netdev - Re: [PATCH] ip6tables: use skb->len for accounting

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Message-ID: <AANLkTik_2HMl3OaGvZiJPCO09Bu4lj6S0PNWFbw1BGXe@mail.gmail.com>
Date:	Fri, 23 Jul 2010 14:38:20 +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>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	"Pekka Savola (ipv6)" <pekkas@...core.fi>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] ip6tables: use skb->len for accounting

On Fri, Jul 23, 2010 at 2:16 PM, Jan Engelhardt <jengelh@...ozas.de> wrote:
>
>
> I wonder how this fares with trailing padding or data, like, when
> you have a standard v4/v6 packet created in a raw socket, and append
> a bunch of \0s to it.
>
>

For the packets received, ip_rcv, ipv6_rcv and bridge all call
pskb_trim_rcsum before feeding them to netfilter. The raw packets are
sent via dev_queue_xmit(), and they don't pass through the output path
of netfilter. One case, maybe the queued packets mangled "wrongly" in
userspace are reinjected, however, we can't prevent a user from
changing the payload_len wrongly.

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