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

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Date:	Mon, 23 May 2011 12:43:40 +0200
From:	Jiri Pirko <jpirko@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Changli Gao <xiaosuo@...il.com>,
	Ben Greear <greearb@...delatech.com>,
	David Miller <davem@...emloft.net>,
	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>, 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 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?

>
>In my investigation earlier I found a non-trivial number of paths into
>__netif_receive_skb.  So it was not clear to me in the slightest how to
>move the check earlier without modifying every networking driver and a
>few other pieces of code.
>
>Why should receive packet steering be affected by vlan tags at all?
>
>Eric
>
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