Prepare for ICE-renomination

webrtc/p2p/base/p2ptransportchannel_unittest.cc

 /*
  *  Copyright 2009 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.
  */
 
@@ skipping 1844 matching lines @@
       const SocketAddress& address) {
     for (cricket::Connection* conn : channel->connections()) {
       if (conn->local_candidate().address().EqualIPs(address)) {
         return conn;
       }
     }
     return nullptr;
   }
 
   void DestroyAllButBestConnection(cricket::P2PTransportChannel* channel) {
-    const cricket::Connection* best_connection = channel->best_connection();
+    const cricket::Connection* selected_connection =
+        channel->selected_connection();
     for (cricket::Connection* conn : channel->connections()) {
-      if (conn != best_connection) {
+      if (conn != selected_connection) {
         conn->Destroy();
       }
     }
   }
 };
 
 // Test that we can establish connectivity when both peers are multihomed.
 TEST_F(P2PTransportChannelMultihomedTest, DISABLED_TestBasic) {
   AddAddress(0, kPublicAddrs[0]);
   AddAddress(0, kAlternateAddrs[0]);
@@ skipping 106 matching lines @@
                              3000, clock);
   EXPECT_TRUE(
     LocalCandidate(ep1_ch1())->address().EqualIPs(kAlternateAddrs[0]));
   EXPECT_TRUE(RemoteCandidate(ep1_ch1())->address().EqualIPs(kPublicAddrs[1]));
   EXPECT_TRUE(
       RemoteCandidate(ep2_ch1())->address().EqualIPs(kAlternateAddrs[0]));
 
   DestroyChannels();
 }
 
+// Test that when the controlling side switches the selected connection,
+// the nominated value of the selected connection on the controlled side will
+// increase.
+TEST_F(P2PTransportChannelMultihomedTest, TestIceRenomination) {
+  rtc::ScopedFakeClock clock;
+  // Adding alternate address will make sure |kPublicAddrs| has the higher
+  // priority than others. This is due to FakeNetwork::AddInterface method.
+  AddAddress(0, kAlternateAddrs[0]);
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  CreateChannels(1);
+  ep1_ch1()->set_peer_supports_renomination(true);
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->receiving() && ep1_ch1()->writable() &&
+                                 ep2_ch1()->receiving() &&
+                                 ep2_ch1()->writable(),
+                             3000, clock);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep2_ch1()->selected_connection()->nominated_value() > 0, kDefaultTimeout,
+      clock);
+  int nominated_value = ep2_ch1()->selected_connection()->nominated_value();
+
+  // Make the receiving timeout shorter for testing.
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
+  ep1_ch1()->SetIceConfig(config);
+  ep2_ch1()->SetIceConfig(config);
+
+  // Blackhole any traffic to or from the public addrs.
+  LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+
+  // We should detect loss of receiving within 1 second or so.
+  EXPECT_TRUE_SIMULATED_WAIT(!ep1_ch1()->selected_connection()->receiving() &&
+                                 !ep2_ch1()->selected_connection()->receiving(),
+                             3000, clock);

[Taylor Brandstetter, 2016/07/27 22:20:55]

This test relies on both channels becoming "not receiving" at the same time. But
what if in the future, the failover algorithm is changed such that there's never
a loss of "receiving"? That would break the test.

I think the test could be made more change-resilient if you blackholed *both*
addresses at the same time, waited for "!receiving", then un-blackholed
kAlternateAddrs[0].

[honghaiz3, 2016/07/28 04:19:14]

Revised. I think we need to make sure that the controlling side switched the
connection and the controlled side increased the nominated value. 

[Taylor Brandstetter, 2016/07/28 16:30:45]

This looks good.

+  // We should switch over to use the alternate addr on both sides
+  // when we are not receiving.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection()->receiving() &&
+                                 ep2_ch1()->selected_connection()->receiving(),
+                             3000, clock);
+  // The connection must have switched on the controlling side and the nominated
+  // value should increase.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep2_ch1()->selected_connection()->nominated_value() > nominated_value,
+      kDefaultTimeout, clock);
+
+  DestroyChannels();
+}
+
 // Test that if an interface fails temporarily and then recovers quickly,
 // the selected connection will not switch.
 // The case that it will switch over to the backup connection if the selected
 // connection does not recover after enough time is covered in
 // TestFailoverControlledSide and TestFailoverControllingSide.
 TEST_F(P2PTransportChannelMultihomedTest,
        TestConnectionSwitchDampeningControlledSide) {
   rtc::ScopedFakeClock clock;
   AddAddress(0, kPublicAddrs[0]);
   // Adding alternate address will make sure |kPublicAddrs| has the higher
@@ skipping 284 matching lines @@
   SetAllocatorFlags(0, kOnlyLocalPorts);
   SetAllocatorFlags(1, kOnlyLocalPorts);
   EXPECT_TRUE_WAIT_MARGIN(ep1_ch1()->receiving() && ep1_ch1()->writable() &&
                               ep2_ch1()->receiving() && ep2_ch1()->writable(),
                           kDefaultTimeout, kDefaultTimeout);
 
