Description:

Since the Linux kernel does not support the ICMP host name
facilities as described in RFC 1788, I wrote a simple
implementation in user-space. It comprises three parts:

o icmpdnd - The ICMP Domain Name daemon, which listens to ICMP
domain name requests and replies to them.
o idnlookup - A user utility to query a host for its host name
over ICMP. Like ping and all other utilities that use ICMP, it
needs to be installed SUID root.
o libnss_icmp.so.2 - A glibc NSS module, which uses idnlookup to
perform queries for the gethostbyaddr function.


The NSS module caches all requests (including failures) and honors
the TTL value sent by the responding host. It uses a configuration
file called /etc/nss-icmp.conf, which controls different aspects
of its operation: