/
ack_frame_legacy.go
364 lines (307 loc) · 9.08 KB
/
ack_frame_legacy.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
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
package wire
import (
"bytes"
"errors"
"time"
"github.com/lucas-clemente/quic-go/internal/protocol"
"github.com/lucas-clemente/quic-go/internal/utils"
)
var errInvalidAckRanges = errors.New("AckFrame: ACK frame contains invalid ACK ranges")
func parseAckFrameLegacy(r *bytes.Reader, _ protocol.VersionNumber) (*AckFrame, error) {
frame := &AckFrame{}
typeByte, err := r.ReadByte()
if err != nil {
return nil, err
}
hasMissingRanges := typeByte&0x20 == 0x20
largestAckedLen := 2 * ((typeByte & 0x0C) >> 2)
if largestAckedLen == 0 {
largestAckedLen = 1
}
missingSequenceNumberDeltaLen := 2 * (typeByte & 0x03)
if missingSequenceNumberDeltaLen == 0 {
missingSequenceNumberDeltaLen = 1
}
la, err := utils.BigEndian.ReadUintN(r, largestAckedLen)
if err != nil {
return nil, err
}
largestAcked := protocol.PacketNumber(la)
delay, err := utils.BigEndian.ReadUfloat16(r)
if err != nil {
return nil, err
}
frame.DelayTime = time.Duration(delay) * time.Microsecond
var numAckBlocks uint8
if hasMissingRanges {
numAckBlocks, err = r.ReadByte()
if err != nil {
return nil, err
}
}
if hasMissingRanges && numAckBlocks == 0 {
return nil, errInvalidAckRanges
}
abl, err := utils.BigEndian.ReadUintN(r, missingSequenceNumberDeltaLen)
if err != nil {
return nil, err
}
ackBlockLength := protocol.PacketNumber(abl)
if largestAcked > 0 && ackBlockLength < 1 {
return nil, errors.New("invalid first ACK range")
}
if ackBlockLength > largestAcked+1 {
return nil, errInvalidAckRanges
}
if hasMissingRanges {
ackRange := AckRange{
Smallest: largestAcked - ackBlockLength + 1,
Largest: largestAcked,
}
frame.AckRanges = append(frame.AckRanges, ackRange)
var inLongBlock bool
var lastRangeComplete bool
for i := uint8(0); i < numAckBlocks; i++ {
var gap uint8
gap, err = r.ReadByte()
if err != nil {
return nil, err
}
abl, err := utils.BigEndian.ReadUintN(r, missingSequenceNumberDeltaLen)
if err != nil {
return nil, err
}
ackBlockLength := protocol.PacketNumber(abl)
if inLongBlock {
frame.AckRanges[len(frame.AckRanges)-1].Smallest -= protocol.PacketNumber(gap) + ackBlockLength
frame.AckRanges[len(frame.AckRanges)-1].Largest -= protocol.PacketNumber(gap)
} else {
lastRangeComplete = false
ackRange := AckRange{
Largest: frame.AckRanges[len(frame.AckRanges)-1].Smallest - protocol.PacketNumber(gap) - 1,
}
ackRange.Smallest = ackRange.Largest - ackBlockLength + 1
frame.AckRanges = append(frame.AckRanges, ackRange)
}
if ackBlockLength > 0 {
lastRangeComplete = true
}
inLongBlock = (ackBlockLength == 0)
}
// if the last range was not complete, First and Last make no sense
// remove the range from frame.AckRanges
if !lastRangeComplete {
frame.AckRanges = frame.AckRanges[:len(frame.AckRanges)-1]
}
} else {
frame.AckRanges = make([]AckRange, 1)
if largestAcked != 0 {
frame.AckRanges[0].Largest = largestAcked
frame.AckRanges[0].Smallest = largestAcked + 1 - ackBlockLength
}
}
if !frame.validateAckRanges() {
return nil, errInvalidAckRanges
}
var numTimestamp byte
numTimestamp, err = r.ReadByte()
if err != nil {
return nil, err
}
if numTimestamp > 0 {
// Delta Largest acked
_, err = r.ReadByte()
if err != nil {
return nil, err
}
// First Timestamp
_, err = utils.BigEndian.ReadUint32(r)
if err != nil {
return nil, err
}
for i := 0; i < int(numTimestamp)-1; i++ {
// Delta Largest acked
_, err = r.ReadByte()
if err != nil {
return nil, err
}
// Time Since Previous Timestamp
_, err = utils.BigEndian.ReadUint16(r)
if err != nil {
return nil, err
}
}
}
return frame, nil
}
func (f *AckFrame) writeLegacy(b *bytes.Buffer, _ protocol.VersionNumber) error {
largestAcked := f.LargestAcked()
largestAckedLen := protocol.GetPacketNumberLength(largestAcked)
typeByte := uint8(0x40)
if largestAckedLen != protocol.PacketNumberLen1 {
typeByte ^= (uint8(largestAckedLen / 2)) << 2
}
missingSequenceNumberDeltaLen := f.getMissingSequenceNumberDeltaLen()
if missingSequenceNumberDeltaLen != protocol.PacketNumberLen1 {
typeByte ^= (uint8(missingSequenceNumberDeltaLen / 2))
}
if f.HasMissingRanges() {
typeByte |= 0x20
}
b.WriteByte(typeByte)
switch largestAckedLen {
case protocol.PacketNumberLen1:
b.WriteByte(uint8(largestAcked))
case protocol.PacketNumberLen2:
utils.BigEndian.WriteUint16(b, uint16(largestAcked))
case protocol.PacketNumberLen4:
