netdev - Re: [PATCH 1/3] vlan: Do not support clearing VLAN_FLAG_REORDER

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Message-ID: <20110524055836.GA2955@psychotron>
Date:	Tue, 24 May 2011 07:58:37 +0200
From:	Jiri Pirko <jpirko@...hat.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Changli Gao <xiaosuo@...il.com>,
	Ben Greear <greearb@...delatech.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	shemminger@...ux-foundation.org, kaber@...sh.net, fubar@...ibm.com,
	eric.dumazet@...il.com, andy@...yhouse.net,
	Jesse Gross <jesse@...ira.com>
Subject: Re: [PATCH 1/3] vlan: Do not support clearing VLAN_FLAG_REORDER_HDR

Mon, May 23, 2011 at 09:48:12PM CEST, nicolas.2p.debian@...il.com wrote:
>Le 23/05/2011 12:43, Jiri Pirko a écrit :
>>Mon, May 23, 2011 at 11:41:22AM CEST, ebiederm@...ssion.com wrote:
>>>Changli Gao<xiaosuo@...il.com>  writes:
>>>
>>>>On Mon, May 23, 2011 at 9:45 AM, Eric W. Biederman
>>>><ebiederm@...ssion.com>  wrote:
>>>>>>In another side, is there a specification which defines the
>>>>>>hw-accel-vlan-rx?
>>>>>
>>>>>I don't know.
>>>>>
>>>>>I have just been trying to clean up the mess since some of the
>>>>>hw-accel-vlan code broke my use case, by delivering packets with
>>>>>priority but no vlan (aka vlan 0 packets) twice to my pf_packet sockets.
>>>>>
>>>>
>>>>OK. But if we have decided to simulate the hw-accel-vlan-rx, I think
>>>>we'd better adjust the place where we put the emulation code. The very
>>>>beginnings of netif_rx() and neif_receive_skb() are better. Then rps
>>>>can support vlan packets without any change.
>>>
>>>That sounds nice. Patches are welcome.
>>>
>>>In principle it should be doable with some code motion.  I don't think
>>>moving vlan_untag earlier constitutes a bug fix.
>>
>>I do not think that is doable. Consider multi tagged packets. The place
>>just after "another_round" takes care about that.
>>
>>Btw what's the rationale to move untag to earlier position?
>
>Maybe simply because we try to mimic hw-accel, and hw-accel untagging
>definitely happens before we enter __netif_receive_skb and only
>happens once.
>
>So having software untagging inside the __netif_receive_skb loop looks different.

I understand. But what code prior to current vlan_untag position needs
to see the skb untagged?

>
>	Nicolas.
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