| // Copyright 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. |
| |
| #include "net/quic/quic_sent_packet_manager.h" |
| |
| #include "base/logging.h" |
| #include "base/stl_util.h" |
| #include "net/quic/congestion_control/pacing_sender.h" |
| #include "net/quic/quic_ack_notifier_manager.h" |
| |
| using std::make_pair; |
| using std::max; |
| using std::min; |
| |
| // TODO(rtenneti): Remove this. |
| // Do not flip this flag until the flakiness of the |
| // net/tools/quic/end_to_end_test is fixed. |
| // If true, then QUIC connections will track the retransmission history of a |
| // packet so that an ack of a previous transmission will ack the data of all |
| // other transmissions. |
| bool FLAGS_track_retransmission_history = false; |
| |
| // Do not remove this flag until the Finch-trials described in b/11706275 |
| // are complete. |
| // If true, QUIC connections will support the use of a pacing algorithm when |
| // sending packets, in an attempt to reduce packet loss. The client must also |
| // request pacing for the server to enable it. |
| bool FLAGS_enable_quic_pacing = false; |
| |
| namespace net { |
| namespace { |
| static const int kBitrateSmoothingPeriodMs = 1000; |
| static const int kHistoryPeriodMs = 5000; |
| |
| static const int kDefaultRetransmissionTimeMs = 500; |
| // TCP RFC calls for 1 second RTO however Linux differs from this default and |
| // define the minimum RTO to 200ms, we will use the same until we have data to |
| // support a higher or lower value. |
| static const int kMinRetransmissionTimeMs = 200; |
| static const int kMaxRetransmissionTimeMs = 60000; |
| static const size_t kMaxRetransmissions = 10; |
| |
| // We retransmit at most 2 packets per ack. |
| static const size_t kMaxRetransmissionsPerAck = 2; |
| |
| // TCP retransmits after 3 nacks. |
| static const size_t kNumberOfNacksBeforeRetransmission = 3; |
| |
| // Only exponentially back off the handshake timer 5 times due to a timeout. |
| static const size_t kMaxHandshakeRetransmissionBackoffs = 5; |
| static const size_t kMinHandshakeTimeoutMs = 10; |
| |
| // Sends up to two tail loss probes before firing an RTO, |
| // per draft RFC draft-dukkipati-tcpm-tcp-loss-probe. |
| static const size_t kDefaultMaxTailLossProbes = 2; |
| static const int64 kMinTailLossProbeTimeoutMs = 10; |
| |
| COMPILE_ASSERT(kHistoryPeriodMs >= kBitrateSmoothingPeriodMs, |
| history_must_be_longer_or_equal_to_the_smoothing_period); |
| |
| } // namespace |
| |
| #define ENDPOINT (is_server_ ? "Server: " : " Client: ") |
| |
| QuicSentPacketManager::HelperInterface::~HelperInterface() { |
| } |
| |
| QuicSentPacketManager::QuicSentPacketManager(bool is_server, |
| HelperInterface* helper, |
| const QuicClock* clock, |
| CongestionFeedbackType type) |
| : is_server_(is_server), |
| helper_(helper), |
| clock_(clock), |
| send_algorithm_(SendAlgorithmInterface::Create(clock, type)), |
| rtt_sample_(QuicTime::Delta::Infinite()), |
| pending_crypto_packet_count_(0), |
| consecutive_rto_count_(0), |
| consecutive_tlp_count_(0), |
| consecutive_crypto_retransmission_count_(0), |
| max_tail_loss_probes_(kDefaultMaxTailLossProbes), |
| using_pacing_(false) { |
| } |
| |
| QuicSentPacketManager::~QuicSentPacketManager() { |
| for (UnackedPacketMap::iterator it = unacked_packets_.begin(); |
| it != unacked_packets_.end(); ++it) { |
| delete it->second.retransmittable_frames; |
| // Only delete previous_transmissions once, for the newest packet. |
| if (it->second.previous_transmissions != NULL && |
| it->first == *it->second.previous_transmissions->rbegin()) { |
| delete it->second.previous_transmissions; |
| } |
| } |
| STLDeleteValues(&packet_history_map_); |
| } |
| |
| void QuicSentPacketManager::SetFromConfig(const QuicConfig& config) { |
| if (config.initial_round_trip_time_us() > 0 && |
| rtt_sample_.IsInfinite()) { |
| // The initial rtt should already be set on the client side. |
| DVLOG_IF(1, !is_server_) |
| << "Client did not set an initial RTT, but did negotiate one."; |
| rtt_sample_ = |
| QuicTime::Delta::FromMicroseconds(config.initial_round_trip_time_us()); |
| send_algorithm_->UpdateRtt(rtt_sample_); |
| } |
| if (config.congestion_control() == kPACE) { |
| MaybeEnablePacing(); |
| } |
| send_algorithm_->SetFromConfig(config, is_server_); |
| } |
| |
| void QuicSentPacketManager::SetMaxPacketSize(QuicByteCount max_packet_size) { |
| send_algorithm_->SetMaxPacketSize(max_packet_size); |
| } |
| |
| // TODO(ianswett): Combine this method with OnPacketSent once packets are always |
| // sent in order and the connection tracks RetransmittableFrames for longer. |
| void QuicSentPacketManager::OnSerializedPacket( |
| const SerializedPacket& serialized_packet) { |
| if (serialized_packet.retransmittable_frames) { |
| ack_notifier_manager_.OnSerializedPacket(serialized_packet); |
| |
| if (serialized_packet.retransmittable_frames->HasCryptoHandshake() |
