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// Copyright (c) 2013 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.
// A send algorithm that adds pacing on top of an another send algorithm.
// It uses the underlying sender's pacing rate to schedule packets.
// It also takes into consideration the expected granularity of the underlying
// alarm to ensure that alarms are not set too aggressively, and err towards
// sending packets too early instead of too late.
#include <cstdint>
#include <map>
#include <memory>
#include "net/third_party/quiche/src/quic/core/congestion_control/send_algorithm_interface.h"
#include "net/third_party/quiche/src/quic/core/quic_bandwidth.h"
#include "net/third_party/quiche/src/quic/core/quic_config.h"
#include "net/third_party/quiche/src/quic/core/quic_packets.h"
#include "net/third_party/quiche/src/quic/core/quic_time.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_export.h"
namespace quic {
namespace test {
class QuicSentPacketManagerPeer;
} // namespace test
class QUIC_EXPORT_PRIVATE PacingSender {
PacingSender(const PacingSender&) = delete;
PacingSender& operator=(const PacingSender&) = delete;
// Sets the underlying sender. Does not take ownership of |sender|. |sender|
// must not be null. This must be called before any of the
// SendAlgorithmInterface wrapper methods are called.
void set_sender(SendAlgorithmInterface* sender);
void set_max_pacing_rate(QuicBandwidth max_pacing_rate) {
max_pacing_rate_ = max_pacing_rate;
void set_alarm_granularity(QuicTime::Delta alarm_granularity) {
alarm_granularity_ = alarm_granularity;
QuicBandwidth max_pacing_rate() const { return max_pacing_rate_; }
void OnCongestionEvent(bool rtt_updated,
QuicByteCount bytes_in_flight,
QuicTime event_time,
const AckedPacketVector& acked_packets,
const LostPacketVector& lost_packets);
void OnPacketSent(QuicTime sent_time,
QuicByteCount bytes_in_flight,
QuicPacketNumber packet_number,
QuicByteCount bytes,
HasRetransmittableData has_retransmittable_data);
// Called when application throttles the sending, so that pacing sender stops
// making up for lost time.
void OnApplicationLimited();
// Set burst_tokens_ and initial_burst_size_.
void SetBurstTokens(uint32_t burst_tokens);
QuicTime::Delta TimeUntilSend(QuicTime now,
QuicByteCount bytes_in_flight) const;
QuicBandwidth PacingRate(QuicByteCount bytes_in_flight) const;
QuicTime ideal_next_packet_send_time() const {
return ideal_next_packet_send_time_;
friend class test::QuicSentPacketManagerPeer;
// Underlying sender. Not owned.
SendAlgorithmInterface* sender_;
// If not QuicBandidth::Zero, the maximum rate the PacingSender will use.
QuicBandwidth max_pacing_rate_;
// Number of unpaced packets to be sent before packets are delayed.
uint32_t burst_tokens_;
QuicTime ideal_next_packet_send_time_; // When can the next packet be sent.
uint32_t initial_burst_size_;
// Number of unpaced packets to be sent before packets are delayed. This token
// is consumed after burst_tokens_ ran out.
uint32_t lumpy_tokens_;
// If the next send time is within alarm_granularity_, send immediately.
// TODO(fayang): Remove alarm_granularity_ when deprecating
// quic_offload_pacing_to_usps2 flag.
QuicTime::Delta alarm_granularity_;
// Indicates whether pacing throttles the sending. If true, make up for lost
// time.
bool pacing_limited_;
// Latched value of --quic_lumpy_pacing_size.
const int32_t lumpy_pacing_size_;
} // namespace quic