Limit the number of reconfig reset requests enqueued

association.go

@@ -110,6 +110,8 @@ const (
 	// irrespective of the receive buffer size
 	// see Association.getMaxTSNOffset
 	maxTSNOffset = 40000
+	// maxReconfigRequests is the maximum number of reconfig requests we will keep outstanding
+	maxReconfigRequests = 1000
 )
 
 func getAssociationStateString(a uint32) string {
@@ -2138,15 +2140,39 @@ func (a *Association) handleReconfigParam(raw param) (*packet, error) {
 	switch p := raw.(type) {
 	case *paramOutgoingResetRequest:
 		a.log.Tracef("[%s] handleReconfigParam (OutgoingResetRequest)", a.name)
+		if a.peerLastTSN < p.senderLastTSN && len(a.reconfigRequests) >= maxReconfigRequests {
+			// We have too many reconfig requests outstanding. Drop the request and let
+			// the peer retransmit. A well behaved peer should only have 1 outstanding
+			// reconfig request.
+			//
+			// RFC 6525: https://www.rfc-editor.org/rfc/rfc6525.html#section-5.1.1
+			//    At any given time, there MUST NOT be more than one request in flight.
+			//    So, if the Re-configuration Timer is running and the RE-CONFIG chunk
+			//    contains at least one request parameter, the chunk MUST be buffered.
+			// chrome: https://chromium.googlesource.com/external/webrtc/+/refs/heads/main/net/dcsctp/socket/stream_reset_handler.cc#271
+			return nil, fmt.Errorf("too many outstanding reconfig requests: %d", len(a.reconfigRequests))
+		}
 		a.reconfigRequests[p.reconfigRequestSequenceNumber] = p
 		resp := a.resetStreamsIfAny(p)
 		if resp != nil {
 			return resp, nil
 		}
 		return nil, nil //nolint:nilnil
-
 	case *paramReconfigResponse:
 		a.log.Tracef("[%s] handleReconfigParam (ReconfigResponse)", a.name)
+		if p.result == reconfigResultInProgress {
+			// RFC 6525: https://www.rfc-editor.org/rfc/rfc6525.html#section-5.2.7
+			//
+			//   If the Result field indicates "In progress", the timer for the
+			//   Re-configuration Request Sequence Number is started again.  If
+			//   the timer runs out, the RE-CONFIG chunk MUST be retransmitted
+			//   but the corresponding error counters MUST NOT be incremented.
+			if len(a.reconfigs) == 0 {
+				a.tReconfig.stop()
+				a.tReconfig.start(a.rtoMgr.getRTO())
+			}
+			return nil, nil
+		}
 		delete(a.reconfigs, p.reconfigResponseSequenceNumber)
 		if len(a.reconfigs) == 0 {
 			a.tReconfig.stop()

association_test.go

@@ -3393,3 +3393,78 @@ func TestDataChunkBundlingIntoPacket(t *testing.T) {
 		}
 	}
 }
+
+func TestAssociation_ReconfigRequestsLimited(t *testing.T) {
+	checkGoroutineLeaks(t)
+
+	lim := test.TimeOut(time.Second * 10)
+	defer lim.Stop()
+
+	a1chan, a2chan := make(chan *Association), make(chan *Association)
+
+	udp1, udp2 := createUDPConnPair()
+
+	go func() {
+		a1, err := Client(Config{
+			NetConn:       udp1,
+			LoggerFactory: logging.NewDefaultLoggerFactory(),
+		})
+		assert.NoError(t, err)
+		a1chan <- a1
+	}()
+
+	go func() {
+		a2, err := Server(Config{
+			NetConn:       udp2,
+			LoggerFactory: logging.NewDefaultLoggerFactory(),
+		})
+		assert.NoError(t, err)
+		a2chan <- a2
+	}()
+
+	a1, a2 := <-a1chan, <-a2chan
+	defer a1.Close()
+	defer a2.Close()
+
+	writeStream, err := a1.OpenStream(1, PayloadTypeWebRTCString)
+	require.NoError(t, err)
+
+	readStream, err := a2.OpenStream(1, PayloadTypeWebRTCString)
+	require.NoError(t, err)
+
+	// exchange some data
+	testData := []byte("test")
+	_, err = writeStream.Write(testData)
+	require.NoError(t, err)
+
+	buf := make([]byte, len(testData))
+	_, err = readStream.Read(buf)
+	assert.NoError(t, err)
+	assert.Equal(t, testData, buf)
+
+	a1.lock.RLock()
+	tsn := a1.myNextTSN
+	a1.lock.RUnlock()
+	for i := 0; i < maxReconfigRequests+100; i++ {
+		c := &chunkReconfig{
+			paramA: &paramOutgoingResetRequest{
+				reconfigRequestSequenceNumber: 10 + uint32(i),
+				senderLastTSN:                 tsn + 10, // has to be enqueued
+				streamIdentifiers:             []uint16{uint16(i)},
+			},
+		}
+		p := a1.createPacket([]chunk{c})
+		buf, err := p.marshal(true)
+		require.NoError(t, err)
+		_, err = a1.netConn.Write(buf)
+		require.NoError(t, err)
+		if i%100 == 0 {
+			time.Sleep(100 * time.Millisecond)
+		}
+	}
+	// Let a2 process the requests
+	time.Sleep(2 * time.Second)
+	a2.lock.RLock()
+	require.LessOrEqual(t, len(a2.reconfigRequests), maxReconfigRequests)
+	a2.lock.RUnlock()
+}