The ICMP Hostname Tools for Linux include a responder daemon, a lookup tool, and a nameswitch module to handle ICMP host name functions.
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:
* timeout – Sets the timeout in milliseconds for ICMP host name queries, by passing the -t option to idnlookup.
* nocache – Disables the cache.
* ttlnotfound – Sets the TTL for not-found cache entries is seconds. The default is 5 minutes.
Both icmpdnd and idnlookup need to run as root, due to the fact that they use ICMP. Thus, idnlookup needs be installed SUID root.
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