netdev - Re: [PATCH 5/5] netfilter: xt_TEE: have cloned packet travel through Xtables too

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Date:	Thu, 1 Apr 2010 13:03:49 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Patrick McHardy <kaber@...sh.net>
cc:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] netfilter: xt_TEE: have cloned packet travel through
 Xtables too

On Thursday 2010-04-01 12:37, Patrick McHardy wrote:

>Jan Engelhardt wrote:
>> Since Xtables is now reentrant/nestable, the cloned packet can also go
>> through Xtables and be subject to rules itself.
>
>That sounds dangerous if conntrack isn't used to prevent loops.

Conntrack loops are prevented by using a dummy conntrack, just as 
NOTRACK does.

>Is that really useful? For filtering, you can simply apply the
>rules before deciding to TEE the packet.

I can think of a handful of applications:
 - CLASSIFY

 - When the cloned packets gets XFRMed or tunneled, its status switches 
   from "special" to "plain". Doing policy routing on them does not seem 
   so far-fetched.
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