   // Add a new wifi interface on end point 2. We should expect a new connection
   // to be created and the new one will be the best connection.
   AddAddress(1, wifi[1], "test_wifi1", rtc::ADAPTER_TYPE_WIFI);
   const cricket::Connection* conn;
-  EXPECT_TRUE_WAIT((conn = ep1_ch1()->best_connection()) != nullptr &&
+  EXPECT_TRUE_WAIT((conn = ep1_ch1()->selected_connection()) != nullptr &&
                        conn->remote_candidate().address().EqualIPs(wifi[1]),
                    kDefaultTimeout);
-  EXPECT_TRUE_WAIT((conn = ep2_ch1()->best_connection()) != nullptr &&
+  EXPECT_TRUE_WAIT((conn = ep2_ch1()->selected_connection()) != nullptr &&
                        conn->local_candidate().address().EqualIPs(wifi[1]),
                    kDefaultTimeout);
 
   // Add a new cellular interface on end point 1, we should expect a new
   // backup connection created using this new interface.
   AddAddress(0, cellular[0], "test_cellular0", rtc::ADAPTER_TYPE_CELLULAR);
-  EXPECT_TRUE_WAIT(ep1_ch1()->GetState() == cricket::STATE_COMPLETED &&
-                       (conn = GetConnectionWithLocalAddress(
-                            ep1_ch1(), cellular[0])) != nullptr &&
-                       conn != ep1_ch1()->best_connection() && conn->writable(),
-                   kDefaultTimeout);
+  EXPECT_TRUE_WAIT(
+      ep1_ch1()->GetState() == cricket::STATE_COMPLETED &&
+          (conn = GetConnectionWithLocalAddress(ep1_ch1(), cellular[0])) !=
+              nullptr &&
+          conn != ep1_ch1()->selected_connection() && conn->writable(),
+      kDefaultTimeout);
   EXPECT_TRUE_WAIT(
       ep2_ch1()->GetState() == cricket::STATE_COMPLETED &&
           (conn = GetConnectionWithRemoteAddress(ep2_ch1(), cellular[0])) !=
               nullptr &&
-          conn != ep2_ch1()->best_connection() && conn->receiving(),
+          conn != ep2_ch1()->selected_connection() && conn->receiving(),
       kDefaultTimeout);
 
   DestroyChannels();
 }
 
 // Tests that we can switch links via continual gathering.
 TEST_F(P2PTransportChannelMultihomedTest,
        TestSwitchLinksViaContinualGathering) {
   rtc::ScopedFakeClock clock;
   AddAddress(0, kPublicAddrs[0]);
@@ skipping 25 matching lines @@
       ep1_ch1()->selected_connection() && ep2_ch1()->selected_connection() &&
           LocalCandidate(ep1_ch1())->address().EqualIPs(kPublicAddrs[0]) &&
           RemoteCandidate(ep1_ch1())->address().EqualIPs(kAlternateAddrs[1]),
       3000, clock);
 
   // Remove one address first and then add another address.
   LOG(LS_INFO) << "Draining again...";
   RemoveAddress(1, kAlternateAddrs[1]);
   AddAddress(1, kAlternateAddrs[0]);
   EXPECT_TRUE_SIMULATED_WAIT(
-      ep1_ch1()->best_connection() && ep2_ch1()->best_connection() &&
+      ep1_ch1()->selected_connection() && ep2_ch1()->selected_connection() &&
           LocalCandidate(ep1_ch1())->address().EqualIPs(kPublicAddrs[0]) &&
           RemoteCandidate(ep1_ch1())->address().EqualIPs(kAlternateAddrs[0]),
       3000, clock);
 
   DestroyChannels();
 }
 
 /*
 TODO(honghaiz) Once continual gathering fully supports
 GATHER_CONTINUALLY_AND_RECOVER, put this test back.
@@ skipping 16 matching lines @@
 
   // Create channels and let them go writable, as usual.
   CreateChannels(1);
   // Set continual gathering policy.
   IceConfig config = CreateIceConfig(1000, GATHER_CONTINUALLY_AND_RECOVER);
   ep1_ch1()->SetIceConfig(config);
   ep2_ch1()->SetIceConfig(config);
   EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->receiving() && ep1_ch1()->writable() &&
                               ep2_ch1()->receiving() && ep2_ch1()->writable(),
                           3000, clock);
-  EXPECT_TRUE(ep1_ch1()->best_connection() && ep2_ch1()->best_connection() &&
+  EXPECT_TRUE(ep1_ch1()->selected_connection() &&
+              ep2_ch1()->selected_connection() &&
               LocalCandidate(ep1_ch1())->address().EqualIPs(wifi[0]) &&
               RemoteCandidate(ep1_ch1())->address().EqualIPs(wifi[1]));
 
   // First destroy all backup connection.
   DestroyAllButBestConnection(ep1_ch1());
 
   SIMULATED_WAIT(false, 10, clock);
   // Then the interface of the best connection goes away.
   RemoveAddress(0, wifi[0]);
   EXPECT_TRUE_SIMULATED_WAIT(
-      ep1_ch1()->best_connection() && ep2_ch1()->best_connection() &&
+      ep1_ch1()->selected_connection() && ep2_ch1()->selected_connection() &&
           LocalCandidate(ep1_ch1())->address().EqualIPs(cellular[0]) &&
           RemoteCandidate(ep1_ch1())->address().EqualIPs(wifi[1]),
       3000, clock);
 
