Update RtxSSRC for simulcast track remote

Fix #2751, updates remote track's rtx ssrc for
simulcast track doesn't contain rtx ssrc in sdp
since readRTX relies on rtx ssrc to determine if
it has a rtx stream.

peerconnection_media_test.go

@@ -13,6 +13,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"regexp"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -26,6 +27,7 @@ import (
 	"github.com/pion/sdp/v3"
 	"github.com/pion/transport/v3/test"
 	"github.com/pion/transport/v3/vnet"
+	"github.com/pion/webrtc/v4/internal/util"
 	"github.com/pion/webrtc/v4/pkg/media"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -1388,6 +1390,222 @@ func TestPeerConnection_Simulcast(t *testing.T) {
 	})
 }
 
+type simulcastTestTrackLocal struct {
+	*TrackLocalStaticRTP
+}
+
+// don't use ssrc&payload in bindings to let the test write different stream packets.
+func (s *simulcastTestTrackLocal) WriteRTP(pkt *rtp.Packet) error {
+	packet := getPacketAllocationFromPool()
+
+	defer resetPacketPoolAllocation(packet)
+
+	*packet = *pkt
+
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	writeErrs := []error{}
+
+	for _, b := range s.bindings {
+		if _, err := b.writeStream.WriteRTP(&packet.Header, packet.Payload); err != nil {
+			writeErrs = append(writeErrs, err)
+		}
+	}
+
+	return util.FlattenErrs(writeErrs)
+}
+
+func TestPeerConnection_Simulcast_RTX(t *testing.T) {
+	lim := test.TimeOut(time.Second * 30)
+	defer lim.Stop()
+
+	report := test.CheckRoutines(t)
+	defer report()
+
+	rids := []string{"a", "b"}
+	pcOffer, pcAnswer, err := newPair()
+	assert.NoError(t, err)
+
+	vp8WriterAStatic, err := NewTrackLocalStaticRTP(RTPCodecCapability{MimeType: MimeTypeVP8}, "video", "pion2", WithRTPStreamID(rids[0]))
+	assert.NoError(t, err)
+
+	vp8WriterBStatic, err := NewTrackLocalStaticRTP(RTPCodecCapability{MimeType: MimeTypeVP8}, "video", "pion2", WithRTPStreamID(rids[1]))
+	assert.NoError(t, err)
+
+	vp8WriterA, vp8WriterB := &simulcastTestTrackLocal{vp8WriterAStatic}, &simulcastTestTrackLocal{vp8WriterBStatic}
+
+	sender, err := pcOffer.AddTrack(vp8WriterA)
+	assert.NoError(t, err)
+	assert.NotNil(t, sender)
+
+	assert.NoError(t, sender.AddEncoding(vp8WriterB))
+
+	var ridMapLock sync.RWMutex
+	ridMap := map[string]int{}
+
+	assertRidCorrect := func(t *testing.T) {
+		ridMapLock.Lock()
+		defer ridMapLock.Unlock()
+
+		for _, rid := range rids {
+			assert.Equal(t, ridMap[rid], 1)
+		}
+		assert.Equal(t, len(ridMap), 2)
+	}
+
+	ridsFullfilled := func() bool {
+		ridMapLock.Lock()
+		defer ridMapLock.Unlock()
+
+		ridCount := len(ridMap)
+		return ridCount == 2
+	}
+
+	var rtxPacketRead atomic.Int32
+	var wg sync.WaitGroup
+	wg.Add(2)
+
+	pcAnswer.OnTrack(func(trackRemote *TrackRemote, _ *RTPReceiver) {
+		ridMapLock.Lock()
+		ridMap[trackRemote.RID()] = ridMap[trackRemote.RID()] + 1
+		ridMapLock.Unlock()
+
+		defer wg.Done()
+
+		for {
+			_, attr, rerr := trackRemote.ReadRTP()
+			if rerr != nil {
+				break
+			}
+			if pt, ok := attr.Get(AttributeRtxPayloadType).(byte); ok {
+				if pt == 97 {
+					rtxPacketRead.Add(1)
+				}
+			}
+		}
+	})
+
+	parameters := sender.GetParameters()
+	assert.Equal(t, "a", parameters.Encodings[0].RID)
+	assert.Equal(t, "b", parameters.Encodings[1].RID)
+
+	var midID, ridID, rsid uint8
+	for _, extension := range parameters.HeaderExtensions {
+		switch extension.URI {
+		case sdp.SDESMidURI:
+			midID = uint8(extension.ID)
+		case sdp.SDESRTPStreamIDURI:
+			ridID = uint8(extension.ID)
+		case sdesRepairRTPStreamIDURI:
+			rsid = uint8(extension.ID)
+		}
+	}
+	assert.NotZero(t, midID)
+	assert.NotZero(t, ridID)
+	assert.NotZero(t, rsid)
+
+	err = signalPairWithModification(pcOffer, pcAnswer, func(sdp string) string {
