already belongs or removing it from a group to which it does not
belong. This makes it possible to include group memberships in
ifconfig_foo0 in rc.conf without fear of breaking "service netif
restart foo0".
MFC after: 3 days
operations. This allows the query operations to work in non-IPv4 jails,
and will be necessary in a future of possible non-INET networking.
Approved by: bz (mentor)
order to - for example - apply firewall rules to a whole group of
interfaces. This is required for importing pf from OpenBSD 3.9
Obtained from: OpenBSD (with changes)
Discussed on: -net (back in April)