   DestroyChannels();
 }
 */
 
 // Tests that the backup connection will be restored after it is destroyed.
 TEST_F(P2PTransportChannelMultihomedTest, TestRestoreBackupConnection) {
@@ skipping 11 matching lines @@
   // Create channels and let them go writable, as usual.
   CreateChannels(1);
   IceConfig config = CreateIceConfig(1000, GATHER_CONTINUALLY);
   config.regather_on_failed_networks_interval = rtc::Optional<int>(2000);
   ep1_ch1()->SetIceConfig(config);
   ep2_ch1()->SetIceConfig(config);
   EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->receiving() && ep1_ch1()->writable() &&
                                  ep2_ch1()->receiving() &&
                                  ep2_ch1()->writable(),
                              3000, clock);
-  EXPECT_TRUE(ep1_ch1()->best_connection() && ep2_ch1()->best_connection() &&
+  EXPECT_TRUE(ep1_ch1()->selected_connection() &&
+              ep2_ch1()->selected_connection() &&
               LocalCandidate(ep1_ch1())->address().EqualIPs(wifi[0]) &&
               RemoteCandidate(ep1_ch1())->address().EqualIPs(wifi[1]));
 
   // Destroy all backup connections.
   DestroyAllButBestConnection(ep1_ch1());
   // Ensure the backup connection is removed first.
   EXPECT_TRUE_SIMULATED_WAIT(
       GetConnectionWithLocalAddress(ep1_ch1(), cellular[0]) == nullptr,
       kDefaultTimeout, clock);
   const cricket::Connection* conn;
   EXPECT_TRUE_SIMULATED_WAIT(
       (conn = GetConnectionWithLocalAddress(ep1_ch1(), cellular[0])) !=
               nullptr &&
-          conn != ep1_ch1()->best_connection() && conn->writable(),
+          conn != ep1_ch1()->selected_connection() && conn->writable(),
       5000, clock);
 
   DestroyChannels();
 }
 
 // A collection of tests which tests a single P2PTransportChannel by sending
 // pings.
 class P2PTransportChannelPingTest : public testing::Test,
                                     public sigslot::has_slots<> {
  public:
@@ skipping 62 matching lines @@
                                             int port,
                                             int priority,
                                             bool writable) {
     channel.AddRemoteCandidate(
         CreateUdpCandidate(LOCAL_PORT_TYPE, ip_addr, port, priority));
     EXPECT_TRUE_SIMULATED_WAIT(
         GetConnectionTo(&channel, ip_addr, port) != nullptr, 3000, clock);
     Connection* conn = GetConnectionTo(&channel, ip_addr, port);
 
     if (conn && writable) {
-      conn->ReceivedPingResponse(LOW_RTT);  // make it writable
+      conn->ReceivedPingResponse(LOW_RTT, "id");  // make it writable
     }
     return conn;
   }
 
-  void NominateConnection(Connection* conn) {
-    conn->set_nominated(true);
+  void NominateConnection(Connection* conn, int nominated_value = 1) {
+    conn->set_nominated_value(nominated_value);
     conn->SignalNominated(conn);
   }
 
   void OnSelectedCandidatePairChanged(
       TransportChannel* transport_channel,
       CandidatePairInterface* selected_candidate_pair,
       int last_sent_packet_id,
       bool ready_to_send) {
     last_selected_candidate_pair_ = selected_candidate_pair;
     last_sent_packet_id_ = last_sent_packet_id;
@@ skipping 80 matching lines @@
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
 
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn1 != nullptr);
   ASSERT_TRUE(conn2 != nullptr);
 
   // Low-priority connection becomes writable so that the other connection
   // is not pruned.
-  conn1->ReceivedPingResponse(LOW_RTT);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_TRUE_WAIT(
       conn1->num_pings_sent() >= MIN_PINGS_AT_WEAK_PING_INTERVAL &&
           conn2->num_pings_sent() >= MIN_PINGS_AT_WEAK_PING_INTERVAL,
       kDefaultTimeout);
 }
 
 // Verify that the connections are pinged at the right time.
 TEST_F(P2PTransportChannelPingTest, TestStunPingIntervals) {
   rtc::ScopedFakeClock clock;
   int RTT_RATIO = 4;
@@ skipping 15 matching lines @@
   int64_t start = clock.TimeNanos();
   SIMULATED_WAIT(conn->num_pings_sent() >= MIN_PINGS_AT_WEAK_PING_INTERVAL,
                  kDefaultTimeout, clock);
   int64_t ping_interval_ms = (clock.TimeNanos() - start) /
                              rtc::kNumNanosecsPerMillisec /
                              (MIN_PINGS_AT_WEAK_PING_INTERVAL - 1);
   EXPECT_EQ(ping_interval_ms, WEAK_PING_INTERVAL);
 
   // Stabilizing.
 
