netdev - Re: [PATCH 3/3] [NET_DOC] Document some simple rules for actions

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Message-ID: <20071016125134.GA11319@gondor.apana.org.au>
Date:	Tue, 16 Oct 2007 20:51:35 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	jamal <hadi@...erus.ca>
Cc:	David Miller <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 3/3] [NET_DOC] Document some simple rules for actions

On Tue, Oct 16, 2007 at 08:33:31AM -0400, jamal wrote:
>
> +2) If you munge any packet thou shalt call skb_expand in the case
> +someone else is referencing the skb. After that you "own" the skb. 
> +You must also tell us if it is ok to munge the packet (TC_OK2MUNGE), 
> +this way any action downstream can stomp on the packet.

Thanks for the documentation!

But I still think the distinction between skb_clone and
skb_copy_header is wrong.

When you munge a packet, it's still going to go back up
the stack and be processed along the same path.  Therefore
you should be calling pskb_expand_head.

In other words, this does not explain why skb_copy/pskb_copy
and skb_copy_expand should differ from skb_clone.  As far as
I can see all these functions should behave in the same manner
with respect to tc_verd.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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