On Sat, 2012-11-17 at 00:00 +0000, Ben Hutchings wrote:

I'm not sure what you mean by this.  Is your point that the
copy-on-write is never needed?  It is still possible for pskb_may_pull()
to fail.

A packet sniffer should have a copy of bad frames, even if dropped later
in our stacks.

GRO layer is not allowed to drop a frame, even if not 'correct'.