Add autotools and build system by Oron Peled.

[icmp-dn.git] / README

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+ICMP host name utilities
+
+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:
+
+    * icmpdnd – The ICMP Domain Name daemon, which listens to ICMP
+      domain name requests and replies to them.
+
+    * 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.
+
+    * libnss_icmp.so.2 – A glibc NSS module, which uses idnlookup to
+      perform queries for the gethostbyaddr function.
+
+General information
+
+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.
+