netdev - Re: [patch net-next-2.6] net: vlan: make non-hw-accel rx path similar to hw-accel

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Date:	Mon, 04 Apr 2011 22:47:48 +0200
From:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Jiri Pirko <jpirko@...hat.com>, Jesse Gross <jesse@...nel.org>,
	netdev@...r.kernel.org, davem@...emloft.net,
	shemminger@...ux-foundation.org, kaber@...sh.net, fubar@...ibm.com,
	eric.dumazet@...il.com, andy@...yhouse.net, xiaosuo@...il.com
Subject: Re: [patch net-next-2.6] net: vlan: make non-hw-accel rx path similar
 to hw-accel

Le 04/04/2011 21:51, Eric W. Biederman a écrit :

>
> __netif_receive_skb is actually late for untagging.  eth_type_trans
> would be better but not path of control into __netif_receive_skb
> actually calls eth_type_trans.

Because vlan may nest, we need to keep some sort of frame untagging inside __netif_receive_skb.

In order to avoid duplicate code, I suggest to manage the first level untagging (for non hwaccel) 
the same way we manage other levels of untagging (which are by design non hwaccell).

Hence my proposal to use a rx_handler on the parent device of the vlan device, if we know the parent 
device lack hwaccel vlan handling.

So, instead of trying to mimic the hwaccel path in software, I suggest to simply disable software 
untagging when we know hwaccel untagging is present, by removing (or not installing) the vlan 
rx_handler from the hwaccel net_device.

Can someone clarify whether hwaccel capable NIC will always untag tagged frames or will only do so 
if requested at device setup?

	Nicolas.
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