1 files changed, 87 insertions, 0 deletions
diff --git a/third_party/libwebrtc/net/dcsctp/packet/chunk_validators.cc b/third_party/libwebrtc/net/dcsctp/packet/chunk_validators.cc
new file mode 100644
index 0000000000..48d351827e
--- /dev/null
+++ b/third_party/libwebrtc/net/dcsctp/packet/chunk_validators.cc
@@ -0,0 +1,87 @@
+/*
+ *  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