/
sent_packet_handler.go
681 lines (600 loc) · 21.6 KB
/
sent_packet_handler.go
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package ackhandler
import (
"errors"
"fmt"
"math"
"time"
"github.com/lucas-clemente/quic-go/internal/congestion"
"github.com/lucas-clemente/quic-go/internal/protocol"
"github.com/lucas-clemente/quic-go/internal/qerr"
"github.com/lucas-clemente/quic-go/internal/utils"
"github.com/lucas-clemente/quic-go/internal/wire"
"github.com/lucas-clemente/quic-go/quictrace"
)
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
)
type packetNumberSpace struct {
history *sentPacketHistory
pns *packetNumberGenerator
lossTime time.Time
largestAcked protocol.PacketNumber
largestSent protocol.PacketNumber
}
func newPacketNumberSpace(initialPN protocol.PacketNumber) *packetNumberSpace {
return &packetNumberSpace{
history: newSentPacketHistory(),
pns: newPacketNumberGenerator(initialPN, protocol.SkipPacketAveragePeriodLength),
largestSent: protocol.InvalidPacketNumber,
largestAcked: protocol.InvalidPacketNumber,
}
}
type sentPacketHandler struct {
lastSentAckElicitingPacketTime time.Time // only applies to the application-data packet number space
lastSentCryptoPacketTime time.Time
nextSendTime time.Time
initialPackets *packetNumberSpace
handshakePackets *packetNumberSpace
oneRTTPackets *packetNumberSpace
// 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
retransmissionQueue []*Packet
bytesInFlight protocol.ByteCount
congestion congestion.SendAlgorithmWithDebugInfos
rttStats *congestion.RTTStats
// The number of times a PTO has been sent without receiving an ack.
ptoCount uint32
// 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
traceCallback func(quictrace.Event)
logger utils.Logger
}
// NewSentPacketHandler creates a new sentPacketHandler
func NewSentPacketHandler(
initialPacketNumber protocol.PacketNumber,
rttStats *congestion.RTTStats,
traceCallback func(quictrace.Event),
logger utils.Logger,
) SentPacketHandler {
congestion := congestion.NewCubicSender(
congestion.DefaultClock{},
rttStats,
true, // use Reno
protocol.InitialCongestionWindow,
protocol.DefaultMaxCongestionWindow,
)
return &sentPacketHandler{
initialPackets: newPacketNumberSpace(initialPacketNumber),
handshakePackets: newPacketNumberSpace(0),
oneRTTPackets: newPacketNumberSpace(0),
rttStats: rttStats,
congestion: congestion,
traceCallback: traceCallback,
logger: logger,
}
}
func (h *sentPacketHandler) DropPackets(encLevel protocol.EncryptionLevel) {
// remove outstanding packets from bytes_in_flight
pnSpace := h.getPacketNumberSpace(encLevel)
pnSpace.history.Iterate(func(p *Packet) (bool, error) {
if p.includedInBytesInFlight {
h.bytesInFlight -= p.Length
}
return true, nil
})
// remove packets from the retransmission queue
var queue []*Packet
for _, packet := range h.retransmissionQueue {
if packet.EncryptionLevel != encLevel {
queue = append(queue, packet)
}
}
h.retransmissionQueue = queue
// drop the packet history
switch encLevel {
case protocol.EncryptionInitial:
h.initialPackets = nil
case protocol.EncryptionHandshake:
h.handshakePackets = nil
default:
panic(fmt.Sprintf("Cannot drop keys for encryption level %s", encLevel))
}
}
func (h *sentPacketHandler) SentPacket(packet *Packet) {
if isAckEliciting := h.sentPacketImpl(packet); isAckEliciting {
h.getPacketNumberSpace(packet.EncryptionLevel).history.SentPacket(packet)
h.setLossDetectionTimer()
}
}
func (h *sentPacketHandler) SentPacketsAsRetransmission(packets []*Packet, retransmissionOf protocol.PacketNumber) {
var p []*Packet
for _, packet := range packets {
if isAckEliciting := h.sentPacketImpl(packet); isAckEliciting {
