linux-kernel - Re: [PATCH] netfilter: Fix br_nf_pre_routing() in conjunction with bridge-nf-call-ip(6)tables=0

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Message-ID: <4F04DD19.601@nod.at>
Date:	Thu, 05 Jan 2012 00:13:29 +0100
From:	Richard Weinberger <richard@....at>
To:	Bart De Schuymer <bdschuym@...dora.be>
CC:	Stephen Hemminger <shemminger@...tta.com>, davem@...emloft.net,
	bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] netfilter: Fix br_nf_pre_routing() in conjunction with
 bridge-nf-call-ip(6)tables=0

Am 04.01.2012 18:55, schrieb Bart De Schuymer:
> Op 3/01/2012 21:29, Richard Weinberger schreef:
>> Am 03.01.2012 21:15, schrieb Bart De Schuymer:
>>> The documentation is probably not explicit enough, but I would keep the
>>> behavior as it is now. Setting bridge-nf-call-iptables to 0 makes
>>> iptables behave as if bridge-netfilter was not enabled at compilation.
>>> Anyway, your patch is almost certainly flawed since the fact that
>>> skb->nf_bridge can be NULL is used as part of the logic in
>>> br_netfilter.c: it indicates that bridge-nf-call-iptables was 0 when the
>>> packet was first processed by bridge-netfilter and should therefore not
>>> be given to iptables in any other netfilter hook.
>> Thanks for the explanation!
>>
>> Wouldn't it make sense to check for bridge-nf-call-iptables in
>> xt_physdev?
>> So that the user gets warned that his iptables rule will never match...
> 
> We don't want to introduce module dependencies between the bridge module
> and the iptables physdev match.

CONFIG_NETFILTER_XT_MATCH_PHYSDEV depends anyway on
CONFIG_BRIDGE_NETFILTER...

> We could add a message to the syslog whenever these proc settings are
> changed (in br_netfilter.c::brnf_sysctl_call_tables()).
> 

Let's export brnf_call_iptables and brnf_call_ip6tables, such that
physdev_mt_check() can notify the user that his iptables rule will have
no effect.

Thanks,
//richard


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