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// 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 <cstddef>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>
#include "net/third_party/quiche/src/quic/core/congestion_control/pacing_sender.h"
#include "net/third_party/quiche/src/quic/core/congestion_control/rtt_stats.h"
#include "net/third_party/quiche/src/quic/core/congestion_control/send_algorithm_interface.h"
#include "net/third_party/quiche/src/quic/core/congestion_control/uber_loss_algorithm.h"
#include "net/third_party/quiche/src/quic/core/proto/cached_network_parameters_proto.h"
#include "net/third_party/quiche/src/quic/core/quic_packets.h"
#include "net/third_party/quiche/src/quic/core/quic_pending_retransmission.h"
#include "net/third_party/quiche/src/quic/core/quic_sustained_bandwidth_recorder.h"
#include "net/third_party/quiche/src/quic/core/quic_transmission_info.h"
#include "net/third_party/quiche/src/quic/core/quic_types.h"
#include "net/third_party/quiche/src/quic/core/quic_unacked_packet_map.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_containers.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_export.h"
namespace quic {
namespace test {
class QuicConnectionPeer;
class QuicSentPacketManagerPeer;
} // namespace test
class QuicClock;
class QuicConfig;
struct QuicConnectionStats;
// Class which tracks the set of packets sent on a QUIC connection and contains
// a send algorithm to decide when to send new packets. It keeps track of any
// retransmittable data associated with each packet. If a packet is
// retransmitted, it will keep track of each version of a packet so that if a
// previous transmission is acked, the data will not be retransmitted.
class QUIC_EXPORT_PRIVATE QuicSentPacketManager {
// Interface which gets callbacks from the QuicSentPacketManager at
// interesting points. Implementations must not mutate the state of
// the packet manager or connection as a result of these callbacks.
class QUIC_EXPORT_PRIVATE DebugDelegate {
virtual ~DebugDelegate() {}
// Called when a spurious retransmission is detected.
virtual void OnSpuriousPacketRetransmission(
TransmissionType /*transmission_type*/,
QuicByteCount /*byte_size*/) {}
virtual void OnIncomingAck(QuicPacketNumber /*ack_packet_number*/,
const QuicAckFrame& /*ack_frame*/,
QuicTime /*ack_receive_time*/,
QuicPacketNumber /*largest_observed*/,
bool /*rtt_updated*/,
QuicPacketNumber /*least_unacked_sent_packet*/) {
virtual void OnPacketLoss(QuicPacketNumber /*lost_packet_number*/,
TransmissionType /*transmission_type*/,
QuicTime /*detection_time*/) {}
virtual void OnApplicationLimited() {}
virtual void OnAdjustNetworkParameters(QuicBandwidth /*bandwidth*/,
QuicTime::Delta /*rtt*/,
QuicByteCount /*old_cwnd*/,
QuicByteCount /*new_cwnd*/) {}
// Interface which gets callbacks from the QuicSentPacketManager when
// network-related state changes. Implementations must not mutate the
// state of the packet manager as a result of these callbacks.
class QUIC_EXPORT_PRIVATE NetworkChangeVisitor {
virtual ~NetworkChangeVisitor() {}
// Called when congestion window or RTT may have changed.
virtual void OnCongestionChange() = 0;
// Called when the Path MTU may have increased.
virtual void OnPathMtuIncreased(QuicPacketLength packet_size) = 0;
QuicSentPacketManager(Perspective perspective,
const QuicClock* clock,
QuicRandom* random,
QuicConnectionStats* stats,
CongestionControlType congestion_control_type,
LossDetectionType loss_type);
QuicSentPacketManager(const QuicSentPacketManager&) = delete;
QuicSentPacketManager& operator=(const QuicSentPacketManager&) = delete;
virtual ~QuicSentPacketManager();
virtual void SetFromConfig(const QuicConfig& config);
// Pass the CachedNetworkParameters to the send algorithm.
void ResumeConnectionState(
const CachedNetworkParameters& cached_network_params,
bool max_bandwidth_resumption);
void SetMaxPacingRate(QuicBandwidth max_pacing_rate) {
QuicBandwidth MaxPacingRate() const {
return pacing_sender_.max_pacing_rate();
// Set handshake_confirmed_ to true and neuter packets in HANDSHAKE packet
// number space.
void SetHandshakeConfirmed();
// Requests retransmission of all unacked packets of |retransmission_type|.
