Add a SetDoNotFragment() method to DatagramSocket, and call this for

net/socket/socket.h

 // Copyright (c) 2011 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.
 
 #ifndef NET_SOCKET_SOCKET_H_
 #define NET_SOCKET_SOCKET_H_
 
 #include <stdint.h>
 
 #include "net/base/completion_callback.h"
@@ skipping 39 matching lines @@
 
   // Set the receive buffer size (in bytes) for the socket.
   // Note: changing this value can affect the TCP window size on some platforms.
   // Returns a net error code.
   virtual int SetReceiveBufferSize(int32_t size) = 0;
 
   // Set the send buffer size (in bytes) for the socket.
   // Note: changing this value can affect the TCP window size on some platforms.
   // Returns a net error code.
   virtual int SetSendBufferSize(int32_t size) = 0;
+
+  // Configures the socket to set or clear the DF (Do not Fragment) bit on
+  // packets, which prevents routers from fragmenting them.
+  virtual int SetDoNotFragment(bool do_not_fragment) = 0;
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_SOCKET_H_