TIp6Mreq.

Used by IPv6 or IPv4 multicast join/leave group socket options KSoIp6JoinGroup and KSoIp6LeaveGroup.

Joining to a multicast group address adds this address to the list of addresses for which incoming packets are accepted. Optionally, if the required support has been installed, some MLD (Multicast Listener Discovery) protocol messages may be generated.

The multicast join/leave are always interface specific, and the interface index should be specified in the set option call. If the index value is set to 0, the stack attempts to select some interface.