Steffen Klassert says:
====================
This is the rework of the IPsec virtual tunnel interface
for ipv4 to support inter address family tunneling and
namespace crossing. The only change to the last RFC version
is a compile fix for an odd configuration where CONFIG_XFRM
is set but CONFIG_INET is not set.
1) Add and use a IPsec protocol multiplexer.
2) Add xfrm_tunnel_skb_cb to the skb common buffer
to store a receive callback there.
3) Make vti work with i_key set by not including the i_key
when comupting the hash for the tunnel lookup in case of
vti tunnels.
4) Update ip_vti to use it's own receive hook.
5) Remove xfrm_tunnel_notifier, this is replaced by the IPsec
protocol multiplexer.
6) We need to be protocol family indepenent, so use the on xfrm_lookup
returned dst_entry instead of the ipv4 rtable in vti_tunnel_xmit().
7) Add support for inter address family tunneling.
8) Check if the tunnel endpoints of the xfrm state and the vti interface
are matching and return an error otherwise.
8) Enable namespace crossing tor vti devices.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>