WIP runtime-controllable concurrency for replication

Changes done so far:
- signal to route concurrency request up to the stepQueue
    - pretty hacky, no status reporting yet
- stepQueue upsizing (confirmed that it works, no intermediary commit)

Stuck at: stepQueue downsizing
- idea was to have the stepQueue signal to the activated step that it
  should suspend
- ideally, we'd just kill everything associated with the step and track
  it as restartable
    - the driver model doesn't allow for that though within an attempt
    - would need to start a separate run for the step
- less perfect: tell the downsized steps to stop copying, but leave
  all zfs sends + rpc conns open
    - - doesn't give back the resoures that a step aquired before
      being selected as downsize victim (open zfs processe + TCP conn,
      some memory in the pipe)
    - - looks weird to user if the ps aux
    - + re-waking a step is easy: just tell it to proceed with copying
    - (the impl would likely pass a check function down into Step.do
      and have it check that functino periodically. the suspend should
      be acknowledged, and stepQueue should only remove the step from
      the active queue _after_ that step has acknowledged that is
      suspended)

.circleci/config.yml

@@ -7,7 +7,9 @@ workflows:
       - build-1.12
       - build-1.13
       - build-latest
+      - test-build-in-docker
 jobs:
+
   # build-latest serves as the template
   # we use YAML anchors & aliases to exchange the docker image (and hence Go version used for the build)
   build-latest: &build-latest
@@ -108,3 +110,30 @@ jobs:
     <<: *build-latest
     docker:
     - image: circleci/golang:1.13
+
+  # this job tries to mimic the build-in-docker instructions
+  # given in docs/installation.rst
+  #
+  # However, CircleCI doesn't support volume mounts, so we have to copy
+  # the source into the build-container by modifying the Dockerfile
+  test-build-in-docker:
+    description: Check that build-in-docker works
+    docker:
+      - image: circleci/golang:latest
+    environment:
+    working_directory: /go/src/github.com/zrepl/zrepl
+    steps:
+    - checkout
+    - setup_remote_docker
+    - run:
+        name: (hacky) circleci doesn't allow volume mounts, so copy src to container
+        command: echo "ADD . /src" >> build.Dockerfile
+    - run:
+        name: (hacky) commit modified Dockerfile to avoid failing git clean check in Makefile
+        command: git -c user.name='circleci' -c user.email='circleci@localhost' commit -m 'CIRCLECI modified Dockerfile with zrepl src' --author 'autoauthor <circleci@localhost>' -- build.Dockerfile
+    - run:
+        name: build the build image (build deps)
+        command: docker build -t zrepl_build -f build.Dockerfile .
+    - run:
+        name: try compiling
+        command: docker run -it zrepl_build make release

Makefile

@@ -17,6 +17,7 @@ endif
 GO := go
 GOOS ?= $(shell bash -c 'source <($(GO) env) && echo "$$GOOS"')
 GOARCH ?= $(shell bash -c 'source <($(GO) env) && echo "$$GOARCH"')
+GOARM ?= $(shell bash -c 'source <($(GO) env) && echo "$$GOARM"')
 GOHOSTOS ?= $(shell bash -c 'source <($(GO) env) && echo "$$GOHOSTOS"')
 GOHOSTARCH ?= $(shell bash -c 'source <($(GO) env) && echo "$$GOHOSTARCH"')
 GO_ENV_VARS := GO111MODULE=on
@@ -25,11 +26,17 @@ GO_MOD_READONLY := -mod=readonly
 GO_BUILDFLAGS := $(GO_MOD_READONLY)
 GO_BUILD := $(GO_ENV_VARS) $(GO) build $(GO_BUILDFLAGS) -ldflags $(GO_LDFLAGS)
 GOLANGCI_LINT := golangci-lint
+ifneq ($(GOARM),)
+	ZREPL_TARGET_TUPLE := $(GOOS)-$(GOARCH)v$(GOARM)
+else
+	ZREPL_TARGET_TUPLE := $(GOOS)-$(GOARCH)
+endif
 
 .PHONY: printvars
 printvars:
 	@echo GOOS=$(GOOS)
 	@echo GOARCH=$(GOARCH)
+	@echo GOARM=$(GOARM)
 
 
 ##################### PRODUCING A RELEASE #############
@@ -99,6 +106,7 @@ bins-all:
 	$(MAKE) $(BINS_ALL_TARGETS) GOOS=freebsd   GOARCH=386
 	$(MAKE) $(BINS_ALL_TARGETS) GOOS=linux     GOARCH=amd64
 	$(MAKE) $(BINS_ALL_TARGETS) GOOS=linux     GOARCH=arm64
+	$(MAKE) $(BINS_ALL_TARGETS) GOOS=linux     GOARCH=arm     GOARM=7
 	$(MAKE) $(BINS_ALL_TARGETS) GOOS=linux     GOARCH=386
 	$(MAKE) $(BINS_ALL_TARGETS) GOOS=darwin    GOARCH=amd64
 	$(MAKE) $(BINS_ALL_TARGETS) GOOS=solaris   GOARCH=amd64
@@ -118,10 +126,10 @@ vet:
 	$(GO_ENV_VARS) $(GO) vet $(GO_BUILDFLAGS) ./...
 
 zrepl-bin:
-	$(GO_BUILD) -o "$(ARTIFACTDIR)/zrepl-$(GOOS)-$(GOARCH)"
+	$(GO_BUILD) -o "$(ARTIFACTDIR)/zrepl-$(ZREPL_TARGET_TUPLE)"
 
 platformtest-bin:
-		$(GO_BUILD) -o "$(ARTIFACTDIR)/platformtest-$(GOOS)-$(GOARCH)" ./platformtest/harness
+	$(GO_BUILD) -o "$(ARTIFACTDIR)/platformtest-$(ZREPL_TARGET_TUPLE)" ./platformtest/harness
 
 ##################### DEV TARGETS #####################
 # not part of the build, must do that manually
@@ -136,8 +144,19 @@ format:
 
 ZREPL_PLATFORMTEST_POOLNAME := zreplplatformtest
 ZREPL_PLATFORMTEST_IMAGEPATH := /tmp/zreplplatformtest.pool.img
+ZREPL_PLATFORMTEST_MOUNTPOINT := /tmp/zreplplatformtest.pool
+ZREPL_PLATFORMTEST_ZFS_LOG := /tmp/zreplplatformtest.zfs.log
+# ZREPL_PLATFORMTEST_STOP_AND_KEEP := -failure.stop-and-keep-pool
+ZREPL_PLATFORMTEST_ARGS := 
 platformtest: # do not track dependency on platformtest-bin to allow build of platformtest outside of test VM
-	"$(ARTIFACTDIR)/platformtest-$(GOOS)-$(GOARCH)" -poolname "$(ZREPL_PLATFORMTEST_POOLNAME)" -imagepath "$(ZREPL_PLATFORMTEST_IMAGEPATH)"
+	rm -f "$(ZREPL_PLATFORMTEST_ZFS_LOG)"
+	platformtest/logmockzfs/logzfsenv "$(ZREPL_PLATFORMTEST_ZFS_LOG)" `which zfs` \
+	"$(ARTIFACTDIR)/platformtest-$(ZREPL_TARGET_TUPLE)" \
+		-poolname "$(ZREPL_PLATFORMTEST_POOLNAME)" \
+		-imagepath "$(ZREPL_PLATFORMTEST_IMAGEPATH)" \
+		-mountpoint "$(ZREPL_PLATFORMTEST_MOUNTPOINT)" \
+		$(ZREPL_PLATFORMTEST_STOP_AND_KEEP) \
+		$(ZREPL_PLATFORMTEST_ARGS)
 
 ##################### NOARCH #####################
 .PHONY: noarch $(ARTIFACTDIR)/bash_completion $(ARTIFACTDIR)/go_env.txt docs docs-clean

build.Dockerfile

@@ -2,7 +2,8 @@ FROM golang:latest
 
 RUN apt-get update && apt-get install -y \
     python3-pip \
-    unzip
+    unzip \
+    gawk
 
 ADD build.installprotoc.bash ./
 RUN bash build.installprotoc.bash
@@ -22,7 +23,7 @@ RUN mkdir -p /.cache && chmod -R 0777 /.cache
 WORKDIR /src
 
 # Install build tools (e.g. protobuf generator, stringer) into $GOPATH/bin
-ADD go.mod go.sum ./
+ADD build/ /tmp/build
 RUN /tmp/lazy.sh godep
 
 RUN chmod -R 0777 /go

build/tools.go

@@ -3,9 +3,9 @@
 package main
 
 import (
-	_ "golang.org/x/tools/cmd/stringer"
-	_ "github.com/golang/protobuf/protoc-gen-go"
 	_ "github.com/alvaroloes/enumer"
-	_ "golang.org/x/tools/cmd/goimports"
+	_ "github.com/golang/protobuf/protoc-gen-go"
 	_ "github.com/golangci/golangci-lint/cmd/golangci-lint"
+	_ "golang.org/x/tools/cmd/goimports"
+	_ "golang.org/x/tools/cmd/stringer"
 )

client/holds.go

@@ -0,0 +1,87 @@
+package client
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/pkg/errors"
+
+	"github.com/zrepl/zrepl/cli"
+	"github.com/zrepl/zrepl/daemon/filters"
+	"github.com/zrepl/zrepl/endpoint"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+var (
+	HoldsCmd = &cli.Subcommand{
+		Use:   "holds",
+		Short: "manage holds & step bookmarks",
+		SetupSubcommands: func() []*cli.Subcommand {
+			return holdsList
+		},
+	}
+)
+
+var holdsList = []*cli.Subcommand{
+	&cli.Subcommand{
+		Use:             "list [FSFILTER]",
+		Run:             doHoldsList,
+		NoRequireConfig: true,
+		Short: `
+FSFILTER SYNTAX:
+representation of a 'filesystems' filter statement on the command line
+		`,
+	},
+}
+
+func fsfilterFromCliArg(arg string) (zfs.DatasetFilter, error) {
+	mappings := strings.Split(arg, ",")
+	f := filters.NewDatasetMapFilter(len(mappings), true)
+	for _, m := range mappings {
+		thisMappingErr := fmt.Errorf("expecting comma-separated list of <dataset-pattern>:<ok|!> pairs, got %q", m)
+		lhsrhs := strings.SplitN(m, ":", 2)
+		if len(lhsrhs) != 2 {
+			return nil, thisMappingErr
+		}
+		err := f.Add(lhsrhs[0], lhsrhs[1])
+		if err != nil {
+			return nil, fmt.Errorf("%s: %s", thisMappingErr, err)
+		}
+	}
+	return f.AsFilter(), nil
+}
+
+func doHoldsList(sc *cli.Subcommand, args []string) error {
+	var err error
+	ctx := context.Background()
+
+	if len(args) > 1 {
+		return errors.New("this subcommand takes at most one argument")
+	}
+
+	var filter zfs.DatasetFilter
+	if len(args) == 0 {
+		filter = zfs.NoFilter()
+	} else {
+		filter, err = fsfilterFromCliArg(args[0])
+		if err != nil {
+			return errors.Wrap(err, "cannot parse filesystem filter args")
+		}
+	}
+
+	listing, err := endpoint.ListZFSHoldsAndBookmarks(ctx, filter)
+	if err != nil {
+		return err // context clear by invocation of command
+	}
+
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("  ", "  ")
+	if err := enc.Encode(listing); err != nil {
+		panic(err)
+	}
+
+	return nil
+}

client/migrate.go

@@ -4,9 +4,13 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/fatih/color"
+	"github.com/kr/pretty"
 	"github.com/pkg/errors"
 	"github.com/spf13/pflag"
 
+	"github.com/zrepl/zrepl/daemon/job"
+	"github.com/zrepl/zrepl/endpoint"
 	"github.com/zrepl/zrepl/zfs"
 
 	"github.com/zrepl/zrepl/cli"
@@ -31,6 +35,13 @@ var migrations = []*cli.Subcommand{
 			f.BoolVar(&migratePlaceholder0_1Args.dryRun, "dry-run", false, "dry run")
 		},
 	},
+	&cli.Subcommand{
+		Use: "replication-cursor:v1-v2",
+		Run: doMigrateReplicationCursor,
+		SetupFlags: func(f *pflag.FlagSet) {
+			f.BoolVar(&migrateReplicationCursorArgs.dryRun, "dry-run", false, "dry run")
+		},
+	},
 }
 
 var migratePlaceholder0_1Args struct {
@@ -102,3 +113,161 @@ func doMigratePlaceholder0_1(sc *cli.Subcommand, args []string) error {
 
 	return nil
 }
+
+var migrateReplicationCursorArgs struct {
+	dryRun bool
+}
+
+var bold = color.New(color.Bold)
+var succ = color.New(color.FgGreen)
+var fail = color.New(color.FgRed)
+
+var migrateReplicationCursorSkipSentinel = fmt.Errorf("skipping this filesystem")
+
+func doMigrateReplicationCursor(sc *cli.Subcommand, args []string) error {
+	if len(args) != 0 {
+		return fmt.Errorf("migration does not take arguments, got %v", args)
+	}
+
+	cfg := sc.Config()
+	jobs, err := job.JobsFromConfig(cfg)
+	if err != nil {
+		fmt.Printf("cannot parse config:\n%s\n\n", err)
+		fmt.Printf("NOTE: this migration was released together with a change in job name requirements.\n")
+		return fmt.Errorf("exiting migration after error")
+	}
+
+	ctx := context.Background()
+
+	v1cursorJobs := make([]job.Job, 0, len(cfg.Jobs))
+	for i, j := range cfg.Jobs {
+		if jobs[i].Name() != j.Name() {
+			panic("implementation error")
+		}
+		switch j.Ret.(type) {
+		case *config.PushJob:
+			v1cursorJobs = append(v1cursorJobs, jobs[i])
+		case *config.SourceJob:
+			v1cursorJobs = append(v1cursorJobs, jobs[i])
+		default:
+			fmt.Printf("ignoring job %q (%d/%d, type %T), not supposed to create v1 replication cursors\n", j.Name(), i, len(cfg.Jobs), j.Ret)
+			continue
+		}
+	}
+
+	// scan all filesystems for v1 replication cursors
+
+	fss, err := zfs.ZFSListMapping(ctx, zfs.NoFilter())
+	if err != nil {
+		return errors.Wrap(err, "list filesystems")
+	}
+
+	var hadError bool
+	for _, fs := range fss {
+
+		bold.Printf("INSPECT FILESYTEM %q\n", fs.ToString())
+
+		err := doMigrateReplicationCursorFS(ctx, v1cursorJobs, fs)
+		if err == migrateReplicationCursorSkipSentinel {
+			bold.Printf("FILESYSTEM SKIPPED\n")
+		} else if err != nil {
+			hadError = true
+			fail.Printf("MIGRATION FAILED: %s\n", err)
+		} else {
+			succ.Printf("FILESYSTEM %q COMPLETE\n", fs.ToString())
+		}
+	}
+
+	if hadError {
+		fail.Printf("\n\none or more filesystems could not be migrated, please inspect output and or re-run migration")
+		return errors.Errorf("")
+	}
+	return nil
+}
+
+func doMigrateReplicationCursorFS(ctx context.Context, v1CursorJobs []job.Job, fs *zfs.DatasetPath) error {
+
+	var owningJob job.Job = nil
+	for _, job := range v1CursorJobs {
+		conf := job.SenderConfig()
+		if conf == nil {
+			continue
+		}
+		pass, err := conf.FSF.Filter(fs)
+		if err != nil {
+			return errors.Wrapf(err, "filesystem filter error in job %q for fs %q", job.Name(), fs.ToString())
+		}
+		if !pass {
+			continue
+		}
+		if owningJob != nil {
+			return errors.Errorf("jobs %q and %q both match %q\ncannot attribute replication cursor to either one", owningJob.Name(), job.Name(), fs)
+		}
+		owningJob = job
+	}
+	if owningJob == nil {
+		fmt.Printf("no job's Filesystems filter matches\n")
+		return migrateReplicationCursorSkipSentinel
+	}
+	fmt.Printf("identified owning job %q\n", owningJob.Name())
+
+	versions, err := zfs.ZFSListFilesystemVersions(fs, nil)
+	if err != nil {
+		return errors.Wrapf(err, "list filesystem versions of %q", fs.ToString())
+	}
+
+	var oldCursor *zfs.FilesystemVersion
+	for i, fsv := range versions {
+		if fsv.Type != zfs.Bookmark {
+			continue
+		}
+
+		_, _, err := endpoint.ParseReplicationCursorBookmarkName(fsv.ToAbsPath(fs))
+		if err != endpoint.ErrV1ReplicationCursor {
+			continue
+		}
+
+		if oldCursor != nil {
+			fmt.Printf("unexpected v1 replication cursor candidate: %q", fsv.ToAbsPath(fs))
+			return errors.Wrap(err, "multiple filesystem versions identified as v1 replication cursors")
+		}
+
+		oldCursor = &versions[i]
+
+	}
+
+	if oldCursor == nil {
+		bold.Printf("no v1 replication cursor found for filesystem %q\n", fs.ToString())
+		return migrateReplicationCursorSkipSentinel
+	}
+
+	fmt.Printf("found v1 replication cursor:\n%s\n", pretty.Sprint(oldCursor))
+
+	mostRecentNew, err := endpoint.GetMostRecentReplicationCursorOfJob(ctx, fs.ToString(), owningJob.SenderConfig().JobID)
+	if err != nil {
+		return errors.Wrapf(err, "get most recent v2 replication cursor")
+	}
+
+	if mostRecentNew == nil {
+		return errors.Errorf("no v2 replication cursor found for job %q on filesystem %q", owningJob.SenderConfig().JobID, fs.ToString())
+	}
+
+	fmt.Printf("most recent v2 replication cursor:\n%#v", oldCursor)
+
+	if !(mostRecentNew.CreateTXG >= oldCursor.CreateTXG) {
+		return errors.Errorf("v1 replication cursor createtxg is higher than v2 cursor's, skipping this filesystem")
+	}
+
+	fmt.Printf("determined that v2 cursor is bookmark of same or newer version than v1 cursor\n")
+	fmt.Printf("destroying v1 cursor %q\n", oldCursor.ToAbsPath(fs))
+
+	if migrateReplicationCursorArgs.dryRun {
+		succ.Printf("DRY RUN\n")
+	} else {
+		if err := zfs.ZFSDestroyFilesystemVersion(fs, oldCursor); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

client/signal.go

@@ -9,7 +9,7 @@ import (
 )
 
 var SignalCmd = &cli.Subcommand{
-	Use:   "signal [wakeup|reset] JOB",
+	Use:   "signal [wakeup|reset] JOB [DATA]",
 	Short: "wake up a job from wait state or abort its current invocation",
 	Run: func(subcommand *cli.Subcommand, args []string) error {
 		return runSignalCmd(subcommand.Config(), args)
@@ -17,8 +17,13 @@ var SignalCmd = &cli.Subcommand{
 }
 
 func runSignalCmd(config *config.Config, args []string) error {
-	if len(args) != 2 {
-		return errors.Errorf("Expected 2 arguments: [wakeup|reset] JOB")
+	if len(args) < 2 || len(args) > 3 {
+		return errors.Errorf("Expected 2 arguments: [wakeup|reset|set-concurrency] JOB [DATA]")
+	}
+
+	var data string
+	if len(args) == 3 {
+		data = args[2]
 	}
 
 	httpc, err := controlHttpClient(config.Global.Control.SockPath)
@@ -30,9 +35,11 @@ func runSignalCmd(config *config.Config, args []string) error {
 		struct {
 			Name string
 			Op   string
+			Data string
 		}{
 			Name: args[1],
 			Op:   args[0],
+			Data: data,
 		},
 		struct{}{},
 	)

client/status.go

@@ -461,12 +461,23 @@ func (t *tui) renderReplicationReport(rep *report.Report, history *bytesProgress
 	if latest.State != report.AttemptPlanning && latest.State != report.AttemptPlanningError {
 		// Draw global progress bar
 		// Progress: [---------------]
-		expected, replicated := latest.BytesSum()
+		expected, replicated, containsInvalidSizeEstimates := latest.BytesSum()
 		rate, changeCount := history.Update(replicated)
+		eta := time.Duration(0)
+		if rate > 0 {
+			eta = time.Duration((expected-replicated)/rate) * time.Second
+		}
 		t.write("Progress: ")
 		t.drawBar(50, replicated, expected, changeCount)
 		t.write(fmt.Sprintf(" %s / %s @ %s/s", ByteCountBinary(replicated), ByteCountBinary(expected), ByteCountBinary(rate)))
+		if eta != 0 {
+			t.write(fmt.Sprintf(" (%s remaining)", humanizeDuration(eta)))
+		}
 		t.newline()
+		if containsInvalidSizeEstimates {
+			t.write("NOTE: not all steps could be size-estimated, total estimate is likely imprecise!")
+			t.newline()
+		}
 
 		var maxFSLen int
 		for _, fs := range latest.Filesystems {
@@ -707,11 +718,20 @@ func (t *tui) drawBar(length int, bytes, totalBytes int64, changeCount int) {
 
 func (t *tui) printFilesystemStatus(rep *report.FilesystemReport, active bool, maxFS int) {
 
-	expected, replicated := rep.BytesSum()
-	status := fmt.Sprintf("%s (step %d/%d, %s/%s)",
+	expected, replicated, containsInvalidSizeEstimates := rep.BytesSum()
+	sizeEstimationImpreciseNotice := ""
+	if containsInvalidSizeEstimates {
+		sizeEstimationImpreciseNotice = " (some steps lack size estimation)"
+	}
+	if rep.CurrentStep < len(rep.Steps) && rep.Steps[rep.CurrentStep].Info.BytesExpected == 0 {
+		sizeEstimationImpreciseNotice = " (step lacks size estimation)"
+	}
+
+	status := fmt.Sprintf("%s (step %d/%d, %s/%s)%s",
 		strings.ToUpper(string(rep.State)),
 		rep.CurrentStep, len(rep.Steps),
 		ByteCountBinary(replicated), ByteCountBinary(expected),
+		sizeEstimationImpreciseNotice,
 	)
 
 	activeIndicator := " "
@@ -731,8 +751,17 @@ func (t *tui) printFilesystemStatus(rep *report.FilesystemReport, active bool, m
 			if nextStep.IsIncremental() {
 				next = fmt.Sprintf("next: %s => %s", nextStep.Info.From, nextStep.Info.To)
 			} else {
-				next = fmt.Sprintf("next: %s (full)", nextStep.Info.To)
+				next = fmt.Sprintf("next: full send %s", nextStep.Info.To)
 			}
+			attribs := []string{}
+
+			if nextStep.Info.Resumed {
+				attribs = append(attribs, "resumed")
+			}
+
+			attribs = append(attribs, fmt.Sprintf("encrypted=%s", nextStep.Info.Encrypted))
+
+			next += fmt.Sprintf(" (%s)", strings.Join(attribs, ", "))
 		} else {
 			next = "" // individual FSes may still be in planning state
 		}
@@ -755,3 +784,27 @@ func ByteCountBinary(b int64) string {
 	}
 	return fmt.Sprintf("%.1f %ciB", float64(b)/float64(div), "KMGTPE"[exp])
 }
+
+func humanizeDuration(duration time.Duration) string {
+	days := int64(duration.Hours() / 24)
+	hours := int64(math.Mod(duration.Hours(), 24))
+	minutes := int64(math.Mod(duration.Minutes(), 60))
+	seconds := int64(math.Mod(duration.Seconds(), 60))
+
+	var parts []string
+
+	force := false
+	chunks := []int64{days, hours, minutes, seconds}
+	for i, chunk := range chunks {
+		if force || chunk > 0 {
+			padding := 0
+			if force {
+				padding = 2
+			}
+			parts = append(parts, fmt.Sprintf("%*d%c", padding, chunk, "dhms"[i]))
+			force = true
+		}
+	}
+
+	return strings.Join(parts, " ")
+}

client/testcmd.go

@@ -1,7 +1,10 @@
 package client
 
 import (
+	"context"
+	"encoding/json"
 	"fmt"
+	"os"
 
 	"github.com/pkg/errors"
 	"github.com/spf13/pflag"
@@ -15,7 +18,7 @@ import (
 var TestCmd = &cli.Subcommand{
 	Use: "test",
 	SetupSubcommands: func() []*cli.Subcommand {
-		return []*cli.Subcommand{testFilter, testPlaceholder}
+		return []*cli.Subcommand{testFilter, testPlaceholder, testDecodeResumeToken}
 	},
 }
 
@@ -176,3 +179,32 @@ func runTestPlaceholder(subcommand *cli.Subcommand, args []string) error {
 	}
 	return nil
 }
+
+var testDecodeResumeTokenArgs struct {
+	token string
+}
+
+var testDecodeResumeToken = &cli.Subcommand{
+	Use:   "decoderesumetoken --token TOKEN",
+	Short: "decode resume token",
+	SetupFlags: func(f *pflag.FlagSet) {
+		f.StringVar(&testDecodeResumeTokenArgs.token, "token", "", "the resume token obtained from the receive_resume_token property")
+	},
+	Run: runTestDecodeResumeTokenCmd,
+}
+
+func runTestDecodeResumeTokenCmd(subcommand *cli.Subcommand, args []string) error {
+	if testDecodeResumeTokenArgs.token == "" {
+		return fmt.Errorf("token argument must be specified")
+	}
+	token, err := zfs.ParseResumeToken(context.Background(), testDecodeResumeTokenArgs.token)
+	if err != nil {
+		return err
+	}
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("", " ")
+	if err := enc.Encode(&token); err != nil {
+		panic(err)
+	}
+	return nil
+}

config/config.go

@@ -75,16 +75,42 @@ type SnapJob struct {
 	Filesystems  FilesystemsFilter `yaml:"filesystems"`
 }
 
+type SendOptions struct {
+	Encrypted bool `yaml:"encrypted"`
+}
+
+var _ yaml.Defaulter = (*SendOptions)(nil)
+
+func (l *SendOptions) SetDefault() {
+	*l = SendOptions{Encrypted: false}
+}
+
+type RecvOptions struct {
+	// Note: we cannot enforce encrypted recv as the ZFS cli doesn't provide a mechanism for it
+	// Encrypted bool `yaml:"may_encrypted"`
+
+	// Future:
+	// Reencrypt bool `yaml:"reencrypt"`
+}
+
+var _ yaml.Defaulter = (*RecvOptions)(nil)
+
+func (l *RecvOptions) SetDefault() {
+	*l = RecvOptions{}
+}
+
 type PushJob struct {
 	ActiveJob    `yaml:",inline"`
 	Snapshotting SnapshottingEnum  `yaml:"snapshotting"`
 	Filesystems  FilesystemsFilter `yaml:"filesystems"`
+	Send         *SendOptions      `yaml:"send,fromdefaults,optional"`
 }
 
 type PullJob struct {
 	ActiveJob `yaml:",inline"`
 	RootFS    string                   `yaml:"root_fs"`
 	Interval  PositiveDurationOrManual `yaml:"interval"`
+	Recv      *RecvOptions             `yaml:"recv,fromdefaults,optional"`
 }
 
 type PositiveDurationOrManual struct {
@@ -120,13 +146,15 @@ func (i *PositiveDurationOrManual) UnmarshalYAML(u func(interface{}, bool) error
 
 type SinkJob struct {
 	PassiveJob `yaml:",inline"`
-	RootFS     string `yaml:"root_fs"`
+	RootFS     string       `yaml:"root_fs"`
+	Recv       *RecvOptions `yaml:"recv,optional,fromdefaults"`
 }
 
 type SourceJob struct {
 	PassiveJob   `yaml:",inline"`
 	Snapshotting SnapshottingEnum  `yaml:"snapshotting"`
 	Filesystems  FilesystemsFilter `yaml:"filesystems"`
+	Send         *SendOptions      `yaml:"send,optional,fromdefaults"`
 }
 
 type FilesystemsFilter map[string]bool
@@ -245,14 +273,16 @@ type ServeCommon struct {
 }
 
 type TCPServe struct {
-	ServeCommon `yaml:",inline"`
-	Listen      string            `yaml:"listen,hostport"`
-	Clients     map[string]string `yaml:"clients"`
+	ServeCommon    `yaml:",inline"`
+	Listen         string            `yaml:"listen,hostport"`
+	ListenFreeBind bool              `yaml:"listen_freebind,default=false"`
+	Clients        map[string]string `yaml:"clients"`
 }
 
 type TLSServe struct {
 	ServeCommon      `yaml:",inline"`
 	Listen           string        `yaml:"listen,hostport"`
+	ListenFreeBind   bool          `yaml:"listen_freebind,default=false"`
 	Ca               string        `yaml:"ca"`
 	Cert             string        `yaml:"cert"`
 	Key              string        `yaml:"key"`
@@ -331,8 +361,9 @@ type MonitoringEnum struct {
 }
 
 type PrometheusMonitoring struct {
-	Type   string `yaml:"type"`
-	Listen string `yaml:"listen,hostport"`
+	Type           string `yaml:"type"`
+	Listen         string `yaml:"listen,hostport"`
+	ListenFreeBind bool   `yaml:"listen_freebind,default=false"`
 }
 
 type SyslogFacility syslog.Priority

config/config_jobid_test.go

@@ -0,0 +1 @@
+package config

config/config_send_test.go

@@ -0,0 +1,74 @@
+package config
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSendOptions(t *testing.T) {
+	tmpl := `
+jobs:
+- name: foo
+  type: push
+  connect:
+    type: local
+    listener_name: foo
+    client_identity: bar
+  filesystems: {"<": true}
+  %s
+  snapshotting:
+    type: manual
+  pruning:
+    keep_sender:
+    - type: last_n
+      count: 10
+    keep_receiver:
+    - type: last_n
+      count: 10
+`
+	encrypted_false := `
+  send:
+    encrypted: false
+`
+
+	encrypted_true := `
+  send:
+    encrypted: true
+`
+
+	encrypted_unspecified := `
+  send: {}
+`
+
+	send_not_specified := `
+`
+
+	fill := func(s string) string { return fmt.Sprintf(tmpl, s) }
+	var c *Config
+
+	t.Run("encrypted_false", func(t *testing.T) {
+		c = testValidConfig(t, fill(encrypted_false))
+		encrypted := c.Jobs[0].Ret.(*PushJob).Send.Encrypted
+		assert.Equal(t, false, encrypted)
+	})
+	t.Run("encrypted_true", func(t *testing.T) {
+		c = testValidConfig(t, fill(encrypted_true))
+		encrypted := c.Jobs[0].Ret.(*PushJob).Send.Encrypted
+		assert.Equal(t, true, encrypted)
+	})
+
+	t.Run("encrypted_unspecified", func(t *testing.T) {
+		c, err := testConfig(t, fill(encrypted_unspecified))
+		assert.Error(t, err)
+		assert.Nil(t, c)
+	})
+
+	t.Run("send_not_specified", func(t *testing.T) {
+		c, err := testConfig(t, fill(send_not_specified))
+		assert.NoError(t, err)
+		assert.NotNil(t, c)
+	})
+
+}

config/samples/push.yml

@@ -10,6 +10,8 @@ jobs:
       address: "backup-server.foo.bar:8888"
     snapshotting:
       type: manual
+    send:
+      encrypted: false
     pruning:
       keep_sender:
         - type: not_replicated

daemon/control.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"net"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/pkg/errors"
@@ -15,6 +16,7 @@ import (
 
 	"github.com/zrepl/zrepl/daemon/job"
 	"github.com/zrepl/zrepl/daemon/nethelpers"
+	"github.com/zrepl/zrepl/endpoint"
 	"github.com/zrepl/zrepl/logger"
 	"github.com/zrepl/zrepl/util/envconst"
 	"github.com/zrepl/zrepl/version"
@@ -44,6 +46,10 @@ func (j *controlJob) Status() *job.Status { return &job.Status{Type: job.TypeInt
 
 func (j *controlJob) OwnedDatasetSubtreeRoot() (p *zfs.DatasetPath, ok bool) { return nil, false }
 
+func (j *controlJob) SenderConfig() *endpoint.SenderConfig { return nil }
+
+func (j *controlJob) SetConcurrency(concurrency int) error { return errors.Errorf("not supported") }
+
 var promControl struct {
 	requestBegin    *prometheus.CounterVec
 	requestFinished *prometheus.HistogramVec
@@ -123,6 +129,7 @@ func (j *controlJob) Run(ctx context.Context) {
 			type reqT struct {
 				Name string
 				Op   string
+				Data string
 			}
 			var req reqT
 			if decoder(&req) != nil {
@@ -135,6 +142,14 @@ func (j *controlJob) Run(ctx context.Context) {
 				err = j.jobs.wakeup(req.Name)
 			case "reset":
 				err = j.jobs.reset(req.Name)
+			case "set-concurrency":
+				var concurrency int
+				concurrency, err = strconv.Atoi(req.Data) // shadow
+				if err != nil {
+					// fallthrough outer
+				} else {
+					err = j.jobs.setConcurrency(req.Name, concurrency)
+				}
 			default:
 				err = fmt.Errorf("operation %q is invalid", req.Op)
 			}

daemon/daemon.go

@@ -76,7 +76,7 @@ func Run(conf *config.Config) error {
 			return errors.Errorf("unknown monitoring job #%d (type %T)", i, v)
 		}
 		if err != nil {
-			return errors.Wrapf(err, "cannot build monitorin gjob #%d", i)
+			return errors.Wrapf(err, "cannot build monitoring job #%d", i)
 		}
 		jobs.start(ctx, job, true)
 	}
@@ -176,6 +176,18 @@ func (s *jobs) reset(job string) error {
 	return wu()
 }
 
+func (s *jobs) setConcurrency(jobName string, concurrency int) error {
+	s.m.RLock()
+	defer s.m.RUnlock()
+
+	job, ok := s.jobs[jobName]
+	if !ok {
+		return errors.Errorf("Job %q does not exist", job)
+	}
+
+	return job.SetConcurrency(concurrency)
+}
+
 const (
 	jobNamePrometheus = "_prometheus"
 	jobNameControl    = "_control"

daemon/filters/fsmapfilter_test.go

@@ -1,11 +1,11 @@
 package filters
 
 import (
+	"testing"
+
 	"github.com/zrepl/zrepl/zfs"
 )
 
-import "testing"
-
 func TestDatasetMapFilter(t *testing.T) {
 
 	type testCase struct {

daemon/job/active.go

@@ -2,6 +2,7 @@ package job
 
 import (
 	"context"
+	"fmt"
 	"sync"
 	"time"
 
@@ -28,7 +29,7 @@ import (
 
 type ActiveSide struct {
 	mode      activeMode
-	name      string
+	name      endpoint.JobID
 	connecter transport.Connecter
 
 	prunerFactory *pruner.PrunerFactory
@@ -54,9 +55,12 @@ const (
 type activeSideTasks struct {
 	state ActiveSideState
 
+	concurrency int
+
 	// valid for state ActiveSideReplicating, ActiveSidePruneSender, ActiveSidePruneReceiver, ActiveSideDone
-	replicationReport driver.ReportFunc
-	replicationCancel context.CancelFunc
+	replicationReport         driver.ReportFunc
+	replicationCancel         context.CancelFunc
+	replicationSetConcurrency driver.SetConcurrencyFunc
 
 	// valid for state ActiveSidePruneSender, ActiveSidePruneReceiver, ActiveSideDone
 	prunerSender, prunerReceiver *pruner.Pruner
@@ -82,17 +86,19 @@ type activeMode interface {
 	DisconnectEndpoints()
 	SenderReceiver() (logic.Sender, logic.Receiver)
 	Type() Type
+	PlannerPolicy() logic.PlannerPolicy
 	RunPeriodic(ctx context.Context, wakeUpCommon chan<- struct{})
 	SnapperReport() *snapper.Report
 	ResetConnectBackoff()
 }
 
 type modePush struct {
-	setupMtx sync.Mutex
-	sender   *endpoint.Sender
-	receiver *rpc.Client
-	fsfilter endpoint.FSFilter
-	snapper  *snapper.PeriodicOrManual
+	setupMtx      sync.Mutex
+	sender        *endpoint.Sender
+	receiver      *rpc.Client
+	senderConfig  *endpoint.SenderConfig
+	plannerPolicy *logic.PlannerPolicy
+	snapper       *snapper.PeriodicOrManual
 }
 
 func (m *modePush) ConnectEndpoints(loggers rpc.Loggers, connecter transport.Connecter) {
@@ -101,7 +107,7 @@ func (m *modePush) ConnectEndpoints(loggers rpc.Loggers, connecter transport.Con
 	if m.receiver != nil || m.sender != nil {
 		panic("inconsistent use of ConnectEndpoints and DisconnectEndpoints")
 	}
-	m.sender = endpoint.NewSender(m.fsfilter)
+	m.sender = endpoint.NewSender(*m.senderConfig)
 	m.receiver = rpc.NewClient(connecter, loggers)
 }
 
@@ -121,6 +127,8 @@ func (m *modePush) SenderReceiver() (logic.Sender, logic.Receiver) {
 
 func (m *modePush) Type() Type { return TypePush }
 
+func (m *modePush) PlannerPolicy() logic.PlannerPolicy { return *m.plannerPolicy }
+
 func (m *modePush) RunPeriodic(ctx context.Context, wakeUpCommon chan<- struct{}) {
 	m.snapper.Run(ctx, wakeUpCommon)
 }
@@ -137,13 +145,22 @@ func (m *modePush) ResetConnectBackoff() {
 	}
 }
 
-func modePushFromConfig(g *config.Global, in *config.PushJob) (*modePush, error) {
+func modePushFromConfig(g *config.Global, in *config.PushJob, jobID endpoint.JobID) (*modePush, error) {
 	m := &modePush{}
+
 	fsf, err := filters.DatasetMapFilterFromConfig(in.Filesystems)
 	if err != nil {
 		return nil, errors.Wrap(err, "cannnot build filesystem filter")
 	}
-	m.fsfilter = fsf
+
+	m.senderConfig = &endpoint.SenderConfig{
+		FSF:     fsf,
+		Encrypt: &zfs.NilBool{B: in.Send.Encrypted},
+		JobID:   jobID,
+	}
+	m.plannerPolicy = &logic.PlannerPolicy{
+		EncryptedSend: logic.TriFromBool(in.Send.Encrypted),
+	}
 
 	if m.snapper, err = snapper.FromConfig(g, fsf, in.Snapshotting); err != nil {
 		return nil, errors.Wrap(err, "cannot build snapper")
@@ -153,11 +170,13 @@ func modePushFromConfig(g *config.Global, in *config.PushJob) (*modePush, error)
 }
 
 type modePull struct {
-	setupMtx sync.Mutex
-	receiver *endpoint.Receiver
-	sender   *rpc.Client
-	rootFS   *zfs.DatasetPath
-	interval config.PositiveDurationOrManual
+	setupMtx       sync.Mutex
+	receiver       *endpoint.Receiver
+	receiverConfig endpoint.ReceiverConfig
+	sender         *rpc.Client
+	rootFS         *zfs.DatasetPath
+	plannerPolicy  *logic.PlannerPolicy
+	interval       config.PositiveDurationOrManual
 }
 
 func (m *modePull) ConnectEndpoints(loggers rpc.Loggers, connecter transport.Connecter) {
@@ -166,7 +185,7 @@ func (m *modePull) ConnectEndpoints(loggers rpc.Loggers, connecter transport.Con
 	if m.receiver != nil || m.sender != nil {
 		panic("inconsistent use of ConnectEndpoints and DisconnectEndpoints")
 	}
-	m.receiver = endpoint.NewReceiver(m.rootFS, false)
+	m.receiver = endpoint.NewReceiver(m.receiverConfig)
 	m.sender = rpc.NewClient(connecter, loggers)
 }
 
@@ -186,6 +205,8 @@ func (m *modePull) SenderReceiver() (logic.Sender, logic.Receiver) {
 
 func (*modePull) Type() Type { return TypePull }
 
+func (m *modePull) PlannerPolicy() logic.PlannerPolicy { return *m.plannerPolicy }
+
 func (m *modePull) RunPeriodic(ctx context.Context, wakeUpCommon chan<- struct{}) {
 	if m.interval.Manual {
 		GetLogger(ctx).Info("manual pull configured, periodic pull disabled")
@@ -223,7 +244,7 @@ func (m *modePull) ResetConnectBackoff() {
 	}
 }
 
-func modePullFromConfig(g *config.Global, in *config.PullJob) (m *modePull, err error) {
+func modePullFromConfig(g *config.Global, in *config.PullJob, jobID endpoint.JobID) (m *modePull, err error) {
 	m = &modePull{}
 	m.interval = in.Interval
 
@@ -235,26 +256,58 @@ func modePullFromConfig(g *config.Global, in *config.PullJob) (m *modePull, err
 		return nil, errors.New("RootFS must not be empty") // duplicates error check of receiver
 	}
 
+	m.plannerPolicy = &logic.PlannerPolicy{
+		EncryptedSend: logic.DontCare,
+	}
+
+	m.receiverConfig = endpoint.ReceiverConfig{
+		JobID:                      jobID,
+		RootWithoutClientComponent: m.rootFS,
+		AppendClientIdentity:       false, // !
+		UpdateLastReceivedHold:     true,
+	}
+	if err := m.receiverConfig.Validate(); err != nil {
+		return nil, errors.Wrap(err, "cannot build receiver config")
+	}
+
 	return m, nil
 }
 
-func activeSide(g *config.Global, in *config.ActiveJob, mode activeMode) (j *ActiveSide, err error) {
+func activeSide(g *config.Global, in *config.ActiveJob, configJob interface{}) (j *ActiveSide, err error) {
+
+	j = &ActiveSide{}
+	j.name, err = endpoint.MakeJobID(in.Name)
+	if err != nil {
+		return nil, errors.Wrap(err, "invalid job name")
+	}
+
+	j.tasks.concurrency = 1 // FIXME
+
+	switch v := configJob.(type) {
+	case *config.PushJob:
+		j.mode, err = modePushFromConfig(g, v, j.name) // shadow
+	case *config.PullJob:
+		j.mode, err = modePullFromConfig(g, v, j.name) // shadow
+	default:
+		panic(fmt.Sprintf("implementation error: unknown job type %T", v))
+	}
+	if err != nil {
+		return nil, err // no wrapping required
+	}
 
-	j = &ActiveSide{mode: mode}
-	j.name = in.Name
 	j.promRepStateSecs = prometheus.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace:   "zrepl",
 		Subsystem:   "replication",
 		Name:        "state_time",
 		Help:        "seconds spent during replication",
-		ConstLabels: prometheus.Labels{"zrepl_job": j.name},
+		ConstLabels: prometheus.Labels{"zrepl_job": j.name.String()},
 	}, []string{"state"})
 	j.promBytesReplicated = prometheus.NewCounterVec(prometheus.CounterOpts{
 		Namespace:   "zrepl",
 		Subsystem:   "replication",
 		Name:        "bytes_replicated",
 		Help:        "number of bytes replicated from sender to receiver per filesystem",
-		ConstLabels: prometheus.Labels{"zrepl_job": j.name},
+		ConstLabels: prometheus.Labels{"zrepl_job": j.name.String()},
 	}, []string{"filesystem"})
 
 	j.connecter, err = fromconfig.ConnecterFromConfig(g, in.Connect)
@@ -267,7 +320,7 @@ func activeSide(g *config.Global, in *config.ActiveJob, mode activeMode) (j *Act
 		Subsystem:   "pruning",
 		Name:        "time",
 		Help:        "seconds spent in pruner",
-		ConstLabels: prometheus.Labels{"zrepl_job": j.name},
+		ConstLabels: prometheus.Labels{"zrepl_job": j.name.String()},
 	}, []string{"prune_side"})
 	j.prunerFactory, err = pruner.NewPrunerFactory(in.Pruning, j.promPruneSecs)
 	if err != nil {
@@ -283,7 +336,7 @@ func (j *ActiveSide) RegisterMetrics(registerer prometheus.Registerer) {
 	registerer.MustRegister(j.promBytesReplicated)
 }
 
-func (j *ActiveSide) Name() string { return j.name }
+func (j *ActiveSide) Name() string { return j.name.String() }
 
 type ActiveSideStatus struct {
 	Replication                    *report.Report
@@ -318,6 +371,31 @@ func (j *ActiveSide) OwnedDatasetSubtreeRoot() (rfs *zfs.DatasetPath, ok bool) {
 	return pull.rootFS.Copy(), true
 }
 
