TUN-4597: Add a QUIC server skeleton

- Added a QUIC server to accept streams
- Unit test for this server also tests ALPN
- Temporary echo capability for HTTP ConnectionType

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/ack_eliciting.go

@@ -0,0 +1,20 @@
+package ackhandler
+
+import "github.com/lucas-clemente/quic-go/internal/wire"
+
+// IsFrameAckEliciting returns true if the frame is ack-eliciting.
+func IsFrameAckEliciting(f wire.Frame) bool {
+	_, isAck := f.(*wire.AckFrame)
+	_, isConnectionClose := f.(*wire.ConnectionCloseFrame)
+	return !isAck && !isConnectionClose
+}
+
+// HasAckElicitingFrames returns true if at least one frame is ack-eliciting.
+func HasAckElicitingFrames(fs []Frame) bool {
+	for _, f := range fs {
+		if IsFrameAckEliciting(f.Frame) {
+			return true
+		}
+	}
+	return false
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/ackhandler.go

@@ -0,0 +1,21 @@
+package ackhandler
+
+import (
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+	"github.com/lucas-clemente/quic-go/logging"
+)
+
+// NewAckHandler creates a new SentPacketHandler and a new ReceivedPacketHandler
+func NewAckHandler(
+	initialPacketNumber protocol.PacketNumber,
+	initialMaxDatagramSize protocol.ByteCount,
+	rttStats *utils.RTTStats,
+	pers protocol.Perspective,
+	tracer logging.ConnectionTracer,
+	logger utils.Logger,
+	version protocol.VersionNumber,
+) (SentPacketHandler, ReceivedPacketHandler) {
+	sph := newSentPacketHandler(initialPacketNumber, initialMaxDatagramSize, rttStats, pers, tracer, logger)
+	return sph, newReceivedPacketHandler(sph, rttStats, logger, version)
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/frame.go

@@ -0,0 +1,9 @@
+package ackhandler
+
+import "github.com/lucas-clemente/quic-go/internal/wire"
+
+type Frame struct {
+	wire.Frame // nil if the frame has already been acknowledged in another packet
+	OnLost     func(wire.Frame)
+	OnAcked    func(wire.Frame)
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/gen.go

@@ -0,0 +1,3 @@
+package ackhandler
+
+//go:generate genny -pkg ackhandler -in ../utils/linkedlist/linkedlist.go -out packet_linkedlist.go gen Item=Packet

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/interfaces.go

@@ -0,0 +1,68 @@
+package ackhandler
+
+import (
+	"time"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/wire"
+)
+
+// A Packet is a packet
+type Packet struct {
+	PacketNumber    protocol.PacketNumber
+	Frames          []Frame
+	LargestAcked    protocol.PacketNumber // InvalidPacketNumber if the packet doesn't contain an ACK
+	Length          protocol.ByteCount
+	EncryptionLevel protocol.EncryptionLevel
+	SendTime        time.Time
+
+	IsPathMTUProbePacket bool // We don't report the loss of Path MTU probe packets to the congestion controller.
+
+	includedInBytesInFlight bool
+	declaredLost            bool
+	skippedPacket           bool
+}
+
+// SentPacketHandler handles ACKs received for outgoing packets
+type SentPacketHandler interface {
+	// SentPacket may modify the packet
+	SentPacket(packet *Packet)
+	ReceivedAck(ackFrame *wire.AckFrame, encLevel protocol.EncryptionLevel, recvTime time.Time) (bool /* 1-RTT packet acked */, error)
+	ReceivedBytes(protocol.ByteCount)
+	DropPackets(protocol.EncryptionLevel)
+	ResetForRetry() error
+	SetHandshakeConfirmed()
+
+	// The SendMode determines if and what kind of packets can be sent.
+	SendMode() SendMode
+	// TimeUntilSend is the time when the next packet should be sent.
+	// It is used for pacing packets.
+	TimeUntilSend() time.Time
+	// HasPacingBudget says if the pacer allows sending of a (full size) packet at this moment.
+	HasPacingBudget() bool
+	SetMaxDatagramSize(count protocol.ByteCount)
+
+	// only to be called once the handshake is complete
+	QueueProbePacket(protocol.EncryptionLevel) bool /* was a packet queued */
+
+	PeekPacketNumber(protocol.EncryptionLevel) (protocol.PacketNumber, protocol.PacketNumberLen)
+	PopPacketNumber(protocol.EncryptionLevel) protocol.PacketNumber
+
+	GetLossDetectionTimeout() time.Time
+	OnLossDetectionTimeout() error
+}
+
+type sentPacketTracker interface {
+	GetLowestPacketNotConfirmedAcked() protocol.PacketNumber
+	ReceivedPacket(protocol.EncryptionLevel)
+}
+
+// ReceivedPacketHandler handles ACKs needed to send for incoming packets
+type ReceivedPacketHandler interface {
+	IsPotentiallyDuplicate(protocol.PacketNumber, protocol.EncryptionLevel) bool
+	ReceivedPacket(pn protocol.PacketNumber, ecn protocol.ECN, encLevel protocol.EncryptionLevel, rcvTime time.Time, shouldInstigateAck bool) error
+	DropPackets(protocol.EncryptionLevel)
+
+	GetAlarmTimeout() time.Time
+	GetAckFrame(encLevel protocol.EncryptionLevel, onlyIfQueued bool) *wire.AckFrame
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/mockgen.go

@@ -0,0 +1,3 @@
+package ackhandler
+
+//go:generate sh -c "../../mockgen_private.sh ackhandler mock_sent_packet_tracker_test.go github.com/lucas-clemente/quic-go/internal/ackhandler sentPacketTracker"

