Skip padding packet for simulcast probe

Skip padding packet for simulcast probe
Fix rtx attributes panic for nil map

Author: cnderrauber

peerconnection.go

@@ -1577,7 +1577,7 @@ func (pc *PeerConnection) handleIncomingSSRC(rtpStream io.Reader, ssrc SSRC) err
 	}
 
 	var mid, rid, rsid string
-	payloadType, err := handleUnknownRTPPacket(b[:i], uint8(midExtensionID), uint8(streamIDExtensionID), uint8(repairStreamIDExtensionID), &mid, &rid, &rsid)
+	payloadType, paddingOnly, err := handleUnknownRTPPacket(b[:i], uint8(midExtensionID), uint8(streamIDExtensionID), uint8(repairStreamIDExtensionID), &mid, &rid, &rsid)
 	if err != nil {
 		return err
 	}
@@ -1595,12 +1595,17 @@ func (pc *PeerConnection) handleIncomingSSRC(rtpStream io.Reader, ssrc SSRC) err
 
 	for readCount := 0; readCount <= simulcastProbeCount; readCount++ {
 		if mid == "" || (rid == "" && rsid == "") {
+			// skip padding only packets for probing
+			if paddingOnly {
+				readCount--
+			}
+
 			i, _, err := interceptor.Read(b, nil)
 			if err != nil {
 				return err
 			}
 
-			if _, err = handleUnknownRTPPacket(b[:i], uint8(midExtensionID), uint8(streamIDExtensionID), uint8(repairStreamIDExtensionID), &mid, &rid, &rsid); err != nil {
+			if _, paddingOnly, err = handleUnknownRTPPacket(b[:i], uint8(midExtensionID), uint8(streamIDExtensionID), uint8(repairStreamIDExtensionID), &mid, &rid, &rsid); err != nil {
 				return err
 			}
 

peerconnection_media_test.go

@@ -1301,7 +1301,28 @@ func TestPeerConnection_Simulcast(t *testing.T) {
 
 		assert.NoError(t, signalPair(pcOffer, pcAnswer))
 
-		for sequenceNumber := uint16(0); !ridsFullfilled(); sequenceNumber++ {
+		// padding only packets should not affect simulcast probe
+		var sequenceNumber uint16
+		for sequenceNumber = 0; sequenceNumber < simulcastProbeCount+10; sequenceNumber++ {
+			time.Sleep(20 * time.Millisecond)
+
+			for _, track := range []*TrackLocalStaticRTP{vp8WriterA, vp8WriterB, vp8WriterC} {
+				pkt := &rtp.Packet{
+					Header: rtp.Header{
+						Version:        2,
+						SequenceNumber: sequenceNumber,
+						PayloadType:    96,
+						Padding:        true,
+					},
+					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 ssrc, rid := range rids {

rtptransceiver.go

@@ -266,12 +266,16 @@ func satisfyTypeAndDirection(remoteKind RTPCodecType, remoteDirection RTPTransce
 
 // handleUnknownRTPPacket consumes a single RTP Packet and returns information that is helpful
 // for demuxing and handling an unknown SSRC (usually for Simulcast)
-func handleUnknownRTPPacket(buf []byte, midExtensionID, streamIDExtensionID, repairStreamIDExtensionID uint8, mid, rid, rsid *string) (payloadType PayloadType, err error) {
+func handleUnknownRTPPacket(buf []byte, midExtensionID, streamIDExtensionID, repairStreamIDExtensionID uint8, mid, rid, rsid *string) (payloadType PayloadType, paddingOnly bool, err error) {
 	rp := &rtp.Packet{}
 	if err = rp.Unmarshal(buf); err != nil {
 		return
 	}
 
+	if rp.Padding && len(rp.Payload) == 0 {
+		paddingOnly = true
+	}
+
 	if !rp.Header.Extension {
 		return
 	}