Enable server use as a library

internal/config/config.go

@@ -6,6 +6,7 @@ import (
 	"path/filepath"
 
 	"github.com/BurntSushi/toml"
+	"github.com/gokrazy/rsync/rsyncd"
 )
 
 type Listener struct {
@@ -14,15 +15,9 @@ type Listener struct {
 	AnonSSH        string `toml:"anon_ssh"`
 }
 
-type Module struct {
-	Name string   `toml:"name"`
-	Path string   `toml:"path"`
-	ACL  []string `toml:"acl"`
-}
-
 type Config struct {
-	Listeners []Listener `toml:"listener"`
-	Modules   []Module   `toml:"module"`
+	Listeners []Listener      `toml:"listener"`
+	Modules   []rsyncd.Module `toml:"module"`
 }
 
 func FromString(input string) (*Config, error) {

internal/config/config_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/gokrazy/rsync/internal/config"
+	"github.com/gokrazy/rsync/rsyncd"
 	"github.com/google/go-cmp/cmp"
 )
 
@@ -43,7 +44,7 @@ path = "/non/existant/path"
 	}
 
 	{
-		want := []config.Module{
+		want := []rsyncd.Module{
 			{Name: "interop", Path: "/non/existant/path"},
 		}
 		if diff := cmp.Diff(want, cfg.Modules); diff != "" {

internal/maincmd/maincmd.go

@@ -1,3 +1,7 @@
+// Package maincmd implements a subset of the '$ rsync' CLI surface, namely that it can:
+//   - serve as a server daemon over TCP or SSH (via SSH session stdin/stdout)
+//   - act as "client" CLI for connecting to the server
+//   - Not yet implemented: both "client" and "server" can act as the sender and the receiver
 package maincmd
 
 import (
@@ -12,7 +16,7 @@ import (
 
 	"github.com/gokrazy/rsync/internal/anonssh"
 	"github.com/gokrazy/rsync/internal/config"
-	"github.com/gokrazy/rsync/internal/rsyncd"
+	"github.com/gokrazy/rsync/rsyncd"
 
 	// For profiling and debugging
 	_ "net/http/pprof"
@@ -53,7 +57,10 @@ func Main(ctx context.Context, args []string, stdin io.Reader, stdout io.Writer,
 				return err
 			}
 		}
-		srv := rsyncd.NewServer(cfg.Modules...)
+		srv, err := rsyncd.NewServer(cfg.Modules)
+		if err != nil {
+			return err
+		}
 		rw := readWriter{
 			r: stdin,
 			w: stdout,
@@ -66,7 +73,7 @@ func Main(ctx context.Context, args []string, stdin io.Reader, stdout io.Writer,
 	if opts.Server {
 		// start_server()
 		srv := &rsyncd.Server{}
-		mod := config.Module{
+		mod := rsyncd.Module{
 			Name: "implicit",
 			Path: "/",
 		}
@@ -112,7 +119,7 @@ func Main(ctx context.Context, args []string, stdin io.Reader, stdout io.Writer,
 							AnonSSH: opts.Gokrazy.AnonSSHListen,
 						},
 					},
-					Modules: []config.Module{},
+					Modules: []rsyncd.Module{},
 				}
 			} else {
 				return cfgErr
@@ -158,7 +165,7 @@ func Main(ctx context.Context, args []string, stdin io.Reader, stdout io.Writer,
 		if len(parts) != 2 {
 			return fmt.Errorf("malformed -gokr.modulemap parameter %q, expected <modulename>=<path>", moduleMap)
 		}
-		module := config.Module{
+		module := rsyncd.Module{
 			Name: parts[0],
 			Path: parts[1],
 		}
@@ -187,7 +194,10 @@ func Main(ctx context.Context, args []string, stdin io.Reader, stdout io.Writer,
 		}()
 	}
 
