Snort mailing list archives

Re: OpenPcap() (doc typo)


From: Gentoo-Wally <gentoowally () gmail com>
Date: Wed, 21 Jun 2006 10:48:52 -0400

FYI this was exactly the problem. Just wanted to post to note that
there is a typo in the 2.6.0 doc's in the config detection section...

– ac-sparebands Aho-Corasick Sparse-Banded (small memory, high performance)

Should probably be...

– ac-sparSebands Aho-Corasick Sparse-Banded (small memory, high performance)

Thx for the help,
Wally


On 6/20/06, Gentoo-Wally <gentoowally () gmail com> wrote:
That is probably exactly what I'm looking for. Thx for the reminder.

Wally

On 6/20/06, Justin Heath <justin.heath () gmail com> wrote:
This was posted from Steve Sturges a little while back on snort-users:

 "As noted in the RELEASE.NOTES, there was a change in the
 default pattern matching engine from Wu-Manber to standard
 Aho-Corasick which is faster but consumes more memory.

 This effectively replaced an implicit config of

 config detection: search-method mwm

 with

 config detection: search-method ac

 The Aho-Corasick implementation in snort has a few different
 memory models, standard, full, banded, sparse, and sparse
 banded.  The sparse and spare-banded ones consume much less
 memory... To use them, add a snort.conf line, as desired,
 for example.  Wu-Manber is being deprecated in the next
 release.

 config detection: search-method ac-sparsebands

 There is also the lowmem method, which is slow, but uses
 very little memory."


On 6/20/06, Gentoo-Wally <gentoowally () gmail com> wrote:
Thx. So do you think a jump from 25% usage in 2.4.5 to 90% usage in
2.6.0 on a machine with 1Gb ram should be expected?

On 6/20/06, Joel Esler <joel.esler () sourcefire com > wrote:
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Snort 2.6 uses more memory than it's predecessors.  The OpenPcap msg you
saw is normal, it's just telling you that there is no IP assigned to the
sniffing interface (eth0).  Which, if you are using a promisc card
interface with no IP, is exactly what you want...

Joel

Gentoo-Wally wrote:
I've started looking at snort 2.6.0 and have run into something
strange.

Compile info:
1. gcc 4.1.1
2. ./configure --enable-dynamicplugin --enable-dependency-tracking
--with-libpcap-includes=/usr/include/
--with-libpcap-libraries=/usr/lib/
3. Have tried libpcap 0.9.4 and the current version of phil woods
libpcap
4. Gentoo Linux box
5. 'ifconfig eth0 up promisc' to bring the interface up

No errors during ./configure && make && make install

when I start snort it hangs for 15-30 seconds at...

Initializing Network Interface eth0
OpenPcap() device eth0 network lookup:
        eth0: no IPv4 address assigned
Decoding Ethernet on interface eth0


I'm starting it like this..

/usr/local/bin/snort -i eth0 -u snort -l /var/log/snort -c
/usr/local/etc/snort/snort.conf

also tried...

/usr/local/bin/snort -i eth0 -l /var/log/snort -c
/usr/local/etc/snort/snort.conf


At this point memory consumption sky rockets to 95% usage even with
all preprocessors except flow turned off. After about 30 seconds it
finishes initializing and appears to work correctly but at 95% memory
consumption and swap usage begins kicking in.

I googled the OpenPcap message but found nothing that seems relevant
to my situation.

I also have a snort 2.4.5 install on the same box. When it starts I do
not see the OpenPcap message and it works flawlessly at around 18-24%
mem usage with all preprocessors on.

I also tried compiling 2.6.0 without the new dynamic preprocessors or
the dep tracking and I still get the openpcap message and crazy mem
usage.

Any ideas?

Wally


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