| == IS_HANDSHAKE) { |
| ++pending_crypto_packet_count_; |
| } |
| } |
| |
| DCHECK(unacked_packets_.empty() || |
| unacked_packets_.rbegin()->first < serialized_packet.sequence_number); |
| unacked_packets_[serialized_packet.sequence_number] = |
| TransmissionInfo(serialized_packet.retransmittable_frames, |
| serialized_packet.sequence_number_length); |
| } |
| |
| void QuicSentPacketManager::OnRetransmittedPacket( |
| QuicPacketSequenceNumber old_sequence_number, |
| QuicPacketSequenceNumber new_sequence_number) { |
| DCHECK(ContainsKey(unacked_packets_, old_sequence_number)); |
| DCHECK(ContainsKey(pending_retransmissions_, old_sequence_number)); |
| DCHECK(unacked_packets_.empty() || |
| unacked_packets_.rbegin()->first < new_sequence_number); |
| |
| pending_retransmissions_.erase(old_sequence_number); |
| // TODO(ianswett): Discard and lose the packet lazily instead of immediately. |
| UnackedPacketMap::iterator unacked_it = |
| unacked_packets_.find(old_sequence_number); |
| TransmissionInfo* transmission_info = &unacked_it->second; |
| RetransmittableFrames* frames = transmission_info->retransmittable_frames; |
| DCHECK(frames); |
| |
| // A notifier may be waiting to hear about ACKs for the original sequence |
| // number. Inform them that the sequence number has changed. |
| ack_notifier_manager_.UpdateSequenceNumber(old_sequence_number, |
| new_sequence_number); |
| |
| // We keep the old packet in the unacked packet list until it, or one of |
| // the retransmissions of it are acked. |
| transmission_info->retransmittable_frames = NULL; |
| unacked_packets_[new_sequence_number] = |
| TransmissionInfo(frames, transmission_info->sequence_number_length); |
| |
| // Keep track of all sequence numbers that this packet |
| // has been transmitted as. |
| SequenceNumberSet* previous_transmissions = |
| transmission_info->previous_transmissions; |
| if (previous_transmissions == NULL) { |
| // This is the first retransmission of this packet, so create a new entry. |
| previous_transmissions = new SequenceNumberSet; |
| transmission_info->previous_transmissions = previous_transmissions; |
| previous_transmissions->insert(old_sequence_number); |
| } |
| previous_transmissions->insert(new_sequence_number); |
| unacked_packets_[new_sequence_number].previous_transmissions = |
| previous_transmissions; |
| |
| DCHECK(HasRetransmittableFrames(new_sequence_number)); |
| } |
| |
| bool QuicSentPacketManager::OnIncomingAck( |
| const ReceivedPacketInfo& received_info, QuicTime ack_receive_time) { |
| // We rely on delta_time_largest_observed to compute an RTT estimate, so |
| // we only update rtt when the largest observed gets acked. |
| bool largest_observed_acked = |
| ContainsKey(unacked_packets_, received_info.largest_observed); |
| MaybeUpdateRTT(received_info, ack_receive_time); |
| HandleAckForSentPackets(received_info); |
| MaybeRetransmitOnAckFrame(received_info, ack_receive_time); |
| |
| // Anytime we are making forward progress and have a new RTT estimate, reset |
| // the backoff counters. |
| if (largest_observed_acked) { |
| // Reset all retransmit counters any time a new packet is acked. |
| consecutive_rto_count_ = 0; |
| consecutive_tlp_count_ = 0; |
| consecutive_crypto_retransmission_count_ = 0; |
| } |
| |
| // Always reset the retransmission alarm when an ack comes in, since we now |
| // have a better estimate of the current rtt than when it was set. |
| return true; |
| } |
| |
| void QuicSentPacketManager::DiscardUnackedPacket( |
| QuicPacketSequenceNumber sequence_number) { |
| MarkPacketHandled(sequence_number, NOT_RECEIVED_BY_PEER); |
| } |
| |
| void QuicSentPacketManager::HandleAckForSentPackets( |
| const ReceivedPacketInfo& received_info) { |
| // Go through the packets we have not received an ack for and see if this |
| // incoming_ack shows they've been seen by the peer. |
| UnackedPacketMap::iterator it = unacked_packets_.begin(); |
| while (it != unacked_packets_.end()) { |
| QuicPacketSequenceNumber sequence_number = it->first; |
| if (sequence_number > received_info.largest_observed) { |
| // These are very new sequence_numbers. |
| break; |
| } |
| |
| if (IsAwaitingPacket(received_info, sequence_number)) { |
| ++it; |
| continue; |
| } |
| |
| // Packet was acked, so remove it from our unacked packet list. |
| DVLOG(1) << ENDPOINT <<"Got an ack for packet " << sequence_number; |
| // If data is associated with the most recent transmission of this |
| // packet, then inform the caller. |
| it = MarkPacketHandled(sequence_number, RECEIVED_BY_PEER); |
| |
| // The AckNotifierManager is informed of every ACKed sequence number. |
| ack_notifier_manager_.OnPacketAcked(sequence_number); |
| } |
| |
| // If we have received a truncated ack, then we need to |
| // clear out some previous transmissions to allow the peer |
| // to actually ACK new packets. |
