We've been through this multiple times, but I think there still is no
"good" solution in-tree.

I have an urgent need to detect a detaching interface inside the kernel
(because I have stored the struct interface pointer and need to clear that).

And no, I don't realy want to interpret the stupid routing socket messages
for this simple (and probably not too uncommon) use, neither do I want to
hardcode a hack in if_detach.

What happened to the FreeBSD inspired callback-function-lists-with-linker-
magic (whose name I forgot)?

Martin