Merge branch 'selftests-forwarding-Add-VRF-based-tests'

Ido Schimmel says:

====================
selftests: forwarding: Add VRF-based tests

One of the nice things about network namespaces is that they allow one
to easily create and test complex environments.

Unfortunately, these namespaces can not be used with actual switching
ASICs, as their ports can not be migrated to other network namespaces
(NETIF_F_NETNS_LOCAL) and most of them probably do not support the
L1-separation provided by namespaces.

However, a similar kind of flexibility can be achieved by using VRFs and
by looping the switch ports together. For example:

                             br0
                              +
               vrf-h1         |           vrf-h2
                 +        +---+----+        +
                 |        |        |        |
    192.0.2.1/24 +        +        +        + 192.0.2.2/24
               swp1     swp2     swp3     swp4
                 +        +        +        +
                 |        |        |        |
                 +--------+        +--------+

The VRFs act as lightweight namespaces representing hosts connected to
the switch.

This approach for testing switch ASICs has several advantages over the
traditional method that requires multiple physical machines, to name a
few:

1. Only the device under test (DUT) is being tested without noise from
other system.

2. Ability to easily provision complex topologies. Testing bridging
between 4-ports LAGs or 8-way ECMP requires many physical links that are
not always available. With the VRF-based approach one merely needs to
loopback more ports.

These tests are written with switch ASICs in mind, but they can be run
on any Linux box using veth pairs to emulate physical loopbacks.

v2:
* Order local variables declaration according to function arguments
  order (Petr)

v1:
* Change location to net/forwarding instead of forwarding/
* Add ability to pause on failure
* Add ability to pause on cleanup
* Make configuration file optional
* Make ping/ping6/mz configurable
* Add more tc tests
====================

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