| if (received_info.is_truncated) { |
| ClearPreviousRetransmissions(received_info.missing_packets.size() / 2); |
| } |
| } |
| |
| void QuicSentPacketManager::ClearPreviousRetransmissions(size_t num_to_clear) { |
| UnackedPacketMap::iterator it = unacked_packets_.begin(); |
| while (it != unacked_packets_.end() && num_to_clear > 0) { |
| QuicPacketSequenceNumber sequence_number = it->first; |
| // If this is not a previous transmission then there is no point |
| // in clearing out any further packets, because it will not affect |
| // the high water mark. |
| SequenceNumberSet* previous_transmissions = |
| it->second.previous_transmissions; |
| if (previous_transmissions == NULL) { |
| if (it->second.retransmittable_frames == NULL) { |
| // This is a current transmission, but a previous transmission has |
| // been acked, so it's safe to remove. |
| it = MarkPacketHandled(sequence_number, NOT_RECEIVED_BY_PEER); |
| --num_to_clear; |
| continue; |
| } |
| break; |
| } |
| QuicPacketSequenceNumber newest_transmission = |
| *previous_transmissions->rbegin(); |
| if (sequence_number == newest_transmission) { |
| break; |
| } |
| |
| DCHECK(it->second.retransmittable_frames == NULL); |
| previous_transmissions->erase(sequence_number); |
| if (previous_transmissions->size() == 1) { |
| unacked_packets_[newest_transmission].previous_transmissions = NULL; |
| delete previous_transmissions; |
| } |
| DCHECK(!it->second.pending); |
| unacked_packets_.erase(it++); |
| --num_to_clear; |
| } |
| } |
| |
| bool QuicSentPacketManager::HasRetransmittableFrames( |
| QuicPacketSequenceNumber sequence_number) const { |
| UnackedPacketMap::const_iterator it = unacked_packets_.find(sequence_number); |
| if (it == unacked_packets_.end()) { |
| return false; |
| } |
| const TransmissionInfo* transmission_info = &it->second; |
| DCHECK(transmission_info); |
| |
| return transmission_info->retransmittable_frames != NULL; |
| } |
| |
| void QuicSentPacketManager::RetransmitUnackedPackets( |
| RetransmissionType retransmission_type) { |
| if (unacked_packets_.empty()) { |
| return; |
| } |
| |
| for (UnackedPacketMap::iterator unacked_it = unacked_packets_.begin(); |
| unacked_it != unacked_packets_.end(); ++unacked_it) { |
| const RetransmittableFrames* frames = |
| unacked_it->second.retransmittable_frames; |
| if (retransmission_type == ALL_PACKETS || |
| (frames != NULL && frames->encryption_level() == ENCRYPTION_INITIAL)) { |
| if (frames) { |
| OnPacketAbandoned(unacked_it); |
| MarkForRetransmission(unacked_it->first, NACK_RETRANSMISSION); |
| } else { |
| DiscardUnackedPacket(unacked_it->first); |
| } |
| } |
| } |
| } |
| |
| void QuicSentPacketManager::MarkForRetransmission( |
| QuicPacketSequenceNumber sequence_number, |
| TransmissionType transmission_type) { |
| DCHECK(ContainsKey(unacked_packets_, sequence_number)); |
| DCHECK(HasRetransmittableFrames(sequence_number)); |
| // TODO(ianswett): Currently the RTO can fire while there are pending NACK |
| // retransmissions for the same data, which is not ideal. |
| if (ContainsKey(pending_retransmissions_, sequence_number)) { |
| return; |
| } |
| |
| pending_retransmissions_[sequence_number] = transmission_type; |
| } |
| |
| bool QuicSentPacketManager::HasPendingRetransmissions() const { |
| return !pending_retransmissions_.empty(); |
| } |
| |
| QuicSentPacketManager::PendingRetransmission |
| QuicSentPacketManager::NextPendingRetransmission() { |
| DCHECK(!pending_retransmissions_.empty()); |
| QuicPacketSequenceNumber sequence_number = |
| pending_retransmissions_.begin()->first; |
| DCHECK(ContainsKey(unacked_packets_, sequence_number)); |
| UnackedPacketMap::iterator unacked_it = |
| unacked_packets_.find(sequence_number); |
| CHECK(unacked_it != unacked_packets_.end()); |
| const TransmissionInfo& transmission_info = unacked_it->second; |
| DCHECK(transmission_info.retransmittable_frames); |
| |
| return PendingRetransmission(sequence_number, |
| pending_retransmissions_.begin()->second, |
| *transmission_info.retransmittable_frames, |
| transmission_info.sequence_number_length); |
| } |
| |
| bool QuicSentPacketManager::IsPreviousTransmission( |
| QuicPacketSequenceNumber sequence_number) const { |
| DCHECK(ContainsKey(unacked_packets_, sequence_number)); |
| |
| UnackedPacketMap::const_iterator unacked_it = |
| unacked_packets_.find(sequence_number); |
| if (unacked_it == unacked_packets_.end()) { |
| return false; |
| } |
| const TransmissionInfo* transmission_info = &unacked_it->second; |
| if (transmission_info->previous_transmissions == NULL) { |
| return false; |
| } |
| |
| SequenceNumberSet* previous_transmissions = |
| transmission_info->previous_transmissions; |
| DCHECK(!previous_transmissions->empty()); |
| return *previous_transmissions->rbegin() != sequence_number; |
| } |
| |
| // static |
| bool QuicSentPacketManager::HasCryptoHandshake( |
