Log unwrapped sequence numbers

Author: mengelbart

log_format_test.go

@@ -8,27 +8,40 @@ package bwe_test
 import (
 	"fmt"
 	"log/slog"
-	"time"
 
 	"github.com/pion/interceptor"
 	"github.com/pion/rtcp"
 	"github.com/pion/rtp"
 )
 
+const (
+	maxSequenceNumberPlusOne = int64(65536)
+	breakpoint               = 32768 // half of max uint16
+)
+
 type packetLogger struct {
 	logger    *slog.Logger
 	direction string
+	seq       *unwrapper
+}
+
+func newPacketLogger(logger *slog.Logger, direction string) *packetLogger {
+	return &packetLogger{
+		logger:    logger,
+		direction: direction,
+		seq:       &unwrapper{},
+	}
 }
 
 func (l *packetLogger) LogRTPPacket(header *rtp.Header, payload []byte, attributes interceptor.Attributes) {
-	ts := time.Now()
+	u := l.seq.Unwrap(header.SequenceNumber)
 	l.logger.Info(
 		"rtp",
 		"direction", l.direction,
-		"ts", ts,
 		"pt", header.PayloadType,
 		"ssrc", header.SSRC,
 		"sequence-number", header.SequenceNumber,
+		"unwrapped-sequence-number", u,
 		"rtp-timestamp", header.Timestamp,
 		"marker", header.Marker,
 		"payload-size", len(payload),
@@ -44,3 +57,41 @@ func (l *packetLogger) LogRTCPPackets(pkts []rtcp.Packet, attributes interceptor
 		)
 	}
 }
+
+// Unwrapper stores an unwrapped sequence number.
+type unwrapper struct {
+	init          bool
+	lastUnwrapped int64
+}
+
+func isNewer(value, previous uint16) bool {
+	if value-previous == breakpoint {
+		return value > previous
+	}
+
+	return value != previous && (value-previous) < breakpoint
+}
+
+// Unwrap unwraps the next sequencenumber.
+func (u *unwrapper) Unwrap(i uint16) int64 {
+	if !u.init {
+		u.init = true
+		u.lastUnwrapped = int64(i)
+
+		return u.lastUnwrapped
+	}
+
+	lastWrapped := uint16(u.lastUnwrapped) //nolint:gosec // G115
+	delta := int64(i - lastWrapped)
+	if isNewer(i, lastWrapped) {
+		if delta < 0 {
+			delta += maxSequenceNumberPlusOne
+		}
+	} else if delta > 0 && u.lastUnwrapped+delta-maxSequenceNumberPlusOne >= 0 {
+		delta -= maxSequenceNumberPlusOne
+	}
+
+	u.lastUnwrapped += delta
+
+	return u.lastUnwrapped
+}

peer_test.go

@@ -54,12 +54,12 @@ func registerDefaultCodecs() option {
 
 func registerPacketLogger(logger *slog.Logger) option {
 	return func(p *peer) error {
-		ipl := &packetLogger{logger: logger, direction: "in"}
+		ipl := newPacketLogger(logger, "in")
 		rd, err := packetdump.NewReceiverInterceptor(packetdump.PacketLog(ipl))
 		if err != nil {
 			return err
 		}
-		opl := &packetLogger{logger: logger, direction: "out"}
+		opl := newPacketLogger(logger, "out")
 		sd, err := packetdump.NewSenderInterceptor(packetdump.PacketLog(opl))
 		if err != nil {
 			return err