p = append(p, packet)
}
}
h.getPacketNumberSpace(p[0].EncryptionLevel).history.SentPacketsAsRetransmission(p, retransmissionOf)
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.Encryption1RTT:
return h.oneRTTPackets
default:
panic("invalid packet number space")
}
}
func (h *sentPacketHandler) sentPacketImpl(packet *Packet) bool /* is ack-eliciting */ {
pnSpace := h.getPacketNumberSpace(packet.EncryptionLevel)
if h.logger.Debug() {
for p := utils.MaxPacketNumber(0, pnSpace.largestSent+1); p < packet.PacketNumber; p++ {
h.logger.Debugf("Skipping packet number %#x", p)
}
}
pnSpace.largestSent = packet.PacketNumber
packet.largestAcked = protocol.InvalidPacketNumber
if packet.Ack != nil {
packet.largestAcked = packet.Ack.LargestAcked()
}
packet.Ack = nil // no need to save the ACK
isAckEliciting := len(packet.Frames) > 0
if isAckEliciting {
if packet.EncryptionLevel != protocol.Encryption1RTT {
h.lastSentCryptoPacketTime = packet.SendTime
}
h.lastSentAckElicitingPacketTime = packet.SendTime
packet.includedInBytesInFlight = true
h.bytesInFlight += packet.Length
packet.canBeRetransmitted = true
if h.numProbesToSend > 0 {
h.numProbesToSend--
}
}
h.congestion.OnPacketSent(packet.SendTime, h.bytesInFlight, packet.PacketNumber, packet.Length, isAckEliciting)
h.nextSendTime = utils.MaxTime(h.nextSendTime, packet.SendTime).Add(h.congestion.TimeUntilSend(h.bytesInFlight))
return isAckEliciting
}
func (h *sentPacketHandler) ReceivedAck(ackFrame *wire.AckFrame, withPacketNumber protocol.PacketNumber, encLevel protocol.EncryptionLevel, rcvTime time.Time) error {
pnSpace := h.getPacketNumberSpace(encLevel)
largestAcked := ackFrame.LargestAcked()
if largestAcked > pnSpace.largestSent {
return qerr.Error(qerr.ProtocolViolation, "Received ACK for an unsent packet")
}
pnSpace.largestAcked = utils.MaxPacketNumber(pnSpace.largestAcked, largestAcked)
if !pnSpace.pns.Validate(ackFrame) {
return qerr.Error(qerr.ProtocolViolation, "Received an ACK for a skipped packet number")
}
// maybe update the RTT
if p := pnSpace.history.GetPacket(ackFrame.LargestAcked()); p != nil {
// don't use the ack delay for Initial and Handshake packets
var ackDelay time.Duration
if encLevel == protocol.Encryption1RTT {
ackDelay = utils.MinDuration(ackFrame.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()
}
ackedPackets, err := h.determineNewlyAckedPackets(ackFrame, encLevel)
if err != nil {
return err
}
if len(ackedPackets) == 0 {
return nil
}
priorInFlight := h.bytesInFlight
for _, p := range ackedPackets {
if p.largestAcked != protocol.InvalidPacketNumber && encLevel == protocol.Encryption1RTT {
h.lowestNotConfirmedAcked = utils.MaxPacketNumber(h.lowestNotConfirmedAcked, p.largestAcked+1)
}
if err := h.onPacketAcked(p, rcvTime); err != nil {
return err
}
if p.includedInBytesInFlight {
h.congestion.OnPacketAcked(p.PacketNumber, p.Length, priorInFlight, rcvTime)
}
}
if err := h.detectLostPackets(rcvTime, encLevel, priorInFlight); err != nil {
return err
}
h.ptoCount = 0
h.numProbesToSend = 0
h.setLossDetectionTimer()
return nil
}
func (h *sentPacketHandler) GetLowestPacketNotConfirmedAcked() protocol.PacketNumber {
return h.lowestNotConfirmedAcked
}
func (h *sentPacketHandler) determineNewlyAckedPackets(
ackFrame *wire.AckFrame,
encLevel protocol.EncryptionLevel,
) ([]*Packet, error) {
pnSpace := h.getPacketNumberSpace(encLevel)
var ackedPackets []*Packet
ackRangeIndex := 0
lowestAcked := ackFrame.LowestAcked()
largestAcked := ackFrame.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 ackFrame.HasMissingRanges() {
ackRange := ackFrame.AckRanges[len(ackFrame.AckRanges)-1-ackRangeIndex]
