net/quic/congestion_control/pacing_sender.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/quic/congestion_control/pacing_sender.h"
   6
   7 namespace net {
   8
   9 PacingSender::PacingSender(SendAlgorithmInterface* sender,
  10                            QuicTime::Delta alarm_granularity,
  11                            uint32 initial_packet_burst)
  12     : sender_(sender),
  13       alarm_granularity_(alarm_granularity),
  14       initial_packet_burst_(initial_packet_burst),
  15       burst_tokens_(initial_packet_burst),
  16       last_delayed_packet_sent_time_(QuicTime::Zero()),
  17       ideal_next_packet_send_time_(QuicTime::Zero()),
  18       was_last_send_delayed_(false) {
  19 }
  20
  21 PacingSender::~PacingSender() {}
  22
  23 void PacingSender::SetFromConfig(const QuicConfig& config,
  24                                  Perspective perspective) {
  25   sender_->SetFromConfig(config, perspective);
  26 }
  27
  28 bool PacingSender::ResumeConnectionState(
  29     const CachedNetworkParameters& cached_network_params,
  30     bool max_bandwidth_resumption) {
  31   return sender_->ResumeConnectionState(cached_network_params,
  32                                         max_bandwidth_resumption);
  33 }
  34
  35 void PacingSender::SetNumEmulatedConnections(int num_connections) {
  36   sender_->SetNumEmulatedConnections(num_connections);
  37 }
  38
  39 void PacingSender::SetMaxCongestionWindow(QuicByteCount max_congestion_window) {
  40   sender_->SetMaxCongestionWindow(max_congestion_window);
  41 }
  42
  43 void PacingSender::OnCongestionEvent(bool rtt_updated,
  44                                      QuicByteCount bytes_in_flight,
  45                                      const CongestionVector& acked_packets,
  46                                      const CongestionVector& lost_packets) {
  47   sender_->OnCongestionEvent(
  48       rtt_updated, bytes_in_flight, acked_packets, lost_packets);
  49 }
  50
  51 bool PacingSender::OnPacketSent(
  52     QuicTime sent_time,
  53     QuicByteCount bytes_in_flight,
  54     QuicPacketSequenceNumber sequence_number,
  55     QuicByteCount bytes,
  56     HasRetransmittableData has_retransmittable_data) {
  57   const bool in_flight =
  58       sender_->OnPacketSent(sent_time, bytes_in_flight, sequence_number,
  59                             bytes, has_retransmittable_data);
  60   if (has_retransmittable_data != HAS_RETRANSMITTABLE_DATA) {
  61     return in_flight;
  62   }
  63   if (bytes_in_flight == 0) {
  64     // Add more burst tokens anytime the connection is leaving quiescence.
  65     burst_tokens_ = initial_packet_burst_;
  66   }
  67   if (burst_tokens_ > 0) {
  68     --burst_tokens_;
  69     was_last_send_delayed_ = false;
  70     last_delayed_packet_sent_time_ = QuicTime::Zero();
  71     ideal_next_packet_send_time_ = QuicTime::Zero();
  72     return in_flight;
  73   }
  74   // The next packet should be sent as soon as the current packets has been
  75   // transferred.
  76   QuicTime::Delta delay = PacingRate().TransferTime(bytes);
  77   // If the last send was delayed, and the alarm took a long time to get
  78   // invoked, allow the connection to make up for lost time.
  79   if (was_last_send_delayed_) {
  80     ideal_next_packet_send_time_ = ideal_next_packet_send_time_.Add(delay);
  81     // The send was application limited if it takes longer than the
  82     // pacing delay between sent packets.
  83     const bool application_limited =
  84         last_delayed_packet_sent_time_.IsInitialized() &&
  85         sent_time > last_delayed_packet_sent_time_.Add(delay);
  86     const bool making_up_for_lost_time =
  87         ideal_next_packet_send_time_ <= sent_time;
  88     // As long as we're making up time and not application limited,
  89     // continue to consider the packets delayed, allowing the packets to be
  90     // sent immediately.
  91     if (making_up_for_lost_time && !application_limited) {
  92       last_delayed_packet_sent_time_ = sent_time;
  93     } else {
  94       was_last_send_delayed_ = false;
  95       last_delayed_packet_sent_time_ = QuicTime::Zero();
  96     }
  97   } else {
  98     ideal_next_packet_send_time_ = QuicTime::Max(
  99         ideal_next_packet_send_time_.Add(delay), sent_time.Add(delay));
 100   }
 101   return in_flight;
 102 }
 103
 104 void PacingSender::OnRetransmissionTimeout(bool packets_retransmitted) {
 105   sender_->OnRetransmissionTimeout(packets_retransmitted);
 106 }
 107
 108 QuicTime::Delta PacingSender::TimeUntilSend(
 109       QuicTime now,
 110       QuicByteCount bytes_in_flight,
 111       HasRetransmittableData has_retransmittable_data) const {
 112   QuicTime::Delta time_until_send =
 113       sender_->TimeUntilSend(now, bytes_in_flight, has_retransmittable_data);
 114   if (burst_tokens_ > 0 || bytes_in_flight == 0) {
 115     // Don't pace if we have burst tokens available or leaving quiescence.
 116     return time_until_send;
 117   }
 118
 119   if (!time_until_send.IsZero()) {
 120     DCHECK(time_until_send.IsInfinite());
 121     // The underlying sender prevents sending.
 122     return time_until_send;
 123   }
 124
 125   if (has_retransmittable_data == NO_RETRANSMITTABLE_DATA) {
 126     // Don't pace ACK packets, since they do not count against CWND and do not
 127     // cause CWND to grow.
 128     return QuicTime::Delta::Zero();
 129   }
 130
 131   // If the next send time is within the alarm granularity, send immediately.
 132   if (ideal_next_packet_send_time_ > now.Add(alarm_granularity_)) {
 133     DVLOG(1) << "Delaying packet: "
 134              << ideal_next_packet_send_time_.Subtract(now).ToMicroseconds();
 135     was_last_send_delayed_ = true;
 136     return ideal_next_packet_send_time_.Subtract(now);
 137   }
 138
 139   DVLOG(1) << "Sending packet now";
 140   return QuicTime::Delta::Zero();
 141 }
 142
 143 QuicBandwidth PacingSender::PacingRate() const {
 144   return sender_->PacingRate();
 145 }
 146
 147 QuicBandwidth PacingSender::BandwidthEstimate() const {
 148   return sender_->BandwidthEstimate();
 149 }
 150
 151 bool PacingSender::HasReliableBandwidthEstimate() const {
 152   return sender_->HasReliableBandwidthEstimate();
 153 }
 154
 155 QuicTime::Delta PacingSender::RetransmissionDelay() const {
 156   return sender_->RetransmissionDelay();
 157 }
 158
 159 QuicByteCount PacingSender::GetCongestionWindow() const {
 160   return sender_->GetCongestionWindow();
 161 }
 162
 163 bool PacingSender::InSlowStart() const {
 164   return sender_->InSlowStart();
 165 }
 166
 167 bool PacingSender::InRecovery() const {
 168   return sender_->InRecovery();
 169 }
 170
 171 QuicByteCount PacingSender::GetSlowStartThreshold() const {
 172   return sender_->GetSlowStartThreshold();
 173 }
 174
 175 CongestionControlType PacingSender::GetCongestionControlType() const {
 176   return sender_->GetCongestionControlType();
 177 }
 178
 179 }  // namespace net