experiment: zync: an rsync-like tool for ZFS datasets (re-uses zrepl abstractions)

Local sync and sync over SSH seems to work.
The sshdirect transport might be interesting / re-usable for zrepl as well, although we'd still need some kind of locking in that case.

zync/transport/sshdirect/serve.go

@@ -0,0 +1,91 @@
+package sshdirect
+
+import (
+	"bytes"
+	"io"
+	"log"
+	"net"
+	"os"
+	"time"
+
+	"github.com/hashicorp/yamux"
+)
+
+type ServeConn struct {
+	stdin, stdout *os.File
+}
+
+var _ net.Conn = (*ServeConn)(nil)
+
+func ServeStdin() (net.Listener, error) {
+
+	conn := &ServeConn{
+		stdin:  os.Stdin,
+		stdout: os.Stdout,
+	}
+
+	var buf bytes.Buffer
+	buf.Write(banner_msg)
+	if _, err := io.Copy(conn, &buf); err != nil {
+		log.Printf("error sending confirm message: %s", err)
+		conn.Close()
+		return nil, err
+	}
+	buf.Reset()
+	if _, err := io.CopyN(&buf, conn, int64(len(begin_msg))); err != nil {
+		log.Printf("error reading begin message: %s", err)
+		conn.Close()
+		return nil, err
+	}
+
+	return yamux.Server(conn, nil)
+}
+
+func (c *ServeConn) Read(p []byte) (int, error) {
+	return c.stdin.Read(p)
+}
+
+func (c *ServeConn) Write(p []byte) (int, error) {
+	return c.stdout.Write(p)
+}
+
+func (f *ServeConn) Close() (err error) {
+	e1 := f.stdin.Close()
+	e2 := f.stdout.Close()
+	// FIXME merge errors
+	if e1 != nil {
+		return e1
+	}
+	return e2
+}
+
+func (f *ServeConn) SetReadDeadline(t time.Time) error {
+	return f.stdin.SetReadDeadline(t)
+}
+
+func (f *ServeConn) SetWriteDeadline(t time.Time) error {
+	return f.stdout.SetReadDeadline(t)
+}
+
+func (f *ServeConn) SetDeadline(t time.Time) error {
+	// try both...
+	werr := f.SetWriteDeadline(t)
+	rerr := f.SetReadDeadline(t)
+	if werr != nil {
+		return werr
+	}
+	if rerr != nil {
+		return rerr
+	}
+	return nil
+}
+
+type serveAddr struct{}
+
+const GoNetwork string = "sshdirect"
+
+func (serveAddr) Network() string { return GoNetwork }
+func (serveAddr) String() string  { return "???" }
+
+func (f *ServeConn) LocalAddr() net.Addr  { return serveAddr{} }
+func (f *ServeConn) RemoteAddr() net.Addr { return serveAddr{} }