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

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Message-ID: <4DDB5C1B.9000207@gmail.com>
Date:	Tue, 24 May 2011 09:19:55 +0200
From:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
To:	Jiri Pirko <jpirko@...hat.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

Le 24/05/2011 07:58, Jiri Pirko a écrit :
<snip>

>>> 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?

Any protocol handlers (ptype_all or ptype_base) registered on the parent interface may need to see 
the skb untagged, for all the reasons given in this thread. Arguably, doing software untagging 
earlier wouldn't help. :-) We need a strong logic to decide whether and when to untag and/or 
possibly re-tag.

	Nicolas.
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