Stream closing is now ordered

internal/multiplex/frame.go

@@ -3,8 +3,8 @@ package multiplex
 import ()
 
 type Frame struct {
-	StreamID        uint32
-	Seq             uint32
-	ClosingStreamID uint32
-	Payload         []byte
+	StreamID uint32
+	Seq      uint32
+	Closing  uint32
+	Payload  []byte
 }

internal/multiplex/frameSorter.go

@@ -68,6 +68,11 @@ func (s *Stream) recvNewFrame() {
 		}
 
 		if len(s.sh) == 0 && f.Seq == s.nextRecvSeq {
+			if f.Closing == 1 {
+				s.passiveClose()
+				return
+			}
+
 			s.sortedBufCh <- f.Payload
 
 			s.nextRecvSeq += 1
@@ -107,8 +112,13 @@ func (s *Stream) recvNewFrame() {
 
 		// Keep popping from the heap until empty or to the point that the wanted seq was not received
 		for len(s.sh) > 0 && s.sh[0].seq == s.nextRecvSeq {
+			frame := heap.Pop(&s.sh).(*frameNode).frame
 
-			payload := heap.Pop(&s.sh).(*frameNode).frame.Payload
+			if frame.Closing == 1 {
+				s.passiveClose()
+				return
+			}
+			payload := frame.Payload
 			s.sortedBufCh <- payload
 
 			s.nextRecvSeq += 1

internal/multiplex/session.go

@@ -28,6 +28,7 @@ type Session struct {
 	// This is supposed to read one TLS message, the same as GoQuiet's ReadTillDrain
 	obfsedReader func(net.Conn, []byte) (int, error)
 
+	// atomic
 	nextStreamID uint32
 
 	streamsM sync.RWMutex
@@ -38,10 +39,6 @@ type Session struct {
 
 	// For accepting new streams
 	acceptCh chan *Stream
-	// Once a stream.Close is called, it sends its streamID to this channel
-	// to be read by another stream to send the streamID to notify the remote
-	// that this stream is closed
-	closeQCh chan uint32
 
 	closingM sync.Mutex
 	die      chan struct{}
@@ -58,7 +55,6 @@ func MakeSession(id int, conn net.Conn, obfs func(*Frame) []byte, deobfs func([]
 		nextStreamID: 1,
 		streams:      make(map[uint32]*Stream),
 		acceptCh:     make(chan *Stream, acceptBacklog),
-		closeQCh:     make(chan uint32, closeBacklog),
 		die:          make(chan struct{}),
 	}
 	sesh.sb = makeSwitchboard(conn, sesh)

internal/multiplex/stream.go

@@ -3,6 +3,8 @@ package multiplex
 import (
 	"errors"
 	"log"
+	"math"
+	prand "math/rand"
 	"sync"
 	"sync/atomic"
 )
@@ -26,6 +28,7 @@ type Stream struct {
 	// sortedBufCh are order-sorted data ready to be read raw
 	sortedBufCh chan []byte
 
+	// atomic
 	nextSendSeq uint32
 
 	closingM sync.Mutex
@@ -81,18 +84,11 @@ func (stream *Stream) Write(in []byte) (n int, err error) {
 	default:
 	}
 
-	var closingID uint32
-
-	select {
-	case closingID = <-stream.session.closeQCh:
-	default:
-	}
-
 	f := &Frame{
-		StreamID:        stream.id,
-		Seq:             stream.nextSendSeq,
-		ClosingStreamID: closingID,
-		Payload:         in,
+		StreamID: stream.id,
+		Seq:      atomic.LoadUint32(&stream.nextSendSeq),
+		Closing:  0,
+		Payload:  in,
 	}
 
 	atomic.AddUint32(&stream.nextSendSeq, 1)
@@ -104,8 +100,24 @@ func (stream *Stream) Write(in []byte) (n int, err error) {
 
 }
 
+// only close locally. Used when the stream close is notified by the remote
+func (stream *Stream) passiveClose() error {
+
+	// Lock here because closing a closed channel causes panic
+	stream.closingM.Lock()
+	defer stream.closingM.Unlock()
+	if stream.closing {
+		return errRepeatStreamClosing
+	}
+	log.Printf("ID: %v passiveclosing\n", stream.id)
+	stream.closing = true
+	close(stream.die)
+	stream.session.delStream(stream.id)
+	return nil
+}
+
+// active close. Close locally and tell the remote that this stream is being closed
 func (stream *Stream) Close() error {
-	log.Printf("ID: %v closing\n", stream.id)
 
