From mboxrd@z Thu Jan  1 00:00:00 1970
From: lucien xin <lucien.xin@gmail.com>
Subject: Re: [PATCH] ip_tunnel:multicast process cause panic due to
 skb->_skb_refdst NULL pointer
Date: Fri, 28 Feb 2014 09:27:35 +0800
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	<20140224145807.GG6598@order.stressinduktion.org>
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On Mon, Feb 24, 2014 at 10:58 PM, Hannes Frederic Sowa
<hannes@stressinduktion.org> wrote:
>
> If the packet is locally forwarded we can test for IPCB(skb)->flags &
> IPSKB_FORWARDED.
>

thanks for  your reply,  hannes

IPSKB_FORWARDED is locally forwarded flag, but in ip_tunnel_rcv(), it
check if the packet
is a *looped back packet* (not about locally forwarded), the path is
__ip_route_output_key()-->
__mkroute_output()(rth->dst.output = ip_mc_output), then,
ip_mc_output()-->dev_loopback_xmit(),
 which happen when inet_sk(sk)->mc_loop =1, and in __mkroute_output(),
rth->rt_is_input = 0.
 In that path, IPCB(skb)->flags &IPSKB_FORWARDED always 0.

so I think 'IPCB(skb)->flags &IPSKB_FORWARDED' cannot meet the goal.