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

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Date:	Tue, 24 May 2011 08:17:05 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Miller <davem@...emloft.net>,
	shemminger@...ux-foundation.org, jpirko@...hat.com,
	xiaosuo@...il.com, netdev@...r.kernel.org, kaber@...sh.net,
	fubar@...ibm.com, eric.dumazet@...il.com, andy@...yhouse.net,
	jesse@...ira.com
Subject: Re: [PATCH 1/3] vlan: Do not support clearing VLAN_FLAG_REORDER_HDR

On 05/24/2011 12:11 AM, Nicolas de Pesloüan wrote:
> Le 24/05/2011 06:20, Ben Greear a écrit :
> <snip>
>
>> Then I think we should put it back with pf_packet logic. Possibly with
>> a per-socket option to disable this and send it as only aux data if that
>> is more efficient.
>
> Why would we need a per-socket option for that?

I'd want the tag available at all times, but if it is a performance win to
put the tag in 'aux data', then a socket could opt for that method.  Otherwise,
the tag should always be inline in the packet.

>> If it turns out the NIC is not stripping VLAN tags for whatever reason,
>> we might be able to optimize things so that it never does the HW emulation
>> so that it never has to un-do it later.
>
> It might be very tricky to avoid any do-undo-redo situation. I will latter try and describe all the possible situations: with/without hw-accel, with/without a
> protocol handler registered on the parent interface, with/without a child interface build on top of a particular parent interface and with the corresponding
> VLAN ID...

You could optimize for some common cases, but leave fix-up code in place to add/remove the
tag properly before handing the packet to user-space, filters, etc.

Thanks,
Ben

>
> Nicolas.


-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com
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