conntrack plugin: Add plugin to collect the connection tracking table size.

conntrack plugin: Add plugin to collect the connection tracking table size.

Hello,

I've adapted entropy plugin to get nf_conntrack entries, which is
important on Linux routers. Attached patch.

BTW you may want to take a look at PLD Linux spec file at
http://cvs.pld-linux.org/cgi-bin/cvsweb/SPECS/collectd.spec or
http://cvs.pld-linux.org/cgi-bin/cvsweb.cgi/SPECS/collectd.spec
as it's much more complex than Fedora, RH or SLES ones which are shipped
in contrib.

--
Tomasz Pala <gotar@pld-linux.org>