[Snort-devel] var PKT_TIMEOUT in sfdaq.c

Russ Combs rcombs at ...402...
Wed Feb 29 17:28:32 EST 2012


On Wed, Feb 29, 2012 at 5:22 PM, Michael Altizer <maltizer at ...402...>wrote:

>  On 02/29/2012 05:00 PM, Guillaume Daleux wrote:
>
>  Hi all,****
>
> ** **
>
> We had some problems with snort and snort daq which use 100% of processing
> power. After debugging, we saw that our system had a lot of call to poll
> function.****
>
> ** **
>
> The function poll (call in daq) set with a default snort parameter
> (PKT_TIMEOUT = 1000) is called everytime and didn't respect this timeout of
> 1 second (maybe heisenbug because only one printf removed this problem).**
> **
>
> ** **
>
> We want to ask you, why this parameter is set to 1000 ms and not -1 ? The
> poll function is called to wait packets so why the snort daq uses a timeout
> and not directly value -1 which would block until a packet arrive ?****
>
> ** **
>
> Can we patch snort and change PKT_TIMEOUT to -1 ?****
>
> ** **
>
> ** **
>
> Thanks for your answer.****
>
> ** **
>
> ** **
>
>  Snort does certain "idle work" (see snort.c:SnortIdle()) each time the
> DAQ acquire call returns.  If you made the call fully blocking, it would
> only return in the case of an error/signal/breakloop, and that code would
> not execute [often enough] when the packet rate is too low.
>
> I do not know why the timeout was being ignored in your case, which seems
> to be the real issue.  You have not mentioned which DAQ module you are
> using.
>

If you are mucking about in the code, it would help to know what the call
to poll() is returning as well.

>
>
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