[Snort-users] Iptables and snort inline

Victor Julien victor at ...12319...
Thu Jun 9 02:17:43 EDT 2005

lmarcilly at ...12243... wrote:
> Hi all!
> I try to use iptables and snort inline on a bridging firewall. This is my configuration for testing :
> ------         ----------
> | PC |---------| Bridge |--------- LAN
> ------         ----------
> When snort inline does not run, I can't reach the LAN. I think it's normal but it's not what i want. In fact, i would like that when snort inline doesn't run, iptables don't put packet in the queue. Like this, even if traffic isn't analysed by snort, i always can reach the LAN...
> I can't find info in the snort user mailling list archive because source-forge is down for the moment so i hope you have a solution to my problem...
> Is there a patch to apply to iptables in order to react when snort is down? Or is this only a problem in the rules?

I believe that when you use QUEUE rules, the packets will be dropped if
1. no snort_inline is running.
2. snort_inline hangs for some reason.

The packets cannot continue travesing the rules because when the QUEUE
target is used, the packets basicly leave the netfilter framework, only
to be reinserted when the verdict is set. For the verdict to be set, the
QUEUE-listener must be running :-)

If snort_inline is not running because it crashed, you could try the
1. send a bugreport to snort-inline-users
2. write a script that checks if snort-inline runs, and if it doesn't,
starts it again.
3. as 2, but instead of starting snort-inline again, change the iptables
rules so ACCEPT is used instead of QUEUE.

Hope this helps!


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