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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.
*/
#ifndef NET_DCSCTP_PACKET_SCTP_PACKET_H_
#define NET_DCSCTP_PACKET_SCTP_PACKET_H_
#include <stddef.h>
#include <cstdint>
#include <functional>
#include <memory>
#include <utility>
#include <vector>
#include "api/array_view.h"
#include "net/dcsctp/common/internal_types.h"
#include "net/dcsctp/packet/chunk/chunk.h"
#include "net/dcsctp/public/dcsctp_options.h"
namespace dcsctp {
// The "Common Header", which every SCTP packet starts with, and is described in
// https://tools.ietf.org/html/rfc4960#section-3.1.
struct CommonHeader {
uint16_t source_port;
uint16_t destination_port;
VerificationTag verification_tag;
uint32_t checksum;
};
// Represents an immutable (received or to-be-sent) SCTP packet.
class SctpPacket {
public:
static constexpr size_t kHeaderSize = 12;
struct ChunkDescriptor {
ChunkDescriptor(uint8_t type,
uint8_t flags,
rtc::ArrayView<const uint8_t> data)
: type(type), flags(flags), data(data) {}
uint8_t type;
uint8_t flags;
rtc::ArrayView<const uint8_t> data;
};
SctpPacket(SctpPacket&& other) = default;
SctpPacket& operator=(SctpPacket&& other) = default;
SctpPacket(const SctpPacket&) = delete;
SctpPacket& operator=(const SctpPacket&) = delete;
// Used for building SctpPacket, as those are immutable.
class Builder {
public:
Builder(VerificationTag verification_tag, const DcSctpOptions& options);
Builder(Builder&& other) = default;
Builder& operator=(Builder&& other) = default;
// Adds a chunk to the to-be-built SCTP packet.
Builder& Add(const Chunk& chunk);
// The number of bytes remaining in the packet for chunk storage until the
// packet reaches its maximum size.
size_t bytes_remaining() const;
// Indicates if any packets have been added to the builder.
bool empty() const { return out_.empty(); }
// Returns the payload of the build SCTP packet. The Builder will be cleared
// after having called this function, and can be used to build a new packet.
// If `write_checksum` is set to false, a value of zero (0) will be written
// as the packet's checksum, instead of the crc32c value.
std::vector<uint8_t> Build(bool write_checksum = true);
private:
VerificationTag verification_tag_;
uint16_t source_port_;
uint16_t dest_port_;
// The maximum packet size is always even divisible by four, as chunks are
// always padded to a size even divisible by four.
size_t max_packet_size_;
std::vector<uint8_t> out_;
};
// Parses `data` as an SCTP packet and returns it if it validates.
static absl::optional<SctpPacket> Parse(rtc::ArrayView<const uint8_t> data,
const DcSctpOptions& options);
// Returns the SCTP common header.
const CommonHeader& common_header() const { return common_header_; }
// Returns the chunks (types and offsets) within the packet.
rtc::ArrayView<const ChunkDescriptor> descriptors() const {
return descriptors_;
}
private:
SctpPacket(const CommonHeader& common_header,
std::vector<uint8_t> data,
std::vector<ChunkDescriptor> descriptors)
: common_header_(common_header),
data_(std::move(data)),
descriptors_(std::move(descriptors)) {}
CommonHeader common_header_;
// As the `descriptors_` refer to offset within data, and since SctpPacket is
// movable, `data` needs to be pointer stable, which it is according to
// http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#2321
std::vector<uint8_t> data_;
// The chunks and their offsets within `data_ `.
std::vector<ChunkDescriptor> descriptors_;
};
} // namespace dcsctp
#endif // NET_DCSCTP_PACKET_SCTP_PACKET_H_
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