+		// Original chrome sdp contains no ssrc info https://pastebin.com/raw/JTjX6zg6
+		re := regexp.MustCompile("(?m)[\r\n]+^.*a=ssrc.*$")
+		res := re.ReplaceAllString(sdp, "")
+		return res
+	})
+	assert.NoError(t, err)
+
+	// padding only packets should not affect simulcast probe
+	var sequenceNumber uint16
+	for sequenceNumber = 0; sequenceNumber < simulcastProbeCount+10; sequenceNumber++ {
+		time.Sleep(20 * time.Millisecond)
+
+		for i, track := range []*simulcastTestTrackLocal{vp8WriterA, vp8WriterB} {
+			pkt := &rtp.Packet{
+				Header: rtp.Header{
+					Version:        2,
+					SequenceNumber: sequenceNumber,
+					PayloadType:    96,
+					Padding:        true,
+					SSRC:           uint32(i),
+				},
+				Payload: []byte{0x00, 0x02},
+			}
+
+			assert.NoError(t, track.WriteRTP(pkt))
+		}
+	}
+	assert.False(t, ridsFullfilled(), "Simulcast probe should not be fulfilled by padding only packets")
+
+	for ; !ridsFullfilled(); sequenceNumber++ {
+		time.Sleep(20 * time.Millisecond)
+
+		for i, track := range []*simulcastTestTrackLocal{vp8WriterA, vp8WriterB} {
+			pkt := &rtp.Packet{
+				Header: rtp.Header{
+					Version:        2,
+					SequenceNumber: sequenceNumber,
+					PayloadType:    96,
+					SSRC:           uint32(i),
+				},
+				Payload: []byte{0x00},
+			}
+			assert.NoError(t, pkt.Header.SetExtension(midID, []byte("0")))
+			assert.NoError(t, pkt.Header.SetExtension(ridID, []byte(track.RID())))
+
+			assert.NoError(t, track.WriteRTP(pkt))
+		}
+	}
+
+	assertRidCorrect(t)
+
+	for i := 0; i < simulcastProbeCount+10; i++ {
+		sequenceNumber++
+		time.Sleep(10 * time.Millisecond)
+
+		for j, track := range []*simulcastTestTrackLocal{vp8WriterA, vp8WriterB} {
+			pkt := &rtp.Packet{
+				Header: rtp.Header{
+					Version:        2,
+					SequenceNumber: sequenceNumber,
+					PayloadType:    97,
+					SSRC:           uint32(100 + j),
+				},
+				Payload: []byte{0x00, 0x00, 0x00, 0x00, 0x00},
+			}
+			assert.NoError(t, pkt.Header.SetExtension(midID, []byte("0")))
+			assert.NoError(t, pkt.Header.SetExtension(ridID, []byte(track.RID())))
+			assert.NoError(t, pkt.Header.SetExtension(rsid, []byte(track.RID())))
+
+			assert.NoError(t, track.WriteRTP(pkt))
+		}
+	}
+
+	for ; rtxPacketRead.Load() == 0; sequenceNumber++ {
+		time.Sleep(20 * time.Millisecond)
+
+		for i, track := range []*simulcastTestTrackLocal{vp8WriterA, vp8WriterB} {
+			pkt := &rtp.Packet{
+				Header: rtp.Header{
+					Version:        2,
+					SequenceNumber: sequenceNumber,
+					PayloadType:    96,
+					SSRC:           uint32(i),
+				},
+				Payload: []byte{0x00},
+			}
+			assert.NoError(t, pkt.Header.SetExtension(midID, []byte("0")))
+			assert.NoError(t, pkt.Header.SetExtension(ridID, []byte(track.RID())))
+
+			assert.NoError(t, track.WriteRTP(pkt))
+		}
+	}
+
+	closePairNow(t, pcOffer, pcAnswer)
+
+	wg.Wait()
+
+	assert.Greater(t, rtxPacketRead.Load(), int32(0), "no rtx packet read")
+}
+
 // Everytime we receieve a new SSRC we probe it and try to determine the proper way to handle it.
 // In most cases a Track explicitly declares a SSRC and a OnTrack is fired. In two cases we don't
 // know the SSRC ahead of time

rtpreceiver.go

@@ -418,6 +418,10 @@ func (r *RTPReceiver) receiveForRtx(ssrc SSRC, rsid string, streamInfo *intercep
 		for i := range r.tracks {
 			if r.tracks[i].track.RID() == rsid {
 				track = &r.tracks[i]
+				if track.track.RtxSSRC() == 0 {
+					track.track.setRtxSSRC(SSRC(streamInfo.SSRC))
+				}
+				break
 			}
 		}
 	}

track_remote.go

@@ -224,3 +224,9 @@ func (t *TrackRemote) HasRTX() bool {
 	defer t.mu.RUnlock()
 	return t.rtxSsrc != 0
 }
+
+func (t *TrackRemote) setRtxSSRC(ssrc SSRC) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	t.rtxSsrc = ssrc
+}