Update from chromium https://crrev.com/302282

net/quic/congestion_control/prr_sender_test.cc

+// Copyright (c) 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/prr_sender.h"
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "net/quic/crypto/crypto_protocol.h"
+#include "net/quic/quic_bandwidth.h"
+#include "net/quic/quic_protocol.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+namespace test {
+
+namespace {
+// Constant based on TCP defaults.
+const QuicByteCount kMaxSegmentSize = kDefaultTCPMSS;
+}  // namespace
+
+class PrrSenderTest : public ::testing::Test {};
+
+TEST_F(PrrSenderTest, SingleLossResultsInSendOnEveryOtherAck) {
+  PrrSender prr;
+  QuicPacketCount num_packets_in_flight = 50;
+  QuicByteCount bytes_in_flight = num_packets_in_flight * kMaxSegmentSize;
+  const QuicPacketCount ssthresh_after_loss = num_packets_in_flight / 2;
+  const QuicByteCount congestion_window = ssthresh_after_loss * kMaxSegmentSize;
+
+  prr.OnPacketLost(bytes_in_flight);
+  // Ack a packet. PRR allows one packet to leave immediately.
+  prr.OnPacketAcked(kMaxSegmentSize);
+  bytes_in_flight -= kMaxSegmentSize;
+  EXPECT_EQ(QuicTime::Delta::Zero(),
+            prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                              ssthresh_after_loss));
+  // Send retransmission.
+  prr.OnPacketSent(kMaxSegmentSize);
+  // PRR shouldn't allow sending any more packets.
+  EXPECT_EQ(QuicTime::Delta::Infinite(),
+            prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                              ssthresh_after_loss));
+
+  // One packet is lost, and one ack was consumed above. PRR now paces
+  // transmissions through the remaining 48 acks. PRR will alternatively
+  // disallow and allow a packet to be sent in response to an ack.
+  for (uint64 i = 0; i < ssthresh_after_loss - 1; ++i) {
+    // Ack a packet. PRR shouldn't allow sending a packet in response.
+    prr.OnPacketAcked(kMaxSegmentSize);
+    bytes_in_flight -= kMaxSegmentSize;
+    EXPECT_EQ(QuicTime::Delta::Infinite(),
+              prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                                ssthresh_after_loss));
+    // Ack another packet. PRR should now allow sending a packet in response.
+    prr.OnPacketAcked(kMaxSegmentSize);
+    bytes_in_flight -= kMaxSegmentSize;
+    EXPECT_EQ(QuicTime::Delta::Zero(),
+              prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                                ssthresh_after_loss));
+    // Send a packet in response.
+    prr.OnPacketSent(kMaxSegmentSize);
+    bytes_in_flight += kMaxSegmentSize;
+  }
+
+  // Since bytes_in_flight is now equal to congestion_window, PRR now maintains
+  // packet conservation, allowing one packet to be sent in response to an ack.
+  EXPECT_EQ(congestion_window, bytes_in_flight);
+  for (int i = 0; i < 10; ++i) {
+    // Ack a packet.
+    prr.OnPacketAcked(kMaxSegmentSize);
+    bytes_in_flight -= kMaxSegmentSize;
+    EXPECT_EQ(QuicTime::Delta::Zero(),
+              prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                                ssthresh_after_loss));
+    // Send a packet in response, since PRR allows it.
+    prr.OnPacketSent(kMaxSegmentSize);
+    bytes_in_flight += kMaxSegmentSize;
+
+    // Since bytes_in_flight is equal to the congestion_window,
+    // PRR disallows sending.
+    EXPECT_EQ(congestion_window, bytes_in_flight);
+    EXPECT_EQ(QuicTime::Delta::Infinite(),
+              prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                                ssthresh_after_loss));
+  }
+}
+
+TEST_F(PrrSenderTest, BurstLossResultsInSlowStart) {
+  PrrSender prr;
+  QuicByteCount bytes_in_flight = 20 * kMaxSegmentSize;
+  const QuicPacketCount num_packets_lost = 13;
+  const QuicPacketCount ssthresh_after_loss = 10;
+  const QuicByteCount congestion_window = ssthresh_after_loss * kMaxSegmentSize;
+
+  // Lose 13 packets.
+  bytes_in_flight -= num_packets_lost * kMaxSegmentSize;
+  prr.OnPacketLost(bytes_in_flight);
+
+  // PRR-SSRB will allow the following 3 acks to send up to 2 packets.
+  for (int i = 0; i < 3; ++i) {
+    prr.OnPacketAcked(kMaxSegmentSize);
+    bytes_in_flight -= kMaxSegmentSize;
+    // PRR-SSRB should allow two packets to be sent.
+    for (int j = 0; j < 2; ++j) {
+      EXPECT_EQ(QuicTime::Delta::Zero(),
+                prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                                  ssthresh_after_loss));
+      // Send a packet in response.
+      prr.OnPacketSent(kMaxSegmentSize);
+      bytes_in_flight += kMaxSegmentSize;
+    }
+    // PRR should allow no more than 2 packets in response to an ack.
+    EXPECT_EQ(QuicTime::Delta::Infinite(),
+              prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                                ssthresh_after_loss));
+  }
+
+  // Out of SSRB mode, PRR allows one send in response to each ack.
+  for (int i = 0; i < 10; ++i) {
+    prr.OnPacketAcked(kMaxSegmentSize);
+    bytes_in_flight -= kMaxSegmentSize;
+    EXPECT_EQ(QuicTime::Delta::Zero(),
+              prr.TimeUntilSend(congestion_window, bytes_in_flight,
+                                ssthresh_after_loss));
+    // Send a packet in response.
+    prr.OnPacketSent(kMaxSegmentSize);
+    bytes_in_flight += kMaxSegmentSize;
+  }
+}
+
+}  // namespace test
+}  // namespace net