netdev - Re: [PATCH] core/dev: set pkt_type after eth_type_trans() in dev_forward

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Message-Id: <20130704.145712.2078075601927798473.davem@davemloft.net>
Date:	Thu, 04 Jul 2013 14:57:12 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	nicolas.dichtel@...nd.com
Cc:	yamahata@...inux.co.jp, netdev@...r.kernel.org,
	murphy.mccauley@...il.com, jasowang@...hat.com, mst@...hat.com,
	edumazet@...gle.com, kaber@...sh.net, honkiko@...il.com,
	ramirose@...il.com, tparkin@...alix.com, xiyou.wangcong@...il.com,
	pshelar@...ira.com, jesse@...ira.com, dev@...nvswitch.org
Subject: Re: [PATCH] core/dev: set pkt_type after eth_type_trans() in
 dev_forward_skb()

From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
Date: Wed, 03 Jul 2013 16:53:52 +0200

> Le 03/07/2013 01:00, David Miller a écrit :
>> From: Isaku Yamahata <yamahata@...inux.co.jp>
>> Date: Tue,  2 Jul 2013 20:30:10 +0900
>>
>>> The dev_forward_skb() assignment of pkt_type should be done
>>> after the call to eth_type_trans().
>>>
>>> ip-encapsulated packets can be handled by localhost. But skb->pkt_type
>>> can be PACKET_OTHERHOST when packet comes via veth into ip tunnel
>>> device.
>>> In that case, the packet is dropped by ip_rcv().
>>> Although this example uses gretap. l2tp-eth also has same issue.
>>> For l2tp-eth case, add dummy device for ip address and ip l2tp
>>> command.
>>   ...
>>> Signed-off-by: Isaku Yamahata <yamahata@...inux.co.jp>
>>
>> Applied, but I had to adjust the patch because in net-next we use
>> a new helper function (skb_scrub_packet()) to clear things out from
>> dev_forward_skb().
> What about calling skb_scrub_packet() after eth_type_trans()?
> 
> I wonder if the same problem may happen the day gre will support
> x-netns,
> because skb_scrub_packet() is also called before eth_type_trans() in
> ip_tunnel_rcv().

That's a fine suggestion, I was just being overly conservative in my
forward-porting of his patch.
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