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// Copyright 2015 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 "quiche/quic/core/congestion_control/general_loss_algorithm.h"
#include <algorithm>
#include <cstdint>
#include <optional>
#include <vector>
#include "quiche/quic/core/congestion_control/rtt_stats.h"
#include "quiche/quic/core/quic_unacked_packet_map.h"
#include "quiche/quic/core/quic_utils.h"
#include "quiche/quic/platform/api/quic_flags.h"
#include "quiche/quic/platform/api/quic_test.h"
#include "quiche/quic/test_tools/mock_clock.h"
namespace quic {
namespace test {
namespace {
// Default packet length.
const uint32_t kDefaultLength = 1000;
class GeneralLossAlgorithmTest : public QuicTest {
protected:
GeneralLossAlgorithmTest() : unacked_packets_(Perspective::IS_CLIENT) {
rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(100),
QuicTime::Delta::Zero(), clock_.Now());
EXPECT_LT(0, rtt_stats_.smoothed_rtt().ToMicroseconds());
loss_algorithm_.Initialize(HANDSHAKE_DATA, nullptr);
}
~GeneralLossAlgorithmTest() override {}
void SendDataPacket(uint64_t packet_number,
QuicPacketLength encrypted_length) {
QuicStreamFrame frame;
frame.stream_id = QuicUtils::GetFirstBidirectionalStreamId(
CurrentSupportedVersions()[0].transport_version,
Perspective::IS_CLIENT);
SerializedPacket packet(QuicPacketNumber(packet_number),
PACKET_1BYTE_PACKET_NUMBER, nullptr,
encrypted_length, false, false);
packet.retransmittable_frames.push_back(QuicFrame(frame));
unacked_packets_.AddSentPacket(&packet, NOT_RETRANSMISSION, clock_.Now(),
true, true, ECN_NOT_ECT);
}
void SendDataPacket(uint64_t packet_number) {
SendDataPacket(packet_number, kDefaultLength);
}
void SendAckPacket(uint64_t packet_number) {
SerializedPacket packet(QuicPacketNumber(packet_number),
PACKET_1BYTE_PACKET_NUMBER, nullptr, kDefaultLength,
true, false);
unacked_packets_.AddSentPacket(&packet, NOT_RETRANSMISSION, clock_.Now(),
false, true, ECN_NOT_ECT);
}
void VerifyLosses(uint64_t largest_newly_acked,
const AckedPacketVector& packets_acked,
const std::vector<uint64_t>& losses_expected) {
return VerifyLosses(largest_newly_acked, packets_acked, losses_expected,
std::nullopt, std::nullopt);
}
void VerifyLosses(
uint64_t largest_newly_acked, const AckedPacketVector& packets_acked,
const std::vector<uint64_t>& losses_expected,
std::optional<QuicPacketCount> max_sequence_reordering_expected,
std::optional<QuicPacketCount> num_borderline_time_reorderings_expected) {
unacked_packets_.MaybeUpdateLargestAckedOfPacketNumberSpace(
APPLICATION_DATA, QuicPacketNumber(largest_newly_acked));
LostPacketVector lost_packets;
LossDetectionInterface::DetectionStats stats = loss_algorithm_.DetectLosses(
unacked_packets_, clock_.Now(), rtt_stats_,
QuicPacketNumber(largest_newly_acked), packets_acked, &lost_packets);
if (max_sequence_reordering_expected.has_value()) {
EXPECT_EQ(stats.sent_packets_max_sequence_reordering,
max_sequence_reordering_expected.value());
}
if (num_borderline_time_reorderings_expected.has_value()) {
EXPECT_EQ(stats.sent_packets_num_borderline_time_reorderings,
num_borderline_time_reorderings_expected.value());
}
ASSERT_EQ(losses_expected.size(), lost_packets.size());
for (size_t i = 0; i < losses_expected.size(); ++i) {
EXPECT_EQ(lost_packets[i].packet_number,
QuicPacketNumber(losses_expected[i]));
}
}
QuicUnackedPacketMap unacked_packets_;
GeneralLossAlgorithm loss_algorithm_;
RttStats rtt_stats_;
MockClock clock_;
};
TEST_F(GeneralLossAlgorithmTest, NackRetransmit1Packet) {
const size_t kNumSentPackets = 5;
// Transmit 5 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
AckedPacketVector packets_acked;
// No loss on one ack.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, std::vector<uint64_t>{}, 1, 0);
packets_acked.clear();
// No loss on two acks.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(3));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(3), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(3, packets_acked, std::vector<uint64_t>{}, 2, 0);
packets_acked.clear();
// Loss on three acks.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(4));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(4), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(4, packets_acked, {1}, 3, 0);
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
// A stretch ack is an ack that covers more than 1 packet of previously
// unacknowledged data.
