webrtc: return an error when proxying stream with no tracks

internal/core/path_test.go

@@ -404,6 +404,37 @@ func TestPathRunOnRead(t *testing.T) {
 						Log:        test.NilLogger{},
 					}
 
+					writerDone := make(chan struct{})
+					defer func() { <-writerDone }()
+
+					writerTerminate := make(chan struct{})
+					defer close(writerTerminate)
+
+					go func() {
+						defer close(writerDone)
+						i := uint16(0)
+						for {
+							select {
+							case <-time.After(100 * time.Millisecond):
+							case <-writerTerminate:
+								return
+							}
+							err := source.WritePacketRTP(testMediaH264, &rtp.Packet{
+								Header: rtp.Header{
+									Version:        2,
+									Marker:         true,
+									PayloadType:    96,
+									SequenceNumber: 123 + i,
+									Timestamp:      45343,
+									SSRC:           563423,
+								},
+								Payload: []byte{5},
+							})
+							require.NoError(t, err)
+							i++
+						}
+					}()
+
 					_, err = c.Read(context.Background())
 					require.NoError(t, err)
 					defer checkClose(t, c.Close)

internal/protocols/webrtc/peer_connection.go

@@ -227,7 +227,7 @@ outer:
 // GatherIncomingTracks gathers incoming tracks.
 func (co *PeerConnection) GatherIncomingTracks(
 	ctx context.Context,
-	count int,
+	maxCount int,
 ) ([]*IncomingTrack, error) {
 	var tracks []*IncomingTrack
 
@@ -237,7 +237,7 @@ func (co *PeerConnection) GatherIncomingTracks(
 	for {
 		select {
 		case <-t.C:
-			if count == 0 {
+			if maxCount == 0 && len(tracks) != 0 {
 				return tracks, nil
 			}
 			return nil, fmt.Errorf("deadline exceeded while waiting tracks")
@@ -249,7 +249,7 @@ func (co *PeerConnection) GatherIncomingTracks(
 			}
 			tracks = append(tracks, track)
 
-			if len(tracks) == count || len(tracks) >= 2 {
+			if len(tracks) == maxCount || len(tracks) >= 2 {
 				return tracks, nil
 			}