+func (j *ActiveSide) SenderConfig() *endpoint.SenderConfig {
+	push, ok := j.mode.(*modePush)
+	if !ok {
+		_ = j.mode.(*modePull) // make sure we didn't introduce a new job type
+		return nil
+	}
+	return push.senderConfig
+}
+
+func (j *ActiveSide) SetConcurrency(concurrency int) (err error) {
+	j.updateTasks(func(tasks *activeSideTasks) {
+		if tasks.replicationSetConcurrency != nil {
+			err = tasks.replicationSetConcurrency(concurrency) // no shadow
+			if err == nil {
+				tasks.concurrency = concurrency
+			}
+		} else {
+			// FIXME this is not great, should always be able to set it
+			err = errors.Errorf("cannot set while not replicating")
+		}
+
+	})
+	return err
+}
+
 func (j *ActiveSide) Run(ctx context.Context) {
 	log := GetLogger(ctx)
 	ctx = logging.WithSubsystemLoggers(ctx, log)
@@ -379,11 +457,14 @@ func (j *ActiveSide) do(ctx context.Context) {
 		ctx, repCancel := context.WithCancel(ctx)
 		var repWait driver.WaitFunc
 		j.updateTasks(func(tasks *activeSideTasks) {
-			// reset it
-			*tasks = activeSideTasks{}
+			// reset it (almost)
+			old := *tasks
+			*tasks = activeSideTasks{
+				concurrency: old.concurrency,
+			}
 			tasks.replicationCancel = repCancel
-			tasks.replicationReport, repWait = replication.Do(
-				ctx, logic.NewPlanner(j.promRepStateSecs, j.promBytesReplicated, sender, receiver),
+			tasks.replicationReport, repWait, tasks.replicationSetConcurrency = replication.Do(
+				ctx, tasks.concurrency, logic.NewPlanner(j.promRepStateSecs, j.promBytesReplicated, sender, receiver, j.mode.PlannerPolicy()),
 			)
 			tasks.state = ActiveSideReplicating
 		})

daemon/job/build_jobs.go

@@ -48,20 +48,12 @@ func buildJob(c *config.Global, in config.JobEnum) (j Job, err error) {
 	// FIXME prettify this
 	switch v := in.Ret.(type) {
 	case *config.SinkJob:
-		m, err := modeSinkFromConfig(c, v)
-		if err != nil {
-			return cannotBuildJob(err, v.Name)
-		}
-		j, err = passiveSideFromConfig(c, &v.PassiveJob, m)
+		j, err = passiveSideFromConfig(c, &v.PassiveJob, v)
 		if err != nil {
 			return cannotBuildJob(err, v.Name)
 		}
 	case *config.SourceJob:
-		m, err := modeSourceFromConfig(c, v)
-		if err != nil {
-			return cannotBuildJob(err, v.Name)
-		}
-		j, err = passiveSideFromConfig(c, &v.PassiveJob, m)
+		j, err = passiveSideFromConfig(c, &v.PassiveJob, v)
 		if err != nil {
 			return cannotBuildJob(err, v.Name)
 		}
@@ -71,20 +63,12 @@ func buildJob(c *config.Global, in config.JobEnum) (j Job, err error) {
 			return cannotBuildJob(err, v.Name)
 		}
 	case *config.PushJob:
-		m, err := modePushFromConfig(c, v)
-		if err != nil {
-			return cannotBuildJob(err, v.Name)
-		}
-		j, err = activeSide(c, &v.ActiveJob, m)
+		j, err = activeSide(c, &v.ActiveJob, v)
 		if err != nil {
 			return cannotBuildJob(err, v.Name)
 		}
 	case *config.PullJob:
-		m, err := modePullFromConfig(c, v)
-		if err != nil {
-			return cannotBuildJob(err, v.Name)
-		}
-		j, err = activeSide(c, &v.ActiveJob, m)
+		j, err = activeSide(c, &v.ActiveJob, v)
 		if err != nil {
 			return cannotBuildJob(err, v.Name)
 		}
@@ -104,6 +88,11 @@ func validateReceivingSidesDoNotOverlap(receivingRootFSs []string) error {
 	sort.Slice(rfss, func(i, j int) bool {
 		return strings.Compare(rfss[i], rfss[j]) == -1
 	})
+	// add tailing slash because of hierarchy-simulation
+	// rootfs/ is not root of rootfs2/
+	for i := 0; i < len(rfss); i++ {
+		rfss[i] += "/"
+	}
 	// idea:
 	//   no path in rfss must be prefix of another
 	//

daemon/job/build_jobs_test.go

@@ -1,9 +1,13 @@
 package job
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/zrepl/zrepl/config"
 )
 
 func TestValidateReceivingSidesDoNotOverlap(t *testing.T) {
@@ -18,6 +22,7 @@ func TestValidateReceivingSidesDoNotOverlap(t *testing.T) {
 		{false, []string{"a"}},
 		{false, []string{"some/path"}},
 		{false, []string{"zroot/sink1", "zroot/sink2", "zroot/sink3"}},
+		{false, []string{"zroot/foo", "zroot/foobar"}},
 		{true, []string{"zroot/b", "zroot/b"}},
 		{true, []string{"zroot/foo", "zroot/foo/bar", "zroot/baz"}},
 		{false, []string{"a/x", "b/x"}},
@@ -40,3 +45,66 @@ func TestValidateReceivingSidesDoNotOverlap(t *testing.T) {
 		}
 	}
 }
+
+func TestJobIDErrorHandling(t *testing.T) {
+	tmpl := `
+jobs:
+- name: %s
+  type: push
+  connect:
+    type: local
+    listener_name: foo
+    client_identity: bar
+  filesystems: {"<": true}
+  snapshotting:
+    type: manual
+  pruning:
+    keep_sender:
+    - type: last_n
+      count: 10
+    keep_receiver:
+    - type: last_n
+      count: 10
+`
+	fill := func(s string) string { return fmt.Sprintf(tmpl, s) }
+
+	type Case struct {
+		jobName string
+		valid   bool
+	}
+	cases := []Case{
+		{"validjobname", true},
+		{"valid with spaces", true},
+		{"invalid\twith\ttabs", false},
+		{"invalid#withdelimiter", false},
+		{"invalid@withdelimiter", false},
+		{"withnewline\\nmiddle", false},
+		{"withnewline\\n", false},
+		{"withslash/", false},
+		{"withslash/inthemiddle", false},
+		{"/", false},
+	}
+
+	for i := range cases {
+		t.Run(cases[i].jobName, func(t *testing.T) {
+			c := cases[i]
+
+			conf, err := config.ParseConfigBytes([]byte(fill(c.jobName)))
+			require.NoError(t, err, "not expecting yaml-config to know about job ids")
+			require.NotNil(t, conf)
+			jobs, err := JobsFromConfig(conf)
+
+			if c.valid {
+				assert.NoError(t, err)
+				require.Len(t, jobs, 1)
+				assert.Equal(t, c.jobName, jobs[0].Name())
+			} else {
+				t.Logf("error: %s", err)
+				assert.Error(t, err)
+				assert.Nil(t, jobs)
+			}
+
+		})
+	}
+
+}

daemon/job/job.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/prometheus/client_golang/prometheus"
 
+	"github.com/zrepl/zrepl/endpoint"
 	"github.com/zrepl/zrepl/logger"
 	"github.com/zrepl/zrepl/zfs"
 )
@@ -38,6 +39,8 @@ type Job interface {
 	// Jobs that return a subtree of the dataset hierarchy
 	// must return the root of that subtree as rfs and ok = true
 	OwnedDatasetSubtreeRoot() (rfs *zfs.DatasetPath, ok bool)
+	SenderConfig() *endpoint.SenderConfig
+	SetConcurrency(concurrency int) error
 }
 
 type Type string

daemon/job/passive.go

@@ -20,7 +20,7 @@ import (
 
 type PassiveSide struct {
 	mode   passiveMode
-	name   string
+	name   endpoint.JobID
 	listen transport.AuthenticatedListenerFactory
 }
 
@@ -32,43 +32,56 @@ type passiveMode interface {
 }
 
 type modeSink struct {
-	rootDataset *zfs.DatasetPath
+	receiverConfig endpoint.ReceiverConfig
 }
 
 func (m *modeSink) Type() Type { return TypeSink }
 
 func (m *modeSink) Handler() rpc.Handler {
-	return endpoint.NewReceiver(m.rootDataset, true)
+	return endpoint.NewReceiver(m.receiverConfig)
 }
 
 func (m *modeSink) RunPeriodic(_ context.Context)  {}
 func (m *modeSink) SnapperReport() *snapper.Report { return nil }
 
-func modeSinkFromConfig(g *config.Global, in *config.SinkJob) (m *modeSink, err error) {
+func modeSinkFromConfig(g *config.Global, in *config.SinkJob, jobID endpoint.JobID) (m *modeSink, err error) {
 	m = &modeSink{}
-	m.rootDataset, err = zfs.NewDatasetPath(in.RootFS)
+
+	rootDataset, err := zfs.NewDatasetPath(in.RootFS)
 	if err != nil {
 		return nil, errors.New("root dataset is not a valid zfs filesystem path")
 	}
-	if m.rootDataset.Length() <= 0 {
-		return nil, errors.New("root dataset must not be empty") // duplicates error check of receiver
+
+	m.receiverConfig = endpoint.ReceiverConfig{
+		JobID:                      jobID,
+		RootWithoutClientComponent: rootDataset,
+		AppendClientIdentity:       true, // !
+		UpdateLastReceivedHold:     true,
 	}
+	if err := m.receiverConfig.Validate(); err != nil {
+		return nil, errors.Wrap(err, "cannot build receiver config")
+	}
+
 	return m, nil
 }
 
 type modeSource struct {
-	fsfilter zfs.DatasetFilter
-	snapper  *snapper.PeriodicOrManual
+	senderConfig *endpoint.SenderConfig
+	snapper      *snapper.PeriodicOrManual
 }
 
-func modeSourceFromConfig(g *config.Global, in *config.SourceJob) (m *modeSource, err error) {
+func modeSourceFromConfig(g *config.Global, in *config.SourceJob, jobID endpoint.JobID) (m *modeSource, err error) {
 	// FIXME exact dedup of modePush
 	m = &modeSource{}
 	fsf, err := filters.DatasetMapFilterFromConfig(in.Filesystems)
 	if err != nil {
 		return nil, errors.Wrap(err, "cannnot build filesystem filter")
 	}
-	m.fsfilter = fsf
+	m.senderConfig = &endpoint.SenderConfig{
+		FSF:     fsf,
+		Encrypt: &zfs.NilBool{B: in.Send.Encrypted},
+		JobID:   jobID,
+	}
 
 	if m.snapper, err = snapper.FromConfig(g, fsf, in.Snapshotting); err != nil {
 		return nil, errors.Wrap(err, "cannot build snapper")
@@ -80,7 +93,7 @@ func modeSourceFromConfig(g *config.Global, in *config.SourceJob) (m *modeSource
 func (m *modeSource) Type() Type { return TypeSource }
 
 func (m *modeSource) Handler() rpc.Handler {
-	return endpoint.NewSender(m.fsfilter)
+	return endpoint.NewSender(*m.senderConfig)
 }
 
 func (m *modeSource) RunPeriodic(ctx context.Context) {
@@ -91,9 +104,25 @@ func (m *modeSource) SnapperReport() *snapper.Report {
 	return m.snapper.Report()
 }
 
-func passiveSideFromConfig(g *config.Global, in *config.PassiveJob, mode passiveMode) (s *PassiveSide, err error) {
+func passiveSideFromConfig(g *config.Global, in *config.PassiveJob, configJob interface{}) (s *PassiveSide, err error) {
+
+	s = &PassiveSide{}
+
+	s.name, err = endpoint.MakeJobID(in.Name)
+	if err != nil {
+		return nil, errors.Wrap(err, "invalid job name")
+	}
+
+	switch v := configJob.(type) {
+	case *config.SinkJob:
+		s.mode, err = modeSinkFromConfig(g, v, s.name) // shadow
+	case *config.SourceJob:
+		s.mode, err = modeSourceFromConfig(g, v, s.name) // shadow
+	}
+	if err != nil {
+		return nil, err // no wrapping necessary
+	}
 
-	s = &PassiveSide{mode: mode, name: in.Name}
 	if s.listen, err = fromconfig.ListenerFactoryFromConfig(g, in.Serve); err != nil {
 		return nil, errors.Wrap(err, "cannot build listener factory")
 	}
@@ -101,7 +130,7 @@ func passiveSideFromConfig(g *config.Global, in *config.PassiveJob, mode passive
 	return s, nil
 }
 
-func (j *PassiveSide) Name() string { return j.name }
+func (j *PassiveSide) Name() string { return j.name.String() }
 
 type PassiveStatus struct {
 	Snapper *snapper.Report
@@ -120,11 +149,22 @@ func (j *PassiveSide) OwnedDatasetSubtreeRoot() (rfs *zfs.DatasetPath, ok bool)
 		_ = j.mode.(*modeSource) // make sure we didn't introduce a new job type
 		return nil, false
 	}
-	return sink.rootDataset.Copy(), true
+	return sink.receiverConfig.RootWithoutClientComponent.Copy(), true
+}
+
+func (j *PassiveSide) SenderConfig() *endpoint.SenderConfig {
+	source, ok := j.mode.(*modeSource)
+	if !ok {
+		_ = j.mode.(*modeSink) // make sure we didn't introduce a new job type
+		return nil
+	}
+	return source.senderConfig
 }
 
 func (*PassiveSide) RegisterMetrics(registerer prometheus.Registerer) {}
 
+func (*PassiveSide) SetConcurrency(concurrency int) error { return errors.Errorf("not supported") }
+
 func (j *PassiveSide) Run(ctx context.Context) {
 
 	log := GetLogger(ctx)

daemon/job/snapjob.go

@@ -2,7 +2,6 @@ package job
 
 import (
 	"context"
-	"fmt"
 	"sort"
 
 	"github.com/pkg/errors"
@@ -20,7 +19,7 @@ import (
 )
 
 type SnapJob struct {
-	name     string
+	name     endpoint.JobID
 	fsfilter zfs.DatasetFilter
 	snapper  *snapper.PeriodicOrManual
 
@@ -31,7 +30,7 @@ type SnapJob struct {
 	pruner *pruner.Pruner
 }
 
-func (j *SnapJob) Name() string { return j.name }
+func (j *SnapJob) Name() string { return j.name.String() }
 
 func (j *SnapJob) Type() Type { return TypeSnap }
 
@@ -39,20 +38,23 @@ func snapJobFromConfig(g *config.Global, in *config.SnapJob) (j *SnapJob, err er
 	j = &SnapJob{}
 	fsf, err := filters.DatasetMapFilterFromConfig(in.Filesystems)
 	if err != nil {
-		return nil, errors.Wrap(err, "cannnot build filesystem filter")
+		return nil, errors.Wrap(err, "cannot build filesystem filter")
 	}
 	j.fsfilter = fsf
 
 	if j.snapper, err = snapper.FromConfig(g, fsf, in.Snapshotting); err != nil {
 		return nil, errors.Wrap(err, "cannot build snapper")
 	}
-	j.name = in.Name
+	j.name, err = endpoint.MakeJobID(in.Name)
+	if err != nil {
+		return nil, errors.Wrap(err, "invalid job name")
+	}
 	j.promPruneSecs = prometheus.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace:   "zrepl",
 		Subsystem:   "pruning",
 		Name:        "time",
 		Help:        "seconds spent in pruner",
-		ConstLabels: prometheus.Labels{"zrepl_job": j.name},
+		ConstLabels: prometheus.Labels{"zrepl_job": j.name.String()},
 	}, []string{"prune_side"})
 	j.prunerFactory, err = pruner.NewLocalPrunerFactory(in.Pruning, j.promPruneSecs)
 	if err != nil {
@@ -84,6 +86,8 @@ func (j *SnapJob) OwnedDatasetSubtreeRoot() (rfs *zfs.DatasetPath, ok bool) {
 	return nil, false
 }
 
+func (j *SnapJob) SenderConfig() *endpoint.SenderConfig { return nil }
+
 func (j *SnapJob) Run(ctx context.Context) {
 	log := GetLogger(ctx)
 	ctx = logging.WithSubsystemLoggers(ctx, log)
@@ -113,6 +117,8 @@ outer:
 	}
 }
 
+func (*SnapJob) SetConcurrency(concurrency int) error { return errors.Errorf("not supported") }
+
 // Adaptor that implements pruner.History around a pruner.Target.
 // The ReplicationCursor method is Get-op only and always returns
 // the filesystem's most recent version's GUID.
@@ -133,9 +139,6 @@ type alwaysUpToDateReplicationCursorHistory struct {
 var _ pruner.History = (*alwaysUpToDateReplicationCursorHistory)(nil)
 
 func (h alwaysUpToDateReplicationCursorHistory) ReplicationCursor(ctx context.Context, req *pdu.ReplicationCursorReq) (*pdu.ReplicationCursorRes, error) {
-	if req.GetGet() == nil {
-		return nil, fmt.Errorf("unsupported ReplicationCursor request: SnapJob only supports GETting a (faked) cursor")
-	}
 	fsvReq := &pdu.ListFilesystemVersionsReq{
 		Filesystem: req.GetFilesystem(),
 	}
@@ -162,7 +165,12 @@ func (h alwaysUpToDateReplicationCursorHistory) ListFilesystems(ctx context.Cont
 func (j *SnapJob) doPrune(ctx context.Context) {
 	log := GetLogger(ctx)
 	ctx = logging.WithSubsystemLoggers(ctx, log)
-	sender := endpoint.NewSender(j.fsfilter)
+	sender := endpoint.NewSender(endpoint.SenderConfig{
+		JobID: j.name,
+		FSF:   j.fsfilter,
+		// FIXME encryption setting is irrelevant for SnapJob because the endpoint is only used as pruner.Target
+		Encrypt: &zfs.NilBool{B: true},
+	})
 	j.pruner = j.prunerFactory.BuildLocalPruner(ctx, sender, alwaysUpToDateReplicationCursorHistory{sender})
 	log.Info("start pruning")
 	j.pruner.Prune()

daemon/prometheus.go

@@ -5,25 +5,29 @@ import (
 	"net"
 	"net/http"
 
+	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 
 	"github.com/zrepl/zrepl/config"
 	"github.com/zrepl/zrepl/daemon/job"
+	"github.com/zrepl/zrepl/endpoint"
 	"github.com/zrepl/zrepl/logger"
 	"github.com/zrepl/zrepl/rpc/dataconn/frameconn"
+	"github.com/zrepl/zrepl/util/tcpsock"
 	"github.com/zrepl/zrepl/zfs"
 )
 
 type prometheusJob struct {
-	listen string
+	listen   string
+	freeBind bool
 }
 
 func newPrometheusJobFromConfig(in *config.PrometheusMonitoring) (*prometheusJob, error) {
 	if _, _, err := net.SplitHostPort(in.Listen); err != nil {
 		return nil, err
 	}
-	return &prometheusJob{in.Listen}, nil
+	return &prometheusJob{in.Listen, in.ListenFreeBind}, nil
 }
 
 var prom struct {
@@ -46,6 +50,10 @@ func (j *prometheusJob) Status() *job.Status { return &job.Status{Type: job.Type
 
 func (j *prometheusJob) OwnedDatasetSubtreeRoot() (p *zfs.DatasetPath, ok bool) { return nil, false }
 
+func (j *prometheusJob) SenderConfig() *endpoint.SenderConfig { return nil }
+
+func (j *prometheusJob) SetConcurrency(concurrency int) error { return errors.Errorf("not supported") }
+
 func (j *prometheusJob) RegisterMetrics(registerer prometheus.Registerer) {}
 
 func (j *prometheusJob) Run(ctx context.Context) {
@@ -60,7 +68,7 @@ func (j *prometheusJob) Run(ctx context.Context) {
 
 	log := job.GetLogger(ctx)
 
-	l, err := net.Listen("tcp", j.listen)
+	l, err := tcpsock.Listen(j.listen, j.freeBind)
 	if err != nil {
 		log.WithError(err).Error("cannot listen")
 		return

daemon/pruner/pruner.go

@@ -412,9 +412,6 @@ tfss_loop:
 
 		rcReq := &pdu.ReplicationCursorReq{
 			Filesystem: tfs.Path,
-			Op: &pdu.ReplicationCursorReq_Get{
-				Get: &pdu.ReplicationCursorReq_GetOp{},
-			},
 		}
 		rc, err := receiver.ReplicationCursor(ctx, rcReq)
 		if err != nil {

daemon/snapper/snapper.go

@@ -13,6 +13,7 @@ import (
 	"github.com/zrepl/zrepl/daemon/filters"
 	"github.com/zrepl/zrepl/daemon/hooks"
 	"github.com/zrepl/zrepl/logger"
+	"github.com/zrepl/zrepl/util/envconst"
 	"github.com/zrepl/zrepl/zfs"
 )
 
@@ -400,9 +401,19 @@ func listFSes(ctx context.Context, mf *filters.DatasetMapFilter) (fss []*zfs.Dat
 	return zfs.ZFSListMapping(ctx, mf)
 }
 
+var syncUpWarnNoSnapshotUntilSyncupMinDuration = envconst.Duration("ZREPL_SNAPPER_SYNCUP_WARN_MIN_DURATION", 1*time.Second)
+
+// see docs/snapshotting.rst
 func findSyncPoint(log Logger, fss []*zfs.DatasetPath, prefix string, interval time.Duration) (syncPoint time.Time, err error) {
+
+	const (
+		prioHasVersions int = iota
+		prioNoVersions
+	)
+
 	type snapTime struct {
 		ds   *zfs.DatasetPath
+		prio int // lower is higher
 		time time.Time
 	}
 
@@ -411,55 +422,89 @@ func findSyncPoint(log Logger, fss []*zfs.DatasetPath, prefix string, interval t
 	}
 
 	snaptimes := make([]snapTime, 0, len(fss))
+	hardErrs := 0
 
 	now := time.Now()
 
-	log.Debug("examine filesystem state")
+	log.Debug("examine filesystem state to find sync point")
 	for _, d := range fss {
-
 		l := log.WithField("fs", d.ToString())
-
-		fsvs, err := zfs.ZFSListFilesystemVersions(d, filters.NewTypedPrefixFilter(prefix, zfs.Snapshot))
-		if err != nil {
-			l.WithError(err).Error("cannot list filesystem versions")
-			continue
-		}
-		if len(fsvs) <= 0 {
-			l.WithField("prefix", prefix).Debug("no filesystem versions with prefix")
-			continue
+		syncPoint, err := findSyncPointFSNextOptimalSnapshotTime(l, now, interval, prefix, d)
+		if err == findSyncPointFSNoFilesystemVersionsErr {
+			snaptimes = append(snaptimes, snapTime{
+				ds:   d,
+				prio: prioNoVersions,
+				time: now,
+			})
+		} else if err != nil {
+			hardErrs++
+			l.WithError(err).Error("cannot determine optimal sync point for this filesystem")
+		} else {
+			l.WithField("syncPoint", syncPoint).Debug("found optimal sync point for this filesystem")
+			snaptimes = append(snaptimes, snapTime{
+				ds:   d,
+				prio: prioHasVersions,
+				time: syncPoint,
+			})
 		}
+	}
 
-		// Sort versions by creation
-		sort.SliceStable(fsvs, func(i, j int) bool {
-			return fsvs[i].CreateTXG < fsvs[j].CreateTXG
-		})
-
-		latest := fsvs[len(fsvs)-1]
-		l.WithField("creation", latest.Creation).
-			Debug("found latest snapshot")
-
-		since := now.Sub(latest.Creation)
-		if since < 0 {
-			l.WithField("snapshot", latest.Name).
-				WithField("creation", latest.Creation).
-				Error("snapshot is from the future")
-			continue
-		}
-		next := now
-		if since < interval {
-			next = latest.Creation.Add(interval)
-		}
-		snaptimes = append(snaptimes, snapTime{d, next})
+	if hardErrs == len(fss) {
+		return time.Time{}, fmt.Errorf("hard errors in determining sync point for every matching filesystem")
 	}
 
 	if len(snaptimes) == 0 {
-		snaptimes = append(snaptimes, snapTime{nil, now})
+		panic("implementation error: loop must either inc hardErrs or add result to snaptimes")
 	}
 
+	// sort ascending by (prio,time)
+	// => those filesystems with versions win over those without any
 	sort.Slice(snaptimes, func(i, j int) bool {
-		return snaptimes[i].time.Before(snaptimes[j].time)
+		if snaptimes[i].prio == snaptimes[j].prio {
+			return snaptimes[i].time.Before(snaptimes[j].time)
+		}
+		return snaptimes[i].prio < snaptimes[j].prio
 	})
 
+	winnerSyncPoint := snaptimes[0].time
+	l := log.WithField("syncPoint", winnerSyncPoint.String())
+	l.Info("determined sync point")
+	if winnerSyncPoint.Sub(now) > syncUpWarnNoSnapshotUntilSyncupMinDuration {
+		for _, st := range snaptimes {
+			if st.prio == prioNoVersions {
+				l.WithField("fs", st.ds.ToString()).Warn("filesystem will not be snapshotted until sync point")
+			}
+		}
+	}
+
 	return snaptimes[0].time, nil
 
 }
+
+var findSyncPointFSNoFilesystemVersionsErr = fmt.Errorf("no filesystem versions")
+
+func findSyncPointFSNextOptimalSnapshotTime(l Logger, now time.Time, interval time.Duration, prefix string, d *zfs.DatasetPath) (time.Time, error) {
+
+	fsvs, err := zfs.ZFSListFilesystemVersions(d, filters.NewTypedPrefixFilter(prefix, zfs.Snapshot))
+	if err != nil {
+		return time.Time{}, errors.Wrap(err, "list filesystem versions")
+	}
+	if len(fsvs) <= 0 {
+		return time.Time{}, findSyncPointFSNoFilesystemVersionsErr
+	}
+
+	// Sort versions by creation
+	sort.SliceStable(fsvs, func(i, j int) bool {
+		return fsvs[i].CreateTXG < fsvs[j].CreateTXG
+	})
+
+	latest := fsvs[len(fsvs)-1]
+	l.WithField("creation", latest.Creation).Debug("found latest snapshot")
+
+	since := now.Sub(latest.Creation)
+	if since < 0 {
+		return time.Time{}, fmt.Errorf("snapshot %q is from the future: creation=%q now=%q", latest.ToAbsPath(d), latest.Creation, now)
+	}
+
+	return latest.Creation.Add(interval), nil
+}

docs/changelog.rst

@@ -27,6 +27,43 @@ We use the following annotations for classifying changes:
 * |bugfix| Change that fixes a bug, no regressions or incompatibilities expected.
 * |docs| Change to the documentation.
 
+0.3
+---
+
+This is a big one! Headlining features:
+
+* **Resumable Send & Recv Support**
+  No knobs required, automatically used where supported.
+* **Hold-Protected Send & Recv**
+  Automatic ZFS holds to ensure that we can always resume a replication step.
+* **Encrypted Send & Recv Support** for OpenZFS native encryption.
+  :ref:`Configurable <job-send-options>` at the job level, i.e., for all filesystems a job is responsible for.
+* **Receive-side hold on last received dataset**
+  The counterpart to the replication cursor bookmark on the send-side.
+  Ensures that incremental replication will always be possible between a sender and receiver.
+
+Actual changelog:
+
+* |break_config| **more restrictive job names than in prior zrepl versions**
+  Starting with this version, job names are going to be embedded into ZFS holds and bookmark names.
+
+* |break| |mig| replication cursor representation changed
+
+  * zrepl now manages the :ref:`replication cursor bookmark <replication-cursor-and-last-received-hold>` per job-filesystem tuple instead of a single replication cursor per filesystem.
+    In the future, this will permit multiple sending jobs to send from the same filesystems.
+  * ZFS does not allow bookmark renaming, thus we cannot migrate the old replication cursors.
+  * zrepl 0.3 will automatically create cursors in the new format for new replications, and warn if it still finds ones in the old format.
+  * Run ``zrepl migrate replication-cursor:v1-v2`` to safely destroy old-format cursors.
+    The migration will ensure that only those old-format cursors are destroyed that have been superseeded by new-format cursors.
+
+* |bugfix| missing logger context vars in control connection handlers
+* |bugfix| improved error messages on ``zfs send`` errors
+* |feature| New option ``listen_freebind`` (tcp, tls, prometheus listener)
+* |bugfix| |docs| snapshotting: clarify sync-up behavior and warn about filesystems
+  that will not be snapshotted until the sync-up phase is over
+* |docs| Document new replication features in the :ref:`config overview <overview-how-replication-works>` and :repomasterlink:`replication/design.md`.
+* **[MAINTAINER NOTICE]** New platform tests in this version, please make sure you run them for your distro!
+
 0.2.1
 -----
 

docs/configuration.rst

@@ -11,6 +11,7 @@ Configuration
     configuration/jobs
     configuration/transports
     configuration/filter_syntax
+    configuration/sendrecvoptions
     configuration/snapshotting
     configuration/prune
     configuration/logging

docs/configuration/filter_syntax.rst

@@ -5,7 +5,7 @@
 Filter Syntax
 =============
 
-For :ref:`source jobs <job-source>` and :ref:`push jobs <job-push>`, a filesystem filter must be defined (field ``filesystems``).
+For :ref:`source<job-source>`, :ref:`push<job-push>` and :ref:`snap<job-snap>` jobs, a filesystem filter must be defined (field ``filesystems``).
 A filter takes a filesystem path (in the ZFS filesystem hierarchy) as parameter and returns ``true`` (pass) or ``false`` (block).
 
 A filter is specified as a **YAML dictionary** with patterns as keys and booleans as values.

docs/configuration/jobs.rst

@@ -24,6 +24,8 @@ Job Type ``push``
       - |connect-transport|
     * - ``filesystems``
       - |filter-spec| for filesystems to be snapshotted and pushed to the sink
+    * - ``send``
+      - |send-options| 
     * - ``snapshotting``
       - |snapshotting-spec|
     * - ``pruning``
@@ -101,6 +103,8 @@ Job Type ``source``
       - |serve-transport|
     * - ``filesystems``
       - |filter-spec| for filesystems to be snapshotted and exposed to connecting clients
+    * - ``send``
+      - |send-options| 
     * - ``snapshotting``
       - |snapshotting-spec|
 

docs/configuration/monitoring.rst

@@ -14,6 +14,7 @@ Prometheus & Grafana
 
 zrepl can expose `Prometheus metrics <https://prometheus.io/docs/instrumenting/exposition_formats/>`_ via HTTP.
 The ``listen`` attribute is a `net.Listen <https://golang.org/pkg/net/#Listen>`_  string for tcp, e.g. ``:9091`` or ``127.0.0.1:9091``.
+The ``listen_freebind`` attribute is :ref:`explained here <listen-freebind-explanation>`.
 The Prometheues monitoring job appears in the ``zrepl control`` job list and may be specified **at most once**.
 
 zrepl also ships with an importable `Grafana <https://grafana.com>`_ dashboard that consumes the Prometheus metrics:
@@ -30,6 +31,7 @@ The dashboard also contains some advice on which metrics are important to monito
       monitoring:
         - type: prometheus
           listen: ':9091'
+          listen_freebind: true # optional, default false
 
 
 

docs/configuration/overview.rst

@@ -90,6 +90,8 @@ It uses the client identity for access control:
 .. TIP::
    The implementation of the ``sink`` job requires that the connecting client identities be a valid ZFS filesystem name components.
 
+.. _overview-how-replication-works:
+
 How Replication Works
 ---------------------
 
@@ -107,9 +109,8 @@ The following steps take place during replication and can be monitored using the
     * Per filesystem, compute a diff between sender and receiver snapshots
     * Build a list of replication steps
 
-      * If possible, use incremental sends (``zfs send -i``)
+      * If possible, use incremental and resumable sends (``zfs send -i``)
       * Otherwise, use full send of most recent snapshot on sender
-      * Give up on filesystems that cannot be replicated without data loss
 
   * Retry on errors that are likely temporary (i.e. network failures).
   * Give up on filesystems where a permanent error was received over RPC.
@@ -119,17 +120,23 @@ The following steps take place during replication and can be monitored using the
   * Perform replication steps in the following order:
     Among all filesystems with pending replication steps, pick the filesystem whose next replication step's snapshot is the oldest.
   * Create placeholder filesystems on the receiving side to mirror the dataset paths on the sender to ``root_fs/${client_identity}``.
-  * After a successful replication step, update the replication cursor bookmark (see below).
+  * Aquire send-side step-holds on the step's `from` and `to` snapshots.
+  * Perform the replication step.
+  * Move the **replication cursor** bookmark on the sending side (see below).
+  * Move the **last-received-hold** on the receiving side (see below).
+  * Release the send-side step-holds.
    
 The idea behind the execution order of replication steps is that if the sender snapshots all filesystems simultaneously at fixed intervals, the receiver will have all filesystems snapshotted at time ``T1`` before the first snapshot at ``T2 = T1 + $interval`` is replicated.
 
-.. _replication-cursor-bookmark:
+.. _replication-cursor-and-last-received-hold:
 
-The **replication cursor bookmark** ``#zrepl_replication_cursor`` is kept per filesystem on the sending side of a replication setup:
-It is a bookmark of the most recent successfully replicated snapshot to the receiving side.
-It is is used by the :ref:`not_replicated <prune-keep-not-replicated>` keep rule to identify all snapshots that have not yet been replicated to the receiving side.
-Regardless of whether that keep rule is used, the bookmark ensures that replication can always continue incrementally.
-Note that there is only one cursor bookmark per filesystem, which prohibits multiple jobs to replicate the same filesystem (:ref:`see below<jobs-multiple-jobs>`).
+**Replication cursor** bookmark and **last-received-hold** are managed by zrepl to ensure that future replications can always be done incrementally:
+the replication cursor is a send-side bookmark of the most recent successfully replicated snapshot,
+and the last-received-hold is a hold of that snapshot on the receiving side.
+The replication cursor has the format ``#zrepl_CUSOR_G_<GUID>_J_<JOBNAME>``.
+The last-received-hold tag has the format ``#zrepl_last_received_J_<JOBNAME>``.
+Encoding the job name in the names ensures that multiple sending jobs can replicate the same filesystem to different receivers without interference.
+The ``zrepl holds list`` provides a listing of all bookmarks and holds managed by zrepl.
 
 .. _replication-placeholder-property:
 
@@ -144,9 +151,13 @@ The ``zrepl test placeholder`` command can be used to check whether a filesystem
 .. ATTENTION::
 
     Currently, zrepl does not replicate filesystem properties.
-    Whe receiving a filesystem, it is never mounted (`-u` flag)  and `mountpoint=none` is set.
+    When receiving a filesystem, it is never mounted (`-u` flag)  and `mountpoint=none` is set.
     This is temporary and being worked on :issue:`24`.
 
+.. NOTE::
+
+    More details can be found in the design document :repomasterlink:`replication/design.md`.
+
 
 .. _jobs-multiple-jobs:
 
@@ -171,7 +182,7 @@ No Overlapping
 Jobs run independently of each other.
 If two jobs match the same filesystem with their ``filesystems`` filter, they will operate on that filesystem independently and potentially in parallel.
 For example, if job A prunes snapshots that job B is planning to replicate, the replication will fail because B asssumed the snapshot to still be present.
-More subtle race conditions can occur with the :ref:`replication cursor bookmark <replication-cursor-bookmark>`, which currently only exists once per filesystem.
+However, the next replication attempt will re-examine the situation from scratch and should work.
 
 N push jobs to 1 sink
 ~~~~~~~~~~~~~~~~~~~~~

docs/configuration/prune.rst

@@ -4,7 +4,7 @@ Pruning Policies
 ================
 
 In zrepl, *pruning* means *destroying snapshots*.
-Pruning must happen on both sides of a replication or the systems would inevitable run out of disk space at some point.
+Pruning must happen on both sides of a replication or the systems would inevitably run out of disk space at some point.
 
 Typically, the requirements to temporal resolution and maximum retention time differ per side.
 For example, when using zrepl to back up a busy database server, you will want high temporal resolution (snapshots every 10 min) for the last 24h in case of administrative disasters, but cannot afford to store them for much longer because you might have high turnover volume in the database.
@@ -66,7 +66,7 @@ Policy ``not_replicated``
 
 ``not_replicated`` keeps all snapshots that have not been replicated to the receiving side.
 It only makes sense to specify this rule on a sender (source or push job).
-The state required to evaluate this rule is stored in the :ref:`replication cursor bookmark <replication-cursor-bookmark>` on the sending side.
+The state required to evaluate this rule is stored in the :ref:`replication cursor bookmark <replication-cursor-and-last-received-hold>` on the sending side.
 
 .. _prune-keep-retention-grid:
 

docs/configuration/sendrecvoptions.rst

@@ -0,0 +1,45 @@
+.. include:: ../global.rst.inc
+
+
+Send & Recv Options
+===================
+
+.. _job-send-options:
+
+Send Options
+~~~~~~~~~~~~
+
+::
+   
+   jobs:
+   - type: push
+     filesystems: ...
+     send:
+       encrypted: true
+     ...
+
+:ref:`Source<job-source>` and :ref:`push<job-push>` jobs have an optional ``send`` configuration section.
+
+``encryption`` option
+---------------------
+
+The ``encryption`` variable controls whether the matched filesystems are sent as `OpenZFS native encryption <http://open-zfs.org/wiki/ZFS-Native_Encryption>`_ raw sends.
+More specificially, if ``encryption=true``, zrepl
+
+* checks for any of the filesystems matched by ``filesystems`` whether the ZFS ``encryption`` property indicates that the filesystem is actually encrypted with ZFS native encryption and
+* invokes the ``zfs send`` subcommand with the ``-w`` option (raw sends) and
+* expects the receiving side to support OpenZFS native encryption (recv will fail otherwise)
+
+Filesystems matched by ``filesystems`` that are not encrypted are not sent and will cause error log messages.
+
+If ``encryption=false``, zrepl expects that filesystems matching ``filesystems`` are not encrypted or have loaded encryption keys.
+
+.. _job-recv-options:
+
+Recv Options
+~~~~~~~~~~~~
+
+:ref:`Sink<job-sink>` and :ref:`pull<job-pull>` jobs have an optional ``recv`` configuration section.
+However, there are currently no variables to configure there.
+
+

docs/configuration/snapshotting.rst

@@ -9,8 +9,15 @@ The ``push``, ``source`` and ``snap`` jobs can automatically take periodic snaps
 The snapshot names are composed of a user-defined prefix followed by a UTC date formatted like ``20060102_150405_000``.
 We use UTC because it will avoid name conflicts when switching time zones or between summer and winter time.
 
+When a job is started, the snapshotter attempts to get the snapshotting rhythms of the matched ``filesystems`` in sync because snapshotting all filesystems at the same time results in a more consistent backup.
+To find that sync point, the most recent snapshot, made by the snapshotter, in any of the matched ``filesystems`` is used.
+A filesystem that does not have snapshots by the snapshotter has lower priority than filesystem that do, and thus might not be snapshotted (and replicated) until it is snapshotted at the next sync point.
+
 For ``push`` jobs, replication is automatically triggered after all filesystems have been snapshotted.
 
+Note that the ``zrepl signal wakeup JOB`` subcommand does not trigger snapshotting.
+
+
 ::
 
     jobs:

docs/configuration/transports.rst

@@ -50,12 +50,18 @@ Serve
       serve:
         type: tcp
         listen: ":8888"
+        listen_freebind: true # optional, default false
         clients: {
           "192.168.122.123" : "mysql01"
           "192.168.122.123" : "mx01"
         }
       ...
 
+.. _listen-freebind-explanation:
+
+``listen_freebind`` controls whether the socket is allowed to bind to non-local or unconfigured IP addresses (Linux ``IP_FREEBIND`` , FreeBSD ``IP_BINDANY``).
+Enable this option if you want to ``listen`` on a specific IP address that might not yet be configured when the zrepl daemon starts.
+
 Connect
 ~~~~~~~
 
@@ -101,6 +107,7 @@ Serve
         serve:
           type: tls
           listen: ":8888"
+          listen_freebind: true # optional, default false
           ca:   /etc/zrepl/ca.crt
           cert: /etc/zrepl/prod.fullchain
           key:  /etc/zrepl/prod.key
@@ -110,6 +117,7 @@ Serve
 
 The ``ca`` field specified the certificate authority used to validate client certificates.
 The ``client_cns`` list specifies a list of accepted client common names (which are also the client identities for this transport).
+The ``listen_freebind`` field is :ref:`explained here <listen-freebind-explanation>`.
 
