linux-kernel - 答复: 答复: 答复: 答复: [PATCH] set fake_rtable's dst to NULL to avoid kernel Oops.

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Date:	Sat, 31 Mar 2012 15:29:53 +0800
From:	"Peter Huang (Peng)" <peter.huangpeng@...wei.com>
To:	'Eric Dumazet' <eric.dumazet@...il.com>
Cc:	linux-kernel@...r.kernel.org, harry.majun@...wei.com,
	zhoukang7@...wei.com, 'netdev' <netdev@...r.kernel.org>
Subject: 答复: 答复: 答复: 答复: [PATCH] set fake_rtable's dst to NULL to avoid kernel Oops.

Hi, Eric

Thanks very much for your reply.
I will refine this patch and send it out later.

--------------------------------
Peter Huang(peng)


> -----邮件原件-----
> 发件人: Eric Dumazet [mailto:eric.dumazet@...il.com]
> 发送时间: 2012年3月31日 13:41
> 收件人: Peter Huang (Peng)
> 抄送: linux-kernel@...r.kernel.org; harry.majun@...wei.com; zhoukang7@...wei.com; 'netdev'
> 主题: Re: 答复: 答复: 答复: [PATCH] set fake_rtable's dst to NULL to avoid kernel Oops.
> 
> On Sat, 2012-03-31 at 09:26 +0800, Peter Huang (Peng) wrote:
> > > > >Check net/bridge/br_netfilter.c and commits e688a6048076 (net: introduce
> > > > >DST_NOPEER dst flag )  4adf0af6818f3ea5 (bridge: send correct MTU value
> > > > >in PMTU (revised))
> >
> > Hi, Eric
> >
> > I confirmed the patch contents again.
> > For our case, NF_INET_PRE_ROUTING is involved, not NF_BR_LOCAL_IN.
> > It seems pre-routing is not included in the patch you mentioned.
> > BTW, our pkts are all ipv6 DHCP pkts(with MAC 33 33 00 01 00 02).
> >
> > We verified the patch bellow, and this works fine, no WARN_ON happened.
> 
> Hi Peter
> 
> I claim that your patch is not the good one and you need to refine it.
> 
> First, code is not needed if CONFIG_BRIDGE_NETFILTER is not set.
> 
> In fact, if CONFIG_BRIDGE_NETFILTER is not set, compilation will fail
> since fake_rtable doesnt exist in "struct net_bridge", so you fix a bug
> and introduce a new one.
> 
>   CC [M]  net/bridge/br_forward.o
> net/bridge/br_forward.c: In function ‘__br_forward’:
> net/bridge/br_forward.c:94: error: ‘struct sk_buff’ has no member named ‘_skb_dst’
> net/bridge/br_forward.c:94: error: ‘struct net_bridge’ has no member named ‘fake_rtable’
> make[1]: *** [net/bridge/br_forward.o] Error 1
> make: *** [_module_net/bridge] Error 2
> 
> 
> Then, the test is using obsolete dst internals and cast that should not
> be in a C file. :
> 
> if (skb->_skb_dst == (unsigned long)&to->br->fake_rtable)
> 
> So I suggested you take a look at net/bridge/br_netfilter.c code to see
> how this can be done properly. Maybe you need to add a helper in an
> include file to make this proper.
> 
> I hope this is now clear to you, because your initial patch cannot be
> applied as is. If you want full credit for this work, you must go a step
> forward, or else another guy will finish the job.
> 
> Thanks


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