Had a requirement to add extra global scope ip's to the loopback interface.
Did cp /etc/netif.d/interface to /etc/netif.d/loopback and added the stuff from /etc/init.d/loopback above the other stuff in the netif_pre_up () function.
Need to symlink /etc/init.d/netif.tmpl to /etc/init.d/netif.lo add it to boot run-level and remove loopback from it.
For a default setup /etc/conf.d/netif.lo will be:
This give you the option to add extra addresses + all the other nice stuff from funtoo network scripts like always available search domain and backup public dns etc...
This is working fine so far on my system although an interface restart to update settings complain about "RTNETLINK answers: File exists" The script could probably be optimized but to add "127.0.0.1/8" to the config won't work because that need to be local scope and the other addresses must be global scope.