 Connect
 ~~~~~~~

docs/global.rst.inc

@@ -21,6 +21,8 @@
 
 .. |serve-transport| replace:: :ref:`serve specification<transport>`
 .. |connect-transport| replace:: :ref:`connect specification<transport>`
+.. |send-options| replace:: :ref:`send options<job-send-options>`, e.g. for encrypted sends
+.. |recv-options| replace:: :ref:`recv options<job-recv-options>`
 .. |snapshotting-spec| replace:: :ref:`snapshotting specification <job-snapshotting-spec>`
 .. |pruning-spec| replace:: :ref:`pruning specification <prune>`
 .. |filter-spec| replace:: :ref:`filter specification<pattern-filter>`

docs/index.rst

@@ -57,9 +57,11 @@ Main Features
   * Advanced replication features
 
     * [x] Automatic retries for temporary network errors
-    * [ ] Resumable send & receive
+    * [x] Automatic resumable send & receive
+    * [x] Automatic ZFS holds during send & receive
+    * [x] Automatic bookmark \& hold management for guaranteed incremental send & recv 
+    * [x] Encrypted raw send & receive to untrusted receivers (OpenZFS native encryption)
     * [ ] Compressed send & receive
-    * [ ] Raw encrypted send & receive
 
 * **Automatic snapshot management**
 
@@ -83,6 +85,7 @@ Main Features
 * **Maintainable implementation in Go**
 
   * [x] Cross platform
+  * [x] Dynamic feature checking
   * [x] Type safe & testable code
 
 

docs/installation.rst

@@ -52,6 +52,9 @@ The following list may be incomplete, feel free to submit a PR with an update:
     * - OmniOS
       - ``pkg install zrepl``
       - Available since `r151030 <https://pkg.omniosce.org/r151030/extra/en/search.shtml?token=zrepl&action=Search>`_
+    * - Void Linux
+      - ``xbps-install zrepl``
+      - Available since `a88a2a4 <https://github.com/void-linux/void-packages/commit/a88a2a4d7bf56072dadf61ab56b8424e39155890>`_
     * - Others
       -
       - Use `binary releases`_ or build from source.

docs/supporters.rst

@@ -32,7 +32,11 @@ We would like to thank the following people and organizations for supporting zre
 
    <div class="fa fa-code" style="width: 1em;"></div>
 
+* |supporter-gold| `Mateusz Kwiatkowski (runhyve.app) <https://runhyve.app>`_
+* |supporter-std| `Gaelan D'costa <https://www.robot-disco.net>`_
 * |supporter-std| `Tenzin Lhakhang <https://confluence.tenzin.io>`_
+* |supporter-std| `Lapo Luchini <https://github.com/lapo-luchini>`_
+* |supporter-std| `F. Schmid <https://github.com/tdschmidl>`_
 * |supporter-gold| `MNX.io <https://mnx.io>`_
 * |supporter-std| `Marshall Clyburn <https://github.com/mdclyburn>`_
 * |supporter-code| `Ross Williams <https://github.com/overhacked>`_
@@ -40,4 +44,5 @@ We would like to thank the following people and organizations for supporting zre
 * |supporter-code| `Justin Scholz <https://github.com/JMoVS>`_
 * |supporter-code| `InsanePrawn <https://github.com/InsanePrawn>`_
 * |supporter-code| `Ben Woods <https://www.freshports.org/sysutils/zrepl/>`_
+* |supporter-code| `Janis Streib <https://github.com/janisstreib>`_
 * |supporter-code| `Anton Schirg <https://github.com/antonxy>`_

docs/tutorial.rst

@@ -52,9 +52,9 @@ Follow the :ref:`OS-specific installation instructions <installation>` and come
 Generate TLS Certificates
 -------------------------
 
-We use the `TLS client authentication transport <transport-tcp+tlsclientauth>` to protect our data on the wire.
+We use the :ref:`TLS client authentication transport <transport-tcp+tlsclientauth>` to protect our data on the wire.
 To get things going quickly, we skip setting up a CA and generate two self-signed certificates as described :ref:`here <transport-tcp+tlsclientauth-2machineopenssl>`.
-Again, for convenience, We generate the key pairs on our local machine and distribute them using ssh:
+For convenience, we generate the key pairs on our local machine and distribute them using ssh:
 
 .. code-block:: bash
    :emphasize-lines: 6,13
@@ -138,7 +138,7 @@ We define a corresponding **sink job** named ``sink`` in ``/etc/zrepl/zrepl.yml`
 Apply Configuration Changes
 ---------------------------
 
-We use ``zrepl configcheck`` before to catch any configuration errors: no output indicates that everything is fine.
+We use ``zrepl configcheck`` to catch any configuration errors: no output indicates that everything is fine.
 If that is the case, restart the zrepl daemon on **both** ``prod`` and ``backups`` using ``service zrepl restart`` or ``systemctl restart zrepl``.
 
 
@@ -175,4 +175,3 @@ Congratulations, you have a working push backup. Where to go next?
 
 * Read more about :ref:`configuration format, options & job types <configuration_toc>`
 * Configure :ref:`logging <logging>` \& :ref:`monitoring <monitoring>`.
-

endpoint/endpoint.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"path"
+	"sync"
 
 	"github.com/pkg/errors"
 
@@ -15,13 +16,39 @@ import (
 	"github.com/zrepl/zrepl/zfs"
 )
 
+type SenderConfig struct {
+	FSF     zfs.DatasetFilter
+	Encrypt *zfs.NilBool
+	JobID   JobID
+}
+
+func (c *SenderConfig) Validate() error {
+	c.JobID.MustValidate()
+	if err := c.Encrypt.Validate(); err != nil {
+		return errors.Wrap(err, "`Encrypt` field invalid")
+	}
+	if _, err := StepHoldTag(c.JobID); err != nil {
+		return fmt.Errorf("JobID cannot be used for hold tag: %s", err)
+	}
+	return nil
+}
+
 // Sender implements replication.ReplicationEndpoint for a sending side
 type Sender struct {
 	FSFilter zfs.DatasetFilter
+	encrypt  *zfs.NilBool
+	jobId    JobID
 }
 
-func NewSender(fsf zfs.DatasetFilter) *Sender {
-	return &Sender{FSFilter: fsf}
+func NewSender(conf SenderConfig) *Sender {
+	if err := conf.Validate(); err != nil {
+		panic("invalid config" + err.Error())
+	}
+	return &Sender{
+		FSFilter: conf.FSF,
+		encrypt:  conf.Encrypt,
+		jobId:    conf.JobID,
+	}
 }
 
 func (s *Sender) filterCheckFS(fs string) (*zfs.DatasetPath, error) {
@@ -49,10 +76,15 @@ func (s *Sender) ListFilesystems(ctx context.Context, r *pdu.ListFilesystemReq)
 	}
 	rfss := make([]*pdu.Filesystem, len(fss))
 	for i := range fss {
+		encEnabled, err := zfs.ZFSGetEncryptionEnabled(ctx, fss[i].ToString())
+		if err != nil {
+			return nil, errors.Wrap(err, "cannot get filesystem encryption status")
+		}
 		rfss[i] = &pdu.Filesystem{
 			Path: fss[i].ToString(),
-			// FIXME: not supporting ResumeToken yet
+			// ResumeToken does not make sense from Sender
 			IsPlaceholder: false, // sender FSs are never placeholders
+			IsEncrypted:   encEnabled,
 		}
 	}
 	res := &pdu.ListFilesystemRes{Filesystems: rfss}
@@ -77,13 +109,86 @@ func (s *Sender) ListFilesystemVersions(ctx context.Context, r *pdu.ListFilesyst
 
 }
 
+func (p *Sender) HintMostRecentCommonAncestor(ctx context.Context, r *pdu.HintMostRecentCommonAncestorReq) (*pdu.HintMostRecentCommonAncestorRes, error) {
+	var err error
+
+	fs := r.GetFilesystem()
+	mostRecent, err := sendArgsFromPDUAndValidateExists(ctx, fs, r.GetSenderVersion())
+	if err != nil {
+		msg := "HintMostRecentCommonAncestor rpc with nonexistent most recent version"
+		getLogger(ctx).WithField("fs", fs).WithField("hinted_most_recent", fmt.Sprintf("%#v", mostRecent)).
+			Warn(msg)
+		return nil, errors.Wrap(err, msg)
+	}
+
+	// move replication cursor to this position
+	_, err = MoveReplicationCursor(ctx, fs, mostRecent, p.jobId)
+	if err == zfs.ErrBookmarkCloningNotSupported {
+		getLogger(ctx).Debug("not creating replication cursor from bookmark because ZFS does not support it")
+		// fallthrough
+	} else if err != nil {
+		return nil, errors.Wrap(err, "cannot set replication cursor to hinted version")
+	}
+
+	// cleanup previous steps
+	if err := ReleaseStepAll(ctx, fs, mostRecent, p.jobId); err != nil {
+		return nil, errors.Wrap(err, "cannot cleanup prior invocation's step holds and bookmarks")
+	}
+
+	return &pdu.HintMostRecentCommonAncestorRes{}, nil
+}
+
 var maxConcurrentZFSSendSemaphore = semaphore.New(envconst.Int64("ZREPL_ENDPOINT_MAX_CONCURRENT_SEND", 10))
 
+func uncheckedSendArgsFromPDU(fsv *pdu.FilesystemVersion) *zfs.ZFSSendArgVersion {
+	if fsv == nil {
+		return nil
+	}
+	return &zfs.ZFSSendArgVersion{RelName: fsv.GetRelName(), GUID: fsv.Guid}
+}
+
+func sendArgsFromPDUAndValidateExists(ctx context.Context, fs string, fsv *pdu.FilesystemVersion) (*zfs.ZFSSendArgVersion, error) {
+	v := uncheckedSendArgsFromPDU(fsv)
+	if v == nil {
+		return nil, errors.New("must not be nil")
+	}
+	if err := v.ValidateExists(ctx, fs); err != nil {
+		return nil, err
+	}
+	return v, nil
+}
+
 func (s *Sender) Send(ctx context.Context, r *pdu.SendReq) (*pdu.SendRes, zfs.StreamCopier, error) {
+
 	_, err := s.filterCheckFS(r.Filesystem)
 	if err != nil {
 		return nil, nil, err
 	}
+	switch r.Encrypted {
+	case pdu.Tri_DontCare:
+		// use s.encrypt setting
+		// ok, fallthrough outer
+	case pdu.Tri_False:
+		if s.encrypt.B {
+			return nil, nil, errors.New("only encrytped sends allowed (send -w + encryption!= off), but unencrytped send requested")
+		}
+		// fallthrough outer
+	case pdu.Tri_True:
+		if !s.encrypt.B {
+			return nil, nil, errors.New("only unencrypted sends allowed, but encrypted send requested")
+		}
+		// fallthrough outer
+	default:
+		return nil, nil, fmt.Errorf("unknown pdu.Tri variant %q", r.Encrypted)
+	}
+
+	sendArgs := zfs.ZFSSendArgs{
+		FS:          r.Filesystem,
+		From:        uncheckedSendArgsFromPDU(r.GetFrom()), // validated by zfs.ZFSSendDry / zfs.ZFSSend
+		To:          uncheckedSendArgsFromPDU(r.GetTo()),   // validated by zfs.ZFSSendDry / zfs.ZFSSend
+		Encrypted:   s.encrypt,
+		ResumeToken: r.ResumeToken, // nil or not nil, depending on decoding success
+	}
 
 	getLogger(ctx).Debug("acquire concurrent send semaphore")
 	// TODO use try-acquire and fail with resource-exhaustion rpc status
@@ -95,28 +200,154 @@ func (s *Sender) Send(ctx context.Context, r *pdu.SendReq) (*pdu.SendRes, zfs.St
 	}
 	defer guard.Release()
 
-	si, err := zfs.ZFSSendDry(r.Filesystem, r.From, r.To, "")
+	si, err := zfs.ZFSSendDry(ctx, sendArgs)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, errors.Wrap(err, "zfs send dry failed")
 	}
 
+	// From now on, assume that sendArgs has been validated by ZFSSendDry
+	// (because validation invovles shelling out, it's actually a little expensive)
+
 	var expSize int64 = 0      // protocol says 0 means no estimate
 	if si.SizeEstimate != -1 { // but si returns -1 for no size estimate
 		expSize = si.SizeEstimate
 	}
-	res := &pdu.SendRes{ExpectedSize: expSize}
+	res := &pdu.SendRes{
+		ExpectedSize:    expSize,
+		UsedResumeToken: r.ResumeToken != "",
+	}
 
 	if r.DryRun {
 		return res, nil, nil
 	}
 
-	streamCopier, err := zfs.ZFSSend(ctx, r.Filesystem, r.From, r.To, "")
+	// update replication cursor
+	if sendArgs.From != nil {
+		// For all but the first replication, this should always be a no-op because SendCompleted already moved the cursor
+		_, err = MoveReplicationCursor(ctx, sendArgs.FS, sendArgs.From, s.jobId)
+		if err == zfs.ErrBookmarkCloningNotSupported {
+			getLogger(ctx).Debug("not creating replication cursor from bookmark because ZFS does not support it")
+			// fallthrough
+		} else if err != nil {
+			return nil, nil, errors.Wrap(err, "cannot set replication cursor to `from` version before starting send")
+		}
+	}
+
+	// make sure `From` doesn't go away in order to make this step resumable
+	if sendArgs.From != nil {
+		err := HoldStep(ctx, sendArgs.FS, sendArgs.From, s.jobId)
+		if err == zfs.ErrBookmarkCloningNotSupported {
+			getLogger(ctx).Debug("not creating step bookmark because ZFS does not support it")
+			// fallthrough
+		} else if err != nil {
+			return nil, nil, errors.Wrap(err, "cannot create step bookmark")
+		}
+	}
+	// make sure `To` doesn't go away in order to make this step resumable
+	err = HoldStep(ctx, sendArgs.FS, sendArgs.To, s.jobId)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, errors.Wrapf(err, "cannot hold `to` version %q before starting send", sendArgs.To.RelName)
+	}
+
+	// step holds & replication cursor released / moved forward in s.SendCompleted => s.moveCursorAndReleaseSendHolds
+
+	streamCopier, err := zfs.ZFSSend(ctx, sendArgs)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "zfs send failed")
 	}
 	return res, streamCopier, nil
 }
 
+func (p *Sender) SendCompleted(ctx context.Context, r *pdu.SendCompletedReq) (*pdu.SendCompletedRes, error) {
+	orig := r.GetOriginalReq() // may be nil, always use proto getters
+	fs := orig.GetFilesystem()
+
+	var err error
+	var from *zfs.ZFSSendArgVersion
+	if orig.GetFrom() != nil {
+		from, err = sendArgsFromPDUAndValidateExists(ctx, fs, orig.GetFrom()) // no shadow
+		if err != nil {
+			return nil, errors.Wrap(err, "validate `from` exists")
+		}
+	}
+	to, err := sendArgsFromPDUAndValidateExists(ctx, fs, orig.GetTo())
+	if err != nil {
+		return nil, errors.Wrap(err, "validate `to` exists")
+	}
+
+	log := getLogger(ctx).WithField("to_guid", to.GUID).
+		WithField("fs", fs).
+		WithField("to", to.RelName)
+	if from != nil {
+		log = log.WithField("from", from.RelName).WithField("from_guid", from.GUID)
+	}
+
+	log.Debug("move replication cursor to most recent common version")
+	destroyedCursors, err := MoveReplicationCursor(ctx, fs, to, p.jobId)
+	if err != nil {
+		if err == zfs.ErrBookmarkCloningNotSupported {
+			log.Debug("not setting replication cursor, bookmark cloning not supported")
+		} else {
+			msg := "cannot move replication cursor, keeping hold on `to` until successful"
+			log.WithError(err).Error(msg)
+			err = errors.Wrap(err, msg)
+			// it is correct to not release the hold if we can't move the cursor!
+			return &pdu.SendCompletedRes{}, err
+		}
+	} else {
+		log.Info("successfully moved replication cursor")
+	}
+
+	// kick off releasing of step holds / bookmarks
+	// if we fail to release them, don't bother the caller:
+	// they are merely an implementation detail on the sender for better resumability
+	var wg sync.WaitGroup
+	wg.Add(2)
+	go func() {
+		defer wg.Done()
+		log.Debug("release step-hold of or step-bookmark on `to`")
+		err = ReleaseStep(ctx, fs, to, p.jobId)
+		if err != nil {
+			log.WithError(err).Error("cannot release step-holds on or destroy step-bookmark of `to`")
+		} else {
+			log.Info("successfully released step-holds on or destroyed step-bookmark of `to`")
+		}
+
+	}()
+	go func() {
+		defer wg.Done()
+		if from == nil {
+			return
+		}
+		log.Debug("release step-hold of or step-bookmark on `from`")
+		err := ReleaseStep(ctx, fs, from, p.jobId)
+		if err != nil {
+			if dne, ok := err.(*zfs.DatasetDoesNotExist); ok {
+				// If bookmark cloning is not supported, `from` might be the old replication cursor
+				// and thus have already been destroyed by MoveReplicationCursor above
+				// In that case, nonexistence of `from` is not an error, otherwise it is.
+				fsp, err := zfs.NewDatasetPath(fs)
+				if err != nil {
+					panic(err) // fs has been validated multiple times above
+				}
+				for _, fsv := range destroyedCursors {
+					if fsv.ToAbsPath(fsp) == dne.Path {
+						log.Info("`from` was a replication cursor and has already been destroyed")
+						return
+					}
+				}
+				// fallthrough
+			}
+			log.WithError(err).Error("cannot release step-holds on or destroy step-bookmark of `from`")
+		} else {
+			log.Info("successfully released step-holds on or destroyed step-bookmark of `from`")
+		}
+	}()
+	wg.Wait()
+
+	return &pdu.SendCompletedRes{}, nil
+}
+
 func (p *Sender) DestroySnapshots(ctx context.Context, req *pdu.DestroySnapshotsReq) (*pdu.DestroySnapshotsRes, error) {
 	dp, err := p.filterCheckFS(req.Filesystem)
 	if err != nil {
@@ -146,25 +377,14 @@ func (p *Sender) ReplicationCursor(ctx context.Context, req *pdu.ReplicationCurs
 		return nil, err
 	}
 
-	switch op := req.Op.(type) {
-	case *pdu.ReplicationCursorReq_Get:
-		cursor, err := zfs.ZFSGetReplicationCursor(dp)
-		if err != nil {
-			return nil, err
-		}
-		if cursor == nil {
-			return &pdu.ReplicationCursorRes{Result: &pdu.ReplicationCursorRes_Notexist{Notexist: true}}, nil
-		}
-		return &pdu.ReplicationCursorRes{Result: &pdu.ReplicationCursorRes_Guid{Guid: cursor.Guid}}, nil
-	case *pdu.ReplicationCursorReq_Set:
-		guid, err := zfs.ZFSSetReplicationCursor(dp, op.Set.Snapshot)
-		if err != nil {
-			return nil, err
-		}
-		return &pdu.ReplicationCursorRes{Result: &pdu.ReplicationCursorRes_Guid{Guid: guid}}, nil
-	default:
-		return nil, errors.Errorf("unknown op %T", op)
+	cursor, err := GetMostRecentReplicationCursorOfJob(ctx, dp.ToString(), p.jobId)
+	if err != nil {
+		return nil, err
 	}
+	if cursor == nil {
+		return &pdu.ReplicationCursorRes{Result: &pdu.ReplicationCursorRes_Notexist{Notexist: true}}, nil
+	}
+	return &pdu.ReplicationCursorRes{Result: &pdu.ReplicationCursorRes_Guid{Guid: cursor.Guid}}, nil
 }
 
 func (p *Sender) Receive(ctx context.Context, r *pdu.ReceiveReq, receive zfs.StreamCopier) (*pdu.ReceiveRes, error) {
@@ -183,22 +403,42 @@ type FSMap interface { // FIXME unused
 	AsFilter() FSFilter
 }
 
+type ReceiverConfig struct {
+	JobID JobID
+
+	RootWithoutClientComponent *zfs.DatasetPath // TODO use
+	AppendClientIdentity       bool
+
+	UpdateLastReceivedHold bool
+}
+
+func (c *ReceiverConfig) copyIn() {
+	c.RootWithoutClientComponent = c.RootWithoutClientComponent.Copy()
+}
+
+func (c *ReceiverConfig) Validate() error {
+	c.JobID.MustValidate()
+	if c.RootWithoutClientComponent.Length() <= 0 {
+		return errors.New("RootWithoutClientComponent must not be an empty dataset path")
+	}
+	return nil
+}
+
 // Receiver implements replication.ReplicationEndpoint for a receiving side
 type Receiver struct {
-	rootWithoutClientComponent *zfs.DatasetPath
-	appendClientIdentity       bool
+	conf ReceiverConfig // validated
 
 	recvParentCreationMtx *chainlock.L
 }
 
-func NewReceiver(rootDataset *zfs.DatasetPath, appendClientIdentity bool) *Receiver {
-	if rootDataset.Length() <= 0 {
-		panic(fmt.Sprintf("root dataset must not be an empty path: %v", rootDataset))
+func NewReceiver(config ReceiverConfig) *Receiver {
+	config.copyIn()
+	if err := config.Validate(); err != nil {
+		panic(err)
 	}
 	return &Receiver{
-		rootWithoutClientComponent: rootDataset.Copy(),
-		appendClientIdentity:       appendClientIdentity,
-		recvParentCreationMtx:      chainlock.New(),
+		conf:                  config,
+		recvParentCreationMtx: chainlock.New(),
 	}
 }
 
@@ -221,8 +461,8 @@ func clientRoot(rootFS *zfs.DatasetPath, clientIdentity string) (*zfs.DatasetPat
 }
 
 func (s *Receiver) clientRootFromCtx(ctx context.Context) *zfs.DatasetPath {
-	if !s.appendClientIdentity {
-		return s.rootWithoutClientComponent.Copy()
+	if !s.conf.AppendClientIdentity {
+		return s.conf.RootWithoutClientComponent.Copy()
 	}
 
 	clientIdentity, ok := ctx.Value(ClientIdentityKey).(string)
@@ -230,7 +470,7 @@ func (s *Receiver) clientRootFromCtx(ctx context.Context) *zfs.DatasetPath {
 		panic(fmt.Sprintf("ClientIdentityKey context value must be set"))
 	}
 
-	clientRoot, err := clientRoot(s.rootWithoutClientComponent, clientIdentity)
+	clientRoot, err := clientRoot(s.conf.RootWithoutClientComponent, clientIdentity)
 	if err != nil {
 		panic(fmt.Sprintf("ClientIdentityContextKey must have been validated before invoking Receiver: %s", err))
 	}
@@ -282,8 +522,27 @@ func (s *Receiver) ListFilesystems(ctx context.Context, req *pdu.ListFilesystemR
 			err := errors.Errorf("inconsistent placeholder state: filesystem %q must exist in this context", a.ToString())
 			return nil, err
 		}
+		token, err := zfs.ZFSGetReceiveResumeTokenOrEmptyStringIfNotSupported(ctx, a)
+		if err != nil {
+			l.WithError(err).Error("cannot get receive resume token")
+			return nil, err
+		}
+		encEnabled, err := zfs.ZFSGetEncryptionEnabled(ctx, a.ToString())
+		if err != nil {
+			l.WithError(err).Error("cannot get encryption enabled status")
+			return nil, err
+		}
+		l.WithField("receive_resume_token", token).Debug("receive resume token")
+
 		a.TrimPrefix(root)
-		fss = append(fss, &pdu.Filesystem{Path: a.ToString(), IsPlaceholder: ph.IsPlaceholder})
+
+		fs := &pdu.Filesystem{
+			Path:          a.ToString(),
+			IsPlaceholder: ph.IsPlaceholder,
+			ResumeToken:   token,
+			IsEncrypted:   encEnabled,
+		}
+		fss = append(fss, fs)
 	}
 	if len(fss) == 0 {
 		getLogger(ctx).Debug("no filesystems found")
@@ -344,7 +603,18 @@ func (s *Receiver) Receive(ctx context.Context, req *pdu.ReceiveReq, receive zfs
 	root := s.clientRootFromCtx(ctx)
 	lp, err := subroot{root}.MapToLocal(req.Filesystem)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "`Filesystem` invalid")
+	}
+
+	to := uncheckedSendArgsFromPDU(req.GetTo())
+	if to == nil {
+		return nil, errors.New("`To` must not be nil")
+	}
+	if err := to.ValidateInMemory(lp.ToString()); err != nil {
+		return nil, errors.Wrap(err, "`To` invalid")
+	}
+	if !to.IsSnapshot() {
+		return nil, errors.New("`To` must be a snapshot")
 	}
 
 	// create placeholder parent filesystems as appropriate
@@ -380,11 +650,11 @@ func (s *Receiver) Receive(ctx context.Context, req *pdu.ReceiveReq, receive zfs
 			}
 
 			if !ph.FSExists {
-				if s.rootWithoutClientComponent.HasPrefix(v.Path) {
+				if s.conf.RootWithoutClientComponent.HasPrefix(v.Path) {
 					if v.Path.Length() == 1 {
 						visitErr = fmt.Errorf("pool %q not imported", v.Path.ToString())
 					} else {
-						visitErr = fmt.Errorf("root_fs %q does not exist", s.rootWithoutClientComponent.ToString())
+						visitErr = fmt.Errorf("root_fs %q does not exist", s.conf.RootWithoutClientComponent.ToString())
 					}
 					getLogger(ctx).WithError(visitErr).Error("placeholders are only created automatically below root_fs")
 					return false
@@ -422,6 +692,17 @@ func (s *Receiver) Receive(ctx context.Context, req *pdu.ReceiveReq, receive zfs
 		}
 	}
 
+	if req.ClearResumeToken && ph.FSExists {
+		if err := zfs.ZFSRecvClearResumeToken(lp.ToString()); err != nil {
+			return nil, errors.Wrap(err, "cannot clear resume token")
+		}
+	}
+
+	recvOpts.SavePartialRecvState, err = zfs.ResumeRecvSupported(ctx, lp)
+	if err != nil {
+		return nil, errors.Wrap(err, "cannot determine whether we can use resumable send & recv")
+	}
+
 	getLogger(ctx).Debug("acquire concurrent recv semaphore")
 	// TODO use try-acquire and fail with resource-exhaustion rpc status
 	// => would require handling on the client-side
@@ -434,13 +715,30 @@ func (s *Receiver) Receive(ctx context.Context, req *pdu.ReceiveReq, receive zfs
 
 	getLogger(ctx).WithField("opts", fmt.Sprintf("%#v", recvOpts)).Debug("start receive command")
 
-	if err := zfs.ZFSRecv(ctx, lp.ToString(), receive, recvOpts); err != nil {
+	snapFullPath := to.FullPath(lp.ToString())
+	if err := zfs.ZFSRecv(ctx, lp.ToString(), to, receive, recvOpts); err != nil {
 		getLogger(ctx).
 			WithError(err).
 			WithField("opts", recvOpts).
 			Error("zfs receive failed")
 		return nil, err
 	}
+
+	// validate that we actually received what the sender claimed
+	if err := to.ValidateExists(ctx, lp.ToString()); err != nil {
+		msg := "receive request's `To` version does not match what we received in the stream"
+		getLogger(ctx).WithError(err).WithField("snap", snapFullPath).Error(msg)
+		getLogger(ctx).Error("aborting recv request, but keeping received snapshot for inspection")
+		return nil, errors.Wrap(err, msg)
+	}
+
+	if s.conf.UpdateLastReceivedHold {
+		getLogger(ctx).Debug("move last-received-hold")
+		if err := MoveLastReceivedHold(ctx, lp.ToString(), *to, s.conf.JobID); err != nil {
+			return nil, errors.Wrap(err, "cannot move last-received-hold")
+		}
+	}
+
 	return &pdu.ReceiveRes{}, nil
 }
 
@@ -453,6 +751,19 @@ func (s *Receiver) DestroySnapshots(ctx context.Context, req *pdu.DestroySnapsho
 	return doDestroySnapshots(ctx, lp, req.Snapshots)
 }
 
+func (p *Receiver) HintMostRecentCommonAncestor(ctx context.Context, r *pdu.HintMostRecentCommonAncestorReq) (*pdu.HintMostRecentCommonAncestorRes, error) {
+	// we don't move last-received-hold as part of this hint
+	// because that wouldn't give us any benefit wrt resumability.
+	//
+	// Other reason: the replication logic that issues this RPC would require refactoring
+	// to include the receiver's FilesystemVersion in the request)
+	return &pdu.HintMostRecentCommonAncestorRes{}, nil
+}
+
+func (p *Receiver) SendCompleted(context.Context, *pdu.SendCompletedReq) (*pdu.SendCompletedRes, error) {
+	return &pdu.SendCompletedRes{}, nil
+}
+
 func doDestroySnapshots(ctx context.Context, lp *zfs.DatasetPath, snaps []*pdu.FilesystemVersion) (*pdu.DestroySnapshotsRes, error) {
 	reqs := make([]*zfs.DestroySnapOp, len(snaps))
 	ress := make([]*pdu.DestroySnapshotRes, len(snaps))

endpoint/endpoint_zfs.go

@@ -0,0 +1,503 @@
+package endpoint
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+	"sort"
+
+	"github.com/kr/pretty"
+	"github.com/pkg/errors"
+
+	"github.com/zrepl/zrepl/zfs"
+)
+
+var stepHoldTagRE = regexp.MustCompile("^zrepl_STEP_J_(.+)")
+
+func StepHoldTag(jobid JobID) (string, error) {
+	return stepHoldTagImpl(jobid.String())
+}
+
+func stepHoldTagImpl(jobid string) (string, error) {
+	t := fmt.Sprintf("zrepl_STEP_J_%s", jobid)
+	if err := zfs.ValidHoldTag(t); err != nil {
+		return "", err
+	}
+	return t, nil
+}
+
+// err != nil always means that the bookmark is not a step bookmark
+func ParseStepHoldTag(tag string) (JobID, error) {
+	match := stepHoldTagRE.FindStringSubmatch(tag)
+	if match == nil {
+		return JobID{}, fmt.Errorf("parse hold tag: match regex %q", stepHoldTagRE)
+	}
+	jobID, err := MakeJobID(match[1])
+	if err != nil {
+		return JobID{}, errors.Wrap(err, "parse hold tag: invalid job id field")
+	}
+	return jobID, nil
+}
+
+const stepBookmarkNamePrefix = "zrepl_STEP"
+
+// v must be validated by caller
+func StepBookmarkName(fs string, guid uint64, id JobID) (string, error) {
+	return stepBookmarkNameImpl(fs, guid, id.String())
+}
+
+func stepBookmarkNameImpl(fs string, guid uint64, jobid string) (string, error) {
+	return makeJobAndGuidBookmarkName(stepBookmarkNamePrefix, fs, guid, jobid)
+}
+
+// name is the full bookmark name, including dataset path
+//
+// err != nil always means that the bookmark is not a step bookmark
+func ParseStepBookmarkName(fullname string) (guid uint64, jobID JobID, err error) {
+	guid, jobID, err = parseJobAndGuidBookmarkName(fullname, stepBookmarkNamePrefix)
+	if err != nil {
+		err = errors.Wrap(err, "parse step bookmark name") // no shadow!
+	}
+	return guid, jobID, err
+}
+
+const replicationCursorBookmarkNamePrefix = "zrepl_CURSOR"
+
+func ReplicationCursorBookmarkName(fs string, guid uint64, id JobID) (string, error) {
+	return replicationCursorBookmarkNameImpl(fs, guid, id.String())
+}
+
+func replicationCursorBookmarkNameImpl(fs string, guid uint64, jobid string) (string, error) {
+	return makeJobAndGuidBookmarkName(replicationCursorBookmarkNamePrefix, fs, guid, jobid)
+}
+
+var ErrV1ReplicationCursor = fmt.Errorf("bookmark name is a v1-replication cursor")
+
+//err != nil always means that the bookmark is not a valid replication bookmark
+//
+// Returns ErrV1ReplicationCursor as error if the bookmark is a v1 replication cursor
+func ParseReplicationCursorBookmarkName(fullname string) (uint64, JobID, error) {
+
+	// check for legacy cursors
+	{
+		if err := zfs.EntityNamecheck(fullname, zfs.EntityTypeBookmark); err != nil {
+			return 0, JobID{}, errors.Wrap(err, "parse replication cursor bookmark name")
+		}
+		_, _, name, err := zfs.DecomposeVersionString(fullname)
+		if err != nil {
+			return 0, JobID{}, errors.Wrap(err, "parse replication cursor bookmark name: decompose version string")
+		}
+		const V1ReplicationCursorBookmarkName = "zrepl_replication_cursor"
+		if name == V1ReplicationCursorBookmarkName {
+			return 0, JobID{}, ErrV1ReplicationCursor
+		}
+	}
+
+	guid, jobID, err := parseJobAndGuidBookmarkName(fullname, replicationCursorBookmarkNamePrefix)
+	if err != nil {
+		err = errors.Wrap(err, "parse replication cursor bookmark name") // no shadow
+	}
+	return guid, jobID, err
+}
+
+// may return nil for both values, indicating there is no cursor
+func GetMostRecentReplicationCursorOfJob(ctx context.Context, fs string, jobID JobID) (*zfs.FilesystemVersion, error) {
+	fsp, err := zfs.NewDatasetPath(fs)
+	if err != nil {
+		return nil, err
+	}
+	candidates, err := GetReplicationCursors(ctx, fsp, jobID)
+	if err != nil || len(candidates) == 0 {
+		return nil, err
+	}
+
+	sort.Slice(candidates, func(i, j int) bool {
+		return candidates[i].CreateTXG < candidates[j].CreateTXG
+	})
+
+	mostRecent := candidates[len(candidates)-1]
+	return &mostRecent, nil
+}
+
+func GetReplicationCursors(ctx context.Context, fs *zfs.DatasetPath, jobID JobID) ([]zfs.FilesystemVersion, error) {
+
+	listOut := &ListHoldsAndBookmarksOutput{}
+	if err := listZFSHoldsAndBookmarksImplFS(ctx, listOut, fs); err != nil {
+		return nil, errors.Wrap(err, "get replication cursor: list bookmarks and holds")
+	}
+
+	if len(listOut.V1ReplicationCursors) > 0 {
+		getLogger(ctx).WithField("bookmark", pretty.Sprint(listOut.V1ReplicationCursors)).
+			Warn("found v1-replication cursor bookmarks, consider running migration 'replication-cursor:v1-v2' after successful replication with this zrepl version")
+	}
+
+	candidates := make([]zfs.FilesystemVersion, 0)
+	for _, v := range listOut.ReplicationCursorBookmarks {
+		zv := zfs.ZFSSendArgVersion{
+			RelName: "#" + v.Name,
+			GUID:    v.Guid,
+		}
+		if err := zv.ValidateExists(ctx, v.FS); err != nil {
+			getLogger(ctx).WithError(err).WithField("bookmark", zv.FullPath(v.FS)).
+				Error("found invalid replication cursor bookmark")
+			continue
+		}
+		candidates = append(candidates, v.v)
+	}
+
+	return candidates, nil
+}
+
+// `target` is validated before replication cursor is set. if validation fails, the cursor is not moved.
+//
+// returns ErrBookmarkCloningNotSupported if version is a bookmark and bookmarking bookmarks is not supported by ZFS
+func MoveReplicationCursor(ctx context.Context, fs string, target *zfs.ZFSSendArgVersion, jobID JobID) (destroyedCursors []zfs.FilesystemVersion, err error) {
+
+	if !target.IsSnapshot() {
+		return nil, zfs.ErrBookmarkCloningNotSupported
+	}
+
+	snapProps, err := target.ValidateExistsAndGetCheckedProps(ctx, fs)
+	if err != nil {
+		return nil, errors.Wrapf(err, "invalid replication cursor target %q (guid=%v)", target.RelName, target.GUID)
+	}
+
+	bookmarkname, err := ReplicationCursorBookmarkName(fs, snapProps.Guid, jobID)
+	if err != nil {
+		return nil, errors.Wrap(err, "determine replication cursor name")
+	}
+
+	// idempotently create bookmark (guid is encoded in it, hence we'll most likely add a new one
+	// cleanup the old one afterwards
+
+	err = zfs.ZFSBookmark(fs, *target, bookmarkname)
+	if err != nil {
+		if err == zfs.ErrBookmarkCloningNotSupported {
+			return nil, err // TODO go1.13 use wrapping
+		}
+		return nil, errors.Wrapf(err, "cannot create bookmark")
+	}
+
+	destroyedCursors, err = DestroyObsoleteReplicationCursors(ctx, fs, target, jobID)
+	if err != nil {
+		return nil, errors.Wrap(err, "destroy obsolete replication cursors")
+	}
+
+	return destroyedCursors, nil
+}
+
+func DestroyObsoleteReplicationCursors(ctx context.Context, fs string, target *zfs.ZFSSendArgVersion, jobID JobID) (destroyed []zfs.FilesystemVersion, err error) {
+	return destroyBookmarksOlderThan(ctx, fs, target, jobID, func(shortname string) (accept bool) {
+		_, parsedID, err := ParseReplicationCursorBookmarkName(fs + "#" + shortname)
+		return err == nil && parsedID == jobID
+	})
+}
+
+// idempotently hold / step-bookmark `version`
+//
+// returns ErrBookmarkCloningNotSupported if version is a bookmark and bookmarking bookmarks is not supported by ZFS
+func HoldStep(ctx context.Context, fs string, v *zfs.ZFSSendArgVersion, jobID JobID) error {
+	if err := v.ValidateExists(ctx, fs); err != nil {
+		return err
+	}
+	if v.IsSnapshot() {
+
+		tag, err := StepHoldTag(jobID)
+		if err != nil {
+			return errors.Wrap(err, "step hold tag")
+		}
+
+		if err := zfs.ZFSHold(ctx, fs, *v, tag); err != nil {
+			return errors.Wrap(err, "step hold: zfs")
+		}
+
+		return nil
+	}
+
+	v.MustBeBookmark()
+
+	bmname, err := StepBookmarkName(fs, v.GUID, jobID)
+	if err != nil {
+		return errors.Wrap(err, "create step bookmark: determine bookmark name")
+	}
+	// idempotently create bookmark
+	err = zfs.ZFSBookmark(fs, *v, bmname)
+	if err != nil {
+		if err == zfs.ErrBookmarkCloningNotSupported {
+			// TODO we could actually try to find a local snapshot that has the requested GUID
+			// 		however, the replication algorithm prefers snapshots anyways, so this quest
+			// 		is most likely not going to be successful. Also, there's the possibility that
+			//      the caller might want to filter what snapshots are eligibile, and this would
+			//      complicate things even further.
+			return err // TODO go1.13 use wrapping
+		}
+		return errors.Wrap(err, "create step bookmark: zfs")
+	}
+	return nil
+}
+
+// idempotently release the step-hold on v if v is a snapshot
+// or idempotently destroy the step-bookmark  of v if v is a bookmark
+//
+// note that this operation leaves v itself untouched, unless v is the step-bookmark itself, in which case v is destroyed
+//
+// returns an instance of *zfs.DatasetDoesNotExist if `v` does not exist
+func ReleaseStep(ctx context.Context, fs string, v *zfs.ZFSSendArgVersion, jobID JobID) error {
+
+	if err := v.ValidateExists(ctx, fs); err != nil {
+		return err
+	}
+
+	if v.IsSnapshot() {
+		tag, err := StepHoldTag(jobID)
+		if err != nil {
+			return errors.Wrap(err, "step release tag")
+		}
+
+		if err := zfs.ZFSRelease(ctx, tag, v.FullPath(fs)); err != nil {
+			return errors.Wrap(err, "step release: zfs")
+		}
+
+		return nil
+	}
+
+	v.MustBeBookmark()
+
+	bmname, err := StepBookmarkName(fs, v.GUID, jobID)
+	if err != nil {
+		return errors.Wrap(err, "step release: determine bookmark name")
+	}
+	// idempotently destroy bookmark
+
+	if err := zfs.ZFSDestroyIdempotent(bmname); err != nil {
+		return errors.Wrap(err, "step release: bookmark destroy: zfs")
+	}
+
+	return nil
+}
+
+// release {step holds, step bookmarks} earlier and including `mostRecent`
+func ReleaseStepAll(ctx context.Context, fs string, mostRecent *zfs.ZFSSendArgVersion, jobID JobID) error {
+
+	if err := mostRecent.ValidateInMemory(fs); err != nil {
+		return err
+	}
+
+	tag, err := StepHoldTag(jobID)
+	if err != nil {
+		return errors.Wrap(err, "step release all: tag")
+	}
+
+	err = zfs.ZFSReleaseAllOlderAndIncludingGUID(ctx, fs, mostRecent.GUID, tag)
+	if err != nil {
+		return errors.Wrapf(err, "step release all: release holds older and including %q", mostRecent.FullPath(fs))
+	}
+
+	_, err = destroyBookmarksOlderThan(ctx, fs, mostRecent, jobID, func(shortname string) bool {
+		_, parsedId, parseErr := ParseStepBookmarkName(fs + "#" + shortname)
+		return parseErr == nil && parsedId == jobID
+	})
+	if err != nil {
+		return errors.Wrapf(err, "step release all: destroy bookmarks older than %q", mostRecent.FullPath(fs))
+	}
+
+	return nil
+}
+
+var lastReceivedHoldTagRE = regexp.MustCompile("^zrepl_last_received_J_(.+)$")
+
+// err != nil always means that the bookmark is not a step bookmark
+func ParseLastReceivedHoldTag(tag string) (JobID, error) {
+	match := lastReceivedHoldTagRE.FindStringSubmatch(tag)
+	if match == nil {
+		return JobID{}, errors.Errorf("parse last-received-hold tag: does not match regex %s", lastReceivedHoldTagRE.String())
+	}
+	jobId, err := MakeJobID(match[1])
+	if err != nil {
+		return JobID{}, errors.Wrap(err, "parse last-received-hold tag: invalid job id field")
+	}
+	return jobId, nil
+}
+
+func LastReceivedHoldTag(jobID JobID) (string, error) {
+	return lastReceivedHoldImpl(jobID.String())
+}
+
+func lastReceivedHoldImpl(jobid string) (string, error) {
+	tag := fmt.Sprintf("zrepl_last_received_J_%s", jobid)
+	if err := zfs.ValidHoldTag(tag); err != nil {
+		return "", err
+	}
+	return tag, nil
+}
+
+func MoveLastReceivedHold(ctx context.Context, fs string, to zfs.ZFSSendArgVersion, jobID JobID) error {
+	if err := to.ValidateExists(ctx, fs); err != nil {
+		return err
+	}
+	if err := zfs.EntityNamecheck(to.FullPath(fs), zfs.EntityTypeSnapshot); err != nil {
+		return err
+	}
+
+	tag, err := LastReceivedHoldTag(jobID)
+	if err != nil {
+		return errors.Wrap(err, "last-received-hold: hold tag")
+	}
+
+	// we never want to be without a hold
+	// => hold new one before releasing old hold
+
+	err = zfs.ZFSHold(ctx, fs, to, tag)
+	if err != nil {
+		return errors.Wrap(err, "last-received-hold: hold newly received")
+	}
+
+	err = zfs.ZFSReleaseAllOlderThanGUID(ctx, fs, to.GUID, tag)
+	if err != nil {
+		return errors.Wrap(err, "last-received-hold: release older holds")
+	}
+
+	return nil
+}
+
+type ListHoldsAndBookmarksOutputBookmarkV1ReplicationCursor struct {
+	FS   string
+	Name string
+}
+
+type ListHoldsAndBookmarksOutput struct {
+	StepBookmarks []*ListHoldsAndBookmarksOutputBookmark
+	StepHolds     []*ListHoldsAndBookmarksOutputHold
+
+	ReplicationCursorBookmarks []*ListHoldsAndBookmarksOutputBookmark
+	V1ReplicationCursors       []*ListHoldsAndBookmarksOutputBookmarkV1ReplicationCursor
+	LastReceivedHolds          []*ListHoldsAndBookmarksOutputHold
+}
+
+type ListHoldsAndBookmarksOutputBookmark struct {
+	FS, Name string
+	Guid     uint64
+	JobID    JobID
+	v        zfs.FilesystemVersion
+}
+
+type ListHoldsAndBookmarksOutputHold struct {
+	FS            string
+	Snap          string
+	SnapGuid      uint64
+	SnapCreateTXG uint64
+	Tag           string
+	JobID         JobID
+}
+
+// List all holds and bookmarks managed by endpoint
+func ListZFSHoldsAndBookmarks(ctx context.Context, fsfilter zfs.DatasetFilter) (*ListHoldsAndBookmarksOutput, error) {
+
+	// initialize all fields so that JSON serializion of output looks pretty (see client/holds.go)
+	// however, listZFSHoldsAndBookmarksImplFS shouldn't rely on it
+	out := &ListHoldsAndBookmarksOutput{
+		StepBookmarks:              make([]*ListHoldsAndBookmarksOutputBookmark, 0),
+		StepHolds:                  make([]*ListHoldsAndBookmarksOutputHold, 0),
+		ReplicationCursorBookmarks: make([]*ListHoldsAndBookmarksOutputBookmark, 0),
+		V1ReplicationCursors:       make([]*ListHoldsAndBookmarksOutputBookmarkV1ReplicationCursor, 0),
+		LastReceivedHolds:          make([]*ListHoldsAndBookmarksOutputHold, 0),
+	}
+
+	fss, err := zfs.ZFSListMapping(ctx, fsfilter)
+	if err != nil {
+		return nil, errors.Wrap(err, "list filesystems")
+	}
+
+	for _, fs := range fss {
+		err := listZFSHoldsAndBookmarksImplFS(ctx, out, fs)
+		if err != nil {
+			return nil, errors.Wrapf(err, "list holds and bookmarks on %q", fs.ToString())
+		}
+	}
+	return out, nil
+}
+
+func listZFSHoldsAndBookmarksImplFS(ctx context.Context, out *ListHoldsAndBookmarksOutput, fs *zfs.DatasetPath) error {
+	fsvs, err := zfs.ZFSListFilesystemVersions(fs, nil)
+	if err != nil {
+		return errors.Wrapf(err, "list filesystem versions of %q", fs)
+	}
+	for _, v := range fsvs {
+		switch v.Type {
+		case zfs.Bookmark:
+			listZFSHoldsAndBookmarksImplTryParseBookmark(ctx, out, fs, v)
+		case zfs.Snapshot:
+			holds, err := zfs.ZFSHolds(ctx, fs.ToString(), v.Name)
+			if err != nil {
+				return errors.Wrapf(err, "get holds of %q", v.ToAbsPath(fs))
+			}
+			for _, tag := range holds {
+				listZFSHoldsAndBookmarksImplSnapshotTryParseHold(ctx, out, fs, v, tag)
+			}
+		default:
+			continue
+		}
+	}
+	return nil
+}
+
+// pure function, err != nil always indicates parsing error
+func listZFSHoldsAndBookmarksImplTryParseBookmark(ctx context.Context, out *ListHoldsAndBookmarksOutput, fs *zfs.DatasetPath, v zfs.FilesystemVersion) {
+	var err error
+
+	if v.Type != zfs.Bookmark {
+		panic("impl error")
+	}
+
+	fullname := v.ToAbsPath(fs)
+
+	bm := &ListHoldsAndBookmarksOutputBookmark{
+		FS: fs.ToString(), Name: v.Name, v: v,
+	}
+	bm.Guid, bm.JobID, err = ParseStepBookmarkName(fullname)
+	if err == nil {
+		out.StepBookmarks = append(out.StepBookmarks, bm)
+		return
+	}
+
+	bm.Guid, bm.JobID, err = ParseReplicationCursorBookmarkName(fullname)
+	if err == nil {
+		out.ReplicationCursorBookmarks = append(out.ReplicationCursorBookmarks, bm)
+		return
+	} else if err == ErrV1ReplicationCursor {
+		v1rc := &ListHoldsAndBookmarksOutputBookmarkV1ReplicationCursor{
+			FS: fs.ToString(), Name: v.Name,
+		}
+		out.V1ReplicationCursors = append(out.V1ReplicationCursors, v1rc)
+		return
+	}
+}
+
+// pure function, err != nil always indicates parsing error
