| // 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 "quic/core/quic_received_packet_manager.h" |
| |
| #include <algorithm> |
| #include <limits> |
| #include <utility> |
| |
| #include "quic/core/congestion_control/rtt_stats.h" |
| #include "quic/core/crypto/crypto_protocol.h" |
| #include "quic/core/quic_connection_stats.h" |
| #include "quic/platform/api/quic_bug_tracker.h" |
| #include "quic/platform/api/quic_flags.h" |
| #include "quic/platform/api/quic_logging.h" |
| |
| namespace quic { |
| |
| namespace { |
| |
| // The maximum number of packets to ack immediately after a missing packet for |
| // fast retransmission to kick in at the sender. This limit is created to |
| // reduce the number of acks sent that have no benefit for fast retransmission. |
| // Set to the number of nacks needed for fast retransmit plus one for protection |
| // against an ack loss |
| const size_t kMaxPacketsAfterNewMissing = 4; |
| |
| // One eighth RTT delay when doing ack decimation. |
| const float kShortAckDecimationDelay = 0.125; |
| } // namespace |
| |
| QuicReceivedPacketManager::QuicReceivedPacketManager() |
| : QuicReceivedPacketManager(nullptr) {} |
| |
| QuicReceivedPacketManager::QuicReceivedPacketManager(QuicConnectionStats* stats) |
| : ack_frame_updated_(false), |
| max_ack_ranges_(0), |
| time_largest_observed_(QuicTime::Zero()), |
| save_timestamps_(false), |
| save_timestamps_for_in_order_packets_(false), |
| stats_(stats), |
| num_retransmittable_packets_received_since_last_ack_sent_(0), |
| min_received_before_ack_decimation_(kMinReceivedBeforeAckDecimation), |
| ack_frequency_(kDefaultRetransmittablePacketsBeforeAck), |
| ack_decimation_delay_(kAckDecimationDelay), |
| unlimited_ack_decimation_(false), |
| one_immediate_ack_(false), |
| ignore_order_(false), |
| local_max_ack_delay_( |
| QuicTime::Delta::FromMilliseconds(kDefaultDelayedAckTimeMs)), |
| ack_timeout_(QuicTime::Zero()), |
| time_of_previous_received_packet_(QuicTime::Zero()), |
| was_last_packet_missing_(false), |
| last_ack_frequency_frame_sequence_number_(-1) {} |
| |
| QuicReceivedPacketManager::~QuicReceivedPacketManager() {} |
| |
| void QuicReceivedPacketManager::SetFromConfig(const QuicConfig& config, |
| Perspective perspective) { |
| if (config.HasClientSentConnectionOption(kAKD3, perspective)) { |
| ack_decimation_delay_ = kShortAckDecimationDelay; |
| } |
| if (config.HasClientSentConnectionOption(kAKDU, perspective)) { |
| unlimited_ack_decimation_ = true; |
| } |
| if (config.HasClientSentConnectionOption(k1ACK, perspective)) { |
| one_immediate_ack_ = true; |
| } |
| } |
| |
| void QuicReceivedPacketManager::RecordPacketReceived( |
| const QuicPacketHeader& header, |
| QuicTime receipt_time) { |
| const QuicPacketNumber packet_number = header.packet_number; |
| QUICHE_DCHECK(IsAwaitingPacket(packet_number)) |
| << " packet_number:" << packet_number; |
| was_last_packet_missing_ = IsMissing(packet_number); |
| if (!ack_frame_updated_) { |
| ack_frame_.received_packet_times.clear(); |
| } |
| ack_frame_updated_ = true; |
| |
| // Whether |packet_number| is received out of order. |
| bool packet_reordered = false; |
| if (LargestAcked(ack_frame_).IsInitialized() && |
| LargestAcked(ack_frame_) > packet_number) { |
| // Record how out of order stats. |
| packet_reordered = true; |
| ++stats_->packets_reordered; |
| stats_->max_sequence_reordering = |
| std::max(stats_->max_sequence_reordering, |
| LargestAcked(ack_frame_) - packet_number); |
| int64_t reordering_time_us = |
| (receipt_time - time_largest_observed_).ToMicroseconds(); |
| stats_->max_time_reordering_us = |
| std::max(stats_->max_time_reordering_us, reordering_time_us); |
| } |
| if (!LargestAcked(ack_frame_).IsInitialized() || |
| packet_number > LargestAcked(ack_frame_)) { |
| ack_frame_.largest_acked = packet_number; |
| time_largest_observed_ = receipt_time; |
| } |
| ack_frame_.packets.Add(packet_number); |
| |
| if (save_timestamps_) { |
| // The timestamp format only handles packets in time order. |
| if (save_timestamps_for_in_order_packets_ && packet_reordered) { |
| QUIC_DLOG(WARNING) << "Not saving receive timestamp for packet " |
| << packet_number; |
| } else if (!ack_frame_.received_packet_times.empty() && |
