From: "Matthew Donofrio" <mdonof2@pride.hofstra.edu>
To: Cedric Blancher <blancher@cartel-securite.fr>
Cc: netfilter@lists.netfilter.org
Subject: Re: How exactly does RELATED work in Connection Tracking?
Date: Wed, 23 Oct 2002 08:57:06 -0700 [thread overview]
Message-ID: <000b01c27aac$d6b2a270$09c809c0@PENT4> (raw)
In-Reply-To: 1035325277.10494.18.camel@elendil
>Connection tracking relies on data structures. In those, to be quick,
>you have tuples that are used to recognise packets going both ways. A
>tuple is a set of datas that caracterize a packet for Netfilter. Theses
>tuples are used firstly to build conntrack table entries, and then to
>try to match theses entries against further packets. That means when you
>see a packet, you can calculate its own tuple, and then compare it to
>the ones that are in data structures that represent current conntracked
>flows.
>When a packet reaches the box, then Netfilter looks at it, extract from
>the header its own tuple and then compares it to known tuples that are
>part of current conntracked connections. If it matches one of theses
>tuples, then it is ESTABLISHED. It is also compared to all expectations.
>If it matches one expectation, then we know this packet is RELATED (and
>if it does not match anything, it is NEW). Then, we can create a new
>structure for him with tuples and so on and treat the flow as others.
The tuple is just the source address and destination address for a
particular packet, correct? So is it safe to say that the only fields that
are compared for connection tracking are the source and destination
addresses? So, if a packet comes in and the source and destination
addresses match an entry in the conntrack state table, then we can say that
it is part of some ESTABLISHED connection. Thanks again.
-Matt
next prev parent reply other threads:[~2002-10-23 15:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-22 5:48 How exactly does RELATED work in Connection Tracking? Matthew Donofrio
2002-10-22 22:21 ` Cedric Blancher
2002-10-23 15:57 ` Matthew Donofrio [this message]
2002-10-23 13:26 ` Cedric Blancher
2002-10-24 10:06 ` Antony Stone
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