+func listZFSHoldsAndBookmarksImplSnapshotTryParseHold(ctx context.Context, out *ListHoldsAndBookmarksOutput, fs *zfs.DatasetPath, v zfs.FilesystemVersion, holdTag string) {
+	var err error
+
+	if v.Type != zfs.Snapshot {
+		panic("impl error")
+	}
+
+	hold := &ListHoldsAndBookmarksOutputHold{
+		FS:            fs.ToString(),
+		Snap:          v.Name,
+		SnapGuid:      v.Guid,
+		SnapCreateTXG: v.CreateTXG,
+		Tag:           holdTag,
+	}
+	hold.JobID, err = ParseStepHoldTag(holdTag)
+	if err == nil {
+		out.StepHolds = append(out.StepHolds, hold)
+		return
+	}
+
+	hold.JobID, err = ParseLastReceivedHoldTag(holdTag)
+	if err == nil {
+		out.LastReceivedHolds = append(out.LastReceivedHolds, hold)
+		return
+	}
+
+}

endpoint/endpoint_zfs_helpers.go

@@ -0,0 +1,109 @@
+package endpoint
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+	"strconv"
+
+	"github.com/pkg/errors"
+
+	"github.com/zrepl/zrepl/zfs"
+)
+
+// returns the short name (no fs# prefix)
+func makeJobAndGuidBookmarkName(prefix string, fs string, guid uint64, jobid string) (string, error) {
+	bmname := fmt.Sprintf(prefix+"_G_%016x_J_%s", guid, jobid)
+	if err := zfs.EntityNamecheck(fmt.Sprintf("%s#%s", fs, bmname), zfs.EntityTypeBookmark); err != nil {
+		return "", err
+	}
+	return bmname, nil
+}
+
+var jobAndGuidBookmarkRE = regexp.MustCompile(`(.+)_G_([0-9a-f]{16})_J_(.+)$`)
+
+func parseJobAndGuidBookmarkName(fullname string, prefix string) (guid uint64, jobID JobID, _ error) {
+
+	if len(prefix) == 0 {
+		panic("prefix must not be empty")
+	}
+
+	if err := zfs.EntityNamecheck(fullname, zfs.EntityTypeBookmark); err != nil {
+		return 0, JobID{}, err
+	}
+
+	_, _, name, err := zfs.DecomposeVersionString(fullname)
+	if err != nil {
+		return 0, JobID{}, errors.Wrap(err, "decompose bookmark name")
+	}
+
+	match := jobAndGuidBookmarkRE.FindStringSubmatch(name)
+	if match == nil {
+		return 0, JobID{}, errors.Errorf("bookmark name does not match regex %q", jobAndGuidBookmarkRE.String())
+	}
+	if match[1] != prefix {
+		return 0, JobID{}, errors.Errorf("prefix component does not match: expected %q, got %q", prefix, match[1])
+	}
+
+	guid, err = strconv.ParseUint(match[2], 16, 64)
+	if err != nil {
+		return 0, JobID{}, errors.Wrapf(err, "parse guid component: %q", match[2])
+	}
+
+	jobID, err = MakeJobID(match[3])
+	if err != nil {
+		return 0, JobID{}, errors.Wrapf(err, "parse jobid component: %q", match[3])
+	}
+
+	return guid, jobID, nil
+}
+
+func destroyBookmarksOlderThan(ctx context.Context, fs string, mostRecent *zfs.ZFSSendArgVersion, jobID JobID, filter func(shortname string) (accept bool)) (destroyed []zfs.FilesystemVersion, err error) {
+	if filter == nil {
+		panic(filter)
+	}
+
+	fsp, err := zfs.NewDatasetPath(fs)
+	if err != nil {
+		return nil, errors.Wrap(err, "invalid filesystem path")
+	}
+
+	mostRecentProps, err := mostRecent.ValidateExistsAndGetCheckedProps(ctx, fs)
+	if err != nil {
+		return nil, errors.Wrap(err, "validate most recent version argument")
+	}
+
+	stepBookmarks, err := zfs.ZFSListFilesystemVersions(fsp, zfs.FilterFromClosure(
+		func(t zfs.VersionType, name string) (accept bool, err error) {
+			if t != zfs.Bookmark {
+				return false, nil
+			}
+			return filter(name), nil
+		}))
+	if err != nil {
+		return nil, errors.Wrap(err, "list bookmarks")
+	}
+
+	// cut off all bookmarks prior to mostRecent's CreateTXG
+	var destroy []zfs.FilesystemVersion
+	for _, v := range stepBookmarks {
+		if v.Type != zfs.Bookmark {
+			panic("implementation error")
+		}
+		if !filter(v.Name) {
+			panic("inconsistent filter result")
+		}
+		if v.CreateTXG < mostRecentProps.CreateTXG {
+			destroy = append(destroy, v)
+		}
+	}
+
+	// FIXME use batch destroy, must adopt code to handle bookmarks
+	for _, v := range destroy {
+		if err := zfs.ZFSDestroyIdempotent(v.ToAbsPath(fsp)); err != nil {
+			return nil, errors.Wrap(err, "destroy bookmark")
+		}
+	}
+
+	return destroy, nil
+}

endpoint/endpoint_zfs_helpers_test.go

@@ -0,0 +1,51 @@
+package endpoint
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseJobAndGuidBookmarkName(t *testing.T) {
+
+	type Case struct {
+		input     string
+		expectErr bool
+
+		guid  uint64
+		jobid string
+	}
+
+	cases := []Case{
+		{
+			`p1/sync#zrepl_CURSOR_G_932f3a7089080ce2_J_push with legitimate name`,
+			false, 0x932f3a7089080ce2, "push with legitimate name",
+		},
+		{
+			input:     `p1/sync#zrepl_CURSOR_G_932f3a7089_J_push with legitimate name`,
+			expectErr: true,
+		},
+		{
+			input:     `p1/sync#zrepl_CURSOR_G_932f3a7089080ce2_J_push with il\tlegitimate name`,
+			expectErr: true,
+		},
+		{
+			input:     `p1/sync#otherprefix_G_932f3a7089080ce2_J_push with legitimate name`,
+			expectErr: true,
+		},
+	}
+
+	for i := range cases {
+		t.Run(cases[i].input, func(t *testing.T) {
+			guid, jobid, err := parseJobAndGuidBookmarkName(cases[i].input, replicationCursorBookmarkNamePrefix)
+			if cases[i].expectErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, cases[i].guid, guid)
+				assert.Equal(t, MustMakeJobID(cases[i].jobid), jobid)
+			}
+		})
+	}
+
+}

endpoint/jobid.go

@@ -0,0 +1,78 @@
+package endpoint
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/pkg/errors"
+
+	"github.com/zrepl/zrepl/zfs"
+)
+
+// An instance of this type returned by MakeJobID guarantees
+// that that instance's JobID.String() can be used in a ZFS dataset name and hold tag.
+type JobID struct {
+	jid string
+}
+
+func MakeJobID(s string) (JobID, error) {
+	if len(s) == 0 {
+		return JobID{}, fmt.Errorf("must not be empty string")
+	}
+
+	if err := zfs.ComponentNamecheck(s); err != nil {
+		return JobID{}, errors.Wrap(err, "muse be usable as a dataset path component")
+	}
+
+	if _, err := stepBookmarkNameImpl("pool/ds", 0xface601d, s); err != nil {
+		// note that this might still fail due to total maximum name length, but we can't enforce that
+		return JobID{}, errors.Wrap(err, "must be usable for a step bookmark")
+	}
+
+	if _, err := stepHoldTagImpl(s); err != nil {
+		return JobID{}, errors.Wrap(err, "must be usable for a step hold tag")
+	}
+
+	if _, err := lastReceivedHoldImpl(s); err != nil {
+		return JobID{}, errors.Wrap(err, "must be usabel as a last-recieved-hold tag")
+	}
+
+	// FIXME replication cursor bookmark name
+
+	_, err := zfs.NewDatasetPath(s)
+	if err != nil {
+		return JobID{}, fmt.Errorf("must be usable in a ZFS dataset path: %s", err)
+	}
+
+	return JobID{s}, nil
+}
+
+func MustMakeJobID(s string) JobID {
+	jid, err := MakeJobID(s)
+	if err != nil {
+		panic(err)
+	}
+	return jid
+}
+
+func (j JobID) expectInitialized() {
+	if j.jid == "" {
+		panic("use of unitialized JobID")
+	}
+}
+
+func (j JobID) String() string {
+	j.expectInitialized()
+	return j.jid
+}
+
+var _ json.Marshaler = JobID{}
+var _ json.Unmarshaler = (*JobID)(nil)
+
+func (j JobID) MarshalJSON() ([]byte, error) { return json.Marshal(j.jid) }
+
+func (j *JobID) UnmarshalJSON(b []byte) error {
+	return json.Unmarshal(b, &j.jid)
+}
+
+func (j JobID) MustValidate() { j.expectInitialized() }

go.mod

@@ -21,32 +21,17 @@ require (
 	github.com/onsi/gomega v1.7.0 // indirect
 	github.com/pkg/errors v0.8.1
 	github.com/pkg/profile v1.2.1
-	github.com/problame/go-netssh v0.0.0-20191026123024-f34099f4f6b1
+	github.com/problame/go-netssh v0.0.0-20191209123953-18d8aa6923c7
 	github.com/prometheus/client_golang v1.2.1
 	github.com/sergi/go-diff v1.0.1-0.20180205163309-da645544ed44 // go1.12 thinks it needs this
 	github.com/spf13/cobra v0.0.2
-	github.com/spf13/pflag v1.0.3
+	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.4.0
 	github.com/yudai/gojsondiff v0.0.0-20170107030110-7b1b7adf999d
 	github.com/yudai/golcs v0.0.0-20170316035057-ecda9a501e82 // go1.12 thinks it needs this
-	github.com/zrepl/yaml-config v0.0.0-20190928121844-af7ca3f8448f
+	github.com/zrepl/yaml-config v0.0.0-20191220194647-cbb6b0cf4bdd
 	golang.org/x/net v0.0.0-20190613194153-d28f0bde5980
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58
-	golang.org/x/sys v0.0.0-20191010194322-b09406accb47
+	golang.org/x/sys v0.0.0-20191026070338-33540a1f6037
 	google.golang.org/grpc v1.17.0
 )
-
-// invalid dates in transitive dependencies (first validated in Go 1.13, didn't fail in earlier Go versions)
-replace (
-	github.com/go-critic/go-critic v0.0.0-20181204210945-1df300866540 => github.com/go-critic/go-critic v0.3.5-0.20190526074819-1df300866540
-	github.com/go-critic/go-critic v0.0.0-20181204210945-ee9bf5809ead => github.com/go-critic/go-critic v0.3.5-0.20190210220443-ee9bf5809ead
-	github.com/golangci/errcheck v0.0.0-20181003203344-ef45e06d44b6 => github.com/golangci/errcheck v0.0.0-20181223084120-ef45e06d44b6
-	github.com/golangci/go-tools v0.0.0-20180109140146-35a9f45a5db0 => github.com/golangci/go-tools v0.0.0-20190124090046-35a9f45a5db0
-	github.com/golangci/go-tools v0.0.0-20180109140146-af6baa5dc196 => github.com/golangci/go-tools v0.0.0-20190318060251-af6baa5dc196
-	github.com/golangci/gofmt v0.0.0-20181105071733-0b8337e80d98 => github.com/golangci/gofmt v0.0.0-20181222123516-0b8337e80d98
-	github.com/golangci/gosec v0.0.0-20180901114220-66fb7fc33547 => github.com/golangci/gosec v0.0.0-20190211064107-66fb7fc33547
-	github.com/golangci/ineffassign v0.0.0-20180808204949-42439a7714cc => github.com/golangci/ineffassign v0.0.0-20190609212857-42439a7714cc
-	github.com/golangci/lint-1 v0.0.0-20180610141402-ee948d087217 => github.com/golangci/lint-1 v0.0.0-20190420132249-ee948d087217
-	golang.org/x/tools v0.0.0-20190125232054-379209517ffe => golang.org/x/tools v0.0.0-20190205201329-379209517ffe
-	mvdan.cc/unparam v0.0.0-20190124213536-fbb59629db34 => mvdan.cc/unparam v0.0.0-20190209190245-fbb59629db34
-)

go.sum

@@ -202,6 +202,8 @@ github.com/problame/go-netssh v0.0.0-20190110232351-09d6bc45d284 h1:GX8YFBfSL6Gl
 github.com/problame/go-netssh v0.0.0-20190110232351-09d6bc45d284/go.mod h1:XMR9fjP5/wMyFK0Ifk9ZHDFem4Rukm+ChvoYr2nxrgw=
 github.com/problame/go-netssh v0.0.0-20191026123024-f34099f4f6b1 h1:HH8yzlaZq/A8xdJaSj/eu32yFFySWAJMTmOQPAGwfYg=
 github.com/problame/go-netssh v0.0.0-20191026123024-f34099f4f6b1/go.mod h1:JRs3nyBjvOv/9YHC+Vlw9z1Jfzl5s5t0BNnTzmclj1c=
+github.com/problame/go-netssh v0.0.0-20191209123953-18d8aa6923c7 h1:Oik8tLrLhoMq4fduDRuNNOAQ+q0M0dXkjAYLUf4+mAc=
+github.com/problame/go-netssh v0.0.0-20191209123953-18d8aa6923c7/go.mod h1:Ba6RaFpK1+IHWs1wLZ6sCBuXkt4iAVLeOG5GinXHusM=
 github.com/prometheus/client_golang v0.0.0-20180410130117-e11c6ff8170b/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
 github.com/prometheus/client_golang v1.0.0/go.mod h1:db9x61etRT2tGnBNRi70OPL5FsnadC4Ky3P0J6CfImo=
@@ -251,6 +253,8 @@ github.com/spf13/jwalterweatherman v1.1.0/go.mod h1:aNWZUN0dPAAO/Ljvb5BEdw96iTZ0
 github.com/spf13/pflag v1.0.1/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
 github.com/spf13/pflag v1.0.3 h1:zPAT6CGy6wXeQ7NtTnaTerfKOsV6V6F8agHXFiazDkg=
 github.com/spf13/pflag v1.0.3/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/spf13/viper v1.0.2/go.mod h1:A8kyI5cUJhb8N+3pkfONlcEcZbueH6nhAm0Fq7SrnBM=
 github.com/spf13/viper v1.3.2/go.mod h1:ZiWeW+zYFKm7srdB9IoDzzZXaJaI5eL9QjNiN/DMA2s=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -277,6 +281,8 @@ github.com/yudai/pp v2.0.1+incompatible h1:Q4//iY4pNF6yPLZIigmvcl7k/bPgrcTPIFIcm
 github.com/yudai/pp v2.0.1+incompatible/go.mod h1:PuxR/8QJ7cyCkFp/aUDS+JY727OFEZkTdatxwunjIkc=
 github.com/zrepl/yaml-config v0.0.0-20190928121844-af7ca3f8448f h1:3MuiGfgMHCSwKUcsuI7ODbi50j+evTB7SsoOBMNC5Fk=
 github.com/zrepl/yaml-config v0.0.0-20190928121844-af7ca3f8448f/go.mod h1:JmNwisZzOvW4GfpfLvhZ+gtyKLsIiA+WC+wNKJGJaFg=
+github.com/zrepl/yaml-config v0.0.0-20191220194647-cbb6b0cf4bdd h1:SSo67WLS+99QESvbW8Meibz7zCrxshP71U9dH5KOCXM=
+github.com/zrepl/yaml-config v0.0.0-20191220194647-cbb6b0cf4bdd/go.mod h1:JmNwisZzOvW4GfpfLvhZ+gtyKLsIiA+WC+wNKJGJaFg=
 github.com/zrepl/zrepl v0.2.0/go.mod h1:M3Zv2IGSO8iYpUjsZD6ayZ2LHy7zyMfzet9XatKOrZ8=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
@@ -315,6 +321,8 @@ golang.org/x/sys v0.0.0-20190626150813-e07cf5db2756 h1:9nuHUbU8dRnRRfj9KjWUVrJeo
 golang.org/x/sys v0.0.0-20190626150813-e07cf5db2756/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191010194322-b09406accb47 h1:/XfQ9z7ib8eEJX2hdgFTZJ/ntt0swNk5oYBziWeTCvY=
 golang.org/x/sys v0.0.0-20191010194322-b09406accb47/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191026070338-33540a1f6037 h1:YyJpGZS1sBuBCzLAR1VEpK193GlqGZbnPFnPV/5Rsb4=
+golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.0.0-20170915090833-1cbadb444a80/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -333,6 +341,7 @@ golang.org/x/tools v0.0.0-20190521203540-521d6ed310dd/go.mod h1:RgjU9mgBXZiqYHBn
 golang.org/x/tools v0.0.0-20190524210228-3d17549cdc6b/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
 google.golang.org/appengine v1.1.0 h1:igQkv0AAhEIvTEpD5LIpAfav2eeVO9HBTjvKHVJPRSs=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
+google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8 h1:Nw54tB0rB7hY/N0NQvRW8DG4Yk3Q6T9cu9RcFQDu1tc=
 google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
 google.golang.org/genproto v0.0.0-20181202183823-bd91e49a0898 h1:yvw+zsSmSM02Z5H3ZdEV7B7Ql7eFrjQTnmByJvK+3J8=
 google.golang.org/genproto v0.0.0-20181202183823-bd91e49a0898/go.mod h1:7Ep/1NZk928CDR8SjdVbjWNpdIf6nzjE3BTgJDr2Atg=

main.go

@@ -17,6 +17,7 @@ func init() {
 	cli.AddSubcommand(client.PprofCmd)
 	cli.AddSubcommand(client.TestCmd)
 	cli.AddSubcommand(client.MigrateCmd)
+	cli.AddSubcommand(client.HoldsCmd)
 }
 
 func main() {

platformtest/harness/harness.go

@@ -4,11 +4,14 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"os"
 	"path/filepath"
+	"regexp"
 	"time"
 
 	"github.com/fatih/color"
 	"github.com/pkg/errors"
+
 	"github.com/zrepl/zrepl/config"
 	"github.com/zrepl/zrepl/daemon/logging"
 	"github.com/zrepl/zrepl/logger"
@@ -16,19 +19,38 @@ import (
 	"github.com/zrepl/zrepl/platformtest/tests"
 )
 
-func main() {
+var bold = color.New(color.Bold)
+var boldRed = color.New(color.Bold, color.FgHiRed)
+var boldGreen = color.New(color.Bold, color.FgHiGreen)
 
-	var args struct {
-		createArgs            platformtest.ZpoolCreateArgs
-		stopAndKeepPoolOnFail bool
+var args struct {
+	createArgs            platformtest.ZpoolCreateArgs
+	stopAndKeepPoolOnFail bool
+
+	run   string
+	runRE *regexp.Regexp
+}
+
+func main() {
+	if err := doMain(); err != nil {
+		os.Exit(1)
 	}
+}
+
+var exitWithErr = fmt.Errorf("exit with error")
+
+func doMain() error {
+
 	flag.StringVar(&args.createArgs.PoolName, "poolname", "", "")
 	flag.StringVar(&args.createArgs.ImagePath, "imagepath", "", "")
-	flag.Int64Var(&args.createArgs.ImageSize, "imagesize", 100*(1<<20), "")
-	flag.StringVar(&args.createArgs.Mountpoint, "mountpoint", "none", "")
+	flag.Int64Var(&args.createArgs.ImageSize, "imagesize", 200*(1<<20), "")
+	flag.StringVar(&args.createArgs.Mountpoint, "mountpoint", "", "")
 	flag.BoolVar(&args.stopAndKeepPoolOnFail, "failure.stop-and-keep-pool", false, "if a test case fails, stop test execution and keep pool as it was when the test failed")
+	flag.StringVar(&args.run, "run", "", "")
 	flag.Parse()
 
+	args.runRE = regexp.MustCompile(args.run)
+
 	outlets := logger.NewOutlets()
 	outlet, level, err := logging.ParseOutlet(config.LoggingOutletEnum{Ret: &config.StdoutLoggingOutlet{
 		LoggingOutletCommon: config.LoggingOutletCommon{
@@ -49,48 +71,132 @@ func main() {
 	ctx := platformtest.WithLogger(context.Background(), logger)
 	ex := platformtest.NewEx(logger)
 
-	bold := color.New(color.Bold)
-	boldRed := color.New(color.Bold, color.FgHiRed)
-	boldGreen := color.New(color.Bold, color.FgHiGreen)
+	type invocation struct {
+		runFunc tests.Case
+		result  *testCaseResult
+	}
+
+	invocations := make([]*invocation, 0, len(tests.Cases))
 	for _, c := range tests.Cases {
-		// ATTENTION future parallelism must pass c by value into closure!
-		err := func() (err error) {
-			var oErr = &err
-			bold.Printf("BEGIN TEST CASE %s\n", c)
-			pool, err := platformtest.CreateOrReplaceZpool(ctx, ex, args.createArgs)
-			if err != nil {
-				return errors.Wrap(err, "create test pool")
-			}
-			defer func() {
-				if err := recover(); err != nil {
-					*oErr = errors.Errorf("panic while running test: %v", err) // shadow
-					if args.stopAndKeepPoolOnFail {
-						return
-					}
-					// fallthrough
-				}
-				if err := pool.Destroy(ctx, ex); err != nil {
-					fmt.Printf("error destroying test pool: %s", err)
-				}
-			}()
-			ctx := &platformtest.Context{
-				Context:     ctx,
-				RootDataset: filepath.Join(pool.Name(), "rootds"),
-			}
-			c(ctx)
-			return nil
-		}()
-		if err != nil {
-			boldRed.Printf("TEST CASE FAILED WITH ERROR:\n")
-			fmt.Printf("%+v\n", err) // print with stack trace
-			if args.stopAndKeepPoolOnFail {
-				bold.Printf("STOPPING TEST RUN AT FAILING TEST PER USER REQUEST\n")
-				return
-			}
-		} else {
-			boldGreen.Printf("DONE  TEST CASE %s\n", c)
+		if args.runRE.MatchString(c.String()) {
+			invocations = append(invocations, &invocation{runFunc: c})
 		}
+	}
+
+	for _, inv := range invocations {
+
+		bold.Printf("BEGIN TEST CASE %s\n", inv.runFunc.String())
+
+		pool, err := platformtest.CreateOrReplaceZpool(ctx, ex, args.createArgs)
+		if err != nil {
+			panic(errors.Wrap(err, "create test pool"))
+		}
+
+		ctx := &platformtest.Context{
+			Context:     ctx,
+			RootDataset: filepath.Join(pool.Name(), "rootds"),
+		}
+
+		res := runTestCase(ctx, ex, inv.runFunc)
+		inv.result = res
+		if res.failed {
+			fmt.Printf("%+v\n", res.failedStack) // print with stack trace
+		}
+
+		if res.failed && args.stopAndKeepPoolOnFail {
+			boldRed.Printf("STOPPING TEST RUN AT FAILING TEST PER USER REQUEST\n")
+			return exitWithErr
+		}
+
+		if err := pool.Destroy(ctx, ex); err != nil {
+			panic(fmt.Sprintf("error destroying test pool: %s", err))
+		}
+
+		if res.failed {
+			boldRed.Printf("TEST FAILED\n")
+		} else if res.skipped {
+			bold.Printf("TEST SKIPPED\n")
+		} else if res.succeeded {
+			boldGreen.Printf("TEST PASSED\n")
+		} else {
+			panic("unreachable")
+		}
+
 		fmt.Println()
 	}
 
+	var summary struct {
+		succ, fail, skip []*invocation
+	}
+	for _, inv := range invocations {
+		var bucket *[]*invocation
+		if inv.result.failed {
+			bucket = &summary.fail
+		} else if inv.result.skipped {
+			bucket = &summary.skip
+		} else if inv.result.succeeded {
+			bucket = &summary.succ
+		} else {
+			panic("unreachable")
+		}
+		*bucket = append(*bucket, inv)
+	}
+	printBucket := func(bucketName string, c *color.Color, bucket []*invocation) {
+		c.Printf("%s:", bucketName)
+		if len(bucket) == 0 {
+			fmt.Printf(" []\n")
+			return
+		}
+		fmt.Printf("\n")
+		for _, inv := range bucket {
+			fmt.Printf("  %s\n", inv.runFunc.String())
+		}
+	}
+	printBucket("PASSING TESTS", boldGreen, summary.succ)
+	printBucket("SKIPPED TESTS", bold, summary.skip)
+	printBucket("FAILED TESTS", boldRed, summary.fail)
+
+	if len(summary.fail) > 0 {
+		return errors.New("at least one test failed")
+	}
+	return nil
+}
+
+type testCaseResult struct {
+	// oneof
+	failed, skipped, succeeded bool
+
+	failedStack error // has stack inside, valid if failed=true
+}
+
+func runTestCase(ctx *platformtest.Context, ex platformtest.Execer, c tests.Case) *testCaseResult {
+
+	// run case
+	var paniced = false
+	var panicValue interface{} = nil
+	var panicStack error
+	func() {
+		defer func() {
+			if item := recover(); item != nil {
+				panicValue = item
+				paniced = true
+				panicStack = errors.Errorf("panic while running test: %v", panicValue)
+			}
+		}()
+		c(ctx)
+	}()
+
+	if paniced {
+		switch panicValue {
+		case platformtest.SkipNowSentinel:
+			return &testCaseResult{skipped: true}
+		case platformtest.FailNowSentinel:
+			return &testCaseResult{failed: true, failedStack: panicStack}
+		default:
+			return &testCaseResult{failed: true, failedStack: panicStack}
+		}
+	} else {
+		return &testCaseResult{succeeded: true}
+	}
+
 }

platformtest/platformtest.go

@@ -2,6 +2,7 @@ package platformtest
 
 import (
 	"context"
+	"fmt"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -12,13 +13,26 @@ type Context struct {
 	RootDataset string
 }
 
+var FailNowSentinel = fmt.Errorf("platformtest: FailNow called on context")
+
+var SkipNowSentinel = fmt.Errorf("platformtest: SkipNow called on context")
+
 var _ assert.TestingT = (*Context)(nil)
 var _ require.TestingT = (*Context)(nil)
 
+func (c *Context) Logf(format string, args ...interface{}) {
+	msg := fmt.Sprintf(format, args...)
+	GetLog(c).Info(msg)
+}
+
 func (c *Context) Errorf(format string, args ...interface{}) {
 	GetLog(c).Printf(format, args...)
 }
 
 func (c *Context) FailNow() {
-	panic(nil)
+	panic(FailNowSentinel)
+}
+
+func (c *Context) SkipNow() {
+	panic(SkipNowSentinel)
 }

platformtest/platformtest_ops.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"os/exec"
 	"strings"
@@ -46,8 +47,9 @@ func (o *DestroyRootOp) Run(ctx context.Context, e Execer) error {
 }
 
 type FSOp struct {
-	Op   Op
-	Path string
+	Op        Op
+	Path      string
+	Encrypted bool // only for Op=Add
 }
 
 func (o *FSOp) Run(ctx context.Context, e Execer) error {
@@ -57,7 +59,22 @@ func (o *FSOp) Run(ctx context.Context, e Execer) error {
 	case AssertNotExists:
 		return e.RunExpectFailureNoOutput(ctx, "zfs", "get", "-H", "name", o.Path)
 	case Add:
-		return e.RunExpectSuccessNoOutput(ctx, "zfs", "create", o.Path)
+		opts := []string{"create"}
+		if o.Encrypted {
+			const passphraseFilePath = "/tmp/zreplplatformtest.encryption.passphrase"
+			const passphrase = "foobar2342"
+			err := ioutil.WriteFile(passphraseFilePath, []byte(passphrase), 0600)
+			if err != nil {
+				panic(err)
+			}
+			opts = append(opts,
+				"-o", "encryption=on",
+				"-o", "keylocation=file:///"+passphraseFilePath,
+				"-o", "keyformat=passphrase",
+			)
+		}
+		opts = append(opts, o.Path)
+		return e.RunExpectSuccessNoOutput(ctx, "zfs", opts...)
 	case Del:
 		return e.RunExpectSuccessNoOutput(ctx, "zfs", "destroy", o.Path)
 	default:
@@ -249,7 +266,25 @@ nextLine:
 		if strings.ContainsAny(comps.Text(), "@") {
 			stmts = append(stmts, &SnapOp{Op: op, Path: fmt.Sprintf("%s/%s", rootds, comps.Text())})
 		} else {
-			stmts = append(stmts, &FSOp{Op: op, Path: fmt.Sprintf("%s/%s", rootds, comps.Text())})
+			// FS
+			fs := comps.Text()
+			var encrypted bool = false
+			if op == Add {
+				if comps.Scan() {
+					t := comps.Text()
+					switch t {
+					case "encrypted":
+						encrypted = true
+					default:
+						panic(fmt.Sprintf("unexpected token %q", t))
+					}
+				}
+			}
+			stmts = append(stmts, &FSOp{
+				Op:        op,
+				Path:      fmt.Sprintf("%s/%s", rootds, fs),
+				Encrypted: encrypted,
+			})
 		}
 
 		if comps.Scan() {

platformtest/platformtest_zpool.go

@@ -2,10 +2,12 @@ package platformtest
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"path/filepath"
 
 	"github.com/pkg/errors"
+
 	"github.com/zrepl/zrepl/zfs"
 )
 
@@ -28,8 +30,8 @@ func (a ZpoolCreateArgs) Validate() error {
 	if a.ImageSize < minImageSize {
 		return errors.Errorf("ImageSize must be > %v, got %v", minImageSize, a.ImageSize)
 	}
-	if a.Mountpoint != "none" {
-		return errors.Errorf("Mountpoint must be \"none\"")
+	if a.Mountpoint == "" || a.Mountpoint[0] != '/' {
+		return errors.Errorf("Mountpoint must be an absolute path to a directory")
 	}
 	if a.PoolName == "" {
 		return errors.Errorf("PoolName must not be emtpy")
@@ -68,7 +70,10 @@ func CreateOrReplaceZpool(ctx context.Context, e Execer, args ZpoolCreateArgs) (
 	image.Close()
 
 	// create the pool
-	err = e.RunExpectSuccessNoOutput(ctx, "zpool", "create", "-f", "-O", "mountpoint=none", args.PoolName, args.ImagePath)
+	err = e.RunExpectSuccessNoOutput(ctx, "zpool", "create", "-f",
+		"-O", fmt.Sprintf("mountpoint=%s", args.Mountpoint),
+		args.PoolName, args.ImagePath,
+	)
 	if err != nil {
 		return nil, errors.Wrap(err, "zpool create")
 	}

platformtest/tests/batchRelease.go

@@ -0,0 +1,154 @@
+package tests
+
+import (
+	"fmt"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+type rollupReleaseExpectTags struct {
+	Snap  string
+	Holds map[string]bool
+}
+
+func rollupReleaseTest(ctx *platformtest.Context, cb func(fs string) []rollupReleaseExpectTags) {
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+	DESTROYROOT
+	CREATEROOT
+	+  "foo bar"
+	+  "foo bar@1"
+	+  "foo bar@2"
+	+  "foo bar@3"
+	+  "foo bar@4"
+	+  "foo bar@5"
+	+  "foo bar@6"
+	R  zfs hold zrepl_platformtest   "${ROOTDS}/foo bar@1"
+	R  zfs hold zrepl_platformtest_2 "${ROOTDS}/foo bar@2"
+	R  zfs hold zrepl_platformtest   "${ROOTDS}/foo bar@3"
+	R  zfs hold zrepl_platformtest   "${ROOTDS}/foo bar@5"
+	R  zfs hold zrepl_platformtest   "${ROOTDS}/foo bar@6"
+	R  zfs bookmark "${ROOTDS}/foo bar@5" "${ROOTDS}/foo bar#5"
+`)
+
+	fs := fmt.Sprintf("%s/foo bar", ctx.RootDataset)
+
+	expTags := cb(fs)
+
+	for _, exp := range expTags {
+		holds, err := zfs.ZFSHolds(ctx, fs, exp.Snap)
+		if err != nil {
+			panic(err)
+		}
+		for _, h := range holds {
+			if e, ok := exp.Holds[h]; !ok || !e {
+				panic(fmt.Sprintf("tag %q on snap %q not expected", h, exp.Snap))
+			}
+		}
+	}
+
+}
+
+func RollupReleaseIncluding(ctx *platformtest.Context) {
+	rollupReleaseTest(ctx, func(fs string) []rollupReleaseExpectTags {
+		guid5, err := zfs.ZFSGetGUID(fs, "@5")
+		require.NoError(ctx, err)
+
+		err = zfs.ZFSReleaseAllOlderAndIncludingGUID(ctx, fs, guid5, "zrepl_platformtest")
+		require.NoError(ctx, err)
+
+		return []rollupReleaseExpectTags{
+			{"1", map[string]bool{}},
+			{"2", map[string]bool{"zrepl_platformtest_2": true}},
+			{"3", map[string]bool{}},
+			{"4", map[string]bool{}},
+			{"5", map[string]bool{}},
+			{"6", map[string]bool{"zrepl_platformtest": true}},
+		}
+	})
+}
+
+func RollupReleaseExcluding(ctx *platformtest.Context) {
+	rollupReleaseTest(ctx, func(fs string) []rollupReleaseExpectTags {
+		guid5, err := zfs.ZFSGetGUID(fs, "@5")
+		require.NoError(ctx, err)
+
+		err = zfs.ZFSReleaseAllOlderThanGUID(ctx, fs, guid5, "zrepl_platformtest")
+		require.NoError(ctx, err)
+
+		return []rollupReleaseExpectTags{
+			{"1", map[string]bool{}},
+			{"2", map[string]bool{"zrepl_platformtest_2": true}},
+			{"3", map[string]bool{}},
+			{"4", map[string]bool{}},
+			{"5", map[string]bool{"zrepl_platformtest": true}},
+			{"6", map[string]bool{"zrepl_platformtest": true}},
+		}
+	})
+}
+
+func RollupReleaseMostRecentIsBookmarkWithoutSnapshot(ctx *platformtest.Context) {
+	rollupReleaseTest(ctx, func(fs string) []rollupReleaseExpectTags {
+		guid5, err := zfs.ZFSGetGUID(fs, "#5")
+		require.NoError(ctx, err)
+
+		err = zfs.ZFSRelease(ctx, "zrepl_platformtest", fs+"@5")
+		require.NoError(ctx, err)
+
+		err = zfs.ZFSDestroy(fs + "@5")
+		require.NoError(ctx, err)
+
+		err = zfs.ZFSReleaseAllOlderAndIncludingGUID(ctx, fs, guid5, "zrepl_platformtest")
+		require.NoError(ctx, err)
+
+		return []rollupReleaseExpectTags{
+			{"1", map[string]bool{}},
+			{"2", map[string]bool{"zrepl_platformtest_2": true}},
+			{"3", map[string]bool{}},
+			{"4", map[string]bool{}},
+			// {"5", map[string]bool{}}, doesn't exist
+			{"6", map[string]bool{"zrepl_platformtest": true}},
+		}
+	})
+}
+
+func RollupReleaseMostRecentIsBookmarkAndSnapshotStillExists(ctx *platformtest.Context) {
+	rollupReleaseTest(ctx, func(fs string) []rollupReleaseExpectTags {
+		guid5, err := zfs.ZFSGetGUID(fs, "#5")
+		require.NoError(ctx, err)
+
+		err = zfs.ZFSReleaseAllOlderAndIncludingGUID(ctx, fs, guid5, "zrepl_platformtest")
+		require.NoError(ctx, err)
+
+		return []rollupReleaseExpectTags{
+			{"1", map[string]bool{}},
+			{"2", map[string]bool{"zrepl_platformtest_2": true}},
+			{"3", map[string]bool{}},
+			{"4", map[string]bool{}},
+			{"5", map[string]bool{}},
+			{"6", map[string]bool{"zrepl_platformtest": true}},
+		}
+	})
+}
+
+func RollupReleaseMostRecentDoesntExist(ctx *platformtest.Context) {
+	rollupReleaseTest(ctx, func(fs string) []rollupReleaseExpectTags {
+
+		const nonexistentGuid = 0 // let's take our chances...
+		err := zfs.ZFSReleaseAllOlderAndIncludingGUID(ctx, fs, nonexistentGuid, "zrepl_platformtest")
+		require.Error(ctx, err)
+		require.Contains(ctx, err.Error(), "cannot find snapshot or bookmark with guid 0")
+
+		return []rollupReleaseExpectTags{
+			{"1", map[string]bool{"zrepl_platformtest": true}},
+			{"2", map[string]bool{"zrepl_platformtest_2": true}},
+			{"3", map[string]bool{"zrepl_platformtest": true}},
+			{"4", map[string]bool{"zrepl_platformtest": true}},
+			{"5", map[string]bool{"zrepl_platformtest": true}},
+			{"6", map[string]bool{"zrepl_platformtest": true}},
+		}
+	})
+}

platformtest/tests/helpers.go

@@ -0,0 +1,139 @@
+package tests
+
+import (
+	"io"
+	"math/rand"
+	"os"
+	"path"
+	"strings"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/util/limitio"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+func sendArgVersion(fs, relName string) zfs.ZFSSendArgVersion {
+	guid, err := zfs.ZFSGetGUID(fs, relName)
+	if err != nil {
+		panic(err)
+	}
+	return zfs.ZFSSendArgVersion{
+		RelName: relName,
+		GUID:    guid,
+	}
+}
+
+func mustDatasetPath(fs string) *zfs.DatasetPath {
+	p, err := zfs.NewDatasetPath(fs)
+	if err != nil {
+		panic(err)
+	}
+	return p
+}
+
+func mustSnapshot(snap string) {
+	if err := zfs.EntityNamecheck(snap, zfs.EntityTypeSnapshot); err != nil {
+		panic(err)
+	}
+	comps := strings.Split(snap, "@")
+	if len(comps) != 2 {
+		panic(comps)
+	}
+	err := zfs.ZFSSnapshot(mustDatasetPath(comps[0]), comps[1], false)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func mustGetProps(entity string) zfs.ZFSPropCreateTxgAndGuidProps {
+	props, err := zfs.ZFSGetCreateTXGAndGuid(entity)
+	check(err)
+	return props
+}
+
+func check(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+var dummyDataRand = rand.New(rand.NewSource(99))
+
+func writeDummyData(path string, numBytes int64) {
+	r := io.LimitReader(dummyDataRand, numBytes)
+	d, err := os.OpenFile(path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0666)
+	check(err)
+	defer d.Close()
+	_, err = io.Copy(d, r)
+	check(err)
+}
+
+type dummySnapshotSituation struct {
+	sendFS       string
+	dummyDataLen int64
+	snapA        *zfs.ZFSSendArgVersion
+	snapB        *zfs.ZFSSendArgVersion
+}
+
+type resumeSituation struct {
+	sendArgs         zfs.ZFSSendArgs
+	recvOpts         zfs.RecvOptions
+	sendErr, recvErr error
+	recvErrDecoded   *zfs.RecvFailedWithResumeTokenErr
+}
+
+func makeDummyDataSnapshots(ctx *platformtest.Context, sendFS string) (situation dummySnapshotSituation) {
+
+	situation.sendFS = sendFS
+	sendFSMount, err := zfs.ZFSGetMountpoint(sendFS)
+	require.NoError(ctx, err)
+	require.True(ctx, sendFSMount.Mounted)
+
+	const dummyLen = int64(10 * (1 << 20))
+	situation.dummyDataLen = dummyLen
+
+	writeDummyData(path.Join(sendFSMount.Mountpoint, "dummy_data"), dummyLen)
+	mustSnapshot(sendFS + "@a snapshot")
+	snapA := sendArgVersion(sendFS, "@a snapshot")
+	situation.snapA = &snapA
+
+	writeDummyData(path.Join(sendFSMount.Mountpoint, "dummy_data"), dummyLen)
+	mustSnapshot(sendFS + "@b snapshot")
+	snapB := sendArgVersion(sendFS, "@b snapshot")
+	situation.snapB = &snapB
+
+	return situation
+}
+
+func makeResumeSituation(ctx *platformtest.Context, src dummySnapshotSituation, recvFS string, sendArgs zfs.ZFSSendArgs, recvOptions zfs.RecvOptions) *resumeSituation {
+
+	situation := &resumeSituation{}
+
+	situation.sendArgs = sendArgs
+	situation.recvOpts = recvOptions
+	require.True(ctx, recvOptions.SavePartialRecvState, "this method would be pointeless otherwise")
+	require.Equal(ctx, sendArgs.FS, src.sendFS)
+
+	copier, err := zfs.ZFSSend(ctx, sendArgs)
+	situation.sendErr = err
+	if err != nil {
+		return situation
+	}
+
+	limitedCopier := zfs.NewReadCloserCopier(limitio.ReadCloser(copier, src.dummyDataLen/2))
+	defer limitedCopier.Close()
+
+	require.NotNil(ctx, sendArgs.To)
+	err = zfs.ZFSRecv(ctx, recvFS, sendArgs.To, limitedCopier, recvOptions)
+	situation.recvErr = err
+	ctx.Logf("zfs recv exit with %T %s", err, err)
+
+	require.NotNil(ctx, err)
+	resumeErr, ok := err.(*zfs.RecvFailedWithResumeTokenErr)
+	require.True(ctx, ok)
+	situation.recvErrDecoded = resumeErr
+
+	return situation
+}

platformtest/tests/idempotentBookmark.go

@@ -0,0 +1,59 @@
+package tests
+
+import (
+	"fmt"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+func IdempotentBookmark(ctx *platformtest.Context) {
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+		DESTROYROOT
+		CREATEROOT
+		+  "foo bar"
+		+  "foo bar@a snap"
+		+  "foo bar@another snap"
+	`)
+
+	fs := fmt.Sprintf("%s/foo bar", ctx.RootDataset)
+
+	asnap := sendArgVersion(fs, "@a snap")
+	anotherSnap := sendArgVersion(fs, "@another snap")
+
+	err := zfs.ZFSBookmark(fs, asnap, "a bookmark")
+	if err != nil {
+		panic(err)
+	}
+
+	// do it again, should be idempotent
+	err = zfs.ZFSBookmark(fs, asnap, "a bookmark")
+	if err != nil {
+		panic(err)
+	}
+
+	// should fail for another snapshot
+	err = zfs.ZFSBookmark(fs, anotherSnap, "a bookmark")
+	if err == nil {
+		panic(err)
+	}
+	if _, ok := err.(*zfs.BookmarkExists); !ok {
+		panic(fmt.Sprintf("has type %T", err))
+	}
+
+	// destroy the snapshot
+	if err := zfs.ZFSDestroy(fmt.Sprintf("%s@a snap", fs)); err != nil {
+		panic(err)
+	}
+
+	// do it again, should fail with special error type
+	err = zfs.ZFSBookmark(fs, asnap, "a bookmark")
+	if err == nil {
+		panic(err)
+	}
+	if _, ok := err.(*zfs.DatasetDoesNotExist); !ok {
+		panic(fmt.Sprintf("has type %T", err))
+	}
+
+}

platformtest/tests/idempotentDestroy.go

@@ -0,0 +1,75 @@
+package tests
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+func IdempotentDestroy(ctx *platformtest.Context) {
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+		DESTROYROOT
+		CREATEROOT
+		+  "foo bar"
+		+  "foo bar@a snap"
+	`)
+
+	fs := fmt.Sprintf("%s/foo bar", ctx.RootDataset)
+	asnap := sendArgVersion(fs, "@a snap")
+	err := zfs.ZFSBookmark(fs, asnap, "a bookmark")
+	if err != nil {
+		panic(err)
+	}
+
+	type testCase struct {
+		description, path string
+	}
+
+	cases := []testCase{
+		{"snapshot", fmt.Sprintf("%s@a snap", fs)},
+		{"bookmark", fmt.Sprintf("%s#a bookmark", fs)},
+		{"filesystem", fs},
+	}
+
+	for i := range cases {
+		func() {
+			c := cases[i]
+
+			log.Printf("SUBBEGIN testing idempotent destroy %q for path %q", c.description, c.path)
+
+			log.Println("destroy existing")
+			err = zfs.ZFSDestroy(c.path)
+			if err != nil {
+				panic(err)
+			}
+			log.Println("destroy again, non-idempotently, must error")
+			err = zfs.ZFSDestroy(c.path)
+			if _, ok := err.(*zfs.DatasetDoesNotExist); !ok {
+				panic(fmt.Sprintf("%T: %s", err, err))
+			}
+			log.Println("destroy again, idempotently, must not error")
+			err = zfs.ZFSDestroyIdempotent(c.path)
+			if err != nil {
+				panic(err)
+			}
+
+			log.Println("SUBEND")
+
+		}()
+	}
+
+	// also test idempotent destroy for cases where the parent dataset does not exist
+	err = zfs.ZFSDestroyIdempotent(fmt.Sprintf("%s/not foo bar@nonexistent snapshot", ctx.RootDataset))
+	if err != nil {
+		panic(err)
+	}
+
+	err = zfs.ZFSDestroyIdempotent(fmt.Sprintf("%s/not foo bar#nonexistent bookmark", ctx.RootDataset))
+	if err != nil {
+		panic(err)
+	}
+
+}

platformtest/tests/idempotentHold.go

@@ -0,0 +1,47 @@
+package tests
+
+import (
+	"fmt"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+func IdempotentHold(ctx *platformtest.Context) {
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+		DESTROYROOT
+		CREATEROOT
+		+  "foo bar"
+		+  "foo bar@1"
+	`)
+	defer platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+		R zfs release zrepl_platformtest "${ROOTDS}/foo bar@1"
+		-  "foo bar@1"
+		-  "foo bar"
+	`)
+
+	fs := fmt.Sprintf("%s/foo bar", ctx.RootDataset)
+	v1 := sendArgVersion(fs, "@1")
+
+	tag := "zrepl_platformtest"
+	err := zfs.ZFSHold(ctx, fs, v1, tag)
+	if err != nil {
+		panic(err)
+	}
+
+	err = zfs.ZFSHold(ctx, fs, v1, tag)
+	if err != nil {
+		panic(err)
+	}
+
+	vnonexistent := zfs.ZFSSendArgVersion{
+		RelName: "@nonexistent",
+		GUID:    0xbadf00d,
+	}
+	err = zfs.ZFSHold(ctx, fs, vnonexistent, tag)
+	if err == nil {
+		panic("still expecting error for nonexistent snapshot")
+	}
+
+}

platformtest/tests/replicationCursor.go

@@ -3,6 +3,9 @@ package tests
 import (
 	"fmt"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/zrepl/zrepl/endpoint"
 	"github.com/zrepl/zrepl/platformtest"
 	"github.com/zrepl/zrepl/zfs"
 )
@@ -13,25 +16,35 @@ func ReplicationCursor(ctx *platformtest.Context) {
 		CREATEROOT
 		+  "foo bar"
 		+  "foo bar@1 with space"
+		R  zfs bookmark "${ROOTDS}/foo bar@1 with space" "${ROOTDS}/foo bar#1 with space"
+		+  "foo bar@2 with space"
+		R  zfs bookmark "${ROOTDS}/foo bar@1 with space" "${ROOTDS}/foo bar#2 with space"
+		+  "foo bar@3 with space"
+		R  zfs bookmark "${ROOTDS}/foo bar@1 with space" "${ROOTDS}/foo bar#3 with space"
 	`)
 
+	jobid := endpoint.MustMakeJobID("zreplplatformtest")
+
 	ds, err := zfs.NewDatasetPath(ctx.RootDataset + "/foo bar")
 	if err != nil {
 		panic(err)
 	}
-	guid, err := zfs.ZFSSetReplicationCursor(ds, "1 with space")
+
+	fs := ds.ToString()
+	snap := sendArgVersion(fs, "@1 with space")
+
+	destroyed, err := endpoint.MoveReplicationCursor(ctx, fs, &snap, jobid)
 	if err != nil {
 		panic(err)
 	}
-	snapProps, err := zfs.ZFSGetCreateTXGAndGuid(ds.ToString() + "@1 with space")
+	assert.Empty(ctx, destroyed)
+
+	snapProps, err := zfs.ZFSGetCreateTXGAndGuid(snap.FullPath(fs))
 	if err != nil {
 		panic(err)
 	}
-	if guid != snapProps.Guid {
-		panic(fmt.Sprintf("guids to not match: %v != %v", guid, snapProps.Guid))
-	}
 
-	bm, err := zfs.ZFSGetReplicationCursor(ds)
+	bm, err := endpoint.GetMostRecentReplicationCursorOfJob(ctx, fs, jobid)
 	if err != nil {
 		panic(err)
 	}
@@ -41,22 +54,15 @@ func ReplicationCursor(ctx *platformtest.Context) {
 	if bm.Guid != snapProps.Guid {
 		panic(fmt.Sprintf("guids do not match: %v != %v", bm.Guid, snapProps.Guid))
 	}
-	if bm.Guid != guid {
-		panic(fmt.Sprintf("guids do not match: %v != %v", bm.Guid, guid))
-	}
 
-	// test nonexistent
-	err = zfs.ZFSDestroyFilesystemVersion(ds, bm)
-	if err != nil {
-		panic(err)
-	}
-	bm2, err := zfs.ZFSGetReplicationCursor(ds)
-	if bm2 != nil {
-		panic(fmt.Sprintf("expecting no replication cursor after deleting it, got %v", bm))
-	}
-	if err != nil {
-		panic(fmt.Sprintf("expecting no error for getting nonexistent replication cursor, bot %v", err))
-	}
+	// try moving
+	cursor1BookmarkName, err := endpoint.ReplicationCursorBookmarkName(fs, snap.GUID, jobid)
+	require.NoError(ctx, err)
 
-	// TODO test moving the replication cursor
+	snap2 := sendArgVersion(fs, "@2 with space")
+	destroyed, err = endpoint.MoveReplicationCursor(ctx, fs, &snap2, jobid)
+	require.NoError(ctx, err)
+	require.Equal(ctx, 1, len(destroyed))
+	require.Equal(ctx, zfs.Bookmark, destroyed[0].Type)
+	require.Equal(ctx, cursor1BookmarkName, destroyed[0].Name)
 }

platformtest/tests/resumableRecvAndTokenHandling.go

@@ -0,0 +1,64 @@
+package tests
+
+import (
+	"fmt"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+func ResumableRecvAndTokenHandling(ctx *platformtest.Context) {
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+	DESTROYROOT
+	CREATEROOT
+	+	"send er"
+	`)
+
+	sendFS := fmt.Sprintf("%s/send er", ctx.RootDataset)
+	recvFS := fmt.Sprintf("%s/recv er", ctx.RootDataset)
+
+	supported, err := zfs.ResumeRecvSupported(ctx, mustDatasetPath(sendFS))
+	check(err)
+
+	src := makeDummyDataSnapshots(ctx, sendFS)
+
+	s := makeResumeSituation(ctx, src, recvFS, zfs.ZFSSendArgs{
+		FS:          sendFS,
+		To:          src.snapA,
+		Encrypted:   &zfs.NilBool{B: false},
+		ResumeToken: "",
+	}, zfs.RecvOptions{
+		RollbackAndForceRecv: false, // doesnt' exist yet
+		SavePartialRecvState: true,
+	})
+
+	if !supported {
+		_, ok := s.recvErr.(*zfs.ErrRecvResumeNotSupported)
+		require.True(ctx, ok)
+
+		// we know that support on sendFS implies support on recvFS
+		// => asser that if we don't support resumed recv, the method returns ""
+		tok, err := zfs.ZFSGetReceiveResumeTokenOrEmptyStringIfNotSupported(ctx, mustDatasetPath(recvFS))
+		check(err)
+		require.Equal(ctx, "", tok)
+
+		return // nothing more to test for recv that doesn't support -s
+	}
+