// The behavior of this method depends on the value of |retransmission_type|:
// ALL_UNACKED_RETRANSMISSION - All unacked packets will be retransmitted.
// This can happen, for example, after a version negotiation packet has been
// received and all packets needs to be retransmitted with the new version.
// ALL_INITIAL_RETRANSMISSION - Only initially encrypted packets will be
// retransmitted. This can happen, for example, when a CHLO has been rejected
// and the previously encrypted data needs to be encrypted with a new key.
void RetransmitUnackedPackets(TransmissionType retransmission_type);
// Notify the sent packet manager of an external network measurement or
// prediction for either |bandwidth| or |rtt|; either can be empty.
void AdjustNetworkParameters(QuicBandwidth bandwidth,
QuicTime::Delta rtt,
bool allow_cwnd_to_decrease);
// Retransmits the oldest pending packet there is still a tail loss probe
// pending. Invoked after OnRetransmissionTimeout.
bool MaybeRetransmitTailLossProbe();
// Retransmits the oldest pending packet.
bool MaybeRetransmitOldestPacket(TransmissionType type);
// Removes the retransmittable frames from all unencrypted packets to ensure
// they don't get retransmitted.
// TODO(fayang): Consider replace this function with NeuterHandshakePackets.
void NeuterUnencryptedPackets();
// Returns true if there are pending retransmissions.
// Not const because retransmissions may be cancelled before returning.
bool HasPendingRetransmissions() const {
return !pending_retransmissions_.empty();
// Retrieves the next pending retransmission. You must ensure that
// there are pending retransmissions prior to calling this function.
QuicPendingRetransmission NextPendingRetransmission();
// Returns true if there's outstanding crypto data.
bool HasUnackedCryptoPackets() const {
return unacked_packets_.HasPendingCryptoPackets();
// Returns true if there are packets in flight expecting to be acknowledged.
bool HasInFlightPackets() const {
return unacked_packets_.HasInFlightPackets();
// Returns the smallest packet number of a serialized packet which has not
// been acked by the peer.
QuicPacketNumber GetLeastUnacked() const {
return unacked_packets_.GetLeastUnacked();
// Called when we have sent bytes to the peer. This informs the manager both
// the number of bytes sent and if they were retransmitted. Returns true if
// the sender should reset the retransmission timer.
bool OnPacketSent(SerializedPacket* serialized_packet,
QuicPacketNumber original_packet_number,
QuicTime sent_time,
TransmissionType transmission_type,
HasRetransmittableData has_retransmittable_data);
// Called when the retransmission timer expires.
void OnRetransmissionTimeout();
// Calculate the time until we can send the next packet to the wire.
// Note 1: When kUnknownWaitTime is returned, there is no need to poll
// TimeUntilSend again until we receive an OnIncomingAckFrame event.
// Note 2: Send algorithms may or may not use |retransmit| in their
// calculations.
QuicTime::Delta TimeUntilSend(QuicTime now) const;
// Returns the current delay for the retransmission timer, which may send
// either a tail loss probe or do a full RTO. Returns QuicTime::Zero() if
// there are no retransmittable packets.
const QuicTime GetRetransmissionTime() const;
// Returns the current delay for the path degrading timer, which is used to
// notify the session that this connection is degrading.
const QuicTime::Delta GetPathDegradingDelay() const;
const RttStats* GetRttStats() const { return &rtt_stats_; }
// Returns the estimated bandwidth calculated by the congestion algorithm.
QuicBandwidth BandwidthEstimate() const {
return send_algorithm_->BandwidthEstimate();
const QuicSustainedBandwidthRecorder* SustainedBandwidthRecorder() const {
return &sustained_bandwidth_recorder_;
// Returns the size of the current congestion window in number of
// kDefaultTCPMSS-sized segments. Note, this is not the *available* window.