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/packet_linkedlist.go

@@ -0,0 +1,217 @@
+// This file was automatically generated by genny.
+// Any changes will be lost if this file is regenerated.
+// see https://github.com/cheekybits/genny
+
+package ackhandler
+
+// Linked list implementation from the Go standard library.
+
+// PacketElement is an element of a linked list.
+type PacketElement struct {
+	// Next and previous pointers in the doubly-linked list of elements.
+	// To simplify the implementation, internally a list l is implemented
+	// as a ring, such that &l.root is both the next element of the last
+	// list element (l.Back()) and the previous element of the first list
+	// element (l.Front()).
+	next, prev *PacketElement
+
+	// The list to which this element belongs.
+	list *PacketList
+
+	// The value stored with this element.
+	Value Packet
+}
+
+// Next returns the next list element or nil.
+func (e *PacketElement) Next() *PacketElement {
+	if p := e.next; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+// Prev returns the previous list element or nil.
+func (e *PacketElement) Prev() *PacketElement {
+	if p := e.prev; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+// PacketList is a linked list of Packets.
+type PacketList struct {
+	root PacketElement // sentinel list element, only &root, root.prev, and root.next are used
+	len  int           // current list length excluding (this) sentinel element
+}
+
+// Init initializes or clears list l.
+func (l *PacketList) Init() *PacketList {
+	l.root.next = &l.root
+	l.root.prev = &l.root
+	l.len = 0
+	return l
+}
+
+// NewPacketList returns an initialized list.
+func NewPacketList() *PacketList { return new(PacketList).Init() }
+
+// Len returns the number of elements of list l.
+// The complexity is O(1).
+func (l *PacketList) Len() int { return l.len }
+
+// Front returns the first element of list l or nil if the list is empty.
+func (l *PacketList) Front() *PacketElement {
+	if l.len == 0 {
+		return nil
+	}
+	return l.root.next
+}
+
+// Back returns the last element of list l or nil if the list is empty.
+func (l *PacketList) Back() *PacketElement {
+	if l.len == 0 {
+		return nil
+	}
+	return l.root.prev
+}
+
+// lazyInit lazily initializes a zero List value.
+func (l *PacketList) lazyInit() {
+	if l.root.next == nil {
+		l.Init()
+	}
+}
+
+// insert inserts e after at, increments l.len, and returns e.
+func (l *PacketList) insert(e, at *PacketElement) *PacketElement {
+	n := at.next
+	at.next = e
+	e.prev = at
+	e.next = n
+	n.prev = e
+	e.list = l
+	l.len++
+	return e
+}
+
+// insertValue is a convenience wrapper for insert(&Element{Value: v}, at).
+func (l *PacketList) insertValue(v Packet, at *PacketElement) *PacketElement {
+	return l.insert(&PacketElement{Value: v}, at)
+}
+
+// remove removes e from its list, decrements l.len, and returns e.
+func (l *PacketList) remove(e *PacketElement) *PacketElement {
+	e.prev.next = e.next
+	e.next.prev = e.prev
+	e.next = nil // avoid memory leaks
+	e.prev = nil // avoid memory leaks
+	e.list = nil
+	l.len--
+	return e
+}
+
+// Remove removes e from l if e is an element of list l.
+// It returns the element value e.Value.
+// The element must not be nil.
+func (l *PacketList) Remove(e *PacketElement) Packet {
+	if e.list == l {
+		// if e.list == l, l must have been initialized when e was inserted
+		// in l or l == nil (e is a zero Element) and l.remove will crash
+		l.remove(e)
+	}
+	return e.Value
+}
+
+// PushFront inserts a new element e with value v at the front of list l and returns e.
+func (l *PacketList) PushFront(v Packet) *PacketElement {
+	l.lazyInit()
+	return l.insertValue(v, &l.root)
+}
+
+// PushBack inserts a new element e with value v at the back of list l and returns e.
+func (l *PacketList) PushBack(v Packet) *PacketElement {
+	l.lazyInit()
+	return l.insertValue(v, l.root.prev)
+}
+
+// InsertBefore inserts a new element e with value v immediately before mark and returns e.
+// If mark is not an element of l, the list is not modified.
+// The mark must not be nil.
+func (l *PacketList) InsertBefore(v Packet, mark *PacketElement) *PacketElement {
+	if mark.list != l {
+		return nil
+	}
+	// see comment in List.Remove about initialization of l
+	return l.insertValue(v, mark.prev)
+}
+
+// InsertAfter inserts a new element e with value v immediately after mark and returns e.
+// If mark is not an element of l, the list is not modified.
+// The mark must not be nil.
+func (l *PacketList) InsertAfter(v Packet, mark *PacketElement) *PacketElement {
+	if mark.list != l {
+		return nil
+	}
+	// see comment in List.Remove about initialization of l
+	return l.insertValue(v, mark)
+}
+
+// MoveToFront moves element e to the front of list l.
+// If e is not an element of l, the list is not modified.
+// The element must not be nil.
+func (l *PacketList) MoveToFront(e *PacketElement) {
+	if e.list != l || l.root.next == e {
+		return
+	}
+	// see comment in List.Remove about initialization of l
+	l.insert(l.remove(e), &l.root)
+}
+
+// MoveToBack moves element e to the back of list l.
+// If e is not an element of l, the list is not modified.
+// The element must not be nil.
+func (l *PacketList) MoveToBack(e *PacketElement) {
+	if e.list != l || l.root.prev == e {
+		return
+	}
+	// see comment in List.Remove about initialization of l
+	l.insert(l.remove(e), l.root.prev)
+}
+
+// MoveBefore moves element e to its new position before mark.
+// If e or mark is not an element of l, or e == mark, the list is not modified.
+// The element and mark must not be nil.
+func (l *PacketList) MoveBefore(e, mark *PacketElement) {
+	if e.list != l || e == mark || mark.list != l {
+		return
+	}
+	l.insert(l.remove(e), mark.prev)
+}
+
+// MoveAfter moves element e to its new position after mark.
+// If e or mark is not an element of l, or e == mark, the list is not modified.
+// The element and mark must not be nil.
+func (l *PacketList) MoveAfter(e, mark *PacketElement) {
+	if e.list != l || e == mark || mark.list != l {
+		return
+	}
+	l.insert(l.remove(e), mark)
+}
+
+// PushBackList inserts a copy of an other list at the back of list l.
+// The lists l and other may be the same. They must not be nil.
+func (l *PacketList) PushBackList(other *PacketList) {
+	l.lazyInit()
+	for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
+		l.insertValue(e.Value, l.root.prev)
+	}
+}
+
+// PushFrontList inserts a copy of an other list at the front of list l.
+// The lists l and other may be the same. They must not be nil.
+func (l *PacketList) PushFrontList(other *PacketList) {
+	l.lazyInit()
+	for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
+		l.insertValue(e.Value, &l.root)
+	}
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/packet_number_generator.go

