Open a new port before closing the original in QUIC's port migration

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 <string>
 #include <sys/epoll.h>
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 982 matching lines @@
   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()->client_address();
 
   // Stop listening on the old FD.
   EpollServer* eps = client_->client()->epoll_server();
   int old_fd = client_->client()->fd();
   eps->UnregisterFD(old_fd);
+  // Create a new socket before closing the old one, which will result in a new
+  // ephemeral port.
+  QuicClientPeer::CreateUDPSocket(client_->client());
   close(old_fd);
 
-  // Create a new socket, which will result in a new ephemeral port.
-  QuicClientPeer::CreateUDPSocket(client_->client());
-
   // 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()->client_address().port();
   QuicClientPeer::SetClientPort(client_->client(), new_port);
@@ skipping 47 matching lines @@
   QuicSession* session = dispatcher->session_map().begin()->second;
   EXPECT_EQ(kClientIFCW,
             session->config()->ReceivedInitialFlowControlWindowBytes());
   server_thread_->Resume();
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace tools
 }  // namespace net