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sent_packet_handler.go
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sent_packet_handler.go
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package ackhandler
import (
"errors"
"fmt"
"time"
"github.com/quic-go/quic-go/internal/congestion"
"github.com/quic-go/quic-go/internal/protocol"
"github.com/quic-go/quic-go/internal/qerr"
"github.com/quic-go/quic-go/internal/utils"
"github.com/quic-go/quic-go/internal/wire"
"github.com/quic-go/quic-go/logging"
)
const (
// Maximum reordering in time space before time based loss detection considers a packet lost.
// Specified as an RTT multiplier.
timeThreshold = 9.0 / 8
// Maximum reordering in packets before packet threshold loss detection considers a packet lost.
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
// 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 {
history *sentPacketHistory
pns packetNumberGenerator
lossTime time.Time
lastAckElicitingPacketTime time.Time
largestAcked protocol.PacketNumber
largestSent protocol.PacketNumber
}
func newPacketNumberSpace(initialPN protocol.PacketNumber, skipPNs bool) *packetNumberSpace {
var pns packetNumberGenerator
if skipPNs {
pns = newSkippingPacketNumberGenerator(initialPN, protocol.SkipPacketInitialPeriod, protocol.SkipPacketMaxPeriod)
} else {
pns = newSequentialPacketNumberGenerator(initialPN)
}
return &packetNumberSpace{
history: newSentPacketHistory(),
pns: pns,
largestSent: protocol.InvalidPacketNumber,
largestAcked: protocol.InvalidPacketNumber,
}
}
type sentPacketHandler struct {
initialPackets *packetNumberSpace
handshakePackets *packetNumberSpace
appDataPackets *packetNumberSpace
// Do we know that the peer completed address validation yet?
// Always true for the server.
peerCompletedAddressValidation bool
bytesReceived protocol.ByteCount
bytesSent protocol.ByteCount
// Have we validated the peer's address yet?
// Always true for the client.
peerAddressValidated bool
handshakeConfirmed bool
// lowestNotConfirmedAcked is the lowest packet number that we sent an ACK for, but haven't received confirmation, that this ACK actually arrived
// example: we send an ACK for packets 90-100 with packet number 20
// once we receive an ACK from the peer for packet 20, the lowestNotConfirmedAcked is 101
// Only applies to the application-data packet number space.
lowestNotConfirmedAcked protocol.PacketNumber
ackedPackets []*packet // to avoid allocations in detectAndRemoveAckedPackets
bytesInFlight protocol.ByteCount
congestion congestion.SendAlgorithmWithDebugInfos
rttStats *utils.RTTStats
// The number of times a PTO has been sent without receiving an ack.
ptoCount uint32
ptoMode SendMode
// The number of PTO probe packets that should be sent.
// Only applies to the application-data packet number space.
numProbesToSend int
// The alarm timeout
alarm time.Time
enableECN bool
ecnTracker ecnHandler
perspective protocol.Perspective
tracer *logging.ConnectionTracer
logger utils.Logger
}
var (
_ SentPacketHandler = &sentPacketHandler{}
_ sentPacketTracker = &sentPacketHandler{}
)
// clientAddressValidated indicates whether the address was validated beforehand by an address validation token.
// If the address was validated, the amplification limit doesn't apply. It has no effect for a client.
func newSentPacketHandler(
initialPN protocol.PacketNumber,
initialMaxDatagramSize protocol.ByteCount,
rttStats *utils.RTTStats,
clientAddressValidated bool,
enableECN bool,
pers protocol.Perspective,
tracer *logging.ConnectionTracer,
logger utils.Logger,
) *sentPacketHandler {
congestion := congestion.NewCubicSender(
congestion.DefaultClock{},
rttStats,
initialMaxDatagramSize,
true, // use Reno
tracer,
)
h := &sentPacketHandler{
peerCompletedAddressValidation: pers == protocol.PerspectiveServer,
peerAddressValidated: pers == protocol.PerspectiveClient || clientAddressValidated,
initialPackets: newPacketNumberSpace(initialPN, false),
handshakePackets: newPacketNumberSpace(0, false),
appDataPackets: newPacketNumberSpace(0, true),
rttStats: rttStats,
congestion: congestion,
perspective: pers,
tracer: tracer,
logger: logger,
}
if enableECN {
h.enableECN = true
h.ecnTracker = newECNTracker(logger, tracer)
}
return h
}
func (h *sentPacketHandler) removeFromBytesInFlight(p *packet) {
if p.includedInBytesInFlight {
if p.Length > h.bytesInFlight {
panic("negative bytes_in_flight")
}
h.bytesInFlight -= p.Length
p.includedInBytesInFlight = false
}
}
func (h *sentPacketHandler) DropPackets(encLevel protocol.EncryptionLevel) {
// The server won't await address validation after the handshake is confirmed.