+	getTokenRaw, err := zfs.ZFSGetReceiveResumeTokenOrEmptyStringIfNotSupported(ctx, mustDatasetPath(recvFS))
+	check(err)
+
+	require.NotEmpty(ctx, getTokenRaw)
+	decodedToken, err := zfs.ParseResumeToken(ctx, getTokenRaw)
+	check(err)
+
+	require.True(ctx, decodedToken.HasToGUID)
+	require.Equal(ctx, s.sendArgs.To.GUID, decodedToken.ToGUID)
+
+	recvErr := s.recvErr.(*zfs.RecvFailedWithResumeTokenErr)
+	require.Equal(ctx, recvErr.ResumeTokenRaw, getTokenRaw)
+	require.Equal(ctx, recvErr.ResumeTokenParsed, decodedToken)
+}

platformtest/tests/resumeTokenParsing.go

@@ -0,0 +1,105 @@
+package tests
+
+import (
+	"github.com/stretchr/testify/require"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+type resumeTokenTest struct {
+	Msg         string
+	Token       string
+	ExpectToken *zfs.ResumeToken
+	ExpectError error
+}
+
+func (rtt *resumeTokenTest) Test(t *platformtest.Context) {
+
+	resumeSendSupported, err := zfs.ResumeSendSupported()
+	if err != nil {
+		t.Errorf("cannot determine whether resume supported: %T %s", err, err)
+		t.FailNow()
+		return
+	}
+
+	res, err := zfs.ParseResumeToken(t, rtt.Token)
+
+	// if decoding is not supported, don't bother with the expectations
+	if !resumeSendSupported {
+		require.Error(t, err)
+		require.Equal(t, zfs.ResumeTokenDecodingNotSupported, err)
+		return
+	}
+
+	if rtt.ExpectError != nil {
+		require.EqualValues(t, rtt.ExpectError, err)
+		return
+	}
+	if rtt.ExpectToken != nil {
+		require.Nil(t, err)
+		require.EqualValues(t, rtt.ExpectToken, res)
+		return
+	}
+}
+
+func ResumeTokenParsing(ctx *platformtest.Context) {
+
+	// cases generated using resumeTokensGenerate.bash on ZoL 0.8.1
+	cases := []resumeTokenTest{
+		{
+			Msg:   "zreplplatformtest/dst/full",
+			Token: "1-b338b54f3-c0-789c636064000310a500c4ec50360710e72765a52697303030419460caa7a515a796806474e0f26c48f2499525a9c540ba42430fabfe92fcf4d2cc140686c88a76d578ae45530c90e439c1f27989b9a90c0c5545a905390539892569f945b940234bf48b8b921d12c1660200c61a1aba",
+			ExpectToken: &zfs.ResumeToken{
+				HasToGUID: true,
+				ToGUID:    0x94a20a5f25877859,
+				ToName:    "zreplplatformtest/src@a",
+			},
+		},
+		{
+			Msg:   "zreplplatformtest/dst/full_raw",
+			Token: "1-e3f40c323-f8-789c636064000310a500c4ec50360710e72765a52697303030419460caa7a515a796806474e0f26c48f2499525a9c540da454f0fabfe92fcf4d2cc140686c88a76d578ae45530c90e439c1f27989b9a90c0c5545a905390539892569f945b940234bf48b8b921d12c1e6713320dc9f9c9f5b50945a5c9c9f0d119380ba07265f94580e936200004ff12141",
+			ExpectToken: &zfs.ResumeToken{
+				HasToGUID:     true,
+				ToGUID:        0x94a20a5f25877859,
+				ToName:        "zreplplatformtest/src@a",
+				HasCompressOK: true, CompressOK: true,
+				HasRawOk: true, RawOK: true,
+			},
+		},
+
+		{
+			Msg:   "zreplplatformtest/dst/inc",
+			Token: "1-eadabb296-e8-789c636064000310a501c49c50360710a715e5e7a69766a63040416445bb6a3cd7a2290a40363b92bafca4acd4e412060626a83a0cf9b4b4e2d412908c0e5c9e0d493ea9b224b518483ba8ea61d55f920f714515bf9b3fc3c396ef0648f29c60f9bcc4dc54a07c516a414e414e62495a7e512ed0c812fde2a2648724b09900d43e2191",
+			ExpectToken: &zfs.ResumeToken{
+				HasFromGUID: true, FromGUID: 0x94a20a5f25877859,
+				HasToGUID: true, ToGUID: 0xf784e1004f460f7a,
+				ToName: "zreplplatformtest/src@b",
+			},
+		},
+		{
+			Msg:   "zreplplatformtest/dst/inc_raw",
+			Token: "1-1164f8d409-120-789c636064000310a501c49c50360710a715e5e7a69766a63040416445bb6a3cd7a2290a40363b92bafca4acd4e412060626a83a0cf9b4b4e2d412908c0e5c9e0d493ea9b224b51848f368eb61d55f920f714515bf9b3fc3c396ef0648f29c60f9bcc4dc54a07c516a414e414e62495a7e512ed0c812fde2a2648724b079dc0c087f26e7e71614a51617e76743c424a0ee81c9172596c3a41800dd2c2818",
+			ExpectToken: &zfs.ResumeToken{
+				HasFromGUID: true, FromGUID: 0x94a20a5f25877859,
+				HasToGUID: true, ToGUID: 0xf784e1004f460f7a,
+				ToName:        "zreplplatformtest/src@b",
+				HasCompressOK: true, CompressOK: true,
+				HasRawOk: true, RawOK: true,
+			},
+		},
+
+		// manual test csaes
+		{
+			Msg:         "corrupted",
+			Token:       "1-1164f8d409-120-badf00d064000310a501c49c50360710a715e5e7a69766a63040416445bb6a3cd7a2290a40363b92bafca4acd4e412060626a83a0cf9b4b4e2d412908c0e5c9e0d493ea9b224b51848f368eb61d55f920f714515bf9b3fc3c396ef0648f29c60f9bcc4dc54a07c516a414e414e62495a7e512ed0c812fde2a2648724b079dc0c087f26e7e71614a51617e76743c424a0ee81c9172596c3a41800dd2c2818",
+			ExpectError: zfs.ResumeTokenCorruptError,
+		},
+	}
+
+	for _, test := range cases {
+		ctx.Logf("BEGIN SUBTEST: %s", test.Msg)
+		test.Test(ctx)
+		ctx.Logf("COMPLETE SUBTEST: %s", test.Msg)
+	}
+}

platformtest/tests/resumeTokensGenerate.bash

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+set -euo pipefail
+set -x
+
+POOLNAME="zreplplatformtest"
+POOLIMG="$1"
+
+if zpool status "$POOLNAME"; then
+    exit 1
+fi
+
+if [ -e "$POOLIMG" ]; then
+    exit 1
+fi
+fallocate -l 500M "$POOLIMG"
+zpool create "$POOLNAME" "$POOLIMG"
+
+SRC_DATASET="$POOLNAME/src"
+DST_ROOT="$POOLNAME/dst"
+
+keylocation="$(mktemp /tmp/ZREPL_PLATFORMTEST_GENERATE_TOKENS_KEYFILE_XXX)"
+echo "foobar123" > "$keylocation"
+zfs create -o encryption=on -o keylocation="file:///$keylocation" -o keyformat=passphrase "$SRC_DATASET"
+rm "$keylocation"
+
+SRC_MOUNT="$(zfs get -H -o value mountpoint "$SRC_DATASET")"
+test -d "$SRC_MOUNT"
+
+A="$SRC_DATASET"@a
+B="$SRC_DATASET"@b
+dd if=/dev/urandom of="$SRC_MOUNT"/dummy_data bs=1M count=5
+zfs snapshot "$A"
+dd if=/dev/urandom of="$SRC_MOUNT"/dummy_data bs=1M count=5
+zfs snapshot "$B"
+
+zfs create "$DST_ROOT"
+
+cutoff="dd bs=1024 count=3K"
+
+set +e
+zfs send    "$A"         | $cutoff | zfs recv -s "$DST_ROOT"/full
+
+zfs send "$A" | zfs recv "$DST_ROOT"/inc
+zfs send    -i "$A" "$B" | $cutoff | zfs recv -s "$DST_ROOT"/inc
+
+zfs send -w "$A"         | $cutoff | zfs recv -s "$DST_ROOT"/full_raw
+
+zfs send -w "$A" | zfs recv "$DST_ROOT"/inc_raw
+zfs send -w -i "$A" "$B" | $cutoff | zfs recv -s "$DST_ROOT"/inc_raw
+set -e
+
+TOKENS="$(zfs list -H -o name,receive_resume_token -r "$DST_ROOT")"
+
+echo "$TOKENS" | awk -e '//{ if ($2 == "-") {  } else { system("zfs send -nvt " + $2);} }'
+
+zpool destroy "$POOLNAME"
+rm "$POOLIMG"

platformtest/tests/sendArgsValidation.go

@@ -0,0 +1,208 @@
+package tests
+
+import (
+	"fmt"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/zrepl/zrepl/platformtest"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+func SendArgsValidationEncryptedSendOfUnencryptedDatasetForbidden(ctx *platformtest.Context) {
+
+	supported, err := zfs.EncryptionCLISupported(ctx)
+	check(err)
+	expectNotSupportedErr := !supported
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+	DESTROYROOT
+	CREATEROOT
+	+	"send er"
+	+   "send er@a snap"
+	`)
+
+	fs := fmt.Sprintf("%s/send er", ctx.RootDataset)
+	props := mustGetProps(fs + "@a snap")
+
+	sendArgs := zfs.ZFSSendArgs{
+		FS: fs,
+		To: &zfs.ZFSSendArgVersion{
+			RelName: "@a snap",
+			GUID:    props.Guid,
+		},
+		Encrypted:   &zfs.NilBool{B: true},
+		ResumeToken: "",
+	}
+	stream, err := zfs.ZFSSend(ctx, sendArgs)
+	if err == nil {
+		defer stream.Close()
+	}
+
+	if expectNotSupportedErr {
+		require.Error(ctx, err)
+		require.Equal(ctx, zfs.ErrEncryptedSendNotSupported, err)
+		return
+	}
+	require.Error(ctx, err)
+	ctx.Logf("send err: %T %s", err, err)
+	validationErr, ok := err.(*zfs.ZFSSendArgsValidationError)
+	require.True(ctx, ok)
+	require.True(ctx, validationErr.What == zfs.ZFSSendArgsEncryptedSendRequestedButFSUnencrypted)
+}
+
+func SendArgsValidationResumeTokenEncryptionMismatchForbidden(ctx *platformtest.Context) {
+
+	supported, err := zfs.EncryptionCLISupported(ctx)
+	check(err)
+	if !supported {
+		ctx.SkipNow()
+	}
+	supported, err = zfs.ResumeSendSupported()
+	check(err)
+	if !supported {
+		ctx.SkipNow()
+	}
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+	DESTROYROOT
+	CREATEROOT
+	+	"send er" encrypted
+	`)
+
+	sendFS := fmt.Sprintf("%s/send er", ctx.RootDataset)
+	unencRecvFS := fmt.Sprintf("%s/unenc recv", ctx.RootDataset)
+	encRecvFS := fmt.Sprintf("%s/enc recv", ctx.RootDataset)
+
+	src := makeDummyDataSnapshots(ctx, sendFS)
+
+	unencS := makeResumeSituation(ctx, src, unencRecvFS, zfs.ZFSSendArgs{
+		FS:        sendFS,
+		To:        src.snapA,
+		Encrypted: &zfs.NilBool{B: false}, // !
+	}, zfs.RecvOptions{
+		RollbackAndForceRecv: false,
+		SavePartialRecvState: true,
+	})
+
+	encS := makeResumeSituation(ctx, src, encRecvFS, zfs.ZFSSendArgs{
+		FS:        sendFS,
+		To:        src.snapA,
+		Encrypted: &zfs.NilBool{B: true}, // !
+	}, zfs.RecvOptions{
+		RollbackAndForceRecv: false,
+		SavePartialRecvState: true,
+	})
+
+	// threat model: use of a crafted resume token that requests an unencrypted send
+	//               but send args require encrypted send
+	{
+		var maliciousSend zfs.ZFSSendArgs = encS.sendArgs
+		maliciousSend.ResumeToken = unencS.recvErrDecoded.ResumeTokenRaw
+
+		stream, err := zfs.ZFSSend(ctx, maliciousSend)
+		if err == nil {
+			defer stream.Close()
+		}
+		require.Nil(ctx, stream)
+		require.Error(ctx, err)
+		ctx.Logf("send err: %T %s", err, err)
+		validationErr, ok := err.(*zfs.ZFSSendArgsValidationError)
+		require.True(ctx, ok)
+		require.Equal(ctx, validationErr.What, zfs.ZFSSendArgsResumeTokenMismatch)
+		ctx.Logf("%s", validationErr)
+
+		mismatchError, ok := validationErr.Msg.(*zfs.ZFSSendArgsResumeTokenMismatchError)
+		require.True(ctx, ok)
+		require.Equal(ctx, mismatchError.What, zfs.ZFSSendArgsResumeTokenMismatchEncryptionNotSet)
+	}
+
+	// threat model: use of a crafted resume token that requests an encryped send
+	//               but send args require unencrypted send
+	{
+		var maliciousSend zfs.ZFSSendArgs = unencS.sendArgs
+		maliciousSend.ResumeToken = encS.recvErrDecoded.ResumeTokenRaw
+
+		stream, err := zfs.ZFSSend(ctx, maliciousSend)
+		if err == nil {
+			defer stream.Close()
+		}
+		require.Nil(ctx, stream)
+		require.Error(ctx, err)
+		ctx.Logf("send err: %T %s", err, err)
+		validationErr, ok := err.(*zfs.ZFSSendArgsValidationError)
+		require.True(ctx, ok)
+		require.Equal(ctx, validationErr.What, zfs.ZFSSendArgsResumeTokenMismatch)
+		ctx.Logf("%s", validationErr)
+
+		mismatchError, ok := validationErr.Msg.(*zfs.ZFSSendArgsResumeTokenMismatchError)
+		require.True(ctx, ok)
+		require.Equal(ctx, mismatchError.What, zfs.ZFSSendArgsResumeTokenMismatchEncryptionSet)
+	}
+
+}
+
+func SendArgsValidationResumeTokenDifferentFilesystemForbidden(ctx *platformtest.Context) {
+
+	supported, err := zfs.EncryptionCLISupported(ctx)
+	check(err)
+	if !supported {
+		ctx.SkipNow()
+	}
+	supported, err = zfs.ResumeSendSupported()
+	check(err)
+	if !supported {
+		ctx.SkipNow()
+	}
+
+	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
+	DESTROYROOT
+	CREATEROOT
+	+	"send er1"
+	+	"send er2"
+	`)
+
+	sendFS1 := fmt.Sprintf("%s/send er1", ctx.RootDataset)
+	sendFS2 := fmt.Sprintf("%s/send er2", ctx.RootDataset)
+	recvFS := fmt.Sprintf("%s/unenc recv", ctx.RootDataset)
+
+	src1 := makeDummyDataSnapshots(ctx, sendFS1)
+	src2 := makeDummyDataSnapshots(ctx, sendFS2)
+
+	rs := makeResumeSituation(ctx, src1, recvFS, zfs.ZFSSendArgs{
+		FS:        sendFS1,
+		To:        src1.snapA,
+		Encrypted: &zfs.NilBool{B: false},
+	}, zfs.RecvOptions{
+		RollbackAndForceRecv: false,
+		SavePartialRecvState: true,
+	})
+
+	// threat model: forged resume token tries to steal a full send of snapA on fs2 by
+	//               presenting a resume token for full send of snapA on fs1
+	var maliciousSend zfs.ZFSSendArgs = zfs.ZFSSendArgs{
+		FS: sendFS2,
+		To: &zfs.ZFSSendArgVersion{
+			RelName: src2.snapA.RelName,
+			GUID:    src2.snapA.GUID,
+		},
+		Encrypted:   &zfs.NilBool{B: false},
+		ResumeToken: rs.recvErrDecoded.ResumeTokenRaw,
+	}
+
+	stream, err := zfs.ZFSSend(ctx, maliciousSend)
+	if err == nil {
+		defer stream.Close()
+	}
+	require.Nil(ctx, stream)
+	require.Error(ctx, err)
+	ctx.Logf("send err: %T %s", err, err)
+	validationErr, ok := err.(*zfs.ZFSSendArgsValidationError)
+	require.True(ctx, ok)
+	require.Equal(ctx, validationErr.What, zfs.ZFSSendArgsResumeTokenMismatch)
+	ctx.Logf("%s", validationErr)
+
+	mismatchError, ok := validationErr.Msg.(*zfs.ZFSSendArgsResumeTokenMismatchError)
+	require.True(ctx, ok)
+	require.Equal(ctx, mismatchError.What, zfs.ZFSSendArgsResumeTokenMismatchFilesystem)
+}

platformtest/tests/tests.go

@@ -18,4 +18,17 @@ var Cases = []Case{
 	UndestroyableSnapshotParsing,
 	GetNonexistent,
 	ReplicationCursor,
+	RollupReleaseIncluding,
+	RollupReleaseExcluding,
+	RollupReleaseMostRecentIsBookmarkWithoutSnapshot,
+	RollupReleaseMostRecentIsBookmarkAndSnapshotStillExists,
+	RollupReleaseMostRecentDoesntExist,
+	IdempotentHold,
+	IdempotentBookmark,
+	IdempotentDestroy,
+	ResumeTokenParsing,
+	ResumableRecvAndTokenHandling,
+	SendArgsValidationEncryptedSendOfUnencryptedDatasetForbidden,
+	SendArgsValidationResumeTokenEncryptionMismatchForbidden,
+	SendArgsValidationResumeTokenDifferentFilesystemForbidden,
 }

platformtest/tests/undestroyableSnapshotParsing.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/stretchr/testify/require"
+
 	"github.com/zrepl/zrepl/platformtest"
 	"github.com/zrepl/zrepl/zfs"
 )

replication/design.md

@@ -0,0 +1,342 @@
+The goal of this document is to describe what **logical steps** zrepl takes to replicate ZFS filesystems.
+Note that the actual code executing these steps is spread over the `endpoint.{Sender,Receiver}` RPC endpoint implementations. The code in `replication/{driver,logic}` (mostly `logic.Step.doReplication`) drives the replication and invokes the `endpoint` methods (locally or via RPC).
+Hence, when trying to map algorithm to implementation, use the code in package `replication` as the entrypoint and follow the RPC calls.
+
+
+* The [Single Replication Step](#zrepl-algo-single-step) algorithm is implemented as described
+  * step holds are implemented as described
+  * step bookmarks rely on bookmark cloning, which is WIP in OpenZFS (see respective TODO comments)
+  * the feature to hold receive-side `to` immediately after replication is used to move the `last-received-hold` forward
+    * this is a little more than what we allow in the algorithm (we only allow specifying a hold tag whereas moving the `last-received-hold` is a little more complex)
+  * the algorithm's sender-side callback is used move the `zrepl_CURSOR` bookmark to point to `to`
+* The `zrepl_CURSOR` bookmark and the `last-received-hold` ensure that future replication steps can always be done using incremental replication:
+  * Both reference / hold the last successfully received snapshot `to`.
+  * Thus, `to` or `#zrepl_CURSOR_G_${to.GUID}_J_${jobid}` can always be used for a future incremental replication step `to => future-to`:
+    * incremental send will be possible because `to` doesn't go away because we claim ownership of the `#zrepl_CURSOR` namespace
+    * incremental recv will be possible iff
+      * `to` will still be present on the recv-side because of `last-received-hold`
+      * the recv-side fs doesn't get newer snapshots than `to` in the meantime
+        * guaranteed because the zrepl model of the receiver assumes ownership of the filesystems it receives into
+          * if that assumption is broken, future replication attempts will fail with a conflict
+* The [Algorithm for Planning and Executing Replication of an Filesystems](#zrepl-algo-filesystem) is a design draft and not used
+* We also have [Notes on Planning and Executing Replication of Multiple Filesystems](#zrepl-algo-multiple-filesystems-notes)
+
+---
+
+<a id="zrepl-algo-single-step"></a>
+## Algorithm for a Single Replication Step
+
+The algorithm described below describes how a single replication step must be implemented.
+A *replication step* is a full send of a snapshot `to` for initial replication, or an incremental send (`from => to`) for incremental replication.
+
+The algorithm **ensures resumability** of the replication step in presence of
+
+* uncoordinated or unsynchronized destruction of the filesystem, snapshots, or bookmarks involved in the replication step
+* network failures at any time
+* other instances of this algorithm executing the same step in parallel (e.g. concurrent replication to different destinations)
+
+To accomplish this goal, the algorithm **assumes ownersip of parts of the ZFS hold tag namespace and the bookmark namespace**:
+* holds with prefix `zrepl_STEP` on any snapshot are reserved for zrepl
+* bookmarks with prefix `zrepl_STEP` are reserved for zrepl
+
+Resumability of a step cannot be guaranteed if these sub-namespaces are manipulated through software other than zrepl.
+
+Note that the algorithm **does not ensure** that a replication *plan*, which describes a *set* of replication steps, can be carried out successfully.
+If that is desirable, additional measures outside of this algorithm must be taken.
+
+---
+
+### Definitions:
+
+#### Step Completion & Invariants
+
+The replication step (full `to` send or `from => to` send) is *complete* iff the algorithm ran to completion without errors or a permanent non-network error is reported by sender or receiver.
+
+Specifically, the algorithm may be invoked with the same `from` and `to` arguments, and potentially a `resume_token`, after a temporary (like network-related) failure:
+**Unless permanent errors occur, repeated invocations of the algorithm with updated resume token will converge monotonically (but not strictly monotonically) toward completion.**
+
+Note that the mere existence of `to` on the receiving side does not constitue completion, since there may still be post-recv actions to be performed on sender and receiver.
+
+#### Job and Job ID
+This algorithm supports that *multiple* instance of it run in parallel on the *same* step (full `to` / `from => to` pair).
+An exemplary use case for this feature are concurrent replication jobs that replicate the same dataset to different receivers.
+
+**We require that all parallel invocations of this algorithm provide different and unique `jobid`s.**
+Violation of `jobid` uniqueness across parallel jobs may result in interference between instances of this algorithm, resulting in potential compromise of resumability.
+
+After a step is *completed*, `jobid` is guaranteed to not be encoded in on-disk state.
+Before a step is completed, there is no such guarantee.
+Changing the `jobid` before step completion may compromise resumability and may leak the underlying ZFS holds or step bookmarks (i.e. zrepl won't clean them up)
+Note the definition of *complete* above.
+
+#### Step Bookmark
+
+A step bookmark is our equivalent of ZFS holds, but for bookmarks.<br/>
+A step bookmark is a ZFS bookmark whose name matches the following regex:
+
+```
+STEP_BOOKMARK = #zrepl_STEP_bm_G_([0-9a-f]+)_J_(.+)
+```
+
+- capture group `1` must be the guid of `zfs get guid ${STEP_BOOKMARK}`, encoded hexadecimal (without leading `0x`) and fixed-length (i.e. padded with leading zeroes)
+- capture group `2` must be equal to the `jobid`
+
+### Algorithm
+
+INPUT:
+
+* `jobid`
+* `from`: snapshot or bookmark: may be nil for full send
+* `to`: snapshot, must never be nil
+* `resume_token` (may be nil)
+* (`from` and `to` must be on the same filesystem)
+
+#### Prepare-Phase
+
+Send-side: make sure `to` and `from` don't go away
+
+- hold `to` using `idempotent_hold(to, zrepl_STEP_J_${jobid})`
+- make sure `from` doesn't go away:
+  - if `from` is a snapshot: hold `from` using `idempotent_hold(from, zrepl_STEP_J_${jobid})`
+  - else `idempotent_step_bookmark(from)` (`from` is a bookmark)
+    - PERMANENT ERROR if this fails (e.g. because `from` is a bookmark whose snapshot no longer exists and we don't have bookmark copying yet (ZFS feature is in development) )
+      - Why? we must assume the given bookmark is externally managed (i.e. not in the )
+      - this means the bookmark is externally created bookmark and cannot be trusted to persist until the replication step succeeds
+      - Maybe provide an override-knob for this behavior
+
+Recv-side: no-op
+
+- `from` cannot go away once we received enough data for the step to be resumable:
+    ```text
+    # do a partial incremental recv @a=>@b (i.e. recv with -s, and abort the incremental recv in the middle)
+    # try destroying the incremental source on the receiving side
+    zfs destroy p1/recv@a
+    cannot destroy 'p1/recv@a': snapshot has dependent clones
+    use '-R' to destroy the following datasets:
+    p1/recv/%recv
+    # => doesn't work, because zfs recv is implemented as a `clone` internally, that's exactly what we want
+    ```
+
+- if recv-side `to` exists, goto cleaup-phase (no replication to do)
+  
+- `to` cannot be destroyed while being received, because it isn't visible as a snapshot yet (it isn't yet one after all)
+
+#### Replication Phase
+
+Attempt the replication step:
+start `zfs send` and pipe its output into `zfs recv` until an error occurs or `recv` returns without error.
+
+Let us now think about interferences that could occur during this phase, and ensure that none of them compromise the goals of this algorithm, i.e., monotonic convergence toward step completion using resumable send & recv.
+
+**Safety from External Pruning**
+We are safe from pruning during the replication step because we have guarantees that no external action will destroy send-side `from` and `to`, and recv-side `to` (for both snapshot and bookmark `from`s)<br/>
+
+**Safety In Presence of Network Failures During Replication**
+Network failures during replication can be recovered from using resumable send & recv:
+
+- Network failure before the receive-side could stored data:
+  - Send-side `from` and `to` are guaranteed to be still present due to zfs holds
+  - recv-side `from` may no longer exist because we don't `hold` it explicitly
+    - if that is the case, ERROR OUT, step can never complete
+  - If the step planning algorithm does not include the step, for example because a snapshot filter configuration was changed by the user inbetween which hides `from` or `to` from the second planning attempt: **tough luck, we're leaking all holds**
+- Network failure during the replication
+  - send-side `from` and `to` are still present due to zfs holds
+  - recv-side `from` is still present because the partial receive state prevents its destruction (see prepare-phase)
+  - if recv-side hasa resume token, the resume token will continue to work on the sender because `from`s and `to` are still present
+- Network failure at the end of the replication step stream transmission
+  - Variant A: failure from the sender's perspective, success from the receiver's perspective
+    - receive-side `to` doesn't have a hold and could be destroyed anytime
+    - receive-side `from` doesn't have a hold and could be destroyed anytime
+    - thus, when the step is invoked again, pattern match `(from_exists, to_exists)`
+      - `(true, true)`: prepare-phase will early-exit
+      - `(false,true)`: prepare-phase will error out bc. `from` does not exist
+      - `(true, false)`: entire step will be re-done
+        - FIXME monotonicity requirement does not hold
+      - `(false, false)`: prepare-phase will error out bc. `from` does not exist
+  - Variant B: success from the sender's perspective, failure from the receiver's perspective
+    - No idea how this would happen except for bugs in error reporting in the replication protocol
+    - Misclassification by the sender, most likely broken error handling in the sender or replication protocol
+    - => the sender will release holds and move the replication cursor while the receiver won't => tough luck
+
+If the RPC used for `zfs recv` returned without error, this phase is done.
+(Although the *replication step* (this algorithm) is not yet *complete*, see definition of complete).
+
+
+#### Cleanup-Phase
+
+At the end of this phase, all intermediate state we built up to support the resumable replication of the step is destroyed.
+However, consumers of this algorithm might want to take advantage of the fact that we currently still have holds / step bookmarks.
+
+##### Recv-side: Optionally hold `to` with a caller-defined tag
+
+Users of the algorithm might want to depend on `to` being available on the receiving side for a longer duration than the lifetime of the current step's algorithm invocation.
+For reasons explained in the next paragraph, we cannot guarantee that we have a `hold` when `recv` exists. If that were the case, we could take our time to provide a generalized callback to the user of the algorithm, and have them do whatever they want with `to` while we guarantee that `to` doesn't go away through the hold. But that functionality isn't available, so we only provide a fixed operation right after receive: **take a `hold` with a tag of the algorithm user's choice**. That's what's needed to guarantee that a replication plan, consisting of multiple consecutive steps, can be carried out without a receive-side prune job interfering by destroying `to`. Technically, this step is racy, i.e., it could happen that `to` is destroyed between `recv` and `hold`. But this is a) unlikely and b) not fatal because we can detect that hold fails because the 'dataset does not exist` and re-do the entire transmission since we still hold send-side `from` and `to`, i.e. we just lose a lot of work in rare cases.
+
+So why can't we have a `hold` at the time `recv` exits?
+It seems like [`zfs send --holds`](https://github.com/zfsonlinux/zfs/commit/9c5e88b1ded19cb4b19b9d767d5c71b34c189540) could be used to send the send-side's holds to the receive-side. But that flag always sends all holds, and `--holds` is implemented in user-space libzfs, i.e., doesn't happen in the same txg as the recv completion. Thus, the race window is in fact only smaller (unless we oversaw some synchronization in userland zfs).
+But if we're willing to entertain the idea a little further, we still hit the problem that `--holds` sends _all_ holds, whereas our goal is to _temporarily_ have >= 1 hold that we own until the callback is done, and then release all of the received holds so that no holds created by us exist after this algorithm completes.
+Since there could be concurrent `zfs hold` invocations on the sender and receiver while this algorithm runs, and because `--holds` doesn't provide info about which holds were sent, we cannot correctly destroy _exactly_ those holds that we received.
+
+##### Send-side: callback to consumer, then cleanup
+We can provide the algorithm user with a generic callback because we have holds / step bookmarks for `to` and `from`, respectively.
+
+Example use case for the sender-side callback is the replication cursor, see algorithm for filesystem replication below.
+
+After the callback is done: cleanup holds & step bookmark:
+
+- `idempotent_release(to, zrepl_STEP_J_${jobid})`
+- make sure `from` can now go away:
+  - if `from` is a snapshot: `idempotent_release(from, zrepl_STEP_J_${jobid})`
+  - else `idempotent_step_bookmark_destroy(from)`
+    - if `from` fulfills the properties of a step bookmark: destroy it
+    - otherwise: it's a bookmark not created by this algorithm that happened to be used for replication: leave it alone
+      - that can only happen if user used the override knob
+
+Note that "make sure `from` can now go away" is the inverse of "Send-side: make sure `to` and `from` don't go away". Those are relatively complex operations and should be implemented in the same file next to each other to ease maintainability.
+
+---
+
+### Notes & Pseudo-APIs used in the algorithm
+
+- `idempotent_hold(snapshot s, string tag)` like zfs hold, but doesn't error if hold already exists
+- `idempotent_release(snapshot s, string tag)` like zfs hold, but doesn't error if hold already exists
+- `idempotent_step_bookmark(snapshot_or_bookmark b)` creates a *step bookmark* of b
+  - determine step bookmark name N
+  - if `N` already exists, verify it's a correct step bookmark => DONE or ERROR
+  - if `b` is a snapshot, issue `zfs bookmark`
+  - if `b` is a bookmark:
+    - if bookmark cloning supported, use it to duplicate the bookmark
+    - else ERROR OUT, with an error that upper layers can identify as such, so that they are able to ignore the fact that we couldn't create a step bookmark 
+- `idempotent_destroy(bookmark #b_$GUID, of a snapshot s)` must atomically check that `$GUID == s.guid` before destroying s
+- `idempotent_bookmark(snapshot s, $GUID, name #b_$GUID)` must atomically check that `$GUID == s.guid` at the time of bookmark creation
+- `idempotent_destroy(snapshot s)` must atomically check that zrepl's `s.guid` matches the current `guid` of the snapshot (i.e. destroy by guid)
+
+
+<a id="zrepl-algo-filesystem"></a>
+## Algorithm for Planning and Executing Replication of a Filesystems (planned, not implemented yet)
+
+This algorithm describes how a filesystem or zvol is replicated in zrepl.
+The algorithm is invoked with a `jobid`, `sender`, `receiver`, a sender-side `filesystem path`.
+It builds a diff between the sender and receiver filesystem bookmarks+snapshots and determines whether a replication conflict exists or whether fast-forward replication using full or incremental sends is possible.
+In case of conflict, the algorithm errors out with a conflict description that can be used to manually or automatically resolve the conflict.
+Otherwise, the algorithm builds a list of replication steps that are then worked on sequentially by the "Algorithm for a Single Replication Step".
+
+The algorithm ensures that a plan can be executed exactly as planned by aquiring appropriate zfs holds.
+The algorithm can be configured to retry a plan when encountering non-permanent errors (e.g. network errors).
+However, permanent errors result in the plan being cancelled.
+
+Regardless of whether a plan can be executed to completion or is cancelled, the algorithm guarantees that leftover artifacts (i.e. holds) of its invocation are cleaned up.
+However, since network failure can occur at any point, there might be stale holds on sending or receiving side after a crash or other error.
+These will be cleaned up on a subsequent invocation of this algorithm with the same `jobid`.
+
+The algorithm is fit to be executed in parallel from the same sender to different receivers.
+To be clear: replicating in parallel from the same sender to different receivers is supported.
+But one instance of the algorithm assumes ownership of the `filesystem path` on the receiver.
+
+The algorithm reserves the following sub-namespaces:
+* zfs hold: `zrepl_FS`
+* bookmark names: `zrepl_FS`
+
+### Definitions
+
+#### ZFS Filesystem Path
+We refer to the name of a ZFS filesystem or volume as a *filesystem path*, sometimes just *path*.
+The name includes the pool name.
+
+#### Sender and Receiver
+Sender and Receiver are passed as RPC stubs to the algorithm.
+One of those RPC stubs will typically be local, i.e., call methods on a struct in the same address space.
+The other RPC stub may invoke actual calls over the network (unless local replication is used).
+The algorithm does not make any assumption about which object is local or an actual stub.
+This design decouples the replication logic (described in this algorithm) from the question which side (sender or receiver) initiates the replication.
+
+### Algorithm
+
+**Cleanup Previous Invocations With Same `jobid`** by scanning the filesystem's list of snapshots and step bookmarks, and destroying any which was created by this algorithm when it was invoked with `jobid`.<br/>
+TODO HOW
+
+**Build a fast-forward list of replication steps** `STEPS`.
+`STEPS` may contain an optional initial full send, and subsequent incremental send steps.
+`STEPS[0]` may also have a resume token.
+If fast-forward is not possible, produce a conflict description and ERROR OUT.<br/>
+TODOs:
+- make it configurable what snapshots are included in the list (i.e. every one we see, only most recent, at least one every X hours, ...)
+
+**Ensure that we will be able to carry out all steps** by aquiring holds or fsstep bookmarks on the sending side
+- `idempotent_hold([s.to for s in STEPS], zrepl_FS_J_${jobid})`
+- `if STEPS[0].from != nil: idempotent_FSSTEP_bookmark(STEPS[0].from, zrepl_FSSTEP_bm_G_${STEPS[0].from.guid}_J_${jobid})` 
+  
+**Determine which steps have not been completed (`uncompleted_steps`)** (we might be in an second invocation of this algorithm after a network failure and some steps might already be done):
+- `res_tok := receiver.ResumeToken(fs)`
+- `rmrfsv := receiver.MostRecentFilesystemVersion(fs)`
+- if `res_tok !=  nil`: ensure that `res_tok` has a correspondinng step in `STEPS`, otherwise ERROR OUT
+- if `rmrfsv != nil`: ensure that `res_tok` has a correspondinng step in `STEPS`, otherwise ERROR OUT
+- if `(res_token != nil && rmrfsv != nil)`: ensure that `res_tok` is the subsequent step to the one we found for `rmrfsv`
+- if both are nil, we are at the beginning, `uncompleted_steps = STEPS` and goto next block
+- `rstep := if res_tok != nil { res_tok } else { rmrfsv }`
+- `uncompleted_steps := STEPS[find_step_idx(STEPS, rstep).expect("must exist, checked above"):]`
+  - Note that we do not explicitly check for the completion of prior replication steps.
+    All we care about is what needs to be done from `rstep`.
+  - This is intentional and necessary because we cummutatively release all holds and step bookmarks made for steps that preceed a just-completed step (see next paragraph)
+
+**Execute uncompleted steps**<br/>
+Invoke the "Algorithm for a Single Replication Step" for each step in `uncompleted_steps`.
+Remember to pass the resume token if one exists.
+
+In the wind-down phase of each replication step `from => to`, while the per-step algorithm still holds send-side `from` and `to`, as well as recv-side `to`:
+
+- Sending side: **Idempotently move the replication cursor to `to`.**
+  - Why: replication cursor tracks the sender's last known replication state, outlives the current plan, but is required to guarantee that future invocations of this algorithm find an incremental path.
+  - Impl for 'atomic' move: have two cursors (fixes [#177](https://github.com/zrepl/zrepl/issues/177))
+      - Idempotently cursor-bookmark `to` using `idempotent_bookmark(to, to.guid, #zrepl_replication_cursor_G_${to.guid}_J_${jobid})`
+      - Idempotently destroy old cursor-bookmark of `from` `idempotent_destroy(#zrepl_replication_cursor_G_${from.guid}_J_${jobid}, from)`
+    - If `from` is a snapshot, release the hold on it using `idempotent_release(from,  zrepl_J_${jobid})`
+    - FIXME: resumability if we crash inbetween those operations (or scrap it and wait for channel programs to bring atomicity)
+
+- Receiving side: **`idempotent_hold(to, zrepl_FS_J_${jobid})` because its going to be the next step's `from`**
+  - As discussed in the section on the per-step algorithm, this is a feature provided to us by the per-step algorithm.
+
+- Receiving side + Sending side (order doesn't matter): Make sure all holds & step bookmarks made by this plan on already replicated snapshots are released / destroyed:
+  - `idempotent_release_prior_and_including(from, zrepl_FS_TODO)`
+  - `idempotent_step_bookmark_destroy_prior_and_including(from, zrepl_FS_TODO)`
+
+**Cleanup** receiving and sending side (order doesn't matter)
+
+  - `idempotent_release_prior_and_including(STEPS[-1].to, zrepl_FS_TODO)`
+  - `idempotent_step_bookmark_destroy_prior_and_including(STEPS[-1].from, zrepl_FS_TODO)`
+
+### Notes
+
+- `idempotent_FSSTEP_bookmark` is like `idempotent_STEP_bookmark`, but with prefix `zrepl_FSSTEP` instead of `zrepl_STEP`
+
+
+<a id="zrepl-algo-multiple-filesystems-notes"></a>
+
+## Notes on Planning and Executing Replication of Multiple Filesystems
+
+### The RPC Interfaces Uses Send-side Filesystem Names to Identify a Filesystem
+
+The model of the receiver includes the assumption that it will `Receive` all snapshot streams sent to it into filesystems with paths prefixed with `root_fs`.
+This is useful for separating filesystem path namespaces for multiple clients.
+The receiver hides this prefixing in its RPC interface, i.e., when responding to `ListFilesystems` rpcs, the prefix is removed before sending the response.
+This behavior is useful to achieve symmetry in this algorithm: we do not need to take the prefixing into consideration when computing diffs.
+For the receiver, it has the advantage that `Receive` rpc can enforce the namespacing and need not trust this algorithm to apply it correctly.
+
+The receiver is also allowed (and may need to) do implement other filtering / namespace transformations.
+For example, when only `foo/a/b` has been received, but not `foo` nor `foo/a`, the receiver must not include the latter two in its `ListFilesystems` response.
+The current zrepl receiver endpoint implementation uses the `zrepl:placeholder` property to mark filesystems `foo` and `foo/a` as placeholders, and filters out such filesystems in the `ListFilesystems` response.
+Another approach would be to have a flat list of received filesystems per sender, and have a separate table that associates send-side names and receive-side filesystem paths.
+
+Similarly, the sender is allowed to filter the output of its RPC interface to hide certain filesystems or snapshots.
+
+#### Consequences of the Above Design
+
+Namespace filtering and transformations of filesystem paths on sender and receiver are user-configurable.
+Both ends of the replication setup have their own config, and do not coordinate config changes.
+This results in a number of challenges:
+
+- A sender might change its filter to allow additional filesystems to be replicated.
+  For example, where `foo/a/b` was initially allowed, the new filter might allow `foo` and `foo/a` as well.
+  If the receiver uses the `zrepl:placeholder` approach as sketched out above, this means that the receiver will need to replace the placeholder filesystems `$root_fs/foo` and `$root_fs/foo/a` with the incoming full sends of `foo` and `foo/a`.
+
+- Send-side renames cannot be handled efficiently because send-side rename effectively changes the filesystem identity because we use its name.

replication/driver/replication_driver.go

@@ -89,6 +89,8 @@ type attempt struct {
 	// if both are nil, it must be assumed that Planner.Plan is active
 	planErr *timedError
 	fss     []*fs
+
+	concurrency int
 }
 
 type timedError struct {
@@ -170,11 +172,12 @@ type step struct {
 
 type ReportFunc func() *report.Report
 type WaitFunc func(block bool) (done bool)
+type SetConcurrencyFunc func(concurrency int) error
 
 var maxAttempts = envconst.Int64("ZREPL_REPLICATION_MAX_ATTEMPTS", 3)
 var reconnectHardFailTimeout = envconst.Duration("ZREPL_REPLICATION_RECONNECT_HARD_FAIL_TIMEOUT", 10*time.Minute)
 
-func Do(ctx context.Context, planner Planner) (ReportFunc, WaitFunc) {
+func Do(ctx context.Context, initialConcurrency int, planner Planner) (ReportFunc, WaitFunc, SetConcurrencyFunc) {
 	log := getLog(ctx)
 	l := chainlock.New()
 	run := &run{
@@ -182,6 +185,8 @@ func Do(ctx context.Context, planner Planner) (ReportFunc, WaitFunc) {
 		startedAt: time.Now(),
 	}
 
+	concurrencyChanges := make(chan concurrencyChange)
+
 	done := make(chan struct{})
 	go func() {
 		defer close(done)
@@ -198,15 +203,21 @@ func Do(ctx context.Context, planner Planner) (ReportFunc, WaitFunc) {
 			run.waitReconnect.SetZero()
 			run.waitReconnectError = nil
 
+			prevConcurrency := initialConcurrency // FIXME default concurrency
+			if prev != nil {
+				prevConcurrency = prev.concurrency
+			}
+
 			// do current attempt
 			cur := &attempt{
-				l:         l,
-				startedAt: time.Now(),
-				planner:   planner,
+				l:           l,
+				startedAt:   time.Now(),
+				planner:     planner,
+				concurrency: prevConcurrency,
 			}
 			run.attempts = append(run.attempts, cur)
 			run.l.DropWhile(func() {
-				cur.do(ctx, prev)
+				cur.do(ctx, prev, concurrencyChanges)
 			})
 			prev = cur
 			if ctx.Err() != nil {
@@ -277,10 +288,25 @@ func Do(ctx context.Context, planner Planner) (ReportFunc, WaitFunc) {
 		defer run.l.Lock().Unlock()
 		return run.report()
 	}
-	return report, wait
+	setConcurrency := func(concurrency int) (reterr error) {
+		var wg sync.WaitGroup
+		wg.Add(1)
+		concurrencyChanges <- concurrencyChange{ concurrency, func(err error) {
