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implement a sophisticated ack algorithm

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fixes #354
This commit is contained in:
Marten Seemann 2017-01-09 13:02:01 +07:00
parent 634d2dc6b7
commit edf6ee3dfc
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GPG key ID: 3603F40B121FCDEA
8 changed files with 370 additions and 256 deletions
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350
ackhandler/received_packet_handler_test.go
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@ -12,57 +12,63 @@ import (
var _ = Describe("receivedPacketHandler", func() {
var (
handler *receivedPacketHandler
handler *receivedPacketHandler
ackAlarmCallbackCalled bool
)
ackAlarmCallback := func(time.Time) {
ackAlarmCallbackCalled = true
}
BeforeEach(func() {
handler = NewReceivedPacketHandler().(*receivedPacketHandler)
ackAlarmCallbackCalled = false
handler = NewReceivedPacketHandler(ackAlarmCallback).(*receivedPacketHandler)
})
Context("accepting packets", func() {
It("handles a packet that arrives late", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(1))
err := handler.ReceivedPacket(protocol.PacketNumber(1), true)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(protocol.PacketNumber(3))
err = handler.ReceivedPacket(protocol.PacketNumber(3), true)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(protocol.PacketNumber(2))
err = handler.ReceivedPacket(protocol.PacketNumber(2), true)
Expect(err).ToNot(HaveOccurred())
})
It("rejects packets with packet number 0", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(0))
err := handler.ReceivedPacket(protocol.PacketNumber(0), true)
Expect(err).To(MatchError(errInvalidPacketNumber))
})
It("rejects a duplicate package", func() {
for i := 1; i < 5; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i))
err := handler.ReceivedPacket(protocol.PacketNumber(i), true)
Expect(err).ToNot(HaveOccurred())
}
err := handler.ReceivedPacket(4)
err := handler.ReceivedPacket(4, true)
Expect(err).To(MatchError(ErrDuplicatePacket))
})
It("ignores a packet with PacketNumber less than the LeastUnacked of a previously received StopWaiting", func() {
err := handler.ReceivedPacket(5)
err := handler.ReceivedPacket(5, true)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: 10})
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(9)
err = handler.ReceivedPacket(9, true)
Expect(err).To(MatchError(ErrPacketSmallerThanLastStopWaiting))
})
It("does not ignore a packet with PacketNumber equal to LeastUnacked of a previously received StopWaiting", func() {
err := handler.ReceivedPacket(5)
err := handler.ReceivedPacket(5, true)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: 10})
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(10)
err = handler.ReceivedPacket(10, true)
Expect(err).ToNot(HaveOccurred())
})
It("saves the time when each packet arrived", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(3))
err := handler.ReceivedPacket(protocol.PacketNumber(3), true)
Expect(err).ToNot(HaveOccurred())
Expect(handler.largestObservedReceivedTime).To(BeTemporally("~", time.Now(), 10*time.Millisecond))
})
@ -70,7 +76,7 @@ var _ = Describe("receivedPacketHandler", func() {
It("updates the largestObserved and the largestObservedReceivedTime", func() {
handler.largestObserved = 3
handler.largestObservedReceivedTime = time.Now().Add(-1 * time.Second)
err := handler.ReceivedPacket(5)
err := handler.ReceivedPacket(5, true)
Expect(err).ToNot(HaveOccurred())
Expect(handler.largestObserved).To(Equal(protocol.PacketNumber(5)))
Expect(handler.largestObservedReceivedTime).To(BeTemporally("~", time.Now(), 10*time.Millisecond))
@ -80,27 +86,27 @@ var _ = Describe("receivedPacketHandler", func() {
timestamp := time.Now().Add(-1 * time.Second)
handler.largestObserved = 5
handler.largestObservedReceivedTime = timestamp
err := handler.ReceivedPacket(4)
err := handler.ReceivedPacket(4, true)
Expect(err).ToNot(HaveOccurred())
Expect(handler.largestObserved).To(Equal(protocol.PacketNumber(5)))
Expect(handler.largestObservedReceivedTime).To(Equal(timestamp))
})
