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Merge pull request #3129 from lucas-clemente/limit-retry-rtt-measurement

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don't use a lower RTT than 5ms after receiving a Retry packet
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Marten Seemann 2021-04-02 19:30:06 +07:00 • committed by GitHub
commit 3138a45fde
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2 changed files with 19 additions and 1 deletions
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5
internal/ackhandler/sent_packet_handler.go
View file

@ -21,6 +21,8 @@ const (
packetThreshold = 3
// Before validating the client's address, the server won't send more than 3x bytes than it received.
amplificationFactor = 3
// We use Retry packets to derive an RTT estimate. Make sure we don't set the RTT to a super low value yet.
minRTTAfterRetry = 5 * time.Millisecond
)
type packetNumberSpace struct {
@ -792,8 +794,9 @@ func (h *sentPacketHandler) ResetForRetry() error {
// Only use the Retry to estimate the RTT if we didn't send any retransmission for the Initial.
// Otherwise, we don't know which Initial the Retry was sent in response to.
if h.ptoCount == 0 {
// Don't set the RTT to a value lower than 5ms here.
now := time.Now()
h.rttStats.UpdateRTT(now.Sub(firstPacketSendTime), 0, now)
h.rttStats.UpdateRTT(utils.MaxDuration(minRTTAfterRetry, now.Sub(firstPacketSendTime)), 0, now)
if h.logger.Debug() {
h.logger.Debugf("\tupdated RTT: %s (σ: %s)", h.rttStats.SmoothedRTT(), h.rttStats.MeanDeviation())
}

15
internal/ackhandler/sent_packet_handler_test.go
View file

@ -1233,6 +1233,21 @@ var _ = Describe("SentPacketHandler", func() {
Expect(handler.rttStats.SmoothedRTT()).To(BeNumerically("~", 500*time.Millisecond, 100*time.Millisecond))
})
It("uses a Retry for an RTT estimate, but doesn't set the RTT to a value lower than 5ms", func() {
handler.SentPacket(ackElicitingPacket(&Packet{
PacketNumber: 42,
EncryptionLevel: protocol.EncryptionInitial,
SendTime: time.Now().Add(-500 * time.Microsecond),
}))
handler.SentPacket(ackElicitingPacket(&Packet{
PacketNumber: 43,
EncryptionLevel: protocol.EncryptionInitial,
SendTime: time.Now().Add(-10 * time.Microsecond),
}))
Expect(handler.ResetForRetry()).To(Succeed())
Expect(handler.rttStats.SmoothedRTT()).To(Equal(minRTTAfterRetry))
})
It("doesn't use a Retry for an RTT estimate, if it was not retransmitted", func() {
handler.SentPacket(ackElicitingPacket(&Packet{
PacketNumber: 42,