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/*
* 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/packet/chunk/sack_chunk.h"
#include <stddef.h>
#include <cstdint>
#include <string>
#include <type_traits>
#include <vector>
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "net/dcsctp/common/str_join.h"
#include "net/dcsctp/packet/bounded_byte_reader.h"
#include "net/dcsctp/packet/bounded_byte_writer.h"
#include "net/dcsctp/packet/tlv_trait.h"
#include "rtc_base/logging.h"
#include "rtc_base/strings/string_builder.h"
namespace dcsctp {
// https://tools.ietf.org/html/rfc4960#section-3.3.4
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Type = 3 |Chunk Flags | Chunk Length |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Cumulative TSN Ack |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Advertised Receiver Window Credit (a_rwnd) |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Number of Gap Ack Blocks = N | Number of Duplicate TSNs = X |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Gap Ack Block #1 Start | Gap Ack Block #1 End |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// / /
// \ ... \
// / /
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Gap Ack Block #N Start | Gap Ack Block #N End |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Duplicate TSN 1 |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// / /
// \ ... \
// / /
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Duplicate TSN X |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
constexpr int SackChunk::kType;
absl::optional<SackChunk> SackChunk::Parse(rtc::ArrayView<const uint8_t> data) {
absl::optional<BoundedByteReader<kHeaderSize>> reader = ParseTLV(data);
if (!reader.has_value()) {
return absl::nullopt;
}
TSN tsn_ack(reader->Load32<4>());
uint32_t a_rwnd = reader->Load32<8>();
uint16_t nbr_of_gap_blocks = reader->Load16<12>();
uint16_t nbr_of_dup_tsns = reader->Load16<14>();
if (reader->variable_data_size() != nbr_of_gap_blocks * kGapAckBlockSize +
nbr_of_dup_tsns * kDupTsnBlockSize) {
RTC_DLOG(LS_WARNING) << "Invalid number of gap blocks or duplicate TSNs";
return absl::nullopt;
}
std::vector<GapAckBlock> gap_ack_blocks;
gap_ack_blocks.reserve(nbr_of_gap_blocks);
size_t offset = 0;
for (int i = 0; i < nbr_of_gap_blocks; ++i) {
BoundedByteReader<kGapAckBlockSize> sub_reader =
reader->sub_reader<kGapAckBlockSize>(offset);
uint16_t start = sub_reader.Load16<0>();
uint16_t end = sub_reader.Load16<2>();
gap_ack_blocks.emplace_back(start, end);
offset += kGapAckBlockSize;
}
std::vector<TSN> duplicate_tsns;
duplicate_tsns.reserve(nbr_of_gap_blocks);
for (int i = 0; i < nbr_of_dup_tsns; ++i) {
BoundedByteReader<kDupTsnBlockSize> sub_reader =
reader->sub_reader<kDupTsnBlockSize>(offset);
duplicate_tsns.push_back(TSN(sub_reader.Load32<0>()));
offset += kDupTsnBlockSize;
}
RTC_DCHECK(offset == reader->variable_data_size());
return SackChunk(tsn_ack, a_rwnd, gap_ack_blocks, duplicate_tsns);
}
void SackChunk::SerializeTo(std::vector<uint8_t>& out) const {
int nbr_of_gap_blocks = gap_ack_blocks_.size();
int nbr_of_dup_tsns = duplicate_tsns_.size();
size_t variable_size =
nbr_of_gap_blocks * kGapAckBlockSize + nbr_of_dup_tsns * kDupTsnBlockSize;
BoundedByteWriter<kHeaderSize> writer = AllocateTLV(out, variable_size);
writer.Store32<4>(*cumulative_tsn_ack_);
writer.Store32<8>(a_rwnd_);
writer.Store16<12>(nbr_of_gap_blocks);
writer.Store16<14>(nbr_of_dup_tsns);
size_t offset = 0;
for (int i = 0; i < nbr_of_gap_blocks; ++i) {
BoundedByteWriter<kGapAckBlockSize> sub_writer =
writer.sub_writer<kGapAckBlockSize>(offset);
sub_writer.Store16<0>(gap_ack_blocks_[i].start);
sub_writer.Store16<2>(gap_ack_blocks_[i].end);
offset += kGapAckBlockSize;
}
for (int i = 0; i < nbr_of_dup_tsns; ++i) {
BoundedByteWriter<kDupTsnBlockSize> sub_writer =
writer.sub_writer<kDupTsnBlockSize>(offset);
sub_writer.Store32<0>(*duplicate_tsns_[i]);
offset += kDupTsnBlockSize;
}
RTC_DCHECK(offset == variable_size);
}
std::string SackChunk::ToString() const {
rtc::StringBuilder sb;
sb << "SACK, cum_ack_tsn=" << *cumulative_tsn_ack()
<< ", a_rwnd=" << a_rwnd();
for (const GapAckBlock& gap : gap_ack_blocks_) {
uint32_t first = *cumulative_tsn_ack_ + gap.start;
uint32_t last = *cumulative_tsn_ack_ + gap.end;
sb << ", gap=" << first << "--" << last;
}
if (!duplicate_tsns_.empty()) {
sb << ", dup_tsns="
<< StrJoin(duplicate_tsns(), ",",
[](rtc::StringBuilder& sb, TSN tsn) { sb << *tsn; });
}
return sb.Release();
}
} // namespace dcsctp
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