-  conn->ReceivedPingResponse(LOW_RTT);
+  conn->ReceivedPingResponse(LOW_RTT, "id");
   int ping_sent_before = conn->num_pings_sent();
   start = clock.TimeNanos();
   // The connection becomes strong but not stable because we haven't been able
   // to converge the RTT.
   SIMULATED_WAIT(conn->num_pings_sent() == ping_sent_before + 1, 3000, clock);
   ping_interval_ms = (clock.TimeNanos() - start) / rtc::kNumNanosecsPerMillisec;
   EXPECT_GE(ping_interval_ms, STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL);
   EXPECT_LE(ping_interval_ms,
             STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL + SCHEDULING_RANGE);
 
   // Stabilized.
 
   // The connection becomes stable after receiving more than RTT_RATIO rtt
   // samples.
   for (int i = 0; i < RTT_RATIO; i++) {
-    conn->ReceivedPingResponse(LOW_RTT);
+    conn->ReceivedPingResponse(LOW_RTT, "id");
   }
   ping_sent_before = conn->num_pings_sent();
   start = clock.TimeNanos();
   SIMULATED_WAIT(conn->num_pings_sent() == ping_sent_before + 1, 3000, clock);
   ping_interval_ms = (clock.TimeNanos() - start) / rtc::kNumNanosecsPerMillisec;
   EXPECT_GE(ping_interval_ms, STABLE_WRITABLE_CONNECTION_PING_INTERVAL);
   EXPECT_LE(ping_interval_ms,
             STABLE_WRITABLE_CONNECTION_PING_INTERVAL + SCHEDULING_RANGE);
 
   // Destabilized.
 
-  conn->ReceivedPingResponse(LOW_RTT);
+  conn->ReceivedPingResponse(LOW_RTT, "id");
   // Create a in-flight ping.
   conn->Ping(clock.TimeNanos() / rtc::kNumNanosecsPerMillisec);
   start = clock.TimeNanos();
   // In-flight ping timeout and the connection will be unstable.
   SIMULATED_WAIT(
       !conn->stable(clock.TimeNanos() / rtc::kNumNanosecsPerMillisec), 3000,
       clock);
   int64_t duration_ms =
       (clock.TimeNanos() - start) / rtc::kNumNanosecsPerMillisec;
   EXPECT_GE(duration_ms, 2 * conn->rtt() - RTT_RANGE);
@@ skipping 61 matching lines @@
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
 
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn1 != nullptr);
   ASSERT_TRUE(conn2 != nullptr);
 
   EXPECT_EQ(conn2, FindNextPingableConnectionAndPingIt(&ch));
   EXPECT_EQ(conn1, FindNextPingableConnectionAndPingIt(&ch));
-  conn1->ReceivedPingResponse(LOW_RTT);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
   ASSERT_TRUE(conn1->writable());
   conn1->ReceivedPing();
 
   // Ping received, but the connection is already writable, so no
   // "triggered check" and conn2 is pinged before conn1 because it has
   // a higher priority.
   EXPECT_EQ(conn2, FindNextPingableConnectionAndPingIt(&ch));
 }
 
 TEST_F(P2PTransportChannelPingTest, TestFailedConnectionNotPingable) {
@@ skipping 96 matching lines @@
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   ASSERT_TRUE(conn1 != nullptr);
   uint32_t remote_priority = conn1->remote_candidate().priority();
 
   // Create a higher priority candidate and make the connection
   // receiving/writable. This will prune conn1.
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn2 != nullptr);
   conn2->ReceivedPing();
-  conn2->ReceivedPingResponse(LOW_RTT);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
 
   // Wait for conn1 to be pruned.
   EXPECT_TRUE_WAIT(conn1->pruned(), 3000);
   // Destroy the connection to test SignalUnknownAddress.
   conn1->Destroy();
   EXPECT_TRUE_WAIT(GetConnectionTo(&ch, "1.1.1.1", 1) == nullptr, 1000);
 
   // Create a minimal STUN message with prflx priority.
   IceMessage request;
   request.SetType(STUN_BINDING_REQUEST);
@@ skipping 80 matching lines @@
 
   // If a stun request with use-candidate attribute arrives, the receiving
   // connection will be set as the selected connection, even though
   // its priority is lower.
   EXPECT_EQ(-1, SendData(ch, data, len, ++last_packet_id));
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "3.3.3.3", 3, 1));
   Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3);
   ASSERT_TRUE(conn3 != nullptr);
   // Because it has a lower priority, the selected connection is still conn2.
   EXPECT_EQ(conn2, ch.selected_connection());
-  conn3->ReceivedPingResponse(LOW_RTT);  // Become writable.
+  conn3->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
   // But if it is nominated via use_candidate, it is chosen as the selected
   // connection.
-  conn3->set_nominated(true);
-  conn3->SignalNominated(conn3);
+  NominateConnection(conn3);
   EXPECT_EQ(conn3, ch.selected_connection());
   EXPECT_EQ(conn3, last_selected_candidate_pair());
   EXPECT_EQ(-1, last_sent_packet_id());
   EXPECT_TRUE(channel_ready_to_send());
 