// This applies even if we didn't receive an ACK for a Handshake packet.
if h.perspective == protocol.PerspectiveClient && encLevel == protocol.EncryptionHandshake {
h.peerCompletedAddressValidation = true
}
// remove outstanding packets from bytes_in_flight
if encLevel == protocol.EncryptionInitial || encLevel == protocol.EncryptionHandshake {
pnSpace := h.getPacketNumberSpace(encLevel)
// We might already have dropped this packet number space.
if pnSpace == nil {
return
}
pnSpace.history.Iterate(func(p *packet) (bool, error) {
h.removeFromBytesInFlight(p)
return true, nil
})
}
// drop the packet history
//nolint:exhaustive // Not every packet number space can be dropped.
switch encLevel {
case protocol.EncryptionInitial:
h.initialPackets = nil
case protocol.EncryptionHandshake:
h.handshakePackets = nil
case protocol.Encryption0RTT:
// This function is only called when 0-RTT is rejected,
// and not when the client drops 0-RTT keys when the handshake completes.
// When 0-RTT is rejected, all application data sent so far becomes invalid.
// Delete the packets from the history and remove them from bytes_in_flight.
h.appDataPackets.history.Iterate(func(p *packet) (bool, error) {
if p.EncryptionLevel != protocol.Encryption0RTT && !p.skippedPacket {
return false, nil
}
h.removeFromBytesInFlight(p)
h.appDataPackets.history.Remove(p.PacketNumber)
return true, nil
})
default:
panic(fmt.Sprintf("Cannot drop keys for encryption level %s", encLevel))
}
if h.tracer != nil && h.tracer.UpdatedPTOCount != nil && h.ptoCount != 0 {
h.tracer.UpdatedPTOCount(0)
}
h.ptoCount = 0
h.numProbesToSend = 0
h.ptoMode = SendNone
h.setLossDetectionTimer()
}
func (h *sentPacketHandler) ReceivedBytes(n protocol.ByteCount) {
wasAmplificationLimit := h.isAmplificationLimited()
h.bytesReceived += n
if wasAmplificationLimit && !h.isAmplificationLimited() {
h.setLossDetectionTimer()
}
}
func (h *sentPacketHandler) ReceivedPacket(l protocol.EncryptionLevel) {
if h.perspective == protocol.PerspectiveServer && l == protocol.EncryptionHandshake && !h.peerAddressValidated {
h.peerAddressValidated = true
h.setLossDetectionTimer()
}
}
func (h *sentPacketHandler) packetsInFlight() int {
packetsInFlight := h.appDataPackets.history.Len()
if h.handshakePackets != nil {
packetsInFlight += h.handshakePackets.history.Len()
}
if h.initialPackets != nil {
packetsInFlight += h.initialPackets.history.Len()
}
return packetsInFlight
}
func (h *sentPacketHandler) SentPacket(
t time.Time,
pn, largestAcked protocol.PacketNumber,
streamFrames []StreamFrame,
frames []Frame,
encLevel protocol.EncryptionLevel,
ecn protocol.ECN,
size protocol.ByteCount,
isPathMTUProbePacket bool,
) {
h.bytesSent += size
pnSpace := h.getPacketNumberSpace(encLevel)
if h.logger.Debug() && pnSpace.history.HasOutstandingPackets() {
for p := utils.Max(0, pnSpace.largestSent+1); p < pn; p++ {
h.logger.Debugf("Skipping packet number %d", p)
}
}
pnSpace.largestSent = pn
isAckEliciting := len(streamFrames) > 0 || len(frames) > 0
if isAckEliciting {
pnSpace.lastAckElicitingPacketTime = t
h.bytesInFlight += size
if h.numProbesToSend > 0 {
h.numProbesToSend--
}
}
h.congestion.OnPacketSent(t, h.bytesInFlight, pn, size, isAckEliciting)
if encLevel == protocol.Encryption1RTT && h.ecnTracker != nil {
h.ecnTracker.SentPacket(pn, ecn)
}
if !isAckEliciting {
pnSpace.history.SentNonAckElicitingPacket(pn)
if !h.peerCompletedAddressValidation {
h.setLossDetectionTimer()
