implement packet history to efficiently calculate ACK ranges

ref #190

ackhandlernew/received_packet_history.go

@@ -0,0 +1,61 @@
+package ackhandlernew
+
+import (
+	"github.com/lucas-clemente/quic-go/protocol"
+	"github.com/lucas-clemente/quic-go/utils"
+)
+
+type receivedPacketHistory struct {
+	ranges *utils.PacketIntervalList
+}
+
+// newReceivedPacketHistory creates a new received packet history
+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) {
+	if h.ranges.Len() == 0 {
+		h.ranges.PushBack(utils.PacketInterval{Start: p, End: p})
+		return
+	}
+
+	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
+		}
+
+		var rangeExtended bool
+		if el.Value.End == p-1 { // extend a range at the end
+			rangeExtended = true
+			el.Value.End = p
+		} else if el.Value.Start == p+1 { // extend a range at the beginning
+			rangeExtended = true
+			el.Value.Start = p
+		}
+
+		// if a range was extended (either at the beginning or at the end, maybe it is possible to merge two ranges into one)
+		if rangeExtended {
+			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
+			}
+			return // if the two ranges were not merge, we're done here
+		}
+
+		// create a new range at the end
+		if p > el.Value.End {
+			h.ranges.InsertAfter(utils.PacketInterval{Start: p, End: p}, el)
+			return
+		}
+	}
+
+	// create a new range at the beginning
+	h.ranges.InsertBefore(utils.PacketInterval{Start: p, End: p}, h.ranges.Front())
+}

ackhandlernew/received_packet_history_test.go

@@ -0,0 +1,120 @@
+package ackhandlernew
+
+import (
+	"github.com/lucas-clemente/quic-go/utils"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("receivedPacketHistory", func() {
+	var (
+		hist *receivedPacketHistory
+	)
+
+	BeforeEach(func() {
+		hist = newReceivedPacketHistory()
+	})
+
+	It("adds the first packet", func() {
+		hist.ReceivedPacket(4)
+		Expect(hist.ranges.Len()).To(Equal(1))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 4}))
+	})
+
+	It("doesn't care about duplicate packets", func() {
+		hist.ReceivedPacket(4)
+		Expect(hist.ranges.Len()).To(Equal(1))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 4}))
+	})
+
+	It("adds a few consecutive packets", func() {
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(5)
+		hist.ReceivedPacket(6)
+		Expect(hist.ranges.Len()).To(Equal(1))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 6}))
+	})
+
+	It("doesn't care about a duplicate packet contained in an existing range", func() {
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(5)
+		hist.ReceivedPacket(6)
+		hist.ReceivedPacket(5)
+		Expect(hist.ranges.Len()).To(Equal(1))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 6}))
+	})
+
+	It("extends a range at the front", func() {
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(3)
+		Expect(hist.ranges.Len()).To(Equal(1))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 3, End: 4}))
+	})
+
+	It("creates a new range when a packet is lost", func() {
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(6)
+		Expect(hist.ranges.Len()).To(Equal(2))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 4}))
+		Expect(hist.ranges.Back().Value).To(Equal(utils.PacketInterval{Start: 6, End: 6}))
+	})
+
+	It("creates a new range in between two ranges", func() {
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(10)
+		Expect(hist.ranges.Len()).To(Equal(2))
+		hist.ReceivedPacket(7)
+		Expect(hist.ranges.Len()).To(Equal(3))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 4}))
+		Expect(hist.ranges.Front().Next().Value).To(Equal(utils.PacketInterval{Start: 7, End: 7}))
+		Expect(hist.ranges.Back().Value).To(Equal(utils.PacketInterval{Start: 10, End: 10}))
+	})
+
+	It("creates a new range before an existing range for a belated packet", func() {
+		hist.ReceivedPacket(6)
+		hist.ReceivedPacket(4)
+		Expect(hist.ranges.Len()).To(Equal(2))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 4}))
+		Expect(hist.ranges.Back().Value).To(Equal(utils.PacketInterval{Start: 6, End: 6}))
+	})
+
+	It("extends a previous range at the end", func() {
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(7)
+		hist.ReceivedPacket(5)
+		Expect(hist.ranges.Len()).To(Equal(2))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 5}))
+		Expect(hist.ranges.Back().Value).To(Equal(utils.PacketInterval{Start: 7, End: 7}))
+	})
+
+	It("extends a range at the front", func() {
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(7)
+		hist.ReceivedPacket(6)
+		Expect(hist.ranges.Len()).To(Equal(2))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 4}))
+		Expect(hist.ranges.Back().Value).To(Equal(utils.PacketInterval{Start: 6, End: 7}))
+	})
+
+	It("closes a range", func() {
+		hist.ReceivedPacket(6)
+		hist.ReceivedPacket(4)
+		Expect(hist.ranges.Len()).To(Equal(2))
+		hist.ReceivedPacket(5)
+		Expect(hist.ranges.Len()).To(Equal(1))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 4, End: 6}))
+	})
+
+	It("closes a range in the middle", func() {
+		hist.ReceivedPacket(1)
+		hist.ReceivedPacket(10)
+		hist.ReceivedPacket(4)
+		hist.ReceivedPacket(6)
+		Expect(hist.ranges.Len()).To(Equal(4))
+		hist.ReceivedPacket(5)
+		Expect(hist.ranges.Len()).To(Equal(3))
+		Expect(hist.ranges.Front().Value).To(Equal(utils.PacketInterval{Start: 1, End: 1}))
+		Expect(hist.ranges.Front().Next().Value).To(Equal(utils.PacketInterval{Start: 4, End: 6}))
+		Expect(hist.ranges.Back().Value).To(Equal(utils.PacketInterval{Start: 10, End: 10}))
+	})
+})