@@ -0,0 +1,76 @@
+package ackhandler
+
+import (
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+)
+
+type packetNumberGenerator interface {
+	Peek() protocol.PacketNumber
+	Pop() protocol.PacketNumber
+}
+
+type sequentialPacketNumberGenerator struct {
+	next protocol.PacketNumber
+}
+
+var _ packetNumberGenerator = &sequentialPacketNumberGenerator{}
+
+func newSequentialPacketNumberGenerator(initial protocol.PacketNumber) packetNumberGenerator {
+	return &sequentialPacketNumberGenerator{next: initial}
+}
+
+func (p *sequentialPacketNumberGenerator) Peek() protocol.PacketNumber {
+	return p.next
+}
+
+func (p *sequentialPacketNumberGenerator) Pop() protocol.PacketNumber {
+	next := p.next
+	p.next++
+	return next
+}
+
+// The skippingPacketNumberGenerator generates the packet number for the next packet
+// it randomly skips a packet number every averagePeriod packets (on average).
+// It is guaranteed to never skip two consecutive packet numbers.
+type skippingPacketNumberGenerator struct {
+	period    protocol.PacketNumber
+	maxPeriod protocol.PacketNumber
+
+	next       protocol.PacketNumber
+	nextToSkip protocol.PacketNumber
+
+	rng utils.Rand
+}
+
+var _ packetNumberGenerator = &skippingPacketNumberGenerator{}
+
+func newSkippingPacketNumberGenerator(initial, initialPeriod, maxPeriod protocol.PacketNumber) packetNumberGenerator {
+	g := &skippingPacketNumberGenerator{
+		next:      initial,
+		period:    initialPeriod,
+		maxPeriod: maxPeriod,
+	}
+	g.generateNewSkip()
+	return g
+}
+
+func (p *skippingPacketNumberGenerator) Peek() protocol.PacketNumber {
+	return p.next
+}
+
+func (p *skippingPacketNumberGenerator) Pop() protocol.PacketNumber {
+	next := p.next
+	p.next++ // generate a new packet number for the next packet
+	if p.next == p.nextToSkip {
+		p.next++
+		p.generateNewSkip()
+	}
+	return next
+}
+
+func (p *skippingPacketNumberGenerator) generateNewSkip() {
+	// make sure that there are never two consecutive packet numbers that are skipped
+	p.nextToSkip = p.next + 2 + protocol.PacketNumber(p.rng.Int31n(int32(2*p.period)))
+	p.period = utils.MinPacketNumber(2*p.period, p.maxPeriod)
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/received_packet_handler.go

