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

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Date:	Thu, 1 Apr 2010 15:59:49 +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 15:48, Patrick McHardy wrote:
>Jan Engelhardt wrote:
>> On Thursday 2010-04-01 15:22, Patrick McHardy wrote:
>>>>>> Conntrack loops are prevented by using a dummy conntrack, just as 
>>>>>> NOTRACK does.
>>>>> [...]
>>>>>>  - 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.
>>>>> My question was about the case without conntrack.
>>>> Hm. Do you have any suggestion in countering a case whereby a user
>>>> does -I OUTPUT -j TEE without conntrack?
>>>>
>>>> Perhaps making nesting a feature that requires conntrack, such that the 
>>>> non-CT case can't loop?
>>> If we drop the reentrancy thing, what should work is to prevent
>>> using loopback as output device and using something similar to
>>> the recursion counters tunnel devices used to have.
>> 
>> Nah. I'm going to pick a bit from struct skbuff to indicate the
>> packet was teed so as to avoid that loop.
>
>That's a bad idea, we shouldn't be adding new skb members for something
>as peripheral as this module.

I would have done this, which does not add a member:

	IP6CB(skb)->flags |= IPSKB_CLONED;

>What's wrong with adding a reentrancy counter?

Sounds like a plan.
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