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

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Date:	Tue, 03 Jan 2012 18:42:41 +0100
From:	Richard Weinberger <richard@....at>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	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 03.01.2012 17:15, schrieb Stephen Hemminger:
> On Tue,  3 Jan 2012 14:26:04 +0100
> Richard Weinberger <richard@....at> wrote:
> 
>> If net.bridge.bridge-nf-call-iptables or net.bridge.bridge-nf-call-ip6tables
>> are set to zero xt_physdev has no effect because skb->nf_bridge has not been set up.
>>
>> Signed-off-by: Richard Weinberger <richard@....at>
> 
> I am not sure if this is a valid configuration. The setting of sysctl is saying
> "don't do iptables on bridge (since I won't be using it)" and then you are later
> doing iptables and expecting the settings as if the iptables setup was being
> done.

I don't think so.

Also rules like this one are broken:
iptables -A INPUT -i bridge0 -m physdev --physdev-in eth0 -j ...

No firewalling is done on the bridge, xt_physdev is only using some meta
information.

At least a big fat warning would be nice that xt_physdev does not work
if bridge-nf-call-iptables=0.
It took me some time to figure out why my firewall rule set gone nuts on
RHEL6...

> Instead, you should just enable the net.bridge.bridge-nf-call-iptables sysctl.
> If a distro chooses to disable it then you may have to do it explicitly.

Fedora and RHEL have net.bridge.bridge-nf-call-iptables=0 per default
due to KVM network performance issues.
I'm sure I'm not the only user of xt_physdev on RHEL and friends.

Thanks,
//richard

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