From: hyperbatus@gmx.de
To: Pascal Hambourg <pascal.mail@plouf.fr.eu.org>, netfilter@vger.kernel.org
Subject: Re: Netfilter internal packet flow
Date: Wed, 07 Apr 2010 10:59:08 +0200 [thread overview]
Message-ID: <20100407085908.64960@gmx.net> (raw)
In-Reply-To: <4BAB377A.5090107@plouf.fr.eu.org>
-------- Original-Nachricht --------
> Datum: Thu, 25 Mar 2010 11:14:18 +0100
> Von: Pascal Hambourg <pascal.mail@plouf.fr.eu.org>
> An: netfilter@vger.kernel.org
> Betreff: Re: Netfilter internal packet flow
> > According to my testing so far (linux kernel 2.6.26 / debian lenny),
> > the behaviour of these packets seems to contradict the documents and
> > graphics I have seen. Such packets seem to go through the INPUT and
> > OUTPUT chains of the FILTER table and through one or two chains of the
> > NAT table (I just can't remember exactly at the moment), but not through
> > the PREROUTING chain of the NAT table. This is confusing ...
>
[...]
> When a packet is looped back, it reaches the conntrack confirm after
> POSTROUTING, so it skips the nat PREROUTING chain. Anyway that makes
> sense : if the destination could be changed in PREROUTING, the packet
> may need to be re-routed through another interface but I don't think
> there is a routing decision after PREROUTING for the loopback (routing
> decision already took place on output). If you need DNAT on loopback,
> you can do it in OUTPUT.
Pascal,
thank you very much for your valuable time and the comprehensive explanation. I think I have got it now. Nevertheless, it would be nice to have some sort of graphics comprising really all of the packet flow for future reference and for showing to others.
I have seen many kinds of such pictures, from obviously wrong to (what I would consider) high quality. But none of these pictures seems to originate from the netfilter / iptables developers, and I am still not sure if the graphics I have mentioned in my original post are correct in every aspect.
So does anyone know about "official" graphics or an "official" complete explanation of the packet flow in netfilter? Or a good book? The reference material which is mentioned on the netfilter homepage doesn't help me; it seems to be mostly outdated and incomplete.
Thank you very much,
Peter
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prev parent reply other threads:[~2010-04-07 8:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-25 9:03 Netfilter internal packet flow hyperbatus
2010-03-25 10:14 ` Pascal Hambourg
2010-04-07 8:59 ` hyperbatus [this message]
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