garbage collect skippedPackets slice in SentPacketHandler

ackhandler/sent_packet_handler.go

@@ -248,6 +248,8 @@ func (h *sentPacketHandler) ReceivedAck(ackFrame *frames.AckFrame, withPacketNum
 		}
 	}
 
+	h.garbageCollectSkippedPackets()
+
 	h.stopWaitingManager.ReceivedAck(ackFrame)
 
 	h.congestion.OnCongestionEvent(
@@ -345,3 +347,13 @@ func (h *sentPacketHandler) TimeOfFirstRTO() time.Time {
 	}
 	return h.lastSentPacketTime.Add(h.getRTO())
 }
+
+func (h *sentPacketHandler) garbageCollectSkippedPackets() {
+	deleteIndex := 0
+	for i, p := range h.skippedPackets {
+		if p <= h.LargestInOrderAcked {
+			deleteIndex = i + 1
+		}
+	}
+	h.skippedPackets = h.skippedPackets[deleteIndex:]
+}

ackhandler/sent_packet_handler_test.go

@@ -186,6 +186,29 @@ var _ = Describe("SentPacketHandler", func() {
 				Expect(handler.skippedPackets[0]).To(Equal(protocol.PacketNumber(10)))
 				Expect(handler.skippedPackets[protocol.MaxTrackedSkippedPackets-1]).To(Equal(protocol.PacketNumber(10 + 2*(protocol.MaxTrackedSkippedPackets-1))))
 			})
+
+			Context("garbage collection", func() {
+				It("keeps all packet numbers above the LargestInOrderAcked", func() {
+					handler.skippedPackets = []protocol.PacketNumber{2, 5, 8, 10}
+					handler.LargestInOrderAcked = 1
+					handler.garbageCollectSkippedPackets()
+					Expect(handler.skippedPackets).To(Equal([]protocol.PacketNumber{2, 5, 8, 10}))
+				})
+
+				It("doesn't keep packet numbers below the LargestInOrderAcked", func() {
+					handler.skippedPackets = []protocol.PacketNumber{1, 5, 8, 10}
+					handler.LargestInOrderAcked = 5
+					handler.garbageCollectSkippedPackets()
+					Expect(handler.skippedPackets).To(Equal([]protocol.PacketNumber{8, 10}))
+				})
+
+				It("deletes all packet numbers if LargestInOrderAcked is sufficiently high", func() {
+					handler.skippedPackets = []protocol.PacketNumber{1, 5, 10}
+					handler.LargestInOrderAcked = 15
+					handler.garbageCollectSkippedPackets()
+					Expect(handler.skippedPackets).To(BeEmpty())
+				})
+			})
 		})
 	})