-
Notifications
You must be signed in to change notification settings - Fork 4.6k
/
ack_frame.go
229 lines (193 loc) · 6.02 KB
/
ack_frame.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
package wire
import (
"bytes"
"errors"
"sort"
"time"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/protocol"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/utils"
)
// TODO: use the value sent in the transport parameters
const ackDelayExponent = 3
var errInvalidAckRanges = errors.New("AckFrame: ACK frame contains invalid ACK ranges")
// An AckFrame is an ACK frame
type AckFrame struct {
AckRanges []AckRange // has to be ordered. The highest ACK range goes first, the lowest ACK range goes last
DelayTime time.Duration
}
// parseAckFrame reads an ACK frame
func parseAckFrame(r *bytes.Reader, version protocol.VersionNumber) (*AckFrame, error) {
typeByte, err := r.ReadByte()
if err != nil {
return nil, err
}
ecn := typeByte&0x1 > 0
frame := &AckFrame{}
la, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
largestAcked := protocol.PacketNumber(la)
delay, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
frame.DelayTime = time.Duration(delay*1<<ackDelayExponent) * time.Microsecond
numBlocks, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
// read the first ACK range
ab, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
ackBlock := protocol.PacketNumber(ab)
if ackBlock > largestAcked {
return nil, errors.New("invalid first ACK range")
}
smallest := largestAcked - ackBlock
// read all the other ACK ranges
frame.AckRanges = append(frame.AckRanges, AckRange{Smallest: smallest, Largest: largestAcked})
for i := uint64(0); i < numBlocks; i++ {
g, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
gap := protocol.PacketNumber(g)
if smallest < gap+2 {
return nil, errInvalidAckRanges
}
largest := smallest - gap - 2
ab, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
ackBlock := protocol.PacketNumber(ab)
if ackBlock > largest {
return nil, errInvalidAckRanges
}
smallest = largest - ackBlock
frame.AckRanges = append(frame.AckRanges, AckRange{Smallest: smallest, Largest: largest})
}
if !frame.validateAckRanges() {
return nil, errInvalidAckRanges
}
// parse (and skip) the ECN section
if ecn {
for i := 0; i < 3; i++ {
if _, err := utils.ReadVarInt(r); err != nil {
return nil, err
}
}
}
return frame, nil
}
// Write writes an ACK frame.
func (f *AckFrame) Write(b *bytes.Buffer, version protocol.VersionNumber) error {
b.WriteByte(0x2)
utils.WriteVarInt(b, uint64(f.LargestAcked()))
utils.WriteVarInt(b, encodeAckDelay(f.DelayTime))
numRanges := f.numEncodableAckRanges()
utils.WriteVarInt(b, uint64(numRanges-1))
// write the first range
_, firstRange := f.encodeAckRange(0)
utils.WriteVarInt(b, firstRange)
// write all the other range
for i := 1; i < numRanges; i++ {
gap, len := f.encodeAckRange(i)
utils.WriteVarInt(b, gap)
utils.WriteVarInt(b, len)
}
return nil
}
// Length of a written frame
func (f *AckFrame) Length(version protocol.VersionNumber) protocol.ByteCount {
largestAcked := f.AckRanges[0].Largest
numRanges := f.numEncodableAckRanges()
length := 1 + utils.VarIntLen(uint64(largestAcked)) + utils.VarIntLen(encodeAckDelay(f.DelayTime))
length += utils.VarIntLen(uint64(numRanges - 1))
lowestInFirstRange := f.AckRanges[0].Smallest
length += utils.VarIntLen(uint64(largestAcked - lowestInFirstRange))
for i := 1; i < numRanges; i++ {
gap, len := f.encodeAckRange(i)
length += utils.VarIntLen(gap)
length += utils.VarIntLen(len)
}
return length
}
// gets the number of ACK ranges that can be encoded
// such that the resulting frame is smaller than the maximum ACK frame size
func (f *AckFrame) numEncodableAckRanges() int {
length := 1 + utils.VarIntLen(uint64(f.LargestAcked())) + utils.VarIntLen(encodeAckDelay(f.DelayTime))
length += 2 // assume that the number of ranges will consume 2 bytes
for i := 1; i < len(f.AckRanges); i++ {
gap, len := f.encodeAckRange(i)
rangeLen := utils.VarIntLen(gap) + utils.VarIntLen(len)
if length+rangeLen > protocol.MaxAckFrameSize {
// Writing range i would exceed the MaxAckFrameSize.
// So encode one range less than that.
return i - 1
}
length += rangeLen
}
return len(f.AckRanges)
}
func (f *AckFrame) encodeAckRange(i int) (uint64 /* gap */, uint64 /* length */) {
if i == 0 {
return 0, uint64(f.AckRanges[0].Largest - f.AckRanges[0].Smallest)
}
return uint64(f.AckRanges[i-1].Smallest - f.AckRanges[i].Largest - 2),
uint64(f.AckRanges[i].Largest - f.AckRanges[i].Smallest)
}
// HasMissingRanges returns if this frame reports any missing packets
func (f *AckFrame) HasMissingRanges() bool {
return len(f.AckRanges) > 1
}
func (f *AckFrame) validateAckRanges() bool {
if len(f.AckRanges) == 0 {
return false
}
// check the validity of every single ACK range
for _, ackRange := range f.AckRanges {
if ackRange.Smallest > ackRange.Largest {
return false
}
}
// check the consistency for ACK with multiple NACK ranges
for i, ackRange := range f.AckRanges {
if i == 0 {
continue
}
lastAckRange := f.AckRanges[i-1]
if lastAckRange.Smallest <= ackRange.Smallest {
return false
}
if lastAckRange.Smallest <= ackRange.Largest+1 {
return false
}
}
return true
}
// LargestAcked is the largest acked packet number
func (f *AckFrame) LargestAcked() protocol.PacketNumber {
return f.AckRanges[0].Largest
}
// LowestAcked is the lowest acked packet number
func (f *AckFrame) LowestAcked() protocol.PacketNumber {
return f.AckRanges[len(f.AckRanges)-1].Smallest
}
// AcksPacket determines if this ACK frame acks a certain packet number
func (f *AckFrame) AcksPacket(p protocol.PacketNumber) bool {
if p < f.LowestAcked() || p > f.LargestAcked() {
return false
}
i := sort.Search(len(f.AckRanges), func(i int) bool {
return p >= f.AckRanges[i].Smallest
})
// i will always be < len(f.AckRanges), since we checked above that p is not bigger than the largest acked
return p <= f.AckRanges[i].Largest
}
func encodeAckDelay(delay time.Duration) uint64 {
return uint64(delay.Nanoseconds() / (1000 * (1 << ackDelayExponent)))
}