blob: a0fbb33c4748ba884b854c076bf4fa806a8aea28 [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 <map>
#include <set>
#include <string>
#include <utility>
#include <vector>
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "net/dcsctp/common/sequence_numbers.h"
#include "net/dcsctp/packet/chunk/forward_tsn_chunk.h"
#include "net/dcsctp/packet/chunk/iforward_tsn_chunk.h"
#include "net/dcsctp/packet/chunk/sack_chunk.h"
#include "net/dcsctp/packet/data.h"
#include "net/dcsctp/public/dcsctp_handover_state.h"
#include "net/dcsctp/public/dcsctp_options.h"
#include "net/dcsctp/public/dcsctp_socket.h"
#include "net/dcsctp/timer/timer.h"
#include "net/dcsctp/tx/outstanding_data.h"
#include "net/dcsctp/tx/retransmission_timeout.h"
#include "net/dcsctp/tx/send_queue.h"
namespace dcsctp {
// The RetransmissionQueue manages all DATA/I-DATA chunks that are in-flight and
// schedules them to be retransmitted if necessary. Chunks are retransmitted
// when they have been lost for a number of consecutive SACKs, or when the
// retransmission timer, `t3_rtx` expires.
// As congestion control is tightly connected with the state of transmitted
// packets, that's also managed here to limit the amount of data that is
// in-flight (sent, but not yet acknowledged).
class RetransmissionQueue {
static constexpr size_t kMinimumFragmentedPayload = 10;
using State = OutstandingData::State;
// Creates a RetransmissionQueue which will send data using `my_initial_tsn`
// (or a value from `DcSctpSocketHandoverState` if given) as the first TSN
// to use for sent fragments. It will poll data from `send_queue`. When SACKs
// are received, it will estimate the RTT, and call `on_new_rtt`. When an
// outstanding chunk has been ACKed, it will call
// `on_clear_retransmission_counter` and will also use `t3_rtx`, which is the
// SCTP retransmission timer to manage retransmissions.
RetransmissionQueue(absl::string_view log_prefix,
DcSctpSocketCallbacks* callbacks,
TSN my_initial_tsn,
size_t a_rwnd,
SendQueue& send_queue,
std::function<void(webrtc::TimeDelta rtt)> on_new_rtt,
std::function<void()> on_clear_retransmission_counter,
Timer& t3_rtx,
const DcSctpOptions& options,
bool supports_partial_reliability = true,
bool use_message_interleaving = false);
// Handles a received SACK. Returns true if the `sack` was processed and
// false if it was discarded due to received out-of-order and not relevant.
bool HandleSack(webrtc::Timestamp now, const SackChunk& sack);
// Handles an expired retransmission timer.
void HandleT3RtxTimerExpiry();
bool has_data_to_be_fast_retransmitted() const {
return outstanding_data_.has_data_to_be_fast_retransmitted();
// Returns a list of chunks to "fast retransmit" that would fit in one SCTP
// packet with `bytes_in_packet` bytes available. The current value
// of `cwnd` is ignored.
std::vector<std::pair<TSN, Data>> GetChunksForFastRetransmit(
size_t bytes_in_packet);
// Returns a list of chunks to send that would fit in one SCTP packet with
// `bytes_remaining_in_packet` bytes available. This may be further limited by
// the congestion control windows. Note that `ShouldSendForwardTSN` must be
// called prior to this method, to abandon expired chunks, as this method will
// not expire any chunks.
std::vector<std::pair<TSN, Data>> GetChunksToSend(
webrtc::Timestamp now,
size_t bytes_remaining_in_packet);
// Returns the internal state of all queued chunks. This is only used in
// unit-tests.
std::vector<std::pair<TSN, OutstandingData::State>> GetChunkStatesForTesting()
const {
return outstanding_data_.GetChunkStatesForTesting();
// Returns the next TSN that will be allocated for sent DATA chunks.
TSN next_tsn() const { return outstanding_data_.next_tsn().Wrap(); }
TSN last_assigned_tsn() const {
return UnwrappedTSN::AddTo(outstanding_data_.next_tsn(), -1).Wrap();
// Returns the size of the congestion window, in bytes. This is the number of
// bytes that may be in-flight.
size_t cwnd() const { return cwnd_; }
// Overrides the current congestion window size.
void set_cwnd(size_t cwnd) { cwnd_ = cwnd; }
// Returns the current receiver window size.
size_t rwnd() const { return rwnd_; }
size_t rtx_packets_count() const { return rtx_packets_count_; }
uint64_t rtx_bytes_count() const { return rtx_bytes_count_; }
// Returns the number of bytes of packets that are in-flight.
size_t unacked_bytes() const { return outstanding_data_.unacked_bytes(); }
// Returns the number of DATA chunks that are in-flight.
size_t unacked_items() const { return outstanding_data_.unacked_items(); }
// Indicates if the congestion control algorithm allows data to be sent.
bool can_send_data() const;
// Given the current time `now`, it will evaluate if there are chunks that
// have expired and that need to be discarded. It returns true if a
// FORWARD-TSN should be sent.
bool ShouldSendForwardTsn(webrtc::Timestamp now);
// Creates a FORWARD-TSN chunk.
