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ackhandler: refactor ACK queueing logic (#4225)

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Once an ACK has been queued, there's no need to check futher conditions that
would lead to queueing of an ACK.
This commit is contained in:
Marten Seemann 2024-01-04 09:39:09 +07:00 • committed by GitHub
parent 8cad3d2ea5
commit 54d6f7dc51
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 26 additions and 32 deletions
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57
internal/ackhandler/received_packet_tracker.go
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@ -56,10 +56,6 @@ func (h *receivedPacketTracker) ReceivedPacket(pn protocol.PacketNumber, ecn pro
h.largestObservedRcvdTime = rcvTime
}
if ackEliciting {
h.hasNewAck = true
h.maybeQueueACK(pn, rcvTime, ecn, isMissing)
}
//nolint:exhaustive // Only need to count ECT(0), ECT(1) and ECN-CE.
switch ecn {
case protocol.ECT0:
@ -69,6 +65,24 @@ func (h *receivedPacketTracker) ReceivedPacket(pn protocol.PacketNumber, ecn pro
case protocol.ECNCE:
h.ecnce++
}
if !ackEliciting {
return nil
}
h.hasNewAck = true
h.ackElicitingPacketsReceivedSinceLastAck++
if !h.ackQueued && h.shouldQueueACK(pn, ecn, isMissing) {
h.ackQueued = true
h.ackAlarm = time.Time{} // cancel the ack alarm
}
if !h.ackQueued {
// No ACK queued, but we'll need to acknowledge the packet after max_ack_delay.
h.ackAlarm = rcvTime.Add(h.maxAckDelay)
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to max ack delay: %s", h.maxAckDelay)
}
}
return nil
}
@ -101,23 +115,13 @@ func (h *receivedPacketTracker) hasNewMissingPackets() bool {
return highestRange.Smallest > h.lastAck.LargestAcked()+1 && highestRange.Len() == 1
}
// maybeQueueACK queues an ACK, if necessary.
func (h *receivedPacketTracker) maybeQueueACK(pn protocol.PacketNumber, rcvTime time.Time, ecn protocol.ECN, wasMissing bool) {
func (h *receivedPacketTracker) shouldQueueACK(pn protocol.PacketNumber, ecn protocol.ECN, wasMissing bool) bool {
// always acknowledge the first packet
if h.lastAck == nil {
if !h.ackQueued {
h.logger.Debugf("\tQueueing ACK because the first packet should be acknowledged.")
}
h.ackQueued = true
return
h.logger.Debugf("\tQueueing ACK because the first packet should be acknowledged.")
return true
}
if h.ackQueued {
return
}
h.ackElicitingPacketsReceivedSinceLastAck++
// 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.
@ -125,7 +129,7 @@ func (h *receivedPacketTracker) maybeQueueACK(pn protocol.PacketNumber, rcvTime
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %d was missing before.", pn)
}
h.ackQueued = true
return true
}
// send an ACK every 2 ack-eliciting packets
@ -133,30 +137,21 @@ func (h *receivedPacketTracker) maybeQueueACK(pn protocol.PacketNumber, rcvTime
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %d packets were received after the last ACK (using initial threshold: %d).", h.ackElicitingPacketsReceivedSinceLastAck, packetsBeforeAck)
}
h.ackQueued = true
} else if h.ackAlarm.IsZero() {
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to max ack delay: %s", h.maxAckDelay)
}
h.ackAlarm = rcvTime.Add(h.maxAckDelay)
return true
}
// queue an ACK if there are new missing packets to report
if h.hasNewMissingPackets() {
h.logger.Debugf("\tQueuing ACK because there's a new missing packet to report.")
h.ackQueued = true
return true
}
// queue an ACK if the packet was ECN-CE marked
if ecn == protocol.ECNCE {
h.logger.Debugf("\tQueuing ACK because the packet was ECN-CE marked.")
h.ackQueued = true
}
if h.ackQueued {
// cancel the ack alarm
h.ackAlarm = time.Time{}
return true
}
return false
}
func (h *receivedPacketTracker) GetAckFrame(onlyIfQueued bool) *wire.AckFrame {