@@ -0,0 +1,136 @@
+package ackhandler
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+	"github.com/lucas-clemente/quic-go/internal/wire"
+)
+
+type receivedPacketHandler struct {
+	sentPackets sentPacketTracker
+
+	initialPackets   *receivedPacketTracker
+	handshakePackets *receivedPacketTracker
+	appDataPackets   *receivedPacketTracker
+
+	lowest1RTTPacket protocol.PacketNumber
+}
+
+var _ ReceivedPacketHandler = &receivedPacketHandler{}
+
+func newReceivedPacketHandler(
+	sentPackets sentPacketTracker,
+	rttStats *utils.RTTStats,
+	logger utils.Logger,
+	version protocol.VersionNumber,
+) ReceivedPacketHandler {
+	return &receivedPacketHandler{
+		sentPackets:      sentPackets,
+		initialPackets:   newReceivedPacketTracker(rttStats, logger, version),
+		handshakePackets: newReceivedPacketTracker(rttStats, logger, version),
+		appDataPackets:   newReceivedPacketTracker(rttStats, logger, version),
+		lowest1RTTPacket: protocol.InvalidPacketNumber,
+	}
+}
+
+func (h *receivedPacketHandler) ReceivedPacket(
+	pn protocol.PacketNumber,
+	ecn protocol.ECN,
+	encLevel protocol.EncryptionLevel,
+	rcvTime time.Time,
+	shouldInstigateAck bool,
+) error {
+	h.sentPackets.ReceivedPacket(encLevel)
+	switch encLevel {
+	case protocol.EncryptionInitial:
+		h.initialPackets.ReceivedPacket(pn, ecn, rcvTime, shouldInstigateAck)
+	case protocol.EncryptionHandshake:
+		h.handshakePackets.ReceivedPacket(pn, ecn, rcvTime, shouldInstigateAck)
+	case protocol.Encryption0RTT:
+		if h.lowest1RTTPacket != protocol.InvalidPacketNumber && pn > h.lowest1RTTPacket {
+			return fmt.Errorf("received packet number %d on a 0-RTT packet after receiving %d on a 1-RTT packet", pn, h.lowest1RTTPacket)
+		}
+		h.appDataPackets.ReceivedPacket(pn, ecn, rcvTime, shouldInstigateAck)
+	case protocol.Encryption1RTT:
+		if h.lowest1RTTPacket == protocol.InvalidPacketNumber || pn < h.lowest1RTTPacket {
+			h.lowest1RTTPacket = pn
+		}
+		h.appDataPackets.IgnoreBelow(h.sentPackets.GetLowestPacketNotConfirmedAcked())
+		h.appDataPackets.ReceivedPacket(pn, ecn, rcvTime, shouldInstigateAck)
+	default:
+		panic(fmt.Sprintf("received packet with unknown encryption level: %s", encLevel))
+	}
+	return nil
+}
+
+func (h *receivedPacketHandler) DropPackets(encLevel protocol.EncryptionLevel) {
+	//nolint:exhaustive // 1-RTT packet number space is never dropped.
+	switch encLevel {
+	case protocol.EncryptionInitial:
+		h.initialPackets = nil
+	case protocol.EncryptionHandshake:
+		h.handshakePackets = nil
+	case protocol.Encryption0RTT:
+		// Nothing to do here.
+		// If we are rejecting 0-RTT, no 0-RTT packets will have been decrypted.
+	default:
+		panic(fmt.Sprintf("Cannot drop keys for encryption level %s", encLevel))
+	}
+}
+
+func (h *receivedPacketHandler) GetAlarmTimeout() time.Time {
+	var initialAlarm, handshakeAlarm time.Time
+	if h.initialPackets != nil {
+		initialAlarm = h.initialPackets.GetAlarmTimeout()
+	}
+	if h.handshakePackets != nil {
+		handshakeAlarm = h.handshakePackets.GetAlarmTimeout()
+	}
+	oneRTTAlarm := h.appDataPackets.GetAlarmTimeout()
+	return utils.MinNonZeroTime(utils.MinNonZeroTime(initialAlarm, handshakeAlarm), oneRTTAlarm)
+}
+
+func (h *receivedPacketHandler) GetAckFrame(encLevel protocol.EncryptionLevel, onlyIfQueued bool) *wire.AckFrame {
+	var ack *wire.AckFrame
+	//nolint:exhaustive // 0-RTT packets can't contain ACK frames.
+	switch encLevel {
+	case protocol.EncryptionInitial:
+		if h.initialPackets != nil {
+			ack = h.initialPackets.GetAckFrame(onlyIfQueued)
+		}
+	case protocol.EncryptionHandshake:
+		if h.handshakePackets != nil {
+			ack = h.handshakePackets.GetAckFrame(onlyIfQueued)
+		}
+	case protocol.Encryption1RTT:
+		// 0-RTT packets can't contain ACK frames
+		return h.appDataPackets.GetAckFrame(onlyIfQueued)
+	default:
+		return nil
+	}
+	// For Initial and Handshake ACKs, the delay time is ignored by the receiver.
+	// Set it to 0 in order to save bytes.
+	if ack != nil {
+		ack.DelayTime = 0
+	}
+	return ack
+}
+
+func (h *receivedPacketHandler) IsPotentiallyDuplicate(pn protocol.PacketNumber, encLevel protocol.EncryptionLevel) bool {
+	switch encLevel {
+	case protocol.EncryptionInitial:
+		if h.initialPackets != nil {
+			return h.initialPackets.IsPotentiallyDuplicate(pn)
+		}
+	case protocol.EncryptionHandshake:
+		if h.handshakePackets != nil {
+			return h.handshakePackets.IsPotentiallyDuplicate(pn)
+		}
+	case protocol.Encryption0RTT, protocol.Encryption1RTT:
+		return h.appDataPackets.IsPotentiallyDuplicate(pn)
+	}
+	panic("unexpected encryption level")
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/received_packet_history.go