codecov.yml

@@ -1,3 +1,4 @@
-coverage: 
+coverage:
-  ignore: 
+  ignore:
     - /utils/byteinterval_linkedlist.go
+    - /utils/packetinterval_linkedlist.go

utils/packet_interval.go

@@ -0,0 +1,10 @@
+package utils
+
+import "github.com/lucas-clemente/quic-go/protocol"
+
+// PacketInterval is an interval from one PacketNumber to the other
+// +gen linkedlist
+type PacketInterval struct {
+	Start protocol.PacketNumber
+	End   protocol.PacketNumber
+}

utils/packetinterval_linkedlist.go

@@ -0,0 +1,214 @@
+// Generated by: main
+// TypeWriter: linkedlist
+// Directive: +gen on PacketInterval
+
+package utils
+
+// List is a modification of http://golang.org/pkg/container/list/
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// PacketIntervalElement is an element of a linked list.
+type PacketIntervalElement 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 *PacketIntervalElement
+
+	// The list to which this element belongs.
+	list *PacketIntervalList
+
+	// The value stored with this element.
+	Value PacketInterval
+}
+
+// Next returns the next list element or nil.
+func (e *PacketIntervalElement) Next() *PacketIntervalElement {
+	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 *PacketIntervalElement) Prev() *PacketIntervalElement {
+	if p := e.prev; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+// PacketIntervalList represents a doubly linked list.
+// The zero value for PacketIntervalList is an empty list ready to use.
+type PacketIntervalList struct {
+	root PacketIntervalElement // 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 *PacketIntervalList) Init() *PacketIntervalList {
+	l.root.next = &l.root
+	l.root.prev = &l.root
+	l.len = 0
+	return l
+}
+
+// NewPacketIntervalList returns an initialized list.
+func NewPacketIntervalList() *PacketIntervalList { return new(PacketIntervalList).Init() }
+
+// Len returns the number of elements of list l.
+// The complexity is O(1).
+func (l *PacketIntervalList) Len() int { return l.len }
+
+// Front returns the first element of list l or nil.
+func (l *PacketIntervalList) Front() *PacketIntervalElement {
+	if l.len == 0 {
+		return nil
+	}
+	return l.root.next
+}
+
+// Back returns the last element of list l or nil.
+func (l *PacketIntervalList) Back() *PacketIntervalElement {
+	if l.len == 0 {
+		return nil
+	}
+	return l.root.prev
+}
+
+// lazyInit lazily initializes a zero PacketIntervalList value.
+func (l *PacketIntervalList) lazyInit() {
+	if l.root.next == nil {
+		l.Init()
+	}
+}
+
+// insert inserts e after at, increments l.len, and returns e.
+func (l *PacketIntervalList) insert(e, at *PacketIntervalElement) *PacketIntervalElement {
+	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(&PacketIntervalElement{Value: v}, at).
+func (l *PacketIntervalList) insertValue(v PacketInterval, at *PacketIntervalElement) *PacketIntervalElement {
+	return l.insert(&PacketIntervalElement{Value: v}, at)
+}
+
+// remove removes e from its list, decrements l.len, and returns e.
+func (l *PacketIntervalList) remove(e *PacketIntervalElement) *PacketIntervalElement {
+	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.
+func (l *PacketIntervalList) Remove(e *PacketIntervalElement) PacketInterval {
+	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 PacketIntervalElement) 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 *PacketIntervalList) PushFront(v PacketInterval) *PacketIntervalElement {
+	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 *PacketIntervalList) PushBack(v PacketInterval) *PacketIntervalElement {
+	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.
+func (l *PacketIntervalList) InsertBefore(v PacketInterval, mark *PacketIntervalElement) *PacketIntervalElement {
+	if mark.list != l {
+		return nil
+	}
+	// see comment in PacketIntervalList.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.
+func (l *PacketIntervalList) InsertAfter(v PacketInterval, mark *PacketIntervalElement) *PacketIntervalElement {
+	if mark.list != l {
+		return nil
+	}
+	// see comment in PacketIntervalList.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.
+func (l *PacketIntervalList) MoveToFront(e *PacketIntervalElement) {
+	if e.list != l || l.root.next == e {
+		return
+	}
+	// see comment in PacketIntervalList.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.
+func (l *PacketIntervalList) MoveToBack(e *PacketIntervalElement) {
+	if e.list != l || l.root.prev == e {
+		return
+	}
+	// see comment in PacketIntervalList.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.
+func (l *PacketIntervalList) MoveBefore(e, mark *PacketIntervalElement) {
+	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 is not an element of l, or e == mark, the list is not modified.
+func (l *PacketIntervalList) MoveAfter(e, mark *PacketIntervalElement) {
+	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.
+func (l *PacketIntervalList) PushBackList(other *PacketIntervalList) {
+	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.
+func (l *PacketIntervalList) PushFrontList(other *PacketIntervalList) {
+	l.lazyInit()
+	for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
+		l.insertValue(e.Value, &l.root)
+	}
+}