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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.
*/
#include "net/dcsctp/socket/transmission_control_block.h"
#include <algorithm>
#include <cstdint>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "absl/types/optional.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/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 {
void TransmissionControlBlock::ObserveRTT(DurationMs rtt) {
DurationMs prev_rto = rto_.rto();
rto_.ObserveRTT(rtt);
RTC_DLOG(LS_VERBOSE) << log_prefix_ << "new rtt=" << *rtt
<< ", srtt=" << *rto_.srtt() << ", rto=" << *rto_.rto()
<< " (" << *prev_rto << ")";
t3_rtx_->set_duration(rto_.rto());
DurationMs delayed_ack_tmo =
std::min(rto_.rto() * 0.5, options_.delayed_ack_max_timeout);
delayed_ack_timer_->set_duration(delayed_ack_tmo);
}
absl::optional<DurationMs> TransmissionControlBlock::OnRtxTimerExpiry() {
TimeMs now = callbacks_.TimeMillis();
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 absl::nullopt;
}
absl::optional<DurationMs> TransmissionControlBlock::OnDelayedAckTimerExpiry() {
data_tracker_.HandleDelayedAckTimerExpiry();
MaybeSendSack();
return absl::nullopt;
}
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::SendBufferedPackets(SctpPacket::Builder& builder,
TimeMs now) {
for (int packet_idx = 0;; ++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()));
}
if (retransmission_queue_.ShouldSendForwardTsn(now)) {
if (capabilities_.message_interleaving) {
builder.Add(retransmission_queue_.CreateIForwardTsn());
} else {
builder.Add(retransmission_queue_.CreateForwardTsn());
}
}
absl::optional<ReConfigChunk> reconfig =
stream_reset_handler_.MakeStreamResetRequest();
if (reconfig.has_value()) {
builder.Add(*reconfig);
}
}
auto chunks =
retransmission_queue_.GetChunksToSend(now, builder.bytes_remaining());
for (auto& elem : chunks) {
TSN tsn = elem.first;
Data data = std::move(elem.second);
if (capabilities_.message_interleaving) {
builder.Add(IDataChunk(tsn, std::move(data), false));
} else {
builder.Add(DataChunk(tsn, std::move(data), false));
}
}
if (builder.empty()) {
break;
}
Send(builder);
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 {
rtc::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,";
}
return sb.Release();
}
} // namespace dcsctp
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