From: Florian Westphal <fw@strlen.de>
Date: Sat, 4 Jan 2014 14:51:32 +0100

Archeology exercise #1 digs up 3b04ddde02c in linux.git, which
creats header_ops->rebuild, from the old  dev->rebuild_header.

Exercise #2 then finds commit 275513d2e1c78 in netdev-vger-cvs.git tree.
Quote from commit message:

        - dev->rebuild_header WILL DISAPPEAR. All the code
          relying on its existance is wrong, though still works.

Alexey calling from 1997 ;-)

These protocols which use the broken ARP ops are special, the
problem is that they do things like send packets out when their
header ops are invoked.

It's non-trivial to undo this design, and these aren't easy protocols
to test.

That's why we've had this compat stuff for them for more than a
decade.