// Some send algorithms may not use a congestion window and will return 0.
QuicPacketCount GetCongestionWindowInTcpMss() const {
return send_algorithm_->GetCongestionWindow() / kDefaultTCPMSS;
// Returns the number of packets of length |max_packet_length| which fit in
// the current congestion window. More packets may end up in flight if the
// congestion window has been recently reduced, of if non-full packets are
// sent.
QuicPacketCount EstimateMaxPacketsInFlight(
QuicByteCount max_packet_length) const {
return send_algorithm_->GetCongestionWindow() / max_packet_length;
// Returns the size of the current congestion window size in bytes.
QuicByteCount GetCongestionWindowInBytes() const {
return send_algorithm_->GetCongestionWindow();
// Returns the size of the slow start congestion window in nume of 1460 byte
// TCP segments, aka ssthresh. Some send algorithms do not define a slow
// start threshold and will return 0.
QuicPacketCount GetSlowStartThresholdInTcpMss() const {
return send_algorithm_->GetSlowStartThreshold() / kDefaultTCPMSS;
// Return the total time spent in slow start so far. If the sender is
// currently in slow start, the return value will include the duration between
// the most recent entry to slow start and now.
// Only implemented for BBR. Return QuicTime::Delta::Infinite() for other
// congestion controllers.
QuicTime::Delta GetSlowStartDuration() const;
// Returns debugging information about the state of the congestion controller.
std::string GetDebugState() const;
// Returns the number of bytes that are considered in-flight, i.e. not lost or
// acknowledged.
QuicByteCount GetBytesInFlight() const {
return unacked_packets_.bytes_in_flight();
// No longer retransmit data for |stream_id|.
void CancelRetransmissionsForStream(QuicStreamId stream_id);
// Called when peer address changes and the connection migrates.
void OnConnectionMigration(AddressChangeType type);
// Called when an ack frame is initially parsed.
void OnAckFrameStart(QuicPacketNumber largest_acked,
QuicTime::Delta ack_delay_time,
QuicTime ack_receive_time);
// Called when ack range [start, end) is received. Populates packets_acked_
// with newly acked packets.
void OnAckRange(QuicPacketNumber start, QuicPacketNumber end);
// Called when a timestamp is processed. If it's present in packets_acked_,
// the timestamp field is set. Otherwise, the timestamp is ignored.
void OnAckTimestamp(QuicPacketNumber packet_number, QuicTime timestamp);
// Called when an ack frame is parsed completely.
AckResult OnAckFrameEnd(QuicTime ack_receive_time,
QuicPacketNumber ack_packet_number,
EncryptionLevel ack_decrypted_level);
// Called to enable/disable letting session decide what to write.
void SetSessionDecideWhatToWrite(bool session_decides_what_to_write) {
void EnableMultiplePacketNumberSpacesSupport();
void SetDebugDelegate(DebugDelegate* debug_delegate);
void SetPacingAlarmGranularity(QuicTime::Delta alarm_granularity) {
QuicPacketNumber GetLargestObserved() const {
return unacked_packets_.largest_acked();
QuicPacketNumber GetLargestAckedPacket(
EncryptionLevel decrypted_packet_level) const;
QuicPacketNumber GetLargestSentPacket() const {
return unacked_packets_.largest_sent_packet();
QuicPacketNumber GetLargestSentPacket(
EncryptionLevel decrypted_packet_level) const;
QuicPacketNumber GetLargestPacketPeerKnowsIsAcked(
EncryptionLevel decrypted_packet_level) const;
void SetNetworkChangeVisitor(NetworkChangeVisitor* visitor) {
network_change_visitor_ = visitor;
bool InSlowStart() const { return send_algorithm_->InSlowStart(); }
size_t GetConsecutiveRtoCount() const { return consecutive_rto_count_; }
size_t GetConsecutiveTlpCount() const { return consecutive_tlp_count_; }
void OnApplicationLimited();
const SendAlgorithmInterface* GetSendAlgorithm() const {
return send_algorithm_.get();
void SetSessionNotifier(SessionNotifierInterface* session_notifier) {
QuicTime GetNextReleaseTime() const;
QuicPacketCount initial_congestion_window() const {
return initial_congestion_window_;
QuicPacketNumber largest_packet_peer_knows_is_acked() const {
return largest_packet_peer_knows_is_acked_;
bool handshake_confirmed() const { return handshake_confirmed_; }
bool session_decides_what_to_write() const {
return unacked_packets_.session_decides_what_to_write();
size_t pending_timer_transmission_count() const {
return pending_timer_transmission_count_;
QuicTime::Delta local_max_ack_delay() const { return local_max_ack_delay_; }
void set_local_max_ack_delay(QuicTime::Delta local_max_ack_delay) {
// The delayed ack time should never be more than one half the min RTO time.
