[Bro] Select Loop

Joel Ebrahimi joel.ebrahimi at gmail.com
Wed Apr 2 12:20:58 PDT 2008

I have been working on Bro on both an Intell and Bivio platform. On the
Bivio system there is some strange occurence where if I my capture_filters
are excluding traffic it will cause the application to periodically stall
and completley destroy performance. Profiling did not really turn up much. I
coded in some timers into the code and noticed the stalls were happening in
post pcap_next() and prior to calling for the next packet. I never got to
the root of the problem but by disabling the select loop my performance sky

This build will not to communicate with other nodes so this sounds like a
perfect solution.


// Joel

On Wed, Apr 2, 2008 at 12:41 PM, Robin Sommer <robin at icir.org> wrote:

> On Tue, Apr 01, 2008 at 18:28 -0700, you wrote:
> > of the event loop. I looked at the code and noticed this will put pcap
> into
> > blocking mode, but Im not sure what other impact this may have.
> That's right, disabling the select loop will let Bro use blocking
> pcap descriptors. That's the only difference and it is only
> noticable when using other input than packets as well, in particular
> when doing communication with other Bro nodes. If pcap blocks,
> communication can stall.
> Historically, Bro used to use only blocking descriptors, which we
> changed when introducing the communication. Initially, the
> non-blocking select loop was optional and needed to be turned on
> explicitly. These days however it is the default and I don't really
> know any reason to turn it off. The option to go back to blocking is
> just a relict from the old times.
> Any particular reason why you're interested in this?
> Robin
> --
> Robin Sommer * Phone +1 (510) 666-2886 * robin at icir.org
> ICSI/LBNL    * Fax   +1 (510) 666-2956 *   www.icir.org
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