| ack_frame_.received_packet_times.back().second > receipt_time) { |
| QUIC_LOG(WARNING) |
| << "Receive time went backwards from: " |
| << ack_frame_.received_packet_times.back().second.ToDebuggingValue() |
| << " to " << receipt_time.ToDebuggingValue(); |
| } else { |
| ack_frame_.received_packet_times.push_back( |
| std::make_pair(packet_number, receipt_time)); |
| } |
| } |
| |
| if (least_received_packet_number_.IsInitialized()) { |
| least_received_packet_number_ = |
| std::min(least_received_packet_number_, packet_number); |
| } else { |
| least_received_packet_number_ = packet_number; |
| } |
| } |
| |
| bool QuicReceivedPacketManager::IsMissing(QuicPacketNumber packet_number) { |
| return LargestAcked(ack_frame_).IsInitialized() && |
| packet_number < LargestAcked(ack_frame_) && |
| !ack_frame_.packets.Contains(packet_number); |
| } |
| |
| bool QuicReceivedPacketManager::IsAwaitingPacket( |
| QuicPacketNumber packet_number) const { |
| return quic::IsAwaitingPacket(ack_frame_, packet_number, |
| peer_least_packet_awaiting_ack_); |
| } |
| |
| const QuicFrame QuicReceivedPacketManager::GetUpdatedAckFrame( |
| QuicTime approximate_now) { |
| if (time_largest_observed_ == QuicTime::Zero()) { |
| // We have received no packets. |
| ack_frame_.ack_delay_time = QuicTime::Delta::Infinite(); |
| } else { |
| // Ensure the delta is zero if approximate now is "in the past". |
| ack_frame_.ack_delay_time = approximate_now < time_largest_observed_ |
| ? QuicTime::Delta::Zero() |
| : approximate_now - time_largest_observed_; |
| } |
| while (max_ack_ranges_ > 0 && |
| ack_frame_.packets.NumIntervals() > max_ack_ranges_) { |
| ack_frame_.packets.RemoveSmallestInterval(); |
| } |
| // Clear all packet times if any are too far from largest observed. |
| // It's expected this is extremely rare. |
| for (auto it = ack_frame_.received_packet_times.begin(); |
| it != ack_frame_.received_packet_times.end();) { |
| if (LargestAcked(ack_frame_) - it->first >= |
| std::numeric_limits<uint8_t>::max()) { |
| it = ack_frame_.received_packet_times.erase(it); |
| } else { |
| ++it; |
| } |
| } |
| |
| #if QUIC_FRAME_DEBUG |
| QuicFrame frame = QuicFrame(&ack_frame_); |
| frame.delete_forbidden = true; |
| return frame; |
| #else // QUIC_FRAME_DEBUG |
| return QuicFrame(&ack_frame_); |
| #endif // QUIC_FRAME_DEBUG |
| } |
| |
| void QuicReceivedPacketManager::DontWaitForPacketsBefore( |
| QuicPacketNumber least_unacked) { |
| if (!least_unacked.IsInitialized()) { |
| return; |
| } |
| // ValidateAck() should fail if peer_least_packet_awaiting_ack shrinks. |
| QUICHE_DCHECK(!peer_least_packet_awaiting_ack_.IsInitialized() || |
| peer_least_packet_awaiting_ack_ <= least_unacked); |
| if (!peer_least_packet_awaiting_ack_.IsInitialized() || |
| least_unacked > peer_least_packet_awaiting_ack_) { |
| peer_least_packet_awaiting_ack_ = least_unacked; |
| bool packets_updated = ack_frame_.packets.RemoveUpTo(least_unacked); |
| if (packets_updated) { |
| // Ack frame gets updated because packets set is updated because of stop |
| // waiting frame. |
| ack_frame_updated_ = true; |
| } |
| } |
| QUICHE_DCHECK(ack_frame_.packets.Empty() || |
| !peer_least_packet_awaiting_ack_.IsInitialized() || |
| ack_frame_.packets.Min() >= peer_least_packet_awaiting_ack_); |
| } |
| |
| QuicTime::Delta QuicReceivedPacketManager::GetMaxAckDelay( |
| QuicPacketNumber last_received_packet_number, |
| const RttStats& rtt_stats) const { |
| if (AckFrequencyFrameReceived() || |
| last_received_packet_number < PeerFirstSendingPacketNumber() + |
| min_received_before_ack_decimation_) { |
| return local_max_ack_delay_; |
| } |
| |
| // Wait for the minimum of the ack decimation delay or the delayed ack time |
| // before sending an ack. |
| QuicTime::Delta ack_delay = std::min( |
| local_max_ack_delay_, rtt_stats.min_rtt() * ack_decimation_delay_); |
| return std::max(ack_delay, kAlarmGranularity); |
| } |
| |
| void QuicReceivedPacketManager::MaybeUpdateAckFrequency( |
| QuicPacketNumber last_received_packet_number) { |
| if (AckFrequencyFrameReceived()) { |
| // Skip Ack Decimation below after receiving an AckFrequencyFrame from the |
| // other end point. |
| return; |
| } |
| if (last_received_packet_number < |
