diff options
Diffstat (limited to 'third_party/libwebrtc/net/dcsctp/packet/sctp_packet.cc')
| -rw-r--r-- | third_party/libwebrtc/net/dcsctp/packet/sctp_packet.cc | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/third_party/libwebrtc/net/dcsctp/packet/sctp_packet.cc b/third_party/libwebrtc/net/dcsctp/packet/sctp_packet.cc new file mode 100644 index 0000000000..cc66235122 --- /dev/null +++ b/third_party/libwebrtc/net/dcsctp/packet/sctp_packet.cc @@ -0,0 +1,184 @@ +/* + * 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/sctp_packet.h" + +#include <stddef.h> + +#include <cstdint> +#include <string> +#include <utility> +#include <vector> + +#include "absl/memory/memory.h" +#include "absl/types/optional.h" +#include "api/array_view.h" +#include "net/dcsctp/common/math.h" +#include "net/dcsctp/packet/bounded_byte_reader.h" +#include "net/dcsctp/packet/bounded_byte_writer.h" +#include "net/dcsctp/packet/chunk/chunk.h" +#include "net/dcsctp/packet/crc32c.h" +#include "net/dcsctp/public/dcsctp_options.h" +#include "rtc_base/logging.h" +#include "rtc_base/strings/string_format.h" + +namespace dcsctp { +namespace { +constexpr size_t kMaxUdpPacketSize = 65535; +constexpr size_t kChunkTlvHeaderSize = 4; +constexpr size_t kExpectedDescriptorCount = 4; +} // namespace + +/* + 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Source Port Number | Destination Port Number | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Verification Tag | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +*/ + +SctpPacket::Builder::Builder(VerificationTag verification_tag, + const DcSctpOptions& options) + : verification_tag_(verification_tag), + source_port_(options.local_port), + dest_port_(options.remote_port), + max_packet_size_(RoundDownTo4(options.mtu)) {} + +SctpPacket::Builder& SctpPacket::Builder::Add(const Chunk& chunk) { + if (out_.empty()) { + out_.reserve(max_packet_size_); + out_.resize(SctpPacket::kHeaderSize); + BoundedByteWriter<kHeaderSize> buffer(out_); + buffer.Store16<0>(source_port_); + buffer.Store16<2>(dest_port_); + buffer.Store32<4>(*verification_tag_); + // Checksum is at offset 8 - written when calling Build(); + } + RTC_DCHECK(IsDivisibleBy4(out_.size())); + + chunk.SerializeTo(out_); + if (out_.size() % 4 != 0) { + out_.resize(RoundUpTo4(out_.size())); + } + + RTC_DCHECK(out_.size() <= max_packet_size_) + << "Exceeded max size, data=" << out_.size() + << ", max_size=" << max_packet_size_; + return *this; +} + +size_t SctpPacket::Builder::bytes_remaining() const { + if (out_.empty()) { + // The packet header (CommonHeader) hasn't been written yet: + return max_packet_size_ - kHeaderSize; + } else if (out_.size() > max_packet_size_) { + RTC_DCHECK_NOTREACHED() << "Exceeded max size, data=" << out_.size() + << ", max_size=" << max_packet_size_; + return 0; + } + return max_packet_size_ - out_.size(); +} + +std::vector<uint8_t> SctpPacket::Builder::Build() { + std::vector<uint8_t> out; + out_.swap(out); + + if (!out.empty()) { + uint32_t crc = GenerateCrc32C(out); + BoundedByteWriter<kHeaderSize>(out).Store32<8>(crc); + } + + RTC_DCHECK(out.size() <= max_packet_size_) + << "Exceeded max size, data=" << out.size() + << ", max_size=" << max_packet_size_; + + return out; +} + +absl::optional<SctpPacket> SctpPacket::Parse( + rtc::ArrayView<const uint8_t> data, + bool disable_checksum_verification) { + if (data.size() < kHeaderSize + kChunkTlvHeaderSize || + data.size() > kMaxUdpPacketSize) { + RTC_DLOG(LS_WARNING) << "Invalid packet size"; + return absl::nullopt; + } + + BoundedByteReader<kHeaderSize> reader(data); + + CommonHeader common_header; + common_header.source_port = reader.Load16<0>(); + common_header.destination_port = reader.Load16<2>(); + common_header.verification_tag = VerificationTag(reader.Load32<4>()); + common_header.checksum = reader.Load32<8>(); + + // Create a copy of the packet, which will be held by this object. + std::vector<uint8_t> data_copy = + std::vector<uint8_t>(data.begin(), data.end()); + + // Verify the checksum. The checksum field must be zero when that's done. + BoundedByteWriter<kHeaderSize>(data_copy).Store32<8>(0); + uint32_t calculated_checksum = GenerateCrc32C(data_copy); + if (!disable_checksum_verification && + calculated_checksum != common_header.checksum) { + RTC_DLOG(LS_WARNING) << rtc::StringFormat( + "Invalid packet checksum, packet_checksum=0x%08x, " + "calculated_checksum=0x%08x", + common_header.checksum, calculated_checksum); + return absl::nullopt; + } + // Restore the checksum in the header. + BoundedByteWriter<kHeaderSize>(data_copy).Store32<8>(common_header.checksum); + + // Validate and parse the chunk headers in the message. + /* + 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Chunk Type | Chunk Flags | Chunk Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + */ + + std::vector<ChunkDescriptor> descriptors; + descriptors.reserve(kExpectedDescriptorCount); + rtc::ArrayView<const uint8_t> descriptor_data = + rtc::ArrayView<const uint8_t>(data_copy).subview(kHeaderSize); + while (!descriptor_data.empty()) { + if (descriptor_data.size() < kChunkTlvHeaderSize) { + RTC_DLOG(LS_WARNING) << "Too small chunk"; + return absl::nullopt; + } + BoundedByteReader<kChunkTlvHeaderSize> chunk_header(descriptor_data); + uint8_t type = chunk_header.Load8<0>(); + uint8_t flags = chunk_header.Load8<1>(); + uint16_t length = chunk_header.Load16<2>(); + uint16_t padded_length = RoundUpTo4(length); + if (padded_length > descriptor_data.size()) { + RTC_DLOG(LS_WARNING) << "Too large chunk. length=" << length + << ", remaining=" << descriptor_data.size(); + return absl::nullopt; + } else if (padded_length < kChunkTlvHeaderSize) { + RTC_DLOG(LS_WARNING) << "Too small chunk. length=" << length; + return absl::nullopt; + } + descriptors.emplace_back(type, flags, + descriptor_data.subview(0, padded_length)); + descriptor_data = descriptor_data.subview(padded_length); + } + + // Note that iterators (and pointer) are guaranteed to be stable when moving a + // std::vector, and `descriptors` have pointers to within `data_copy`. + return SctpPacket(common_header, std::move(data_copy), + std::move(descriptors)); +} +} // namespace dcsctp |