   // Even if another higher priority candidate arrives, it will not be set as
   // the selected connection because the selected connection is nominated by
   // the controlling side.
   EXPECT_EQ(len, SendData(ch, data, len, ++last_packet_id));
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "4.4.4.4", 4, 100));
   Connection* conn4 = WaitForConnectionTo(&ch, "4.4.4.4", 4);
   ASSERT_TRUE(conn4 != nullptr);
   EXPECT_EQ(conn3, ch.selected_connection());
   // But if it is nominated via use_candidate and writable, it will be set as
   // the selected connection.
-  conn4->set_nominated(true);
-  conn4->SignalNominated(conn4);
+  NominateConnection(conn4);
   // Not switched yet because conn4 is not writable.
   EXPECT_EQ(conn3, ch.selected_connection());
   reset_channel_ready_to_send();
   // The selected connection switches after conn4 becomes writable.
-  conn4->ReceivedPingResponse(LOW_RTT);
+  conn4->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_EQ_WAIT(conn4, ch.selected_connection(), kDefaultTimeout);
   EXPECT_EQ(conn4, last_selected_candidate_pair());
   EXPECT_EQ(last_packet_id, last_sent_packet_id());
   // SignalReadyToSend is fired again because conn4 is writable.
   EXPECT_TRUE(channel_ready_to_send());
 }
 
 // The controlled side will select a connection as the "selected connection"
 // based on requests from an unknown address before the controlling side
 // nominates a connection, and will nominate a connection from an unknown
@@ skipping 14 matching lines @@
   uint32_t prflx_priority = ICE_TYPE_PREFERENCE_PRFLX << 24;
   request.AddAttribute(
       new StunUInt32Attribute(STUN_ATTR_PRIORITY, prflx_priority));
   TestUDPPort* port = static_cast<TestUDPPort*>(GetPort(&ch));
   port->SignalUnknownAddress(port, rtc::SocketAddress("1.1.1.1", 1), PROTO_UDP,
                              &request, kIceUfrag[1], false);
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   ASSERT_TRUE(conn1 != nullptr);
   EXPECT_TRUE(port->sent_binding_response());
   EXPECT_EQ(conn1, ch.selected_connection());
-  conn1->ReceivedPingResponse(LOW_RTT);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_EQ(conn1, ch.selected_connection());
   port->set_sent_binding_response(false);
 
   // Another connection is nominated via use_candidate.
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn2 != nullptr);
   // Because it has a lower priority, the selected connection is still conn1.
   EXPECT_EQ(conn1, ch.selected_connection());
   // When it is nominated via use_candidate and writable, it is chosen as the
   // selected connection.
-  conn2->ReceivedPingResponse(LOW_RTT);  // Become writable.
-  conn2->set_nominated(true);
-  conn2->SignalNominated(conn2);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
+  NominateConnection(conn2);
   EXPECT_EQ(conn2, ch.selected_connection());
 
   // Another request with unknown address, it will not be set as the selected
   // connection because the selected connection was nominated by the controlling
   // side.
   port->SignalUnknownAddress(port, rtc::SocketAddress("3.3.3.3", 3), PROTO_UDP,
                              &request, kIceUfrag[1], false);
   Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3);
   ASSERT_TRUE(conn3 != nullptr);
   EXPECT_TRUE(port->sent_binding_response());
-  conn3->ReceivedPingResponse(LOW_RTT);  // Become writable.
+  conn3->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
   EXPECT_EQ(conn2, ch.selected_connection());
   port->set_sent_binding_response(false);
 
   // However if the request contains use_candidate attribute, it will be
   // selected as the selected connection.
   request.AddAttribute(new StunByteStringAttribute(STUN_ATTR_USE_CANDIDATE));
   port->SignalUnknownAddress(port, rtc::SocketAddress("4.4.4.4", 4), PROTO_UDP,
                              &request, kIceUfrag[1], false);
   Connection* conn4 = WaitForConnectionTo(&ch, "4.4.4.4", 4);
   ASSERT_TRUE(conn4 != nullptr);
   EXPECT_TRUE(port->sent_binding_response());
   // conn4 is not the selected connection yet because it is not writable.
   EXPECT_EQ(conn2, ch.selected_connection());
-  conn4->ReceivedPingResponse(LOW_RTT);  // Become writable.
+  conn4->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
   EXPECT_EQ_WAIT(conn4, ch.selected_connection(), kDefaultTimeout);
 
   // Test that the request from an unknown address contains a ufrag from an old
   // generation.
   port->set_sent_binding_response(false);
   ch.SetRemoteIceCredentials(kIceUfrag[2], kIcePwd[2]);
   ch.SetRemoteIceCredentials(kIceUfrag[3], kIcePwd[3]);
   port->SignalUnknownAddress(port, rtc::SocketAddress("5.5.5.5", 5), PROTO_UDP,
                              &request, kIceUfrag[2], false);
   Connection* conn5 = WaitForConnectionTo(&ch, "5.5.5.5", 5);
@@ skipping 19 matching lines @@
 
   // If a data packet is received on conn2, the selected connection should
   // switch to conn2 because the controlled side must mirror the media path
   // chosen by the controlling side.
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn2 != nullptr);
   conn2->ReceivedPing();  // Start receiving.
   conn2->OnReadPacket("ABC", 3, rtc::CreatePacketTime(0));
   EXPECT_EQ(conn2, ch.selected_connection());
-  conn2->ReceivedPingResponse(LOW_RTT);  // Become writable.
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
 