-	srv := rsyncd.NewServer(cfg.Modules...)
+	srv, err := rsyncd.NewServer(cfg.Modules)
+	if err != nil {
+		return err
+	}
 	var ln net.Listener
 	listeners, err := systemdListeners()
 	if err != nil {

internal/maincmd/namespacing.go

@@ -12,10 +12,10 @@ import (
 	"os/exec"
 	"strconv"
 
-	"github.com/gokrazy/rsync/internal/config"
+	"github.com/gokrazy/rsync/rsyncd"
 )
 
-func namespace(modules []config.Module, listen string) error {
+func namespace(modules []rsyncd.Module, listen string) error {
 	if os.Getenv("GOKRAZY_RSYNC_PRIVDROP") != "" {
 		log.Printf("pid %d (privileges dropped)", os.Getpid())
 

internal/maincmd/namespacing_linux.go

@@ -14,7 +14,7 @@ import (
 	"strconv"
 	"syscall"
 
-	"github.com/gokrazy/rsync/internal/config"
+	"github.com/gokrazy/rsync/rsyncd"
 	"golang.org/x/sys/unix"
 )
 
@@ -71,7 +71,7 @@ func pivotRoot(newroot string) error {
 	return nil
 }
 
-func namespace(modules []config.Module, listen string) error {
+func namespace(modules []rsyncd.Module, listen string) error {
 	if os.Getenv("GOKRAZY_RSYNC_NAMESPACE") != "" {
 		log.Printf("pid %d (inside Linux mount/pid namespace)", os.Getpid())
 

internal/rsynctest/rsynctest.go

@@ -20,7 +20,7 @@ import (
 	"github.com/gokrazy/rsync/internal/anonssh"
 	"github.com/gokrazy/rsync/internal/config"
 	"github.com/gokrazy/rsync/internal/maincmd"
-	"github.com/gokrazy/rsync/internal/rsyncd"
+	"github.com/gokrazy/rsync/rsyncd"
 	"github.com/google/go-cmp/cmp"
 	"golang.org/x/sys/unix"
 )
@@ -37,8 +37,8 @@ type TestServer struct {
 
 // InteropModule is a convenience function to define an rsync module named
 // “interop” with the specified path.
-func InteropModule(path string) []config.Module {
-	return []config.Module{
+func InteropModule(path string) []rsyncd.Module {
+	return []rsyncd.Module{
 		{
 			Name: "interop",
 			Path: path,
@@ -60,7 +60,7 @@ func Listener(ln net.Listener) Option {
 	}
 }
 
-func New(t *testing.T, modules []config.Module, opts ...Option) *TestServer {
+func New(t *testing.T, modules []rsyncd.Module, opts ...Option) *TestServer {
 	ts := &TestServer{}
 	for _, opt := range opts {
 		opt(ts)
@@ -70,7 +70,10 @@ func New(t *testing.T, modules []config.Module, opts ...Option) *TestServer {
 			{Rsyncd: "localhost:0"},
 		}
 	}
-	srv := rsyncd.NewServer(modules...)
+	srv, err := rsyncd.NewServer(modules)
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	if ts.listener == nil {
 		ln, err := net.Listen("tcp", "localhost:0")

interop_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/gokrazy/rsync/internal/config"
 	"github.com/gokrazy/rsync/internal/maincmd"
 	"github.com/gokrazy/rsync/internal/rsynctest"
+	"github.com/gokrazy/rsync/rsyncd"
 	"github.com/google/go-cmp/cmp"
 )
 
@@ -357,7 +358,7 @@ func TestInteropRemoteDaemon(t *testing.T) {
 		// in remote daemon mode, rsync needs a config file, so we create one and
 		// set the HOME environment variable such that gokr-rsyncd will pick it up.
 		cfg := config.Config{
-			Modules: []config.Module{
+			Modules: []rsyncd.Module{
 				{Name: "interop", Path: source},
 			},
 		}

internal/rsyncd/flist.go → rsyncd/flist.go

@@ -10,7 +10,6 @@ import (
 	"sync"
 
