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
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
|
/*
* Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "net/dcsctp/rx/traditional_reassembly_streams.h"
#include <stddef.h>
#include <cstdint>
#include <functional>
#include <iterator>
#include <map>
#include <numeric>
#include <utility>
#include <vector>
#include "absl/algorithm/container.h"
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "net/dcsctp/common/sequence_numbers.h"
#include "net/dcsctp/packet/chunk/forward_tsn_common.h"
#include "net/dcsctp/packet/data.h"
#include "net/dcsctp/public/dcsctp_message.h"
#include "rtc_base/logging.h"
namespace dcsctp {
namespace {
// Given a map (`chunks`) and an iterator to within that map (`iter`), this
// function will return an iterator to the first chunk in that message, which
// has the `is_beginning` flag set. If there are any gaps, or if the beginning
// can't be found, `absl::nullopt` is returned.
absl::optional<std::map<UnwrappedTSN, Data>::iterator> FindBeginning(
const std::map<UnwrappedTSN, Data>& chunks,
std::map<UnwrappedTSN, Data>::iterator iter) {
UnwrappedTSN prev_tsn = iter->first;
for (;;) {
if (iter->second.is_beginning) {
return iter;
}
if (iter == chunks.begin()) {
return absl::nullopt;
}
--iter;
if (iter->first.next_value() != prev_tsn) {
return absl::nullopt;
}
prev_tsn = iter->first;
}
}
// Given a map (`chunks`) and an iterator to within that map (`iter`), this
// function will return an iterator to the chunk after the last chunk in that
// message, which has the `is_end` flag set. If there are any gaps, or if the
// end can't be found, `absl::nullopt` is returned.
absl::optional<std::map<UnwrappedTSN, Data>::iterator> FindEnd(
std::map<UnwrappedTSN, Data>& chunks,
std::map<UnwrappedTSN, Data>::iterator iter) {
UnwrappedTSN prev_tsn = iter->first;
for (;;) {
if (iter->second.is_end) {
return ++iter;
}
++iter;
if (iter == chunks.end()) {
return absl::nullopt;
}
if (iter->first != prev_tsn.next_value()) {
return absl::nullopt;
}
prev_tsn = iter->first;
}
}
} // namespace
TraditionalReassemblyStreams::TraditionalReassemblyStreams(
absl::string_view log_prefix,
OnAssembledMessage on_assembled_message)
: log_prefix_(log_prefix),
on_assembled_message_(std::move(on_assembled_message)) {}
int TraditionalReassemblyStreams::UnorderedStream::Add(UnwrappedTSN tsn,
Data data) {
if (data.is_beginning && data.is_end) {
// Fastpath for already assembled chunks.
AssembleMessage(tsn, std::move(data));
return 0;
}
int queued_bytes = data.size();
auto [it, inserted] = chunks_.emplace(tsn, std::move(data));
if (!inserted) {
return 0;
}
queued_bytes -= TryToAssembleMessage(it);
return queued_bytes;
}
size_t TraditionalReassemblyStreams::UnorderedStream::TryToAssembleMessage(
ChunkMap::iterator iter) {
// TODO(boivie): This method is O(N) with the number of fragments in a
// message, which can be inefficient for very large values of N. This could be
// optimized by e.g. only trying to assemble a message once _any_ beginning
// and _any_ end has been found.
absl::optional<ChunkMap::iterator> start = FindBeginning(chunks_, iter);
if (!start.has_value()) {
return 0;
}
absl::optional<ChunkMap::iterator> end = FindEnd(chunks_, iter);
if (!end.has_value()) {
return 0;
}
size_t bytes_assembled = AssembleMessage(*start, *end);
chunks_.erase(*start, *end);
return bytes_assembled;
}
size_t TraditionalReassemblyStreams::StreamBase::AssembleMessage(
const ChunkMap::iterator start,
const ChunkMap::iterator end) {
size_t count = std::distance(start, end);
if (count == 1) {
// Fast path - zero-copy
return AssembleMessage(start->first, std::move(start->second));
}
// Slow path - will need to concatenate the payload.