for p.PacketNumber > ackRange.Largest && ackRangeIndex < len(ackFrame.AckRanges)-1 {
ackRangeIndex++
ackRange = ackFrame.AckRanges[len(ackFrame.AckRanges)-1-ackRangeIndex]
}
if p.PacketNumber >= ackRange.Smallest { // packet i contained in ACK range
if p.PacketNumber > ackRange.Largest {
return false, fmt.Errorf("BUG: ackhandler would have acked wrong packet 0x%x, while evaluating range 0x%x -> 0x%x", p.PacketNumber, ackRange.Smallest, ackRange.Largest)
}
ackedPackets = append(ackedPackets, p)
}
} else {
ackedPackets = append(ackedPackets, p)
}
return true, nil
})
if h.logger.Debug() && len(ackedPackets) > 0 {
pns := make([]protocol.PacketNumber, len(ackedPackets))
for i, p := range ackedPackets {
pns[i] = p.PacketNumber
}
h.logger.Debugf("\tnewly acked packets (%d): %#x", len(pns), pns)
}
return ackedPackets, err
}
func (h *sentPacketHandler) getEarliestLossTime() (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.oneRTTPackets.lossTime.IsZero() && h.oneRTTPackets.lossTime.Before(lossTime)) {
lossTime = h.oneRTTPackets.lossTime
encLevel = protocol.Encryption1RTT
}
return lossTime, encLevel
}
func (h *sentPacketHandler) hasOutstandingCryptoPackets() bool {
var hasInitial, hasHandshake bool
if h.initialPackets != nil {
hasInitial = h.initialPackets.history.HasOutstandingPackets()
}
if h.handshakePackets != nil {
hasHandshake = h.handshakePackets.history.HasOutstandingPackets()
}
return hasInitial || hasHandshake
}
func (h *sentPacketHandler) hasOutstandingPackets() bool {
return h.oneRTTPackets.history.HasOutstandingPackets() || h.hasOutstandingCryptoPackets()
}
func (h *sentPacketHandler) setLossDetectionTimer() {
if lossTime, _ := h.getEarliestLossTime(); !lossTime.IsZero() {
// Early retransmit timer or time loss detection.
h.alarm = lossTime
}
// Cancel the alarm if no packets are outstanding
if !h.hasOutstandingPackets() {
h.alarm = time.Time{}
return
}
// PTO alarm
h.alarm = h.lastSentAckElicitingPacketTime.Add(h.rttStats.PTO() << h.ptoCount)
}
func (h *sentPacketHandler) detectLostPackets(
now time.Time,
encLevel protocol.EncryptionLevel,
priorInFlight protocol.ByteCount,
) error {
pnSpace := h.getPacketNumberSpace(encLevel)
pnSpace.lossTime = time.Time{}
maxRTT := float64(utils.MaxDuration(h.rttStats.LatestRTT(), h.rttStats.SmoothedRTT()))
lossDelay := time.Duration(timeThreshold * maxRTT)
// Minimum time of granularity before packets are deemed lost.
lossDelay = utils.MaxDuration(lossDelay, protocol.TimerGranularity)
// Packets sent before this time are deemed lost.
lostSendTime := now.Add(-lossDelay)
var lostPackets []*Packet
pnSpace.history.Iterate(func(packet *Packet) (bool, error) {
if packet.PacketNumber > pnSpace.largestAcked {
return false, nil
}
if packet.SendTime.Before(lostSendTime) || pnSpace.largestAcked >= packet.PacketNumber+packetThreshold {
lostPackets = append(lostPackets, packet)
} else if pnSpace.lossTime.IsZero() {
// Note: This conditional is only entered once per call
lossTime := packet.SendTime.Add(lossDelay)
if h.logger.Debug() {
h.logger.Debugf("\tsetting loss timer for packet %#x (%s) to %s (in %s)", packet.PacketNumber, encLevel, lossDelay, lossTime)
}
pnSpace.lossTime = lossTime
}
return true, nil
})
if h.logger.Debug() && len(lostPackets) > 0 {
pns := make([]protocol.PacketNumber, len(lostPackets))
for i, p := range lostPackets {
pns[i] = p.PacketNumber
}
h.logger.Debugf("\tlost packets (%d): %#x", len(pns), pns)
}
for _, p := range lostPackets {
// the bytes in flight need to be reduced no matter if this packet will be retransmitted
if p.includedInBytesInFlight {
h.bytesInFlight -= p.Length
h.congestion.OnPacketLost(p.PacketNumber, p.Length, priorInFlight)