| const TransmissionInfo& transmission_info) { |
| if (transmission_info.retransmittable_frames == NULL) { |
| return false; |
| } |
| return transmission_info.retransmittable_frames->HasCryptoHandshake() == |
| IS_HANDSHAKE; |
| } |
| |
| QuicSentPacketManager::UnackedPacketMap::iterator |
| QuicSentPacketManager::MarkPacketHandled( |
| QuicPacketSequenceNumber sequence_number, ReceivedByPeer received_by_peer) { |
| DCHECK(ContainsKey(unacked_packets_, sequence_number)); |
| |
| // If this packet is pending, remove it and inform the send algorithm. |
| UnackedPacketMap::iterator it = unacked_packets_.find(sequence_number); |
| if (it->second.pending) { |
| size_t bytes_sent = packet_history_map_[sequence_number]->bytes_sent(); |
| if (received_by_peer == RECEIVED_BY_PEER) { |
| send_algorithm_->OnPacketAcked(sequence_number, bytes_sent); |
| } else { |
| // It's been abandoned. |
| send_algorithm_->OnPacketAbandoned(sequence_number, bytes_sent); |
| } |
| it->second.pending = false; |
| } |
| |
| // If this packet has never been retransmitted, then simply drop it. |
| if (it->second.previous_transmissions == NULL) { |
| ++it; |
| DiscardPacket(sequence_number); |
| return it; |
| } |
| |
| SequenceNumberSet* previous_transmissions = it->second.previous_transmissions; |
| DCHECK(!previous_transmissions->empty()); |
| SequenceNumberSet::reverse_iterator previous_transmissions_it = |
| previous_transmissions->rbegin(); |
| QuicPacketSequenceNumber newest_transmission = *previous_transmissions_it; |
| if (newest_transmission == sequence_number) { |
| DiscardPacket(newest_transmission); |
| } else { |
| UnackedPacketMap::iterator unacked_it = |
| unacked_packets_.find(newest_transmission); |
| TransmissionInfo* transmission_info = &unacked_it->second; |
| if (HasCryptoHandshake(*transmission_info)) { |
| --pending_crypto_packet_count_; |
| } |
| // If we have received an ack for a previous transmission of a packet, |
| // we want to keep the "new" transmission of the packet unacked, |
| // but prevent the data from being retransmitted. |
| delete transmission_info->retransmittable_frames; |
| transmission_info->retransmittable_frames = NULL; |
| transmission_info->previous_transmissions = NULL; |
| } |
| |
| // Clear out information all previous transmissions. |
| ++previous_transmissions_it; |
| while (previous_transmissions_it != previous_transmissions->rend()) { |
| QuicPacketSequenceNumber previous_transmission = *previous_transmissions_it; |
| ++previous_transmissions_it; |
| // If the packet was TLP retransmitted, the old copy was not yet considered |
| // lost or abandoned, so do that now. |
| if (unacked_packets_[previous_transmission].pending) { |
| send_algorithm_->OnPacketLost(previous_transmission, clock_->Now()); |
| OnPacketAbandoned(unacked_packets_.find(previous_transmission)); |
| } |
| DiscardPacket(previous_transmission); |
| } |
| |
| delete previous_transmissions; |
| |
| if (ContainsKey(pending_retransmissions_, newest_transmission)) { |
| pending_retransmissions_.erase(newest_transmission); |
| if (!unacked_packets_[newest_transmission].pending) { |
| // If the newest transmission has already been marked for retransmission |
| // and has already been abandoned, then we should remove it from |
| // unacked_packets_, as well as cancel the retransmission. |
| DCHECK(ContainsKey(unacked_packets_, newest_transmission)); |
| DCHECK(!unacked_packets_[newest_transmission].previous_transmissions); |
| unacked_packets_.erase(newest_transmission); |
| } |
| } |
| |
| UnackedPacketMap::iterator next_unacked = unacked_packets_.begin(); |
| while (next_unacked != unacked_packets_.end() && |
| next_unacked->first < sequence_number) { |
| ++next_unacked; |
| } |
| return next_unacked; |
| } |
| |
| void QuicSentPacketManager::DiscardPacket( |
| QuicPacketSequenceNumber sequence_number) { |
| UnackedPacketMap::iterator unacked_it = |
| unacked_packets_.find(sequence_number); |
| DCHECK(unacked_it != unacked_packets_.end()); |
| // Ensure the packet is no longer pending when it's discarded. |
| DCHECK(!unacked_it->second.pending); |
| |
| RetransmittableFrames* retransmittable_frames = |
| unacked_it->second.retransmittable_frames; |
| if (HasCryptoHandshake(unacked_it->second)) { |
| --pending_crypto_packet_count_; |
| } |
| |
| // Delete the retransmittable frames. |
| delete retransmittable_frames; |
| unacked_packets_.erase(unacked_it); |
| pending_retransmissions_.erase(sequence_number); |
| return; |
| } |
| |
| bool QuicSentPacketManager::IsUnacked( |
| QuicPacketSequenceNumber sequence_number) const { |
| return ContainsKey(unacked_packets_, sequence_number); |
| } |
| |
| bool QuicSentPacketManager::HasUnackedPackets() const { |
| return !unacked_packets_.empty(); |
| } |
| |
| bool QuicSentPacketManager::HasPendingPackets() const { |
| for (UnackedPacketMap::const_reverse_iterator it = |
| unacked_packets_.rbegin(); it != unacked_packets_.rend(); ++it) { |
