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// Copyright 2014 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/congestion_control/tcp_loss_algorithm.h"
#include <algorithm>
#include "base/logging.h"
#include "base/stl_util.h"
#include "net/quic/congestion_control/rtt_stats.h"
#include "net/quic/quic_ack_notifier_manager.h"
#include "net/quic/quic_unacked_packet_map.h"
#include "net/quic/test_tools/mock_clock.h"
#include "testing/gtest/include/gtest/gtest.h"
using std::vector;
namespace net {
namespace test {
namespace {
// Default packet length.
const uint32 kDefaultLength = 1000;
class TcpLossAlgorithmTest : public ::testing::Test {
protected:
TcpLossAlgorithmTest() : unacked_packets_(&ack_notifier_manager_) {
rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(100),
QuicTime::Delta::Zero(),
clock_.Now());
}
~TcpLossAlgorithmTest() override {
STLDeleteElements(&packets_);
}
void SendDataPacket(QuicPacketSequenceNumber sequence_number) {
packets_.push_back(new QuicEncryptedPacket(nullptr, kDefaultLength));
SerializedPacket packet(
sequence_number, PACKET_1BYTE_SEQUENCE_NUMBER, packets_.back(), 0,
new RetransmittableFrames(ENCRYPTION_NONE), false, false);
unacked_packets_.AddSentPacket(packet, 0, NOT_RETRANSMISSION, clock_.Now(),
1000, true);
}
void VerifyLosses(QuicPacketSequenceNumber largest_observed,
QuicPacketSequenceNumber* losses_expected,
size_t num_losses) {
SequenceNumberSet lost_packets =
loss_algorithm_.DetectLostPackets(
unacked_packets_, clock_.Now(), largest_observed, rtt_stats_);
EXPECT_EQ(num_losses, lost_packets.size());
for (size_t i = 0; i < num_losses; ++i) {
EXPECT_TRUE(ContainsKey(lost_packets, losses_expected[i]));
}
}
vector<QuicEncryptedPacket*> packets_;
AckNotifierManager ack_notifier_manager_;
QuicUnackedPacketMap unacked_packets_;
TCPLossAlgorithm loss_algorithm_;
RttStats rtt_stats_;
MockClock clock_;
};
TEST_F(TcpLossAlgorithmTest, NackRetransmit1Packet) {
const size_t kNumSentPackets = 5;
// Transmit 5 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
// No loss on one ack.
unacked_packets_.RemoveFromInFlight(2);
unacked_packets_.NackPacket(1, 1);
VerifyLosses(2, nullptr, 0);
// No loss on two acks.
unacked_packets_.RemoveFromInFlight(3);
unacked_packets_.NackPacket(1, 2);
VerifyLosses(3, nullptr, 0);
// Loss on three acks.
unacked_packets_.RemoveFromInFlight(4);
unacked_packets_.NackPacket(1, 3);
QuicPacketSequenceNumber lost[] = {1};
VerifyLosses(4, lost, arraysize(lost));
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(TcpLossAlgorithmTest, NackRetransmit1PacketWith1StretchAck) {
const size_t kNumSentPackets = 10;
// Transmit 10 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
// Nack the first packet 3 times in a single StretchAck.
unacked_packets_.NackPacket(1, 3);
unacked_packets_.RemoveFromInFlight(2);
unacked_packets_.RemoveFromInFlight(3);
unacked_packets_.RemoveFromInFlight(4);
QuicPacketSequenceNumber lost[] = { 1 };
VerifyLosses(4, lost, arraysize(lost));
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
// Ack a packet 3 packets ahead, causing a retransmit.