 	"github.com/gokrazy/rsync"
-	"github.com/gokrazy/rsync/internal/config"
 	"github.com/gokrazy/rsync/internal/rsyncwire"
 )
 
@@ -20,7 +19,7 @@ var (
 )
 
 // rsync/flist.c:send_file_list
-func (st *sendTransfer) sendFileList(mod config.Module, opts *Opts, paths []string) (*fileList, error) {
+func (st *sendTransfer) sendFileList(mod Module, opts *Opts, paths []string) (*fileList, error) {
 	var fileList fileList
 	fec := &rsyncwire.Buffer{}
 

internal/rsyncd/rsyncd.go → rsyncd/rsyncd.go

@@ -3,6 +3,7 @@ package rsyncd
 import (
 	"bufio"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -11,7 +12,6 @@ import (
 	"strings"
 
 	"github.com/gokrazy/rsync"
-	"github.com/gokrazy/rsync/internal/config"
 	"github.com/gokrazy/rsync/internal/rsyncwire"
 )
 
@@ -25,22 +25,34 @@ type sendTransfer struct {
 	lastMatch int64
 }
 
-func NewServer(modules ...config.Module) *Server {
-	return &Server{modules}
+type Module struct {
+	Name string   `toml:"name"`
+	Path string   `toml:"path"`
+	ACL  []string `toml:"acl"`
+}
+
+func NewServer(modules []Module) (*Server, error) {
+	for _, mod := range modules {
+		if err := validateModule(mod); err != nil {
+			return nil, err
+		}
+	}
+
+	return &Server{modules}, nil
 }
 
 type Server struct {
-	modules []config.Module
+	modules []Module
 }
 
-func (s *Server) getModule(requestedModule string) (config.Module, error) {
+func (s *Server) getModule(requestedModule string) (Module, error) {
 	for _, mod := range s.modules {
 		if mod.Name == requestedModule {
 			return mod, nil
 		}
 	}
 
-	return config.Module{}, fmt.Errorf("no such module: %s", requestedModule)
+	return Module{}, fmt.Errorf("no such module: %s", requestedModule)
 }
 
 func (s *Server) formatModuleList() string {
@@ -190,7 +202,7 @@ func (s *Server) HandleDaemonConn(ctx context.Context, conn io.ReadWriter, remot
 	log.Printf("client %v requested rsync module %q", remoteAddr, requestedModule)
 	module, err := s.getModule(requestedModule)
 	if err != nil {
-		fmt.Fprintf(cwr, "@ERROR: Unknown module '%s'\n", requestedModule)
+		fmt.Fprintf(cwr, "@ERROR: Unknown module %q\n", requestedModule)
 		return err
 	}
 
@@ -263,7 +275,7 @@ func (s *Server) HandleDaemonConn(ctx context.Context, conn io.ReadWriter, remot
 }
 
 // handleConn is equivalent to rsync/main.c:start_server
-func (s *Server) HandleConn(module config.Module, rd io.Reader, crd *countingReader, cwr *countingWriter, paths []string, opts *Opts, negotiate bool) (err error) {
+func (s *Server) HandleConn(module Module, rd io.Reader, crd *countingReader, cwr *countingWriter, paths []string, opts *Opts, negotiate bool) (err error) {
 	// “SHOULD be unique to each connection” as per
 	// https://github.com/JohannesBuchner/Jarsync/blob/master/jarsync/rsync.txt
 	//
@@ -396,3 +408,14 @@ func (s *Server) Serve(ctx context.Context, ln net.Listener) error {
 		}()
 	}
 }
+
+func validateModule(mod Module) error {
+	if mod.Name == "" {
+		return errors.New("module has no name")
+	}
+	if mod.Path == "" {
+		return fmt.Errorf("module %q has empty path", mod.Name)
+	}
+
+	return nil
+}