No Linux distro that I've seen so far supports RFC 1788 (<http://www.faqs.org/rfcs/rfc1788.html>), which describes a method for fetching the FQDN of a host over ICMP. It seems the BSDs support this, and it also seems to be suggested for Internet hosts. I have recently written a set of programs and a nameswitch module to support this (given by the URL of this bug). Just today, I received a contribution of an RPM spec for it as well, so I would like to suggest that Fedora Core 5 includes these programs, thereby possibly becoming the first Linux distro to support RFC 1788. It would also be convenient for me, so that I won't have to install it manually anymore. ;-) Fetching the FQDN over ICMP is very convenient for situations where you are communicating between, for example, two different home networks where no other method of reverse lookup is possible (it's not easy, if even possible, for a home user to get a delegation for an in-addr.arpa zone). It is thus the only way to, for example, do Kerberos authentication between two such networks.
We're going to pass on this one for Core, although it would make a fine addition to Fedora Extras.