| /* |
| * 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/socket/transmission_control_block.h" |
| |
| #include <algorithm> |
| #include <cstdint> |
| #include <memory> |
| #include <optional> |
| #include <string> |
| #include <utility> |
| #include <vector> |
| |
| #include "api/units/time_delta.h" |
| #include "net/dcsctp/packet/chunk/data_chunk.h" |
| #include "net/dcsctp/packet/chunk/forward_tsn_chunk.h" |
| #include "net/dcsctp/packet/chunk/idata_chunk.h" |
| #include "net/dcsctp/packet/chunk/iforward_tsn_chunk.h" |
| #include "net/dcsctp/packet/chunk/reconfig_chunk.h" |
| #include "net/dcsctp/packet/chunk/sack_chunk.h" |
| #include "net/dcsctp/packet/sctp_packet.h" |
| #include "net/dcsctp/public/dcsctp_options.h" |
| #include "net/dcsctp/public/types.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/stream_reset_handler.h" |
| #include "net/dcsctp/timer/timer.h" |
| #include "net/dcsctp/tx/retransmission_queue.h" |
| #include "net/dcsctp/tx/retransmission_timeout.h" |
| #include "rtc_base/logging.h" |
| #include "rtc_base/strings/string_builder.h" |
| |
| namespace dcsctp { |
| using ::webrtc::TimeDelta; |
| using ::webrtc::Timestamp; |
| |
| TransmissionControlBlock::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) |
| : log_prefix_(log_prefix), |
| options_(options), |
| timer_manager_(timer_manager), |
| capabilities_(capabilities), |
| callbacks_(callbacks), |
| t3_rtx_(timer_manager_.CreateTimer( |
| "t3-rtx", |
| absl::bind_front(&TransmissionControlBlock::OnRtxTimerExpiry, this), |
| TimerOptions(options.rto_initial.ToTimeDelta(), |
| TimerBackoffAlgorithm::kExponential, |
| /*max_restarts=*/std::nullopt, |
| options.max_timer_backoff_duration.has_value() |
| ? options.max_timer_backoff_duration->ToTimeDelta() |
| : TimeDelta::PlusInfinity()))), |
| delayed_ack_timer_(timer_manager_.CreateTimer( |
| "delayed-ack", |
| absl::bind_front(&TransmissionControlBlock::OnDelayedAckTimerExpiry, |
| this), |
| TimerOptions(options.delayed_ack_max_timeout.ToTimeDelta(), |
| TimerBackoffAlgorithm::kExponential, |
| /*max_restarts=*/0, |
| /*max_backoff_duration=*/TimeDelta::PlusInfinity(), |
| webrtc::TaskQueueBase::DelayPrecision::kHigh))), |
| my_verification_tag_(my_verification_tag), |
| my_initial_tsn_(my_initial_tsn), |
| peer_verification_tag_(peer_verification_tag), |
| peer_initial_tsn_(peer_initial_tsn), |
| tie_tag_(tie_tag), |
| is_connection_established_(std::move(is_connection_established)), |
| packet_sender_(packet_sender), |
| rto_(options), |
| tx_error_counter_(log_prefix, options), |
| data_tracker_(log_prefix, delayed_ack_timer_.get(), peer_initial_tsn), |
| reassembly_queue_(log_prefix, |
| options.max_receiver_window_buffer_size, |
| capabilities.message_interleaving), |
| retransmission_queue_( |
| log_prefix, |
| &callbacks_, |
| my_initial_tsn, |
| a_rwnd, |
| send_queue, |
| absl::bind_front(&TransmissionControlBlock::ObserveRTT, this), |
| [this]() { tx_error_counter_.Clear(); }, |
| *t3_rtx_, |
| options, |
| capabilities.partial_reliability, |
| capabilities.message_interleaving), |
| stream_reset_handler_(log_prefix, |
| this, |
| &timer_manager, |
| &data_tracker_, |
| &reassembly_queue_, |
| &retransmission_queue_), |
| heartbeat_handler_(log_prefix, options, this, &timer_manager_) { |
| send_queue.EnableMessageInterleaving(capabilities.message_interleaving); |
| } |
| |
| void TransmissionControlBlock::ObserveRTT(TimeDelta rtt) { |
| TimeDelta prev_rto = rto_.rto(); |
| rto_.ObserveRTT(rtt); |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ << "new rtt=" << webrtc::ToString(rtt) |
| << ", srtt=" << webrtc::ToString(rto_.srtt()) |
| << ", rto=" << webrtc::ToString(rto_.rto()) << " (" |
| << webrtc::ToString(prev_rto) << ")"; |
| t3_rtx_->set_duration(rto_.rto()); |
| |
| TimeDelta delayed_ack_tmo = std::min( |
| rto_.rto() * 0.5, options_.delayed_ack_max_timeout.ToTimeDelta()); |
| delayed_ack_timer_->set_duration(delayed_ack_tmo); |
| } |
| |
| TimeDelta TransmissionControlBlock::OnRtxTimerExpiry() { |
| Timestamp now = callbacks_.Now(); |
| RTC_DLOG(LS_INFO) << log_prefix_ << "Timer " << t3_rtx_->name() |