TEST_F(GeneralLossAlgorithmTest, NackRetransmit1PacketWith1StretchAck) {
const size_t kNumSentPackets = 10;
// Transmit 10 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
AckedPacketVector packets_acked;
// Nack the first packet 3 times in a single StretchAck.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(3));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(3), kMaxOutgoingPacketSize, QuicTime::Zero()));
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(4));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(4), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(4, packets_acked, {1});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
// Ack a packet 3 packets ahead, causing a retransmit.
TEST_F(GeneralLossAlgorithmTest, NackRetransmit1PacketSingleAck) {
const size_t kNumSentPackets = 10;
// Transmit 10 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
AckedPacketVector packets_acked;
// Nack the first packet 3 times in an AckFrame with three missing packets.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(4));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(4), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(4, packets_acked, {1});
EXPECT_EQ(clock_.Now() + 1.25 * rtt_stats_.smoothed_rtt(),
loss_algorithm_.GetLossTimeout());
}
TEST_F(GeneralLossAlgorithmTest, EarlyRetransmit1Packet) {
const size_t kNumSentPackets = 2;
// Transmit 2 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
AckedPacketVector packets_acked;
// Early retransmit when the final packet gets acked and the first is nacked.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
EXPECT_EQ(clock_.Now() + 1.25 * rtt_stats_.smoothed_rtt(),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(1.13 * rtt_stats_.latest_rtt());
// If reordering_shift increases by one we should have detected a loss.
VerifyLosses(2, packets_acked, {}, /*max_sequence_reordering_expected=*/1,
/*num_borderline_time_reorderings_expected=*/1);
clock_.AdvanceTime(0.13 * rtt_stats_.latest_rtt());
VerifyLosses(2, packets_acked, {1});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(GeneralLossAlgorithmTest, EarlyRetransmitAllPackets) {
const size_t kNumSentPackets = 5;
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
// Advance the time 1/4 RTT between 3 and 4.
if (i == 3) {
clock_.AdvanceTime(0.25 * rtt_stats_.smoothed_rtt());
}
}
AckedPacketVector packets_acked;
// Early retransmit when the final packet gets acked and 1.25 RTTs have
// elapsed since the packets were sent.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(kNumSentPackets));
packets_acked.push_back(AckedPacket(QuicPacketNumber(kNumSentPackets),
kMaxOutgoingPacketSize,
QuicTime::Zero()));
// This simulates a single ack following multiple missing packets with FACK.
VerifyLosses(kNumSentPackets, packets_acked, {1, 2});
packets_acked.clear();
// The time has already advanced 1/4 an RTT, so ensure the timeout is set
// 1.25 RTTs after the earliest pending packet(3), not the last(4).
EXPECT_EQ(clock_.Now() + rtt_stats_.smoothed_rtt(),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(rtt_stats_.smoothed_rtt());
VerifyLosses(kNumSentPackets, packets_acked, {3});
EXPECT_EQ(clock_.Now() + 0.25 * rtt_stats_.smoothed_rtt(),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(0.25 * rtt_stats_.smoothed_rtt());
VerifyLosses(kNumSentPackets, packets_acked, {4});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(GeneralLossAlgorithmTest, DontEarlyRetransmitNeuteredPacket) {
const size_t kNumSentPackets = 2;
// Transmit 2 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
AckedPacketVector packets_acked;
// Neuter packet 1.
unacked_packets_.RemoveRetransmittability(QuicPacketNumber(1));
clock_.AdvanceTime(rtt_stats_.smoothed_rtt());
// Early retransmit when the final packet gets acked and the first is nacked.
unacked_packets_.MaybeUpdateLargestAckedOfPacketNumberSpace(
APPLICATION_DATA, QuicPacketNumber(2));
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, std::vector<uint64_t>{});
EXPECT_EQ(clock_.Now() + 0.25 * rtt_stats_.smoothed_rtt(),
loss_algorithm_.GetLossTimeout());
}
TEST_F(GeneralLossAlgorithmTest, EarlyRetransmitWithLargerUnackablePackets) {
// Transmit 2 data packets and one ack.
