The sunrpc server code needs to know the source and destination address for
UDP packets so it can reply properly.  It currently copies code out of the
network stack to pick the pieces out of the skb.  This is ugly and causes
compile problems with the IPv6 stuff.

So, rip that out and use recv_msg instead.  This is a much cleaner interface,
but has a slight cost in that the checksum is now checked before the copy, so
we don't benefit from doing both at the same time.  This can probably be
fixed.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>