client: fix module listing via rsync daemon protocol

It worked with SSH, but not via daemon protocol.
The newly added test covers this.

integration/interop/interop_test.go

@@ -60,7 +60,7 @@ func TestTridgeRsyncVersion(t *testing.T) {
 	}
 }
 
-func TestModuleListing(t *testing.T) {
+func TestModuleListingServer(t *testing.T) {
 	t.Parallel()
 
 	rsyncBin := rsynctest.TridgeOrGTFO(t, "TODO: add reason")
@@ -90,6 +90,30 @@ func TestModuleListing(t *testing.T) {
 	}
 }
 
+func TestModuleListingClient(t *testing.T) {
+	t.Parallel()
+
+	tmp := t.TempDir()
+
+	// start a server to sync from
+	srv := rsynctest.New(t, rsynctest.InteropModule(tmp))
+
+	// request module list
+	args := []string{
+		"gokr-rsync",
+		"-aH",
+		"rsync://localhost:" + srv.Port + "/",
+	}
+	var stdout bytes.Buffer
+	if _, err := maincmd.Main(t.Context(), args, os.Stdin, &stdout, &stdout, nil); err != nil {
+		t.Fatal(err)
+	}
+
+	if want := "interop\tinterop"; !strings.Contains(stdout.String(), want) {
+		t.Fatalf("rsync output unexpectedly did not contain %q:\n%s", want, stdout.String())
+	}
+}
+
 func TestInterop(t *testing.T) {
 	t.Parallel()
 

internal/maincmd/clientmaincmd.go

@@ -99,9 +99,13 @@ func rsyncMain(osenv receiver.Osenv, opts *rsyncopts.Options, sources []string,
 		}
 		negotiate := true
 		if daemonConnection != 0 {
-			if err := startInbandExchange(opts, conn, module, path); err != nil {
+			done, err := startInbandExchange(osenv, opts, conn, module, path)
+			if err != nil {
 				return nil, err
 			}
+			if done {
+				return nil, nil
+			}
 			negotiate = false // already done
 		}
 		stats, err := clientRun(osenv, opts, conn, other, negotiate)

internal/maincmd/clientserver.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"io"
 	"net"
-	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -35,17 +34,18 @@ func socketClient(osenv receiver.Osenv, opts *rsyncopts.Options, host string, pa
 	if err != nil {
 		return nil, err
 	}
-	if path == "" {
-		return nil, fmt.Errorf("empty remote path")
-	}
 	module := path
 	if idx := strings.IndexByte(module, '/'); idx > -1 {
 		module = module[:idx]
 	}
 	log.Printf("rsync module %q, path %q", module, path)
-	if err := startInbandExchange(opts, conn, module, path); err != nil {
+	done, err := startInbandExchange(osenv, opts, conn, module, path)
+	if err != nil {
 		return nil, err
 	}
+	if done {
+		return nil, nil
+	}
 	stats, err := clientRun(osenv, opts, conn, dest, false)
 	if err != nil {
 		return nil, err
@@ -54,7 +54,7 @@ func socketClient(osenv receiver.Osenv, opts *rsyncopts.Options, host string, pa
 }
 
 // rsync/clientserver.c:start_inband_exchange
-func startInbandExchange(opts *rsyncopts.Options, conn io.ReadWriter, module, path string) error {
+func startInbandExchange(osenv receiver.Osenv, opts *rsyncopts.Options, conn io.ReadWriter, module, path string) (done bool, _ error) {
 	rd := bufio.NewReader(conn)
 
 	// send client greeting
@@ -63,23 +63,23 @@ func startInbandExchange(opts *rsyncopts.Options, conn io.ReadWriter, module, pa
 	// read server greeting
 	serverGreeting, err := rd.ReadString('\n')
 	if err != nil {
-		return fmt.Errorf("ReadString: %v", err)
+		return false, fmt.Errorf("ReadString: %v", err)
 	}
 	serverGreeting = strings.TrimSpace(serverGreeting)
 	const serverGreetingPrefix = "@RSYNCD: "
 	if !strings.HasPrefix(serverGreeting, serverGreetingPrefix) {
-		return fmt.Errorf("invalid server greeting: got %q", serverGreeting)
+		return false, fmt.Errorf("invalid server greeting: got %q", serverGreeting)
 	}
 	// protocol negotiation: require at least version 27
 	serverGreeting = strings.TrimPrefix(serverGreeting, serverGreetingPrefix)
 	var remoteProtocol, remoteSub int32
 	if _, err := fmt.Sscanf(serverGreeting, "%d.%d", &remoteProtocol, &remoteSub); err != nil {
 		if _, err := fmt.Sscanf(serverGreeting, "%d", &remoteProtocol); err != nil {
-			return fmt.Errorf("reading server greeting: %v", err)
+			return false, fmt.Errorf("reading server greeting: %v", err)
 		}
 	}
 	if remoteProtocol < 27 {
-		return fmt.Errorf("server version %d too old", remoteProtocol)
+		return false, fmt.Errorf("server version %d too old", remoteProtocol)
 	}
 
 	log.Printf("(Client) Protocol versions: remote=%d, negotiated=%d", remoteProtocol, rsync.ProtocolVersion)
@@ -90,28 +90,31 @@ func startInbandExchange(opts *rsyncopts.Options, conn io.ReadWriter, module, pa
 	for {
 		line, err := rd.ReadString('\n')
 		if err != nil {
-			return fmt.Errorf("did not get server startup line: %v", err)
+			return false, fmt.Errorf("did not get server startup line: %v", err)
 		}
 		line = strings.TrimSpace(line)
+		log.Printf("read line: %q", line)
 
 		if strings.HasPrefix(line, "@RSYNCD: AUTHREQD ") {
 			// TODO: implement support for authentication
-			return fmt.Errorf("authentication not yet implemented")
+			return false, fmt.Errorf("authentication not yet implemented")
 		}
 
 		if line == "@RSYNCD: OK" {
 			break
 		}
 
-		// TODO: @RSYNCD: EXIT after listing modules
+		if line == "@RSYNCD: EXIT" {
+			return true, nil
+		}
 
 		if strings.HasPrefix(line, "@ERROR") {
-			fmt.Fprintf(os.Stderr, "%s\n", line)
-			return fmt.Errorf("abort (rsync fatal error)")
+			fmt.Fprintf(osenv.Stderr, "%s\n", line)
+			return false, fmt.Errorf("abort (rsync fatal error)")
 		}
 
 		// print rsync server message of the day (MOTD)
-		fmt.Fprintf(os.Stdout, "%s\n", line)
+		fmt.Fprintf(osenv.Stdout, "%s\n", line)
 	}
 
 	sargv := serverOptions(opts)
@@ -125,5 +128,5 @@ func startInbandExchange(opts *rsyncopts.Options, conn io.ReadWriter, module, pa
 	}
 	fmt.Fprintf(conn, "\n")
 
-	return nil
+	return false, nil
 }