netdev - Re: [PATCH 1/4] netfilter: xt_connlimit: fix daddr connlimit in SNAT scenario

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Message-ID: <AANLkTimBV9x7Y-tUez5VMDoU+8mtaw1f48GV1yxgZ71c@mail.gmail.com>
Date:	Tue, 15 Mar 2011 07:49:04 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Jan Engelhardt <jengelh@...ozas.de>
Cc:	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 1/4] netfilter: xt_connlimit: fix daddr connlimit in SNAT scenario

On Tue, Mar 15, 2011 at 3:00 AM, Jan Engelhardt <jengelh@...ozas.de> wrote:
> On Monday 2011-03-14 13:42, Changli Gao wrote:
>
>>
>>Yes, you are correct only when there is no SNAT rule. If there is an
>>SNAT rule:
>>
>>-t nat -A POSTROUTING -p tcp --dport 80 -j SNAT --to-source 192.168.0.1
>>
>>the final tuples will be:
>>src = home dst = router src=1.2.3.4 dst=192.168.0.1
>>
>>However, the tuple saved by connlimit is src=1.2.3.4 dst=home, so this
>>conn will be removed later as there isn't any conntrack, which has
>>this tuple in any direction.
>
> But I don't yet see how your patch #1 can help. At the time
> conn->tuple = *tuple is done, *tuple still contains the non-SNATed
> tuple, and it is never updated again.
>

In this patch, conn->addr is used to save the destination/source
address instead of conn->tuple.src.u3, so the conn->tuple is used for
conntrack lookup only. Just as the original tuple isn't updated, we
can use it to looking up the associated conntrack all the time.

addr: 192.168.0.1
tuple: src = home, dst = router

-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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