[PATCH 0/15] Pass keys down to ip_queue_xmit()

The final goal of this set of changes is to normalize all uses
of ip_queue_xmit() and how sockets are connected up so that
ip_queue_xmit() can elide it's usage of rt->rt_{src,dst}

Along the way I found some locking problems in L2TP fixed here.

Basically we reuse inet_sk->cork.fl to store keying information
and pass that (or something more appropriate) to ip_queue_xmit()

This opens up the door for SCTP to express exactly what is does, by
passing in a flow which is now added to the individual transport
instances.

Taking this one step further, we could add a "struct dst **dst"
argument to ->queue_xmit() and friends, then SCTP could pass in
"&transport->dst" and it would no longer need to do that special
"pre-hookup the DST to skb" uglyness.

L2TP could be modified similarly.

Then the pre-routed SKB code can be removed completely.

Signed-off-by: David S. Miller <davem@davemloft.net>