From: Patrick McHardy <redacted>
Date: Sat, 29 Sep 2007 17:21:23 +0200
Unfortunately gcc doesn't perform tail call optimization when the
address of a parameter or local variable is passed to an extern
function before the tail call, which NF_HOOK does for the skb.
To which Herbert later asked why we need the **pskb thing.
The reason is that if we have to COW or resize the SKB it
could result in a realloc of the sk_buff struct which is
why we need the **pskb thing.
But strangely I can't find any skbuff.h interfaces that
require that any longer :-))) So this might be some artifact
that we can in fact kill off.