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implement loss detection for handshake packets

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This commit is contained in:
Marten Seemann 2017-09-30 22:44:26 +07:00
parent e20fdf43ef
commit daa8d08fba
6 changed files with 99 additions and 7 deletions
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47
ackhandler/sent_packet_handler.go
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@ -16,8 +16,13 @@ const (
// Maximum reordering in time space before time based loss detection considers a packet lost.
// In fraction of an RTT.
timeReorderingFraction = 1.0 / 8
// The default RTT used before an RTT sample is taken.
// Note: This constant is also defined in the congestion package.
defaultInitialRTT = 100 * time.Millisecond
// defaultRTOTimeout is the RTO time on new connections
defaultRTOTimeout = 500 * time.Millisecond
// Minimum time in the future a tail loss probe alarm may be set for.
minTPLTimeout = 10 * time.Millisecond
// Minimum time in the future an RTO alarm may be set for.
minRTOTimeout = 200 * time.Millisecond
// maxRTOTimeout is the maximum RTO time
@ -56,6 +61,10 @@ type sentPacketHandler struct {
congestion congestion.SendAlgorithm
rttStats *congestion.RTTStats
handshakeComplete bool
// The number of times the handshake packets have been retransmitted without receiving an ack.
handshakeCount uint32
// The number of times an RTO has been sent without receiving an ack.
rtoCount uint32
@ -95,6 +104,10 @@ func (h *sentPacketHandler) ShouldSendRetransmittablePacket() bool {
return h.numNonRetransmittablePackets >= protocol.MaxNonRetransmittablePackets
}
func (h *sentPacketHandler) SetHandshakeComplete() {
h.handshakeComplete = true
}
func (h *sentPacketHandler) SentPacket(packet *Packet) error {
if packet.PacketNumber <= h.lastSentPacketNumber {
return errPacketNumberNotIncreasing
@ -247,9 +260,10 @@ func (h *sentPacketHandler) updateLossDetectionAlarm() {
return
}
// TODO(#496): Handle handshake packets separately
// TODO(#497): TLP
if !h.lossTime.IsZero() {
if !h.handshakeComplete {
h.alarm = time.Now().Add(h.computeHandshakeTimeout())
} else if !h.lossTime.IsZero() {
// Early retransmit timer or time loss detection.
h.alarm = h.lossTime
} else {
@ -291,9 +305,10 @@ func (h *sentPacketHandler) detectLostPackets() {
}
func (h *sentPacketHandler) OnAlarm() {
// TODO(#496): Handle handshake packets separately
// TODO(#497): TLP
if !h.lossTime.IsZero() {
if !h.handshakeComplete {
h.queueHandshakePacketsForRetransmission()
} else if !h.lossTime.IsZero() {
// Early retransmit or time loss detection
h.detectLostPackets()
} else {
@ -312,6 +327,7 @@ func (h *sentPacketHandler) GetAlarmTimeout() time.Time {
func (h *sentPacketHandler) onPacketAcked(packetElement *PacketElement) {
h.bytesInFlight -= packetElement.Value.Length
h.rtoCount = 0
h.handshakeCount = 0
// TODO(#497): h.tlpCount = 0
h.packetHistory.Remove(packetElement)
}
@ -372,6 +388,18 @@ func (h *sentPacketHandler) queueRTO(el *PacketElement) {
h.congestion.OnRetransmissionTimeout(true)
}
func (h *sentPacketHandler) queueHandshakePacketsForRetransmission() {
var handshakePackets []*PacketElement
for el := h.packetHistory.Front(); el != nil; el = el.Next() {
if el.Value.EncryptionLevel < protocol.EncryptionForwardSecure {
handshakePackets = append(handshakePackets, el)
}
}
for _, el := range handshakePackets {
h.queuePacketForRetransmission(el)
}
}
func (h *sentPacketHandler) queuePacketForRetransmission(packetElement *PacketElement) {
packet := &packetElement.Value
h.bytesInFlight -= packet.Length
@ -380,6 +408,17 @@ func (h *sentPacketHandler) queuePacketForRetransmission(packetElement *PacketEl
h.stopWaitingManager.QueuedRetransmissionForPacketNumber(packet.PacketNumber)
}
func (h *sentPacketHandler) computeHandshakeTimeout() time.Duration {
duration := 2 * h.rttStats.SmoothedRTT()
if duration == 0 {
duration = 2 * defaultInitialRTT
}
duration = utils.MaxDuration(duration, minTPLTimeout)
// exponential backoff
// There's an implicit limit to this set by the handshake timeout.
return duration << h.handshakeCount
}
func (h *sentPacketHandler) computeRTOTimeout() time.Duration {
rto := h.congestion.RetransmissionDelay()
if rto == 0 {