| << " has expired"; |
| if (cookie_echo_chunk_.has_value()) { |
| // In the COOKIE_ECHO state, let the T1-COOKIE timer trigger |
| // retransmissions, to avoid having two timers doing that. |
| RTC_DLOG(LS_VERBOSE) << "Not retransmitting as T1-cookie is active."; |
| } else { |
| if (IncrementTxErrorCounter("t3-rtx expired")) { |
| retransmission_queue_.HandleT3RtxTimerExpiry(); |
| SendBufferedPackets(now); |
| } |
| } |
| return TimeDelta::Zero(); |
| } |
| |
| TimeDelta TransmissionControlBlock::OnDelayedAckTimerExpiry() { |
| data_tracker_.HandleDelayedAckTimerExpiry(); |
| MaybeSendSack(); |
| return TimeDelta::Zero(); |
| } |
| |
| void TransmissionControlBlock::MaybeSendSack() { |
| if (data_tracker_.ShouldSendAck(/*also_if_delayed=*/false)) { |
| SctpPacket::Builder builder = PacketBuilder(); |
| builder.Add( |
| data_tracker_.CreateSelectiveAck(reassembly_queue_.remaining_bytes())); |
| Send(builder); |
| } |
| } |
| |
| void TransmissionControlBlock::MaybeSendForwardTsn(SctpPacket::Builder& builder, |
| Timestamp now) { |
| if (now >= limit_forward_tsn_until_ && |
| retransmission_queue_.ShouldSendForwardTsn(now)) { |
| if (capabilities_.message_interleaving) { |
| builder.Add(retransmission_queue_.CreateIForwardTsn()); |
| } else { |
| builder.Add(retransmission_queue_.CreateForwardTsn()); |
| } |
| // https://datatracker.ietf.org/doc/html/rfc3758 |
| // "IMPLEMENTATION NOTE: An implementation may wish to limit the number of |
| // duplicate FORWARD TSN chunks it sends by ... waiting a full RTT before |
| // sending a duplicate FORWARD TSN." |
| // "Any delay applied to the sending of FORWARD TSN chunk SHOULD NOT exceed |
| // 200ms and MUST NOT exceed 500ms". |
| limit_forward_tsn_until_ = |
| now + std::min(TimeDelta::Millis(200), rto_.srtt()); |
| } |
| } |
| |
| void TransmissionControlBlock::MaybeSendFastRetransmit() { |
| if (!retransmission_queue_.has_data_to_be_fast_retransmitted()) { |
| return; |
| } |
| |
| // https://datatracker.ietf.org/doc/html/rfc4960#section-7.2.4 |
| // "Determine how many of the earliest (i.e., lowest TSN) DATA chunks marked |
| // for retransmission will fit into a single packet, subject to constraint of |
| // the path MTU of the destination transport address to which the packet is |
| // being sent. Call this value K. Retransmit those K DATA chunks in a single |
| // packet. When a Fast Retransmit is being performed, the sender SHOULD |
| // ignore the value of cwnd and SHOULD NOT delay retransmission for this |
| // single packet." |
| |
| SctpPacket::Builder builder(peer_verification_tag_, options_); |
| auto chunks = retransmission_queue_.GetChunksForFastRetransmit( |
| builder.bytes_remaining()); |
| for (auto& [tsn, data] : chunks) { |
| if (capabilities_.message_interleaving) { |
| builder.Add(IDataChunk(tsn, std::move(data), false)); |
| } else { |
| builder.Add(DataChunk(tsn, std::move(data), false)); |
| } |
| } |
| Send(builder); |
| } |
| |
| void TransmissionControlBlock::SendBufferedPackets(SctpPacket::Builder& builder, |
| Timestamp now) { |
| for (int packet_idx = 0; packet_idx < options_.max_burst; ++packet_idx) { |
| // Only add control chunks to the first packet that is sent, if sending |
| // multiple packets in one go (as allowed by the congestion window). |
| if (packet_idx == 0) { |
| if (cookie_echo_chunk_.has_value()) { |
| // https://tools.ietf.org/html/rfc4960#section-5.1 |
| // "The COOKIE ECHO chunk can be bundled with any pending outbound DATA |
| // chunks, but it MUST be the first chunk in the packet..." |
| RTC_DCHECK(builder.empty()); |
| builder.Add(*cookie_echo_chunk_); |
| } |
| |
| // https://tools.ietf.org/html/rfc4960#section-6 |
| // "Before an endpoint transmits a DATA chunk, if any received DATA |
| // chunks have not been acknowledged (e.g., due to delayed ack), the |
| // sender should create a SACK and bundle it with the outbound DATA chunk, |
| // as long as the size of the final SCTP packet does not exceed the |
| // current MTU." |
| if (data_tracker_.ShouldSendAck(/*also_if_delayed=*/true)) { |
| builder.Add(data_tracker_.CreateSelectiveAck( |