@@ -0,0 +1,142 @@
+package ackhandler
+
+import (
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+	"github.com/lucas-clemente/quic-go/internal/wire"
+)
+
+// The receivedPacketHistory stores if a packet number has already been received.
+// It generates ACK ranges which can be used to assemble an ACK frame.
+// It does not store packet contents.
+type receivedPacketHistory struct {
+	ranges *utils.PacketIntervalList
+
+	deletedBelow protocol.PacketNumber
+}
+
+func newReceivedPacketHistory() *receivedPacketHistory {
+	return &receivedPacketHistory{
+		ranges: utils.NewPacketIntervalList(),
+	}
+}
+
+// ReceivedPacket registers a packet with PacketNumber p and updates the ranges
+func (h *receivedPacketHistory) ReceivedPacket(p protocol.PacketNumber) bool /* is a new packet (and not a duplicate / delayed packet) */ {
+	// ignore delayed packets, if we already deleted the range
+	if p < h.deletedBelow {
+		return false
+	}
+	isNew := h.addToRanges(p)
+	h.maybeDeleteOldRanges()
+	return isNew
+}
+
+func (h *receivedPacketHistory) addToRanges(p protocol.PacketNumber) bool /* is a new packet (and not a duplicate / delayed packet) */ {
+	if h.ranges.Len() == 0 {
+		h.ranges.PushBack(utils.PacketInterval{Start: p, End: p})
+		return true
+	}
+
+	for el := h.ranges.Back(); el != nil; el = el.Prev() {
+		// p already included in an existing range. Nothing to do here
+		if p >= el.Value.Start && p <= el.Value.End {
+			return false
+		}
+
+		if el.Value.End == p-1 { // extend a range at the end
+			el.Value.End = p
+			return true
+		}
+		if el.Value.Start == p+1 { // extend a range at the beginning
+			el.Value.Start = p
+
+			prev := el.Prev()
+			if prev != nil && prev.Value.End+1 == el.Value.Start { // merge two ranges
+				prev.Value.End = el.Value.End
+				h.ranges.Remove(el)
+			}
+			return true
+		}
+
+		// create a new range at the end
+		if p > el.Value.End {
+			h.ranges.InsertAfter(utils.PacketInterval{Start: p, End: p}, el)
+			return true
+		}
+	}
+
+	// create a new range at the beginning
+	h.ranges.InsertBefore(utils.PacketInterval{Start: p, End: p}, h.ranges.Front())
+	return true
+}
+
+// Delete old ranges, if we're tracking more than 500 of them.
+// This is a DoS defense against a peer that sends us too many gaps.
+func (h *receivedPacketHistory) maybeDeleteOldRanges() {
+	for h.ranges.Len() > protocol.MaxNumAckRanges {
+		h.ranges.Remove(h.ranges.Front())
+	}
+}
+
+// DeleteBelow deletes all entries below (but not including) p
+func (h *receivedPacketHistory) DeleteBelow(p protocol.PacketNumber) {
+	if p < h.deletedBelow {
+		return
+	}
+	h.deletedBelow = p
+
+	nextEl := h.ranges.Front()
+	for el := h.ranges.Front(); nextEl != nil; el = nextEl {
+		nextEl = el.Next()
+
+		if el.Value.End < p { // delete a whole range
+			h.ranges.Remove(el)
+		} else if p > el.Value.Start && p <= el.Value.End {
+			el.Value.Start = p
+			return
+		} else { // no ranges affected. Nothing to do
+			return
+		}
+	}
+}
+
+// GetAckRanges gets a slice of all AckRanges that can be used in an AckFrame
+func (h *receivedPacketHistory) GetAckRanges() []wire.AckRange {
+	if h.ranges.Len() == 0 {
+		return nil
+	}
+
+	ackRanges := make([]wire.AckRange, h.ranges.Len())
+	i := 0
+	for el := h.ranges.Back(); el != nil; el = el.Prev() {
+		ackRanges[i] = wire.AckRange{Smallest: el.Value.Start, Largest: el.Value.End}
+		i++
+	}
+	return ackRanges
+}
+
+func (h *receivedPacketHistory) GetHighestAckRange() wire.AckRange {
+	ackRange := wire.AckRange{}
+	if h.ranges.Len() > 0 {
+		r := h.ranges.Back().Value
+		ackRange.Smallest = r.Start
+		ackRange.Largest = r.End
+	}
+	return ackRange
+}
+
+func (h *receivedPacketHistory) IsPotentiallyDuplicate(p protocol.PacketNumber) bool {
+	if p < h.deletedBelow {
+		return true
+	}
+	for el := h.ranges.Back(); el != nil; el = el.Prev() {
+		if p > el.Value.End {
+			return false
+		}
+		if p <= el.Value.End && p >= el.Value.Start {
+			return true
+		}
+	}
+	return false
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/received_packet_tracker.go