It("doesn't store more than MaxTrackedReceivedPackets packets", func() {
err := handler.ReceivedPacket(1)
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
for i := protocol.PacketNumber(3); i < 3+protocol.MaxTrackedReceivedPackets-1; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i))
err := handler.ReceivedPacket(protocol.PacketNumber(i), true)
Expect(err).ToNot(HaveOccurred())
}
err = handler.ReceivedPacket(protocol.PacketNumber(protocol.MaxTrackedReceivedPackets) + 10)
err = handler.ReceivedPacket(protocol.PacketNumber(protocol.MaxTrackedReceivedPackets)+10, true)
Expect(err).To(MatchError(errTooManyOutstandingReceivedPackets))
})
It("passes on errors from receivedPacketHistory", func() {
var err error
for i := protocol.PacketNumber(0); i < 5*protocol.MaxTrackedReceivedAckRanges; i++ {
err = handler.ReceivedPacket(2*i + 1)
err = handler.ReceivedPacket(2*i+1, true)
// this will eventually return an error
// details about when exactly the receivedPacketHistory errors are tested there
if err != nil {
@ -120,7 +126,7 @@ var _ = Describe("receivedPacketHandler", func() {
It("increase the ignorePacketsBelow number, even if all packets below the LeastUnacked were already acked", func() {
for i := 1; i < 20; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i))
err := handler.ReceivedPacket(protocol.PacketNumber(i), true)
Expect(err).ToNot(HaveOccurred())
}
err := handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(12)})
@ -138,133 +144,185 @@ var _ = Describe("receivedPacketHandler", func() {
})
})
Context("ACK package generation", func() {
It("generates a simple ACK frame", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(1))
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(protocol.PacketNumber(2))
Expect(err).ToNot(HaveOccurred())
ack, err := handler.GetAckFrame(true)
Expect(err).ToNot(HaveOccurred())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(2)))
Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(1)))
Expect(ack.AckRanges).To(BeEmpty())
})
It("generates an ACK frame with missing packets", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(1))
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(protocol.PacketNumber(4))
Expect(err).ToNot(HaveOccurred())
ack, err := handler.GetAckFrame(true)
Expect(err).ToNot(HaveOccurred())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(4)))
Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(1)))
Expect(ack.AckRanges).To(HaveLen(2))
Expect(ack.AckRanges[0]).To(Equal(frames.AckRange{FirstPacketNumber: 4, LastPacketNumber: 4}))
Expect(ack.AckRanges[1]).To(Equal(frames.AckRange{FirstPacketNumber: 1, LastPacketNumber: 1}))
})
It("does not generate an ACK if an ACK has already been sent for the largest Packet", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(1))
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(protocol.PacketNumber(2))
Expect(err).ToNot(HaveOccurred())
ack, err := handler.GetAckFrame(true)
Expect(err).ToNot(HaveOccurred())
Expect(ack).ToNot(BeNil())
ack, err = handler.GetAckFrame(true)
Expect(err).ToNot(HaveOccurred())
Expect(ack).To(BeNil())
})
It("does not dequeue an ACK frame if told so", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(2))
Expect(err).ToNot(HaveOccurred())
ack, err := handler.GetAckFrame(false)
Expect(err).ToNot(HaveOccurred())
Expect(ack).ToNot(BeNil())
ack, err = handler.GetAckFrame(false)
Expect(err).ToNot(HaveOccurred())
Expect(ack).ToNot(BeNil())
ack, err = handler.GetAckFrame(false)
Expect(err).ToNot(HaveOccurred())
Expect(ack).ToNot(BeNil())
})
It("returns a cached ACK frame if the ACK was not dequeued", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(2))
Expect(err).ToNot(HaveOccurred())
ack, err := handler.GetAckFrame(false)
Expect(err).ToNot(HaveOccurred())
Expect(ack).ToNot(BeNil())
ack2, err := handler.GetAckFrame(false)
Expect(err).ToNot(HaveOccurred())
Expect(ack2).ToNot(BeNil())
Expect(&ack).To(Equal(&ack2))
})
It("generates a new ACK (and deletes the cached one) when a new packet arrives", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(1))
Expect(err).ToNot(HaveOccurred())
ack, _ := handler.GetAckFrame(true)
