Remember listen-on and listen-on-v6 are ACLs.  Take the addresses
on the system and apply check them against the ACL and if they match
open a socket.

listen-on { any; }; opens two sockets for every IPv4 interface (TCP
and UDP) so that UDP replies get the correct source address on
multi-homed machines.  TCP automatically does this.

For IPv6 the Advanced Sockets API lets you specify the source address
of UDP packets and to get the destination address of received packets
so its possible to get the reply source addresses correct with a
single socket for listen-on-v6 { any; }; if the OS supports it.

For AnyIP the server would have to take the ACL list, workout which
prefixes are actually complete addresses, then apply a 127/8 filter
to them and attempt to open them only on Linux boxes making sure not
to match any addresses already configured by matching against the
existing interfaces.

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka@isc.org