mod_asn looks up the AS and network prefix of IP address.

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mod_asn is an Apache module doing lookups of the autonomous system (AS) and the
network prefix that an IP address is contained in.

It is written with scalability in mind. To do high-speed lookups, it uses the
PostgreSQL ip4r datatype that is indexable with a Patricia Trie algorithm to
store network prefixes.

It comes with script to create such a database and update it with snapshots from
router's "view of the world".

The module sets the looked up data as env table variables, for use by other
Apache module to do things with it, and it can send it as response headers to
the client.


Example HTTP response headers:

HTTP/1.1 200 OK
Date: Thu, 12 Feb 2009 23:24:33 GMT
Server: Apache/2.2.11 (Linux/SUSE)
X-Prefix: 83.133.0.0/16
X-AS: 13237
Last-Modified: Wed, 11 Feb 2009 19:52:09 GMT
ETag: "c0ee5656-a55d-462a9f0652c40"
Accept-Ranges: bytes
Content-Length: 42333
Content-Type: application/x-rpm