 	// Lock here because closing a closed channel causes panic
 	stream.closingM.Lock()
@@ -113,10 +125,25 @@ func (stream *Stream) Close() error {
 	if stream.closing {
 		return errRepeatStreamClosing
 	}
+	log.Printf("ID: %v closing\n", stream.id)
 	stream.closing = true
 	close(stream.die)
+
+	prand.Seed(int64(stream.id))
+	padLen := int(math.Floor(prand.Float64()*200 + 300))
+	log.Println(padLen)
+	pad := make([]byte, padLen)
+	prand.Read(pad)
+	f := &Frame{
+		StreamID: stream.id,
+		Seq:      atomic.LoadUint32(&stream.nextSendSeq),
+		Closing:  1,
+		Payload:  pad,
+	}
+	tlsRecord := stream.session.obfs(f)
+	stream.session.sb.dispatCh <- tlsRecord
+
 	stream.session.delStream(stream.id)
-	stream.session.closeQCh <- stream.id
 	return nil
 }
 
@@ -133,6 +160,5 @@ func (stream *Stream) closeNoDelMap() error {
 	}
 	stream.closing = true
 	close(stream.die)
-	stream.session.closeQCh <- stream.id
 	return nil
 }

internal/multiplex/switchboard.go

@@ -145,7 +145,6 @@ func (sb *switchboard) dispatch() {
 // it is responsible to act in response to the deobfsed header
 // i.e. should a new stream be added? which existing stream should be closed?
 func (sb *switchboard) deplex(ce *connEnclave) {
-	var highestStream uint32
 	buf := make([]byte, 20480)
 	for {
 		i, err := sb.session.obfsedReader(ce.remoteConn, buf)
@@ -156,22 +155,10 @@ func (sb *switchboard) deplex(ce *connEnclave) {
 			return
 		}
 		frame := sb.session.deobfs(buf[:i])
-		if closing := sb.session.getStream(frame.ClosingStreamID); closing != nil {
-			log.Printf("HeaderClosing: %v\n", frame.ClosingStreamID)
-			closing.Close()
-		}
-
 		var stream *Stream
-		// If we want to open a new stream, we need to make sure that the newStreamID is indeed new
-		// i.e. it is not a stream that existed before but has been closed
-		// we don't allow streamID reuse.
-		// So here we do a check that the new stream has a higher ID than the highest ID we have got
-		if stream = sb.session.getStream(frame.StreamID); highestStream < frame.StreamID && stream == nil {
+		if stream = sb.session.getStream(frame.StreamID); stream == nil {
 			stream = sb.session.addStream(frame.StreamID)
-			highestStream = frame.StreamID
-		}
-		if stream != nil {
-			stream.newFrameCh <- frame
 		}
+		stream.newFrameCh <- frame
 	}
 }

internal/util/obfs.go

@@ -25,11 +25,11 @@ func genXorKeys(SID []byte, data []byte) (i uint32, ii uint32, iii uint32) {
 func MakeObfs(key []byte) func(*mux.Frame) []byte {
 	obfs := func(f *mux.Frame) []byte {
 		obfsedHeader := make([]byte, 12)
-		// header: [StreamID 4 bytes][Seq 4 bytes][ClosingStreamID 4 bytes]
+		// header: [StreamID 4 bytes][Seq 4 bytes][Closing 4 bytes]
 		i, ii, iii := genXorKeys(key, f.Payload[0:18])
 		binary.BigEndian.PutUint32(obfsedHeader[0:4], f.StreamID^i)
 		binary.BigEndian.PutUint32(obfsedHeader[4:8], f.Seq^ii)
-		binary.BigEndian.PutUint32(obfsedHeader[8:12], f.ClosingStreamID^iii)
+		binary.BigEndian.PutUint32(obfsedHeader[8:12], f.Closing^iii)
 
 		// Composing final obfsed message
 		// We don't use util.AddRecordLayer here to avoid unnecessary malloc
@@ -52,14 +52,14 @@ func MakeDeobfs(key []byte) func([]byte) *mux.Frame {
 		i, ii, iii := genXorKeys(key, peeled[12:30])
 		streamID := binary.BigEndian.Uint32(peeled[0:4]) ^ i
 		seq := binary.BigEndian.Uint32(peeled[4:8]) ^ ii
-		closingStreamID := binary.BigEndian.Uint32(peeled[8:12]) ^ iii
+		closing := binary.BigEndian.Uint32(peeled[8:12]) ^ iii
 		payload := make([]byte, len(peeled)-12)
 		copy(payload, peeled[12:])
 		ret := &mux.Frame{
-			StreamID:        streamID,
-			Seq:             seq,
-			ClosingStreamID: closingStreamID,
-			Payload:         payload,
+			StreamID: streamID,
+			Seq:      seq,
+			Closing:  closing,
+			Payload:  payload,
 		}
 		return ret
 	}