DCHECK_LE(local_max_ack_delay, (min_rto_timeout_ * 0.5));
local_max_ack_delay_ = local_max_ack_delay;
QuicTime::Delta peer_max_ack_delay() const { return peer_max_ack_delay_; }
void set_peer_max_ack_delay(QuicTime::Delta peer_max_ack_delay) {
peer_max_ack_delay_ = peer_max_ack_delay;
const QuicUnackedPacketMap& unacked_packets() const {
return unacked_packets_;
// Sets the send algorithm to the given congestion control type and points the
// pacing sender at |send_algorithm_|. Can be called any number of times.
void SetSendAlgorithm(CongestionControlType congestion_control_type);
// Sets the send algorithm to |send_algorithm| and points the pacing sender at
// |send_algorithm_|. Takes ownership of |send_algorithm|. Can be called any
// number of times.
// Setting the send algorithm once the connection is underway is dangerous.
void SetSendAlgorithm(SendAlgorithmInterface* send_algorithm);
bool supports_multiple_packet_number_spaces() const {
return unacked_packets_.supports_multiple_packet_number_spaces();
bool ignore_tlpr_if_no_pending_stream_data() const {
return ignore_tlpr_if_no_pending_stream_data_;
bool fix_rto_retransmission() const { return fix_rto_retransmission_; }
friend class test::QuicConnectionPeer;
friend class test::QuicSentPacketManagerPeer;
// The retransmission timer is a single timer which switches modes depending
// upon connection state.
enum RetransmissionTimeoutMode {
// A conventional TCP style RTO.
// A tail loss probe. By default, QUIC sends up to two before RTOing.
// Retransmission of handshake packets prior to handshake completion.
// Re-invoke the loss detection when a packet is not acked before the
// loss detection algorithm expects.
typedef QuicLinkedHashMap<QuicPacketNumber,
// Returns the current retransmission mode.
RetransmissionTimeoutMode GetRetransmissionMode() const;
// Retransmits all crypto stream packets.
void RetransmitCryptoPackets();
// Retransmits two packets for an RTO and removes any non-retransmittable
// packets from flight.
void RetransmitRtoPackets();
// Returns the timeout for retransmitting crypto handshake packets.
const QuicTime::Delta GetCryptoRetransmissionDelay() const;
// Returns the timeout for a new tail loss probe. |consecutive_tlp_count| is
// the number of consecutive tail loss probes that have already been sent.
const QuicTime::Delta GetTailLossProbeDelay(
size_t consecutive_tlp_count) const;
// Calls GetTailLossProbeDelay() with values from the current state of this
// packet manager as its params.
const QuicTime::Delta GetTailLossProbeDelay() const {
return GetTailLossProbeDelay(consecutive_tlp_count_);
// Returns the retransmission timeout, after which a full RTO occurs.
// |consecutive_rto_count| is the number of consecutive RTOs that have already
// occurred.
const QuicTime::Delta GetRetransmissionDelay(
size_t consecutive_rto_count) const;
// Calls GetRetransmissionDelay() with values from the current state of this
// packet manager as its params.
const QuicTime::Delta GetRetransmissionDelay() const {
return GetRetransmissionDelay(consecutive_rto_count_);
// Returns the newest transmission associated with a packet.