@@ -0,0 +1,196 @@
+package ackhandler
+
+import (
+	"time"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+	"github.com/lucas-clemente/quic-go/internal/wire"
+)
+
+// number of ack-eliciting packets received before sending an ack.
+const packetsBeforeAck = 2
+
+type receivedPacketTracker struct {
+	largestObserved             protocol.PacketNumber
+	ignoreBelow                 protocol.PacketNumber
+	largestObservedReceivedTime time.Time
+	ect0, ect1, ecnce           uint64
+
+	packetHistory *receivedPacketHistory
+
+	maxAckDelay time.Duration
+	rttStats    *utils.RTTStats
+
+	hasNewAck bool // true as soon as we received an ack-eliciting new packet
+	ackQueued bool // true once we received more than 2 (or later in the connection 10) ack-eliciting packets
+
+	ackElicitingPacketsReceivedSinceLastAck int
+	ackAlarm                                time.Time
+	lastAck                                 *wire.AckFrame
+
+	logger utils.Logger
+
+	version protocol.VersionNumber
+}
+
+func newReceivedPacketTracker(
+	rttStats *utils.RTTStats,
+	logger utils.Logger,
+	version protocol.VersionNumber,
+) *receivedPacketTracker {
+	return &receivedPacketTracker{
+		packetHistory: newReceivedPacketHistory(),
+		maxAckDelay:   protocol.MaxAckDelay,
+		rttStats:      rttStats,
+		logger:        logger,
+		version:       version,
+	}
+}
+
+func (h *receivedPacketTracker) ReceivedPacket(packetNumber protocol.PacketNumber, ecn protocol.ECN, rcvTime time.Time, shouldInstigateAck bool) {
+	if packetNumber < h.ignoreBelow {
+		return
+	}
+
+	isMissing := h.isMissing(packetNumber)
+	if packetNumber >= h.largestObserved {
+		h.largestObserved = packetNumber
+		h.largestObservedReceivedTime = rcvTime
+	}
+
+	if isNew := h.packetHistory.ReceivedPacket(packetNumber); isNew && shouldInstigateAck {
+		h.hasNewAck = true
+	}
+	if shouldInstigateAck {
+		h.maybeQueueAck(packetNumber, rcvTime, isMissing)
+	}
+	switch ecn {
+	case protocol.ECNNon:
+	case protocol.ECT0:
+		h.ect0++
+	case protocol.ECT1:
+		h.ect1++
+	case protocol.ECNCE:
+		h.ecnce++
+	}
+}
+
+// IgnoreBelow sets a lower limit for acknowledging 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 %d.", 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()+1 && highestRange.Len() == 1
+}
+
+// maybeQueueAck queues an ACK, if necessary.
+func (h *receivedPacketTracker) maybeQueueAck(pn protocol.PacketNumber, rcvTime time.Time, wasMissing 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
+	}
+
+	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.
+	if wasMissing {
+		if h.logger.Debug() {
+			h.logger.Debugf("\tQueueing ACK because packet %d was missing before.", pn)
+		}
+		h.ackQueued = true
+	}
+
+	// send an ACK every 2 ack-eliciting packets
+	if h.ackElicitingPacketsReceivedSinceLastAck >= packetsBeforeAck {
+		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)
+	}
+
+	// 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
+	}
+
+	if h.ackQueued {
+		// cancel the ack alarm
+		h.ackAlarm = time.Time{}
+	}
+}
+
+func (h *receivedPacketTracker) GetAckFrame(onlyIfQueued bool) *wire.AckFrame {
+	if !h.hasNewAck {
+		return nil
+	}
+	now := time.Now()
+	if onlyIfQueued {
+		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(),
+		// Make sure that the DelayTime is always positive.
+		// This is not guaranteed on systems that don't have a monotonic clock.
+		DelayTime: utils.MaxDuration(0, now.Sub(h.largestObservedReceivedTime)),
+		ECT0:      h.ect0,
+		ECT1:      h.ect1,
+		ECNCE:     h.ecnce,
+	}
+
+	h.lastAck = ack
+	h.ackAlarm = time.Time{}
+	h.ackQueued = false
+	h.hasNewAck = false
+	h.ackElicitingPacketsReceivedSinceLastAck = 0
+	return ack
+}
+
+func (h *receivedPacketTracker) GetAlarmTimeout() time.Time { return h.ackAlarm }
+
+func (h *receivedPacketTracker) IsPotentiallyDuplicate(pn protocol.PacketNumber) bool {
+	return h.packetHistory.IsPotentiallyDuplicate(pn)
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/send_mode.go

@@ -0,0 +1,40 @@
+package ackhandler
+
+import "fmt"
+
+// The SendMode says what kind of packets can be sent.
+type SendMode uint8
+
+const (
+	// SendNone means that no packets should be sent
+	SendNone SendMode = iota
+	// SendAck means an ACK-only packet should be sent
+	SendAck
+	// SendPTOInitial means that an Initial probe packet should be sent
+	SendPTOInitial
+	// SendPTOHandshake means that a Handshake probe packet should be sent
+	SendPTOHandshake
+	// SendPTOAppData means that an Application data probe packet should be sent
+	SendPTOAppData
+	// SendAny means that any packet should be sent
+	SendAny
+)
+
+func (s SendMode) String() string {
+	switch s {
+	case SendNone:
+		return "none"
+	case SendAck:
+		return "ack"
+	case SendPTOInitial:
+		return "pto (Initial)"
+	case SendPTOHandshake:
+		return "pto (Handshake)"
+	case SendPTOAppData:
+		return "pto (Application Data)"
+	case SendAny:
+		return "any"
+	default:
+		return fmt.Sprintf("invalid send mode: %d", s)
+	}
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/sent_packet_handler.go