   // Now another STUN message with an unknown address and use_candidate will
   // nominate the selected connection.
   IceMessage request;
   request.SetType(STUN_BINDING_REQUEST);
   request.AddAttribute(
       new StunByteStringAttribute(STUN_ATTR_USERNAME, kIceUfrag[1]));
   uint32_t prflx_priority = ICE_TYPE_PREFERENCE_PRFLX << 24;
   request.AddAttribute(
       new StunUInt32Attribute(STUN_ATTR_PRIORITY, prflx_priority));
   request.AddAttribute(new StunByteStringAttribute(STUN_ATTR_USE_CANDIDATE));
   Port* port = GetPort(&ch);
   port->SignalUnknownAddress(port, rtc::SocketAddress("3.3.3.3", 3), PROTO_UDP,
                              &request, kIceUfrag[1], false);
   Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3);
   ASSERT_TRUE(conn3 != nullptr);
   EXPECT_EQ(conn2, ch.selected_connection());  // Not writable yet.
-  conn3->ReceivedPingResponse(LOW_RTT);    // Become writable.
+  conn3->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
   EXPECT_EQ_WAIT(conn3, ch.selected_connection(), kDefaultTimeout);
 
   // Now another data packet will not switch the selected connection because the
   // selected connection was nominated by the controlling side.
   conn2->ReceivedPing();
-  conn2->ReceivedPingResponse(LOW_RTT);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
   conn2->OnReadPacket("XYZ", 3, rtc::CreatePacketTime(0));
   EXPECT_EQ_WAIT(conn3, ch.selected_connection(), kDefaultTimeout);
 }
 
 TEST_F(P2PTransportChannelPingTest,
        TestControlledAgentDataReceivingTakesHigherPrecedenceThanPriority) {
   rtc::ScopedFakeClock clock;
 
   FakePortAllocator pa(rtc::Thread::Current(), nullptr);
   P2PTransportChannel ch("SwitchSelectedConnection", 1, &pa);
@@ skipping 69 matching lines @@
   conn2->OnReadPacket("XYZ", 3, rtc::CreatePacketTime(0));
   EXPECT_EQ(1, reset_selected_candidate_pair_switches());
   EXPECT_EQ(conn2, last_selected_candidate_pair());
 
   // Make sure sorting won't reselect candidate pair.
   SIMULATED_WAIT(false, 10, clock);
   EXPECT_EQ(0, reset_selected_candidate_pair_switches());
 }
 
 TEST_F(P2PTransportChannelPingTest,
+       TestControlledAgentSelectsConnectionWithHigherNominatedValue) {
+  rtc::ScopedFakeClock clock;
+
+  FakePortAllocator pa(rtc::Thread::Current(), nullptr);
+  P2PTransportChannel ch("SwitchSelectedConnection", 1, &pa);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  // The connections have decreasing priority.
+  Connection* conn1 =
+      CreateConnectionWithCandidate(ch, clock, "1.1.1.1", 1, 10, false);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 =
+      CreateConnectionWithCandidate(ch, clock, "2.2.2.2", 2, 9, false);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // conn1 is the selected connection because it has a higher priority,
+  EXPECT_EQ_SIMULATED_WAIT(conn1, last_selected_candidate_pair(),
+                           kDefaultTimeout, clock);
+  reset_selected_candidate_pair_switches();
+
+  // conn2 is nominated; it becomes selected.
+  NominateConnection(conn2);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_EQ(conn2, last_selected_candidate_pair());
+
+  // conn1 is selected because of its priority.
+  NominateConnection(conn1);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_EQ(conn1, last_selected_candidate_pair());
+
+  // conn2 gets higher nominated value; it is selected again.
+  NominateConnection(conn2, 2);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_EQ(conn2, last_selected_candidate_pair());
+
+  // Make sure sorting won't reselect candidate pair.
+  SIMULATED_WAIT(false, 100, clock);
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+}
+
+TEST_F(P2PTransportChannelPingTest,
        TestControlledAgentWriteStateTakesHigherPrecedenceThanNomination) {
   rtc::ScopedFakeClock clock;
 
   FakePortAllocator pa(rtc::Thread::Current(), nullptr);
   P2PTransportChannel ch("SwitchSelectedConnection", 1, &pa);
   PrepareChannel(&ch);
   ch.SetIceRole(ICEROLE_CONTROLLED);
   ch.MaybeStartGathering();
   // The connections have decreasing priority.
   Connection* conn1 =
       CreateConnectionWithCandidate(ch, clock, "1.1.1.1", 1, 10, false);
   ASSERT_TRUE(conn1 != nullptr);
   Connection* conn2 =
       CreateConnectionWithCandidate(ch, clock, "2.2.2.2", 2, 9, false);
   ASSERT_TRUE(conn2 != nullptr);
 
   NominateConnection(conn1);
   EXPECT_EQ(1, reset_selected_candidate_pair_switches());
 
   // conn2 becomes writable; it is selected even though it is not nominated.
-  conn2->ReceivedPingResponse(LOW_RTT);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
 