std::vector<UnwrappedTSN> tsns;
std::vector<uint8_t> payload;
size_t payload_size = std::accumulate(
start, end, 0,
[](size_t v, const auto& p) { return v + p.second.size(); });
tsns.reserve(count);
payload.reserve(payload_size);
for (auto it = start; it != end; ++it) {
const Data& data = it->second;
tsns.push_back(it->first);
payload.insert(payload.end(), data.payload.begin(), data.payload.end());
}
DcSctpMessage message(start->second.stream_id, start->second.ppid,
std::move(payload));
parent_.on_assembled_message_(tsns, std::move(message));
return payload_size;
}
size_t TraditionalReassemblyStreams::StreamBase::AssembleMessage(
UnwrappedTSN tsn,
Data data) {
// Fast path - zero-copy
size_t payload_size = data.size();
UnwrappedTSN tsns[1] = {tsn};
DcSctpMessage message(data.stream_id, data.ppid, std::move(data.payload));
parent_.on_assembled_message_(tsns, std::move(message));
return payload_size;
}
size_t TraditionalReassemblyStreams::UnorderedStream::EraseTo(
UnwrappedTSN tsn) {
auto end_iter = chunks_.upper_bound(tsn);
size_t removed_bytes = std::accumulate(
chunks_.begin(), end_iter, 0,
[](size_t r, const auto& p) { return r + p.second.size(); });
chunks_.erase(chunks_.begin(), end_iter);
return removed_bytes;
}
size_t TraditionalReassemblyStreams::OrderedStream::TryToAssembleMessage() {
if (chunks_by_ssn_.empty() || chunks_by_ssn_.begin()->first != next_ssn_) {
return 0;
}
ChunkMap& chunks = chunks_by_ssn_.begin()->second;
if (!chunks.begin()->second.is_beginning || !chunks.rbegin()->second.is_end) {
return 0;
}
uint32_t tsn_diff =
UnwrappedTSN::Difference(chunks.rbegin()->first, chunks.begin()->first);
if (tsn_diff != chunks.size() - 1) {
return 0;
}
size_t assembled_bytes = AssembleMessage(chunks.begin(), chunks.end());
chunks_by_ssn_.erase(chunks_by_ssn_.begin());
next_ssn_.Increment();
return assembled_bytes;
}
size_t TraditionalReassemblyStreams::OrderedStream::TryToAssembleMessages() {
size_t assembled_bytes = 0;
for (;;) {
size_t assembled_bytes_this_iter = TryToAssembleMessage();
if (assembled_bytes_this_iter == 0) {
break;
}
assembled_bytes += assembled_bytes_this_iter;
}
return assembled_bytes;
}
size_t
TraditionalReassemblyStreams::OrderedStream::TryToAssembleMessagesFastpath(
UnwrappedSSN ssn,
UnwrappedTSN tsn,
Data data) {
RTC_DCHECK(ssn == next_ssn_);
size_t assembled_bytes = 0;
if (data.is_beginning && data.is_end) {
assembled_bytes += AssembleMessage(tsn, std::move(data));
next_ssn_.Increment();
} else {
size_t queued_bytes = data.size();
auto [iter, inserted] = chunks_by_ssn_[ssn].emplace(tsn, std::move(data));
if (!inserted) {
// Not actually assembled, but deduplicated meaning queued size doesn't
// include this message.
return queued_bytes;
}
}
return assembled_bytes + TryToAssembleMessages();
}
int TraditionalReassemblyStreams::OrderedStream::Add(UnwrappedTSN tsn,
Data data) {
int queued_bytes = data.size();
UnwrappedSSN ssn = ssn_unwrapper_.Unwrap(data.ssn);
if (ssn == next_ssn_) {
return queued_bytes -
TryToAssembleMessagesFastpath(ssn, tsn, std::move(data));
}
auto [iter, inserted] = chunks_by_ssn_[ssn].emplace(tsn, std::move(data));
if (!inserted) {
return 0;
}
return queued_bytes;
}
size_t TraditionalReassemblyStreams::OrderedStream::EraseTo(SSN ssn) {
UnwrappedSSN unwrapped_ssn = ssn_unwrapper_.Unwrap(ssn);
auto end_iter = chunks_by_ssn_.upper_bound(unwrapped_ssn);
size_t removed_bytes = std::accumulate(
chunks_by_ssn_.begin(), end_iter, 0, [](size_t r1, const auto& p) {
return r1 +
absl::c_accumulate(p.second, 0, [](size_t r2, const auto& q) {
return r2 + q.second.size();
});
});
chunks_by_ssn_.erase(chunks_by_ssn_.begin(), end_iter);
if (unwrapped_ssn >= next_ssn_) {
unwrapped_ssn.Increment();
next_ssn_ = unwrapped_ssn;
}
removed_bytes += TryToAssembleMessages();
return removed_bytes;
}
int TraditionalReassemblyStreams::Add(UnwrappedTSN tsn, Data data) {
if (data.is_unordered) {
auto it = unordered_streams_.try_emplace(data.stream_id, this).first;
return it->second.Add(tsn, std::move(data));
}
auto it = ordered_streams_.try_emplace(data.stream_id, this).first;
return it->second.Add(tsn, std::move(data));
}
size_t TraditionalReassemblyStreams::HandleForwardTsn(
UnwrappedTSN new_cumulative_ack_tsn,
rtc::ArrayView<const AnyForwardTsnChunk::SkippedStream> skipped_streams) {
size_t bytes_removed = 0;
// The `skipped_streams` only cover ordered messages - need to
// iterate all unordered streams manually to remove those chunks.
