Michael Ströder:
Maybe this feature should be removed in 2.5 to make that really clear.
please don't...Everybody inspecting a log full with IPv6 connections for troubleshooting will *love* reverse DNS!
Apache has the similar problem + feature: http://httpd.apache.org/docs/2.4/mod/core.html#hostnamelookups
It exist, but the sane default is "off". Andreas