ipsec_isloopbackaddr(3) on Linux
The text 09282d5669ee, as Debian 5.0 (Lenny) shipped it.
get "any" address ipsec isanyaddr - test address for equality to "any" address ipsec unspecaddr - get "unspecified" address ipsec isunspecaddr - test address for equality to "unspecified" address ipsec loopbackaddr - get loopback address ipsec isloopbackaddr - test address for equality to loopback address