Log time inversion between incoming packets (#4415)

* Log time inversion between incoming packets

Log of timestamp inversion within a red packet did not show anything.
Log across packets. Not dropping till there is more evidence of the
cause.

* save

* comment

pkg/sfu/redprimaryreceiver.go

@@ -45,6 +45,9 @@ type RedPrimaryReceiver struct {
 
 	firstPktReceived bool
 	lastSeq          uint16
+	lastExtSeq       uint64
+	lastTS           uint32
+	lastExtTS        uint64
 
 	// bitset for upstream packet receive history [lastSeq-8, lastSeq-1], bit 1 represents packet received
 	pktHistory byte
@@ -107,10 +110,41 @@ func (r *RedPrimaryReceiver) ForwardRTP(pkt *buffer.ExtPacket, spatialLayer int3
 				"packetETS", pPkt.ExtTimestamp,
 				"pktHistory", r.pktHistory,
 				"redHeader", pkt.Packet.Payload[:10],
+				"payloadSize", len(pkt.Packet.Payload),
 			)
 			continue // drop the packet which causes the inversion
 		}
 
+		if r.lastTS != 0 {
+			if pPkt.ExtSequenceNumber > r.lastExtSeq && pPkt.ExtTimestamp < r.lastExtTS {
+				r.logger.Warnw(
+					"timestamp inversion", nil,
+					"numPackets", len(pkts),
+					"primaryIncomingSN", pkt.Packet.Header.SequenceNumber,
+					"primaryIncomingTS", pkt.Packet.Header.Timestamp,
+					"primaryExtractedSN", pkts[len(pkts)-1].SequenceNumber,
+					"primaryExtractedTS", pkts[len(pkts)-1].Timestamp,
+					"primaryESN", pkt.ExtSequenceNumber,
+					"primaryETS", pkt.ExtTimestamp,
+					"packetIndex", i,
+					"packetExtractedSN", pkts[i].SequenceNumber,
+					"packetESN", pPkt.ExtSequenceNumber,
+					"packetExtractedTS", pkts[i].Timestamp,
+					"packetETS", pPkt.ExtTimestamp,
+					"pktHistory", r.pktHistory,
+					"redHeader", pkt.Packet.Payload[:10],
+					"payloadSize", len(pkt.Packet.Payload),
+					"lastSeq", r.lastSeq,
+					"lastExtSeq", r.lastExtSeq,
+					"lastTS", r.lastTS,
+					"lastExtTS", r.lastExtTS,
+				)
+			}
+		}
+		r.lastTS = pPkt.Packet.Header.Timestamp
+		r.lastExtTS = pPkt.ExtTimestamp
+		r.lastExtSeq = pPkt.ExtSequenceNumber
+
 		// not modify the ExtPacket.RawPacket here for performance since it is not used by the DownTrack,
 		// otherwise it should be set to the correct value (marshal the primary rtp packet)
 		r.downTrackSpreader.Broadcast(func(dt TrackSender) {