| if (it->second.pending) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| size_t QuicSentPacketManager::GetNumRetransmittablePackets() const { |
| size_t num_unacked_packets = 0; |
| for (UnackedPacketMap::const_iterator it = unacked_packets_.begin(); |
| it != unacked_packets_.end(); ++it) { |
| QuicPacketSequenceNumber sequence_number = it->first; |
| if (HasRetransmittableFrames(sequence_number)) { |
| ++num_unacked_packets; |
| } |
| } |
| return num_unacked_packets; |
| } |
| |
| QuicPacketSequenceNumber |
| QuicSentPacketManager::GetLeastUnackedSentPacket() const { |
| if (unacked_packets_.empty()) { |
| // If there are no unacked packets, set the least unacked packet to |
| // the sequence number of the next packet sent. |
| return helper_->GetNextPacketSequenceNumber(); |
| } |
| |
| return unacked_packets_.begin()->first; |
| } |
| |
| SequenceNumberSet QuicSentPacketManager::GetUnackedPackets() const { |
| SequenceNumberSet unacked_packets; |
| for (UnackedPacketMap::const_iterator it = unacked_packets_.begin(); |
| it != unacked_packets_.end(); ++it) { |
| unacked_packets.insert(it->first); |
| } |
| return unacked_packets; |
| } |
| |
| bool QuicSentPacketManager::OnPacketSent( |
| QuicPacketSequenceNumber sequence_number, |
| QuicTime sent_time, |
| QuicByteCount bytes, |
| TransmissionType transmission_type, |
| HasRetransmittableData has_retransmittable_data) { |
| DCHECK_LT(0u, sequence_number); |
| UnackedPacketMap::iterator it = unacked_packets_.find(sequence_number); |
| // In rare circumstances, the packet could be serialized, sent, and then acked |
| // before OnPacketSent is called. |
| if (it == unacked_packets_.end()) { |
| return false; |
| } |
| DCHECK(!it->second.pending); |
| |
| // Only track packets the send algorithm wants us to track. |
| if (!send_algorithm_->OnPacketSent(sent_time, sequence_number, bytes, |
| transmission_type, |
| has_retransmittable_data)) { |
| DCHECK(it->second.retransmittable_frames == NULL); |
| unacked_packets_.erase(it); |
| // Do not reset the retransmission timer, since the packet isn't tracked. |
| return false; |
| } |
| |
| const bool set_retransmission_timer = !HasPendingPackets(); |
| it->second.sent_time = sent_time; |
| it->second.pending = true; |
| packet_history_map_[sequence_number] = |
| new SendAlgorithmInterface::SentPacket(bytes, sent_time); |
| CleanupPacketHistory(); |
| |
| // Reset the retransmission timer anytime a packet is sent in tail loss probe |
| // mode or before the crypto handshake has completed. |
| return set_retransmission_timer || GetRetransmissionMode() != RTO_MODE; |
| } |
| |
| void QuicSentPacketManager::OnRetransmissionTimeout() { |
| DCHECK(HasPendingPackets()); |
| // Handshake retransmission, TLP, and RTO are implemented with a single alarm. |
| // The handshake alarm is set when the handshake has not completed, and the |
| // TLP and RTO alarms are set after that. |
| // The TLP alarm is always set to run for under an RTO. |
| switch (GetRetransmissionMode()) { |
| case HANDSHAKE_MODE: |
| RetransmitCryptoPackets(); |
| return; |
| case TLP_MODE: |
| // If no tail loss probe can be sent, because there are no retransmittable |
| // packets, execute a conventional RTO to abandon old packets. |
| RetransmitOldestPacket(); |
| return; |
| case RTO_MODE: |
| RetransmitAllPackets(); |
| return; |
| } |
| } |
| |
| void QuicSentPacketManager::RetransmitCryptoPackets() { |
| DCHECK_EQ(HANDSHAKE_MODE, GetRetransmissionMode()); |
| // TODO(ianswett): Typical TCP implementations only retransmit 5 times. |
| consecutive_crypto_retransmission_count_ = |
| min(kMaxHandshakeRetransmissionBackoffs, |
| consecutive_crypto_retransmission_count_ + 1); |
| bool packet_retransmitted = false; |
| for (UnackedPacketMap::iterator it = unacked_packets_.begin(); |
| it != unacked_packets_.end(); ++it) { |
| QuicPacketSequenceNumber sequence_number = it->first; |
| const RetransmittableFrames* frames = it->second.retransmittable_frames; |
| // Only retransmit frames which are pending, and therefore have been sent. |
| if (!it->second.pending || frames == NULL || |
| frames->HasCryptoHandshake() != IS_HANDSHAKE) { |
| continue; |
| } |
| DCHECK(ContainsKey(packet_history_map_, sequence_number)); |
| packet_retransmitted = true; |
| MarkForRetransmission(sequence_number, TLP_RETRANSMISSION); |
| // Abandon all the crypto retransmissions now so they're not lost later. |
| OnPacketAbandoned(it); |
| } |
| DCHECK(packet_retransmitted) << "No crypto packets found to retransmit."; |
| } |
| |
| void QuicSentPacketManager::RetransmitOldestPacket() { |
| DCHECK_EQ(TLP_MODE, GetRetransmissionMode()); |
| ++consecutive_tlp_count_; |
| for (UnackedPacketMap::const_iterator it = unacked_packets_.begin(); |
| it != unacked_packets_.end(); ++it) { |
| QuicPacketSequenceNumber sequence_number = it->first; |
