Use sync.Once to close die ch

cmd/ck-server/ck-server.go

@@ -152,8 +152,9 @@ func dispatchConnection(conn net.Conn, sta *server.State) {
 		for {
 			newStream, err := sesh.AcceptStream()
 			if err != nil {
-				log.Printf("Failed to get new stream: %v", err)
+				log.Printf("Failed to get new stream: %v\n", err)
 				if err == mux.ErrBrokenSession {
+					log.Printf("Session closed: %x:%v\n", UID, sessionID)
 					user.DelSession(sessionID)
 					return
 				} else {
@@ -162,7 +163,7 @@ func dispatchConnection(conn net.Conn, sta *server.State) {
 			}
 			ssConn, err := net.Dial("tcp", sta.SS_LOCAL_HOST+":"+sta.SS_LOCAL_PORT)
 			if err != nil {
-				log.Printf("Failed to connect to ssserver: %v", err)
+				log.Printf("Failed to connect to ssserver: %v\n", err)
 				continue
 			}
 			go pipe(ssConn, newStream)

internal/multiplex/session.go

@@ -38,10 +38,8 @@ type Session struct {
 	// For accepting new streams
 	acceptCh chan *Stream
 
-	// TODO: use sync.Once for this
-	closingM sync.Mutex
 	die      chan struct{}
-	closing  bool
+	overdose sync.Once // fentanyl? beware of respiratory depression
 }
 
 // 1 conn is needed to make a session
@@ -123,13 +121,7 @@ func (sesh *Session) addStream(id uint32) *Stream {
 
 func (sesh *Session) Close() error {
 	// Because closing a closed channel causes panic
-	sesh.closingM.Lock()
+	sesh.overdose.Do(func() { close(sesh.die) })
-	if sesh.closing {
-		sesh.closingM.Unlock()
-		return errRepeatSessionClosing
-	}
-	sesh.closing = true
-	close(sesh.die)
 	sesh.streamsM.Lock()
 	for id, stream := range sesh.streams {
 		// If we call stream.Close() here, streamsM will result in a deadlock

internal/multiplex/stream.go

@@ -10,7 +10,6 @@ import (
 )
 
 var errBrokenStream = errors.New("broken stream")
-var errRepeatStreamClosing = errors.New("trying to close a closed stream")
 
 type Stream struct {
 	id uint32
@@ -31,11 +30,11 @@ type Stream struct {
 	// atomic
 	nextSendSeq uint32
 
-	closingM sync.RWMutex
+	writingM sync.RWMutex
+
 	// close(die) is used to notify different goroutines that this stream is closing
-	die chan struct{}
+	die        chan struct{}
-	// to prevent closing a closed channel
+	heliumMask sync.Once // my personal fav
-	closing bool
 }
 
 func makeStream(id uint32, sesh *Session) *Stream {
@@ -84,10 +83,10 @@ func (stream *Stream) Write(in []byte) (n int, err error) {
 	// The use of RWMutex is so that the stream will not actively close
 	// in the middle of the execution of Write. This may cause the closing frame
 	// to be sent before the data frame and cause loss of packet.
-	stream.closingM.RLock()
+	stream.writingM.RLock()
 	select {
 	case <-stream.die:
-		stream.closingM.RUnlock()
+		stream.writingM.RUnlock()
 		return 0, errBrokenStream
 	default:
 	}
@@ -101,43 +100,26 @@ func (stream *Stream) Write(in []byte) (n int, err error) {
 
 	tlsRecord := stream.session.obfs(f)
 	n, err = stream.session.sb.send(tlsRecord)
-	stream.closingM.RUnlock()
+	stream.writingM.RUnlock()
 
 	return
 
 }
 
-func (stream *Stream) shutdown() error {
-	// Lock here because closing a closed channel causes panic
-	stream.closingM.Lock()
-	if stream.closing {
-		stream.closingM.Unlock()
-		return errRepeatStreamClosing
-	}
-	stream.closing = true
-	close(stream.die)
-	stream.closingM.Unlock()
-	return nil
-}
-
 // only close locally. Used when the stream close is notified by the remote
 func (stream *Stream) passiveClose() error {
-	err := stream.shutdown()
+	stream.heliumMask.Do(func() { close(stream.die) })
-	if err != nil {
-		return err
-	}
 	stream.session.delStream(stream.id)
 	log.Printf("%v passive closing\n", stream.id)
+	// TODO: really need to return an error?
 	return nil
 }
 
 // active close. Close locally and tell the remote that this stream is being closed
 func (stream *Stream) Close() error {
 
-	err := stream.shutdown()
+	stream.writingM.Lock()
-	if err != nil {
+	stream.heliumMask.Do(func() { close(stream.die) })
-		return err
-	}
 
 	// Notify remote that this stream is closed
 	prand.Seed(int64(stream.id))
@@ -151,17 +133,20 @@ func (stream *Stream) Close() error {
 		Payload:  pad,
 	}
 	tlsRecord := stream.session.obfs(f)
-	// FIXME: despite sb.send being always called after Write(), the actual TCP sending
-	// may still be out of order
 	stream.session.sb.send(tlsRecord)
 
 	stream.session.delStream(stream.id)
 	log.Printf("%v actively closed\n", stream.id)
+	stream.writingM.Unlock()
 	return nil
 }
 
-// Same as Close() but no call to session.delStream.
+// Same as passiveClose() but no call to session.delStream.
 // This is called in session.Close() to avoid mutex deadlock
+// We don't notify the remote because session.Close() is always
+// called when the session is passively closed
 func (stream *Stream) closeNoDelMap() error {
-	return stream.shutdown()
+	stream.heliumMask.Do(func() { close(stream.die) })
+	// TODO: really need to return an error?
+	return nil
 }