add tracing for lost packets

internal/ackhandler/sent_packet_handler.go

@@ -76,6 +76,8 @@ type sentPacketHandler struct {
 	// The alarm timeout
 	alarm time.Time
 
+	traceCallback func(quictrace.Event)
+
 	logger utils.Logger
 }
 
@@ -83,6 +85,7 @@ type sentPacketHandler struct {
 func NewSentPacketHandler(
 	initialPacketNumber protocol.PacketNumber,
 	rttStats *congestion.RTTStats,
+	traceCallback func(quictrace.Event),
 	logger utils.Logger,
 ) SentPacketHandler {
 	congestion := congestion.NewCubicSender(
@@ -99,6 +102,7 @@ func NewSentPacketHandler(
 		oneRTTPackets:    newPacketNumberSpace(0),
 		rttStats:         rttStats,
 		congestion:       congestion,
+		traceCallback:    traceCallback,
 		logger:           logger,
 	}
 }
@@ -404,6 +408,17 @@ func (h *sentPacketHandler) detectLostPackets(
 			}
 		}
 		pnSpace.history.Remove(p.PacketNumber)
+		if h.traceCallback != nil {
+			h.traceCallback(quictrace.Event{
+				Time:            now,
+				EventType:       quictrace.PacketLost,
+				EncryptionLevel: p.EncryptionLevel,
+				PacketNumber:    p.PacketNumber,
+				PacketSize:      p.Length,
+				Frames:          p.Frames,
+				TransportState:  h.GetStats(),
+			})
+		}
 	}
 	return nil
 }

internal/ackhandler/sent_packet_handler_test.go

@@ -48,7 +48,7 @@ var _ = Describe("SentPacketHandler", func() {
 
 	BeforeEach(func() {
 		rttStats := &congestion.RTTStats{}
-		handler = NewSentPacketHandler(42, rttStats, utils.DefaultLogger).(*sentPacketHandler)
+		handler = NewSentPacketHandler(42, rttStats, nil, utils.DefaultLogger).(*sentPacketHandler)
 		streamFrame = wire.StreamFrame{
 			StreamID: 5,
 			Data:     []byte{0x13, 0x37},

session.go

@@ -162,6 +162,8 @@ type session struct {
 	// it is reset as soon as we receive a packet from the peer
 	keepAlivePingSent bool
 
+	traceCallback func(quictrace.Event)
+
 	logger utils.Logger
 }
 
@@ -194,7 +196,7 @@ var newSession = func(
 		version:               v,
 	}
 	s.preSetup()
-	s.sentPacketHandler = ackhandler.NewSentPacketHandler(0, s.rttStats, s.logger)
+	s.sentPacketHandler = ackhandler.NewSentPacketHandler(0, s.rttStats, s.traceCallback, s.logger)
 	s.streamsMap = newStreamsMap(
 		s,
 		s.newFlowController,
@@ -276,7 +278,7 @@ var newClientSession = func(
 		version:               v,
 	}
 	s.preSetup()
-	s.sentPacketHandler = ackhandler.NewSentPacketHandler(initialPacketNumber, s.rttStats, s.logger)
+	s.sentPacketHandler = ackhandler.NewSentPacketHandler(initialPacketNumber, s.rttStats, s.traceCallback, s.logger)
 	initialStream := newCryptoStream()
 	handshakeStream := newCryptoStream()
 	oneRTTStream := newPostHandshakeCryptoStream(s.framer)
@@ -339,6 +341,11 @@ func (s *session) preSetup() {
 		s.rttStats,
 		s.logger,
 	)
+	if s.config.QuicTracer != nil {
+		s.traceCallback = func(ev quictrace.Event) {
+			s.config.QuicTracer.Trace(s.origDestConnID, ev)
+		}
+	}
 }
 
 func (s *session) postSetup() error {
@@ -683,7 +690,7 @@ func (s *session) handleUnpackedPacket(packet *unpackedPacket, rcvTime time.Time
 		if ackhandler.IsFrameAckEliciting(frame) {
 			isAckEliciting = true
 		}
-		if s.config.QuicTracer != nil {
+		if s.traceCallback != nil {
 			frames = append(frames, frame)
 		}
 		if err := s.handleFrame(frame, packet.packetNumber, packet.encryptionLevel); err != nil {
@@ -691,8 +698,8 @@ func (s *session) handleUnpackedPacket(packet *unpackedPacket, rcvTime time.Time
 		}
 	}
 
-	if s.config.QuicTracer != nil {
-		s.config.QuicTracer.Trace(s.origDestConnID, quictrace.Event{
+	if s.traceCallback != nil {
+		s.traceCallback(quictrace.Event{
 			Time:            time.Now(),
 			EventType:       quictrace.PacketReceived,
 			TransportState:  s.sentPacketHandler.GetStats(),
@@ -1173,8 +1180,8 @@ func (s *session) sendPackedPacket(packet *packedPacket) error {
 	if s.firstAckElicitingPacketAfterIdleSentTime.IsZero() && packet.IsAckEliciting() {
 		s.firstAckElicitingPacketAfterIdleSentTime = time.Now()
 	}
-	if s.config.QuicTracer != nil {
-		s.config.QuicTracer.Trace(s.origDestConnID, quictrace.Event{
+	if s.traceCallback != nil {
+		s.traceCallback(quictrace.Event{
 			Time:            time.Now(),
 			EventType:       quictrace.PacketSent,
 			TransportState:  s.sentPacketHandler.GetStats(),