ipn: misc cleanup

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnserver/server.go

@@ -76,16 +76,21 @@ func pump(logf logger.Logf, ctx context.Context, bs *ipn.BackendServer, s net.Co
 	}
 }
 
-func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e wgengine.Engine) error {
-	bo := backoff.Backoff{Name: "ipnserver"}
+func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e wgengine.Engine) (err error) {
+	runDone := make(chan error, 1)
+	defer func() { runDone <- err }()
 
 	listen, _, err := safesocket.Listen(opts.SocketPath, uint16(opts.Port))
 	if err != nil {
 		return fmt.Errorf("safesocket.Listen: %v", err)
 	}
+
 	// Go listeners can't take a context, close it instead.
 	go func() {
-		<-rctx.Done()
+		select {
+		case <-rctx.Done():
+		case <-runDone:
+		}
 		listen.Close()
 	}()
 	logf("Listening on %v\n", listen.Addr())
@@ -130,13 +135,11 @@ func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e w
 		})
 	}
 
-	var oldS net.Conn
-	//lint:ignore SA4006 ctx is never used, but has to be defined so
-	// that it can be assigned to in the following for loop. It's a
-	// bit of necessary code convolution to work around Go's variable
-	// shadowing rules.
-	ctx, cancel := context.WithCancel(rctx)
-
+	var (
+		oldS   net.Conn
+		ctx    context.Context
+		cancel context.CancelFunc
+	)
 	stopAll := func() {
 		// Currently we only support one client connection at a time.
 		// Theoretically we could allow multiple clients, by passing
@@ -150,6 +153,8 @@ func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e w
 		}
 	}
 
+	bo := backoff.Backoff{Name: "ipnserver"}
+
 	for i := 1; rctx.Err() == nil; i++ {
 		s, err = listen.Accept()
 		if err != nil {
@@ -160,10 +165,11 @@ func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e w
 		logf("%d: Incoming control connection.\n", i)
 		stopAll()
 
-		ctx, cancel = context.WithCancel(context.Background())
+		ctx, cancel = context.WithCancel(rctx)
 		oldS = s
 
 		go func(ctx context.Context, bs *ipn.BackendServer, s net.Conn, i int) {
+			// TODO: move this prefixing-Logf code into a new helper in types/logger?
 			si := fmt.Sprintf("%d: ", i)
 			pump(func(fmt string, args ...interface{}) {
 				logf(si+fmt, args...)

ipn/local.go

@@ -71,7 +71,7 @@ func NewLocalBackend(logf logger.Logf, logid string, store StateStore, e wgengin
 		logf("skipping portlist: %s\n", err)
 	}
 
-	b := LocalBackend{
+	b := &LocalBackend{
 		logf:         logf,
 		e:            e,
 		store:        store,
@@ -86,7 +86,7 @@ func NewLocalBackend(logf logger.Logf, logid string, store StateStore, e wgengin
 		go b.runPoller()
 	}
 
-	return &b, nil
+	return b, nil
 }
 
 func (b *LocalBackend) Shutdown() {

ipn/message.go

@@ -49,7 +49,7 @@ type Command struct {
 type BackendServer struct {
 	logf          logger.Logf
 	b             Backend              // the Backend we are serving up
-	sendNotifyMsg func(b []byte) // send a notification message
+	sendNotifyMsg func(jsonMsg []byte) // send a notification message
 	GotQuit       bool                 // a Quit command was received
 }
 
@@ -70,13 +70,14 @@ func (bs *BackendServer) send(n Notify) {
 	bs.sendNotifyMsg(b)
 }
 
-// Inform the BackendServer of an incoming message.
+// GotCommandMsg parses the incoming message b as a JSON Command and
+// calls GotCommand with it.
 func (bs *BackendServer) GotCommandMsg(b []byte) error {
-	cmd := Command{}
-	if err := json.Unmarshal(b, &cmd); err != nil {
+	cmd := &Command{}
+	if err := json.Unmarshal(b, cmd); err != nil {
 		return err
 	}
-	return bs.GotCommand(&cmd)
+	return bs.GotCommand(cmd)
 }
 
 func (bs *BackendServer) GotCommand(cmd *Command) error {
@@ -130,11 +131,11 @@ func (bs *BackendServer) Reset() error {
 
 type BackendClient struct {
 	logf           logger.Logf
-	sendCommandMsg func(b []byte)
-	notify         func(n Notify)
+	sendCommandMsg func(jsonb []byte)
+	notify         func(Notify)
 }
 
-func NewBackendClient(logf logger.Logf, sendCommandMsg func(b []byte)) *BackendClient {
+func NewBackendClient(logf logger.Logf, sendCommandMsg func(jsonb []byte)) *BackendClient {
 	return &BackendClient{
 		logf:           logf,
 		sendCommandMsg: sendCommandMsg,
@@ -203,7 +204,8 @@ func (bc *BackendClient) FakeExpireAfter(x time.Duration) {
 	bc.send(Command{FakeExpireAfter: &FakeExpireAfterArgs{Duration: x}})
 }
 
-const MSG_MAX = 1024 * 1024
+// MaxMessageSize is the maximum message size, in bytes.
+const MaxMessageSize = 1 << 20
 
 // TODO(apenwarr): incremental json decode?
 //  That would let us avoid storing the whole byte array uselessly in RAM.
@@ -214,7 +216,7 @@ func ReadMsg(r io.Reader) ([]byte, error) {
 		return nil, err
 	}
 	n := binary.LittleEndian.Uint32(cb)
-	if n > 1024*1024 {
+	if n > MaxMessageSize {
 		return nil, fmt.Errorf("ipn.Read: message too large: %v bytes", n)
 	}
 	b := make([]byte, n)
@@ -229,8 +231,12 @@ func ReadMsg(r io.Reader) ([]byte, error) {
 //  That would save RAM, at the expense of having to encode once so that
 //  we can produce the initial byte count.
 func WriteMsg(w io.Writer, b []byte) error {
+	// TODO(bradfitz): this does two writes to w, which likely
+	// does two writes on the wire, two frame generations, etc. We
+	// should take a concrete buffered type, or use a sync.Pool to
+	// allocate a buf and do one write.
 	cb := make([]byte, 4)
-	if len(b) > MSG_MAX {
+	if len(b) > MaxMessageSize {
 		return fmt.Errorf("ipn.Write: message too large: %v bytes", len(b))
 	}
 	binary.LittleEndian.PutUint32(cb, uint32(len(b)))