@@ -0,0 +1,832 @@
+package ackhandler
+
+import (
+	"errors"
+	"fmt"
+	"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/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
+)
+
+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, rttStats *utils.RTTStats) *packetNumberSpace {
+	var pns packetNumberGenerator
+	if skipPNs {
+		pns = newSkippingPacketNumberGenerator(initialPN, protocol.SkipPacketInitialPeriod, protocol.SkipPacketMaxPeriod)
+	} else {
+		pns = newSequentialPacketNumberGenerator(initialPN)
+	}
+	return &packetNumberSpace{
+		history:      newSentPacketHistory(rttStats),
+		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
+
+	perspective protocol.Perspective
+
+	tracer logging.ConnectionTracer
+	logger utils.Logger
+}
+
+var (
+	_ SentPacketHandler = &sentPacketHandler{}
+	_ sentPacketTracker = &sentPacketHandler{}
+)
+
+func newSentPacketHandler(
+	initialPN protocol.PacketNumber,
+	initialMaxDatagramSize protocol.ByteCount,
+	rttStats *utils.RTTStats,
+	pers protocol.Perspective,
+	tracer logging.ConnectionTracer,
+	logger utils.Logger,
+) *sentPacketHandler {
+	congestion := congestion.NewCubicSender(
+		congestion.DefaultClock{},
+		rttStats,
+		initialMaxDatagramSize,
+		true, // use Reno
+		tracer,
+	)
+
+	return &sentPacketHandler{
+		peerCompletedAddressValidation: pers == protocol.PerspectiveServer,
+		peerAddressValidated:           pers == protocol.PerspectiveClient,
+		initialPackets:                 newPacketNumberSpace(initialPN, false, rttStats),
+		handshakePackets:               newPacketNumberSpace(0, false, rttStats),
+		appDataPackets:                 newPacketNumberSpace(0, true, rttStats),
+		rttStats:                       rttStats,
+		congestion:                     congestion,
+		perspective:                    pers,
+		tracer:                         tracer,
+		logger:                         logger,
+	}
+}
+
+func (h *sentPacketHandler) DropPackets(encLevel protocol.EncryptionLevel) {
+	if h.perspective == protocol.PerspectiveClient && encLevel == protocol.EncryptionInitial {
+		// This function is called when the crypto setup seals a Handshake packet.
+		// If this Handshake packet is coalesced behind an Initial packet, we would drop the Initial packet number space
+		// before SentPacket() was called for that Initial packet.
+		return
+	}
+	h.dropPackets(encLevel)
+}
+
+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)
+		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 {
+				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.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(packet *Packet) {
+	h.bytesSent += packet.Length
+	// For the client, drop the Initial packet number space when the first Handshake packet is sent.
+	if h.perspective == protocol.PerspectiveClient && packet.EncryptionLevel == protocol.EncryptionHandshake && h.initialPackets != nil {
+		h.dropPackets(protocol.EncryptionInitial)
+	}
+	isAckEliciting := h.sentPacketImpl(packet)
+	h.getPacketNumberSpace(packet.EncryptionLevel).history.SentPacket(packet, isAckEliciting)
+	if h.tracer != nil && isAckEliciting {
+		h.tracer.UpdatedMetrics(h.rttStats, h.congestion.GetCongestionWindow(), h.bytesInFlight, h.packetsInFlight())
+	}
+	if isAckEliciting || !h.peerCompletedAddressValidation {
+		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) sentPacketImpl(packet *Packet) bool /* is ack-eliciting */ {
+	pnSpace := h.getPacketNumberSpace(packet.EncryptionLevel)
+
+	if h.logger.Debug() && pnSpace.history.HasOutstandingPackets() {
+		for p := utils.MaxPacketNumber(0, pnSpace.largestSent+1); p < packet.PacketNumber; p++ {
+			h.logger.Debugf("Skipping packet number %d", p)
+		}
+	}
+
+	pnSpace.largestSent = packet.PacketNumber
+	isAckEliciting := len(packet.Frames) > 0
+
+	if isAckEliciting {
+		pnSpace.lastAckElicitingPacketTime = packet.SendTime
+		packet.includedInBytesInFlight = true
+		h.bytesInFlight += packet.Length
+		if h.numProbesToSend > 0 {
+			h.numProbesToSend--
+		}
+	}
+	h.congestion.OnPacketSent(packet.SendTime, h.bytesInFlight, packet.PacketNumber, packet.Length, isAckEliciting)
+
+	return isAckEliciting
+}
+
+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",
+		}
+	}
+
+	pnSpace.largestAcked = utils.MaxPacketNumber(pnSpace.largestAcked, largestAcked)
+
+	// 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.MinDuration(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()
+		}
+	}
+	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)
+	}
+
+	// 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.ptoCount != 0 {
+			h.tracer.UpdatedPTOCount(0)
+		}
+		h.ptoCount = 0
+	}
+	h.numProbesToSend = 0
+
+	if h.tracer != nil {
+		h.tracer.UpdatedMetrics(h.rttStats, h.congestion.GetCongestionWindow(), h.bytesInFlight, h.packetsInFlight())
+	}
+
+	pnSpace.history.DeleteOldPackets(rcvTime)
+	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.MaxPacketNumber(h.lowestNotConfirmedAcked, p.LargestAcked+1)
+		}
+
+		for _, f := range p.Frames {
+			if f.OnAcked != nil {
+				f.OnAcked(f.Frame)
+			}
+		}
+		if err := pnSpace.history.Remove(p.PacketNumber); err != nil {
+			return nil, err
+		}
+		if h.tracer != 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
+}
+
+// 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.rttStats.PTO(false) << h.ptoCount)
+		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.rttStats.PTO(false) << h.ptoCount)
+		}
+	}
+	if h.handshakePackets != nil && !h.handshakePackets.lastAckElicitingPacketTime.IsZero() {
+		t := h.handshakePackets.lastAckElicitingPacketTime.Add(h.rttStats.PTO(false) << h.ptoCount)
+		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.rttStats.PTO(true) << h.ptoCount)
+		if pto.IsZero() || (!t.IsZero() && t.Before(pto)) {
+			pto = t
+			encLevel = protocol.Encryption1RTT
+		}
+	}
+	return pto, encLevel, true
+}
+
+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.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.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()
+			}
+		}
+		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()
+			}
+		}
+		return
+	}
+
+	// PTO alarm
+	ptoTime, encLevel, ok := h.getPTOTimeAndSpace()
+	if !ok {
+		return
+	}
+	h.alarm = ptoTime
+	if h.tracer != 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.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)
+
+	priorInFlight := h.bytesInFlight
+	return pnSpace.history.Iterate(func(p *Packet) (bool, error) {
+		if p.PacketNumber > pnSpace.largestAcked {
+			return false, nil
+		}
+		if p.declaredLost || p.skippedPacket {
+			return true, nil
+		}
+
+		var packetLost bool
+		if p.SendTime.Before(lostSendTime) {
+			packetLost = true
+			if h.logger.Debug() {
+				h.logger.Debugf("\tlost packet %d (time threshold)", p.PacketNumber)
+			}
+			if h.tracer != nil {
+				h.tracer.LostPacket(p.EncryptionLevel, p.PacketNumber, logging.PacketLossTimeThreshold)
+			}
+		} else if pnSpace.largestAcked >= p.PacketNumber+packetThreshold {
+			packetLost = true
+			if h.logger.Debug() {
+				h.logger.Debugf("\tlost packet %d (reordering threshold)", p.PacketNumber)
+			}
+			if h.tracer != 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 {
+			p.declaredLost = true
+			// 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.OnPacketLost(p.PacketNumber, p.Length, priorInFlight)
+			}
+		}
+		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(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 {
+		h.tracer.LossTimerExpired(logging.TimerTypePTO, encLevel)
+		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
+		_ = h.PopPacketNumber(protocol.Encryption1RTT)
+		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) 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 := 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
+	}
+	return SendAny
+}
+
+func (h *sentPacketHandler) TimeUntilSend() time.Time {
+	return h.congestion.TimeUntilSend(h.bytesInFlight)
+}
+
+func (h *sentPacketHandler) HasPacingBudget() bool {
+	return h.congestion.HasPacingBudget()
+}
+
+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)
+	p.declaredLost = true
+	return true
+}
+
+func (h *sentPacketHandler) queueFramesForRetransmission(p *Packet) {
+	if len(p.Frames) == 0 {
+		panic("no frames")
+	}
+	for _, f := range p.Frames {
+		f.OnLost(f.Frame)
+	}
+	p.Frames = nil
+}
+
+func (h *sentPacketHandler) ResetForRetry() 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.
+		now := time.Now()
+		h.rttStats.UpdateRTT(utils.MaxDuration(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(h.rttStats, h.congestion.GetCongestionWindow(), h.bytesInFlight, h.packetsInFlight())
+		}
+	}
+	h.initialPackets = newPacketNumberSpace(h.initialPackets.pns.Pop(), false, h.rttStats)
+	h.appDataPackets = newPacketNumberSpace(h.appDataPackets.pns.Pop(), true, h.rttStats)
+	oldAlarm := h.alarm
+	h.alarm = time.Time{}
+	if h.tracer != nil {
+		h.tracer.UpdatedPTOCount(0)
+		if !oldAlarm.IsZero() {
+			h.tracer.LossTimerCanceled()
+		}
+	}
+	h.ptoCount = 0
+	return nil
+}
+
+func (h *sentPacketHandler) SetHandshakeConfirmed() {
+	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()
+}

