[netflow-tools] Flowd Filter Question

Damien Miller djm at mindrot.org
Wed Mar 15 07:39:02 EST 2006

On Tue, 14 Mar 2006, Nathan Einwechter wrote:

> I just installed flowd as part of a security management system I'm
> trying to pull together and am trying to refine the collection of
> NetFlow logs to reduce the amount of space eaten by the logs. As such, I
> am trying to filter out those entries I'm not interested in.
> Specifically, I am trying to filter out (discard) anything non-UDP or
> TCP and any connection which was not established (obviously for TCP
> only, we'll keep all UDP).
> How can this be done? I've been fiddling with the filters for a couple
> days now and just can't seem to get it.

You should be able to do something like:

discard all
accept proto udp
accept proto tcp tcp_flags mask 0x12 equals 0x12

# ACK = 0x10, SYN = 0x02


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