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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_validators.h"
#include <algorithm>
#include <utility>
#include <vector>
#include "net/dcsctp/packet/chunk/sack_chunk.h"
#include "rtc_base/logging.h"
namespace dcsctp {
SackChunk ChunkValidators::Clean(SackChunk&& sack) {
if (Validate(sack)) {
return std::move(sack);
}
RTC_DLOG(LS_WARNING) << "Received SACK is malformed; cleaning it";
std::vector<SackChunk::GapAckBlock> gap_ack_blocks;
gap_ack_blocks.reserve(sack.gap_ack_blocks().size());
// First: Only keep blocks that are sane
for (const SackChunk::GapAckBlock& gap_ack_block : sack.gap_ack_blocks()) {
if (gap_ack_block.end > gap_ack_block.start) {
gap_ack_blocks.emplace_back(gap_ack_block);
}
}
// Not more than at most one remaining? Exit early.
if (gap_ack_blocks.size() <= 1) {
return SackChunk(sack.cumulative_tsn_ack(), sack.a_rwnd(),
std::move(gap_ack_blocks), sack.duplicate_tsns());
}
// Sort the intervals by their start value, to aid in the merging below.
absl::c_sort(gap_ack_blocks, [&](const SackChunk::GapAckBlock& a,
const SackChunk::GapAckBlock& b) {
return a.start < b.start;
});
// Merge overlapping ranges.
std::vector<SackChunk::GapAckBlock> merged;
merged.reserve(gap_ack_blocks.size());
merged.push_back(gap_ack_blocks[0]);
for (size_t i = 1; i < gap_ack_blocks.size(); ++i) {
if (merged.back().end + 1 >= gap_ack_blocks[i].start) {
merged.back().end = std::max(merged.back().end, gap_ack_blocks[i].end);
} else {
merged.push_back(gap_ack_blocks[i]);
}
}
return SackChunk(sack.cumulative_tsn_ack(), sack.a_rwnd(), std::move(merged),
sack.duplicate_tsns());
}
bool ChunkValidators::Validate(const SackChunk& sack) {
if (sack.gap_ack_blocks().empty()) {
return true;
}
// Ensure that gap-ack-blocks are sorted, has an "end" that is not before
// "start" and are non-overlapping and non-adjacent.
uint16_t prev_end = 0;
for (const SackChunk::GapAckBlock& gap_ack_block : sack.gap_ack_blocks()) {
if (gap_ack_block.end < gap_ack_block.start) {
return false;
}
if (gap_ack_block.start <= (prev_end + 1)) {
return false;
}
prev_end = gap_ack_block.end;
}
return true;
}
} // namespace dcsctp
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