QuicPacketNumber GetNewestRetransmission(
QuicPacketNumber packet_number,
const QuicTransmissionInfo& transmission_info) const;
// Update the RTT if the ack is for the largest acked packet number.
// Returns true if the rtt was updated.
bool MaybeUpdateRTT(QuicPacketNumber largest_acked,
QuicTime::Delta ack_delay_time,
QuicTime ack_receive_time);
// Invokes the loss detection algorithm and loses and retransmits packets if
// necessary.
void InvokeLossDetection(QuicTime time);
// Invokes OnCongestionEvent if |rtt_updated| is true, there are pending acks,
// or pending losses. Clears pending acks and pending losses afterwards.
// |prior_in_flight| is the number of bytes in flight before the losses or
// acks, |event_time| is normally the timestamp of the ack packet which caused
// the event, although it can be the time at which loss detection was
// triggered.
void MaybeInvokeCongestionEvent(bool rtt_updated,
QuicByteCount prior_in_flight,
QuicTime event_time);
// Removes the retransmittability and in flight properties from the packet at
// |info| due to receipt by the peer.
void MarkPacketHandled(QuicPacketNumber packet_number,
QuicTransmissionInfo* info,
QuicTime::Delta ack_delay_time,
QuicTime receive_timestamp);
// Request that |packet_number| be retransmitted after the other pending
// retransmissions. Does not add it to the retransmissions if it's already
// a pending retransmission.
void MarkForRetransmission(QuicPacketNumber packet_number,
TransmissionType transmission_type);
// Performs whatever work is need to retransmit the data correctly, either
// by retransmitting the frames directly or by notifying that the frames
// are lost.
void HandleRetransmission(TransmissionType transmission_type,
QuicTransmissionInfo* transmission_info);
// Called after packets have been marked handled with last received ack frame.
void PostProcessNewlyAckedPackets(QuicPacketNumber ack_packet_number,
const QuicAckFrame& ack_frame,
QuicTime ack_receive_time,
bool rtt_updated,
QuicByteCount prior_bytes_in_flight);
// Notify observers that packet with QuicTransmissionInfo |info| is a spurious
// retransmission. It is caller's responsibility to guarantee the packet with
// QuicTransmissionInfo |info| is a spurious retransmission before calling
// this function.
void RecordOneSpuriousRetransmission(const QuicTransmissionInfo& info);
// Notify observers about spurious retransmits of packet with
// QuicTransmissionInfo |info|.
void RecordSpuriousRetransmissions(const QuicTransmissionInfo& info,
QuicPacketNumber acked_packet_number);
// Sets the initial RTT of the connection.
void SetInitialRtt(QuicTime::Delta rtt);
// Should only be called from constructor.
LossDetectionInterface* GetInitialLossAlgorithm();
// Called when handshake is confirmed to remove the retransmittable frames
// from all packets of HANDSHAKE_DATA packet number space to ensure they don't
// get retransmitted and will eventually be removed from unacked packets map.
// Please note, this only applies to QUIC Crypto and needs to be changed when
// switches to IETF QUIC with QUIC TLS.
void NeuterHandshakePackets();
// Newly serialized retransmittable packets are added to this map, which
// contains owning pointers to any contained frames. If a packet is
// retransmitted, this map will contain entries for both the old and the new
// packet. The old packet's retransmittable frames entry will be nullptr,
// while the new packet's entry will contain the frames to retransmit.
// If the old packet is acked before the new packet, then the old entry will
// be removed from the map and the new entry's retransmittable frames will be
// set to nullptr.
QuicUnackedPacketMap unacked_packets_;
// Pending retransmissions which have not been packetized and sent yet.
PendingRetransmissionMap pending_retransmissions_;
const QuicClock* clock_;
QuicRandom* random_;
QuicConnectionStats* stats_;
DebugDelegate* debug_delegate_;
NetworkChangeVisitor* network_change_visitor_;
QuicPacketCount initial_congestion_window_;
RttStats rtt_stats_;
std::unique_ptr<SendAlgorithmInterface> send_algorithm_;
// Not owned. Always points to |general_loss_algorithm_| outside of tests.