   EXPECT_EQ_SIMULATED_WAIT(1, reset_selected_candidate_pair_switches(),
                            kDefaultTimeout, clock);
   EXPECT_EQ_SIMULATED_WAIT(conn2, last_selected_candidate_pair(),
                            kDefaultTimeout, clock);
 
   // If conn1 is also writable, it will become selected.
-  conn1->ReceivedPingResponse(LOW_RTT);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_EQ_SIMULATED_WAIT(1, reset_selected_candidate_pair_switches(),
                            kDefaultTimeout, clock);
   EXPECT_EQ_SIMULATED_WAIT(conn1, last_selected_candidate_pair(),
                            kDefaultTimeout, clock);
 
   // Make sure sorting won't reselect candidate pair.
   SIMULATED_WAIT(false, 10, clock);
   EXPECT_EQ(0, reset_selected_candidate_pair_switches());
 }
 
@@ skipping 40 matching lines @@
 TEST_F(P2PTransportChannelPingTest, TestDontPruneWhenWeak) {
   FakePortAllocator pa(rtc::Thread::Current(), nullptr);
   P2PTransportChannel ch("test channel", 1, &pa);
   PrepareChannel(&ch);
   ch.SetIceRole(ICEROLE_CONTROLLED);
   ch.MaybeStartGathering();
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   ASSERT_TRUE(conn1 != nullptr);
   EXPECT_EQ(conn1, ch.selected_connection());
-  conn1->ReceivedPingResponse(LOW_RTT);  // Becomes writable and receiving
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
 
   // When a higher-priority, nominated candidate comes in, the connections with
   // lower-priority are pruned.
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 10));
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn2 != nullptr);
-  conn2->ReceivedPingResponse(LOW_RTT);  // Becomes writable and receiving
-  conn2->set_nominated(true);
-  conn2->SignalNominated(conn2);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  NominateConnection(conn2);
   EXPECT_TRUE_WAIT(conn1->pruned(), 3000);
 
   ch.SetIceConfig(CreateIceConfig(500, GATHER_ONCE));
   // Wait until conn2 becomes not receiving.
   EXPECT_TRUE_WAIT(!conn2->receiving(), 3000);
 
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "3.3.3.3", 3, 1));
   Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3);
   ASSERT_TRUE(conn3 != nullptr);
   // The selected connection should still be conn2. Even through conn3 has lower
@@ skipping 34 matching lines @@
   EXPECT_EQ(TransportChannelState::STATE_INIT, ch.GetState());
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn1 != nullptr);
   ASSERT_TRUE(conn2 != nullptr);
   // Now there are two connections, so the transport channel is connecting.
   EXPECT_EQ(TransportChannelState::STATE_CONNECTING, ch.GetState());
   // |conn1| becomes writable and receiving; it then should prune |conn2|.
-  conn1->ReceivedPingResponse(LOW_RTT);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_TRUE_WAIT(conn2->pruned(), 1000);
   EXPECT_EQ(TransportChannelState::STATE_COMPLETED, ch.GetState());
   conn1->Prune();  // All connections are pruned.
   // Need to wait until the channel state is updated.
   EXPECT_EQ_WAIT(TransportChannelState::STATE_FAILED, ch.GetState(), 1000);
 }
 
 // Test that when a low-priority connection is pruned, it is not deleted
 // right away, and it can become active and be pruned again.
 TEST_F(P2PTransportChannelPingTest, TestConnectionPrunedAgain) {
   FakePortAllocator pa(rtc::Thread::Current(), nullptr);
   P2PTransportChannel ch("test channel", 1, &pa);
   PrepareChannel(&ch);
   IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
   config.receiving_switching_delay = rtc::Optional<int>(800);
   ch.SetIceConfig(config);
   ch.MaybeStartGathering();
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   ASSERT_TRUE(conn1 != nullptr);
   EXPECT_EQ(conn1, ch.selected_connection());
-  conn1->ReceivedPingResponse(LOW_RTT);  // Becomes writable and receiving
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
 
   // Add a low-priority connection |conn2|, which will be pruned, but it will
   // not be deleted right away. Once the current selected connection becomes not
   // receiving, |conn2| will start to ping and upon receiving the ping response,
   // it will become the selected connection.
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn2 != nullptr);
   EXPECT_TRUE_WAIT(!conn2->active(), 1000);
   // |conn2| should not send a ping yet.
   EXPECT_EQ(Connection::STATE_WAITING, conn2->state());
   EXPECT_EQ(TransportChannelState::STATE_COMPLETED, ch.GetState());
   // Wait for |conn1| becoming not receiving.
   EXPECT_TRUE_WAIT(!conn1->receiving(), 3000);
   // Make sure conn2 is not deleted.
   conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn2 != nullptr);
   EXPECT_EQ_WAIT(Connection::STATE_INPROGRESS, conn2->state(), 1000);
-  conn2->ReceivedPingResponse(LOW_RTT);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_EQ_WAIT(conn2, ch.selected_connection(), 1000);
   EXPECT_EQ(TransportChannelState::STATE_CONNECTING, ch.GetState());
 
