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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// The pure virtual class for send side congestion control algorithm.
#include <algorithm>
#include <map>
#include <string>
#include "quiche/quic/core/crypto/quic_random.h"
#include "quiche/quic/core/quic_bandwidth.h"
#include "quiche/quic/core/quic_clock.h"
#include "quiche/quic/core/quic_config.h"
#include "quiche/quic/core/quic_connection_stats.h"
#include "quiche/quic/core/quic_packets.h"
#include "quiche/quic/core/quic_time.h"
#include "quiche/quic/core/quic_types.h"
#include "quiche/quic/core/quic_unacked_packet_map.h"
#include "quiche/quic/platform/api/quic_export.h"
namespace quic {
using QuicRoundTripCount = uint64_t;
class CachedNetworkParameters;
class RttStats;
class QUIC_EXPORT_PRIVATE SendAlgorithmInterface {
// Network Params for AdjustNetworkParameters.
struct QUIC_NO_EXPORT NetworkParams {
NetworkParams() = default;
NetworkParams(const QuicBandwidth& bandwidth, const QuicTime::Delta& rtt,
bool allow_cwnd_to_decrease)
: bandwidth(bandwidth),
allow_cwnd_to_decrease(allow_cwnd_to_decrease) {}
bool operator==(const NetworkParams& other) const {
return bandwidth == other.bandwidth && rtt == other.rtt &&
max_initial_congestion_window ==
other.max_initial_congestion_window &&
allow_cwnd_to_decrease == other.allow_cwnd_to_decrease &&
is_rtt_trusted == other.is_rtt_trusted;
QuicBandwidth bandwidth = QuicBandwidth::Zero();
QuicTime::Delta rtt = QuicTime::Delta::Zero();
int max_initial_congestion_window = 0;
bool allow_cwnd_to_decrease = false;
bool is_rtt_trusted = false;
static SendAlgorithmInterface* Create(
const QuicClock* clock, const RttStats* rtt_stats,
const QuicUnackedPacketMap* unacked_packets, CongestionControlType type,
QuicRandom* random, QuicConnectionStats* stats,
QuicPacketCount initial_congestion_window,
SendAlgorithmInterface* old_send_algorithm);
virtual ~SendAlgorithmInterface() {}
virtual void SetFromConfig(const QuicConfig& config,
Perspective perspective) = 0;
virtual void ApplyConnectionOptions(
const QuicTagVector& connection_options) = 0;
// Sets the initial congestion window in number of packets. May be ignored
// if called after the initial congestion window is no longer relevant.
virtual void SetInitialCongestionWindowInPackets(QuicPacketCount packets) = 0;
// Indicates an update to the congestion state, caused either by an incoming
// ack or loss event timeout. |rtt_updated| indicates whether a new
// latest_rtt sample has been taken, |prior_in_flight| the bytes in flight
// prior to the congestion event. |acked_packets| and |lost_packets| are any
// packets considered acked or lost as a result of the congestion event.
virtual void OnCongestionEvent(bool rtt_updated,
QuicByteCount prior_in_flight,
QuicTime event_time,
const AckedPacketVector& acked_packets,
const LostPacketVector& lost_packets) = 0;
// Inform that we sent |bytes| to the wire, and if the packet is
// retransmittable. |bytes_in_flight| is the number of bytes in flight before
// the packet was sent.
// Note: this function must be called for every packet sent to the wire.
virtual void OnPacketSent(QuicTime sent_time, QuicByteCount bytes_in_flight,
QuicPacketNumber packet_number, QuicByteCount bytes,
HasRetransmittableData is_retransmittable) = 0;
// Inform that |packet_number| has been neutered.
virtual void OnPacketNeutered(QuicPacketNumber packet_number) = 0;
// Called when the retransmission timeout fires. Neither OnPacketAbandoned
// nor OnPacketLost will be called for these packets.
virtual void OnRetransmissionTimeout(bool packets_retransmitted) = 0;
// Called when connection migrates and cwnd needs to be reset.
virtual void OnConnectionMigration() = 0;
// Make decision on whether the sender can send right now. Note that even
// when this method returns true, the sending can be delayed due to pacing.
virtual bool CanSend(QuicByteCount bytes_in_flight) = 0;
// The pacing rate of the send algorithm. May be zero if the rate is unknown.
virtual QuicBandwidth PacingRate(QuicByteCount bytes_in_flight) const = 0;
// What's the current estimated bandwidth in bytes per second.
// Returns 0 when it does not have an estimate.
virtual QuicBandwidth BandwidthEstimate() const = 0;
// Whether BandwidthEstimate returns a good measurement for resumption.
virtual bool HasGoodBandwidthEstimateForResumption() const = 0;
// Returns the size of the current congestion window in bytes. Note, this is
// not the *available* window. Some send algorithms may not use a congestion
// window and will return 0.
virtual QuicByteCount GetCongestionWindow() const = 0;
// Whether the send algorithm is currently in slow start. When true, the
// BandwidthEstimate is expected to be too low.
virtual bool InSlowStart() const = 0;
// Whether the send algorithm is currently in recovery.
virtual bool InRecovery() const = 0;
// True when the congestion control is probing for more bandwidth and needs
// enough data to not be app-limited to do so.
// TODO(ianswett): In the future, this API may want to indicate the size of
// the probing packet.
virtual bool ShouldSendProbingPacket() const = 0;
// Returns the size of the slow start congestion window in bytes,
// aka ssthresh. Only defined for Cubic and Reno, other algorithms return 0.
virtual QuicByteCount GetSlowStartThreshold() const = 0;
virtual CongestionControlType GetCongestionControlType() const = 0;
// Notifies the congestion control algorithm of an external network
// measurement or prediction. Either |bandwidth| or |rtt| may be zero if no
// sample is available.
virtual void AdjustNetworkParameters(const NetworkParams& params) = 0;
// Retrieves debugging information about the current state of the
// send algorithm.
virtual std::string GetDebugState() const = 0;
// Called when the connection has no outstanding data to send. Specifically,
// this means that none of the data streams are write-blocked, there are no
// packets in the connection queue, and there are no pending retransmissins,
// i.e. the sender cannot send anything for reasons other than being blocked
// by congestion controller. This includes cases when the connection is
// blocked by the flow controller.
// The fact that this method is called does not necessarily imply that the
// connection would not be blocked by the congestion control if it actually
// tried to send data. If the congestion control algorithm needs to exclude
// such cases, it should use the internal state it uses for congestion control
// for that.
virtual void OnApplicationLimited(QuicByteCount bytes_in_flight) = 0;
// Called before connection close to collect stats.
virtual void PopulateConnectionStats(QuicConnectionStats* stats) const = 0;
} // namespace quic