Expect(ack).ToNot(BeNil())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(1)))
err = handler.ReceivedPacket(protocol.PacketNumber(3))
Expect(err).ToNot(HaveOccurred())
ack, _ = handler.GetAckFrame(true)
Expect(ack).ToNot(BeNil())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(3)))
})
It("generates a new ACK when an out-of-order packet arrives", func() {
err := handler.ReceivedPacket(protocol.PacketNumber(1))
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(protocol.PacketNumber(3))
Expect(err).ToNot(HaveOccurred())
ack, _ := handler.GetAckFrame(true)
Expect(ack).ToNot(BeNil())
Expect(ack.AckRanges).To(HaveLen(2))
err = handler.ReceivedPacket(protocol.PacketNumber(2))
Expect(err).ToNot(HaveOccurred())
ack, _ = handler.GetAckFrame(true)
Expect(ack).ToNot(BeNil())
Expect(ack.AckRanges).To(BeEmpty())
})
It("doesn't send old ACK ranges after receiving a StopWaiting", func() {
err := handler.ReceivedPacket(5)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(10)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(11)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(12)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(11)})
Expect(err).ToNot(HaveOccurred())
ack, err := handler.GetAckFrame(true)
Expect(err).ToNot(HaveOccurred())
Expect(ack).ToNot(BeNil())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(12)))
Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(11)))
Expect(ack.HasMissingRanges()).To(BeFalse())
})
It("deletes packets from the packetHistory after receiving a StopWaiting, after continuously received packets", func() {
for i := 1; i <= 12; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i))
Expect(err).ToNot(HaveOccurred())
Context("ACKs", func() {
Context("queueing ACKs", func() {
receiveAndAck10Packets := func() {
for i := 1; i <= 10; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i), true)
Expect(err).ToNot(HaveOccurred())
}
Expect(handler.GetAckFrame()).ToNot(BeNil())
Expect(handler.ackQueued).To(BeFalse())
ackAlarmCallbackCalled = false
}
err := handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(6)})
Expect(err).ToNot(HaveOccurred())
// check that the packets were deleted from the receivedPacketHistory by checking the values in an ACK frame
ack, err := handler.GetAckFrame(true)
Expect(err).ToNot(HaveOccurred())
Expect(ack).ToNot(BeNil())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(12)))
Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(6)))
Expect(ack.HasMissingRanges()).To(BeFalse())
It("always queues an ACK for the first packet", func() {
err := handler.ReceivedPacket(1, false)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeTrue())
Expect(ackAlarmCallbackCalled).To(BeFalse())
})
It("only queues one ACK for many non-retransmittable packets", func() {
receiveAndAck10Packets()
for i := 11; i < 10+protocol.MaxPacketsReceivedBeforeAckSend; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i), false)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeFalse())
}
err := handler.ReceivedPacket(10+protocol.MaxPacketsReceivedBeforeAckSend, false)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeTrue())
Expect(ackAlarmCallbackCalled).To(BeFalse())
})
It("queues an ACK for every second retransmittable packet, if they are arriving fast", func() {
receiveAndAck10Packets()
err := handler.ReceivedPacket(11, true)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeFalse())
Expect(ackAlarmCallbackCalled).To(BeTrue())
ackAlarmCallbackCalled = false
err = handler.ReceivedPacket(12, true)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeTrue())
Expect(ackAlarmCallbackCalled).To(BeFalse())
})
It("only sets the timer when receiving a retransmittable packets", func() {
receiveAndAck10Packets()
err := handler.ReceivedPacket(11, false)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeFalse())
Expect(handler.ackAlarm).To(BeZero())
err = handler.ReceivedPacket(12, true)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeFalse())
Expect(handler.ackAlarm).ToNot(BeZero())
Expect(ackAlarmCallbackCalled).To(BeTrue())
})
It("queues an ACK if it was reported missing before", func() {
