Really connect to the same server in FTP network transaction.

net/ftp/ftp_network_transaction.cc

 // Copyright (c) 2010 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 "net/ftp/ftp_network_transaction.h"
 
 #include "base/compiler_specific.h"
 #include "base/histogram.h"
 #include "base/string_util.h"
 #include "net/base/connection_type_histograms.h"
@@ skipping 1086 matching lines @@
 int FtpNetworkTransaction::ProcessResponseQUIT(
     const FtpCtrlResponse& response) {
   ctrl_socket_->Disconnect();
   return last_error_;
 }
 
 // Data Connection
 
 int FtpNetworkTransaction::DoDataConnect() {
   next_state_ = STATE_DATA_CONNECT_COMPLETE;
-  AddressList data_addresses;
-  // TODO(phajdan.jr): Use exactly same IP address as the control socket.
-  // If the DNS name resolves to several different IPs, and they are different
-  // physical servers, this will break. However, that configuration is very rare
-  // in practice.
-  data_addresses.Copy(addresses_.head());
-  data_addresses.SetPort(data_connection_port_);
-  data_socket_.reset(socket_factory_->CreateTCPClientSocket(data_addresses));
+  AddressList data_address;
+  // Connect to the same host as the control socket to prevent PASV port
+  // scanning attacks.
+  int rv = ctrl_socket_->GetPeerAddress(&data_address);
+  if (rv != OK)
+    return Stop(rv);
+  data_address.SetPort(data_connection_port_);
+  data_socket_.reset(socket_factory_->CreateTCPClientSocket(data_address));
   return data_socket_->Connect(&io_callback_, load_log_);
 }
 
 int FtpNetworkTransaction::DoDataConnectComplete(int result) {
   RecordDataConnectionError(result);
   if (retr_failed_) {
     next_state_ = STATE_CTRL_WRITE_CWD;
   } else {
     next_state_ = STATE_CTRL_WRITE_SIZE;
   }
@@ skipping 105 matching lines @@
   if (!had_error_type[type]) {
     had_error_type[type] = true;
     UMA_HISTOGRAM_ENUMERATION("Net.FtpDataConnectionErrorHappened",
         type, NUM_OF_NET_ERROR_TYPES);
   }
   UMA_HISTOGRAM_ENUMERATION("Net.FtpDataConnectionErrorCount",
       type, NUM_OF_NET_ERROR_TYPES);
 }
 
 }  // namespace net