1 // Copyright 2014 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/time_loss_algorithm.h" 6 7 #include "net/quic/congestion_control/rtt_stats.h" 8 #include "net/quic/quic_protocol.h" 9 10 namespace net { 11 namespace { 12 13 // The minimum delay before a packet will be considered lost, 14 // regardless of SRTT. Half of the minimum TLP, since the loss algorithm only 15 // triggers when a nack has been receieved for the packet. 16 static const size_t kMinLossDelayMs = 5; 17 18 // How many RTTs the algorithm waits before determining a packet is lost. 19 static const double kLossDelayMultiplier = 1.25; 20 21 } // namespace 22 23 TimeLossAlgorithm::TimeLossAlgorithm() 24 : loss_detection_timeout_(QuicTime::Zero()) { } 25 26 LossDetectionType TimeLossAlgorithm::GetLossDetectionType() const { 27 return kTime; 28 } 29 30 SequenceNumberSet TimeLossAlgorithm::DetectLostPackets( 31 const QuicUnackedPacketMap& unacked_packets, 32 const QuicTime& time, 33 QuicPacketSequenceNumber largest_observed, 34 const RttStats& rtt_stats) { 35 SequenceNumberSet lost_packets; 36 loss_detection_timeout_ = QuicTime::Zero(); 37 QuicTime::Delta loss_delay = QuicTime::Delta::Max( 38 QuicTime::Delta::FromMilliseconds(kMinLossDelayMs), 39 QuicTime::Delta::Max(rtt_stats.SmoothedRtt(), rtt_stats.latest_rtt()) 40 .Multiply(kLossDelayMultiplier)); 41 42 for (QuicUnackedPacketMap::const_iterator it = unacked_packets.begin(); 43 it != unacked_packets.end() && it->first <= largest_observed; ++it) { 44 if (!it->second.in_flight) { 45 continue; 46 } 47 LOG_IF(DFATAL, it->second.nack_count == 0) 48 << "All packets less than largest observed should have been nacked."; 49 50 // Packets are sent in order, so break when we haven't waited long enough 51 // to lose any more packets and leave the loss_time_ set for the timeout. 52 QuicTime when_lost = it->second.sent_time.Add(loss_delay); 53 if (time < when_lost) { 54 loss_detection_timeout_ = when_lost; 55 break; 56 } 57 lost_packets.insert(it->first); 58 } 59 60 return lost_packets; 61 } 62 63 // loss_time_ is updated in DetectLostPackets, which must be called every time 64 // an ack is received or the timeout expires. 65 QuicTime TimeLossAlgorithm::GetLossTimeout() const { 66 return loss_detection_timeout_; 67 } 68 69 } // namespace net 70