   // When |conn1| comes back again, |conn2| will be pruned again.
-  conn1->ReceivedPingResponse(LOW_RTT);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_EQ_WAIT(conn1, ch.selected_connection(), 1000);
   EXPECT_TRUE_WAIT(!conn2->active(), 1000);
   EXPECT_EQ(TransportChannelState::STATE_COMPLETED, ch.GetState());
 }
 
 // Test that if all connections in a channel has timed out on writing, they
 // will all be deleted. We use Prune to simulate write_time_out.
 TEST_F(P2PTransportChannelPingTest, TestDeleteConnectionsIfAllWriteTimedout) {
   FakePortAllocator pa(rtc::Thread::Current(), nullptr);
   P2PTransportChannel ch("test channel", 1, &pa);
@@ skipping 28 matching lines @@
 // the current port allocator session.
 TEST_F(P2PTransportChannelPingTest, TestStopPortAllocatorSessions) {
   FakePortAllocator pa(rtc::Thread::Current(), nullptr);
   P2PTransportChannel ch("test channel", 1, &pa);
   PrepareChannel(&ch);
   ch.SetIceConfig(CreateIceConfig(2000, GATHER_ONCE));
   ch.MaybeStartGathering();
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
   Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   ASSERT_TRUE(conn1 != nullptr);
-  conn1->ReceivedPingResponse(LOW_RTT);  // Becomes writable and receiving
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
   EXPECT_TRUE(!ch.allocator_session()->IsGettingPorts());
 
   // Start a new session. Even though conn1, which belongs to an older
   // session, becomes unwritable and writable again, it should not stop the
   // current session.
   ch.SetIceCredentials(kIceUfrag[1], kIcePwd[1]);
   ch.MaybeStartGathering();
   conn1->Prune();
-  conn1->ReceivedPingResponse(LOW_RTT);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
   EXPECT_TRUE(ch.allocator_session()->IsGettingPorts());
 
   // But if a new connection created from the new session becomes writable,
   // it will stop the current session.
   ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 100));
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   ASSERT_TRUE(conn2 != nullptr);
-  conn2->ReceivedPingResponse(LOW_RTT);  // Becomes writable and receiving
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
   EXPECT_TRUE(!ch.allocator_session()->IsGettingPorts());
 }
 
 // Test that the ICE role is updated even on ports that has been removed.
 // These ports may still have connections that need a correct role, in case that
 // the connections on it may still receive stun pings.
 TEST_F(P2PTransportChannelPingTest, TestIceRoleUpdatedOnRemovedPort) {
   FakePortAllocator pa(rtc::Thread::Current(), nullptr);
   P2PTransportChannel ch("test channel", ICE_CANDIDATE_COMPONENT_DEFAULT, &pa);
   // Starts with ICEROLE_CONTROLLING.
@@ skipping 145 matching lines @@
   Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
   EXPECT_EQ(conn2->local_candidate().type(), LOCAL_PORT_TYPE);
   EXPECT_EQ(conn2->remote_candidate().type(), LOCAL_PORT_TYPE);
   conn2->ReceivedPing();
   EXPECT_EQ(conn2, FindNextPingableConnectionAndPingIt(&ch));
 
   // Make conn3 the selected connection.
   Connection* conn3 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
   EXPECT_EQ(conn3->local_candidate().type(), LOCAL_PORT_TYPE);
   EXPECT_EQ(conn3->remote_candidate().type(), RELAY_PORT_TYPE);
-  conn3->ReceivedPingResponse(LOW_RTT);
+  conn3->ReceivedPingResponse(LOW_RTT, "id");
   ASSERT_TRUE(conn3->writable());
   conn3->ReceivedPing();
 
   /*
 
   TODO(honghaiz): Re-enable this once we use fake clock for this test to fix
   the flakiness. The following test becomes flaky because we now ping the
   connections with fast rates until every connection is pinged at least three
   times. The selected connection may have been pinged before
   |max_strong_interval|, so it may not be the next connection to be pinged as
   expected in the test.
 
   // Verify that conn3 will be the "selected connection" since it is readable
   // and writable. After |MAX_CURRENT_STRONG_INTERVAL|, it should be the next
   // pingable connection.
   EXPECT_TRUE_WAIT(conn3 == ch.selected_connection(), 5000);
   WAIT(false, max_strong_interval + 100);
-  conn3->ReceivedPingResponse(LOW_RTT);
+  conn3->ReceivedPingResponse(LOW_RTT, "id");
   ASSERT_TRUE(conn3->writable());
   EXPECT_EQ(conn3, FindNextPingableConnectionAndPingIt(&ch));
 
   */
 }
 
 // Test that Relay/Relay connections will be pinged first when everything has
 // been pinged even if the Relay/Relay connection wasn't the first to be pinged
 // in the first round.
 TEST_F(P2PTransportChannelMostLikelyToWorkFirstTest,
@@ skipping 83 matching lines @@
 
   // TCP Relay/Relay is the next.
   VerifyNextPingableConnection(RELAY_PORT_TYPE, RELAY_PORT_TYPE,
                                TCP_PROTOCOL_NAME);
 
   // Finally, Local/Relay will be pinged.
   VerifyNextPingableConnection(LOCAL_PORT_TYPE, RELAY_PORT_TYPE);
 }
 
 }  // namespace cricket {