vendor/github.com/lucas-clemente/quic-go/internal/ackhandler/sent_packet_history.go

@@ -0,0 +1,108 @@
+package ackhandler
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+)
+
+type sentPacketHistory struct {
+	rttStats    *utils.RTTStats
+	packetList  *PacketList
+	packetMap   map[protocol.PacketNumber]*PacketElement
+	highestSent protocol.PacketNumber
+}
+
+func newSentPacketHistory(rttStats *utils.RTTStats) *sentPacketHistory {
+	return &sentPacketHistory{
+		rttStats:    rttStats,
+		packetList:  NewPacketList(),
+		packetMap:   make(map[protocol.PacketNumber]*PacketElement),
+		highestSent: protocol.InvalidPacketNumber,
+	}
+}
+
+func (h *sentPacketHistory) SentPacket(p *Packet, isAckEliciting bool) {
+	if p.PacketNumber <= h.highestSent {
+		panic("non-sequential packet number use")
+	}
+	// Skipped packet numbers.
+	for pn := h.highestSent + 1; pn < p.PacketNumber; pn++ {
+		el := h.packetList.PushBack(Packet{
+			PacketNumber:    pn,
+			EncryptionLevel: p.EncryptionLevel,
+			SendTime:        p.SendTime,
+			skippedPacket:   true,
+		})
+		h.packetMap[pn] = el
+	}
+	h.highestSent = p.PacketNumber
+
+	if isAckEliciting {
+		el := h.packetList.PushBack(*p)
+		h.packetMap[p.PacketNumber] = el
+	}
+}
+
+// Iterate iterates through all packets.
+func (h *sentPacketHistory) Iterate(cb func(*Packet) (cont bool, err error)) error {
+	cont := true
+	var next *PacketElement
+	for el := h.packetList.Front(); cont && el != nil; el = next {
+		var err error
+		next = el.Next()
+		cont, err = cb(&el.Value)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// FirstOutStanding returns the first outstanding packet.
+func (h *sentPacketHistory) FirstOutstanding() *Packet {
+	for el := h.packetList.Front(); el != nil; el = el.Next() {
+		p := &el.Value
+		if !p.declaredLost && !p.skippedPacket && !p.IsPathMTUProbePacket {
+			return p
+		}
+	}
+	return nil
+}
+
+func (h *sentPacketHistory) Len() int {
+	return len(h.packetMap)
+}
+
+func (h *sentPacketHistory) Remove(p protocol.PacketNumber) error {
+	el, ok := h.packetMap[p]
+	if !ok {
+		return fmt.Errorf("packet %d not found in sent packet history", p)
+	}
+	h.packetList.Remove(el)
+	delete(h.packetMap, p)
+	return nil
+}
+
+func (h *sentPacketHistory) HasOutstandingPackets() bool {
+	return h.FirstOutstanding() != nil
+}
+
+func (h *sentPacketHistory) DeleteOldPackets(now time.Time) {
+	maxAge := 3 * h.rttStats.PTO(false)
+	var nextEl *PacketElement
+	for el := h.packetList.Front(); el != nil; el = nextEl {
+		nextEl = el.Next()
+		p := el.Value
+		if p.SendTime.After(now.Add(-maxAge)) {
+			break
+		}
+		if !p.skippedPacket && !p.declaredLost { // should only happen in the case of drastic RTT changes
+			continue
+		}
+		delete(h.packetMap, p.PacketNumber)
+		h.packetList.Remove(el)
+	}
+}