}
return
}
p := getPacket()
p.SendTime = t
p.PacketNumber = pn
p.EncryptionLevel = encLevel
p.Length = size
p.LargestAcked = largestAcked
p.StreamFrames = streamFrames
p.Frames = frames
p.IsPathMTUProbePacket = isPathMTUProbePacket
p.includedInBytesInFlight = true
pnSpace.history.SentAckElicitingPacket(p)
if h.tracer != nil && h.tracer.UpdatedMetrics != nil {
h.tracer.UpdatedMetrics(h.rttStats, h.congestion.GetCongestionWindow(), h.bytesInFlight, h.packetsInFlight())
}
h.setLossDetectionTimer()
}
func (h *sentPacketHandler) getPacketNumberSpace(encLevel protocol.EncryptionLevel) *packetNumberSpace {
switch encLevel {
case protocol.EncryptionInitial:
return h.initialPackets
case protocol.EncryptionHandshake:
return h.handshakePackets
case protocol.Encryption0RTT, protocol.Encryption1RTT:
return h.appDataPackets
default:
panic("invalid packet number space")
}
}
func (h *sentPacketHandler) ReceivedAck(ack *wire.AckFrame, encLevel protocol.EncryptionLevel, rcvTime time.Time) (bool /* contained 1-RTT packet */, error) {
pnSpace := h.getPacketNumberSpace(encLevel)
largestAcked := ack.LargestAcked()
if largestAcked > pnSpace.largestSent {
return false, &qerr.TransportError{
ErrorCode: qerr.ProtocolViolation,
ErrorMessage: "received ACK for an unsent packet",
}
}
// Servers complete address validation when a protected packet is received.
if h.perspective == protocol.PerspectiveClient && !h.peerCompletedAddressValidation &&
(encLevel == protocol.EncryptionHandshake || encLevel == protocol.Encryption1RTT) {
h.peerCompletedAddressValidation = true
h.logger.Debugf("Peer doesn't await address validation any longer.")
// Make sure that the timer is reset, even if this ACK doesn't acknowledge any (ack-eliciting) packets.
h.setLossDetectionTimer()
}
priorInFlight := h.bytesInFlight
ackedPackets, err := h.detectAndRemoveAckedPackets(ack, encLevel)
if err != nil || len(ackedPackets) == 0 {
return false, err
}
// update the RTT, if the largest acked is newly acknowledged
if len(ackedPackets) > 0 {
if p := ackedPackets[len(ackedPackets)-1]; p.PacketNumber == ack.LargestAcked() {
// don't use the ack delay for Initial and Handshake packets
var ackDelay time.Duration
if encLevel == protocol.Encryption1RTT {
ackDelay = utils.Min(ack.DelayTime, h.rttStats.MaxAckDelay())
}
h.rttStats.UpdateRTT(rcvTime.Sub(p.SendTime), ackDelay, rcvTime)
if h.logger.Debug() {
h.logger.Debugf("\tupdated RTT: %s (σ: %s)", h.rttStats.SmoothedRTT(), h.rttStats.MeanDeviation())
}
h.congestion.MaybeExitSlowStart()
}
}
// Only inform the ECN tracker about new 1-RTT ACKs if the ACK increases the largest acked.
if encLevel == protocol.Encryption1RTT && h.ecnTracker != nil && largestAcked > pnSpace.largestAcked {
congested := h.ecnTracker.HandleNewlyAcked(ackedPackets, int64(ack.ECT0), int64(ack.ECT1), int64(ack.ECNCE))
if congested {
h.congestion.OnCongestionEvent(largestAcked, 0, priorInFlight)
}
}
pnSpace.largestAcked = utils.Max(pnSpace.largestAcked, largestAcked)
if err := h.detectLostPackets(rcvTime, encLevel); err != nil {
return false, err
}
var acked1RTTPacket bool
for _, p := range ackedPackets {
if p.includedInBytesInFlight && !p.declaredLost {
h.congestion.OnPacketAcked(p.PacketNumber, p.Length, priorInFlight, rcvTime)
}
if p.EncryptionLevel == protocol.Encryption1RTT {
acked1RTTPacket = true
}
h.removeFromBytesInFlight(p)
putPacket(p)
}
// After this point, we must not use ackedPackets any longer!