for (auto& [unused, stream] : unordered_streams_) {
bytes_removed += stream.EraseTo(new_cumulative_ack_tsn);
}
for (const auto& skipped_stream : skipped_streams) {
auto it =
ordered_streams_.try_emplace(skipped_stream.stream_id, this).first;
bytes_removed += it->second.EraseTo(skipped_stream.ssn);
}
return bytes_removed;
}
void TraditionalReassemblyStreams::ResetStreams(
rtc::ArrayView<const StreamID> stream_ids) {
if (stream_ids.empty()) {
for (auto& [stream_id, stream] : ordered_streams_) {
RTC_DLOG(LS_VERBOSE) << log_prefix_
<< "Resetting implicit stream_id=" << *stream_id;
stream.Reset();
}
} else {
for (StreamID stream_id : stream_ids) {
auto it = ordered_streams_.find(stream_id);
if (it != ordered_streams_.end()) {
RTC_DLOG(LS_VERBOSE)
<< log_prefix_ << "Resetting explicit stream_id=" << *stream_id;
it->second.Reset();
}
}
}
}
HandoverReadinessStatus TraditionalReassemblyStreams::GetHandoverReadiness()
const {
HandoverReadinessStatus status;
for (const auto& [unused, stream] : ordered_streams_) {
if (stream.has_unassembled_chunks()) {
status.Add(HandoverUnreadinessReason::kOrderedStreamHasUnassembledChunks);
break;
}
}
for (const auto& [unused, stream] : unordered_streams_) {
if (stream.has_unassembled_chunks()) {
status.Add(
HandoverUnreadinessReason::kUnorderedStreamHasUnassembledChunks);
break;
}
}
return status;
}
void TraditionalReassemblyStreams::AddHandoverState(
DcSctpSocketHandoverState& state) {
for (const auto& [stream_id, stream] : ordered_streams_) {
DcSctpSocketHandoverState::OrderedStream state_stream;
state_stream.id = stream_id.value();
state_stream.next_ssn = stream.next_ssn().value();
state.rx.ordered_streams.push_back(std::move(state_stream));
}
for (const auto& [stream_id, unused] : unordered_streams_) {
DcSctpSocketHandoverState::UnorderedStream state_stream;
state_stream.id = stream_id.value();
state.rx.unordered_streams.push_back(std::move(state_stream));
}
}
void TraditionalReassemblyStreams::RestoreFromState(
const DcSctpSocketHandoverState& state) {
// Validate that the component is in pristine state.
RTC_DCHECK(ordered_streams_.empty());
RTC_DCHECK(unordered_streams_.empty());
for (const DcSctpSocketHandoverState::OrderedStream& state_stream :
state.rx.ordered_streams) {
ordered_streams_.emplace(
std::piecewise_construct,
std::forward_as_tuple(StreamID(state_stream.id)),
std::forward_as_tuple(this, SSN(state_stream.next_ssn)));
}
for (const DcSctpSocketHandoverState::UnorderedStream& state_stream :
state.rx.unordered_streams) {
unordered_streams_.emplace(std::piecewise_construct,
std::forward_as_tuple(StreamID(state_stream.id)),
std::forward_as_tuple(this));
}
}
} // namespace dcsctp
|