From: Stephen Hemminger <stephen.hemminger@vyatta.com>
Date: Thu, 30 Dec 2010 15:06:16 -0800

quoted text
> Although copy is slower for large packets, this is a non performance
> path. The code in question is for bridged multicast Ipv6 ICMP
> packets. This case is so uncritical it could be done in BASIC and no
> one could possibly care!

I still think we should be judicious and keep using skb_clone() here.

Simply combine the two pskb_may_pull() calls into one on "skb2" after
the clone and before the blind __skb_pull() call.  Then add a error
path "out:" called "out_nopush:" for the error path to goto.

Also, I think the "+ 1" in the ipv6 stack code comes from the fact that
the parsing loop can "peek" into the next header's byte to see the type.
And I really don't think it's relevant here.

Also, all of these "x_header + ... + 1 - skb->data" factors are
irrelevent and shouldn't be used.  Just pass "offset + sizeof(*icmp6h)"
to pskb_may_pull().

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