Add support of IP_MULTICAST_IF in UDP sockets.

net/udp/datagram_server_socket.h

 // 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.
 
 #ifndef NET_UDP_DATAGRAM_SERVER_SOCKET_H_
 #define NET_UDP_DATAGRAM_SERVER_SOCKET_H_
 
 #include "net/base/completion_callback.h"
 #include "net/base/net_util.h"
 #include "net/udp/datagram_socket.h"
@@ skipping 51 matching lines @@
   virtual bool SetSendBufferSize(int32 size) = 0;
 
   // Allow the socket to share the local address to which the socket will
   // be bound with other processes. Should be called before Listen().
   virtual void AllowAddressReuse() = 0;
 
   // Allow sending and receiving packets to and from broadcast addresses.
   // Should be called before Listen().
   virtual void AllowBroadcast() = 0;
 
+  // Set interface to use for multicast. If |interface_index| set to 0, default
+  // interface is used. Must be called before |JoinGroup| or |LeaveGroup|.
+  virtual int SetMulticastInterface(uint32 interface_index) = 0;
+
   // Join the multicast group with address |group_address|.
   // Returns a network error code.
-  virtual int JoinGroup(const IPAddressNumber& group_address) const = 0;
+  virtual int JoinGroup(const IPAddressNumber& group_address) = 0;
 
   // Leave the multicast group with address |group_address|.
   // If the socket hasn't joined the group, it will be ignored.
   // It's optional to leave the multicast group before destroying
   // the socket. It will be done by the OS.
   // Returns a network error code.
-  virtual int LeaveGroup(const IPAddressNumber& group_address) const = 0;
+  virtual int LeaveGroup(const IPAddressNumber& group_address) = 0;
 
   // Set the time-to-live option for UDP packets sent to the multicast
   // group address. The default value of this option is 1.
   // Cannot be negative or more than 255.
   // Should be called before Bind().
   // Returns a network error code.
   virtual int SetMulticastTimeToLive(int time_to_live) = 0;
 
   // Set the loopback flag for UDP socket. If this flag is true, the host
   // will receive packets sent to the joined group from itself.
   // The default value of this option is true.
   // Should be called before Bind().
   // Returns a network error code.
   virtual int SetMulticastLoopbackMode(bool loopback) = 0;
 
   // Set the Differentiated Services Code Point. May do nothing on
   // some platforms. Returns a network error code.
   virtual int SetDiffServCodePoint(DiffServCodePoint dscp) = 0;
 };
 
 }  // namespace net
 
 #endif  // NET_UDP_DATAGRAM_SERVER_SOCKET_H_