Anope does not store this info by default so still need a module to get it and store it, and Anope does nothing with the IP other then filter it down into the zline bans to make sure its not banned after that the information is lost.
Still waiting on SNU final spec of the module, who knows he may want something a bit more then just pulling it for a given user.
DNS lookups are easy just need a fast enough lib to get the data, this is how for the most part BOPM have been doing so well, all they do is take the host, resolve it and tack it to a lookup host and resolve again.