// We've already returned the buffers.
ackedPackets = nil //nolint:ineffassign // This is just to be on the safe side.
// Reset the pto_count unless the client is unsure if the server has validated the client's address.
if h.peerCompletedAddressValidation {
if h.tracer != nil && h.tracer.UpdatedPTOCount != nil && h.ptoCount != 0 {
h.tracer.UpdatedPTOCount(0)
}
h.ptoCount = 0
}
h.numProbesToSend = 0
if h.tracer != nil && h.tracer.UpdatedMetrics != nil {
h.tracer.UpdatedMetrics(h.rttStats, h.congestion.GetCongestionWindow(), h.bytesInFlight, h.packetsInFlight())
}
h.setLossDetectionTimer()
return acked1RTTPacket, nil
}
func (h *sentPacketHandler) GetLowestPacketNotConfirmedAcked() protocol.PacketNumber {
return h.lowestNotConfirmedAcked
}
// Packets are returned in ascending packet number order.
func (h *sentPacketHandler) detectAndRemoveAckedPackets(ack *wire.AckFrame, encLevel protocol.EncryptionLevel) ([]*packet, error) {
pnSpace := h.getPacketNumberSpace(encLevel)
h.ackedPackets = h.ackedPackets[:0]
ackRangeIndex := 0
lowestAcked := ack.LowestAcked()
largestAcked := ack.LargestAcked()
err := pnSpace.history.Iterate(func(p *packet) (bool, error) {
// Ignore packets below the lowest acked
if p.PacketNumber < lowestAcked {
return true, nil
}
// Break after largest acked is reached
if p.PacketNumber > largestAcked {
return false, nil
}
if ack.HasMissingRanges() {
ackRange := ack.AckRanges[len(ack.AckRanges)-1-ackRangeIndex]
for p.PacketNumber > ackRange.Largest && ackRangeIndex < len(ack.AckRanges)-1 {
ackRangeIndex++
ackRange = ack.AckRanges[len(ack.AckRanges)-1-ackRangeIndex]
}
if p.PacketNumber < ackRange.Smallest { // packet not contained in ACK range
return true, nil
}
if p.PacketNumber > ackRange.Largest {
return false, fmt.Errorf("BUG: ackhandler would have acked wrong packet %d, while evaluating range %d -> %d", p.PacketNumber, ackRange.Smallest, ackRange.Largest)
}
}
if p.skippedPacket {
return false, &qerr.TransportError{
ErrorCode: qerr.ProtocolViolation,
ErrorMessage: fmt.Sprintf("received an ACK for skipped packet number: %d (%s)", p.PacketNumber, encLevel),
}
}
h.ackedPackets = append(h.ackedPackets, p)
return true, nil
})
if h.logger.Debug() && len(h.ackedPackets) > 0 {
pns := make([]protocol.PacketNumber, len(h.ackedPackets))
for i, p := range h.ackedPackets {
pns[i] = p.PacketNumber
}
h.logger.Debugf("\tnewly acked packets (%d): %d", len(pns), pns)
}
for _, p := range h.ackedPackets {
if p.LargestAcked != protocol.InvalidPacketNumber && encLevel == protocol.Encryption1RTT {
h.lowestNotConfirmedAcked = utils.Max(h.lowestNotConfirmedAcked, p.LargestAcked+1)
}
for _, f := range p.Frames {
if f.Handler != nil {
f.Handler.OnAcked(f.Frame)
}
}
for _, f := range p.StreamFrames {
if f.Handler != nil {
f.Handler.OnAcked(f.Frame)
}
}
if err := pnSpace.history.Remove(p.PacketNumber); err != nil {
return nil, err
}
if h.tracer != nil && h.tracer.AcknowledgedPacket != nil {
h.tracer.AcknowledgedPacket(encLevel, p.PacketNumber)
}
}
return h.ackedPackets, err
}
func (h *sentPacketHandler) getLossTimeAndSpace() (time.Time, protocol.EncryptionLevel) {
var encLevel protocol.EncryptionLevel
var lossTime time.Time
if h.initialPackets != nil {
lossTime = h.initialPackets.lossTime
encLevel = protocol.EncryptionInitial
}
if h.handshakePackets != nil && (lossTime.IsZero() || (!h.handshakePackets.lossTime.IsZero() && h.handshakePackets.lossTime.Before(lossTime))) {
lossTime = h.handshakePackets.lossTime
encLevel = protocol.EncryptionHandshake
}
if lossTime.IsZero() || (!h.appDataPackets.lossTime.IsZero() && h.appDataPackets.lossTime.Before(lossTime)) {
lossTime = h.appDataPackets.lossTime
encLevel = protocol.Encryption1RTT
}
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,
// because before that, we don't have the keys to decrypt ACKs sent in 1-RTT packets.