+			defer wg.Done()
+			reterr = err // shadow
+		}}
+		wg.Wait()
+		return reterr
+	}
+	return report, wait, setConcurrency
 }
 
-func (a *attempt) do(ctx context.Context, prev *attempt) {
+type concurrencyChange struct {
+	value          int
+	resultCallback func(error)
+}
+
+func (a *attempt) do(ctx context.Context, prev *attempt, setConcurrency <-chan concurrencyChange) {
 	pfss, err := a.planner.Plan(ctx)
 	errTime := time.Now()
 	defer a.l.Lock().Unlock()
@@ -354,8 +380,8 @@ func (a *attempt) do(ctx context.Context, prev *attempt) {
 	}
 	// invariant: prevs contains an entry for each unambigious correspondence
 
-	stepQueue := newStepQueue()
-	defer stepQueue.Start(1)() // TODO parallel replication
+	stepQueue := newStepQueue(a.concurrency)
+	defer stepQueue.Start()()
 	var fssesDone sync.WaitGroup
 	for _, f := range a.fss {
 		fssesDone.Add(1)
@@ -364,16 +390,47 @@ func (a *attempt) do(ctx context.Context, prev *attempt) {
 			f.do(ctx, stepQueue, prevs[f])
 		}(f)
 	}
+	changeConcurrencyDone := make(chan struct{})
+	go func() {
+		for {
+			select {
+			case change := <-setConcurrency:
+				err := stepQueue.SetConcurrency(change.value)
+				go change.resultCallback(err)
+				if err == nil {
+					a.l.Lock()
+					a.concurrency = change.value
+					a.l.Unlock()
+				}
+			case <-changeConcurrencyDone:
+				return
+				// not waiting for ctx.Done here, the main job are the fsses
+			}
+		}
+	}()
 	a.l.DropWhile(func() {
 		fssesDone.Wait()
+		close(changeConcurrencyDone)
 	})
 	a.finishedAt = time.Now()
 }
 
 func (fs *fs) do(ctx context.Context, pq *stepQueue, prev *fs) {
-	psteps, err := fs.fs.PlanFS(ctx)
-	errTime := time.Now()
+
 	defer fs.l.Lock().Unlock()
+
+	// get planned steps from replication logic
+	var psteps []Step
+	var errTime time.Time
+	var err error
+	fs.l.DropWhile(func() {
+		// TODO hacky
+		// choose target time that is earlier than any snapshot, so fs planning is always prioritized
+		targetDate := time.Unix(0, 0)
+		defer pq.WaitReady(fs, targetDate)()
+		psteps, err = fs.fs.PlanFS(ctx) // no shadow
+		errTime = time.Now()            // no shadow
+	})
 	debug := debugPrefix("fs=%s", fs.fs.ReportInfo().Name)
 	fs.planning.done = true
 	if err != nil {
@@ -449,7 +506,8 @@ func (fs *fs) do(ctx context.Context, pq *stepQueue, prev *fs) {
 		// lock must not be held while executing step in order for reporting to work
 		fs.l.DropWhile(func() {
 			targetDate := s.step.TargetDate()
-			defer pq.WaitReady(fs, targetDate)()
+			ctx, done := pq.WaitReady(ctx, fs, targetDate)()
+			defer done()
 			err = s.step.Step(ctx) // no shadow
 			errTime = time.Now()   // no shadow
 		})
@@ -470,6 +528,7 @@ func (r *run) report() *report.Report {
 		WaitReconnectSince: r.waitReconnect.begin,
 		WaitReconnectUntil: r.waitReconnect.end,
 		WaitReconnectError: r.waitReconnectError.IntoReportError(),
+		// Concurrency:        r.concurrency,
 	}
 	for i := range report.Attempts {
 		report.Attempts[i] = r.attempts[i].report()

replication/driver/replication_driver_test.go

@@ -151,7 +151,7 @@ func TestReplication(t *testing.T) {
 	ctx := context.Background()
 
 	mp := &mockPlanner{}
-	getReport, wait := Do(ctx, mp)
+	getReport, wait, _ := Do(ctx, 1, mp)
 	begin := time.Now()
 	fireAt := []time.Duration{
 		// the following values are relative to the start

replication/driver/replication_stepqueue.go

@@ -2,6 +2,8 @@ package driver
 
 import (
 	"container/heap"
+	"fmt"
+	"sync"
 	"time"
 
 	"github.com/zrepl/zrepl/util/chainlock"
@@ -11,51 +13,88 @@ type stepQueueRec struct {
 	ident      interface{}
 	targetDate time.Time
 	wakeup     chan StepCompletedFunc
+	cancelDueToConcurrencyDownsize interace{}
 }
 
 type stepQueue struct {
 	stop chan struct{}
 	reqs chan stepQueueRec
+
+	// l protects all members except the channels above
+
+	l           *chainlock.L
+	pendingCond *sync.Cond
+
+	// ident => queueItem
+	pending    *stepQueueHeap
+	active     *stepQueueHeap
+	queueItems map[interface{}]*stepQueueHeapItem // for tracking used idents in both pending and active
+
+	// stopped is used for cancellation of "wake" goroutine
+	stopped bool
+
+	concurrency int
 }
 
 type stepQueueHeapItem struct {
 	idx int
-	req stepQueueRec
+	req *stepQueueRec
+}
+type stepQueueHeap struct {
+	items   []*stepQueueHeapItem
+	reverse bool // never change after pushing first element
 }
-type stepQueueHeap []*stepQueueHeapItem
 
 func (h stepQueueHeap) Less(i, j int) bool {
-	return h[i].req.targetDate.Before(h[j].req.targetDate)
+	res := h.items[i].req.targetDate.Before(h.items[j].req.targetDate)
+	if h.reverse {
+		return !res
+	}
+	return res
 }
 
 func (h stepQueueHeap) Swap(i, j int) {
-	h[i], h[j] = h[j], h[i]
-	h[i].idx = i
-	h[j].idx = j
+	h.items[i], h.items[j] = h.items[j], h.items[i]
+	h.items[i].idx = i
+	h.items[j].idx = j
 }
 
 func (h stepQueueHeap) Len() int {
-	return len(h)
+	return len(h.items)
 }
 
 func (h *stepQueueHeap) Push(elem interface{}) {
 	hitem := elem.(*stepQueueHeapItem)
 	hitem.idx = h.Len()
-	*h = append(*h, hitem)
+	h.items = append(h.items, hitem)
 }
 
 func (h *stepQueueHeap) Pop() interface{} {
-	elem := (*h)[h.Len()-1]
+	elem := h.items[h.Len()-1]
 	elem.idx = -1
-	*h = (*h)[:h.Len()-1]
+	h.items = h.items[:h.Len()-1]
 	return elem
 }
 
 // returned stepQueue must be closed with method Close
-func newStepQueue() *stepQueue {
+func newStepQueue(concurrency int) *stepQueue {
+	l := chainlock.New()
 	q := &stepQueue{
-		stop: make(chan struct{}),
-		reqs: make(chan stepQueueRec),
+		stop:        make(chan struct{}),
+		reqs:        make(chan stepQueueRec),
+		l:           l,
+		pendingCond: l.NewCond(),
+		// priority queue
+		pending: &stepQueueHeap{reverse: false},
+		active:  &stepQueueHeap{reverse: true},
+		// ident => queueItem
+		queueItems: make(map[interface{}]*stepQueueHeapItem),
+		// stopped is used for cancellation of "wake" goroutine
+		stopped: false,
+	}
+	err := q.setConcurrencyLocked(concurrency)
+	if err != nil {
+		panic(err)
 	}
 	return q
 }
@@ -65,25 +104,12 @@ func newStepQueue() *stepQueue {
 //
 // No WaitReady calls must be active at the time done is called
 // The behavior of calling WaitReady after done was called is undefined
-func (q *stepQueue) Start(concurrency int) (done func()) {
-	if concurrency < 1 {
-		panic("concurrency must be >= 1")
-	}
-	// l protects pending and queueItems
-	l := chainlock.New()
-	pendingCond := l.NewCond()
-	// priority queue
-	pending := &stepQueueHeap{}
-	// ident => queueItem
-	queueItems := make(map[interface{}]*stepQueueHeapItem)
-	// stopped is used for cancellation of "wake" goroutine
-	stopped := false
-	active := 0
+func (q *stepQueue) Start() (done func()) {
 	go func() { // "stopper" goroutine
 		<-q.stop
-		defer l.Lock().Unlock()
-		stopped = true
-		pendingCond.Broadcast()
+		defer q.l.Lock().Unlock()
+		q.stopped = true
+		q.pendingCond.Broadcast()
 	}()
 	go func() { // "reqs" goroutine
 		for {
@@ -97,41 +123,52 @@ func (q *stepQueue) Start(concurrency int) (done func()) {
 				}
 			case req := <-q.reqs:
 				func() {
-					defer l.Lock().Unlock()
-					if _, ok := queueItems[req.ident]; ok {
+					defer q.l.Lock().Unlock()
+					if _, ok := q.queueItems[req.ident]; ok {
 						panic("WaitReady must not be called twice for the same ident")
 					}
 					qitem := &stepQueueHeapItem{
 						req: req,
 					}
-					queueItems[req.ident] = qitem
-					heap.Push(pending, qitem)
-					pendingCond.Broadcast()
+					q.queueItems[req.ident] = qitem
+					heap.Push(q.pending, qitem)
+					q.pendingCond.Broadcast()
 				}()
 			}
 		}
 	}()
 	go func() { // "wake" goroutine
-		defer l.Lock().Unlock()
+		defer q.l.Lock().Unlock()
 		for {
 
-			for !stopped && (active >= concurrency || pending.Len() == 0) {
-				pendingCond.Wait()
+			for !q.stopped && (q.active.Len() >= q.concurrency || q.pending.Len() == 0) {
+				q.pendingCond.Wait()
 			}
-			if stopped {
+			if q.stopped {
 				return
 			}
-			if pending.Len() <= 0 {
+			if q.pending.Len() <= 0 {
 				return
 			}
-			active++
-			next := heap.Pop(pending).(*stepQueueHeapItem).req
-			delete(queueItems, next.ident)
 
-			next.wakeup <- func() {
-				defer l.Lock().Unlock()
-				active--
-				pendingCond.Broadcast()
+			// pop from tracked items
+			next := heap.Pop(q.pending).(*stepQueueHeapItem)
+
+			next.req.cancelDueToConcurrencyDownsize = 
+
+			heap.Push(q.active, next)
+
+			next.req.wakeup <- func() {
+				defer q.l.Lock().Unlock()
+
+				//
+				qitem := &stepQueueHeapItem{
+					req: req,
+				}
+
+				// delete(q.queueItems, next.req.ident) // def
+
+				q.pendingCond.Broadcast()
 			}
 		}
 	}()
@@ -161,3 +198,24 @@ func (q *stepQueue) WaitReady(ident interface{}, targetDate time.Time) StepCompl
 	}
 	return q.sendAndWaitForWakeup(ident, targetDate)
 }
+
+// caller must hold lock
+func (q *stepQueue) setConcurrencyLocked(newConcurrency int) error {
+	if !(newConcurrency >= 1) {
+		return fmt.Errorf("concurrency must be >= 1 but requested %v", newConcurrency)
+	}
+	q.concurrency = newConcurrency
+	q.pendingCond.Broadcast() // wake up waiters who could make progress
+
+	for q.active.Len() > q.concurrency {
+		item := heap.Pop(q.active).(*stepQueueHeapItem)
+		item.req.cancelDueToConcurrencyDownsize()
+		heap.Push(q.pending, item)
+	}
+	return nil
+}
+
+func (q *stepQueue) SetConcurrency(new int) error {
+	defer q.l.Lock().Unlock()
+	return q.setConcurrencyLocked(new)
+}

replication/driver/replication_stepqueue_test.go

@@ -17,7 +17,7 @@ import (
 // (relies on scheduler responsivity of < 500ms)
 func TestPqNotconcurrent(t *testing.T) {
 	var ctr uint32
-	q := newStepQueue()
+	q := newStepQueue(1)
 	var wg sync.WaitGroup
 	wg.Add(4)
 	go func() {
@@ -29,7 +29,7 @@ func TestPqNotconcurrent(t *testing.T) {
 	}()
 
 	// give goroutine "1" 500ms to enter queue, get the active slot and enter time.Sleep
-	defer q.Start(1)()
+	defer q.Start()()
 	time.Sleep(500 * time.Millisecond)
 
 	// while "1" is still running, queue in "2", "3" and "4"
@@ -77,8 +77,9 @@ func (r record) String() string {
 // Hence, perform some statistics on the wakeup times and assert that the mean wakeup
 // times for each step are close together.
 func TestPqConcurrent(t *testing.T) {
-
-	q := newStepQueue()
+	
+	concurrency := 5
+	q := newStepQueue(concurrency)
 	var wg sync.WaitGroup
 	filesystems := 100
 	stepsPerFS := 20
@@ -104,8 +105,7 @@ func TestPqConcurrent(t *testing.T) {
 			records <- recs
 		}(fs)
 	}
-	concurrency := 5
-	defer q.Start(concurrency)()
+	defer q.Start()()
 	wg.Wait()
 	close(records)
 	t.Logf("loop done")

replication/logic/pdu/pdu.pb.go

@@ -23,6 +23,32 @@ var _ = math.Inf
 // proto package needs to be updated.
 const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
 
+type Tri int32
+
+const (
+	Tri_DontCare Tri = 0
+	Tri_False    Tri = 1
+	Tri_True     Tri = 2
+)
+
+var Tri_name = map[int32]string{
+	0: "DontCare",
+	1: "False",
+	2: "True",
+}
+var Tri_value = map[string]int32{
+	"DontCare": 0,
+	"False":    1,
+	"True":     2,
+}
+
+func (x Tri) String() string {
+	return proto.EnumName(Tri_name, int32(x))
+}
+func (Tri) EnumDescriptor() ([]byte, []int) {
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{0}
+}
+
 type FilesystemVersion_VersionType int32
 
 const (
@@ -43,7 +69,7 @@ func (x FilesystemVersion_VersionType) String() string {
 	return proto.EnumName(FilesystemVersion_VersionType_name, int32(x))
 }
 func (FilesystemVersion_VersionType) EnumDescriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{5, 0}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{5, 0}
 }
 
 type ListFilesystemReq struct {
@@ -56,7 +82,7 @@ func (m *ListFilesystemReq) Reset()         { *m = ListFilesystemReq{} }
 func (m *ListFilesystemReq) String() string { return proto.CompactTextString(m) }
 func (*ListFilesystemReq) ProtoMessage()    {}
 func (*ListFilesystemReq) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{0}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{0}
 }
 func (m *ListFilesystemReq) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ListFilesystemReq.Unmarshal(m, b)
@@ -87,7 +113,7 @@ func (m *ListFilesystemRes) Reset()         { *m = ListFilesystemRes{} }
 func (m *ListFilesystemRes) String() string { return proto.CompactTextString(m) }
 func (*ListFilesystemRes) ProtoMessage()    {}
 func (*ListFilesystemRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{1}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{1}
 }
 func (m *ListFilesystemRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ListFilesystemRes.Unmarshal(m, b)
@@ -118,6 +144,7 @@ type Filesystem struct {
 	Path                 string   `protobuf:"bytes,1,opt,name=Path,proto3" json:"Path,omitempty"`
 	ResumeToken          string   `protobuf:"bytes,2,opt,name=ResumeToken,proto3" json:"ResumeToken,omitempty"`
 	IsPlaceholder        bool     `protobuf:"varint,3,opt,name=IsPlaceholder,proto3" json:"IsPlaceholder,omitempty"`
+	IsEncrypted          bool     `protobuf:"varint,4,opt,name=IsEncrypted,proto3" json:"IsEncrypted,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -127,7 +154,7 @@ func (m *Filesystem) Reset()         { *m = Filesystem{} }
 func (m *Filesystem) String() string { return proto.CompactTextString(m) }
 func (*Filesystem) ProtoMessage()    {}
 func (*Filesystem) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{2}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{2}
 }
 func (m *Filesystem) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Filesystem.Unmarshal(m, b)
@@ -168,6 +195,13 @@ func (m *Filesystem) GetIsPlaceholder() bool {
 	return false
 }
 
+func (m *Filesystem) GetIsEncrypted() bool {
+	if m != nil {
+		return m.IsEncrypted
+	}
+	return false
+}
+
 type ListFilesystemVersionsReq struct {
 	Filesystem           string   `protobuf:"bytes,1,opt,name=Filesystem,proto3" json:"Filesystem,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
@@ -179,7 +213,7 @@ func (m *ListFilesystemVersionsReq) Reset()         { *m = ListFilesystemVersion
 func (m *ListFilesystemVersionsReq) String() string { return proto.CompactTextString(m) }
 func (*ListFilesystemVersionsReq) ProtoMessage()    {}
 func (*ListFilesystemVersionsReq) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{3}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{3}
 }
 func (m *ListFilesystemVersionsReq) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ListFilesystemVersionsReq.Unmarshal(m, b)
@@ -217,7 +251,7 @@ func (m *ListFilesystemVersionsRes) Reset()         { *m = ListFilesystemVersion
 func (m *ListFilesystemVersionsRes) String() string { return proto.CompactTextString(m) }
 func (*ListFilesystemVersionsRes) ProtoMessage()    {}
 func (*ListFilesystemVersionsRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{4}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{4}
 }
 func (m *ListFilesystemVersionsRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ListFilesystemVersionsRes.Unmarshal(m, b)
@@ -259,7 +293,7 @@ func (m *FilesystemVersion) Reset()         { *m = FilesystemVersion{} }
 func (m *FilesystemVersion) String() string { return proto.CompactTextString(m) }
 func (*FilesystemVersion) ProtoMessage()    {}
 func (*FilesystemVersion) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{5}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{5}
 }
 func (m *FilesystemVersion) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FilesystemVersion.Unmarshal(m, b)
@@ -316,20 +350,18 @@ func (m *FilesystemVersion) GetCreation() string {
 
 type SendReq struct {
 	Filesystem string `protobuf:"bytes,1,opt,name=Filesystem,proto3" json:"Filesystem,omitempty"`
-	From       string `protobuf:"bytes,2,opt,name=From,proto3" json:"From,omitempty"`
-	// May be empty / null to request a full transfer of From
-	To string `protobuf:"bytes,3,opt,name=To,proto3" json:"To,omitempty"`
-	// If ResumeToken is not empty, the resume token that CAN be tried for 'zfs send' by the sender.
-	// The sender MUST indicate in SendRes.UsedResumeToken
-	// If it does not work, the sender SHOULD clear the resume token on their side
-	// and use From and To instead
-	// If ResumeToken is not empty, the GUIDs of From and To
-	// MUST correspond to those encoded in the ResumeToken.
-	// Otherwise, the Sender MUST return an error.
+	// May be empty / null to request a full transfer of To
+	From *FilesystemVersion `protobuf:"bytes,2,opt,name=From,proto3" json:"From,omitempty"`
+	To   *FilesystemVersion `protobuf:"bytes,3,opt,name=To,proto3" json:"To,omitempty"`
+	// If ResumeToken is not empty, the resume token that CAN be used for 'zfs
+	// send' by the sender. The sender MUST indicate use of ResumeToken in the
+	// reply message SendRes.UsedResumeToken If it does not work, the sender
+	// SHOULD clear the resume token on their side and use From and To instead If
+	// ResumeToken is not empty, the GUIDs of From and To MUST correspond to those
+	// encoded in the ResumeToken. Otherwise, the Sender MUST return an error.
 	ResumeToken          string   `protobuf:"bytes,4,opt,name=ResumeToken,proto3" json:"ResumeToken,omitempty"`
-	Compress             bool     `protobuf:"varint,5,opt,name=Compress,proto3" json:"Compress,omitempty"`
-	Dedup                bool     `protobuf:"varint,6,opt,name=Dedup,proto3" json:"Dedup,omitempty"`
-	DryRun               bool     `protobuf:"varint,7,opt,name=DryRun,proto3" json:"DryRun,omitempty"`
+	Encrypted            Tri      `protobuf:"varint,5,opt,name=Encrypted,proto3,enum=Tri" json:"Encrypted,omitempty"`
+	DryRun               bool     `protobuf:"varint,6,opt,name=DryRun,proto3" json:"DryRun,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -339,7 +371,7 @@ func (m *SendReq) Reset()         { *m = SendReq{} }
 func (m *SendReq) String() string { return proto.CompactTextString(m) }
 func (*SendReq) ProtoMessage()    {}
 func (*SendReq) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{6}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{6}
 }
 func (m *SendReq) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_SendReq.Unmarshal(m, b)
@@ -366,18 +398,18 @@ func (m *SendReq) GetFilesystem() string {
 	return ""
 }
 
-func (m *SendReq) GetFrom() string {
+func (m *SendReq) GetFrom() *FilesystemVersion {
 	if m != nil {
 		return m.From
 	}
-	return ""
+	return nil
 }
 
-func (m *SendReq) GetTo() string {
+func (m *SendReq) GetTo() *FilesystemVersion {
 	if m != nil {
 		return m.To
 	}
-	return ""
+	return nil
 }
 
 func (m *SendReq) GetResumeToken() string {
@@ -387,18 +419,11 @@ func (m *SendReq) GetResumeToken() string {
 	return ""
 }
 
-func (m *SendReq) GetCompress() bool {
+func (m *SendReq) GetEncrypted() Tri {
 	if m != nil {
-		return m.Compress
+		return m.Encrypted
 	}
-	return false
-}
-
-func (m *SendReq) GetDedup() bool {
-	if m != nil {
-		return m.Dedup
-	}
-	return false
+	return Tri_DontCare
 }
 
 func (m *SendReq) GetDryRun() bool {
@@ -420,7 +445,7 @@ func (m *Property) Reset()         { *m = Property{} }
 func (m *Property) String() string { return proto.CompactTextString(m) }
 func (*Property) ProtoMessage()    {}
 func (*Property) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{7}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{7}
 }
 func (m *Property) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Property.Unmarshal(m, b)
@@ -456,6 +481,7 @@ func (m *Property) GetValue() string {
 
 type SendRes struct {
 	// Whether the resume token provided in the request has been used or not.
+	// If the SendReq.ResumeToken == "", this field has no meaning.
 	UsedResumeToken bool `protobuf:"varint,2,opt,name=UsedResumeToken,proto3" json:"UsedResumeToken,omitempty"`
 	// Expected stream size determined by dry run, not exact.
 	// 0 indicates that for the given SendReq, no size estimate could be made.
@@ -470,7 +496,7 @@ func (m *SendRes) Reset()         { *m = SendRes{} }
 func (m *SendRes) String() string { return proto.CompactTextString(m) }
 func (*SendRes) ProtoMessage()    {}
 func (*SendRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{8}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{8}
 }
 func (m *SendRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_SendRes.Unmarshal(m, b)
@@ -511,10 +537,80 @@ func (m *SendRes) GetProperties() []*Property {
 	return nil
 }
 
+type SendCompletedReq struct {
+	OriginalReq          *SendReq `protobuf:"bytes,2,opt,name=OriginalReq,proto3" json:"OriginalReq,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *SendCompletedReq) Reset()         { *m = SendCompletedReq{} }
+func (m *SendCompletedReq) String() string { return proto.CompactTextString(m) }
+func (*SendCompletedReq) ProtoMessage()    {}
+func (*SendCompletedReq) Descriptor() ([]byte, []int) {
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{9}
+}
+func (m *SendCompletedReq) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_SendCompletedReq.Unmarshal(m, b)
+}
+func (m *SendCompletedReq) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_SendCompletedReq.Marshal(b, m, deterministic)
+}
+func (dst *SendCompletedReq) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_SendCompletedReq.Merge(dst, src)
+}
+func (m *SendCompletedReq) XXX_Size() int {
+	return xxx_messageInfo_SendCompletedReq.Size(m)
+}
+func (m *SendCompletedReq) XXX_DiscardUnknown() {
+	xxx_messageInfo_SendCompletedReq.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_SendCompletedReq proto.InternalMessageInfo
+
+func (m *SendCompletedReq) GetOriginalReq() *SendReq {
+	if m != nil {
+		return m.OriginalReq
+	}
+	return nil
+}
+
+type SendCompletedRes struct {
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *SendCompletedRes) Reset()         { *m = SendCompletedRes{} }
+func (m *SendCompletedRes) String() string { return proto.CompactTextString(m) }
+func (*SendCompletedRes) ProtoMessage()    {}
+func (*SendCompletedRes) Descriptor() ([]byte, []int) {
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{10}
+}
+func (m *SendCompletedRes) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_SendCompletedRes.Unmarshal(m, b)
+}
+func (m *SendCompletedRes) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_SendCompletedRes.Marshal(b, m, deterministic)
+}
+func (dst *SendCompletedRes) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_SendCompletedRes.Merge(dst, src)
+}
+func (m *SendCompletedRes) XXX_Size() int {
+	return xxx_messageInfo_SendCompletedRes.Size(m)
+}
+func (m *SendCompletedRes) XXX_DiscardUnknown() {
+	xxx_messageInfo_SendCompletedRes.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_SendCompletedRes proto.InternalMessageInfo
+
 type ReceiveReq struct {
-	Filesystem string `protobuf:"bytes,1,opt,name=Filesystem,proto3" json:"Filesystem,omitempty"`
-	// If true, the receiver should clear the resume token before perfoming the zfs recv of the stream in the request
-	ClearResumeToken     bool     `protobuf:"varint,2,opt,name=ClearResumeToken,proto3" json:"ClearResumeToken,omitempty"`
+	Filesystem string             `protobuf:"bytes,1,opt,name=Filesystem,proto3" json:"Filesystem,omitempty"`
+	To         *FilesystemVersion `protobuf:"bytes,2,opt,name=To,proto3" json:"To,omitempty"`
+	// If true, the receiver should clear the resume token before perfoming the
+	// zfs recv of the stream in the request
+	ClearResumeToken     bool     `protobuf:"varint,3,opt,name=ClearResumeToken,proto3" json:"ClearResumeToken,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -524,7 +620,7 @@ func (m *ReceiveReq) Reset()         { *m = ReceiveReq{} }
 func (m *ReceiveReq) String() string { return proto.CompactTextString(m) }
 func (*ReceiveReq) ProtoMessage()    {}
 func (*ReceiveReq) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{9}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{11}
 }
 func (m *ReceiveReq) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ReceiveReq.Unmarshal(m, b)
@@ -551,6 +647,13 @@ func (m *ReceiveReq) GetFilesystem() string {
 	return ""
 }
 
+func (m *ReceiveReq) GetTo() *FilesystemVersion {
+	if m != nil {
+		return m.To
+	}
+	return nil
+}
+
 func (m *ReceiveReq) GetClearResumeToken() bool {
 	if m != nil {
 		return m.ClearResumeToken
@@ -568,7 +671,7 @@ func (m *ReceiveRes) Reset()         { *m = ReceiveRes{} }
 func (m *ReceiveRes) String() string { return proto.CompactTextString(m) }
 func (*ReceiveRes) ProtoMessage()    {}
 func (*ReceiveRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{10}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{12}
 }
 func (m *ReceiveRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ReceiveRes.Unmarshal(m, b)
@@ -601,7 +704,7 @@ func (m *DestroySnapshotsReq) Reset()         { *m = DestroySnapshotsReq{} }
 func (m *DestroySnapshotsReq) String() string { return proto.CompactTextString(m) }
 func (*DestroySnapshotsReq) ProtoMessage()    {}
 func (*DestroySnapshotsReq) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{11}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{13}
 }
 func (m *DestroySnapshotsReq) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_DestroySnapshotsReq.Unmarshal(m, b)
@@ -647,7 +750,7 @@ func (m *DestroySnapshotRes) Reset()         { *m = DestroySnapshotRes{} }
 func (m *DestroySnapshotRes) String() string { return proto.CompactTextString(m) }
 func (*DestroySnapshotRes) ProtoMessage()    {}
 func (*DestroySnapshotRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{12}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{14}
 }
 func (m *DestroySnapshotRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_DestroySnapshotRes.Unmarshal(m, b)
@@ -692,7 +795,7 @@ func (m *DestroySnapshotsRes) Reset()         { *m = DestroySnapshotsRes{} }
 func (m *DestroySnapshotsRes) String() string { return proto.CompactTextString(m) }
 func (*DestroySnapshotsRes) ProtoMessage()    {}
 func (*DestroySnapshotsRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{13}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{15}
 }
 func (m *DestroySnapshotsRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_DestroySnapshotsRes.Unmarshal(m, b)
@@ -720,21 +823,17 @@ func (m *DestroySnapshotsRes) GetResults() []*DestroySnapshotRes {
 }
 
 type ReplicationCursorReq struct {
-	Filesystem string `protobuf:"bytes,1,opt,name=Filesystem,proto3" json:"Filesystem,omitempty"`
-	// Types that are valid to be assigned to Op:
-	//	*ReplicationCursorReq_Get
-	//	*ReplicationCursorReq_Set
-	Op                   isReplicationCursorReq_Op `protobuf_oneof:"op"`
-	XXX_NoUnkeyedLiteral struct{}                  `json:"-"`
-	XXX_unrecognized     []byte                    `json:"-"`
-	XXX_sizecache        int32                     `json:"-"`
+	Filesystem           string   `protobuf:"bytes,1,opt,name=Filesystem,proto3" json:"Filesystem,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
 }
 
 func (m *ReplicationCursorReq) Reset()         { *m = ReplicationCursorReq{} }
 func (m *ReplicationCursorReq) String() string { return proto.CompactTextString(m) }
 func (*ReplicationCursorReq) ProtoMessage()    {}
 func (*ReplicationCursorReq) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{14}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{16}
 }
 func (m *ReplicationCursorReq) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ReplicationCursorReq.Unmarshal(m, b)
@@ -761,185 +860,6 @@ func (m *ReplicationCursorReq) GetFilesystem() string {
 	return ""
 }
 
-type isReplicationCursorReq_Op interface {
-	isReplicationCursorReq_Op()
-}
-
-type ReplicationCursorReq_Get struct {
-	Get *ReplicationCursorReq_GetOp `protobuf:"bytes,2,opt,name=get,proto3,oneof"`
-}
-
-type ReplicationCursorReq_Set struct {
-	Set *ReplicationCursorReq_SetOp `protobuf:"bytes,3,opt,name=set,proto3,oneof"`
-}
-
-func (*ReplicationCursorReq_Get) isReplicationCursorReq_Op() {}
-
-func (*ReplicationCursorReq_Set) isReplicationCursorReq_Op() {}
-
-func (m *ReplicationCursorReq) GetOp() isReplicationCursorReq_Op {
-	if m != nil {
-		return m.Op
-	}
-	return nil
-}
-
-func (m *ReplicationCursorReq) GetGet() *ReplicationCursorReq_GetOp {
-	if x, ok := m.GetOp().(*ReplicationCursorReq_Get); ok {
-		return x.Get
-	}
-	return nil
-}
-
-func (m *ReplicationCursorReq) GetSet() *ReplicationCursorReq_SetOp {
-	if x, ok := m.GetOp().(*ReplicationCursorReq_Set); ok {
-		return x.Set
-	}
-	return nil
-}
-
-// XXX_OneofFuncs is for the internal use of the proto package.
-func (*ReplicationCursorReq) XXX_OneofFuncs() (func(msg proto.Message, b *proto.Buffer) error, func(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error), func(msg proto.Message) (n int), []interface{}) {
-	return _ReplicationCursorReq_OneofMarshaler, _ReplicationCursorReq_OneofUnmarshaler, _ReplicationCursorReq_OneofSizer, []interface{}{
-		(*ReplicationCursorReq_Get)(nil),
-		(*ReplicationCursorReq_Set)(nil),
-	}
-}
-
-func _ReplicationCursorReq_OneofMarshaler(msg proto.Message, b *proto.Buffer) error {
-	m := msg.(*ReplicationCursorReq)
-	// op
-	switch x := m.Op.(type) {
-	case *ReplicationCursorReq_Get:
-		b.EncodeVarint(2<<3 | proto.WireBytes)
-		if err := b.EncodeMessage(x.Get); err != nil {
-			return err
-		}
-	case *ReplicationCursorReq_Set:
-		b.EncodeVarint(3<<3 | proto.WireBytes)
-		if err := b.EncodeMessage(x.Set); err != nil {
-			return err
-		}
-	case nil:
-	default:
-		return fmt.Errorf("ReplicationCursorReq.Op has unexpected type %T", x)
-	}
-	return nil
-}
-
-func _ReplicationCursorReq_OneofUnmarshaler(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error) {
-	m := msg.(*ReplicationCursorReq)
-	switch tag {
-	case 2: // op.get
-		if wire != proto.WireBytes {
-			return true, proto.ErrInternalBadWireType
-		}
-		msg := new(ReplicationCursorReq_GetOp)
-		err := b.DecodeMessage(msg)
-		m.Op = &ReplicationCursorReq_Get{msg}
-		return true, err
-	case 3: // op.set
-		if wire != proto.WireBytes {
-			return true, proto.ErrInternalBadWireType
-		}
-		msg := new(ReplicationCursorReq_SetOp)
-		err := b.DecodeMessage(msg)
-		m.Op = &ReplicationCursorReq_Set{msg}
-		return true, err
-	default:
-		return false, nil
-	}
-}
-
-func _ReplicationCursorReq_OneofSizer(msg proto.Message) (n int) {
-	m := msg.(*ReplicationCursorReq)
-	// op
-	switch x := m.Op.(type) {
-	case *ReplicationCursorReq_Get:
-		s := proto.Size(x.Get)
-		n += 1 // tag and wire
-		n += proto.SizeVarint(uint64(s))
-		n += s
-	case *ReplicationCursorReq_Set:
-		s := proto.Size(x.Set)
-		n += 1 // tag and wire
-		n += proto.SizeVarint(uint64(s))
-		n += s
-	case nil:
-	default:
-		panic(fmt.Sprintf("proto: unexpected type %T in oneof", x))
-	}
-	return n
-}
-
-type ReplicationCursorReq_GetOp struct {
-	XXX_NoUnkeyedLiteral struct{} `json:"-"`
-	XXX_unrecognized     []byte   `json:"-"`
-	XXX_sizecache        int32    `json:"-"`
-}
-
-func (m *ReplicationCursorReq_GetOp) Reset()         { *m = ReplicationCursorReq_GetOp{} }
-func (m *ReplicationCursorReq_GetOp) String() string { return proto.CompactTextString(m) }
-func (*ReplicationCursorReq_GetOp) ProtoMessage()    {}
-func (*ReplicationCursorReq_GetOp) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{14, 0}
-}
-func (m *ReplicationCursorReq_GetOp) XXX_Unmarshal(b []byte) error {
-	return xxx_messageInfo_ReplicationCursorReq_GetOp.Unmarshal(m, b)
-}
-func (m *ReplicationCursorReq_GetOp) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	return xxx_messageInfo_ReplicationCursorReq_GetOp.Marshal(b, m, deterministic)
-}
-func (dst *ReplicationCursorReq_GetOp) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_ReplicationCursorReq_GetOp.Merge(dst, src)
-}
-func (m *ReplicationCursorReq_GetOp) XXX_Size() int {
-	return xxx_messageInfo_ReplicationCursorReq_GetOp.Size(m)
-}
-func (m *ReplicationCursorReq_GetOp) XXX_DiscardUnknown() {
-	xxx_messageInfo_ReplicationCursorReq_GetOp.DiscardUnknown(m)
-}
-
-var xxx_messageInfo_ReplicationCursorReq_GetOp proto.InternalMessageInfo
-
-type ReplicationCursorReq_SetOp struct {
-	Snapshot             string   `protobuf:"bytes,2,opt,name=Snapshot,proto3" json:"Snapshot,omitempty"`
-	XXX_NoUnkeyedLiteral struct{} `json:"-"`
-	XXX_unrecognized     []byte   `json:"-"`
-	XXX_sizecache        int32    `json:"-"`
-}
-
-func (m *ReplicationCursorReq_SetOp) Reset()         { *m = ReplicationCursorReq_SetOp{} }
-func (m *ReplicationCursorReq_SetOp) String() string { return proto.CompactTextString(m) }
-func (*ReplicationCursorReq_SetOp) ProtoMessage()    {}
-func (*ReplicationCursorReq_SetOp) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{14, 1}
-}
-func (m *ReplicationCursorReq_SetOp) XXX_Unmarshal(b []byte) error {
-	return xxx_messageInfo_ReplicationCursorReq_SetOp.Unmarshal(m, b)
-}
-func (m *ReplicationCursorReq_SetOp) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	return xxx_messageInfo_ReplicationCursorReq_SetOp.Marshal(b, m, deterministic)
-}
-func (dst *ReplicationCursorReq_SetOp) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_ReplicationCursorReq_SetOp.Merge(dst, src)
-}
-func (m *ReplicationCursorReq_SetOp) XXX_Size() int {
-	return xxx_messageInfo_ReplicationCursorReq_SetOp.Size(m)
-}
-func (m *ReplicationCursorReq_SetOp) XXX_DiscardUnknown() {
-	xxx_messageInfo_ReplicationCursorReq_SetOp.DiscardUnknown(m)
-}
-
-var xxx_messageInfo_ReplicationCursorReq_SetOp proto.InternalMessageInfo
-
-func (m *ReplicationCursorReq_SetOp) GetSnapshot() string {
-	if m != nil {
-		return m.Snapshot
-	}
-	return ""
-}
-
 type ReplicationCursorRes struct {
 	// Types that are valid to be assigned to Result:
 	//	*ReplicationCursorRes_Guid
@@ -954,7 +874,7 @@ func (m *ReplicationCursorRes) Reset()         { *m = ReplicationCursorRes{} }
 func (m *ReplicationCursorRes) String() string { return proto.CompactTextString(m) }
 func (*ReplicationCursorRes) ProtoMessage()    {}
 func (*ReplicationCursorRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{15}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{17}
 }
 func (m *ReplicationCursorRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ReplicationCursorRes.Unmarshal(m, b)
@@ -1090,7 +1010,7 @@ func (m *PingReq) Reset()         { *m = PingReq{} }
 func (m *PingReq) String() string { return proto.CompactTextString(m) }
 func (*PingReq) ProtoMessage()    {}
 func (*PingReq) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{16}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{18}
 }
 func (m *PingReq) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_PingReq.Unmarshal(m, b)
@@ -1129,7 +1049,7 @@ func (m *PingRes) Reset()         { *m = PingRes{} }
 func (m *PingRes) String() string { return proto.CompactTextString(m) }
 func (*PingRes) ProtoMessage()    {}
 func (*PingRes) Descriptor() ([]byte, []int) {
-	return fileDescriptor_pdu_83b7e2a28d820622, []int{17}
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{19}
 }
 func (m *PingRes) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_PingRes.Unmarshal(m, b)
@@ -1156,6 +1076,82 @@ func (m *PingRes) GetEcho() string {
 	return ""
 }
 
+type HintMostRecentCommonAncestorReq struct {
+	Filesystem           string             `protobuf:"bytes,1,opt,name=Filesystem,proto3" json:"Filesystem,omitempty"`
+	SenderVersion        *FilesystemVersion `protobuf:"bytes,2,opt,name=SenderVersion,proto3" json:"SenderVersion,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}           `json:"-"`
+	XXX_unrecognized     []byte             `json:"-"`
+	XXX_sizecache        int32              `json:"-"`
+}
+
+func (m *HintMostRecentCommonAncestorReq) Reset()         { *m = HintMostRecentCommonAncestorReq{} }
+func (m *HintMostRecentCommonAncestorReq) String() string { return proto.CompactTextString(m) }
+func (*HintMostRecentCommonAncestorReq) ProtoMessage()    {}
+func (*HintMostRecentCommonAncestorReq) Descriptor() ([]byte, []int) {
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{20}
+}
+func (m *HintMostRecentCommonAncestorReq) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_HintMostRecentCommonAncestorReq.Unmarshal(m, b)
+}
+func (m *HintMostRecentCommonAncestorReq) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_HintMostRecentCommonAncestorReq.Marshal(b, m, deterministic)
+}
+func (dst *HintMostRecentCommonAncestorReq) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_HintMostRecentCommonAncestorReq.Merge(dst, src)
+}
+func (m *HintMostRecentCommonAncestorReq) XXX_Size() int {
+	return xxx_messageInfo_HintMostRecentCommonAncestorReq.Size(m)
+}
+func (m *HintMostRecentCommonAncestorReq) XXX_DiscardUnknown() {
+	xxx_messageInfo_HintMostRecentCommonAncestorReq.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_HintMostRecentCommonAncestorReq proto.InternalMessageInfo
+
+func (m *HintMostRecentCommonAncestorReq) GetFilesystem() string {
+	if m != nil {
+		return m.Filesystem
+	}
+	return ""
+}
+
+func (m *HintMostRecentCommonAncestorReq) GetSenderVersion() *FilesystemVersion {
+	if m != nil {
+		return m.SenderVersion
+	}
+	return nil
+}
+
+type HintMostRecentCommonAncestorRes struct {
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *HintMostRecentCommonAncestorRes) Reset()         { *m = HintMostRecentCommonAncestorRes{} }
+func (m *HintMostRecentCommonAncestorRes) String() string { return proto.CompactTextString(m) }
+func (*HintMostRecentCommonAncestorRes) ProtoMessage()    {}
+func (*HintMostRecentCommonAncestorRes) Descriptor() ([]byte, []int) {
+	return fileDescriptor_pdu_0f43b713cd3bf056, []int{21}
+}
+func (m *HintMostRecentCommonAncestorRes) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_HintMostRecentCommonAncestorRes.Unmarshal(m, b)
+}
+func (m *HintMostRecentCommonAncestorRes) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_HintMostRecentCommonAncestorRes.Marshal(b, m, deterministic)
+}
+func (dst *HintMostRecentCommonAncestorRes) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_HintMostRecentCommonAncestorRes.Merge(dst, src)
+}
+func (m *HintMostRecentCommonAncestorRes) XXX_Size() int {
+	return xxx_messageInfo_HintMostRecentCommonAncestorRes.Size(m)
+}
+func (m *HintMostRecentCommonAncestorRes) XXX_DiscardUnknown() {
+	xxx_messageInfo_HintMostRecentCommonAncestorRes.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_HintMostRecentCommonAncestorRes proto.InternalMessageInfo
+
 func init() {
 	proto.RegisterType((*ListFilesystemReq)(nil), "ListFilesystemReq")
 	proto.RegisterType((*ListFilesystemRes)(nil), "ListFilesystemRes")
@@ -1166,17 +1162,20 @@ func init() {
 	proto.RegisterType((*SendReq)(nil), "SendReq")
 	proto.RegisterType((*Property)(nil), "Property")
 	proto.RegisterType((*SendRes)(nil), "SendRes")
+	proto.RegisterType((*SendCompletedReq)(nil), "SendCompletedReq")
+	proto.RegisterType((*SendCompletedRes)(nil), "SendCompletedRes")
 	proto.RegisterType((*ReceiveReq)(nil), "ReceiveReq")
 	proto.RegisterType((*ReceiveRes)(nil), "ReceiveRes")
 	proto.RegisterType((*DestroySnapshotsReq)(nil), "DestroySnapshotsReq")
 	proto.RegisterType((*DestroySnapshotRes)(nil), "DestroySnapshotRes")
 	proto.RegisterType((*DestroySnapshotsRes)(nil), "DestroySnapshotsRes")
 	proto.RegisterType((*ReplicationCursorReq)(nil), "ReplicationCursorReq")
-	proto.RegisterType((*ReplicationCursorReq_GetOp)(nil), "ReplicationCursorReq.GetOp")
-	proto.RegisterType((*ReplicationCursorReq_SetOp)(nil), "ReplicationCursorReq.SetOp")
 	proto.RegisterType((*ReplicationCursorRes)(nil), "ReplicationCursorRes")
 	proto.RegisterType((*PingReq)(nil), "PingReq")
 	proto.RegisterType((*PingRes)(nil), "PingRes")
+	proto.RegisterType((*HintMostRecentCommonAncestorReq)(nil), "HintMostRecentCommonAncestorReq")
+	proto.RegisterType((*HintMostRecentCommonAncestorRes)(nil), "HintMostRecentCommonAncestorRes")
+	proto.RegisterEnum("Tri", Tri_name, Tri_value)
 	proto.RegisterEnum("FilesystemVersion_VersionType", FilesystemVersion_VersionType_name, FilesystemVersion_VersionType_value)
 }
 
@@ -1197,6 +1196,8 @@ type ReplicationClient interface {
 	ListFilesystemVersions(ctx context.Context, in *ListFilesystemVersionsReq, opts ...grpc.CallOption) (*ListFilesystemVersionsRes, error)
 	DestroySnapshots(ctx context.Context, in *DestroySnapshotsReq, opts ...grpc.CallOption) (*DestroySnapshotsRes, error)
 	ReplicationCursor(ctx context.Context, in *ReplicationCursorReq, opts ...grpc.CallOption) (*ReplicationCursorRes, error)
+	SendCompleted(ctx context.Context, in *SendCompletedReq, opts ...grpc.CallOption) (*SendCompletedRes, error)