}
if p.canBeRetransmitted {
// queue the packet for retransmission, and report the loss to the congestion controller
if err := h.queuePacketForRetransmission(p, pnSpace); err != nil {
return err
}
}
pnSpace.history.Remove(p.PacketNumber)
if h.traceCallback != nil {
h.traceCallback(quictrace.Event{
Time: now,
EventType: quictrace.PacketLost,
EncryptionLevel: p.EncryptionLevel,
PacketNumber: p.PacketNumber,
PacketSize: p.Length,
Frames: p.Frames,
TransportState: h.GetStats(),
})
}
}
return nil
}
func (h *sentPacketHandler) OnLossDetectionTimeout() error {
// When all outstanding are acknowledged, the alarm is canceled in
// updateLossDetectionAlarm. 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.hasOutstandingPackets() {
if err := h.onVerifiedLossDetectionTimeout(); err != nil {
return err
}
}
h.setLossDetectionTimer()
return nil
}
func (h *sentPacketHandler) onVerifiedLossDetectionTimeout() error {
lossTime, encLevel := h.getEarliestLossTime()
if !lossTime.IsZero() {
if h.logger.Debug() {
h.logger.Debugf("Loss detection alarm fired in loss timer mode. Loss time: %s", lossTime)
}
// Early retransmit or time loss detection
return h.detectLostPackets(time.Now(), encLevel, h.bytesInFlight)
}
// PTO
if h.logger.Debug() {
h.logger.Debugf("Loss detection alarm fired in PTO mode. PTO count: %d", h.ptoCount)
}
h.ptoCount++
h.numProbesToSend += 2
return nil
}
func (h *sentPacketHandler) GetLossDetectionTimeout() time.Time {
return h.alarm
}
func (h *sentPacketHandler) onPacketAcked(p *Packet, rcvTime time.Time) error {
pnSpace := h.getPacketNumberSpace(p.EncryptionLevel)
// This happens if a packet and its retransmissions is acked in the same ACK.
// As soon as we process the first one, this will remove all the retransmissions,
// so we won't find the retransmitted packet number later.
if packet := pnSpace.history.GetPacket(p.PacketNumber); packet == nil {
return nil
}
// only report the acking of this packet to the congestion controller if:
// * it is an ack-eliciting packet
// * this packet wasn't retransmitted yet
if p.isRetransmission {
// that the parent doesn't exist is expected to happen every time the original packet was already acked
if parent := pnSpace.history.GetPacket(p.retransmissionOf); parent != nil {
if len(parent.retransmittedAs) == 1 {
parent.retransmittedAs = nil
} else {
// remove this packet from the slice of retransmission
retransmittedAs := make([]protocol.PacketNumber, 0, len(parent.retransmittedAs)-1)
for _, pn := range parent.retransmittedAs {
if pn != p.PacketNumber {
retransmittedAs = append(retransmittedAs, pn)
}
}
parent.retransmittedAs = retransmittedAs
}
}
}
// this also applies to packets that have been retransmitted as probe packets
if p.includedInBytesInFlight {
h.bytesInFlight -= p.Length
}
if err := h.stopRetransmissionsFor(p, pnSpace); err != nil {
return err
}
return pnSpace.history.Remove(p.PacketNumber)
}
func (h *sentPacketHandler) stopRetransmissionsFor(p *Packet, pnSpace *packetNumberSpace) error {
if err := pnSpace.history.MarkCannotBeRetransmitted(p.PacketNumber); err != nil {
return err
}
for _, r := range p.retransmittedAs {
packet := pnSpace.history.GetPacket(r)
if packet == nil {
return fmt.Errorf("sent packet handler BUG: marking packet as not retransmittable %d (retransmission of %d) not found in history", r, p.PacketNumber)
}
h.stopRetransmissionsFor(packet, pnSpace)
}
return nil
}
func (h *sentPacketHandler) DequeuePacketForRetransmission() *Packet {
if len(h.retransmissionQueue) == 0 {
return nil
}
packet := h.retransmissionQueue[0]
// Shift the slice and don't retain anything that isn't needed.