if !h.handshakeConfirmed && !h.hasOutstandingCryptoPackets() {
if h.peerCompletedAddressValidation {
return
}
t := time.Now().Add(h.getScaledPTO(false))
if h.initialPackets != nil {
return t, protocol.EncryptionInitial, true
}
return t, protocol.EncryptionHandshake, true
}
if h.initialPackets != nil {
encLevel = protocol.EncryptionInitial
if t := h.initialPackets.lastAckElicitingPacketTime; !t.IsZero() {
pto = t.Add(h.getScaledPTO(false))
}
}
if h.handshakePackets != nil && !h.handshakePackets.lastAckElicitingPacketTime.IsZero() {
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.getScaledPTO(true))
if pto.IsZero() || (!t.IsZero() && t.Before(pto)) {
pto = t
encLevel = protocol.Encryption1RTT
}
}
return pto, encLevel, true
}
func (h *sentPacketHandler) hasOutstandingCryptoPackets() bool {
if h.initialPackets != nil && h.initialPackets.history.HasOutstandingPackets() {
return true
}
if h.handshakePackets != nil && h.handshakePackets.history.HasOutstandingPackets() {
return true
}
return false
}
func (h *sentPacketHandler) hasOutstandingPackets() bool {
return h.appDataPackets.history.HasOutstandingPackets() || h.hasOutstandingCryptoPackets()
}
func (h *sentPacketHandler) setLossDetectionTimer() {
oldAlarm := h.alarm // only needed in case tracing is enabled
lossTime, encLevel := h.getLossTimeAndSpace()
if !lossTime.IsZero() {
// Early retransmit timer or time loss detection.
h.alarm = lossTime
if h.tracer != nil && h.tracer.SetLossTimer != nil && h.alarm != oldAlarm {
h.tracer.SetLossTimer(logging.TimerTypeACK, encLevel, h.alarm)
}
return
}
// Cancel the alarm if amplification limited.
if h.isAmplificationLimited() {
h.alarm = time.Time{}
if !oldAlarm.IsZero() {
h.logger.Debugf("Canceling loss detection timer. Amplification limited.")
if h.tracer != nil && h.tracer.LossTimerCanceled != nil {
h.tracer.LossTimerCanceled()
}
}
return
}
// Cancel the alarm if no packets are outstanding
if !h.hasOutstandingPackets() && h.peerCompletedAddressValidation {
h.alarm = time.Time{}
if !oldAlarm.IsZero() {
h.logger.Debugf("Canceling loss detection timer. No packets in flight.")
if h.tracer != nil && h.tracer.LossTimerCanceled != nil {
h.tracer.LossTimerCanceled()
}
}
return
}
// PTO alarm
ptoTime, encLevel, ok := h.getPTOTimeAndSpace()
if !ok {
if !oldAlarm.IsZero() {
h.alarm = time.Time{}
h.logger.Debugf("Canceling loss detection timer. No PTO needed..")