receiveAndAck10Packets()
err := handler.ReceivedPacket(11, true)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(13, true)
Expect(err).ToNot(HaveOccurred())
ack := handler.GetAckFrame() // ACK: 1 and 3, missing: 2
Expect(ack).ToNot(BeNil())
Expect(ack.HasMissingRanges()).To(BeTrue())
Expect(handler.ackQueued).To(BeFalse())
err = handler.ReceivedPacket(12, false)
Expect(err).ToNot(HaveOccurred())
Expect(handler.ackQueued).To(BeTrue())
})
It("queues an ACK if it creates a new missing range", func() {
receiveAndAck10Packets()
for i := 11; i < 16; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i), true)
Expect(err).ToNot(HaveOccurred())
}
Expect(handler.GetAckFrame()).ToNot(BeNil())
handler.ReceivedPacket(20, true) // we now know that packets 16 to 19 are missing
Expect(handler.ackQueued).To(BeTrue())
})
})
Context("ACK generation", func() {
BeforeEach(func() {
handler.ackQueued = true
})
It("generates a simple ACK frame", func() {
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(2, true)
Expect(err).ToNot(HaveOccurred())
ack := handler.GetAckFrame()
Expect(ack).ToNot(BeNil())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(2)))
Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(1)))
Expect(ack.AckRanges).To(BeEmpty())
})
It("saves the last sent ACK", func() {
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
ack := handler.GetAckFrame()
Expect(ack).ToNot(BeNil())
Expect(handler.lastAck).To(Equal(ack))
err = handler.ReceivedPacket(2, true)
Expect(err).ToNot(HaveOccurred())
handler.ackQueued = true
ack = handler.GetAckFrame()
Expect(ack).ToNot(BeNil())
Expect(handler.lastAck).To(Equal(ack))
})
It("generates an ACK frame with missing packets", func() {
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
err = handler.ReceivedPacket(4, true)
Expect(err).ToNot(HaveOccurred())
ack := handler.GetAckFrame()
Expect(ack).ToNot(BeNil())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(4)))
Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(1)))
Expect(ack.AckRanges).To(HaveLen(2))
Expect(ack.AckRanges[0]).To(Equal(frames.AckRange{FirstPacketNumber: 4, LastPacketNumber: 4}))
Expect(ack.AckRanges[1]).To(Equal(frames.AckRange{FirstPacketNumber: 1, LastPacketNumber: 1}))
})
It("deletes packets from the packetHistory after receiving a StopWaiting, after continuously received packets", func() {
for i := 1; i <= 12; i++ {
err := handler.ReceivedPacket(protocol.PacketNumber(i), true)
Expect(err).ToNot(HaveOccurred())
}
err := handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(6)})
Expect(err).ToNot(HaveOccurred())
// check that the packets were deleted from the receivedPacketHistory by checking the values in an ACK frame
ack := handler.GetAckFrame()
Expect(ack).ToNot(BeNil())
Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(12)))
Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(6)))
Expect(ack.HasMissingRanges()).To(BeFalse())
})
It("resets all counters needed for the ACK queueing decision when sending an ACK", func() {
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
handler.ackAlarm = time.Now().Add(-time.Minute)
Expect(handler.GetAckFrame()).ToNot(BeNil())
Expect(handler.packetsReceivedSinceLastAck).To(BeZero())
Expect(handler.ackAlarm).To(BeZero())
Expect(handler.retransmittablePacketsReceivedSinceLastAck).To(BeZero())
Expect(handler.ackQueued).To(BeFalse())
})
It("doesn't generate an ACK when none is queued and the timer is not set", func() {
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
handler.ackQueued = false
handler.ackAlarm = time.Time{}
Expect(handler.GetAckFrame()).To(BeNil())
})
It("doesn't generate an ACK when none is queued and the timer has not yet expired", func() {
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
handler.ackQueued = false
handler.ackAlarm = time.Now().Add(time.Minute)
Expect(handler.GetAckFrame()).To(BeNil())
})
It("generates an ACK when the timer has expired", func() {
err := handler.ReceivedPacket(1, true)
Expect(err).ToNot(HaveOccurred())
handler.ackQueued = false
handler.ackAlarm = time.Now().Add(-time.Minute)
Expect(handler.GetAckFrame()).ToNot(BeNil())
})
})
})
})