LossDetectionInterface* loss_algorithm_;
UberLossAlgorithm uber_loss_algorithm_;
// Tracks the first RTO packet. If any packet before that packet gets acked,
// it indicates the RTO was spurious and should be reversed(F-RTO).
QuicPacketNumber first_rto_transmission_;
// Number of times the RTO timer has fired in a row without receiving an ack.
size_t consecutive_rto_count_;
// Number of times the tail loss probe has been sent.
size_t consecutive_tlp_count_;
// Number of times the crypto handshake has been retransmitted.
size_t consecutive_crypto_retransmission_count_;
// Number of pending transmissions of TLP, RTO, or crypto packets.
size_t pending_timer_transmission_count_;
// Maximum number of tail loss probes to send before firing an RTO.
size_t max_tail_loss_probes_;
// Maximum number of packets to send upon RTO.
QuicPacketCount max_rto_packets_;
// If true, send the TLP at 0.5 RTT.
bool enable_half_rtt_tail_loss_probe_;
bool using_pacing_;
// If true, use the new RTO with loss based CWND reduction instead of the send
// algorithms's OnRetransmissionTimeout to reduce the congestion window.
bool use_new_rto_;
// If true, use a more conservative handshake retransmission policy.
bool conservative_handshake_retransmits_;
// The minimum TLP timeout.
QuicTime::Delta min_tlp_timeout_;
// The minimum RTO.
QuicTime::Delta min_rto_timeout_;
// Whether to use IETF style TLP that includes the max ack delay.
bool ietf_style_tlp_;
// IETF style TLP, but with a 2x multiplier instead of 1.5x.
bool ietf_style_2x_tlp_;
// Vectors packets acked and lost as a result of the last congestion event.
AckedPacketVector packets_acked_;
LostPacketVector packets_lost_;
// Largest newly acknowledged packet.
QuicPacketNumber largest_newly_acked_;
// Largest packet in bytes ever acknowledged.
QuicPacketLength largest_mtu_acked_;
// Replaces certain calls to |send_algorithm_| when |using_pacing_| is true.
// Calls into |send_algorithm_| for the underlying congestion control.
PacingSender pacing_sender_;
// Set to true after the crypto handshake has successfully completed. After
// this is true we no longer use HANDSHAKE_MODE, and further frames sent on
// the crypto stream (i.e. SCUP messages) are treated like normal
// retransmittable frames.
bool handshake_confirmed_;
// Records bandwidth from server to client in normal operation, over periods
// of time with no loss events.
QuicSustainedBandwidthRecorder sustained_bandwidth_recorder_;
// The largest acked value that was sent in an ack, which has then been acked.
QuicPacketNumber largest_packet_peer_knows_is_acked_;
// The largest acked value that was sent in an ack, which has then been acked
// for per packet number space. Only used when connection supports multiple
// packet number spaces.
// The local node's maximum ack delay time. This is the maximum amount of
// time to wait before sending an acknowledgement.
QuicTime::Delta local_max_ack_delay_;
// The maximum ACK delay time that the peer uses. Initialized to be the
// same as local_max_ack_delay_, may be changed via transport parameter
// negotiation.
QuicTime::Delta peer_max_ack_delay_;
// Latest received ack frame.
QuicAckFrame last_ack_frame_;
// Record whether RTT gets updated by last largest acked..
bool rtt_updated_;
// A reverse iterator of last_ack_frame_.packets. This is reset in
// OnAckRangeStart, and gradually moves in OnAckRange..
PacketNumberQueue::const_reverse_iterator acked_packets_iter_;
// Latched value of quic_loss_removes_from_inflight.
const bool loss_removes_from_inflight_;
// Latched value of quic_ignore_tlpr_if_no_pending_stream_data.
const bool ignore_tlpr_if_no_pending_stream_data_;
// Latched value of quic_fix_rto_retransmission.
const bool fix_rto_retransmission_;
} // namespace quic