if h.tracer != nil && h.tracer.LossTimerCanceled != nil {
h.tracer.LossTimerCanceled()
}
}
return
}
h.alarm = ptoTime
if h.tracer != nil && h.tracer.SetLossTimer != nil && h.alarm != oldAlarm {
h.tracer.SetLossTimer(logging.TimerTypePTO, encLevel, h.alarm)
}
}
func (h *sentPacketHandler) detectLostPackets(now time.Time, encLevel protocol.EncryptionLevel) error {
pnSpace := h.getPacketNumberSpace(encLevel)
pnSpace.lossTime = time.Time{}
maxRTT := float64(utils.Max(h.rttStats.LatestRTT(), h.rttStats.SmoothedRTT()))
lossDelay := time.Duration(timeThreshold * maxRTT)
// Minimum time of granularity before packets are deemed lost.
lossDelay = utils.Max(lossDelay, protocol.TimerGranularity)
// Packets sent before this time are deemed lost.
lostSendTime := now.Add(-lossDelay)
priorInFlight := h.bytesInFlight
return pnSpace.history.Iterate(func(p *packet) (bool, error) {
if p.PacketNumber > pnSpace.largestAcked {
return false, nil
}
var packetLost bool
if p.SendTime.Before(lostSendTime) {
packetLost = true
if !p.skippedPacket {
if h.logger.Debug() {
h.logger.Debugf("\tlost packet %d (time threshold)", p.PacketNumber)
}
if h.tracer != nil && h.tracer.LostPacket != nil {
h.tracer.LostPacket(p.EncryptionLevel, p.PacketNumber, logging.PacketLossTimeThreshold)
}
}
} else if pnSpace.largestAcked >= p.PacketNumber+packetThreshold {
packetLost = true
if !p.skippedPacket {
if h.logger.Debug() {
h.logger.Debugf("\tlost packet %d (reordering threshold)", p.PacketNumber)
}
if h.tracer != nil && h.tracer.LostPacket != nil {
h.tracer.LostPacket(p.EncryptionLevel, p.PacketNumber, logging.PacketLossReorderingThreshold)
}
}
} else if pnSpace.lossTime.IsZero() {
// Note: This conditional is only entered once per call
lossTime := p.SendTime.Add(lossDelay)
if h.logger.Debug() {
h.logger.Debugf("\tsetting loss timer for packet %d (%s) to %s (in %s)", p.PacketNumber, encLevel, lossDelay, lossTime)
}
pnSpace.lossTime = lossTime
}
if packetLost {
pnSpace.history.DeclareLost(p.PacketNumber)
if !p.skippedPacket {
// the bytes in flight need to be reduced no matter if the frames in this packet will be retransmitted
h.removeFromBytesInFlight(p)
h.queueFramesForRetransmission(p)
if !p.IsPathMTUProbePacket {
h.congestion.OnCongestionEvent(p.PacketNumber, p.Length, priorInFlight)
}
if encLevel == protocol.Encryption1RTT && h.ecnTracker != nil {
h.ecnTracker.LostPacket(p.PacketNumber)
}
}
}
return true, nil
})
}
func (h *sentPacketHandler) OnLossDetectionTimeout() error {
defer h.setLossDetectionTimer()
earliestLossTime, encLevel := h.getLossTimeAndSpace()
if !earliestLossTime.IsZero() {
if h.logger.Debug() {
h.logger.Debugf("Loss detection alarm fired in loss timer mode. Loss time: %s", earliestLossTime)
}
if h.tracer != nil && h.tracer.LossTimerExpired != nil {
h.tracer.LossTimerExpired(logging.TimerTypeACK, encLevel)
}
// Early retransmit or time loss detection
return h.detectLostPackets(time.Now(), encLevel)
}
// PTO
// When all outstanding are acknowledged, the alarm is canceled in
// setLossDetectionTimer. This doesn't reset the timer in the session though.
