• infos = Information about network plugin is in keys below
• infos/author = Markus Raab elekt.nosp@m.ra@l.nosp@m.ibele.nosp@m.ktra.nosp@m..org
• infos/licence = BSD
• infos/provides = check
• infos/needs =
• infos/placements = presetstorage
• infos/status = maintained unittest nodep libc nodoc
• infos/metadata = check/ipaddr
• infos/description = Checks keys if they contain a valid ip address

This plugin is a check plugin that checks if a key contains a valid ip address. It uses the POSIX.1-2001 interface getaddrinfo() in order to check if an ip address is valid.

Purpose

While, in theory, a regular expression can express if a string is a network address, in practice, such an attempt does not work well. The reason is that an unmanageable number of valid shortenings for IPv6 addresses makes the regular expression hard to write and understand.

So the idea of building such a complicated regular expression was discarded, but instead a dedicated checker was introduced. The idea is to use the operating system facilities to resolve the network address. If this succeeds, it is guaranteed that this network address will be valid when it is resolved by the same interface afterwards.

Many network address translators coexist. In POSIX.1-2001 a powerful address translator is provided with the interface getaddrinfo(). It is a common network address translation for both IPv4 and IPv6. We used it to implement this plugin.

Usage

Every key tagged with the metakey check/ipaddr will be checked using getaddrinfo(). If additionally the values ipv4 or ipv6 are supplied, the address family will be specified. If supplied only numerical hosts are allowed. If left empty, the plugin will resolve domain names and look if it is reachable (i.e. "localhost" should most likely work on any system)