| const RetransmittableFrames* frames = it->second.retransmittable_frames; |
| // Only retransmit frames which are pending, and therefore have been sent. |
| if (!it->second.pending || frames == NULL) { |
| continue; |
| } |
| DCHECK_NE(IS_HANDSHAKE, frames->HasCryptoHandshake()); |
| MarkForRetransmission(sequence_number, TLP_RETRANSMISSION); |
| return; |
| } |
| DLOG(FATAL) |
| << "No retransmittable packets, so RetransmitOldestPacket failed."; |
| } |
| |
| void QuicSentPacketManager::RetransmitAllPackets() { |
| // Abandon all retransmittable packets and packets older than the |
| // retransmission delay. |
| |
| DVLOG(1) << "OnRetransmissionTimeout() fired with " |
| << unacked_packets_.size() << " unacked packets."; |
| |
| // Request retransmission of all retransmittable packets when the RTO |
| // fires, and let the congestion manager decide how many to send |
| // immediately and the remaining packets will be queued. |
| // Abandon any non-retransmittable packets that are sufficiently old. |
| bool packets_retransmitted = false; |
| for (UnackedPacketMap::iterator it = unacked_packets_.begin(); |
| it != unacked_packets_.end(); ++it) { |
| it->second.pending = false; |
| if (it->second.retransmittable_frames != NULL) { |
| packets_retransmitted = true; |
| MarkForRetransmission(it->first, RTO_RETRANSMISSION); |
| } |
| } |
| |
| send_algorithm_->OnRetransmissionTimeout(packets_retransmitted); |
| if (packets_retransmitted) { |
| ++consecutive_rto_count_; |
| } |
| } |
| |
| QuicSentPacketManager::RetransmissionTimeoutMode |
| QuicSentPacketManager::GetRetransmissionMode() const { |
| DCHECK(HasPendingPackets()); |
| if (pending_crypto_packet_count_ > 0) { |
| return HANDSHAKE_MODE; |
| } |
| if (consecutive_tlp_count_ < max_tail_loss_probes_) { |
| // Ensure there are retransmittable frames. |
| for (UnackedPacketMap::const_reverse_iterator it = |
| unacked_packets_.rbegin(); it != unacked_packets_.rend(); ++it) { |
| if (it->second.pending && it->second.retransmittable_frames) { |
| return TLP_MODE; |
| } |
| } |
| } |
| return RTO_MODE; |
| } |
| |
| void QuicSentPacketManager::OnPacketAbandoned(UnackedPacketMap::iterator it) { |
| DCHECK(it != unacked_packets_.end()); |
| QuicPacketSequenceNumber sequence_number = it->first; |
| DCHECK(ContainsKey(packet_history_map_, sequence_number)); |
| if (it->second.pending) { |
| send_algorithm_->OnPacketAbandoned( |
| sequence_number, packet_history_map_[sequence_number]->bytes_sent()); |
| it->second.pending = false; |
| } |
| } |
| |
| void QuicSentPacketManager::OnIncomingQuicCongestionFeedbackFrame( |
| const QuicCongestionFeedbackFrame& frame, |
| const QuicTime& feedback_receive_time) { |
| send_algorithm_->OnIncomingQuicCongestionFeedbackFrame( |
| frame, feedback_receive_time, packet_history_map_); |
| } |
| |
| void QuicSentPacketManager::MaybeRetransmitOnAckFrame( |
| const ReceivedPacketInfo& received_info, |
| const QuicTime& ack_receive_time) { |
| // Go through all pending packets up to the largest observed and see if any |
| // need to be retransmitted or lost. |
| size_t num_retransmitted = 0; |
| UnackedPacketMap::iterator it = unacked_packets_.begin(); |
| while (it != unacked_packets_.end() && |
| it->first <= received_info.largest_observed) { |
| if (!it->second.pending) { |
| ++it; |
| continue; |
| } |
| QuicPacketSequenceNumber sequence_number = it->first; |
| DVLOG(1) << "still missing packet " << sequence_number; |
| // Acks must be handled previously, so ensure it's missing and not acked. |
| DCHECK(IsAwaitingPacket(received_info, sequence_number)); |
| DCHECK(ContainsKey(packet_history_map_, sequence_number)); |
| const TransmissionInfo& transmission_info = it->second; |
| SendAlgorithmInterface::SentPacket* sent_packet = |
| packet_history_map_[sequence_number]; |
| |
| // Consider it multiple nacks when there is a gap between the missing packet |
| // and the largest observed, since the purpose of a nack threshold is to |
| // tolerate re-ordering. This handles both StretchAcks and Forward Acks. |
| // TODO(ianswett): This relies heavily on sequential reception of packets, |
| // and makes an assumption that the congestion control uses TCP style nacks. |
| size_t min_nacks = received_info.largest_observed - sequence_number; |
| sent_packet->Nack(min_nacks); |
| |
| size_t num_nacks_needed = kNumberOfNacksBeforeRetransmission; |
| // Check for early retransmit(RFC5827) when the last packet gets acked and |
| // the there are fewer than 4 pending packets. |
| // TODO(ianswett): Set a retransmission timer instead of losing the packet |
| // and retransmitting immediately. Also consider only invoking OnPacketLost |
| // and OnPacketAbandoned when they're actually retransmitted in case they |
| // arrive while queued for retransmission. |
| if (transmission_info.retransmittable_frames && |
| packet_history_map_.rbegin()->first == received_info.largest_observed) { |