TEST_F(TcpLossAlgorithmTest, NackRetransmit1PacketSingleAck) {
const size_t kNumSentPackets = 10;
// Transmit 10 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
// Nack the first packet 3 times in an AckFrame with three missing packets.
unacked_packets_.NackPacket(1, 3);
unacked_packets_.NackPacket(2, 2);
unacked_packets_.NackPacket(3, 1);
unacked_packets_.RemoveFromInFlight(4);
QuicPacketSequenceNumber lost[] = { 1 };
VerifyLosses(4, lost, arraysize(lost));
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(TcpLossAlgorithmTest, EarlyRetransmit1Packet) {
const size_t kNumSentPackets = 2;
// Transmit 2 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
// Early retransmit when the final packet gets acked and the first is nacked.
unacked_packets_.RemoveFromInFlight(2);
unacked_packets_.NackPacket(1, 1);
VerifyLosses(2, nullptr, 0);
EXPECT_EQ(clock_.Now().Add(rtt_stats_.smoothed_rtt().Multiply(1.25)),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(rtt_stats_.latest_rtt().Multiply(1.25));
QuicPacketSequenceNumber lost[] = { 1 };
VerifyLosses(2, lost, arraysize(lost));
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(TcpLossAlgorithmTest, 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(rtt_stats_.smoothed_rtt().Multiply(0.25));
}
}
// Early retransmit when the final packet gets acked and 1.25 RTTs have
// elapsed since the packets were sent.
unacked_packets_.RemoveFromInFlight(kNumSentPackets);
// This simulates a single ack following multiple missing packets with FACK.
for (size_t i = 1; i < kNumSentPackets; ++i) {
unacked_packets_.NackPacket(i, kNumSentPackets - i);
}
QuicPacketSequenceNumber lost[] = { 1, 2 };
VerifyLosses(kNumSentPackets, lost, arraysize(lost));
// 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().Add(rtt_stats_.smoothed_rtt()),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(rtt_stats_.smoothed_rtt());
QuicPacketSequenceNumber lost2[] = { 1, 2, 3 };
VerifyLosses(kNumSentPackets, lost2, arraysize(lost2));
EXPECT_EQ(clock_.Now().Add(rtt_stats_.smoothed_rtt().Multiply(0.25)),
loss_algorithm_.GetLossTimeout());
clock_.AdvanceTime(rtt_stats_.smoothed_rtt().Multiply(0.25));
QuicPacketSequenceNumber lost3[] = { 1, 2, 3, 4 };
VerifyLosses(kNumSentPackets, lost3, arraysize(lost3));
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(TcpLossAlgorithmTest, DontEarlyRetransmitNeuteredPacket) {
const size_t kNumSentPackets = 2;
// Transmit 2 packets.
for (size_t i = 1; i <= kNumSentPackets; ++i) {
SendDataPacket(i);
}
// Neuter packet 1.
unacked_packets_.RemoveRetransmittability(1);
// Early retransmit when the final packet gets acked and the first is nacked.
unacked_packets_.IncreaseLargestObserved(2);
unacked_packets_.RemoveFromInFlight(2);
unacked_packets_.NackPacket(1, 1);
VerifyLosses(2, nullptr, 0);
EXPECT_EQ(QuicTime::Zero(), loss_algorithm_.GetLossTimeout());
}
TEST_F(TcpLossAlgorithmTest, AlwaysLosePacketSent1RTTEarlier) {
// Transmit 1 packet and then wait an rtt plus 1ms.
SendDataPacket(1);
clock_.AdvanceTime(
rtt_stats_.smoothed_rtt().Add(QuicTime::Delta::FromMilliseconds(1)));
// Transmit 2 packets.
SendDataPacket(2);
SendDataPacket(3);
// Wait another RTT and ack 2.
clock_.AdvanceTime(rtt_stats_.smoothed_rtt());
unacked_packets_.IncreaseLargestObserved(2);
unacked_packets_.RemoveFromInFlight(2);
unacked_packets_.NackPacket(1, 1);
QuicPacketSequenceNumber lost[] = {1};
VerifyLosses(2, lost, arraysize(lost));
}
} // namespace
} // namespace test
} // namespace net
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