Folks,

Has anyone figured out how to specify the outgoing interface for  IPv6  multicast  using the boost  asio  library socket options  on
Linux ?

See snippets below...

What value does one specify for  "unsigned int ipv6_interface"  in the network_interface constructor ?

Tried specifying the interface index (1..3 on my host)  but that did not work.


Thanks,
Jay ..



>From multicast.hpp
* Implements the IPPROTO_IP/IP_MULTICAST_IF socket option.
*
* @par Examples
* Setting the option:
* @code
* boost::asio::ip::udp::socket socket(io_service);
 * ...
* boost::asio::ip::address_v4 local_interface =
*   boost::asio::ip::address_v4::from_string("1.2.3.4");
* boost::asio::ip::multicast::outbound_interface option(local_interface);
* socket.set_option(option);
* @endcode
*
* @par Concepts:
* SettableSocketOption.
*/
#if defined(GENERATING_DOCUMENTATION)
typedef implementation_defined outbound_interface;
#else
typedef boost::asio::ip::detail::socket_option::network_interface<
  IPPROTO_IP, IP_MULTICAST_IF, IPPROTO_IPV6, IPV6_MULTICAST_IF>
  outbound_interface;
#endif

==========================================================
From:  socket_options.hpp ...
// Construct with IPv6 interface.
  explicit network_interface(unsigned int ipv6_interface)
  {
    ipv4_value_.s_addr =
      boost::asio::detail::socket_ops::host_to_network_long(
          boost::asio::ip::address_v4::any().to_ulong());
    ipv6_value_ = ipv6_interface;
  }