Merge branch 'lwtunnel'

Thomas Graf says:

====================
Lightweight & flow based encapsulation

This series combines the work previously posted by Roopa, Robert and
myself. It's according to what we discussed at NFWS. The motivation
of this series is to:

 * Consolidate code between OVS and the rest of the kernel and get
   rid of OVS vports and instead represent them as pure net_devices.
 * Introduce a lightweight tunneling mechanism which enables flow
   based encapsulation to improve scalability on both RX and TX.
 * Do the above in an encapsulation unspecific way so that the
   encapsulation type is eventually abstracted away from the user.
 * Use the same forwarding decision for both native forwarding and
   encapsulation thus allowing to switch between native IPv6 and
   UDP encapsulation based on endpoint without requiring additional
   logic

The fundamental changes introduces in this series are:
 * A new RTA_ENCAP Netlink attribute for routes carrying encapsulation
   instructions. Depending on the specified type, the instructions
   apply to UDP encapsulations, MPLS and possible other in the future.
 * Depending on the encapsulation type, the output function of the
   dst is directly overwritten or the dst merely attaches metadata and
   relies on a subsequent net_device to apply it to the packet. The
   latter is typically used if an inner and outer IP header exist which
   require two subsequent routing lookups to be performed.
 * A new metadata_dst structure which can be attached to skbs to
   carry metadata in between subsystems. This new metadata transport
   is used to provide a single interface for VXLAN, routing and OVS
   to communicate through metadata.

The OVS interfaces remain as-is but will transparently create a real
VXLAN net_device in the background. iproute2 is extended with a new
use cases:

  VXLAN:
  ip route add 40.1.1.1/32 encap vxlan id 10 dst 50.1.1.2 dev vxlan0

  MPLS:
  ip route add 10.1.1.0/30 encap mpls 200 via inet 10.1.1.1 dev swp1

Performance implications:
  The additional memory allocation in the receive path should have
  performance implications although it is not observable in standard
  throughput tests if GRO is properly done. The correct net_device
  model outweights the additional cost of the allocation. Furthermore,
  this implication can be relaxed by reintroducing a direct unqueued
  path from a software device to a consumer like bridge or OVS if
  needed.

    $ netperf  -t TCP_STREAM -H 15.1.1.201
    MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to
    15.1.1.201 (15.1.1.201) port 0 AF_INET : demo
    Recv   Send    Send
    Socket Socket  Message  Elapsed
    Size   Size    Size     Time     Throughput
    bytes  bytes   bytes    secs.    10^6bits/sec

     87380  16384  16384    10.00    9118.17

Changes since v1:
 * Properly initialize tun_id as reported by Julian
 * Drop dupliate netif_keep_dst() as reported by Alexei
====================

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