[Snort-devel] [PATCHES] Fixes for daq_nfq

Kelvie Wong kwong at ...3121...
Tue Nov 2 16:31:21 EDT 2010


On November 2, 2010 01:08:36 pm Russ Combs wrote:
 > Too bad NFQ is so buggy.  Any idea when this fails and when not?  Is it
> certain traffic?
> 

I am not quite sure.  Mainly I have been testing this with a nmap scan of the 
TCP ports; this also happens for a storm of TCP packets as well.  I hadn't 
tested this against other types of traffic, prior to apply this patch.

> If this happens always or never, for a given run of Snort, the patch is
> reasonable.  If it is every other packet, we may be better off just adding
> the smallest delta possible to the timestamp to keep them sequenced.

For the type of traffic I had tested (I placed printf statements inside 
there), it was every single packet, and not just some of them.
 
> The freeze scenario should be eliminated with daq 0.3.  Can you verify
> that?

I do not have a test bench set up right now, but I may be able to get a few 
tests in later after I have exhausted my other committments.

> 
> The early exit is a little different.  Does this indicate a permanent
> error?  Can you elaborate on the conditions?
> 
> The errors were presumbed permanent and Snort exits to avoid consuming
> excessive resources.

I have attached a packet capture that can reproduce it every single time on 
one of our hardware configurations -- I have not tested it elsewhere.  Packets 
are still queued normally from NFQ after nfq_handle_packet returns an error.

Snort exits at around the 1000th packet.

As I have mentioned earlier, I don't have a test environment set up currently 
(nor the time to set it up), so I'm terribly sorry I can't be of more help 
right now.

-- 
Kelvie Wong
Software Developer

Wurldtech Security Technologies Inc.
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