Add a test to ensure QUIC's TcpCubicSender always allows packets to be

net/quic/congestion_control/tcp_cubic_sender_test.cc

 // Copyright (c) 2012 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 <algorithm>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/quic/congestion_control/rtt_stats.h"
 #include "net/quic/congestion_control/tcp_cubic_sender.h"
 #include "net/quic/congestion_control/tcp_receiver.h"
 #include "net/quic/crypto/crypto_protocol.h"
 #include "net/quic/quic_utils.h"
 #include "net/quic/test_tools/mock_clock.h"
 #include "net/quic/test_tools/quic_config_peer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using std::make_pair;
 using std::min;
 
 namespace net {
 namespace test {
 
-const uint32 kDefaultWindowTCP = 10 * kDefaultTCPMSS;
+const int64 kInitialCongestionWindow = 10;
+const uint32 kDefaultWindowTCP = kInitialCongestionWindow * kDefaultTCPMSS;
 
 // TODO(ianswett): Remove 10000 once b/10075719 is fixed.
 const QuicTcpCongestionWindow kDefaultMaxCongestionWindowTCP = 10000;
 
 class TcpCubicSenderPeer : public TcpCubicSender {
  public:
   TcpCubicSenderPeer(const QuicClock* clock,
                      bool reno,
                      QuicTcpCongestionWindow max_tcp_congestion_window)
       : TcpCubicSender(
@@ skipping 257 matching lines @@
   AckNPackets(1);
   expected_send_window += kDefaultTCPMSS;
   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 
   // Now RTO and ensure slow start gets reset.
   EXPECT_TRUE(sender_->hybrid_slow_start().started());
   sender_->OnRetransmissionTimeout(true);
   EXPECT_FALSE(sender_->hybrid_slow_start().started());
 }
 
+TEST_F(TcpCubicSenderTest, NoPRRWhenLessThanOnePacketInFlight) {
+  SendAvailableSendWindow();
+  LoseNPackets(kInitialCongestionWindow - 1);
+  AckNPackets(1);
+  // PRR will allow 2 packets for every ack during recovery.
+  EXPECT_EQ(2, SendAvailableSendWindow());
+  // Simulate abandoning all packets by supplying a bytes_in_flight of 0.
+  // PRR should now allow a packet to be sent, even though prr's state
+  // variables believe it has sent enough packets.
+  EXPECT_EQ(QuicTime::Delta::Zero(),
+            sender_->TimeUntilSend(clock_.Now(), 0, HAS_RETRANSMITTABLE_DATA));
+}
+
 TEST_F(TcpCubicSenderTest, SlowStartPacketLossPRR) {
   // Test based on the first example in RFC6937.
   // Ack 10 packets in 5 acks to raise the CWND to 20, as in the example.
   const int kNumberOfAcks = 5;
   for (int i = 0; i < kNumberOfAcks; ++i) {
     // Send our full send window.
     SendAvailableSendWindow();
     AckNPackets(2);
   }
   SendAvailableSendWindow();
@@ skipping 303 matching lines @@
   }
 
   // Next ack should cause congestion window to grow by 1MSS.
   AckNPackets(2);
   expected_send_window += kDefaultTCPMSS;
   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 }
 
 }  // namespace test
 }  // namespace net