This patch against v2.6.31 adds support for route lookup using sk_mark in some 
more places. The benefits from this patch are the following.
First, SO_MARK option now has effect on UDP sockets too.
Second, ip_queue_xmit() and inet_sk_rebuild_header() could fail to do routing 
lookup correctly if TCP sockets with SO_MARK were used.
Signed-off-by: NAtis Elsts <atis@mikrotik.com>
Acked-by: NEric Dumazet <eric.dumazet@gmail.com>