Measure packet loss so we can use it to select ICE candidate pairs.

webrtc/p2p/base/packetlossestimator_unittest.cc

+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <utility>
+
+#include "webrtc/base/gunit.h"
+#include "webrtc/p2p/base/packetlossestimator.h"
+
+using cricket::PacketLossEstimator;
+
+class PacketLossEstimatorTest : public testing::Test {};
+
+TEST_F(PacketLossEstimatorTest, InitialResponseRate) {
+  PacketLossEstimator ple(5, 100);
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, InitialUpdateResponseRate) {
+  PacketLossEstimator ple(5, 100);
+  ple.UpdateResponseRate(10);
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseReceived) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.ReceivedResponse("a", 1);
+  ple.UpdateResponseRate(2);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseNotConsideredLostYet) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.UpdateResponseRate(2);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseConsideredLost) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.UpdateResponseRate(10);
+
+  EXPECT_EQ(0.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseLate) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.ReceivedResponse("a", 6);
+  ple.UpdateResponseRate(10);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseForgotten) {
+  PacketLossEstimator ple(5, 100);
+  ple.ExpectResponse("a", 0);
+  ple.UpdateResponseRate(101);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, Lost1_Received1) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.ExpectResponse("b", 2);
+  ple.ReceivedResponse("b", 6);
+  ple.UpdateResponseRate(7);
+
+  EXPECT_EQ(0.5, ple.get_response_rate());
+}
+
+static const std::pair<std::string, int64_t> kFivePackets[5] = {{"a", 0},
+                                                                {"b", 2},
+                                                                {"c", 4},
+                                                                {"d", 6},
+                                                                {"e", 8}};
+
+// Time: 0 1 2 3 4 5 6 7 8 9 10
+// Sent: a   b   c   d   e   |
+// Recv:       b             |
+// Wind: -------------->     |
+TEST_F(PacketLossEstimatorTest, Lost3_Received1_Waiting1) {
+  PacketLossEstimator ple(3, 100);
+
+  for (const auto& p : kFivePackets) {
+    ple.ExpectResponse(p.first, p.second);
+  }
+  ple.ReceivedResponse("b", 3);
+  ple.UpdateResponseRate(10);
+  EXPECT_EQ(0.25, ple.get_response_rate());
+}
+
+// Time: 0 1 2 3 4 5 6 7 8 9 10
+// Sent: a   b   c   d   e   |
+// Recv:                   e |
+// Wind: -------------->     |
+TEST_F(PacketLossEstimatorTest, Lost4_Early1) {
+  PacketLossEstimator ple(3, 100);
+
+  for (const auto& p : kFivePackets) {
+    ple.ExpectResponse(p.first, p.second);
+  }
+  ple.ReceivedResponse("e", 9);
+  ple.UpdateResponseRate(10);
+  // e should be considered, even though its response was received less than
+  // |consider_lost_after_ms| ago.
+  EXPECT_EQ(0.2, ple.get_response_rate());
+}
+
+// Time: 0 1 2 3 4 5 6 7 8 9 10
+// Sent: a   b   c   d   e   |
+// Recv:           c         |
+// Wind:       <------->     |
+TEST_F(PacketLossEstimatorTest, Forgot2_Received1_Lost1_Waiting1) {
+  PacketLossEstimator ple(3, 7);
+
+  for (const auto& p : kFivePackets) {
+    ple.ExpectResponse(p.first, p.second);
+  }
+  ple.ReceivedResponse("c", 5);
+  ple.UpdateResponseRate(10);
+  EXPECT_EQ(0.5, ple.get_response_rate());
+}
+
+// Tests that old messages are forgotten if ExpectResponse is called
+// |forget_after_ms| after |last_forgot_at|. It is important that ExpectResponse
+// and ReceivedResponse forget old messages to avoid |tracked_packets_| growing
+// without bound if UpdateResponseRate is never called (or rarely called).
+//
+// Time: 0 1 2 3 4 5 6
+// Sent: a           b
+// Wind:   <------->
+TEST_F(PacketLossEstimatorTest, ExpectResponseForgetsOldPackets) {
+  PacketLossEstimator ple(1, 5);
+  ple.ExpectResponse("a", 0);  // This message will be forgotten.
+  ple.ExpectResponse("b", 6);  // This call should trigger clean up.
+  // a should be forgotten, b should be tracked.
+  EXPECT_EQ(1u, ple.tracked_packet_count_for_testing());
+}
+
+// Tests that old messages are forgotten if ExpectResponse is called
+// |forget_after_ms| after |last_forgot_at|. It is important that ExpectResponse
+// and ReceivedResponse forget old messages to avoid |tracked_packets_| growing
+// without bound if UpdateResponseRate is never called (or rarely called).
+//
+// Time: 0 1 2 3 4 5 6
+// Sent: a
+// Recv:             b
+// Wind:   <------->
+TEST_F(PacketLossEstimatorTest, ReceivedResponseForgetsOldPackets) {
+  PacketLossEstimator ple(1, 5);
+  ple.ExpectResponse("a", 0);    // This message will be forgotten.
+  ple.ReceivedResponse("b", 6);  // This call should trigger clean up.
+  // a should be forgoten, b should not be tracked (received but not sent).
+  EXPECT_EQ(0u, ple.tracked_packet_count_for_testing());
+}