DHCPv6 relay-forward message sent through wrong socket

[sodz]

When sending DHCPv6 relay-foward messages (dhcpv6.c:535), the used socket is bound to the slave interface (dhcpv6.c:63), while it is required to be sent through the master interface; thus the `sendmsg' system call returns EINVAL.
It seems that a UDP socket is also required on the master interface (dhcpv6.c:54), and the relay-forw message should be send through that socket. This solution works for me.

[sbyx]

Should be fixed in sbyx@60bb0a1 thanks.

[sodz]

But it was designed not to create such a socket on the master interface (dhcpv6.c:54):

if (enable && iface->dhcpv6 && !iface->master)

That should be fixed too, by deleting && !iface->master.