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limit the exponential PTO backoff to 60s (#3595)

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cliffc-spirent 2022-11-15 13:42:35 -10:00 • committed by GitHub
parent f2d3cb8f43
commit b8447041bb
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2 changed files with 25 additions and 5 deletions
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18
internal/ackhandler/sent_packet_handler.go
View file

@ -23,6 +23,8 @@ const (
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
// The PTO duration uses exponential backoff, but is truncated to a maximum value, as allowed by RFC 8961, section 4.4.
maxPTODuration = 60 * time.Second
)
type packetNumberSpace struct {
@ -457,6 +459,14 @@ func (h *sentPacketHandler) getLossTimeAndSpace() (time.Time, protocol.Encryptio
return lossTime, encLevel
}
func (h *sentPacketHandler) getScaledPTO(includeMaxAckDelay bool) time.Duration {
pto := h.rttStats.PTO(includeMaxAckDelay) << h.ptoCount
if pto > maxPTODuration || pto <= 0 {
return maxPTODuration
}
return pto
}
// same logic as getLossTimeAndSpace, but for lastAckElicitingPacketTime instead of lossTime
func (h *sentPacketHandler) getPTOTimeAndSpace() (pto time.Time, encLevel protocol.EncryptionLevel, ok bool) {
// We only send application data probe packets once the handshake is confirmed,
@ -465,7 +475,7 @@ func (h *sentPacketHandler) getPTOTimeAndSpace() (pto time.Time, encLevel protoc
if h.peerCompletedAddressValidation {
return
}
t := time.Now().Add(h.rttStats.PTO(false) << h.ptoCount)
t := time.Now().Add(h.getScaledPTO(false))
if h.initialPackets != nil {
return t, protocol.EncryptionInitial, true
}
@ -475,18 +485,18 @@ func (h *sentPacketHandler) getPTOTimeAndSpace() (pto time.Time, encLevel protoc
if h.initialPackets != nil {
encLevel = protocol.EncryptionInitial
if t := h.initialPackets.lastAckElicitingPacketTime; !t.IsZero() {
pto = t.Add(h.rttStats.PTO(false) << h.ptoCount)
pto = t.Add(h.getScaledPTO(false))
}
}
if h.handshakePackets != nil && !h.handshakePackets.lastAckElicitingPacketTime.IsZero() {
t := h.handshakePackets.lastAckElicitingPacketTime.Add(h.rttStats.PTO(false) << h.ptoCount)
t := h.handshakePackets.lastAckElicitingPacketTime.Add(h.getScaledPTO(false))
if pto.IsZero() || (!t.IsZero() && t.Before(pto)) {
pto = t
encLevel = protocol.EncryptionHandshake
}
}
if h.handshakeConfirmed && !h.appDataPackets.lastAckElicitingPacketTime.IsZero() {
t := h.appDataPackets.lastAckElicitingPacketTime.Add(h.rttStats.PTO(true) << h.ptoCount)
t := h.appDataPackets.lastAckElicitingPacketTime.Add(h.getScaledPTO(true))
if pto.IsZero() || (!t.IsZero() && t.Before(pto)) {
pto = t
encLevel = protocol.Encryption1RTT

12
internal/ackhandler/sent_packet_handler_test.go
View file

@ -687,6 +687,14 @@ var _ = Describe("SentPacketHandler", func() {
handler.ptoCount = 2
handler.setLossDetectionTimer()
Expect(handler.GetLossDetectionTimeout().Sub(sendTime)).To(Equal(4 * timeout))
// truncated when the exponential gets too large
handler.ptoCount = 20
handler.setLossDetectionTimer()
Expect(handler.GetLossDetectionTimeout().Sub(sendTime)).To(Equal(maxPTODuration))
// protected from rollover
handler.ptoCount = 100
handler.setLossDetectionTimer()
Expect(handler.GetLossDetectionTimeout().Sub(sendTime)).To(Equal(maxPTODuration))
})
It("reset the PTO count when receiving an ACK", func() {
@ -1036,7 +1044,7 @@ var _ = Describe("SentPacketHandler", func() {
})
It("correctly sets the timer after the Initial packet number space has been dropped", func() {
handler.SentPacket(initialPacket(&Packet{PacketNumber: 1, SendTime: time.Now().Add(-42 * time.Second)}))
handler.SentPacket(initialPacket(&Packet{PacketNumber: 1, SendTime: time.Now().Add(-19 * time.Second)}))
_, err := handler.ReceivedAck(
&wire.AckFrame{AckRanges: []wire.AckRange{{Smallest: 1, Largest: 1}}},
protocol.EncryptionInitial,
@ -1048,6 +1056,8 @@ var _ = Describe("SentPacketHandler", func() {
pto := handler.rttStats.PTO(false)
Expect(pto).ToNot(BeZero())
// pto is approximately 19 * 3. Using a number > 19 above will
// run into the maxPTODuration limit
Expect(handler.GetLossDetectionTimeout()).To(BeTemporally("~", time.Now().Add(pto), 10*time.Millisecond))
})