[Snort-devel] Trivial question

Russ Combs rcombs at ...402...
Thu Sep 12 16:22:09 EDT 2013


Yes.  What matters is whether you are in IPS mode or not.  That can be done
with a pcap too.


On Thu, Sep 12, 2013 at 4:19 PM, Reinoud Koornstra <sockstat at ...445...>wrote:

> Ok, thanks.
> Does this also hold for snort reading a pcap containing an ftp session?
>
>  ------------------------------
> Date: Thu, 12 Sep 2013 15:50:21 -0400
> Subject: Re: [Snort-devel] Trivial question
> From: rcombs at ...402...
> To: sockstat at ...445...
> CC: snort-devel at lists.sourceforge.net
>
>
> Snort reassembles different protocols differently.  The 17K number is
> close to the paf_max default of 16K.  PDUs (protocol data units like an
> HTTP response) larger than paf_max are truncated into paf_max blocks for
> processing by Snort.  The FTP data channel does not get reassembled in that
> fashion.  Simplifying things, in inline IPS mode, it will reassemble every
> 2 data segments.  Otherwise, every 2 or more acknowledged data segments,
> upon acknowledgement.  Typically this will be around 2*1460 = 2920 bytes.
>
> So, based on the limited info in your question, the answer is yes, that is
> correct.
>
>
> On Wed, Sep 11, 2013 at 3:17 PM, Reinoud Koornstra <sockstat at ...445...>wrote:
>
>  Dear Everyone,
>
> When i run http traffic through snort, while snort is in inline mode and
> monitoring the sizeo of the packets, I see that every 4 of more full mtu
> packets a packet of 17k bytes is being processed by snort. I am seeing this
> with most kind of traffic, but not with ftp.
> Is that correct or not?
> Thanks,
>
> Reinoud.
>
>
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