ackhandler: track lost packets and detect spurious losses (#5355)

* ackhandler: implement a lost packet tracker

* logging: add ConnectionTracer.DetectedSpuriousLoss event

* ackhandler: detect spurious losses

* qlog: add support for logging spurious packet loss

* ackhandler: delete lost packets after detecting spurios loss

* guard against slice index underflow

internal/mocks/logging/connection_tracer.go

@@ -68,6 +68,9 @@ func NewMockConnectionTracer(ctrl *gomock.Controller) (*logging.ConnectionTracer
 		LostPacket: func(encLevel logging.EncryptionLevel, pn logging.PacketNumber, reason logging.PacketLossReason) {
 			t.LostPacket(encLevel, pn, reason)
 		},
+		DetectedSpuriousLoss: func(encLevel logging.EncryptionLevel, pn logging.PacketNumber, reordering uint64, dur time.Duration) {
+			t.DetectedSpuriousLoss(encLevel, pn, reordering, dur)
+		},
 		UpdatedMTU: func(mtu logging.ByteCount, done bool) {
 			t.UpdatedMTU(mtu, done)
 		},

internal/mocks/logging/internal/connection_tracer.go

@@ -258,6 +258,42 @@ func (c *MockConnectionTracerDebugCall) DoAndReturn(f func(string, string)) *Moc
 	return c
 }
 
+// DetectedSpuriousLoss mocks base method.
+func (m *MockConnectionTracer) DetectedSpuriousLoss(arg0 logging.EncryptionLevel, arg1 logging.PacketNumber, arg2 uint64, arg3 time.Duration) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "DetectedSpuriousLoss", arg0, arg1, arg2, arg3)
+}
+
+// DetectedSpuriousLoss indicates an expected call of DetectedSpuriousLoss.
+func (mr *MockConnectionTracerMockRecorder) DetectedSpuriousLoss(arg0, arg1, arg2, arg3 any) *MockConnectionTracerDetectedSpuriousLossCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DetectedSpuriousLoss", reflect.TypeOf((*MockConnectionTracer)(nil).DetectedSpuriousLoss), arg0, arg1, arg2, arg3)
+	return &MockConnectionTracerDetectedSpuriousLossCall{Call: call}
+}
+
+// MockConnectionTracerDetectedSpuriousLossCall wrap *gomock.Call
+type MockConnectionTracerDetectedSpuriousLossCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockConnectionTracerDetectedSpuriousLossCall) Return() *MockConnectionTracerDetectedSpuriousLossCall {
+	c.Call = c.Call.Return()
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockConnectionTracerDetectedSpuriousLossCall) Do(f func(logging.EncryptionLevel, logging.PacketNumber, uint64, time.Duration)) *MockConnectionTracerDetectedSpuriousLossCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockConnectionTracerDetectedSpuriousLossCall) DoAndReturn(f func(logging.EncryptionLevel, logging.PacketNumber, uint64, time.Duration)) *MockConnectionTracerDetectedSpuriousLossCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
+
 // DroppedEncryptionLevel mocks base method.
 func (m *MockConnectionTracer) DroppedEncryptionLevel(arg0 logging.EncryptionLevel) {
 	m.ctrl.T.Helper()

internal/mocks/logging/mockgen.go

@@ -38,6 +38,7 @@ type ConnectionTracer interface {
 	UpdatedMetrics(rttStats *logging.RTTStats, cwnd, bytesInFlight logging.ByteCount, packetsInFlight int)
 	AcknowledgedPacket(logging.EncryptionLevel, logging.PacketNumber)
 	LostPacket(logging.EncryptionLevel, logging.PacketNumber, logging.PacketLossReason)
+	DetectedSpuriousLoss(logging.EncryptionLevel, logging.PacketNumber, uint64, time.Duration)
 	UpdatedCongestionState(logging.CongestionState)
 	UpdatedPTOCount(value uint32)
 	UpdatedKeyFromTLS(logging.EncryptionLevel, logging.Perspective)