Reduces flakiness of EndToEndTest.ConnectionMigrationClientPortChanged.

net/tools/quic/end_to_end_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 <stddef.h>
 #include <sys/epoll.h>
 
 #include <list>
 #include <memory>
 #include <string>
@@ skipping 1456 matching lines @@
   // Tests that the client's port can change during an established QUIC
   // connection, and that doing so does not result in the connection being
   // closed by the server.
   ASSERT_TRUE(Initialize());
 
   EXPECT_EQ(kFooResponseBody, client_->SendSynchronousRequest("/foo"));
   EXPECT_EQ(200u, client_->response_headers()->parsed_response_code());
 
   // Store the client address which was used to send the first request.
   IPEndPoint old_address = client_->client()->GetLatestClientAddress();
-
-  // Stop listening and close the old FD.
-  QuicClientPeer::CleanUpUDPSocket(client_->client(),
-                                   client_->client()->GetLatestFD());
+  int old_fd = client_->client()->GetLatestFD();
 
   // Create a new socket before closing the old one, which will result in a new
   // ephemeral port.
   QuicClientPeer::CreateUDPSocketAndBind(client_->client());
 
+  // Stop listening and close the old FD.
+  QuicClientPeer::CleanUpUDPSocket(client_->client(), old_fd);
+
   // The packet writer needs to be updated to use the new FD.
   client_->client()->CreateQuicPacketWriter();
 
   // Change the internal state of the client and connection to use the new port,
   // this is done because in a real NAT rebinding the client wouldn't see any
   // port change, and so expects no change to incoming port.
   // This is kind of ugly, but needed as we are simply swapping out the client
   // FD rather than any more complex NAT rebinding simulation.
   int new_port = client_->client()->GetLatestClientAddress().port();
   QuicClientPeer::SetClientPort(client_->client(), new_port);
@@ skipping 1191 matching lines @@
   client_->WaitForResponse();
   // TODO(fayang): Fix this test to work with stateless rejects.
   if (!BothSidesSupportStatelessRejects()) {
     VerifyCleanConnection(false);
   }
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace net