From 7467e7ebff40e66ed9d2fb1aa5ab4efbd511332d Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Sun, 24 Apr 2016 20:28:37 +0700
Subject: [PATCH] OutgoingPacketAckHandler queues packets for retransmission

---
 ackhandler/outgoing_packet_ack_handler.go     | 13 +++++++--
 .../outgoing_packet_ack_handler_test.go       | 28 +++++++++++++++++++
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/ackhandler/outgoing_packet_ack_handler.go b/ackhandler/outgoing_packet_ack_handler.go
index 1f5698d6..bdbc9349 100644
--- a/ackhandler/outgoing_packet_ack_handler.go
+++ b/ackhandler/outgoing_packet_ack_handler.go
@@ -9,8 +9,9 @@ import (
 )
 
 var (
-	errEntropy   = errors.New("OutgoingPacketAckHandler: Wrong entropy")
-	errMapAccess = errors.New("OutgoingPacketAckHandler: Packet does not exist in PacketHistory")
+	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
 )
 
 type outgoingPacketAckHandler struct {
@@ -20,6 +21,7 @@ type outgoingPacketAckHandler struct {
 	LargestObserved                 protocol.PacketNumber
 	packetHistory                   map[protocol.PacketNumber]*Packet
 	packetHistoryMutex              sync.Mutex
+	retransmissionQueue             []*Packet // ToDo: use better data structure
 }
 
 // NewOutgoingPacketAckHandler creates a new outgoingPacketAckHandler
@@ -164,7 +166,12 @@ func (h *outgoingPacketAckHandler) ReceivedAck(ackFrame *frames.AckFrame) error
 					return errMapAccess
 				}
 				packet.MissingReports++
-				// ToDo: do something as when packet.MissionReports > threshold
+				// 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
+				}
 			}
 			// ToDo: delete packet from history, since it already has been ACKed
 		}
diff --git a/ackhandler/outgoing_packet_ack_handler_test.go b/ackhandler/outgoing_packet_ack_handler_test.go
index 3c55a02a..899cd92a 100644
--- a/ackhandler/outgoing_packet_ack_handler_test.go
+++ b/ackhandler/outgoing_packet_ack_handler_test.go
@@ -310,5 +310,33 @@ var _ = Describe("AckHandler", func() {
 				Expect(handler.packetHistory[4].MissingReports).To(Equal(uint8(1)))
 			})
 		})
+
+		Context("Retransmission handler", func() {
+			It("queues a packet for retransmission", func() {
+				retransmissionThreshold = 1
+				nackRange1 := frames.NackRange{FirstPacketNumber: 4, LastPacketNumber: 4}
+				nackRange2 := 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{nackRange2},
+				}
+				err := handler.ReceivedAck(&ack1)
+				Expect(err).ToNot(HaveOccurred())
+				entropy.Add(5, packets[4].EntropyBit)
+				ack2 := frames.AckFrame{
+					LargestObserved: 5,
+					Entropy:         byte(entropy),
+					NackRanges:      []frames.NackRange{nackRange1, nackRange2},
+				}
+				err = handler.ReceivedAck(&ack2)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(len(handler.retransmissionQueue)).To(Equal(1))
+				Expect(handler.retransmissionQueue[0].PacketNumber).To(Equal(protocol.PacketNumber(2)))
+			})
+		})
 	})
 })