ForwardTsnChunk CreateForwardTsn() const {
return outstanding_data_.CreateForwardTsn();
// Creates an I-FORWARD-TSN chunk.
IForwardTsnChunk CreateIForwardTsn() const {
return outstanding_data_.CreateIForwardTsn();
// See the SendQueue for a longer description of these methods related
// to stream resetting.
void PrepareResetStream(StreamID stream_id);
bool HasStreamsReadyToBeReset() const;
std::vector<StreamID> BeginResetStreams();
void CommitResetStreams();
void RollbackResetStreams();
HandoverReadinessStatus GetHandoverReadiness() const;
void AddHandoverState(DcSctpSocketHandoverState& state);
void RestoreFromState(const DcSctpSocketHandoverState& state);
enum class CongestionAlgorithmPhase {
bool IsConsistent() const;
// Returns how large a chunk will be, serialized, carrying the data
size_t GetSerializedChunkSize(const Data& data) const;
// Indicates if the congestion control algorithm is in "fast recovery".
bool is_in_fast_recovery() const {
return fast_recovery_exit_tsn_.has_value();
// Indicates if the provided SACK is valid given what has previously been
// received. If it returns false, the SACK is most likely a duplicate of
// something already seen, so this returning false doesn't necessarily mean
// that the SACK is illegal.
bool IsSackValid(const SackChunk& sack) const;
// When a SACK chunk is received, this method will be called which _may_ call
// into the `RetransmissionTimeout` to update the RTO.
void UpdateRTT(webrtc::Timestamp now, UnwrappedTSN cumulative_tsn_ack);
// If the congestion control is in "fast recovery mode", this may be exited
// now.
void MaybeExitFastRecovery(UnwrappedTSN cumulative_tsn_ack);
// If chunks have been ACKed, stop the retransmission timer.
void StopT3RtxTimerOnIncreasedCumulativeTsnAck(
UnwrappedTSN cumulative_tsn_ack);
// Update the congestion control algorithm given as the cumulative ack TSN
// value has increased, as reported in an incoming SACK chunk.
void HandleIncreasedCumulativeTsnAck(size_t unacked_bytes,
size_t total_bytes_acked);
// Update the congestion control algorithm, given as packet loss has been
// detected, as reported in an incoming SACK chunk.
void HandlePacketLoss(UnwrappedTSN highest_tsn_acked);
// Update the view of the receiver window size.
void UpdateReceiverWindow(uint32_t a_rwnd);
// If there is data sent and not ACKED, ensure that the retransmission timer
// is running.
void StartT3RtxTimerIfOutstandingData();
// Returns the current congestion control algorithm phase.
CongestionAlgorithmPhase phase() const {
return (cwnd_ <= ssthresh_)
? CongestionAlgorithmPhase::kSlowStart
: CongestionAlgorithmPhase::kCongestionAvoidance;
// Returns the number of bytes that may be sent in a single packet according
// to the congestion control algorithm.
size_t max_bytes_to_send() const;
DcSctpSocketCallbacks& callbacks_;
const DcSctpOptions options_;
// The minimum bytes required to be available in the congestion window to
// allow packets to be sent - to avoid sending too small packets.
const size_t min_bytes_required_to_send_;
// If the peer supports RFC3758 - SCTP Partial Reliability Extension.
const bool partial_reliability_;
const absl::string_view log_prefix_;
// The size of the data chunk (DATA/I-DATA) header that is used.
const size_t data_chunk_header_size_;
// Called when a new RTT measurement has been done
const std::function<void(webrtc::TimeDelta rtt)> on_new_rtt_;
// Called when a SACK has been seen that cleared the retransmission counter.
const std::function<void()> on_clear_retransmission_counter_;
// The retransmission counter.
Timer& t3_rtx_;
// Unwraps TSNs
UnwrappedTSN::Unwrapper tsn_unwrapper_;
// Congestion Window. Number of bytes that may be in-flight (sent, not acked).
size_t cwnd_;
// Receive Window. Number of bytes available in the receiver's RX buffer.
size_t rwnd_;
// Slow Start Threshold. See RFC4960.
size_t ssthresh_;
// Partial Bytes Acked. See RFC4960.
size_t partial_bytes_acked_;
// See `dcsctp::Metrics`.
size_t rtx_packets_count_ = 0;
uint64_t rtx_bytes_count_ = 0;
// If set, fast recovery is enabled until this TSN has been cumulative
// acked.
absl::optional<UnwrappedTSN> fast_recovery_exit_tsn_ = absl::nullopt;
// The send queue.
SendQueue& send_queue_;
// All the outstanding data chunks that are in-flight and that have not been
// cumulative acked. Note that it also contains chunks that have been acked in
// gap ack blocks.
OutstandingData outstanding_data_;
} // namespace dcsctp