| num_nacks_needed = received_info.largest_observed - sequence_number; |
| } |
| |
| if (sent_packet->nack_count() < num_nacks_needed) { |
| ++it; |
| continue; |
| } |
| |
| // If the number of retransmissions has maxed out, don't lose or retransmit |
| // any more packets. |
| if (num_retransmitted >= kMaxRetransmissionsPerAck) { |
| ++it; |
| continue; |
| } |
| |
| // TODO(ianswett): OnPacketLost is also called from TCPCubicSender when |
| // an FEC packet is lost, but FEC loss information should be shared among |
| // congestion managers. Additionally, if it's expected the FEC packet may |
| // repair the loss, it should be recorded as a loss to the congestion |
| // manager, but not retransmitted until it's known whether the FEC packet |
| // arrived. |
| send_algorithm_->OnPacketLost(sequence_number, ack_receive_time); |
| OnPacketAbandoned(it); |
| |
| if (transmission_info.retransmittable_frames) { |
| ++num_retransmitted; |
| MarkForRetransmission(sequence_number, NACK_RETRANSMISSION); |
| ++it; |
| } else { |
| // Since we will not retransmit this, we need to remove it from |
| // unacked_packets_. This is either the current transmission of |
| // a packet whose previous transmission has been acked, or it |
| // is a packet that has been TLP retransmitted. |
| RemovePreviousTransmission(sequence_number); |
| unacked_packets_.erase(it++); |
| } |
| } |
| } |
| |
| void QuicSentPacketManager::MaybeUpdateRTT( |
| const ReceivedPacketInfo& received_info, |
| const QuicTime& ack_receive_time) { |
| // We calculate the RTT based on the highest ACKed sequence number, the lower |
| // sequence numbers will include the ACK aggregation delay. |
| UnackedPacketMap::iterator unacked_it = |
| unacked_packets_.find(received_info.largest_observed); |
| if (unacked_it == unacked_packets_.end()) { |
| return; |
| } |
| const TransmissionInfo* transmission_info = &unacked_it->second; |
| if (transmission_info == NULL) { |
| return; |
| } |
| // Don't update the RTT if it hasn't been sent. |
| if (transmission_info->sent_time == QuicTime::Zero()) { |
| return; |
| } |
| |
| QuicTime::Delta send_delta = |
| ack_receive_time.Subtract(transmission_info->sent_time); |
| if (send_delta > received_info.delta_time_largest_observed) { |
| rtt_sample_ = send_delta.Subtract( |
| received_info.delta_time_largest_observed); |
| } else if (rtt_sample_.IsInfinite()) { |
| // Even though we received information from the peer suggesting |
| // an invalid (negative) RTT, we can use the send delta as an |
| // approximation until we get a better estimate. |
| rtt_sample_ = send_delta; |
| } |
| send_algorithm_->UpdateRtt(rtt_sample_); |
| } |
| |
| QuicTime::Delta QuicSentPacketManager::TimeUntilSend( |
| QuicTime now, |
| TransmissionType transmission_type, |
| HasRetransmittableData retransmittable, |
| IsHandshake handshake) { |
| return send_algorithm_->TimeUntilSend(now, transmission_type, retransmittable, |
| handshake); |
| } |
| |
| // Ensures that the Delayed Ack timer is always set to a value lesser |
| // than the retransmission timer's minimum value (MinRTO). We want the |
| // delayed ack to get back to the QUIC peer before the sender's |
| // retransmission timer triggers. Since we do not know the |
| // reverse-path one-way delay, we assume equal delays for forward and |
| // reverse paths, and ensure that the timer is set to less than half |
| // of the MinRTO. |
| // There may be a value in making this delay adaptive with the help of |
| // the sender and a signaling mechanism -- if the sender uses a |
| // different MinRTO, we may get spurious retransmissions. May not have |
| // any benefits, but if the delayed ack becomes a significant source |
| // of (likely, tail) latency, then consider such a mechanism. |
| const QuicTime::Delta QuicSentPacketManager::DelayedAckTime() const { |
| return QuicTime::Delta::FromMilliseconds(kMinRetransmissionTimeMs/2); |
| } |
| |
| const QuicTime QuicSentPacketManager::GetRetransmissionTime() const { |
| // Don't set the timer if there are no pending packets. |
| if (!HasPendingPackets()) { |
| return QuicTime::Zero(); |
| } |
| switch (GetRetransmissionMode()) { |
| case HANDSHAKE_MODE: |
| return clock_->ApproximateNow().Add(GetCryptoRetransmissionDelay()); |
| case TLP_MODE: { |
| // TODO(ianswett): When CWND is available, it would be preferable to |
| // set the timer based on the earliest retransmittable packet. |
| // Base the updated timer on the send time of the last packet. |
| UnackedPacketMap::const_reverse_iterator it = unacked_packets_.rbegin(); |
| while (it != unacked_packets_.rend() && |
| (!it->second.pending || |
| it->second.retransmittable_frames == NULL)) { |
| ++it; |
| } |
| DCHECK(it != unacked_packets_.rend()); |
| const QuicTime& sent_time = it->second.sent_time; |
| const QuicTime tlp_time = sent_time.Add(GetTailLossProbeDelay()); |