| PeerFirstSendingPacketNumber() + min_received_before_ack_decimation_) { |
| return; |
| } |
| ack_frequency_ = unlimited_ack_decimation_ |
| ? std::numeric_limits<size_t>::max() |
| : kMaxRetransmittablePacketsBeforeAck; |
| } |
| |
| void QuicReceivedPacketManager::MaybeUpdateAckTimeout( |
| bool should_last_packet_instigate_acks, |
| QuicPacketNumber last_received_packet_number, |
| QuicTime last_packet_receipt_time, QuicTime now, |
| const RttStats* rtt_stats) { |
| if (!ack_frame_updated_) { |
| // ACK frame has not been updated, nothing to do. |
| return; |
| } |
| |
| if (!ignore_order_ && was_last_packet_missing_ && |
| last_sent_largest_acked_.IsInitialized() && |
| last_received_packet_number < last_sent_largest_acked_) { |
| // Only ack immediately if an ACK frame was sent with a larger largest acked |
| // than the newly received packet number. |
| ack_timeout_ = now; |
| return; |
| } |
| |
| if (!should_last_packet_instigate_acks) { |
| return; |
| } |
| |
| ++num_retransmittable_packets_received_since_last_ack_sent_; |
| |
| MaybeUpdateAckFrequency(last_received_packet_number); |
| if (num_retransmittable_packets_received_since_last_ack_sent_ >= |
| ack_frequency_) { |
| ack_timeout_ = now; |
| return; |
| } |
| |
| if (!ignore_order_ && HasNewMissingPackets()) { |
| ack_timeout_ = now; |
| return; |
| } |
| |
| QuicTime ack_timeout_base = now; |
| const bool quic_update_ack_timeout_on_receipt_time = |
| GetQuicReloadableFlag(quic_update_ack_timeout_on_receipt_time); |
| if (quic_update_ack_timeout_on_receipt_time) { |
| if (last_packet_receipt_time <= now) { |
| QUIC_CODE_COUNT(quic_update_ack_timeout_on_receipt_time); |
| ack_timeout_base = last_packet_receipt_time; |
| } else { |
| QUIC_CODE_COUNT(quic_update_ack_timeout_on_now); |
| ack_timeout_base = now; |
| } |
| } |
| QuicTime updated_ack_time = |
| ack_timeout_base + |
| GetMaxAckDelay(last_received_packet_number, *rtt_stats); |
| if (quic_update_ack_timeout_on_receipt_time) { |
| updated_ack_time = std::max(now, updated_ack_time); |
| } |
| if (!ack_timeout_.IsInitialized() || ack_timeout_ > updated_ack_time) { |
| ack_timeout_ = updated_ack_time; |
| } |
| } |
| |
| void QuicReceivedPacketManager::ResetAckStates() { |
| ack_frame_updated_ = false; |
| ack_timeout_ = QuicTime::Zero(); |
| num_retransmittable_packets_received_since_last_ack_sent_ = 0; |
| last_sent_largest_acked_ = LargestAcked(ack_frame_); |
| } |
| |
| bool QuicReceivedPacketManager::HasMissingPackets() const { |
| if (ack_frame_.packets.Empty()) { |
| return false; |
| } |
| if (ack_frame_.packets.NumIntervals() > 1) { |
| return true; |
| } |
| return peer_least_packet_awaiting_ack_.IsInitialized() && |
| ack_frame_.packets.Min() > peer_least_packet_awaiting_ack_; |
| } |
| |
| bool QuicReceivedPacketManager::HasNewMissingPackets() const { |
| if (one_immediate_ack_) { |
| return HasMissingPackets() && ack_frame_.packets.LastIntervalLength() == 1; |
| } |
| return HasMissingPackets() && |
| ack_frame_.packets.LastIntervalLength() <= kMaxPacketsAfterNewMissing; |
| } |
| |
| bool QuicReceivedPacketManager::ack_frame_updated() const { |
| return ack_frame_updated_; |
| } |
| |
| QuicPacketNumber QuicReceivedPacketManager::GetLargestObserved() const { |
| return LargestAcked(ack_frame_); |
| } |
| |
| QuicPacketNumber QuicReceivedPacketManager::PeerFirstSendingPacketNumber() |
| const { |
| if (!least_received_packet_number_.IsInitialized()) { |
| QUIC_BUG(quic_bug_10849_1) << "No packets have been received yet"; |
| return QuicPacketNumber(1); |
| } |
| return least_received_packet_number_; |
| } |
| |
| bool QuicReceivedPacketManager::IsAckFrameEmpty() const { |
| return ack_frame_.packets.Empty(); |
| } |
| |
| void QuicReceivedPacketManager::OnAckFrequencyFrame( |
| const QuicAckFrequencyFrame& frame) { |
| int64_t new_sequence_number = frame.sequence_number; |
| if (new_sequence_number <= last_ack_frequency_frame_sequence_number_) { |
| // Ignore old ACK_FREQUENCY frames. |
| return; |
| } |
| last_ack_frequency_frame_sequence_number_ = new_sequence_number; |
| ack_frequency_ = frame.packet_tolerance; |
| local_max_ack_delay_ = frame.max_ack_delay; |
| ignore_order_ = frame.ignore_order; |
| } |
| |
| } // namespace quic |