SendDataPacket(1);
SendDataPacket(2);
SendAckPacket(3);
AckedPacketVector packets_acked;
clock_.AdvanceTime(rtt_stats_.smoothed_rtt());
// Early retransmit when the final packet gets acked and the first is nacked.
unacked_packets_.MaybeUpdateLargestAckedOfPacketNumberSpace(
APPLICATION_DATA, QuicPacketNumber(2));
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
EXPECT_EQ(clock_.Now() + 0.25 * rtt_stats_.smoothed_rtt(),
loss_algorithm_.GetLossTimeout());
// The packet should be lost once the loss timeout is reached.
clock_.AdvanceTime(0.25 * rtt_stats_.latest_rtt());
VerifyLosses(2, packets_acked, {1});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(GeneralLossAlgorithmTest, AlwaysLosePacketSent1RTTEarlier) {
// Transmit 1 packet and then wait an rtt plus 1ms.
SendDataPacket(1);
clock_.AdvanceTime(rtt_stats_.smoothed_rtt() +
QuicTime::Delta::FromMilliseconds(1));
// Transmit 2 packets.
SendDataPacket(2);
SendDataPacket(3);
AckedPacketVector packets_acked;
// Wait another RTT and ack 2.
clock_.AdvanceTime(rtt_stats_.smoothed_rtt());
unacked_packets_.MaybeUpdateLargestAckedOfPacketNumberSpace(
APPLICATION_DATA, QuicPacketNumber(2));
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, {1});
}
TEST_F(GeneralLossAlgorithmTest, IncreaseTimeThresholdUponSpuriousLoss) {
loss_algorithm_.enable_adaptive_time_threshold();
loss_algorithm_.set_reordering_shift(kDefaultLossDelayShift);
EXPECT_EQ(kDefaultLossDelayShift, loss_algorithm_.reordering_shift());
EXPECT_TRUE(loss_algorithm_.use_adaptive_time_threshold());
const size_t kNumSentPackets = 10;
// Transmit 2 packets at 1/10th an RTT interval.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
clock_.AdvanceTime(0.1 * rtt_stats_.smoothed_rtt());
}
EXPECT_EQ(QuicTime::Zero() + rtt_stats_.smoothed_rtt(), clock_.Now());
AckedPacketVector packets_acked;
// Expect the timer to not be set.
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
// Packet 1 should not be lost until 1/4 RTTs pass.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
// Expect the timer to be set to 1/4 RTT's in the future.
EXPECT_EQ(rtt_stats_.smoothed_rtt() * (1.0f / 4),
loss_algorithm_.GetLossTimeout() - clock_.Now());
VerifyLosses(2, packets_acked, std::vector<uint64_t>{});
clock_.AdvanceTime(rtt_stats_.smoothed_rtt() * (1.0f / 4));
VerifyLosses(2, packets_acked, {1});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
// Retransmit packet 1 as 11 and 2 as 12.
SendDataPacket(11);
SendDataPacket(12);
// Advance the time 1/4 RTT and indicate the loss was spurious.
// The new threshold should be 1/2 RTT.
clock_.AdvanceTime(rtt_stats_.smoothed_rtt() * (1.0f / 4));
loss_algorithm_.SpuriousLossDetected(unacked_packets_, rtt_stats_,
clock_.Now(), QuicPacketNumber(1),
QuicPacketNumber(2));
EXPECT_EQ(1, loss_algorithm_.reordering_shift());
}
TEST_F(GeneralLossAlgorithmTest, IncreaseReorderingThresholdUponSpuriousLoss) {
loss_algorithm_.set_use_adaptive_reordering_threshold(true);
for (size_t i = 1; i <= 4; ++i) {
SendDataPacket(i);
}
// Acking 4 causes 1 detected lost.
