oidentd (an identd daemon)

oidentd is an ident (rfc1413 compliant) daemon that runs on Linux, Darwin,
FreeBSD, OpenBSD, NetBSD and Solaris. oidentd can handle IP masqueraded/NAT
connections on Linux, Darwin, FreeBSD (ipf only), OpenBSD and NetBSD.
oidentd has a flexible mechanism for specifying ident responses. Users can
be granted permission to specify their own ident responses. Responses can
be specified according to host and port pairs.