utils.BigEndian.WriteUint32(b, uint32(largestAcked))
case protocol.PacketNumberLen6:
utils.BigEndian.WriteUint48(b, uint64(largestAcked)&(1<<48-1))
}
utils.BigEndian.WriteUfloat16(b, uint64(f.DelayTime/time.Microsecond))
var numRanges uint64
var numRangesWritten uint64
if f.HasMissingRanges() {
numRanges = f.numWritableNackRanges()
if numRanges > 0xFF {
panic("AckFrame: Too many ACK ranges")
}
b.WriteByte(uint8(numRanges - 1))
}
var firstAckBlockLength protocol.PacketNumber
if !f.HasMissingRanges() {
firstAckBlockLength = largestAcked - f.LowestAcked() + 1
} else {
firstAckBlockLength = largestAcked - f.AckRanges[0].Smallest + 1
numRangesWritten++
}
switch missingSequenceNumberDeltaLen {
case protocol.PacketNumberLen1:
b.WriteByte(uint8(firstAckBlockLength))
case protocol.PacketNumberLen2:
utils.BigEndian.WriteUint16(b, uint16(firstAckBlockLength))
case protocol.PacketNumberLen4:
utils.BigEndian.WriteUint32(b, uint32(firstAckBlockLength))
case protocol.PacketNumberLen6:
utils.BigEndian.WriteUint48(b, uint64(firstAckBlockLength)&(1<<48-1))
}
for i, ackRange := range f.AckRanges {
if i == 0 {
continue
}
length := ackRange.Largest - ackRange.Smallest + 1
gap := f.AckRanges[i-1].Smallest - ackRange.Largest - 1
num := gap/0xFF + 1
if gap%0xFF == 0 {
num--
}
if num == 1 {
b.WriteByte(uint8(gap))
switch missingSequenceNumberDeltaLen {
case protocol.PacketNumberLen1:
b.WriteByte(uint8(length))
case protocol.PacketNumberLen2:
utils.BigEndian.WriteUint16(b, uint16(length))
case protocol.PacketNumberLen4:
utils.BigEndian.WriteUint32(b, uint32(length))
case protocol.PacketNumberLen6:
utils.BigEndian.WriteUint48(b, uint64(length)&(1<<48-1))
}
numRangesWritten++
} else {
for i := 0; i < int(num); i++ {
var lengthWritten uint64
var gapWritten uint8
if i == int(num)-1 { // last block
lengthWritten = uint64(length)
gapWritten = uint8(1 + ((gap - 1) % 255))
} else {
lengthWritten = 0
gapWritten = 0xFF
}
b.WriteByte(gapWritten)
switch missingSequenceNumberDeltaLen {
case protocol.PacketNumberLen1:
b.WriteByte(uint8(lengthWritten))
case protocol.PacketNumberLen2:
utils.BigEndian.WriteUint16(b, uint16(lengthWritten))
case protocol.PacketNumberLen4:
utils.BigEndian.WriteUint32(b, uint32(lengthWritten))
case protocol.PacketNumberLen6:
utils.BigEndian.WriteUint48(b, lengthWritten&(1<<48-1))
}
numRangesWritten++
}
}
// this is needed if not all AckRanges can be written to the ACK frame (if there are more than 0xFF)
if numRangesWritten >= numRanges {
break
}
}
if numRanges != numRangesWritten {
return errors.New("BUG: Inconsistent number of ACK ranges written")
}
b.WriteByte(0) // no timestamps
return nil
}
func (f *AckFrame) lengthLegacy(_ protocol.VersionNumber) protocol.ByteCount {
length := protocol.ByteCount(1 + 2 + 1) // 1 TypeByte, 2 ACK delay time, 1 Num Timestamp
length += protocol.ByteCount(protocol.GetPacketNumberLength(f.LargestAcked()))
missingSequenceNumberDeltaLen := protocol.ByteCount(f.getMissingSequenceNumberDeltaLen())
if f.HasMissingRanges() {
length += (1 + missingSequenceNumberDeltaLen) * protocol.ByteCount(f.numWritableNackRanges())
} else {
length += missingSequenceNumberDeltaLen
}
// we don't write
return length
}
// numWritableNackRanges calculates the number of ACK blocks that are about to be written
// this number is different from len(f.AckRanges) for the case of long gaps (> 255 packets)
func (f *AckFrame) numWritableNackRanges() uint64 {
if len(f.AckRanges) == 0 {
return 0
}
var numRanges uint64
for i, ackRange := range f.AckRanges {
if i == 0 {
continue
}
lastAckRange := f.AckRanges[i-1]
gap := lastAckRange.Smallest - ackRange.Largest - 1
rangeLength := 1 + uint64(gap)/0xFF
if uint64(gap)%0xFF == 0 {
rangeLength--
}
if numRanges+rangeLength < 0xFF {
numRanges += rangeLength
} else {
break
}
}
return numRanges + 1
}
func (f *AckFrame) getMissingSequenceNumberDeltaLen() protocol.PacketNumberLen {
var maxRangeLength protocol.PacketNumber
if f.HasMissingRanges() {
for _, ackRange := range f.AckRanges {
rangeLength := ackRange.Largest - ackRange.Smallest + 1
if rangeLength > maxRangeLength {
maxRangeLength = rangeLength
}
}
} else {
maxRangeLength = f.LargestAcked() - f.LowestAcked() + 1
}
if maxRangeLength <= 0xFF {
return protocol.PacketNumberLen1
}
if maxRangeLength <= 0xFFFF {
return protocol.PacketNumberLen2
}
if maxRangeLength <= 0xFFFFFFFF {
return protocol.PacketNumberLen4
}
return protocol.PacketNumberLen6
}