// When OnAlarm is called, we therefore need to make sure that there are
// actually packets outstanding.
if h.bytesInFlight == 0 && !h.peerCompletedAddressValidation {
h.ptoCount++
h.numProbesToSend++
if h.initialPackets != nil {
h.ptoMode = SendPTOInitial
} else if h.handshakePackets != nil {
h.ptoMode = SendPTOHandshake
} else {
return errors.New("sentPacketHandler BUG: PTO fired, but bytes_in_flight is 0 and Initial and Handshake already dropped")
}
return nil
}
_, encLevel, ok := h.getPTOTimeAndSpace()
if !ok {
return nil
}
if ps := h.getPacketNumberSpace(encLevel); !ps.history.HasOutstandingPackets() && !h.peerCompletedAddressValidation {
return nil
}
h.ptoCount++
if h.logger.Debug() {
h.logger.Debugf("Loss detection alarm for %s fired in PTO mode. PTO count: %d", encLevel, h.ptoCount)
}
if h.tracer != nil {
if h.tracer.LossTimerExpired != nil {
h.tracer.LossTimerExpired(logging.TimerTypePTO, encLevel)
}
if h.tracer.UpdatedPTOCount != nil {
h.tracer.UpdatedPTOCount(h.ptoCount)
}
}
h.numProbesToSend += 2
//nolint:exhaustive // We never arm a PTO timer for 0-RTT packets.
switch encLevel {
case protocol.EncryptionInitial:
h.ptoMode = SendPTOInitial
case protocol.EncryptionHandshake:
h.ptoMode = SendPTOHandshake
case protocol.Encryption1RTT:
// skip a packet number in order to elicit an immediate ACK
pn := h.PopPacketNumber(protocol.Encryption1RTT)
h.getPacketNumberSpace(protocol.Encryption1RTT).history.SkippedPacket(pn)
h.ptoMode = SendPTOAppData
default:
return fmt.Errorf("PTO timer in unexpected encryption level: %s", encLevel)
}
return nil
}
func (h *sentPacketHandler) GetLossDetectionTimeout() time.Time {
return h.alarm
}
func (h *sentPacketHandler) ECNMode(isShortHeaderPacket bool) protocol.ECN {
if !h.enableECN {
return protocol.ECNUnsupported
}
if !isShortHeaderPacket {
return protocol.ECNNon
}
return h.ecnTracker.Mode()
}
func (h *sentPacketHandler) PeekPacketNumber(encLevel protocol.EncryptionLevel) (protocol.PacketNumber, protocol.PacketNumberLen) {
pnSpace := h.getPacketNumberSpace(encLevel)
pn := pnSpace.pns.Peek()
// See section 17.1 of RFC 9000.
return pn, protocol.GetPacketNumberLengthForHeader(pn, pnSpace.largestAcked)
}
func (h *sentPacketHandler) PopPacketNumber(encLevel protocol.EncryptionLevel) protocol.PacketNumber {
pnSpace := h.getPacketNumberSpace(encLevel)
skipped, pn := pnSpace.pns.Pop()
if skipped {
skippedPN := pn - 1
pnSpace.history.SkippedPacket(skippedPN)
if h.logger.Debug() {
h.logger.Debugf("Skipping packet number %d", skippedPN)
}
}
return pn
}
func (h *sentPacketHandler) SendMode(now time.Time) SendMode {
numTrackedPackets := h.appDataPackets.history.Len()
if h.initialPackets != nil {
numTrackedPackets += h.initialPackets.history.Len()
}
if h.handshakePackets != nil {
numTrackedPackets += h.handshakePackets.history.Len()
}
if h.isAmplificationLimited() {
h.logger.Debugf("Amplification window limited. Received %d bytes, already sent out %d bytes", h.bytesReceived, h.bytesSent)
return SendNone
}
// Don't send any packets if we're keeping track of the maximum number of packets.
// Note that since MaxOutstandingSentPackets is smaller than MaxTrackedSentPackets,
// we will stop sending out new data when reaching MaxOutstandingSentPackets,
// but still allow sending of retransmissions and ACKs.
if numTrackedPackets >= protocol.MaxTrackedSentPackets {
if h.logger.Debug() {
h.logger.Debugf("Limited by the number of tracked packets: tracking %d packets, maximum %d", numTrackedPackets, protocol.MaxTrackedSentPackets)
}
return SendNone
}
if h.numProbesToSend > 0 {
return h.ptoMode
}
// Only send ACKs if we're congestion limited.
