blob: f8b2445525cf6746dfac1d0f147f778081cf4ce6 [file] [log] [blame]
* 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 <cstdint>
#include <functional>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "absl/functional/bind_front.h"
#include "absl/strings/string_view.h"
#include "api/task_queue/task_queue_base.h"
#include "net/dcsctp/common/sequence_numbers.h"
#include "net/dcsctp/packet/chunk/cookie_echo_chunk.h"
#include "net/dcsctp/packet/sctp_packet.h"
#include "net/dcsctp/public/dcsctp_options.h"
#include "net/dcsctp/public/dcsctp_socket.h"
#include "net/dcsctp/rx/data_tracker.h"
#include "net/dcsctp/rx/reassembly_queue.h"
#include "net/dcsctp/socket/capabilities.h"
#include "net/dcsctp/socket/context.h"
#include "net/dcsctp/socket/heartbeat_handler.h"
#include "net/dcsctp/socket/packet_sender.h"
#include "net/dcsctp/socket/stream_reset_handler.h"
#include "net/dcsctp/timer/timer.h"
#include "net/dcsctp/tx/retransmission_error_counter.h"
#include "net/dcsctp/tx/retransmission_queue.h"
#include "net/dcsctp/tx/retransmission_timeout.h"
#include "net/dcsctp/tx/send_queue.h"
namespace dcsctp {
// The TransmissionControlBlock (TCB) represents an open connection to a peer,
// and holds all the resources for that. If the connection is e.g. shutdown,
// closed or restarted, this object will be deleted and/or replaced.
class TransmissionControlBlock : public Context {
TransmissionControlBlock(TimerManager& timer_manager,
absl::string_view log_prefix,
const DcSctpOptions& options,
const Capabilities& capabilities,
DcSctpSocketCallbacks& callbacks,
SendQueue& send_queue,
VerificationTag my_verification_tag,
TSN my_initial_tsn,
VerificationTag peer_verification_tag,
TSN peer_initial_tsn,
size_t a_rwnd,
TieTag tie_tag,
PacketSender& packet_sender,
std::function<bool()> is_connection_established);
// Implementation of `Context`.
bool is_connection_established() const override {
return is_connection_established_();
TSN my_initial_tsn() const override { return my_initial_tsn_; }
TSN peer_initial_tsn() const override { return peer_initial_tsn_; }
DcSctpSocketCallbacks& callbacks() const override { return callbacks_; }
void ObserveRTT(webrtc::TimeDelta rtt) override;
webrtc::TimeDelta current_rto() const override { return rto_.rto(); }
bool IncrementTxErrorCounter(absl::string_view reason) override {
return tx_error_counter_.Increment(reason);
void ClearTxErrorCounter() override { tx_error_counter_.Clear(); }
SctpPacket::Builder PacketBuilder() const override {
return SctpPacket::Builder(peer_verification_tag_, options_);
bool HasTooManyTxErrors() const override {
return tx_error_counter_.IsExhausted();
void Send(SctpPacket::Builder& builder) override {
// Other accessors
DataTracker& data_tracker() { return data_tracker_; }
ReassemblyQueue& reassembly_queue() { return reassembly_queue_; }
RetransmissionQueue& retransmission_queue() { return retransmission_queue_; }
StreamResetHandler& stream_reset_handler() { return stream_reset_handler_; }
HeartbeatHandler& heartbeat_handler() { return heartbeat_handler_; }
size_t cwnd() const { return retransmission_queue_.cwnd(); }
webrtc::TimeDelta current_srtt() const { return rto_.srtt(); }
// Returns this socket's verification tag, set in all packet headers.
VerificationTag my_verification_tag() const { return my_verification_tag_; }
// Returns the peer's verification tag, which should be in received packets.
VerificationTag peer_verification_tag() const {
return peer_verification_tag_;
// All negotiated supported capabilities.
const Capabilities& capabilities() const { return capabilities_; }
// A 64-bit tie-tag, used to e.g. detect reconnections.