| reassembly_queue_.remaining_bytes())); |
| } |
| MaybeSendForwardTsn(builder, now); |
| std::optional<ReConfigChunk> reconfig = |
| stream_reset_handler_.MakeStreamResetRequest(); |
| if (reconfig.has_value()) { |
| builder.Add(*reconfig); |
| } |
| } |
| |
| auto chunks = |
| retransmission_queue_.GetChunksToSend(now, builder.bytes_remaining()); |
| |
| if (!chunks.empty()) { |
| // https://datatracker.ietf.org/doc/html/rfc9260#section-8.3 |
| // Sending DATA means that the path is not idle - restart heartbeat timer. |
| heartbeat_handler_.RestartTimer(); |
| } |
| |
| bool set_immediate_sack_bit = |
| cwnd() < (options_.immediate_sack_under_cwnd_mtus * options_.mtu); |
| for (auto& [tsn, data] : chunks) { |
| if (capabilities_.message_interleaving) { |
| builder.Add(IDataChunk(tsn, std::move(data), set_immediate_sack_bit)); |
| } else { |
| builder.Add(DataChunk(tsn, std::move(data), set_immediate_sack_bit)); |
| } |
| } |
| |
| // https://www.ietf.org/archive/id/draft-tuexen-tsvwg-sctp-zero-checksum-02.html#section-4.2 |
| // "When an end point sends a packet containing a COOKIE ECHO chunk, it MUST |
| // include a correct CRC32c checksum in the packet containing the COOKIE |
| // ECHO chunk." |
| bool write_checksum = |
| !capabilities_.zero_checksum || cookie_echo_chunk_.has_value(); |
| if (!packet_sender_.Send(builder, write_checksum)) { |
| break; |
| } |
| |
| if (cookie_echo_chunk_.has_value()) { |
| // https://tools.ietf.org/html/rfc4960#section-5.1 |
| // "... until the COOKIE ACK is returned the sender MUST NOT send any |
| // other packets to the peer." |
| break; |
| } |
| } |
| } |
| |
| std::string TransmissionControlBlock::ToString() const { |
| webrtc::StringBuilder sb; |
| |
| sb.AppendFormat( |
| "verification_tag=%08x, last_cumulative_ack=%u, capabilities=", |
| *peer_verification_tag_, *data_tracker_.last_cumulative_acked_tsn()); |
| |
| if (capabilities_.partial_reliability) { |
| sb << "PR,"; |
| } |
| if (capabilities_.message_interleaving) { |
| sb << "IL,"; |
| } |
| if (capabilities_.reconfig) { |
| sb << "Reconfig,"; |
| } |
| if (capabilities_.zero_checksum) { |
| sb << "ZeroChecksum,"; |
| } |
| sb << " max_in=" << capabilities_.negotiated_maximum_incoming_streams; |
| sb << " max_out=" << capabilities_.negotiated_maximum_outgoing_streams; |
| |
| return sb.Release(); |
| } |
| |
| HandoverReadinessStatus TransmissionControlBlock::GetHandoverReadiness() const { |
| HandoverReadinessStatus status; |
| status.Add(data_tracker_.GetHandoverReadiness()); |
| status.Add(stream_reset_handler_.GetHandoverReadiness()); |
| status.Add(reassembly_queue_.GetHandoverReadiness()); |
| status.Add(retransmission_queue_.GetHandoverReadiness()); |
| return status; |
| } |
| |
| void TransmissionControlBlock::AddHandoverState( |
| DcSctpSocketHandoverState& state) { |
| state.capabilities.partial_reliability = capabilities_.partial_reliability; |
| state.capabilities.message_interleaving = capabilities_.message_interleaving; |
| state.capabilities.reconfig = capabilities_.reconfig; |
| state.capabilities.zero_checksum = capabilities_.zero_checksum; |
| state.capabilities.negotiated_maximum_incoming_streams = |
| capabilities_.negotiated_maximum_incoming_streams; |
| state.capabilities.negotiated_maximum_outgoing_streams = |
| capabilities_.negotiated_maximum_outgoing_streams; |
| |
| state.my_verification_tag = my_verification_tag().value(); |
| state.peer_verification_tag = peer_verification_tag().value(); |
| state.my_initial_tsn = my_initial_tsn().value(); |
| state.peer_initial_tsn = peer_initial_tsn().value(); |
| state.tie_tag = tie_tag().value(); |
| |
| data_tracker_.AddHandoverState(state); |
| stream_reset_handler_.AddHandoverState(state); |
| reassembly_queue_.AddHandoverState(state); |
| retransmission_queue_.AddHandoverState(state); |
| } |
| |
| void TransmissionControlBlock::RestoreFromState( |
| const DcSctpSocketHandoverState& state) { |
| data_tracker_.RestoreFromState(state); |
| retransmission_queue_.RestoreFromState(state); |
| reassembly_queue_.RestoreFromState(state); |
| } |
| } // namespace dcsctp |