copy(h.retransmissionQueue, h.retransmissionQueue[1:])
h.retransmissionQueue[len(h.retransmissionQueue)-1] = nil
h.retransmissionQueue = h.retransmissionQueue[:len(h.retransmissionQueue)-1]
return packet
}
func (h *sentPacketHandler) DequeueProbePacket() (*Packet, error) {
if len(h.retransmissionQueue) > 0 {
return h.DequeuePacketForRetransmission(), nil
}
var pnSpace *packetNumberSpace
var p *Packet
if h.initialPackets != nil {
pnSpace = h.initialPackets
p = h.initialPackets.history.FirstOutstanding()
}
if p == nil && h.handshakePackets != nil {
pnSpace = h.handshakePackets
p = h.handshakePackets.history.FirstOutstanding()
}
if p == nil {
pnSpace = h.oneRTTPackets
p = h.oneRTTPackets.history.FirstOutstanding()
}
if p == nil {
return nil, errors.New("cannot dequeue a probe packet. No outstanding packets")
}
if err := h.queuePacketForRetransmission(p, pnSpace); err != nil {
return nil, err
}
return h.DequeuePacketForRetransmission(), nil
}
func (h *sentPacketHandler) PeekPacketNumber(encLevel protocol.EncryptionLevel) (protocol.PacketNumber, protocol.PacketNumberLen) {
pnSpace := h.getPacketNumberSpace(encLevel)
var lowestUnacked protocol.PacketNumber
if p := pnSpace.history.FirstOutstanding(); p != nil {
lowestUnacked = p.PacketNumber
} else {
lowestUnacked = pnSpace.largestAcked + 1
}
pn := pnSpace.pns.Peek()
return pn, protocol.GetPacketNumberLengthForHeader(pn, lowestUnacked)
}
func (h *sentPacketHandler) PopPacketNumber(encLevel protocol.EncryptionLevel) protocol.PacketNumber {
return h.getPacketNumberSpace(encLevel).pns.Pop()
}
func (h *sentPacketHandler) SendMode() SendMode {
numTrackedPackets := len(h.retransmissionQueue) + h.oneRTTPackets.history.Len()
if h.initialPackets != nil {
numTrackedPackets += h.initialPackets.history.Len()
}
if h.handshakePackets != nil {
numTrackedPackets += h.handshakePackets.history.Len()
}
// 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 SendPTO
}
// 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
}
// Send retransmissions first, if there are any.
if len(h.retransmissionQueue) > 0 {
return SendRetransmission
}
if numTrackedPackets >= protocol.MaxOutstandingSentPackets {
if h.logger.Debug() {
h.logger.Debugf("Max outstanding limited: tracking %d packets, maximum: %d", numTrackedPackets, protocol.MaxOutstandingSentPackets)
}
return SendAck
}
return SendAny
}
func (h *sentPacketHandler) TimeUntilSend() time.Time {
return h.nextSendTime
}
func (h *sentPacketHandler) ShouldSendNumPackets() int {
if h.numProbesToSend > 0 {
// RTO probes should not be paced, but must be sent immediately.
return h.numProbesToSend
}
delay := h.congestion.TimeUntilSend(h.bytesInFlight)
if delay == 0 || delay > protocol.MinPacingDelay {
return 1
}
return int(math.Ceil(float64(protocol.MinPacingDelay) / float64(delay)))
}
func (h *sentPacketHandler) queuePacketForRetransmission(p *Packet, pnSpace *packetNumberSpace) error {
if !p.canBeRetransmitted {
return fmt.Errorf("sent packet handler BUG: packet %d already queued for retransmission", p.PacketNumber)
}
if err := pnSpace.history.MarkCannotBeRetransmitted(p.PacketNumber); err != nil {
return err
}
h.retransmissionQueue = append(h.retransmissionQueue, p)
return nil
}
func (h *sentPacketHandler) ResetForRetry() error {
h.bytesInFlight = 0
var packets []*Packet
h.initialPackets.history.Iterate(func(p *Packet) (bool, error) {
if p.canBeRetransmitted {
packets = append(packets, p)
}
return true, nil
})
for _, p := range packets {
h.logger.Debugf("Queueing packet %#x for retransmission.", p.PacketNumber)
h.retransmissionQueue = append(h.retransmissionQueue, p)
}
h.initialPackets = newPacketNumberSpace(h.initialPackets.pns.Pop())
h.setLossDetectionTimer()
return nil
}
func (h *sentPacketHandler) GetStats() *quictrace.TransportState {
return &quictrace.TransportState{
MinRTT: h.rttStats.MinRTT(),
SmoothedRTT: h.rttStats.SmoothedRTT(),
LatestRTT: h.rttStats.LatestRTT(),
BytesInFlight: h.bytesInFlight,
CongestionWindow: h.congestion.GetCongestionWindow(),
InSlowStart: h.congestion.InSlowStart(),
InRecovery: h.congestion.InRecovery(),
}
}