AckedPacketVector packets_acked;
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(4));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(4), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(4, packets_acked, std::vector<uint64_t>{1});
packets_acked.clear();
// Retransmit 1 as 5.
SendDataPacket(5);
// Acking 1 such that it was detected lost spuriously.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(1));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(1), kMaxOutgoingPacketSize, QuicTime::Zero()));
loss_algorithm_.SpuriousLossDetected(unacked_packets_, rtt_stats_,
clock_.Now(), QuicPacketNumber(1),
QuicPacketNumber(4));
VerifyLosses(4, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
// Verify acking 5 does not cause 2 detected lost.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(5));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(5), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(5, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
SendDataPacket(6);
// Acking 6 will causes 2 detected lost.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(6));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(6), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(6, packets_acked, std::vector<uint64_t>{2});
packets_acked.clear();
// Retransmit 2 as 7.
SendDataPacket(7);
// Acking 2 such that it was detected lost spuriously.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
loss_algorithm_.SpuriousLossDetected(unacked_packets_, rtt_stats_,
clock_.Now(), QuicPacketNumber(2),
QuicPacketNumber(6));
VerifyLosses(6, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
// Acking 7 will not cause 3 as detected lost.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(7));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(7), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(7, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
}
TEST_F(GeneralLossAlgorithmTest, DefaultIetfLossDetection) {
loss_algorithm_.set_reordering_shift(kDefaultIetfLossDelayShift);
for (size_t i = 1; i <= 6; ++i) {
SendDataPacket(i);
}
// Packet threshold loss detection.
AckedPacketVector packets_acked;
// No loss on one ack.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
// No loss on two acks.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(3));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(3), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(3, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
// Loss on three acks.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(4));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(4), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(4, packets_acked, {1});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
packets_acked.clear();
SendDataPacket(7);
// Time threshold loss detection.
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(6));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(6), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(6, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
EXPECT_EQ(clock_.Now() + rtt_stats_.smoothed_rtt() +
(rtt_stats_.smoothed_rtt() >> 3),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(rtt_stats_.smoothed_rtt() +
(rtt_stats_.smoothed_rtt() >> 3));
VerifyLosses(6, packets_acked, {5});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(GeneralLossAlgorithmTest, IetfLossDetectionWithOneFourthRttDelay) {
loss_algorithm_.set_reordering_shift(2);
SendDataPacket(1);
SendDataPacket(2);
AckedPacketVector packets_acked;
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(2));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(2), kMaxOutgoingPacketSize, QuicTime::Zero()));
VerifyLosses(2, packets_acked, std::vector<uint64_t>{});
packets_acked.clear();
EXPECT_EQ(clock_.Now() + rtt_stats_.smoothed_rtt() +
(rtt_stats_.smoothed_rtt() >> 2),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(rtt_stats_.smoothed_rtt() +
(rtt_stats_.smoothed_rtt() >> 2));
VerifyLosses(2, packets_acked, {1});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(GeneralLossAlgorithmTest, NoPacketThresholdForRuntPackets) {
loss_algorithm_.disable_packet_threshold_for_runt_packets();
for (size_t i = 1; i <= 6; ++i) {
SendDataPacket(i);
}
// Send a small packet.
SendDataPacket(7, /*encrypted_length=*/kDefaultLength / 2);
// No packet threshold for runt packet.
AckedPacketVector packets_acked;
unacked_packets_.RemoveFromInFlight(QuicPacketNumber(7));
packets_acked.push_back(AckedPacket(
QuicPacketNumber(7), kMaxOutgoingPacketSize, QuicTime::Zero()));
// Verify no packet is detected lost because packet 7 is a runt.
VerifyLosses(7, packets_acked, std::vector<uint64_t>{});
EXPECT_EQ(clock_.Now() + rtt_stats_.smoothed_rtt() +
(rtt_stats_.smoothed_rtt() >> 2),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(rtt_stats_.smoothed_rtt() +
(rtt_stats_.smoothed_rtt() >> 2));
// Verify packets are declared lost because time threshold has passed.
VerifyLosses(7, packets_acked, {1, 2, 3, 4, 5, 6});
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
} // namespace
} // namespace test
} // namespace quic