+	HintMostRecentCommonAncestor(ctx context.Context, in *HintMostRecentCommonAncestorReq, opts ...grpc.CallOption) (*HintMostRecentCommonAncestorRes, error)
 }
 
 type replicationClient struct {
@@ -1252,6 +1253,24 @@ func (c *replicationClient) ReplicationCursor(ctx context.Context, in *Replicati
 	return out, nil
 }
 
+func (c *replicationClient) SendCompleted(ctx context.Context, in *SendCompletedReq, opts ...grpc.CallOption) (*SendCompletedRes, error) {
+	out := new(SendCompletedRes)
+	err := c.cc.Invoke(ctx, "/Replication/SendCompleted", in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *replicationClient) HintMostRecentCommonAncestor(ctx context.Context, in *HintMostRecentCommonAncestorReq, opts ...grpc.CallOption) (*HintMostRecentCommonAncestorRes, error) {
+	out := new(HintMostRecentCommonAncestorRes)
+	err := c.cc.Invoke(ctx, "/Replication/HintMostRecentCommonAncestor", in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // ReplicationServer is the server API for Replication service.
 type ReplicationServer interface {
 	Ping(context.Context, *PingReq) (*PingRes, error)
@@ -1259,6 +1278,8 @@ type ReplicationServer interface {
 	ListFilesystemVersions(context.Context, *ListFilesystemVersionsReq) (*ListFilesystemVersionsRes, error)
 	DestroySnapshots(context.Context, *DestroySnapshotsReq) (*DestroySnapshotsRes, error)
 	ReplicationCursor(context.Context, *ReplicationCursorReq) (*ReplicationCursorRes, error)
+	SendCompleted(context.Context, *SendCompletedReq) (*SendCompletedRes, error)
+	HintMostRecentCommonAncestor(context.Context, *HintMostRecentCommonAncestorReq) (*HintMostRecentCommonAncestorRes, error)
 }
 
 func RegisterReplicationServer(s *grpc.Server, srv ReplicationServer) {
@@ -1355,6 +1376,42 @@ func _Replication_ReplicationCursor_Handler(srv interface{}, ctx context.Context
 	return interceptor(ctx, in, info, handler)
 }
 
+func _Replication_SendCompleted_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(SendCompletedReq)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(ReplicationServer).SendCompleted(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: "/Replication/SendCompleted",
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(ReplicationServer).SendCompleted(ctx, req.(*SendCompletedReq))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _Replication_HintMostRecentCommonAncestor_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(HintMostRecentCommonAncestorReq)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(ReplicationServer).HintMostRecentCommonAncestor(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: "/Replication/HintMostRecentCommonAncestor",
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(ReplicationServer).HintMostRecentCommonAncestor(ctx, req.(*HintMostRecentCommonAncestorReq))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 var _Replication_serviceDesc = grpc.ServiceDesc{
 	ServiceName: "Replication",
 	HandlerType: (*ReplicationServer)(nil),
@@ -1379,63 +1436,77 @@ var _Replication_serviceDesc = grpc.ServiceDesc{
 			MethodName: "ReplicationCursor",
 			Handler:    _Replication_ReplicationCursor_Handler,
 		},
+		{
+			MethodName: "SendCompleted",
+			Handler:    _Replication_SendCompleted_Handler,
+		},
+		{
+			MethodName: "HintMostRecentCommonAncestor",
+			Handler:    _Replication_HintMostRecentCommonAncestor_Handler,
+		},
 	},
 	Streams:  []grpc.StreamDesc{},
 	Metadata: "pdu.proto",
 }
 
-func init() { proto.RegisterFile("pdu.proto", fileDescriptor_pdu_83b7e2a28d820622) }
+func init() { proto.RegisterFile("pdu.proto", fileDescriptor_pdu_0f43b713cd3bf056) }
 
-var fileDescriptor_pdu_83b7e2a28d820622 = []byte{
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-	0x00,
+var fileDescriptor_pdu_0f43b713cd3bf056 = []byte{
+	// 892 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x8c, 0x56, 0xdf, 0x6f, 0xdb, 0x36,
+	0x10, 0x8e, 0x6c, 0x39, 0x91, 0xcf, 0xe9, 0xea, 0x5c, 0xb2, 0x42, 0x13, 0xba, 0xce, 0xe3, 0x86,
+	0xc1, 0x0d, 0x30, 0x61, 0xc8, 0x7e, 0x60, 0xc3, 0x80, 0x02, 0x8d, 0x93, 0x34, 0xc5, 0xd6, 0xce,
+	0x60, 0xbc, 0x62, 0xe8, 0x9b, 0x6a, 0x1f, 0x12, 0x21, 0xb2, 0xa8, 0x90, 0xf4, 0x50, 0x6f, 0x7b,
+	0xda, 0xe3, 0xfe, 0xbd, 0xe5, 0x0f, 0x2a, 0x44, 0x4b, 0xb6, 0x6c, 0xc9, 0x89, 0x9f, 0xcc, 0xfb,
+	0x78, 0x14, 0xef, 0xbe, 0xfb, 0xee, 0x68, 0x68, 0x26, 0xa3, 0x89, 0x9f, 0x48, 0xa1, 0x05, 0xdb,
+	0x87, 0xbd, 0x5f, 0x43, 0xa5, 0xcf, 0xc2, 0x88, 0xd4, 0x54, 0x69, 0x1a, 0x73, 0xba, 0x61, 0xc7,
+	0x65, 0x50, 0xe1, 0xd7, 0xd0, 0x5a, 0x00, 0xca, 0xb5, 0x3a, 0xf5, 0x6e, 0xeb, 0xa8, 0xe5, 0x17,
+	0x9c, 0x8a, 0xfb, 0xec, 0x3f, 0x0b, 0x60, 0x61, 0x23, 0x82, 0xdd, 0x0f, 0xf4, 0x95, 0x6b, 0x75,
+	0xac, 0x6e, 0x93, 0x9b, 0x35, 0x76, 0xa0, 0xc5, 0x49, 0x4d, 0xc6, 0x34, 0x10, 0xd7, 0x14, 0xbb,
+	0x35, 0xb3, 0x55, 0x84, 0xf0, 0x4b, 0x78, 0xf0, 0x52, 0xf5, 0xa3, 0x60, 0x48, 0x57, 0x22, 0x1a,
+	0x91, 0x74, 0xeb, 0x1d, 0xab, 0xeb, 0xf0, 0x65, 0x30, 0xfd, 0xce, 0x4b, 0x75, 0x1a, 0x0f, 0xe5,
+	0x34, 0xd1, 0x34, 0x72, 0x6d, 0xe3, 0x53, 0x84, 0xd8, 0xcf, 0xf0, 0xc9, 0x72, 0x42, 0x6f, 0x48,
+	0xaa, 0x50, 0xc4, 0x8a, 0xd3, 0x0d, 0x3e, 0x29, 0x06, 0x9a, 0x05, 0x58, 0x40, 0xd8, 0x2f, 0xeb,
+	0x0f, 0x2b, 0xf4, 0xc1, 0xc9, 0xcd, 0x8c, 0x12, 0xf4, 0x4b, 0x9e, 0x7c, 0xee, 0xc3, 0x6e, 0x2d,
+	0xd8, 0x2b, 0xed, 0xe3, 0x11, 0xd8, 0x83, 0x69, 0x42, 0xe6, 0xf2, 0x8f, 0x8e, 0x9e, 0x94, 0xbf,
+	0xe0, 0x67, 0xbf, 0xa9, 0x17, 0x37, 0xbe, 0x29, 0xa3, 0xaf, 0x83, 0x31, 0x65, 0xb4, 0x99, 0x75,
+	0x8a, 0xbd, 0x98, 0x84, 0x23, 0x43, 0x93, 0xcd, 0xcd, 0x1a, 0x1f, 0x43, 0xb3, 0x27, 0x29, 0xd0,
+	0x34, 0xf8, 0xe3, 0x85, 0xe1, 0xc6, 0xe6, 0x0b, 0x00, 0x3d, 0x70, 0x8c, 0x11, 0x8a, 0xd8, 0x6d,
+	0x98, 0x2f, 0xcd, 0x6d, 0xf6, 0x14, 0x5a, 0x85, 0x6b, 0x71, 0x17, 0x9c, 0x8b, 0x38, 0x48, 0xd4,
+	0x95, 0xd0, 0xed, 0xad, 0xd4, 0x3a, 0x16, 0xe2, 0x7a, 0x1c, 0xc8, 0xeb, 0xb6, 0xc5, 0xfe, 0xb7,
+	0x60, 0xe7, 0x82, 0xe2, 0xd1, 0x06, 0x7c, 0xe2, 0x57, 0x60, 0x9f, 0x49, 0x31, 0x36, 0x81, 0x57,
+	0xd3, 0x65, 0xf6, 0x91, 0x41, 0x6d, 0x20, 0x4c, 0x2a, 0xd5, 0x5e, 0xb5, 0x81, 0x58, 0x95, 0x90,
+	0x5d, 0x96, 0x10, 0x83, 0xe6, 0x42, 0x1a, 0x0d, 0xc3, 0xaf, 0xed, 0x0f, 0x64, 0xc8, 0x17, 0x30,
+	0x3e, 0x82, 0xed, 0x13, 0x39, 0xe5, 0x93, 0xd8, 0xdd, 0x36, 0xda, 0xc9, 0x2c, 0xf6, 0x1d, 0x38,
+	0x7d, 0x29, 0x12, 0x92, 0x7a, 0x3a, 0xa7, 0xdb, 0x2a, 0xd0, 0x7d, 0x00, 0x8d, 0x37, 0x41, 0x34,
+	0xc9, 0x6b, 0x30, 0x33, 0xd8, 0xbf, 0x73, 0x2e, 0x14, 0x76, 0xe1, 0xe1, 0xef, 0x8a, 0x46, 0xab,
+	0x32, 0x77, 0xf8, 0x2a, 0x8c, 0x0c, 0x76, 0x4f, 0xdf, 0x27, 0x34, 0xd4, 0x34, 0xba, 0x08, 0xff,
+	0x22, 0x93, 0x77, 0x9d, 0x2f, 0x61, 0xf8, 0x14, 0x20, 0x8b, 0x27, 0x24, 0xe5, 0xda, 0x46, 0x6e,
+	0x4d, 0x3f, 0x0f, 0x91, 0x17, 0x36, 0xd9, 0x33, 0x68, 0xa7, 0x31, 0xf4, 0xc4, 0x38, 0x89, 0x48,
+	0x93, 0x29, 0xcc, 0x21, 0xb4, 0x7e, 0x93, 0xe1, 0x65, 0x18, 0x07, 0x11, 0xa7, 0x9b, 0x8c, 0x7f,
+	0xc7, 0xcf, 0xea, 0xc6, 0x8b, 0x9b, 0x0c, 0x4b, 0xe7, 0x15, 0xfb, 0x07, 0x80, 0xd3, 0x90, 0xc2,
+	0x3f, 0x69, 0x93, 0x32, 0xcf, 0xca, 0x57, 0xbb, 0xb3, 0x7c, 0x87, 0xd0, 0xee, 0x45, 0x14, 0xc8,
+	0x22, 0x3f, 0xb3, 0x16, 0x2f, 0xe1, 0x6c, 0xb7, 0x70, 0xbb, 0x62, 0x97, 0xb0, 0x7f, 0x42, 0x4a,
+	0x4b, 0x31, 0xcd, 0x35, 0xb9, 0x49, 0x2f, 0xe3, 0x37, 0xd0, 0x9c, 0xfb, 0xbb, 0xb5, 0xb5, 0xfd,
+	0xba, 0x70, 0x62, 0x6f, 0x01, 0x57, 0x2e, 0xca, 0xda, 0x3e, 0x37, 0xcd, 0x2d, 0x6b, 0xda, 0x3e,
+	0xf7, 0x49, 0x95, 0x72, 0x2a, 0xa5, 0x90, 0xb9, 0x52, 0x8c, 0xc1, 0x4e, 0xaa, 0x92, 0x48, 0x27,
+	0xed, 0x4e, 0x9a, 0x78, 0xa4, 0xf3, 0x91, 0xb2, 0xef, 0x97, 0x43, 0xe0, 0xb9, 0x0f, 0xfb, 0x01,
+	0x0e, 0x38, 0x25, 0x51, 0x38, 0x34, 0x5d, 0xdb, 0x9b, 0x48, 0x25, 0xe4, 0x26, 0x73, 0x6d, 0x50,
+	0x79, 0x4e, 0xe1, 0x41, 0x36, 0x44, 0xd2, 0x13, 0xf6, 0xf9, 0xd6, 0x7c, 0x8c, 0x38, 0xaf, 0x85,
+	0xa6, 0xf7, 0xa1, 0xd2, 0x33, 0x09, 0x9f, 0x6f, 0xf1, 0x39, 0x72, 0xec, 0xc0, 0xf6, 0x2c, 0x1c,
+	0xf6, 0x05, 0xec, 0xf4, 0xc3, 0xf8, 0x32, 0x0d, 0xc0, 0x85, 0x9d, 0x57, 0xa4, 0x54, 0x70, 0x99,
+	0x77, 0x4d, 0x6e, 0xb2, 0x4f, 0x73, 0x27, 0x95, 0xf6, 0xd5, 0xe9, 0xf0, 0x4a, 0xe4, 0x7d, 0x95,
+	0xae, 0xd9, 0xdf, 0xf0, 0xd9, 0x79, 0x18, 0xeb, 0x57, 0x42, 0xe9, 0xb4, 0xe4, 0xb1, 0xee, 0x89,
+	0xf1, 0x58, 0xc4, 0xcf, 0xe3, 0x21, 0x29, 0xbd, 0x51, 0x72, 0xf8, 0x23, 0x3c, 0x48, 0xf5, 0x4b,
+	0x32, 0xab, 0xc5, 0x1d, 0x42, 0x5c, 0x76, 0x64, 0x9f, 0xdf, 0x77, 0xb9, 0x3a, 0xec, 0x42, 0x7d,
+	0x20, 0xc3, 0x74, 0x04, 0x9e, 0x88, 0x58, 0xf7, 0x02, 0x49, 0xed, 0x2d, 0x6c, 0x42, 0xe3, 0x2c,
+	0x88, 0x14, 0xb5, 0x2d, 0x74, 0xc0, 0x1e, 0xc8, 0x09, 0xb5, 0x6b, 0x47, 0xb7, 0xf5, 0x74, 0x40,
+	0xcd, 0x49, 0x46, 0x0f, 0xec, 0x34, 0x71, 0x74, 0xfc, 0x8c, 0x24, 0x2f, 0x5f, 0x29, 0xfc, 0x09,
+	0x1e, 0x2e, 0xbf, 0x33, 0x0a, 0xd1, 0x2f, 0x3d, 0xce, 0x5e, 0x19, 0x53, 0xd8, 0x87, 0x47, 0xd5,
+	0x4f, 0x14, 0x7a, 0xfe, 0xda, 0x87, 0xcf, 0x5b, 0xbf, 0xa7, 0xf0, 0x19, 0xb4, 0x57, 0xa5, 0x89,
+	0x07, 0x7e, 0x45, 0xcb, 0x79, 0x55, 0xa8, 0xc2, 0xe7, 0xb0, 0x57, 0x12, 0x17, 0x7e, 0xec, 0x57,
+	0x09, 0xd5, 0xab, 0x84, 0x15, 0x7e, 0x3f, 0x2b, 0xe1, 0x7c, 0x04, 0xe1, 0x9e, 0xbf, 0x3a, 0xd2,
+	0xbc, 0x12, 0xa4, 0xf0, 0x1d, 0x3c, 0xbe, 0xab, 0x7e, 0xd8, 0xf1, 0xef, 0xd1, 0x96, 0x77, 0x9f,
+	0x87, 0x3a, 0x6e, 0xbc, 0xad, 0x27, 0xa3, 0xc9, 0xbb, 0x6d, 0xf3, 0x1f, 0xea, 0xdb, 0x0f, 0x01,
+	0x00, 0x00, 0xff, 0xff, 0xad, 0x4e, 0x98, 0x29, 0x50, 0x09, 0x00, 0x00,
 }

replication/logic/pdu/pdu.proto

@@ -2,131 +2,133 @@ syntax = "proto3";
 option go_package = "pdu";
 
 service Replication {
-    rpc Ping (PingReq) returns (PingRes);
-    rpc ListFilesystems (ListFilesystemReq) returns (ListFilesystemRes);
-    rpc ListFilesystemVersions (ListFilesystemVersionsReq) returns (ListFilesystemVersionsRes);
-    rpc DestroySnapshots (DestroySnapshotsReq) returns (DestroySnapshotsRes);
-    rpc ReplicationCursor (ReplicationCursorReq) returns (ReplicationCursorRes);
-    // for Send and Recv, see package rpc
+  rpc Ping(PingReq) returns (PingRes);
+  rpc ListFilesystems(ListFilesystemReq) returns (ListFilesystemRes);
+  rpc ListFilesystemVersions(ListFilesystemVersionsReq)
+      returns (ListFilesystemVersionsRes);
+  rpc DestroySnapshots(DestroySnapshotsReq) returns (DestroySnapshotsRes);
+  rpc ReplicationCursor(ReplicationCursorReq) returns (ReplicationCursorRes);
+  rpc SendCompleted(SendCompletedReq) returns (SendCompletedRes);
+  rpc HintMostRecentCommonAncestor(HintMostRecentCommonAncestorReq) returns (HintMostRecentCommonAncestorRes);
+  // for Send and Recv, see package rpc
 }
 
 message ListFilesystemReq {}
 
-message ListFilesystemRes {
-    repeated Filesystem Filesystems = 1;
-}
+message ListFilesystemRes { repeated Filesystem Filesystems = 1; }
 
 message Filesystem {
-    string Path = 1;
-    string ResumeToken = 2;
-    bool IsPlaceholder = 3;
+  string Path = 1;
+  string ResumeToken = 2;
+  bool IsPlaceholder = 3;
+  bool IsEncrypted = 4;
 }
 
-message ListFilesystemVersionsReq {
-    string Filesystem = 1;
-}
+message ListFilesystemVersionsReq { string Filesystem = 1; }
 
-message ListFilesystemVersionsRes {
-    repeated FilesystemVersion Versions = 1;
-}
+message ListFilesystemVersionsRes { repeated FilesystemVersion Versions = 1; }
 
 message FilesystemVersion {
-    enum VersionType {
-        Snapshot = 0;
-        Bookmark = 1;
-    }
-    VersionType Type = 1;
-    string Name = 2;
-    uint64 Guid = 3;
-    uint64 CreateTXG = 4;
-    string Creation = 5; // RFC 3339
+  enum VersionType {
+    Snapshot = 0;
+    Bookmark = 1;
+  }
+  VersionType Type = 1;
+  string Name = 2;
+  uint64 Guid = 3;
+  uint64 CreateTXG = 4;
+  string Creation = 5; // RFC 3339
 }
 
+enum Tri {
+  DontCare = 0;
+  False = 1;
+  True = 2;
+}
 
 message SendReq {
-    string Filesystem  = 1;
-    string From = 2;
-    // May be empty / null to request a full transfer of From
-    string To = 3;
+  string Filesystem = 1;
+  // May be empty / null to request a full transfer of To
+  FilesystemVersion From = 2;
+  FilesystemVersion To = 3;
 
-    // If ResumeToken is not empty, the resume token that CAN be tried for 'zfs send' by the sender.
-    // The sender MUST indicate in SendRes.UsedResumeToken
-    // If it does not work, the sender SHOULD clear the resume token on their side
-    // and use From and To instead
-    // If ResumeToken is not empty, the GUIDs of From and To
-    // MUST correspond to those encoded in the ResumeToken.
-    // Otherwise, the Sender MUST return an error.
-    string ResumeToken  = 4;
-    bool Compress = 5;
-    bool Dedup = 6;
+  // If ResumeToken is not empty, the resume token that CAN be used for 'zfs
+  // send' by the sender. The sender MUST indicate use of ResumeToken in the
+  // reply message SendRes.UsedResumeToken If it does not work, the sender
+  // SHOULD clear the resume token on their side and use From and To instead If
+  // ResumeToken is not empty, the GUIDs of From and To MUST correspond to those
+  // encoded in the ResumeToken. Otherwise, the Sender MUST return an error.
+  string ResumeToken = 4;
+  Tri Encrypted = 5;
 
-    bool DryRun = 7;
+  bool DryRun = 6;
 }
 
 message Property {
-    string Name = 1;
-    string Value = 2;
+  string Name = 1;
+  string Value = 2;
 }
 
 message SendRes {
-    // Whether the resume token provided in the request has been used or not.
-    bool UsedResumeToken = 2;
+  // Whether the resume token provided in the request has been used or not.
+  // If the SendReq.ResumeToken == "", this field has no meaning.
+  bool UsedResumeToken = 2;
 
-    // Expected stream size determined by dry run, not exact.
-    // 0 indicates that for the given SendReq, no size estimate could be made.
-    int64 ExpectedSize = 3;
+  // Expected stream size determined by dry run, not exact.
+  // 0 indicates that for the given SendReq, no size estimate could be made.
+  int64 ExpectedSize = 3;
 
-    repeated Property Properties = 4;
+  repeated Property Properties = 4;
 }
 
-message ReceiveReq {
-    string Filesystem = 1; // FIXME should be snapshot name, we can enforce that on recv
+message SendCompletedReq {
+  SendReq OriginalReq = 2;
+}
 
-    // If true, the receiver should clear the resume token before perfoming the zfs recv of the stream in the request
-    bool ClearResumeToken = 2;
+message SendCompletedRes {}
+
+message ReceiveReq {
+  string Filesystem = 1;
+  FilesystemVersion To = 2;
+
+  // If true, the receiver should clear the resume token before perfoming the
+  // zfs recv of the stream in the request
+  bool ClearResumeToken = 3;
 }
 
 message ReceiveRes {}
 
 message DestroySnapshotsReq {
-    string Filesystem = 1;
-    // Path to filesystem, snapshot or bookmark to be destroyed
-    repeated FilesystemVersion Snapshots = 2;
+  string Filesystem = 1;
+  // Path to filesystem, snapshot or bookmark to be destroyed
+  repeated FilesystemVersion Snapshots = 2;
 }
 
 message DestroySnapshotRes {
-    FilesystemVersion Snapshot = 1;
-    string Error = 2;
+  FilesystemVersion Snapshot = 1;
+  string Error = 2;
 }
 
-message DestroySnapshotsRes {
-    repeated DestroySnapshotRes Results = 1;
-}
+message DestroySnapshotsRes { repeated DestroySnapshotRes Results = 1; }
 
-message ReplicationCursorReq {
-    string Filesystem = 1;
-    message GetOp {}
-    message SetOp {
-        string Snapshot = 2;
-    }
-    oneof op {
-        GetOp get = 2;
-        SetOp set = 3;
-    }
-}
+message ReplicationCursorReq { string Filesystem = 1; }
 
 message ReplicationCursorRes {
-    oneof Result {
-        uint64 Guid = 1;
-        bool Notexist = 2;
-    }
+  oneof Result {
+    uint64 Guid = 1;
+    bool Notexist = 2;
+  }
 }
 
-message PingReq {
-    string Message = 1;
-}
+message PingReq { string Message = 1; }
 
 message PingRes {
-    // Echo must be PingReq.Message
-    string Echo = 1;
-}
+  // Echo must be PingReq.Message
+  string Echo = 1;
+}
+
+message HintMostRecentCommonAncestorReq {
+    string Filesystem = 1;
+    FilesystemVersion SenderVersion = 2;
+}
+message HintMostRecentCommonAncestorRes {}

replication/logic/pdu/pdu_extras.go

@@ -7,6 +7,14 @@ import (
 	"github.com/zrepl/zrepl/zfs"
 )
 
+func (v *FilesystemVersion) GetRelName() string {
+	zv, err := v.ZFSFilesystemVersion()
+	if err != nil {
+		return ""
+	}
+	return zv.String()
+}
+
 func (v *FilesystemVersion) RelName() string {
 	zv, err := v.ZFSFilesystemVersion()
 	if err != nil {

replication/logic/replication_logic.go

@@ -30,6 +30,7 @@ type Endpoint interface {
 	ListFilesystemVersions(ctx context.Context, req *pdu.ListFilesystemVersionsReq) (*pdu.ListFilesystemVersionsRes, error)
 	DestroySnapshots(ctx context.Context, req *pdu.DestroySnapshotsReq) (*pdu.DestroySnapshotsRes, error)
 	WaitForConnectivity(ctx context.Context) error
+	HintMostRecentCommonAncestor(context.Context, *pdu.HintMostRecentCommonAncestorReq) (*pdu.HintMostRecentCommonAncestorRes, error)
 }
 
 type Sender interface {
@@ -38,6 +39,7 @@ type Sender interface {
 	// any next call to the parent github.com/zrepl/zrepl/replication.Endpoint.
 	// If the send request is for dry run the io.ReadCloser will be nil
 	Send(ctx context.Context, r *pdu.SendReq) (*pdu.SendRes, zfs.StreamCopier, error)
+	SendCompleted(ctx context.Context, r *pdu.SendCompletedReq) (*pdu.SendCompletedRes, error)
 	ReplicationCursor(ctx context.Context, req *pdu.ReplicationCursorReq) (*pdu.ReplicationCursorRes, error)
 }
 
@@ -48,9 +50,14 @@ type Receiver interface {
 	Receive(ctx context.Context, req *pdu.ReceiveReq, receive zfs.StreamCopier) (*pdu.ReceiveRes, error)
 }
 
+type PlannerPolicy struct {
+	EncryptedSend tri // all sends must be encrypted (send -w, and encryption!=off)
+}
+
 type Planner struct {
 	sender   Sender
 	receiver Receiver
+	policy   PlannerPolicy
 
 	promSecsPerState    *prometheus.HistogramVec // labels: state
 	promBytesReplicated *prometheus.CounterVec   // labels: filesystem
@@ -109,10 +116,11 @@ func (p *Planner) WaitForConnectivity(ctx context.Context) error {
 type Filesystem struct {
 	sender   Sender
 	receiver Receiver
+	policy   PlannerPolicy
 
-	Path                string // compat
-	receiverFS          *pdu.Filesystem
-	promBytesReplicated prometheus.Counter // compat
+	Path                 string             // compat
+	receiverFS, senderFS *pdu.Filesystem    // receiverFS may be nil, senderFS never nil
+	promBytesReplicated  prometheus.Counter // compat
 
 	sizeEstimateRequestSem *semaphore.S
 }
@@ -145,8 +153,10 @@ type Step struct {
 	sender   Sender
 	receiver Receiver
 
-	parent   *Filesystem
-	from, to *pdu.FilesystemVersion // compat
+	parent      *Filesystem
+	from, to    *pdu.FilesystemVersion // from may be nil, indicating full send
+	encrypt     tri
+	resumeToken string // empty means no resume token shall be used
 
 	expectedSize int64 // 0 means no size estimate present / possible
 
@@ -186,23 +196,36 @@ func (s *Step) ReportInfo() *report.StepInfo {
 	}
 	s.byteCounterMtx.Unlock()
 
-	// FIXME stick to zfs convention of from and to
 	from := ""
 	if s.from != nil {
 		from = s.from.RelName()
 	}
+	var encrypted report.EncryptedEnum
+	switch s.encrypt {
+	case DontCare:
+		encrypted = report.EncryptedSenderDependent
+	case True:
+		encrypted = report.EncryptedTrue
+	case False:
+		encrypted = report.EncryptedFalse
+	default:
+		panic(fmt.Sprintf("unknown variant %s", s.encrypt))
+	}
 	return &report.StepInfo{
 		From:            from,
 		To:              s.to.RelName(),
+		Resumed:         s.resumeToken != "",
+		Encrypted:       encrypted,
 		BytesExpected:   s.expectedSize,
 		BytesReplicated: byteCounter,
 	}
 }
 
-func NewPlanner(secsPerState *prometheus.HistogramVec, bytesReplicated *prometheus.CounterVec, sender Sender, receiver Receiver) *Planner {
+func NewPlanner(secsPerState *prometheus.HistogramVec, bytesReplicated *prometheus.CounterVec, sender Sender, receiver Receiver, policy PlannerPolicy) *Planner {
 	return &Planner{
 		sender:              sender,
 		receiver:            receiver,
+		policy:              policy,
 		promSecsPerState:    secsPerState,
 		promBytesReplicated: bytesReplicated,
 	}
@@ -265,7 +288,9 @@ func (p *Planner) doPlanning(ctx context.Context) ([]*Filesystem, error) {
 		q = append(q, &Filesystem{
 			sender:                 p.sender,
 			receiver:               p.receiver,
+			policy:                 p.policy,
 			Path:                   fs.Path,
+			senderFS:               fs,
 			receiverFS:             receiverFS,
 			promBytesReplicated:    ctr,
 			sizeEstimateRequestSem: sizeEstimateRequestSem,
@@ -281,6 +306,10 @@ func (fs *Filesystem) doPlanning(ctx context.Context) ([]*Step, error) {
 
 	log.Debug("assessing filesystem")
 
+	if fs.policy.EncryptedSend == True && !fs.senderFS.GetIsEncrypted() {
+		return nil, fmt.Errorf("sender filesystem is not encrypted but policy mandates encrypted send")
+	}
+
 	sfsvsres, err := fs.sender.ListFilesystemVersions(ctx, &pdu.ListFilesystemVersionsReq{Filesystem: fs.Path})
 	if err != nil {
 		log.WithError(err).Error("cannot get remote filesystem versions")
@@ -306,42 +335,194 @@ func (fs *Filesystem) doPlanning(ctx context.Context) ([]*Step, error) {
 		rfsvs = []*pdu.FilesystemVersion{}
 	}
 
-	path, conflict := IncrementalPath(rfsvs, sfsvs)
-	if conflict != nil {
-		var msg string
-		path, msg = resolveConflict(conflict) // no shadowing allowed!
-		if path != nil {
-			log.WithField("conflict", conflict).Info("conflict")
-			log.WithField("resolution", msg).Info("automatically resolved")
-		} else {
-			log.WithField("conflict", conflict).Error("conflict")
-			log.WithField("problem", msg).Error("cannot resolve conflict")
+	var resumeToken *zfs.ResumeToken
+	var resumeTokenRaw string
+	if fs.receiverFS != nil && fs.receiverFS.ResumeToken != "" {
+		resumeTokenRaw = fs.receiverFS.ResumeToken // shadow
+		log.WithField("receiverFS.ResumeToken", resumeTokenRaw).Debug("decode receiver fs resume token")
+		resumeToken, err = zfs.ParseResumeToken(ctx, resumeTokenRaw) // shadow
+		if err != nil {
+			// TODO in theory, we could do replication without resume token, but that would mean that
+			// we need to discard the resumable state on the receiver's side.
+			// Would be easy by setting UsedResumeToken=false in the RecvReq ...
+			// FIXME / CHECK semantics UsedResumeToken if SendReq.ResumeToken == ""
+			log.WithError(err).Error("cannot decode resume token, aborting")
+			return nil, err
 		}
-	}
-	if len(path) == 0 {
-		return nil, conflict
+		log.WithField("token", resumeToken).Debug("decode resume token")
 	}
 
-	steps := make([]*Step, 0, len(path))
-	// FIXME unify struct declarations => initializer?
-	if len(path) == 1 {
-		steps = append(steps, &Step{
+	// give both sides a hint about how far the replication got
+	// This serves as a cummulative variant of SendCompleted and can be useful
+	// for example to release stale holds from an earlier (interrupted) replication.
+	// TODO FIXME: enqueue this as a replication step instead of doing it here during planning
+	//             then again, the step should run regardless of planning success
+	//             so maybe a separate phase before PLANNING, then?
+	path, conflict := IncrementalPath(rfsvs, sfsvs)
+	var sender_mrca *pdu.FilesystemVersion // from sfsvs
+	if conflict == nil && len(path) > 0 {
+		sender_mrca = path[0] // shadow
+	}
+	if sender_mrca != nil {
+		var wg sync.WaitGroup
+		doHint := func(ep Endpoint, name string) {
+			defer wg.Done()
+			log := log.WithField("to_side", name).
+				WithField("sender_mrca", sender_mrca.String())
+			log.Debug("hint most recent common ancestor")
+			hint := &pdu.HintMostRecentCommonAncestorReq{
+				Filesystem:    fs.Path,
+				SenderVersion: sender_mrca,
+			}
+			_, err := ep.HintMostRecentCommonAncestor(ctx, hint)
+			if err != nil {
+				log.WithError(err).Error("error hinting most recent common ancestor")
+			}
+		}
+		wg.Add(2)
+		go doHint(fs.sender, "sender")
+		go doHint(fs.receiver, "receiver")
+		wg.Wait()
+	} else {
+		log.Debug("cannot identify most recent common ancestor, skipping hint")
+	}
+
+	var steps []*Step
+	// build the list of replication steps
+	//
+	// prefer to resume any started replication instead of starting over with a normal IncrementalPath
+	//
+	// look for the step encoded in the resume token in the sender's version
+	// if we find that step:
+	//   1. use it as first step (including resume token)
+	//   2. compute subsequent steps by computing incremental path from the token.To version on
+	//      ...
+	//      that's actually equivalent to simply cutting off earlier versions from rfsvs and sfsvs
+	if resumeToken != nil {
+
+		sfsvs := SortVersionListByCreateTXGThenBookmarkLTSnapshot(sfsvs)
+
+		var fromVersion, toVersion *pdu.FilesystemVersion
+		var toVersionIdx int
+		for idx, sfsv := range sfsvs {
+			if resumeToken.HasFromGUID && sfsv.Guid == resumeToken.FromGUID {
+				if fromVersion != nil && fromVersion.Type == pdu.FilesystemVersion_Snapshot {
+					// prefer snapshots over bookmarks for size estimation
+				} else {
+					fromVersion = sfsv
+				}
+			}
+			if resumeToken.HasToGUID && sfsv.Guid == resumeToken.ToGUID && sfsv.Type == pdu.FilesystemVersion_Snapshot {
+				// `toversion` must always be a snapshot
+				toVersion, toVersionIdx = sfsv, idx
+			}
+		}
+
+		encryptionMatches := false
+		switch fs.policy.EncryptedSend {
+		case True:
+			encryptionMatches = resumeToken.RawOK && resumeToken.CompressOK
+		case False:
+			encryptionMatches = !resumeToken.RawOK && !resumeToken.CompressOK
+		case DontCare:
+			encryptionMatches = true
+		}
+
+		log.WithField("fromVersion", fromVersion).
+			WithField("toVersion", toVersion).
+			WithField("encryptionMatches", encryptionMatches).
+			Debug("result of resume-token-matching to sender's versions")
+
+		if !encryptionMatches {
+			return nil, fmt.Errorf("resume token `rawok`=%v and `compressok`=%v are incompatible with encryption policy=%v", resumeToken.RawOK, resumeToken.CompressOK, fs.policy.EncryptedSend)
+		} else if toVersion == nil {
+			return nil, fmt.Errorf("resume token `toguid` = %v not found on sender (`toname` = %q)", resumeToken.ToGUID, resumeToken.ToName)
+		} else if fromVersion == toVersion {
+			return nil, fmt.Errorf("resume token `fromguid` and `toguid` match same version on sener")
+		}
+		// fromVersion may be nil, toVersion is no nil, encryption matches
+		// good to go this one step!
+		resumeStep := &Step{
 			parent:   fs,
 			sender:   fs.sender,
 			receiver: fs.receiver,
-			from:     nil,
-			to:       path[0],
-		})
-	} else {
-		for i := 0; i < len(path)-1; i++ {
+
+			from:    fromVersion,
+			to:      toVersion,
+			encrypt: fs.policy.EncryptedSend,
+
+			resumeToken: resumeTokenRaw,
+		}
+
+		// by definition, the resume token _must_ be the receiver's most recent version, if they have any
+		// don't bother checking, zfs recv will produce an error if above assumption is wrong
+		//
+		// thus, subsequent steps are just incrementals on the sender's remaining _snapshots_ (not bookmarks)
+
+		var remainingSFSVs []*pdu.FilesystemVersion
+		for _, sfsv := range sfsvs[toVersionIdx:] {
+			if sfsv.Type == pdu.FilesystemVersion_Snapshot {
+				remainingSFSVs = append(remainingSFSVs, sfsv)
+			}
+		}
+
+		steps = make([]*Step, 0, len(remainingSFSVs)) // shadow
+		steps = append(steps, resumeStep)
+		for i := 0; i < len(remainingSFSVs)-1; i++ {
 			steps = append(steps, &Step{
 				parent:   fs,
 				sender:   fs.sender,
 				receiver: fs.receiver,
-				from:     path[i],
-				to:       path[i+1],
+				from:     remainingSFSVs[i],
+				to:       remainingSFSVs[i+1],
+				encrypt:  fs.policy.EncryptedSend,
 			})
 		}
+	} else { // resumeToken == nil
+		path, conflict := IncrementalPath(rfsvs, sfsvs)
+		if conflict != nil {
+			var msg string
+			path, msg = resolveConflict(conflict) // no shadowing allowed!
+			if path != nil {
+				log.WithField("conflict", conflict).Info("conflict")
+				log.WithField("resolution", msg).Info("automatically resolved")
+			} else {
+				log.WithField("conflict", conflict).Error("conflict")
+				log.WithField("problem", msg).Error("cannot resolve conflict")
+			}
+		}
+		if len(path) == 0 {
+			return nil, conflict
+		}
+
+		steps = make([]*Step, 0, len(path)) // shadow
+		if len(path) == 1 {
+			steps = append(steps, &Step{
+				parent:   fs,
+				sender:   fs.sender,
+				receiver: fs.receiver,
+
+				from:    nil,
+				to:      path[0],
+				encrypt: fs.policy.EncryptedSend,
+			})
+		} else {
+			for i := 0; i < len(path)-1; i++ {
+				steps = append(steps, &Step{
+					parent:   fs,
+					sender:   fs.sender,
+					receiver: fs.receiver,
+
+					from:    path[i],
+					to:      path[i+1],
+					encrypt: fs.policy.EncryptedSend,
+				})
+			}
+		}
+	}
+
+	if len(steps) == 0 {
+		log.Info("planning determined that no replication steps are required")
 	}
 
 	log.Debug("compute send size estimate")
@@ -389,29 +570,6 @@ func (fs *Filesystem) doPlanning(ctx context.Context) ([]*Step, error) {
 	return steps, nil
 }
 
-// type FilesystemsReplicationFailedError struct {
-// 	FilesystemsWithError []*fsrep.Replication
-// }
-
-// func (e FilesystemsReplicationFailedError) Error() string {
-// 	allSame := true
-// 	lastErr := e.FilesystemsWithError[0].Err().Error()
-// 	for _, fs := range e.FilesystemsWithError {
-// 		fsErr := fs.Err().Error()
-// 		allSame = allSame && lastErr == fsErr
-// 	}
-
-// 	fsstr := "multiple filesystems"
-// 	if len(e.FilesystemsWithError) == 1 {
-// 		fsstr = fmt.Sprintf("filesystem %s", e.FilesystemsWithError[0].FS())
-// 	}
-// 	errorStr := lastErr
-// 	if !allSame {
-// 		errorStr = "multiple different errors"
-// 	}
-// 	return fmt.Sprintf("%s could not be replicated: %s", fsstr, errorStr)
-// }
-
 func (s *Step) updateSizeEstimate(ctx context.Context) error {
 
 	log := getLogger(ctx)
@@ -430,19 +588,13 @@ func (s *Step) updateSizeEstimate(ctx context.Context) error {
 
 func (s *Step) buildSendRequest(dryRun bool) (sr *pdu.SendReq) {
 	fs := s.parent.Path
-	if s.from == nil {
-		sr = &pdu.SendReq{
-			Filesystem: fs,
-			To:         s.to.RelName(),
-			DryRun:     dryRun,
-		}
-	} else {
-		sr = &pdu.SendReq{
-			Filesystem: fs,
-			From:       s.from.RelName(),
-			To:         s.to.RelName(),
-			DryRun:     dryRun,
-		}
+	sr = &pdu.SendReq{
+		Filesystem:  fs,
+		From:        s.from, // may be nil
+		To:          s.to,
+		Encrypted:   s.encrypt.ToPDU(),
+		ResumeToken: s.resumeToken,
+		DryRun:      dryRun,
 	}
 	return sr
 }
@@ -478,6 +630,7 @@ func (s *Step) doReplication(ctx context.Context) error {
 
 	rr := &pdu.ReceiveReq{
 		Filesystem:       fs,
+		To:               sr.GetTo(),
 		ClearResumeToken: !sres.UsedResumeToken,
 	}
 	log.Debug("initiate receive request")
@@ -486,6 +639,7 @@ func (s *Step) doReplication(ctx context.Context) error {
 		log.
 			WithError(err).
 			WithField("errType", fmt.Sprintf("%T", err)).
+			WithField("rr", fmt.Sprintf("%v", rr)).
 			Error("receive request failed (might also be error on sender)")
 		// This failure could be due to
 		// 	- an unexpected exit of ZFS on the sending side
@@ -495,22 +649,12 @@ func (s *Step) doReplication(ctx context.Context) error {
 	}
 	log.Debug("receive finished")
 
-	log.Debug("advance replication cursor")
-	req := &pdu.ReplicationCursorReq{
-		Filesystem: fs,
-		Op: &pdu.ReplicationCursorReq_Set{
-			Set: &pdu.ReplicationCursorReq_SetOp{
-				Snapshot: s.to.GetName(),
-			},
-		},
-	}
-	_, err = s.sender.ReplicationCursor(ctx, req)
+	log.Debug("tell sender replication completed")
+	_, err = s.sender.SendCompleted(ctx, &pdu.SendCompletedReq{
+		OriginalReq: sr,
+	})
 	if err != nil {
-		log.WithError(err).Error("error advancing replication cursor")
-		// If this fails and replication planning restarts, the diff algorithm will find
-		// that cursor out of place. This is not a problem because then, it would just use another FS
-		// However, we FIXME have no means to just update the cursor in a
-		// second replication attempt right after this one where we don't have new snaps yet
+		log.WithError(err).Error("error telling sender that replication completed successfully")
 		return err
 	}
 

replication/logic/replication_logic_tri.go

@@ -0,0 +1,46 @@
+package logic
+
+import (
+	"fmt"
+
+	"github.com/zrepl/zrepl/replication/logic/pdu"
+)
+
+type tri int
+
+const (
+	DontCare = 0x0
+	False    = 0x1
+	True     = 0x2
+)
+
+func (t tri) String() string {
+	switch t {
+	case DontCare:
+		return "dontcare"
+	case False:
+		return "false"
+	case True:
+		return "true"
+	}
+	panic(fmt.Sprintf("unknown variant %v", int(t)))
+}
+
+func (t tri) ToPDU() pdu.Tri {
+	switch t {
+	case DontCare:
+		return pdu.Tri_DontCare
+	case False:
+		return pdu.Tri_False
+	case True:
+		return pdu.Tri_True
+	}
+	panic(fmt.Sprintf("unknown variant %v", int(t)))
+}
+
+func TriFromBool(b bool) tri {
+	if b {
+		return True
+	}
+	return False
+}

replication/replication.go

@@ -8,6 +8,6 @@ import (
 	"github.com/zrepl/zrepl/replication/driver"
 )
 
-func Do(ctx context.Context, planner driver.Planner) (driver.ReportFunc, driver.WaitFunc) {
-	return driver.Do(ctx, planner)
+func Do(ctx context.Context, initialConcurrency int, planner driver.Planner) (driver.ReportFunc, driver.WaitFunc, driver.SetConcurrencyFunc) {
+	return driver.Do(ctx, initialConcurrency, planner)
 }

replication/report/replication_report.go

@@ -10,6 +10,7 @@ type Report struct {
 	WaitReconnectSince, WaitReconnectUntil time.Time
 	WaitReconnectError                     *TimedError
 	Attempts                               []*AttemptReport
+	Concurrency                            int
 }
 
 var _, _ = json.Marshal(&Report{})
@@ -85,25 +86,37 @@ type StepReport struct {
 	Info *StepInfo
 }
 
+type EncryptedEnum string
+
+const (
+	EncryptedTrue            EncryptedEnum = "yes"
+	EncryptedFalse           EncryptedEnum = "no"
+	EncryptedSenderDependent EncryptedEnum = "sender-dependent"
+)
+
 type StepInfo struct {
 	From, To        string
+	Resumed         bool
+	Encrypted       EncryptedEnum
 	BytesExpected   int64
 	BytesReplicated int64
 }
 
-func (a *AttemptReport) BytesSum() (expected, replicated int64) {
+func (a *AttemptReport) BytesSum() (expected, replicated int64, containsInvalidSizeEstimates bool) {
 	for _, fs := range a.Filesystems {
-		e, r := fs.BytesSum()
+		e, r, fsContainsInvalidEstimate := fs.BytesSum()
+		containsInvalidSizeEstimates = containsInvalidSizeEstimates || fsContainsInvalidEstimate
 		expected += e
 		replicated += r
 	}
-	return expected, replicated
+	return expected, replicated, containsInvalidSizeEstimates
 }
 
-func (f *FilesystemReport) BytesSum() (expected, replicated int64) {
+func (f *FilesystemReport) BytesSum() (expected, replicated int64, containsInvalidSizeEstimates bool) {
 	for _, step := range f.Steps {
 		expected += step.Info.BytesExpected
 		replicated += step.Info.BytesReplicated
+		containsInvalidSizeEstimates = containsInvalidSizeEstimates || step.Info.BytesExpected == 0
 	}
 	return
 }
@@ -148,5 +161,5 @@ func (f *FilesystemReport) NextStep() *StepReport {
 }
 
 func (f *StepReport) IsIncremental() bool {
-	return f.Info.From != "" // FIXME change to ZFS semantics (To != "")
+	return f.Info.From != ""
 }

rpc/grpcclientidentity/authlistener_grpc_adaptor.go

@@ -99,7 +99,9 @@ func (*transportCredentials) OverrideServerName(string) error {
 	panic("not implemented")
 }
 
-func NewInterceptors(logger Logger, clientIdentityKey interface{}) (unary grpc.UnaryServerInterceptor, stream grpc.StreamServerInterceptor) {
+type ContextInterceptor = func(ctx context.Context) context.Context
+
+func NewInterceptors(logger Logger, clientIdentityKey interface{}, ctxInterceptor ContextInterceptor) (unary grpc.UnaryServerInterceptor, stream grpc.StreamServerInterceptor) {
 	unary = func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
 		logger.WithField("fullMethod", info.FullMethod).Debug("request")
 		p, ok := peer.FromContext(ctx)
@@ -113,8 +115,13 @@ func NewInterceptors(logger Logger, clientIdentityKey interface{}) (unary grpc.U
 		}
 		logger.WithField("peer_client_identity", a.clientIdentity).Debug("peer client identity")
 		ctx = context.WithValue(ctx, clientIdentityKey, a.clientIdentity)
+		if ctxInterceptor != nil {
+			ctx = ctxInterceptor(ctx)
+		}
 		return handler(ctx, req)
 	}
-	stream = nil
+	stream = func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		panic("unimplemented")
+	}
 	return
 }

rpc/grpcclientidentity/example/main.go

@@ -87,10 +87,13 @@ func server() {
 
 	log := logger.NewStderrDebugLogger()
 
-	srv, serve, err := grpchelper.NewServer(authListenerFactory, clientIdentityKey, log)
+	authListener, err := authListenerFactory()
 	if err != nil {
-		onErr(err, "new server")
+		onErr(err, "cannot listen")
 	}
+
+	srv, serve := grpchelper.NewServer(authListener, clientIdentityKey, log, nil)
+
 	svc := &greeter{"hello "}
 	pdu.RegisterGreeterServer(srv, svc)
 

rpc/grpcclientidentity/grpchelper/authlistener_grpc_adaptor_wrapper.go

@@ -50,25 +50,25 @@ func ClientConn(cn transport.Connecter, log Logger) *grpc.ClientConn {
 }
 
 // NewServer is a convenience interface around the TransportCredentials and Interceptors interface.
-func NewServer(authListenerFactory transport.AuthenticatedListenerFactory, clientIdentityKey interface{}, logger grpcclientidentity.Logger) (srv *grpc.Server, serve func() error, err error) {
+func NewServer(authListener transport.AuthenticatedListener, clientIdentityKey interface{}, logger grpcclientidentity.Logger, ctxInterceptor grpcclientidentity.ContextInterceptor) (srv *grpc.Server, serve func() error) {
 	ka := grpc.KeepaliveParams(keepalive.ServerParameters{
 		Time:    StartKeepalivesAfterInactivityDuration,
 		Timeout: KeepalivePeerTimeout,
 	})
+	ep := grpc.KeepaliveEnforcementPolicy(keepalive.EnforcementPolicy{
+		MinTime:             StartKeepalivesAfterInactivityDuration / 2, // avoid skew
+		PermitWithoutStream: true,
+	})
 	tcs := grpcclientidentity.NewTransportCredentials(logger)
-	unary, stream := grpcclientidentity.NewInterceptors(logger, clientIdentityKey)
-	srv = grpc.NewServer(grpc.Creds(tcs), grpc.UnaryInterceptor(unary), grpc.StreamInterceptor(stream), ka)
+	unary, stream := grpcclientidentity.NewInterceptors(logger, clientIdentityKey, ctxInterceptor)
+	srv = grpc.NewServer(grpc.Creds(tcs), grpc.UnaryInterceptor(unary), grpc.StreamInterceptor(stream), ka, ep)
 
 	serve = func() error {
-		l, err := authListenerFactory()
-		if err != nil {
-			return err
-		}
-		if err := srv.Serve(netadaptor.New(l, logger)); err != nil {
+		if err := srv.Serve(netadaptor.New(authListener, logger)); err != nil {
 			return err
 		}
 		return nil
 	}
 
-	return srv, serve, nil
+	return srv, serve
 }

rpc/rpc_client.go

@@ -116,6 +116,14 @@ func (c *Client) ReplicationCursor(ctx context.Context, in *pdu.ReplicationCurso
 	return c.controlClient.ReplicationCursor(ctx, in)
 }
 
+func (c *Client) SendCompleted(ctx context.Context, in *pdu.SendCompletedReq) (*pdu.SendCompletedRes, error) {
+	return c.controlClient.SendCompleted(ctx, in)
+}
+
+func (c *Client) HintMostRecentCommonAncestor(ctx context.Context, in *pdu.HintMostRecentCommonAncestorReq) (*pdu.HintMostRecentCommonAncestorRes, error) {
+	return c.controlClient.HintMostRecentCommonAncestor(ctx, in)
+}
+
 func (c *Client) WaitForConnectivity(ctx context.Context) error {
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()

rpc/rpc_server.go

@@ -4,13 +4,10 @@ import (
 	"context"
 	"time"
 
-	"google.golang.org/grpc"
-
 	"github.com/zrepl/zrepl/endpoint"
 	"github.com/zrepl/zrepl/replication/logic/pdu"
 	"github.com/zrepl/zrepl/rpc/dataconn"
-	"github.com/zrepl/zrepl/rpc/grpcclientidentity"
-	"github.com/zrepl/zrepl/rpc/netadaptor"
+	"github.com/zrepl/zrepl/rpc/grpcclientidentity/grpchelper"
 	"github.com/zrepl/zrepl/rpc/versionhandshake"
 	"github.com/zrepl/zrepl/transport"
 	"github.com/zrepl/zrepl/util/envconst"
@@ -28,7 +25,6 @@ type serveFunc func(ctx context.Context, demuxedListener transport.Authenticated
 type Server struct {
 	logger             Logger
 	handler            Handler
-	controlServer      *grpc.Server
 	controlServerServe serveFunc
 	dataServer         *dataconn.Server
 	dataServerServe    serveFunc
@@ -40,11 +36,11 @@ type HandlerContextInterceptor func(ctx context.Context) context.Context
 func NewServer(handler Handler, loggers Loggers, ctxInterceptor HandlerContextInterceptor) *Server {
 
 	// setup control server
-	tcs := grpcclientidentity.NewTransportCredentials(loggers.Control) // TODO different subsystem for log