| // Ensure the tlp timer never gets set to a time in the past. |
| return QuicTime::Max(clock_->ApproximateNow(), tlp_time); |
| } |
| case RTO_MODE: { |
| // The RTO is based on the first pending packet. |
| UnackedPacketMap::const_iterator it = unacked_packets_.begin(); |
| while (it != unacked_packets_.end() && !it->second.pending) { |
| ++it; |
| } |
| DCHECK(it != unacked_packets_.end()); |
| const QuicTime& sent_time = it->second.sent_time; |
| // Always wait at least 1.5 * RTT after the first sent packet. |
| QuicTime min_timeout = clock_->ApproximateNow().Add( |
| SmoothedRtt().Multiply(1.5)); |
| QuicTime rto_timeout = sent_time.Add(GetRetransmissionDelay()); |
| return QuicTime::Max(min_timeout, rto_timeout); |
| } |
| } |
| DCHECK(false); |
| return QuicTime::Zero(); |
| } |
| |
| const QuicTime::Delta QuicSentPacketManager::GetCryptoRetransmissionDelay() |
| const { |
| // This is equivalent to the TailLossProbeDelay, but slightly more aggressive |
| // because crypto handshake messages don't incur a delayed ack time. |
| int64 delay_ms = max<int64>(kMinHandshakeTimeoutMs, |
| 1.5 * SmoothedRtt().ToMilliseconds()); |
| return QuicTime::Delta::FromMilliseconds( |
| delay_ms << consecutive_crypto_retransmission_count_); |
| } |
| |
| const QuicTime::Delta QuicSentPacketManager::GetTailLossProbeDelay() const { |
| QuicTime::Delta srtt = SmoothedRtt(); |
| size_t num_pending = 0; |
| for (UnackedPacketMap::const_reverse_iterator it = unacked_packets_.rbegin(); |
| it != unacked_packets_.rend(); ++it) { |
| if (it->second.pending) { |
| ++num_pending; |
| if (num_pending > 1) { |
| break; |
| } |
| } |
| } |
| DCHECK_LT(0u, num_pending); |
| if (num_pending == 1) { |
| return QuicTime::Delta::Max( |
| srtt.Multiply(1.5).Add(DelayedAckTime()), srtt.Multiply(2)); |
| } |
| return QuicTime::Delta::FromMilliseconds( |
| max(kMinTailLossProbeTimeoutMs, |
| static_cast<int64>(2 * srtt.ToMilliseconds()))); |
| } |
| |
| const QuicTime::Delta QuicSentPacketManager::GetRetransmissionDelay() const { |
| QuicTime::Delta retransmission_delay = send_algorithm_->RetransmissionDelay(); |
| if (retransmission_delay.IsZero()) { |
| // We are in the initial state, use default timeout values. |
| retransmission_delay = |
| QuicTime::Delta::FromMilliseconds(kDefaultRetransmissionTimeMs); |
| } |
| // Calculate exponential back off. |
| retransmission_delay = retransmission_delay.Multiply( |
| 1 << min<size_t>(consecutive_rto_count_, kMaxRetransmissions)); |
| |
| // TODO(rch): This code should move to |send_algorithm_|. |
| if (retransmission_delay.ToMilliseconds() < kMinRetransmissionTimeMs) { |
| return QuicTime::Delta::FromMilliseconds(kMinRetransmissionTimeMs); |
| } |
| if (retransmission_delay.ToMilliseconds() > kMaxRetransmissionTimeMs) { |
| return QuicTime::Delta::FromMilliseconds(kMaxRetransmissionTimeMs); |
| } |
| return retransmission_delay; |
| } |
| |
| const QuicTime::Delta QuicSentPacketManager::SmoothedRtt() const { |
| return send_algorithm_->SmoothedRtt(); |
| } |
| |
| QuicBandwidth QuicSentPacketManager::BandwidthEstimate() const { |
| return send_algorithm_->BandwidthEstimate(); |
| } |
| |
| QuicByteCount QuicSentPacketManager::GetCongestionWindow() const { |
| return send_algorithm_->GetCongestionWindow(); |
| } |
| |
| void QuicSentPacketManager::CleanupPacketHistory() { |
| const QuicTime::Delta kHistoryPeriod = |
| QuicTime::Delta::FromMilliseconds(kHistoryPeriodMs); |
| QuicTime now = clock_->ApproximateNow(); |
| |
| SendAlgorithmInterface::SentPacketsMap::iterator history_it = |
| packet_history_map_.begin(); |
| for (; history_it != packet_history_map_.end(); ++history_it) { |
| if (now.Subtract(history_it->second->send_timestamp()) <= kHistoryPeriod) { |
| return; |
| } |
| // Don't remove packets which have not been acked. |
| if (ContainsKey(unacked_packets_, history_it->first)) { |
| continue; |
| } |
| delete history_it->second; |
| packet_history_map_.erase(history_it); |
| history_it = packet_history_map_.begin(); |
| } |
| } |
| |
| void QuicSentPacketManager::MaybeEnablePacing() { |
| if (!FLAGS_enable_quic_pacing) { |
| return; |
| } |
| |
| if (using_pacing_) { |
| return; |
| } |
| |
| using_pacing_ = true; |
| send_algorithm_.reset( |
| new PacingSender(send_algorithm_.release(), |
| QuicTime::Delta::FromMicroseconds(1))); |
| } |
| |
| void QuicSentPacketManager::RemovePreviousTransmission( |
| QuicPacketSequenceNumber sequence_number) { |
| SequenceNumberSet* previous_transmissions = |
| unacked_packets_[sequence_number].previous_transmissions; |
| if (!previous_transmissions) { |
| return; |
| } |
| previous_transmissions->erase(sequence_number); |
| if (previous_transmissions->size() == 1) { |
| QuicPacketSequenceNumber current = *previous_transmissions->begin(); |
| unacked_packets_[current].previous_transmissions = NULL; |
| delete previous_transmissions; |
| } |
| } |
| |
| } // namespace net |