netdev - Re: [PATCH] net: bridge: check the length of skb after nf_bridge_maybe_copy

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Message-ID: <AANLkTingFk8qJ8tBwSRCxD=9k-0O3GnTv9V9TbF4N=bg@mail.gmail.com>
Date:	Mon, 3 Jan 2011 18:44:59 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	shemminger@...ux-foundation.org, bridge@...ts.linux-foundation.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] net: bridge: check the length of skb after nf_bridge_maybe_copy_header()

On Sat, Jan 1, 2011 at 3:10 AM, David Miller <davem@...emloft.net> wrote:
> From: Changli Gao <xiaosuo@...il.com>
> Date: Sat, 25 Dec 2010 21:41:30 +0800
>
>> Since nf_bridge_maybe_copy_header() may change the length of skb,
>> we should check the length of skb after it to handle the ppoe skbs.
>>
>> Signed-off-by: Changli Gao <xiaosuo@...il.com>
>
> This is really strange.
>
> packet_length() subtracts VLAN_HLEN from the value it returns, so the
> correct fix seems to be to make this function handle the PPPOE case
> too.
>

It is correct. The actual MTU of 802.1q frame is 4 bytes larger. For
example, the MTU of ethernet is normally 1500, however the actual MTU
of the 802.1Q is 1504.

Please see this patch:
http://git.kernel.org/?p=linux/kernel/git/davem/net-next-2.6.git;a=commitdiff;h=c893b8066c7bf6156e4d760e5acaf4c148e37190;hp=3c0fef0b7d36e5f8d3ea3731a8228102274e3c23

> Otherwise I suspect you have many other functions to fix as well.
>
> I'm not applying this patch.
>



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