implemenet OutgoingPacketAckHandler.DequeuePacketForRetransmission(), fix minor error

ackhandler/outgoing_packet_ack_handler.go

@@ -11,7 +11,7 @@ import (
 var (
 	errEntropy              = errors.New("OutgoingPacketAckHandler: Wrong entropy")
 	errMapAccess            = errors.New("OutgoingPacketAckHandler: Packet does not exist in PacketHistory")
-	retransmissionThreshold = uint8(1) // ToDo: use 3 as recommended in the RFC here
+	retransmissionThreshold = uint8(3)
 )
 
 type outgoingPacketAckHandler struct {
@@ -168,7 +168,6 @@ func (h *outgoingPacketAckHandler) ReceivedAck(ackFrame *frames.AckFrame) error
 				packet.MissingReports++
 				// send out the packet again when it has been NACK more than retransmissionThreshold times
 				if packet.MissingReports > retransmissionThreshold {
-					fmt.Printf("Should retransmit packet %d\n", packet.PacketNumber)
 					h.retransmissionQueue = append(h.retransmissionQueue, packet)
 					// ToDo: delete the packet from the history, as if it had been acked
 				}
@@ -184,5 +183,10 @@ func (h *outgoingPacketAckHandler) ReceivedAck(ackFrame *frames.AckFrame) error
 }
 
 func (h *outgoingPacketAckHandler) DequeuePacketForRetransmission() (packet *Packet) {
+	if len(h.retransmissionQueue) == 0 {
 		return nil
+	}
+	packet = h.retransmissionQueue[0]
+	h.retransmissionQueue = h.retransmissionQueue[1:]
+	return packet
 }

ackhandler/outgoing_packet_ack_handler_test.go

@@ -337,6 +337,31 @@ var _ = Describe("AckHandler", func() {
 				Expect(len(handler.retransmissionQueue)).To(Equal(1))
 				Expect(handler.retransmissionQueue[0].PacketNumber).To(Equal(protocol.PacketNumber(2)))
 			})
+
+			It("dequeues a packet for retransmission", func() {
+				retransmissionThreshold = 1
+				nackRange := frames.NackRange{FirstPacketNumber: 2, LastPacketNumber: 2}
+				entropy := EntropyAccumulator(0)
+				entropy.Add(1, packets[0].EntropyBit)
+				entropy.Add(3, packets[2].EntropyBit)
+				ack1 := frames.AckFrame{
+					LargestObserved: 3,
+					Entropy:         byte(entropy),
+					NackRanges:      []frames.NackRange{nackRange},
+				}
+				err := handler.ReceivedAck(&ack1)
+				Expect(err).ToNot(HaveOccurred())
+				entropy.Add(4, packets[3].EntropyBit)
+				ack2 := frames.AckFrame{
+					LargestObserved: 4,
+					Entropy:         byte(entropy),
+					NackRanges:      []frames.NackRange{nackRange},
+				}
+				err = handler.ReceivedAck(&ack2)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(handler.DequeuePacketForRetransmission()).ToNot(BeNil())
+				Expect(handler.DequeuePacketForRetransmission()).To(BeNil())
+			})
 		})
 	})
 })