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

net/udp/datagram_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_UDP_DATAGRAM_SOCKET_H_
 #define NET_UDP_DATAGRAM_SOCKET_H_
 
 #include "net/base/net_export.h"
 
 namespace net {
@@ skipping 16 matching lines @@
   // Close the socket.
   virtual void Close() = 0;
 
   // Copy the remote udp address into |address| and return a network error code.
   virtual int GetPeerAddress(IPEndPoint* address) const = 0;
 
   // Copy the local udp address into |address| and return a network error code.
   // (similar to getsockname)
   virtual int GetLocalAddress(IPEndPoint* address) const = 0;
 
+  // If supported by the platform, configures the socket to set the DF
+  // (Do not Fragment) bit on packets, which prevents routers from fragmenting
+  // them. Also, for IPv6, it prevents hosts from fragmenting them.
+  // Returns a return a network error code if there was a problem, but the
+  // socket will still be usable. Can not return ERR_IO_PENDING.
+  virtual int SetDoNotFragment() = 0;
+
   // Gets the NetLog for this socket.
   virtual const BoundNetLog& NetLog() const = 0;
 };
 
 }  // namespace net
 
 #endif  // NET_UDP_DATAGRAM_SOCKET_H_