When we run a config with mcast_addr="239.5.5.5" in an IPv6 stack, then the channel won't be created due to the sanity check exception.

Solution: map the IPv4 multicast address to an IPv6 equivalent, e.g.

239.5.5.5 --> FF0e::239.5.5.5, as outlined in [1]

[1] http://www.6net.org/publications/standards/draft-venaas-mboned-v4v6mcastgw-00.txt
[2] http://www.faqs.org/rfcs/rfc2529.html