-	unary, stream := grpcclientidentity.NewInterceptors(loggers.Control, endpoint.ClientIdentityKey)
-	controlServer := grpc.NewServer(grpc.Creds(tcs), grpc.UnaryInterceptor(unary), grpc.StreamInterceptor(stream))
-	pdu.RegisterReplicationServer(controlServer, handler)
 	controlServerServe := func(ctx context.Context, controlListener transport.AuthenticatedListener, errOut chan<- error) {
+
+		controlServer, serve := grpchelper.NewServer(controlListener, endpoint.ClientIdentityKey, loggers.Control, ctxInterceptor)
+		pdu.RegisterReplicationServer(controlServer, handler)
+
 		// give time for graceful stop until deadline expires, then hard stop
 		go func() {
 			<-ctx.Done()
@@ -55,7 +51,7 @@ func NewServer(handler Handler, loggers Loggers, ctxInterceptor HandlerContextIn
 			controlServer.GracefulStop()
 		}()
 
-		errOut <- controlServer.Serve(netadaptor.New(controlListener, loggers.Control))
+		errOut <- serve()
 	}
 
 	// setup data server
@@ -76,7 +72,6 @@ func NewServer(handler Handler, loggers Loggers, ctxInterceptor HandlerContextIn
 	server := &Server{
 		logger:             loggers.General,
 		handler:            handler,
-		controlServer:      controlServer,
 		controlServerServe: controlServerServe,
 		dataServer:         dataServer,
 		dataServerServe:    dataServerServe,

rpc/versionhandshake/versionhandshake.go

@@ -152,7 +152,7 @@ func (m *HandshakeMessage) DecodeReader(r io.Reader, maxLen int) error {
 
 func DoHandshakeCurrentVersion(conn net.Conn, deadline time.Time) *HandshakeError {
 	// current protocol version is hardcoded here
-	return DoHandshakeVersion(conn, deadline, 1)
+	return DoHandshakeVersion(conn, deadline, 2)
 }
 
 const HandshakeMessageMaxLen = 16 * 4096

transport/tcp/serve_tcp.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/zrepl/zrepl/config"
 	"github.com/zrepl/zrepl/transport"
+	"github.com/zrepl/zrepl/util/tcpsock"
 )
 
 type ipMapEntry struct {
@@ -44,16 +45,12 @@ func (m *ipMap) Get(ip net.IP) (string, error) {
 }
 
 func TCPListenerFactoryFromConfig(c *config.Global, in *config.TCPServe) (transport.AuthenticatedListenerFactory, error) {
-	addr, err := net.ResolveTCPAddr("tcp", in.Listen)
-	if err != nil {
-		return nil, errors.Wrap(err, "cannot parse listen address")
-	}
 	clientMap, err := ipMapFromConfig(in.Clients)
 	if err != nil {
 		return nil, errors.Wrap(err, "cannot parse client IP map")
 	}
 	lf := func() (transport.AuthenticatedListener, error) {
-		l, err := net.ListenTCP("tcp", addr)
+		l, err := tcpsock.Listen(in.Listen, in.ListenFreeBind)
 		if err != nil {
 			return nil, err
 		}

transport/tls/serve_tls.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"crypto/tls"
 	"fmt"
-	"net"
 	"time"
 
 	"github.com/pkg/errors"
@@ -12,6 +11,7 @@ import (
 	"github.com/zrepl/zrepl/config"
 	"github.com/zrepl/zrepl/tlsconf"
 	"github.com/zrepl/zrepl/transport"
+	"github.com/zrepl/zrepl/util/tcpsock"
 )
 
 type TLSListenerFactory struct{}
@@ -45,12 +45,11 @@ func TLSListenerFactoryFromConfig(c *config.Global, in *config.TLSServe) (transp
 	}
 
 	lf := func() (transport.AuthenticatedListener, error) {
-		l, err := net.Listen("tcp", address)
+		l, err := tcpsock.Listen(address, in.ListenFreeBind)
 		if err != nil {
 			return nil, err
 		}
-		tcpL := l.(*net.TCPListener)
-		tl := tlsconf.NewClientAuthListener(tcpL, clientCA, serverCert, handshakeTimeout)
+		tl := tlsconf.NewClientAuthListener(l, clientCA, serverCert, handshakeTimeout)
 		return &tlsAuthListener{tl, clientCNs}, nil
 	}
 

util/circlog/circlog.go

@@ -27,6 +27,14 @@ type CircularLog struct {
 	mtx sync.Mutex
 }
 
+func MustNewCircularLog(max int) *CircularLog {
+	log, err := NewCircularLog(max)
+	if err != nil {
+		panic(err)
+	}
+	return log
+}
+
 func NewCircularLog(max int) (*CircularLog, error) {
 	if max <= 0 {
 		return nil, fmt.Errorf("max must be positive")

util/limitio/limitio.go

@@ -0,0 +1,36 @@
+package limitio
+
+import "io"
+
+type readCloser struct {
+	read  int64
+	limit int64
+	r     io.ReadCloser
+}
+
+func ReadCloser(rc io.ReadCloser, limit int64) io.ReadCloser {
+	return &readCloser{0, limit, rc}
+}
+
+var _ io.ReadCloser = (*readCloser)(nil)
+
+func (r *readCloser) Read(b []byte) (int, error) {
+
+	if len(b) == 0 {
+		return 0, nil
+	}
+
+	if r.read == r.limit {
+		return 0, io.EOF
+	}
+
+	if r.read+int64(len(b)) >= r.limit {
+		b = b[:int(r.limit-r.read)]
+	}
+
+	readN, err := r.r.Read(b)
+	r.read += int64(readN)
+	return readN, err
+}
+
+func (r *readCloser) Close() error { return r.r.Close() }

util/limitio/limitio_readcloser_test.go

@@ -0,0 +1,44 @@
+package limitio
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type mockRC struct {
+	r      io.Reader
+	closed bool
+}
+
+func newMockRC(r io.Reader) *mockRC { return &mockRC{r, false} }
+
+func (m mockRC) Read(b []byte) (int, error) {
+	if m.closed {
+		return 0, io.ErrClosedPipe
+	}
+	return m.r.Read(b)
+}
+
+func (m *mockRC) Close() error {
+	m.closed = true
+	return nil
+}
+
+func TestReadCloser(t *testing.T) {
+	foobarReader := bytes.NewReader([]byte("foobar2342"))
+	mock := newMockRC(foobarReader)
+	limited := ReadCloser(mock, 6)
+	var buf [20]byte
+	n, err := limited.Read(buf[:])
+	assert.NoError(t, err)
+	assert.Equal(t, 6, n)
+	assert.Equal(t, buf[:n], []byte("foobar"))
+	n, err = limited.Read(buf[:])
+	assert.Equal(t, 0, n)
+	assert.Equal(t, io.EOF, err)
+	limited.Close()
+	assert.True(t, mock.closed)
+}

util/tcpsock/tcpsock.go

@@ -0,0 +1,27 @@
+package tcpsock
+
+import (
+	"context"
+	"net"
+	"syscall"
+)
+
+func Listen(address string, tryFreeBind bool) (*net.TCPListener, error) {
+	control := func(network, address string, c syscall.RawConn) error {
+		if tryFreeBind {
+			if err := freeBind(network, address, c); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+	var listenConfig = net.ListenConfig{
+		Control: control,
+	}
+
+	l, err := listenConfig.Listen(context.Background(), "tcp", address)
+	if err != nil {
+		return nil, err
+	}
+	return l.(*net.TCPListener), nil
+}

util/tcpsock/tcpsock_freebind_freebsd.go

@@ -0,0 +1,25 @@
+// +build freebsd
+
+package tcpsock
+
+import (
+	"fmt"
+	"syscall"
+)
+
+func freeBind(network, address string, c syscall.RawConn) error {
+	var err, sockerr error
+	err = c.Control(func(fd uintptr) {
+		if network == "tcp6" {
+			sockerr = syscall.SetsockoptInt(int(fd), syscall.IPPROTO_IPV6, syscall.IPV6_BINDANY, 1)
+		} else if network == "tcp4" {
+			sockerr = syscall.SetsockoptInt(int(fd), syscall.IPPROTO_IP, syscall.IP_BINDANY, 1)
+		} else {
+			sockerr = fmt.Errorf("expecting 'tcp6' or 'tcp4', got %q", network)
+		}
+	})
+	if err != nil {
+		return err
+	}
+	return sockerr
+}

util/tcpsock/tcpsock_freebind_linux.go

@@ -0,0 +1,19 @@
+// +build linux
+
+package tcpsock
+
+import (
+	"syscall"
+)
+
+func freeBind(network, address string, c syscall.RawConn) error {
+	var err, sockerr error
+	err = c.Control(func(fd uintptr) {
+		// apparently, this works for both IPv4 and IPv6
+		sockerr = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_FREEBIND, 1)
+	})
+	if err != nil {
+		return err
+	}
+	return sockerr
+}

util/tcpsock/tcpsock_freebind_unsupported.go

@@ -0,0 +1,12 @@
+// +build !linux,!freebsd
+
+package tcpsock
+
+import (
+	"fmt"
+	"syscall"
+)
+
+func freeBind(network, address string, c syscall.RawConn) error {
+	return fmt.Errorf("IP_FREEBIND equivalent functionality not supported  on this platform")
+}

zfs/encryption.go

@@ -0,0 +1,71 @@
+package zfs
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+	"sync"
+
+	"github.com/pkg/errors"
+
+	"github.com/zrepl/zrepl/util/envconst"
+)
+
+var encryptionCLISupport struct {
+	once      sync.Once
+	supported bool
+	err       error
+}
+
+func EncryptionCLISupported(ctx context.Context) (bool, error) {
+	encryptionCLISupport.once.Do(func() {
+		// "feature discovery"
+		cmd := exec.Command("zfs", "load-key")
+		output, err := cmd.CombinedOutput()
+		if ee, ok := err.(*exec.ExitError); !ok || ok && !ee.Exited() {
+			encryptionCLISupport.err = errors.Wrap(err, "native encryption cli support feature check failed")
+		}
+		def := strings.Contains(string(output), "load-key") && strings.Contains(string(output), "keylocation")
+		encryptionCLISupport.supported = envconst.Bool("ZREPL_EXPERIMENTAL_ZFS_ENCRYPTION_CLI_SUPPORTED", def)
+		debug("encryption cli feature check complete %#v", &encryptionCLISupport)
+	})
+	return encryptionCLISupport.supported, encryptionCLISupport.err
+}
+
+// returns false, nil if encryption is not supported
+func ZFSGetEncryptionEnabled(ctx context.Context, fs string) (enabled bool, err error) {
+	defer func(e *error) {
+		if *e != nil {
+			*e = fmt.Errorf("zfs get encryption enabled fs=%q: %s", fs, *e)
+		}
+	}(&err)
+	if supp, err := EncryptionCLISupported(ctx); err != nil {
+		return false, err
+	} else if !supp {
+		return false, nil
+	}
+
+	if err := validateZFSFilesystem(fs); err != nil {
+		return false, err
+	}
+
+	props, err := zfsGet(fs, []string{"encryption"}, sourceAny)
+	if err != nil {
+		return false, errors.Wrap(err, "cannot get `encryption` property")
+	}
+	val := props.Get("encryption")
+	switch val {
+	case "":
+		panic("zfs get should return a value for `encryption`")
+	case "-":
+		return false, errors.New("`encryption` property should never be \"-\"")
+	case "off":
+		return false, nil
+	default:
+		// we don't want to hardcode the cipher list, and we checked for != 'off'
+		// ==> assume any other value means encryption is enabled
+		// TODO add test to OpenZFS test suite
+		return true, nil
+	}
+}

zfs/holds.go

@@ -0,0 +1,307 @@
+package zfs
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"sort"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"github.com/pkg/errors"
+
+	"github.com/zrepl/zrepl/util/envconst"
+)
+
+// no need for feature tests, holds have been around forever
+
+func validateNotEmpty(field, s string) error {
+	if s == "" {
+		return fmt.Errorf("`%s` must not be empty", field)
+	}
+	return nil
+}
+
+// returned err != nil is guaranteed to represent invalid hold tag
+func ValidHoldTag(tag string) error {
+	maxlen := envconst.Int("ZREPL_ZFS_MAX_HOLD_TAG_LEN", 256-1) // 256 include NULL byte, from module/zfs/dsl_userhold.c
+	if len(tag) > maxlen {
+		return fmt.Errorf("hold tag %q exceeds max length of %d", tag, maxlen)
+	}
+	return nil
+}
+
+// Idemptotent: does not return an error if the tag already exists
+func ZFSHold(ctx context.Context, fs string, v ZFSSendArgVersion, tag string) error {
+	if err := v.ValidateInMemory(fs); err != nil {
+		return errors.Wrap(err, "invalid version")
+	}
+	if !v.IsSnapshot() {
+		return errors.Errorf("can only hold snapshots, got %s", v.RelName)
+	}
+
+	if err := validateNotEmpty("tag", tag); err != nil {
+		return err
+	}
+	fullPath := v.FullPath(fs)
+	output, err := exec.CommandContext(ctx, "zfs", "hold", tag, fullPath).CombinedOutput()
+	if err != nil {
+		if bytes.Contains(output, []byte("tag already exists on this dataset")) {
+			goto success
+		}
+		return &ZFSError{output, errors.Wrapf(err, "cannot hold %q", fullPath)}
+	}
+success:
+	return nil
+}
+
+func ZFSHolds(ctx context.Context, fs, snap string) ([]string, error) {
+	if err := validateZFSFilesystem(fs); err != nil {
+		return nil, errors.Wrap(err, "`fs` is not a valid filesystem path")
+	}
+	if snap == "" {
+		return nil, fmt.Errorf("`snap` must not be empty")
+	}
+	dp := fmt.Sprintf("%s@%s", fs, snap)
+	output, err := exec.CommandContext(ctx, "zfs", "holds", "-H", dp).CombinedOutput()
+	if err != nil {
+		return nil, &ZFSError{output, errors.Wrap(err, "zfs holds failed")}
+	}
+	scan := bufio.NewScanner(bytes.NewReader(output))
+	var tags []string
+	for scan.Scan() {
+		// NAME              TAG  TIMESTAMP
+		comps := strings.SplitN(scan.Text(), "\t", 3)
+		if len(comps) != 3 {
+			return nil, fmt.Errorf("zfs holds: unexpected output\n%s", output)
+		}
+		if comps[0] != dp {
+			return nil, fmt.Errorf("zfs holds: unexpected output: expecting %q as first component, got %q\n%s", dp, comps[0], output)
+		}
+		tags = append(tags, comps[1])
+	}
+	return tags, nil
+}
+
+// Idempotent: if the hold doesn't exist, this is not an error
+func ZFSRelease(ctx context.Context, tag string, snaps ...string) error {
+	cumLens := make([]int, len(snaps))
+	for i := 1; i < len(snaps); i++ {
+		cumLens[i] = cumLens[i-1] + len(snaps[i])
+	}
+	maxInvocationLen := 12 * os.Getpagesize()
+	var noSuchTagLines, otherLines []string
+	for i := 0; i < len(snaps); {
+		var j = i
+		for ; j < len(snaps); j++ {
+			if cumLens[j]-cumLens[i] > maxInvocationLen {
+				break
+			}
+		}
+		args := []string{"release", tag}
+		args = append(args, snaps[i:j]...)
+		output, err := exec.CommandContext(ctx, "zfs", args...).CombinedOutput()
+		if pe, ok := err.(*os.PathError); err != nil && ok && pe.Err == syscall.E2BIG {
+			maxInvocationLen = maxInvocationLen / 2
+			continue
+		}
+		maxInvocationLen = maxInvocationLen + os.Getpagesize()
+		i = j
+
+		// even if release fails for datasets where there's no hold with the tag
+		// the hold is still released on datasets which have a hold with the tag
+		// FIXME verify this in a platformtest
+		// => screen-scrape
+		scan := bufio.NewScanner(bytes.NewReader(output))
+		for scan.Scan() {
+			line := scan.Text()
+			if strings.Contains(line, "no such tag on this dataset") {
+				noSuchTagLines = append(noSuchTagLines, line)
+			} else {
+				otherLines = append(otherLines, line)
+			}
+		}
+
+	}
+	if debugEnabled {
+		debug("zfs release: no such tag lines=%v otherLines=%v", noSuchTagLines, otherLines)
+	}
+	if len(otherLines) > 0 {
+		return fmt.Errorf("unknown zfs error while releasing hold with tag %q: unidentified stderr lines\n%s", tag, strings.Join(otherLines, "\n"))
+	}
+	return nil
+}
+
+// Idempotent: if the hold doesn't exist, this is not an error
+func ZFSReleaseAllOlderAndIncludingGUID(ctx context.Context, fs string, snapOrBookmarkGuid uint64, tag string) error {
+	return doZFSReleaseAllOlderAndIncOrExcludingGUID(ctx, fs, snapOrBookmarkGuid, tag, true)
+}
+
+// Idempotent: if the hold doesn't exist, this is not an error
+func ZFSReleaseAllOlderThanGUID(ctx context.Context, fs string, snapOrBookmarkGuid uint64, tag string) error {
+	return doZFSReleaseAllOlderAndIncOrExcludingGUID(ctx, fs, snapOrBookmarkGuid, tag, false)
+}
+
+type zfsReleaseAllOlderAndIncOrExcludingGUIDZFSListLine struct {
+	entityType EntityType
+	name       string
+	createtxg  uint64
+	guid       uint64
+	userrefs   uint64 // always 0 for bookmarks
+}
+
+func doZFSReleaseAllOlderAndIncOrExcludingGUID(ctx context.Context, fs string, snapOrBookmarkGuid uint64, tag string, includeGuid bool) error {
+	// TODO channel program support still unreleased but
+	// might be a huge performance improvement
+	// https://github.com/zfsonlinux/zfs/pull/7902/files
+
+	if err := validateZFSFilesystem(fs); err != nil {
+		return errors.Wrap(err, "`fs` is not a valid filesystem path")
+	}
+	if tag == "" {
+		return fmt.Errorf("`tag` must not be empty`")
+	}
+
+	output, err := exec.CommandContext(ctx,
+		"zfs", "list", "-o", "type,name,createtxg,guid,userrefs",
+		"-H", "-t", "snapshot,bookmark", "-r", "-d", "1", fs).CombinedOutput()
+	if err != nil {
+		return &ZFSError{output, errors.Wrap(err, "cannot list snapshots and their userrefs")}
+	}
+
+	lines, err := doZFSReleaseAllOlderAndIncOrExcludingGUIDParseListOutput(output)
+	if err != nil {
+		return errors.Wrap(err, "unexpected ZFS output")
+	}
+
+	releaseSnaps, err := doZFSReleaseAllOlderAndIncOrExcludingGUIDFindSnapshots(snapOrBookmarkGuid, includeGuid, lines)
+	if err != nil {
+		return err
+	}
+
+	if len(releaseSnaps) == 0 {
+		return nil
+	}
+	return ZFSRelease(ctx, tag, releaseSnaps...)
+}
+
+func doZFSReleaseAllOlderAndIncOrExcludingGUIDParseListOutput(output []byte) ([]zfsReleaseAllOlderAndIncOrExcludingGUIDZFSListLine, error) {
+
+	scan := bufio.NewScanner(bytes.NewReader(output))
+
+	var lines []zfsReleaseAllOlderAndIncOrExcludingGUIDZFSListLine
+
+	for scan.Scan() {
+		const numCols = 5
+		comps := strings.SplitN(scan.Text(), "\t", numCols)
+		if len(comps) != numCols {
+			return nil, fmt.Errorf("not %d columns\n%s", numCols, output)
+		}
+		dstype := comps[0]
+		name := comps[1]
+
+		var entityType EntityType
+		switch dstype {
+		case "snapshot":
+			entityType = EntityTypeSnapshot
+		case "bookmark":
+			entityType = EntityTypeBookmark
+		default:
+			return nil, fmt.Errorf("column 0 is %q, expecting \"snapshot\" or \"bookmark\"", dstype)
+		}
+
+		createtxg, err := strconv.ParseUint(comps[2], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("cannot parse createtxg %q: %s\n%s", comps[2], err, output)
+		}
+
+		guid, err := strconv.ParseUint(comps[3], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("cannot parse guid %q: %s\n%s", comps[3], err, output)
+		}
+
+		var userrefs uint64
+		switch entityType {
+		case EntityTypeBookmark:
+			if comps[4] != "-" {
+				return nil, fmt.Errorf("entity type \"bookmark\" should have userrefs=\"-\", got %q", comps[4])
+			}
+			userrefs = 0
+		case EntityTypeSnapshot:
+			userrefs, err = strconv.ParseUint(comps[4], 10, 64) // shadow
+			if err != nil {
+				return nil, fmt.Errorf("cannot parse userrefs %q: %s\n%s", comps[4], err, output)
+			}
+		default:
+			panic(entityType)
+		}
+
+		lines = append(lines, zfsReleaseAllOlderAndIncOrExcludingGUIDZFSListLine{
+			entityType: entityType,
+			name:       name,
+			createtxg:  createtxg,
+			guid:       guid,
+			userrefs:   userrefs,
+		})
+	}
+
+	return lines, nil
+
+}
+
+func doZFSReleaseAllOlderAndIncOrExcludingGUIDFindSnapshots(snapOrBookmarkGuid uint64, includeGuid bool, lines []zfsReleaseAllOlderAndIncOrExcludingGUIDZFSListLine) (releaseSnaps []string, err error) {
+
+	// sort lines by createtxg,(snap < bookmark)
+	// we cannot do this using zfs list -s because `type` is not a
+	sort.Slice(lines, func(i, j int) (less bool) {
+		if lines[i].createtxg == lines[j].createtxg {
+			iET := func(t EntityType) int {
+				switch t {
+				case EntityTypeSnapshot:
+					return 0
+				case EntityTypeBookmark:
+					return 1
+				default:
+					panic("unepxected entity type " + t.String())
+				}
+			}
+			return iET(lines[i].entityType) < iET(lines[j].entityType)
+		}
+		return lines[i].createtxg < lines[j].createtxg
+	})
+
+	// iterate over snapshots oldest to newest and collect snapshots that have holds and
+	// are older than (inclusive or exclusive, depends on includeGuid) a snapshot or bookmark
+	// with snapOrBookmarkGuid
+	foundGuid := false
+	for _, line := range lines {
+		if line.guid == snapOrBookmarkGuid {
+			foundGuid = true
+		}
+		if line.userrefs > 0 {
+			if !foundGuid || (foundGuid && includeGuid) {
+				// only snapshots have userrefs > 0, no need to check entityType
+				releaseSnaps = append(releaseSnaps, line.name)
+			}
+		}
+		if foundGuid {
+			// The secondary key in sorting (snap < bookmark) guarantees that we
+			//   A) either found the snapshot with snapOrBoomkarkGuid
+			//   B) or no snapshot with snapGuid exists, but one or more bookmarks of it exists
+			// In the case of A, we already added the snapshot to releaseSnaps if includeGuid requests it,
+			// and can ignore possible subsequent bookmarks of the snapshot.
+			// In the case of B, there is nothing to add to releaseSnaps.
+			break
+		}
+	}
+
+	if !foundGuid {
+		return nil, fmt.Errorf("cannot find snapshot or bookmark with guid %v", snapOrBookmarkGuid)
+	}
+
+	return releaseSnaps, nil
+}

zfs/holds_test.go

@@ -0,0 +1,38 @@
+package zfs
+
+import (
+	"testing"
+
+	"github.com/kr/pretty"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDoZFSReleaseAllOlderAndIncOrExcludingGUIDFindSnapshots(t *testing.T) {
+
+	// what we test here: sort bookmark #3 before @3
+	// => assert that the function doesn't stop at the first guid match
+	//    (which might be a bookmark, depending on zfs list ordering)
+	//    but instead considers the entire stride of boomarks and snapshots with that guid
+	//
+	// also, throw in unordered createtxg for good measure
+	list, err := doZFSReleaseAllOlderAndIncOrExcludingGUIDParseListOutput(
+		[]byte("snapshot\tfoo@1\t1\t1013001\t1\n" +
+			"snapshot\tfoo@2\t2\t2013002\t1\n" +
+			"bookmark\tfoo#3\t3\t7013003\t-\n" +
+			"snapshot\tfoo@6\t6\t5013006\t1\n" +
+			"snapshot\tfoo@3\t3\t7013003\t1\n" +
+			"snapshot\tfoo@4\t3\t6013004\t1\n" +
+			""),
+	)
+	require.NoError(t, err)
+	t.Log(pretty.Sprint(list))
+	require.Equal(t, 6, len(list))
+	require.Equal(t, EntityTypeBookmark, list[2].entityType)
+
+	releaseSnaps, err := doZFSReleaseAllOlderAndIncOrExcludingGUIDFindSnapshots(7013003, true, list)
+	t.Logf("releasedSnaps = %#v", releaseSnaps)
+	assert.NoError(t, err)
+
+	assert.Equal(t, []string{"foo@1", "foo@2", "foo@3"}, releaseSnaps)
+}

zfs/namecheck.go

@@ -0,0 +1,193 @@
+package zfs
+
+import (
+	"bytes"
+	"fmt"
+	"regexp"
+	"strings"
+	"unicode"
+)
+
+const MaxDatasetNameLen = 256 - 1
+
+type EntityType string
+
+const (
+	EntityTypeFilesystem EntityType = "filesystem"
+	EntityTypeVolume     EntityType = "volume"
+	EntityTypeSnapshot   EntityType = "snapshot"
+	EntityTypeBookmark   EntityType = "bookmark"
+)
+
+func (e EntityType) Validate() error {
+	switch e {
+	case EntityTypeFilesystem:
+		return nil
+	case EntityTypeVolume:
+		return nil
+	case EntityTypeSnapshot:
+		return nil
+	case EntityTypeBookmark:
+		return nil
+	default:
+		return fmt.Errorf("invalid entity type %q", string(e))
+	}
+}
+
+func (e EntityType) MustValidate() {
+	if err := e.Validate(); err != nil {
+		panic(err)
+	}
+}
+
+func (e EntityType) String() string {
+	e.MustValidate()
+	return string(e)
+}
+
+var componentValidChar = regexp.MustCompile(`^[0-9a-zA-Z-_\.: ]+$`)
+
+// From module/zcommon/zfs_namecheck.c
+//
+// Snapshot names must be made up of alphanumeric characters plus the following
+// characters:
+//
+//	[-_.: ]
+//
+func ComponentNamecheck(datasetPathComponent string) error {
+	if len(datasetPathComponent) == 0 {
+		return fmt.Errorf("path component must not be empty")
+	}
+	if len(datasetPathComponent) > MaxDatasetNameLen {
+		return fmt.Errorf("path component must not be longer than %d chars", MaxDatasetNameLen)
+	}
+
+	if !(isASCII(datasetPathComponent)) {
+		return fmt.Errorf("path component must be ASCII")
+	}
+
+	if !componentValidChar.MatchString(datasetPathComponent) {
+		return fmt.Errorf("path component must only contain alphanumeric chars and any in %q", "-_.: ")
+	}
+
+	if datasetPathComponent == "." || datasetPathComponent == ".." {
+		return fmt.Errorf("path component must not be '%s'", datasetPathComponent)
+	}
+
+	return nil
+}
+
+type PathValidationError struct {
+	path       string
+	entityType EntityType
+	msg        string
+}
+
+func (e *PathValidationError) Path() string { return e.path }
+
+func (e *PathValidationError) Error() string {
+	return fmt.Sprintf("invalid %s %q: %s", e.entityType, e.path, e.msg)
+}
+
+// combines
+//
+//    lib/libzfs/libzfs_dataset.c: zfs_validate_name
+//    module/zcommon/zfs_namecheck.c: entity_namecheck
+//
+// The '%' character is not allowed because it's reserved for zfs-internal use
+func EntityNamecheck(path string, t EntityType) (err *PathValidationError) {
+	pve := func(msg string) *PathValidationError {
+		return &PathValidationError{path: path, entityType: t, msg: msg}
+	}
+
+	t.MustValidate()
+
+	// delimiter checks
+	if t != EntityTypeSnapshot && strings.Contains(path, "@") {
+		return pve("snapshot delimiter '@' is not expected here")
+	}
+	if t == EntityTypeSnapshot && !strings.Contains(path, "@") {
+		return pve("missing '@' delimiter in snapshot name")
+	}
+	if t != EntityTypeBookmark && strings.Contains(path, "#") {
+		return pve("bookmark delimiter '#' is not expected here")
+	}
+	if t == EntityTypeBookmark && !strings.Contains(path, "#") {
+		return pve("missing '#' delimiter in bookmark name")
+	}
+
+	// EntityTypeVolume and EntityTypeFilesystem are already covered above
+
+	if strings.Contains(path, "%") {
+		return pve("invalid character '%' in name")
+	}
+
+	// mimic module/zcommon/zfs_namecheck.c: entity_namecheck
+
+	if len(path) > MaxDatasetNameLen {
+		return pve("name too long")
+	}
+
+	if len(path) == 0 {
+		return pve("must not be empty")
+	}
+
+	if !isASCII(path) {
+		return pve("must be ASCII")
+	}
+
+	slashComps := bytes.Split([]byte(path), []byte("/"))
+	bookmarkOrSnapshotDelims := 0
+	for compI, comp := range slashComps {
+
+		snapCount := bytes.Count(comp, []byte("@"))
+		bookCount := bytes.Count(comp, []byte("#"))
+
+		if !(snapCount*bookCount == 0) {
+			panic("implementation error: delimiter checks before this loop must ensure this cannot happen")
+		}
+		bookmarkOrSnapshotDelims += snapCount + bookCount
+		if bookmarkOrSnapshotDelims > 1 {
+			return pve("multiple delimiters '@' or '#' are not allowed")
+		}
+		if bookmarkOrSnapshotDelims == 1 && compI != len(slashComps)-1 {
+			return pve("snapshot or bookmark must not contain '/'")
+		}
+
+		if bookmarkOrSnapshotDelims == 0 {
+			// hot path, all but last component
+			if err := ComponentNamecheck(string(comp)); err != nil {
+				return pve(err.Error())
+			}
+			continue
+		}
+
+		subComps := bytes.FieldsFunc(comp, func(r rune) bool {
+			return r == '#' || r == '@'
+		})
+		if len(subComps) > 2 {
+			panic("implementation error: delimiter checks above should ensure a single bookmark or snapshot delimiter per component")
+		}
+		if len(subComps) != 2 {
+			return pve("empty component, bookmark or snapshot name not allowed")
+		}
+
+		for _, comp := range subComps {
+			if err := ComponentNamecheck(string(comp)); err != nil {
+				return pve(err.Error())
+			}
+		}
+
+	}
+
+	return nil
+}
+
+func isASCII(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] > unicode.MaxASCII {
+			return false
+		}
+	}
+	return true
+}

zfs/namecheck_test.go

@@ -0,0 +1,64 @@
+package zfs
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestEntityNamecheck(t *testing.T) {
+
+	type testcase struct {
+		input      string
+		entityType EntityType
+		ok         bool
+	}
+
+	tcs := []testcase{
+		{"/", EntityTypeFilesystem, false},
+		{"/foo", EntityTypeFilesystem, false},
+		{"/foo@bar", EntityTypeSnapshot, false},
+		{"foo", EntityTypeBookmark, false},
+		{"foo", EntityTypeSnapshot, false},
+		{"foo@bar", EntityTypeBookmark, false},
+		{"foo#bar", EntityTypeSnapshot, false},
+		{"foo#book", EntityTypeBookmark, true},
+		{"foo#book@bar", EntityTypeBookmark, false},
+		{"foo/book@bar", EntityTypeSnapshot, true},
+		{"foo/book#bar", EntityTypeBookmark, true},
+		{"foo/for%idden", EntityTypeFilesystem, false},
+		{"foo/bår", EntityTypeFilesystem, false},
+		{"", EntityTypeFilesystem, false},
+		{"foo/bar@", EntityTypeSnapshot, false},
+		{"foo/bar#", EntityTypeBookmark, false},
+		{"foo/bar#@blah", EntityTypeBookmark, false},
+		{"foo bar/baz bar@blah foo", EntityTypeSnapshot, true},
+		{"foo bar/baz bar@#lah foo", EntityTypeSnapshot, false},
+		{"foo bar/baz bar@@lah foo", EntityTypeSnapshot, false},
+		{"foo bar/baz bar##lah foo", EntityTypeBookmark, false},
+		{"foo bar/baz@blah/foo", EntityTypeSnapshot, false},
+		{"foo bar/baz@blah/foo", EntityTypeFilesystem, false},
+		{"foo/b\tr@ba\tz", EntityTypeSnapshot, false},
+		{"foo/b\tr@baz", EntityTypeSnapshot, false},
+		{"foo/bar@ba\tz", EntityTypeSnapshot, false},
+		{"foo/./bar", EntityTypeFilesystem, false},
+		{"foo/../bar", EntityTypeFilesystem, false},
+		{"foo/bar@..", EntityTypeFilesystem, false},
+		{"foo/bar@.", EntityTypeFilesystem, false},
+		{strings.Repeat("a", MaxDatasetNameLen), EntityTypeFilesystem, true},
+		{strings.Repeat("a", MaxDatasetNameLen) + "a", EntityTypeFilesystem, false},
+		{strings.Repeat("a", MaxDatasetNameLen-2) + "/a", EntityTypeFilesystem, true},
+		{strings.Repeat("a", MaxDatasetNameLen-4) + "/a@b", EntityTypeSnapshot, true},
+		{strings.Repeat("a", MaxDatasetNameLen) + "/a@b", EntityTypeSnapshot, false},
+	}
+
+	for idx := range tcs {
+		t.Run(tcs[idx].input, func(t *testing.T) {
+			tc := tcs[idx]
+			err := EntityNamecheck(tc.input, tc.entityType)
+			if !((err == nil && tc.ok) || (err != nil && !tc.ok)) {
+				t.Errorf("expecting ok=%v but got err=%v", tc.ok, err)
+			}
+		})
+	}
+
+}

zfs/replication_history.go

@@ -1,50 +0,0 @@
-package zfs
-
-import (
-	"fmt"
-
-	"github.com/pkg/errors"
-)
-
-const ReplicationCursorBookmarkName = "zrepl_replication_cursor"
-
-// may return nil for both values, indicating there is no cursor
-func ZFSGetReplicationCursor(fs *DatasetPath) (*FilesystemVersion, error) {
-	versions, err := ZFSListFilesystemVersions(fs, nil)
-	if err != nil {
-		return nil, err
-	}
-	for _, v := range versions {
-		if v.Type == Bookmark && v.Name == ReplicationCursorBookmarkName {
-			return &v, nil
-		}
-	}
-	return nil, nil
-}
-
-func ZFSSetReplicationCursor(fs *DatasetPath, snapname string) (guid uint64, err error) {
-	snapPath := fmt.Sprintf("%s@%s", fs.ToString(), snapname)
-	debug("replication cursor: snap path %q", snapPath)
-	snapProps, err := ZFSGetCreateTXGAndGuid(snapPath)
-	if err != nil {
-		return 0, errors.Wrapf(err, "get properties of %q", snapPath)
-	}
-	bookmarkPath := fmt.Sprintf("%s#%s", fs.ToString(), ReplicationCursorBookmarkName)
-	propsBookmark, err := ZFSGetCreateTXGAndGuid(bookmarkPath)
-	_, bookmarkNotExistErr := err.(*DatasetDoesNotExist)
-	if err != nil && !bookmarkNotExistErr {
-		return 0, errors.Wrap(err, "zfs: replication cursor: get bookmark txg")
-	}
-	if err == nil {
-		if snapProps.CreateTXG < propsBookmark.CreateTXG {
-			return 0, errors.New("zfs: replication cursor: can only be advanced, not set back")
-		}
-		if err := ZFSDestroy(bookmarkPath); err != nil { // FIXME make safer by using new temporary bookmark, then rename, possible with channel programs
-			return 0, errors.Wrap(err, "zfs: replication cursor: destroy current cursor")
-		}
-	}
-	if err := ZFSBookmark(fs, snapname, ReplicationCursorBookmarkName); err != nil {
-		return 0, errors.Wrapf(err, "zfs: replication cursor: create bookmark")
-	}
-	return snapProps.Guid, nil
-}

zfs/resume_token.go

@@ -2,17 +2,26 @@ package zfs
 
 import (
 	"context"
-	"errors"
+	"fmt"
 	"os/exec"
 	"regexp"
 	"strconv"
+	"strings"
+	"sync"
 	"time"
+
+	"github.com/pkg/errors"
+
+	"github.com/zrepl/zrepl/util/envconst"
 )
 
+// NOTE: Update ZFSSendARgs.Validate when changning fields (potentially SECURITY SENSITIVE)
 type ResumeToken struct {
-	HasFromGUID, HasToGUID bool
-	FromGUID, ToGUID       uint64
-	// no support for other fields
+	HasFromGUID, HasToGUID    bool
+	FromGUID, ToGUID          uint64
+	ToName                    string
+	HasCompressOK, CompressOK bool
+	HasRawOk, RawOK           bool
 }
 
 var resumeTokenNVListRE = regexp.MustCompile(`\t(\S+) = (.*)`)
@@ -23,11 +32,134 @@ var ResumeTokenCorruptError = errors.New("resume token is corrupt")
 var ResumeTokenDecodingNotSupported = errors.New("zfs binary does not allow decoding resume token or zrepl cannot scrape zfs output")
 var ResumeTokenParsingError = errors.New("zrepl cannot parse resume token values")
 
+var resumeSendSupportedCheck struct {
+	once      sync.Once
+	supported bool
+	err       error
+}
+
+func ResumeSendSupported() (bool, error) {
+	resumeSendSupportedCheck.once.Do(func() {
+		// "feature discovery"
+		cmd := exec.Command("zfs", "send")
+		output, err := cmd.CombinedOutput()
+		if ee, ok := err.(*exec.ExitError); !ok || ok && !ee.Exited() {
+			resumeSendSupportedCheck.err = errors.Wrap(err, "resumable send cli support feature check failed")
+		}
+		def := strings.Contains(string(output), "receive_resume_token")
+		resumeSendSupportedCheck.supported = envconst.Bool("ZREPL_EXPERIMENTAL_ZFS_SEND_RESUME_SUPPORTED", def)
+		debug("resume send feature check complete %#v", &resumeSendSupportedCheck)
+	})
+	return resumeSendSupportedCheck.supported, resumeSendSupportedCheck.err
+}
+
+var resumeRecvPoolSupportRecheckTimeout = envconst.Duration("ZREPL_ZFS_RESUME_RECV_POOL_SUPPORT_RECHECK_TIMEOUT", 30*time.Second)
+
+type resumeRecvPoolSupportedResult struct {
+	lastCheck time.Time
+	supported bool
+	err       error
+}
+
+var resumeRecvSupportedCheck struct {
+	mtx         sync.RWMutex
+	flagSupport struct {
+		checked   bool
+		supported bool
+		err       error
+	}
+	poolSupported map[string]resumeRecvPoolSupportedResult
+}
+
+// fs == nil only checks for CLI support
+func ResumeRecvSupported(ctx context.Context, fs *DatasetPath) (bool, error) {
+	sup := &resumeRecvSupportedCheck
+	sup.mtx.RLock()
+	defer sup.mtx.RUnlock()
+	upgradeWhile := func(cb func()) {
+		sup.mtx.RUnlock()
+		defer sup.mtx.RLock()
+		sup.mtx.Lock()
+		defer sup.mtx.Unlock()
+		cb()
+	}
+
+	if !sup.flagSupport.checked {
+		output, err := exec.CommandContext(ctx, "zfs", "receive").CombinedOutput()
+		upgradeWhile(func() {
+			sup.flagSupport.checked = true
+			if ee, ok := err.(*exec.ExitError); err != nil && (!ok || ok && !ee.Exited()) {
+				sup.flagSupport.err = err
+			} else {
+				sup.flagSupport.supported = strings.Contains(string(output), "-A <filesystem|volume>")
+			}
+			debug("resume recv cli flag feature check result: %#v", sup.flagSupport)
+		})
+		// fallthrough
+	}
+
+	if sup.flagSupport.err != nil {
+		return false, errors.Wrap(sup.flagSupport.err, "zfs recv feature check for resumable send & recv failed")
+	} else if !sup.flagSupport.supported || fs == nil {
+		return sup.flagSupport.supported, nil
+	}
+
+	// Flag is supported and pool-support is request
+	// Now check for pool support
+
+	pool, err := fs.Pool()
+	if err != nil {
+		return false, errors.Wrap(err, "resume recv check requires pool of dataset")
+	}
+
+	if sup.poolSupported == nil {
+		upgradeWhile(func() {
+			sup.poolSupported = make(map[string]resumeRecvPoolSupportedResult)
+		})
+	}
+
+	var poolSup resumeRecvPoolSupportedResult
+	var ok bool
+	if poolSup, ok = sup.poolSupported[pool]; !ok || // shadow
+		(!poolSup.supported && time.Since(poolSup.lastCheck) > resumeRecvPoolSupportRecheckTimeout) {
+
+		output, err := exec.CommandContext(ctx, "zpool", "get", "-H", "-p", "-o", "value", "feature@extensible_dataset", pool).CombinedOutput()
+		if err != nil {
+			debug("resume recv pool support check result: %#v", sup.flagSupport)
+			poolSup.supported = false
+			poolSup.err = err
+		} else {
+			poolSup.err = nil
+			o := strings.TrimSpace(string(output))
+			poolSup.supported = o == "active" || o == "enabled"
+		}
+		poolSup.lastCheck = time.Now()
+
+		// we take the lock late, so two updaters might check simultaneously, but that shouldn't hurt
+		upgradeWhile(func() {
+			sup.poolSupported[pool] = poolSup
+		})
+		// fallthrough
+	}
+
+	if poolSup.err != nil {
+		return false, errors.Wrapf(poolSup.err, "pool %q check for feature@extensible_dataset feature failed", pool)
+	}
+
+	return poolSup.supported, nil
+}
+
 // Abuse 'zfs send' to decode the resume token
 //
 // FIXME: implement nvlist unpacking in Go and read through libzfs_sendrecv.c
 func ParseResumeToken(ctx context.Context, token string) (*ResumeToken, error) {
 
+	if supported, err := ResumeSendSupported(); err != nil {
+		return nil, err
+	} else if !supported {
+		return nil, ResumeTokenDecodingNotSupported
+	}
+
 	// Example resume tokens:
 	//
 	// From a non-incremental send
@@ -48,8 +180,6 @@ func ParseResumeToken(ctx context.Context, token string) (*ResumeToken, error) {
 	//	toname = pool1/test@b
 	//cannot resume send: 'pool1/test@b' used in the initial send no longer exists
 
-	ctx, cancel := context.WithTimeout(ctx, 500*time.Millisecond)
-	defer cancel()
 	cmd := exec.CommandContext(ctx, ZFS_BINARY, "send", "-nvt", string(token))
 	output, err := cmd.CombinedOutput()
 	if err != nil {
@@ -94,6 +224,20 @@ func ParseResumeToken(ctx context.Context, token string) (*ResumeToken, error) {
 				return nil, ResumeTokenParsingError
 			}
 			rt.HasToGUID = true
+		case "toname":
+			rt.ToName = val
+		case "rawok":
+			rt.HasRawOk = true
+			rt.RawOK, err = strconv.ParseBool(val)
+			if err != nil {
+				return nil, ResumeTokenParsingError
+			}
+		case "compressok":
+			rt.HasCompressOK = true
+			rt.CompressOK, err = strconv.ParseBool(val)
+			if err != nil {
+				return nil, ResumeTokenParsingError
+			}
 		}
 	}
 
@@ -105,17 +249,35 @@ func ParseResumeToken(ctx context.Context, token string) (*ResumeToken, error) {
 
 }
 
-func ZFSGetReceiveResumeToken(fs *DatasetPath) (string, error) {
+// if string is empty and err == nil, the feature is not supported
+func ZFSGetReceiveResumeTokenOrEmptyStringIfNotSupported(ctx context.Context, fs *DatasetPath) (string, error) {
+	if supported, err := ResumeRecvSupported(ctx, fs); err != nil {
+		return "", errors.Wrap(err, "cannot determine zfs recv resume support")
+	} else if !supported {
+		return "", nil
+	}
 	const prop_receive_resume_token = "receive_resume_token"
 	props, err := ZFSGet(fs, []string{prop_receive_resume_token})
 	if err != nil {
 		return "", err
 	}
-	res := props.m[prop_receive_resume_token]
+	res := props.Get(prop_receive_resume_token)
+	debug("%q receive_resume_token=%q", fs.ToString(), res)
 	if res == "-" {
 		return "", nil
 	} else {
 		return res, nil
 	}
-
+}
+
+func (t *ResumeToken) ToNameSplit() (fs *DatasetPath, snapName string, err error) {
+	comps := strings.SplitN(t.ToName, "@", 2)
+	if len(comps) != 2 {
+		return nil, "", fmt.Errorf("resume token field `toname` does not contain @: %q", t.ToName)
+	}
+	dp, err := NewDatasetPath(comps[0])
+	if err != nil {
+		return nil, "", errors.Wrap(err, "resume token field `toname` dataset path invalid")
+	}
+	return dp, comps[1], nil
 }

zfs/resume_token_test.go

@@ -1,68 +0,0 @@
-package zfs_test
-
-import (
-	"context"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-
-	"github.com/zrepl/zrepl/zfs"
-)
-
-type ResumeTokenTest struct {
-	Msg         string
-	Token       string
-	ExpectToken *zfs.ResumeToken
-	ExpectError error
-}
-
-func (rtt *ResumeTokenTest) Test(t *testing.T) {
-	t.Log(rtt.Msg)
-	res, err := zfs.ParseResumeToken(context.TODO(), rtt.Token)
-
-	if rtt.ExpectError != nil {
-		assert.EqualValues(t, rtt.ExpectError, err)
-		return
-	}
-	if rtt.ExpectToken != nil {
-		assert.Nil(t, err)
-		assert.EqualValues(t, rtt.ExpectToken, res)
-		return
-	}
-}
-
-func TestParseResumeToken(t *testing.T) {
-
-	t.SkipNow() // FIXME not compatible with docker
-
-	tbl := []ResumeTokenTest{
-		{
-			Msg:   "normal send (non-incremental)",
-			Token: `1-bf31b879a-b8-789c636064000310a500c4ec50360710e72765a5269740f80cd8e4d3d28a534b18e00024cf86249f5459925acc802a8facbf243fbd3433858161f5ddb9ab1ae7c7466a20c97382e5f312735319180af2f3730cf58166953824c2cc0200cde81651`,
-			ExpectToken: &zfs.ResumeToken{
-				HasToGUID: true,
-				ToGUID:    0x595d9f81aa9dddab,
-			},
-		},
-		{
-			Msg:   "normal send (incremental)",
-			Token: `1-c49b979a2-e0-789c636064000310a501c49c50360710a715e5e7a69766a63040c1eabb735735ce8f8d5400b2d991d4e52765a5269740f82080219f96569c5ac2000720793624f9a4ca92d46206547964fd25f91057f09e37babb88c9bf5503499e132c9f97989bcac050909f9f63a80f34abc421096616007c881d4c`,
-			ExpectToken: &zfs.ResumeToken{
-				HasToGUID:   true,
-				ToGUID:      0x854f02a2dd32cf0d,
-				HasFromGUID: true,
-				FromGUID:    0x595d9f81aa9dddab,
-			},
-		},
-		{
-			Msg:         "corrupted token",
-			Token:       `1-bf31b879a-b8-789c636064000310a500c4ec50360710e72765a5269740f80cd8e4d3d28a534b18e00024cf86249f5459925acc802a8facbf243fbd3433858161f5ddb9ab1ae7c7466a20c97382e5f312735319180af2f3730cf58166953824c2cc0200cd12345`,
-			ExpectError: zfs.ResumeTokenCorruptError,
-		},
-	}
-
-	for _, test := range tbl {
-		test.Test(t)
-	}
-
-}

zfs/versions.go

@@ -88,6 +88,19 @@ type FilesystemVersionFilter interface {
 	Filter(t VersionType, name string) (accept bool, err error)
 }
 
+type closureFilesystemVersionFilter struct {
+	cb func(t VersionType, name string) (accept bool, err error)
+}
+
+func (f *closureFilesystemVersionFilter) Filter(t VersionType, name string) (accept bool, err error) {
+	return f.cb(t, name)
+}
+
+func FilterFromClosure(cb func(t VersionType, name string) (accept bool, err error)) FilesystemVersionFilter {
+	return &closureFilesystemVersionFilter{cb}
+}
+
+// returned versions are sorted by createtxg
 func ZFSListFilesystemVersions(fs *DatasetPath, filter FilesystemVersionFilter) (res []FilesystemVersion, err error) {
 	listResults := make(chan ZFSListResult)