Added the following experiments:
1) Testing different PTO values (2, 3 and 5) for path degradation. (cl/766276642)
2) Enabling multi-port connection creation on 1 RTO in PTO_MODE with and without migration. (cl/772554253)
3) Added the test in the `end_to_end_test` when both kMPR1 and kMPQM are passed in the client connection options.

PiperOrigin-RevId: 774884978

quiche/quic/core/http/end_to_end_test.cc

diff --git a/quiche/quic/core/http/end_to_end_test.cc b/quiche/quic/core/http/end_to_end_test.cc
index ec8d3a4..87420ca 100644
--- a/quiche/quic/core/http/end_to_end_test.cc
+++ b/quiche/quic/core/http/end_to_end_test.cc
@@ -6071,6 +6071,69 @@
   stream->Reset(QuicRstStreamErrorCode::QUIC_STREAM_NO_ERROR);
 }
 
+TEST_P(EndToEndTest, ClientMultiPortMigrationOnPathDegradingOnRTO) {
+  client_config_.SetClientConnectionOptions(QuicTagVector{kMPQC, kMPR1, kMPQM});
+  ASSERT_TRUE(Initialize());
+  if (!version_.HasIetfQuicFrames()) {
+    return;
+  }
+  client_.reset(EndToEndTest::CreateQuicClient(nullptr));
+  ASSERT_TRUE(client_->client()->WaitForHandshakeConfirmed());
+
+  QuicConnection* client_connection = GetClientConnection();
+  QuicSpdyClientStream* stream = client_->GetOrCreateStream();
+  ASSERT_TRUE(stream);
+
+  // Increase the probing frequency to speed up this test.
+  client_connection->SetMultiPortProbingInterval(
+      QuicTime::Delta::FromMilliseconds(100));
+
+  SendSynchronousFooRequestAndCheckResponse();
+
+  // If no multiport connection is established, induce the client to validate an
+  // alternative path.
+  server_writer_->set_fake_packet_loss_percentage(100);
+  EXPECT_TRUE(client_->WaitUntil(1000, [&]() {
+    return client_connection->multi_port_stats()
+               ->num_multi_port_paths_created == 1;
+  }));
+  server_writer_->set_fake_packet_loss_percentage(0);
+
+  // Verify that the probing is triggered after multiport connection is
+  // established.
+  EXPECT_TRUE(client_->WaitUntil(1000, [&]() {
+    return 1u == client_connection->GetStats().num_path_response_received;
+  }));
+
+  auto original_self_addr = client_connection->self_address();
+  // Trigger client side path degrading
+  client_connection->OnPathDegradingDetected();
+  // Verify that the client address has changed due to migration.
+  EXPECT_NE(original_self_addr, client_connection->self_address());
+
+  // Send another request to trigger connection id retirement.
+  SendSynchronousFooRequestAndCheckResponse();
+  EXPECT_EQ(1u, client_connection->GetStats().num_retire_connection_id_sent);
+
+  // Verify new alternate path is created.
+  WaitForNewConnectionIds();
+  // Send another request to make sure the server will have a chance to
+  // establish new multiport connection on RTO.
+  SendSynchronousFooRequestAndCheckResponse();
+  // Simulate another RTO and verify that the probing on RTO is triggered again.
+  server_writer_->set_fake_packet_loss_percentage(100);
+  // Verify that a new multiport connection is established on RTO.
+  EXPECT_TRUE(client_->WaitUntil(2000, [&]() {
+    return client_connection->multi_port_stats()
+               ->num_multi_port_paths_created == 2;
+  }));
+  server_writer_->set_fake_packet_loss_percentage(0);
+  auto new_alt_path = QuicConnectionPeer::GetAlternativePath(client_connection);
+  EXPECT_NE(client_connection->self_address(), new_alt_path->self_address);
+
+  stream->Reset(QuicRstStreamErrorCode::QUIC_STREAM_NO_ERROR);
+}
+
 TEST_P(EndToEndTest, SimpleServerPreferredAddressTest) {
   use_preferred_address_ = true;
   ASSERT_TRUE(Initialize());