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received_packet_tracker.go
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received_packet_tracker.go
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package ackhandler
import (
"time"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/congestion"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/protocol"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/utils"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/wire"
)
type receivedPacketTracker struct {
largestObserved protocol.PacketNumber
ignoreBelow protocol.PacketNumber
largestObservedReceivedTime time.Time
packetHistory *receivedPacketHistory
ackSendDelay time.Duration
rttStats *congestion.RTTStats
packetsReceivedSinceLastAck int
retransmittablePacketsReceivedSinceLastAck int
ackQueued bool
ackAlarm time.Time
lastAck *wire.AckFrame
logger utils.Logger
version protocol.VersionNumber
}
func newReceivedPacketTracker(
rttStats *congestion.RTTStats,
logger utils.Logger,
version protocol.VersionNumber,
) *receivedPacketTracker {
return &receivedPacketTracker{
packetHistory: newReceivedPacketHistory(),
ackSendDelay: ackSendDelay,
rttStats: rttStats,
logger: logger,
version: version,
}
}
func (h *receivedPacketTracker) ReceivedPacket(packetNumber protocol.PacketNumber, rcvTime time.Time, shouldInstigateAck bool) error {
if packetNumber < h.ignoreBelow {
return nil
}
isMissing := h.isMissing(packetNumber)
if packetNumber >= h.largestObserved {
h.largestObserved = packetNumber
h.largestObservedReceivedTime = rcvTime
}
if err := h.packetHistory.ReceivedPacket(packetNumber); err != nil {
return err
}
h.maybeQueueAck(packetNumber, rcvTime, shouldInstigateAck, isMissing)
return nil
}
// IgnoreBelow sets a lower limit for acking packets.
// Packets with packet numbers smaller than p will not be acked.
func (h *receivedPacketTracker) IgnoreBelow(p protocol.PacketNumber) {
if p <= h.ignoreBelow {
return
}
h.ignoreBelow = p
h.packetHistory.DeleteBelow(p)
if h.logger.Debug() {
h.logger.Debugf("\tIgnoring all packets below %#x.", p)
}
}
// isMissing says if a packet was reported missing in the last ACK.
func (h *receivedPacketTracker) isMissing(p protocol.PacketNumber) bool {
if h.lastAck == nil || p < h.ignoreBelow {
return false
}
return p < h.lastAck.LargestAcked() && !h.lastAck.AcksPacket(p)
}
func (h *receivedPacketTracker) hasNewMissingPackets() bool {
if h.lastAck == nil {
return false
}
highestRange := h.packetHistory.GetHighestAckRange()
return highestRange.Smallest >= h.lastAck.LargestAcked() && highestRange.Len() <= maxPacketsAfterNewMissing
}
// maybeQueueAck queues an ACK, if necessary.
// It is implemented analogously to Chrome's QuicConnection::MaybeQueueAck()
// in ACK_DECIMATION_WITH_REORDERING mode.
func (h *receivedPacketTracker) maybeQueueAck(packetNumber protocol.PacketNumber, rcvTime time.Time, shouldInstigateAck, wasMissing bool) {
h.packetsReceivedSinceLastAck++
// always ack the first packet
if h.lastAck == nil {
h.logger.Debugf("\tQueueing ACK because the first packet should be acknowledged.")
h.ackQueued = true
return
}
// Send an ACK if this packet was reported missing in an ACK sent before.
// Ack decimation with reordering relies on the timer to send an ACK, but if
// missing packets we reported in the previous ack, send an ACK immediately.
if wasMissing {
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %#x was missing before.", packetNumber)
}
h.ackQueued = true
}
if !h.ackQueued && shouldInstigateAck {
h.retransmittablePacketsReceivedSinceLastAck++
if packetNumber > minReceivedBeforeAckDecimation {
// ack up to 10 packets at once
if h.retransmittablePacketsReceivedSinceLastAck >= retransmittablePacketsBeforeAck {
h.ackQueued = true
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %d packets were received after the last ACK (using threshold: %d).", h.retransmittablePacketsReceivedSinceLastAck, retransmittablePacketsBeforeAck)
}
} else if h.ackAlarm.IsZero() {
// wait for the minimum of the ack decimation delay or the delayed ack time before sending an ack
ackDelay := utils.MinDuration(ackSendDelay, time.Duration(float64(h.rttStats.MinRTT())*float64(ackDecimationDelay)))
h.ackAlarm = rcvTime.Add(ackDelay)
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to min(1/4 min-RTT, max ack delay): %s (%s from now)", ackDelay, time.Until(h.ackAlarm))
}
}
} else {
// send an ACK every 2 retransmittable packets
if h.retransmittablePacketsReceivedSinceLastAck >= initialRetransmittablePacketsBeforeAck {
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %d packets were received after the last ACK (using initial threshold: %d).", h.retransmittablePacketsReceivedSinceLastAck, initialRetransmittablePacketsBeforeAck)
}
h.ackQueued = true
} else if h.ackAlarm.IsZero() {
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to max ack delay: %s", ackSendDelay)
}
h.ackAlarm = rcvTime.Add(ackSendDelay)
}
}
// If there are new missing packets to report, set a short timer to send an ACK.
if h.hasNewMissingPackets() {
// wait the minimum of 1/8 min RTT and the existing ack time
ackDelay := time.Duration(float64(h.rttStats.MinRTT()) * float64(shortAckDecimationDelay))
ackTime := rcvTime.Add(ackDelay)
if h.ackAlarm.IsZero() || h.ackAlarm.After(ackTime) {
h.ackAlarm = ackTime
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to 1/8 min-RTT: %s (%s from now)", ackDelay, time.Until(h.ackAlarm))
}
}
}
}
if h.ackQueued {
// cancel the ack alarm
h.ackAlarm = time.Time{}
}
}
func (h *receivedPacketTracker) GetAckFrame() *wire.AckFrame {
now := time.Now()
if !h.ackQueued && (h.ackAlarm.IsZero() || h.ackAlarm.After(now)) {
return nil
}
if h.logger.Debug() && !h.ackQueued && !h.ackAlarm.IsZero() {
h.logger.Debugf("Sending ACK because the ACK timer expired.")
}
ack := &wire.AckFrame{
AckRanges: h.packetHistory.GetAckRanges(),
DelayTime: now.Sub(h.largestObservedReceivedTime),
}
h.lastAck = ack
h.ackAlarm = time.Time{}
h.ackQueued = false
h.packetsReceivedSinceLastAck = 0
h.retransmittablePacketsReceivedSinceLastAck = 0
return ack
}
func (h *receivedPacketTracker) GetAlarmTimeout() time.Time { return h.ackAlarm }