--iface-can-reach and DualStack

[flucas1]

The arg options --iface-can-reach do not seem to be working if using IPv6 addresses. It only seems to work for IPv4.
I would appreciate the option of --iface-regex for ipv4 and ipv6.

The context is that with dual stack and ipv6 privacy extensions the first ip (the selected) is always the changing one.
If there are several prefixes announced or private ipv6 ranges + routable ipv6 ranges, I would prefer to have some control on the say to select the IP.

This issue was already raised on the original ticket.
#1545 (comment)

--iface-regex also seems to be IPv4 only

[rbrtbnfgl]

Hi. I think it'll be complex to have a dualstack IP for that flag. I can update to accept also the IPv6 address.