if !h.congestion.CanSend(h.bytesInFlight) {
if h.logger.Debug() {
h.logger.Debugf("Congestion limited: bytes in flight %d, window %d", h.bytesInFlight, h.congestion.GetCongestionWindow())
}
return SendAck
}
if numTrackedPackets >= protocol.MaxOutstandingSentPackets {
if h.logger.Debug() {
h.logger.Debugf("Max outstanding limited: tracking %d packets, maximum: %d", numTrackedPackets, protocol.MaxOutstandingSentPackets)
}
return SendAck
}
if !h.congestion.HasPacingBudget(now) {
return SendPacingLimited
}
return SendAny
}
func (h *sentPacketHandler) TimeUntilSend() time.Time {
return h.congestion.TimeUntilSend(h.bytesInFlight)
}
func (h *sentPacketHandler) SetMaxDatagramSize(s protocol.ByteCount) {
h.congestion.SetMaxDatagramSize(s)
}
func (h *sentPacketHandler) isAmplificationLimited() bool {
if h.peerAddressValidated {
return false
}
return h.bytesSent >= amplificationFactor*h.bytesReceived
}
func (h *sentPacketHandler) QueueProbePacket(encLevel protocol.EncryptionLevel) bool {
pnSpace := h.getPacketNumberSpace(encLevel)
p := pnSpace.history.FirstOutstanding()
if p == nil {
return false
}
h.queueFramesForRetransmission(p)
// TODO: don't declare the packet lost here.
// Keep track of acknowledged frames instead.
h.removeFromBytesInFlight(p)
pnSpace.history.DeclareLost(p.PacketNumber)
return true
}
func (h *sentPacketHandler) queueFramesForRetransmission(p *packet) {
if len(p.Frames) == 0 && len(p.StreamFrames) == 0 {
panic("no frames")
}
for _, f := range p.Frames {
if f.Handler != nil {
f.Handler.OnLost(f.Frame)
}
}
for _, f := range p.StreamFrames {
if f.Handler != nil {
f.Handler.OnLost(f.Frame)
}
}
p.StreamFrames = nil
p.Frames = nil
}
func (h *sentPacketHandler) ResetForRetry(now time.Time) error {
h.bytesInFlight = 0
var firstPacketSendTime time.Time
h.initialPackets.history.Iterate(func(p *packet) (bool, error) {
if firstPacketSendTime.IsZero() {
firstPacketSendTime = p.SendTime
}
if p.declaredLost || p.skippedPacket {
return true, nil
}
h.queueFramesForRetransmission(p)
return true, nil
})
// All application data packets sent at this point are 0-RTT packets.
// In the case of a Retry, we can assume that the server dropped all of them.
h.appDataPackets.history.Iterate(func(p *packet) (bool, error) {
if !p.declaredLost && !p.skippedPacket {
h.queueFramesForRetransmission(p)
}
return true, nil
})
// 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.
h.rttStats.UpdateRTT(utils.Max(minRTTAfterRetry, now.Sub(firstPacketSendTime)), 0, now)
if h.logger.Debug() {
h.logger.Debugf("\tupdated RTT: %s (σ: %s)", h.rttStats.SmoothedRTT(), h.rttStats.MeanDeviation())
}
if h.tracer != nil && h.tracer.UpdatedMetrics != nil {
h.tracer.UpdatedMetrics(h.rttStats, h.congestion.GetCongestionWindow(), h.bytesInFlight, h.packetsInFlight())
}
}
h.initialPackets = newPacketNumberSpace(h.initialPackets.pns.Peek(), false)
h.appDataPackets = newPacketNumberSpace(h.appDataPackets.pns.Peek(), true)
oldAlarm := h.alarm
h.alarm = time.Time{}
if h.tracer != nil {
if h.tracer.UpdatedPTOCount != nil {
h.tracer.UpdatedPTOCount(0)
}
if !oldAlarm.IsZero() && h.tracer.LossTimerCanceled != nil {
h.tracer.LossTimerCanceled()
}
}
h.ptoCount = 0
return nil
}
func (h *sentPacketHandler) SetHandshakeConfirmed() {
if h.initialPackets != nil {
panic("didn't drop initial correctly")
}
if h.handshakePackets != nil {
panic("didn't drop handshake correctly")
}
h.handshakeConfirmed = true
// We don't send PTOs for application data packets before the handshake completes.
// Make sure the timer is armed now, if necessary.
h.setLossDetectionTimer()
}