netdev - Re: [PATCH 1/2][RFC] vlan: use pskb_copy() when inserting a vlan tag by hand

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Message-ID: <4873A6BC.6030205@trash.net>
Date:	Tue, 08 Jul 2008 19:41:16 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Lennert Buytenhek <buytenh@...tstofly.org>
CC:	Nicolas Pitre <nico@....org>,
	Dale Farnsworth <dale@...nsworth.org>,
	Ashish Karkare <akarkare@...vell.com>,
	Jesper Dangaard Brouer <jdb@...x.dk>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/2][RFC] vlan: use pskb_copy() when inserting a vlan
 tag by hand

Patrick McHardy wrote:
>> Lennert Buytenhek wrote:
>>>>> When inserting a vlan tag into an skb by hand (in the case the
>>>>> target network device hardware does not support inserting a vlan
>>>>> tag by passing it in via the TX descriptor), making a copy of the
>>>>> skb to be modified by calling skb_copy() is overkill, since
>>>>> skb_copy() will needlessly linearize the skb, copying of all of
>>>>> the fragmented data around, and checksumming the paket in software
>>>>> even if the hardware is perfectly capable of doing that by itself.
>>>>>
>>>>> For this case, pskb_copy() does exactly what is needed and no more,
>>>>> so use that instead. 
> Actually, are you sure this patch is helping for the case
> you describe? The function you changed is only called on
> the RX path.

Could you try this one please?


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