Merge branch 'mpls-in-ipv4-and-udp'

Simon Horman says:

====================
net: support MPLS in IPv4 and UDP

This short series provides support for MPLS in IPv4 (RFC4023), and by
virtue of FOU, MPLS in UDP (RFC7510).

The changes are as follows:
1. Teach tunnel4.c about AF_MPLS, it already understands AF_INET and
   AF_INET6
2. Enhance IPIP and SIT to handle MPLS. Both already handle IPv4.
   SIT also already handles IPv6.
3. Trivially enhance MPLS to allow routes over SIT and IPIP tunnels.

A corresponding patch set for iproute2 has also been provided.

Changes since v1
* Correct inverted IPIP protocol logic in SIT patch
* Provide usage example below

Sample configuration follows:

* The following creates a tunnel and routes MPLS packets whose outermost
  label is 100 over it. The forwarded packets will have the outermost label
  stack entry, 100, removed and two label stack entries added, the
  outermost having label 200 and the next having label 300.

  The local end-point for the tunnel is 10.0.99.192 and the remote
  endpoint is 10.0.99.193.

  The local address for encapsulated packets is 10.0.98.192 and the
  remote address is 10.0.98.193.

  # Create an MPLS over IPv4 tunnel using the IPIP driver
  ip link add name tun1 type ipip remote 10.0.99.193 local 10.0.99.192 \
	ttl 225 mode mplsip

  # Bring the tunnel up and an add an IPv4 address and route
  ip link set up dev tun1
  ip addr add 10.0.98.192/24 dev tun1

  # Set MPLS route
  # Allow MPLS forwarding of packets recieved on eth0
  echo 1 > /proc/sys/net/mpls/conf/eth0/input
  # Larger than label to be routed (100)
  echo 101 > /proc/sys/net/mpls/platform_labels
  ip -f mpls route add 100 as 200/300 via inet 10.0.98.193

* For FOU (in this case MPLS over UDP) a tunnel may created using:

  # Packets recieved on UDP port 6635 are MPLS over UDP (IP proto 137)
  ip fou add port 6635 ipproto 137
  # Create the tunnel netdev
  ip link add name tun1 type ipip remote 10.0.99.193 local 10.0.99.192 \
	ttl 225 mode mplsip encap fou encap-sport auto encap-dport 6635

  IPv4 address, link and route, and MPLS routing commands are as per
  the MPLS over IPv4 example

* To use the SIT driver instead of the IPIP driver "ipip" may be substituted
  for "sit" in the above examples.

* To create a tunnel that forwards and receives all supported
  inner-protocols "mplsip" may be substituted for "any" in the above
  examples.

  For the IPIP driver this configures both IPv4 and MPLS over IPv4.
  For the SIT driver this configures IPv6, IPv4 and MPLS over IPv4.
====================

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