TieTag tie_tag() const { return tie_tag_; }
// Sends a SACK, if there is a need to.
void MaybeSendSack();
// Sends a FORWARD-TSN, if it is needed and allowed (rate-limited).
void MaybeSendForwardTsn(SctpPacket::Builder& builder, webrtc::Timestamp now);
// Will be set while the socket is in kCookieEcho state. In this state, there
// can only be a single packet outstanding, and it must contain the COOKIE
// ECHO chunk as the first chunk in that packet, until the COOKIE ACK has been
// received, which will make the socket call `ClearCookieEchoChunk`.
void SetCookieEchoChunk(CookieEchoChunk chunk) {
cookie_echo_chunk_ = std::move(chunk);
// Called when the COOKIE ACK chunk has been received, to allow further
// packets to be sent.
void ClearCookieEchoChunk() { cookie_echo_chunk_ = absl::nullopt; }
bool has_cookie_echo_chunk() const { return cookie_echo_chunk_.has_value(); }
void MaybeSendFastRetransmit();
// Fills `builder` (which may already be filled with control chunks) with
// other control and data chunks, and sends packets as much as can be
// allowed by the congestion control algorithm.
void SendBufferedPackets(SctpPacket::Builder& builder, webrtc::Timestamp now);
// As above, but without passing in a builder. If `cookie_echo_chunk_` is
// present, then only one packet will be sent, with this chunk as the first
// chunk.
void SendBufferedPackets(webrtc::Timestamp now) {
SctpPacket::Builder builder(peer_verification_tag_, options_);
SendBufferedPackets(builder, now);
// Returns a textual representation of this object, for logging.
std::string ToString() const;
HandoverReadinessStatus GetHandoverReadiness() const;
void AddHandoverState(DcSctpSocketHandoverState& state);
void RestoreFromState(const DcSctpSocketHandoverState& handover_state);
// Will be called when the retransmission timer (t3-rtx) expires.
webrtc::TimeDelta OnRtxTimerExpiry();
// Will be called when the delayed ack timer expires.
webrtc::TimeDelta OnDelayedAckTimerExpiry();
const absl::string_view log_prefix_;
const DcSctpOptions options_;
TimerManager& timer_manager_;
// Negotiated capabilities that both peers support.
const Capabilities capabilities_;
DcSctpSocketCallbacks& callbacks_;
// The data retransmission timer, called t3-rtx in SCTP.
const std::unique_ptr<Timer> t3_rtx_;
// Delayed ack timer, which triggers when acks should be sent (when delayed).
const std::unique_ptr<Timer> delayed_ack_timer_;
const VerificationTag my_verification_tag_;
const TSN my_initial_tsn_;
const VerificationTag peer_verification_tag_;
const TSN peer_initial_tsn_;
// Nonce, used to detect reconnections.
const TieTag tie_tag_;
const std::function<bool()> is_connection_established_;
PacketSender& packet_sender_;
// Rate limiting of FORWARD-TSN. Next can be sent at or after this timestamp.
webrtc::Timestamp limit_forward_tsn_until_ = webrtc::Timestamp::Zero();
RetransmissionTimeout rto_;
RetransmissionErrorCounter tx_error_counter_;
DataTracker data_tracker_;
ReassemblyQueue reassembly_queue_;
RetransmissionQueue retransmission_queue_;
StreamResetHandler stream_reset_handler_;
HeartbeatHandler heartbeat_handler_;
// Only valid when the socket state == State::kCookieEchoed. In this state,
// the socket must wait for COOKIE ACK to continue sending any packets (not
// including a COOKIE ECHO). So if `cookie_echo_chunk_` is present, the
// SendBufferedChunks will always only just send one packet, with this chunk
// as the first chunk in the packet.
absl::optional<CookieEchoChunk> cookie_echo_chunk_ = absl::nullopt;
} // namespace dcsctp