Snort mailing list archives

Re: Mmapped Capture on Linux


From: Mike Lococo <mikelococo () gmail com>
Date: Thu, 12 Aug 2010 17:57:17 -0400

It looks like the later versions will use mmap if possible.

A crude way to check on linux:  run this before and after starting Snort:

    grep -i mapped /proc/meminfo

The mapped allocation grows a bit and then bounces around after enabling
snort.  Prior to enabling snort, it's quite stable.  I assume this means
that we're using mmapped collection already.

BTW, you can go to Snort 2.9.0 and use afpacket.  That uses mmap and
works with live traffic both passive and inline.  :)

I'll have a peak at this.  I'm still seeing ~ 10% packet loss at
50mbit/sec on a fairly monstrous box with very little CPU usage.  I'll
also have to look into kernel-tuning a bit.  I've been spoiled by Endace
Dag cards on high-bandwidth links.  Monitoring a measly 150 megabits on
a commodity ethernet card seems difficult by comparison.

Thanks for your help.

Cheers,
Mike Lococo

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