stderr debugging for #517 (tls: bad certificate)

refs #517

cc @asomers

rpc/transportmux/transportmux.go

@@ -7,6 +7,7 @@ package transportmux
 
 import (
 	"context"
+	"os"
 	"sync/atomic"
 	"syscall"
 
@@ -15,6 +16,7 @@ import (
 	"net"
 	"time"
 
+	"github.com/kr/pretty"
 	"github.com/zrepl/zrepl/daemon/logging"
 	"github.com/zrepl/zrepl/logger"
 	"github.com/zrepl/zrepl/transport"
@@ -151,6 +153,7 @@ func Demux(ctx context.Context, rawListener transport.AuthenticatedListener, lab
 
 			rawConn, err := rawListener.Accept(ctx)
 			if err != nil {
+				fmt.Fprintf(os.Stderr, "transportmux.Demux: rawListener.Accept() returned error: %T %s\n%s\n", err, err, pretty.Sprint(err))
 				if ctx.Err() != nil {
 					return
 				}

rpc/versionhandshake/versionhandshake.go

@@ -10,9 +10,12 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"os"
 	"strings"
 	"time"
 	"unicode/utf8"
+
+	"github.com/kr/pretty"
 )
 
 type HandshakeMessage struct {
@@ -93,6 +96,7 @@ func (m *HandshakeMessage) Encode() ([]byte, error) {
 func (m *HandshakeMessage) DecodeReader(r io.Reader, maxLen int) error {
 	var lenAndSpace [11]byte
 	if _, err := io.ReadFull(r, lenAndSpace[:]); err != nil {
+		fmt.Fprintf(os.Stderr, "HandshakeMessage.DecodeReader error: %T\n%s", err, pretty.Sprint(err))
 		return hsIOErr(err, "error reading protocol banner length: %s", err)
 	}
 	if !utf8.Valid(lenAndSpace[:]) {

rpc/versionhandshake/versionhandshake_transport_wrappers.go

@@ -2,7 +2,9 @@ package versionhandshake
 
 import (
 	"context"
+	"fmt"
 	"net"
+	"os"
 	"time"
 
 	"github.com/zrepl/zrepl/transport"
@@ -23,6 +25,7 @@ func (c HandshakeConnecter) Connect(ctx context.Context) (transport.Wire, error)
 		dl = time.Now().Add(c.timeout)
 	}
 	if err := DoHandshakeCurrentVersion(conn, dl); err != nil {
+		fmt.Fprintf(os.Stderr, "HandshakeConnecter error: %T\n\t%s\n\t%v\n\t%#v\n\n", err, err, err, err)
 		conn.Close()
 		return nil, err
 	}