I've finally finished merging the general encapsulation code for IPv4.
Here is the patch.

The idea is basically to make x->type->output similar in structure to
x->type->input.  That means moving the tunnel encapsulation and other
generic code out.

They have ended up in xfrm4_output.c.

The advantage of this is that we have exactly one copy of the tunnel
encapsulation code.  So if we need to change it (e.g., set the TTL
according to the route) then it's easier and less error-prone.

In fact, in doing so I've already noticed that the ECN wasn't being
copied correctly in everything except xfrm4_tunnel.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@redhat.com>