Subject: Re: RFC: pskb_expand_head instead of skb_copy in skb_checksum_help

From: "David S. Miller" <[email-masked]>
Date: Tue, 24 Aug 2004 17:17:09 -0700

On Tue, 24 Aug 2004 21:05:32 +1000
Herbert Xu <[email-masked]> wrote:

> Here is the patch that you wanted to shoot holes at :)
> 
> The idea is simple.  None of the callers of skb_checksum are passing it
> skb's which are shared.  They may be cloned however.  But the application
> checksum is always in the skb header so there is no need to linearise it.
> 
> Supposing all these assumptions are correct, then we can avoid the overhead
> of skb_copy() and get away with pskb_expand_head().

I'm going to apply this.

If your assertion is wrong, then the skb_shared() BUG() will trigger
in pskb_expand_head() and we will know :-)