selftests: net: Test for the IOAM insertion with IPv6

selftests: net: Test for the IOAM insertion with IPv6

This test evaluates the IOAM insertion for IPv6 by checking the IOAM data
integrity on the receiver.

The topology is formed by 3 nodes: Alpha (sender), Beta (router in-between)
and Gamma (receiver). An IOAM domain is configured from Alpha to Gamma only,
which means not on the reverse path. When Gamma is the destination, Alpha
adds an IOAM option (Pre-allocated Trace) inside a Hop-by-hop and fills the
trace with its own IOAM data. Beta and Gamma also fill the trace. The IOAM
data integrity is checked on Gamma, by comparing with the pre-defined IOAM
configuration (see below).

    +-------------------+            +-------------------+
    |                   |            |                   |
    |    alpha netns    |            |    gamma netns    |
    |                   |            |                   |
    |  +-------------+  |            |  +-------------+  |
    |  |    veth0    |  |            |  |    veth0    |  |
    |  |  db01::2/64 |  |            |  |  db02::2/64 |  |
    |  +-------------+  |            |  +-------------+  |
    |         .         |            |         .         |
    +-------------------+            +-------------------+
              .                                .
              .                                .
              .                                .
    +----------------------------------------------------+
    |         .                                .         |
    |  +-------------+                  +-------------+  |
    |  |    veth0    |                  |    veth1    |  |
    |  |  db01::1/64 | ................ |  db02::1/64 |  |
    |  +-------------+                  +-------------+  |
    |                                                    |
    |                      beta netns                    |
    |                                                    |
    +--------------------------+-------------------------+

~~~~~~~~~~~~~~~~~~~~~~
| IOAM configuration |
~~~~~~~~~~~~~~~~~~~~~~

Alpha
+-----------------------------------------------------------+
| Type                | Value                               |
+-----------------------------------------------------------+
| Node ID             | 1                                   |
+-----------------------------------------------------------+
| Node Wide ID        | 11111111                            |
+-----------------------------------------------------------+
| Ingress ID          | 0xffff (default value)              |
+-----------------------------------------------------------+
| Ingress Wide ID     | 0xffffffff (default value)          |
+-----------------------------------------------------------+
| Egress ID           | 101                                 |
+-----------------------------------------------------------+
| Egress Wide ID      | 101101                              |
+-----------------------------------------------------------+
| Namespace Data      | 0xdeadbee0                          |
+-----------------------------------------------------------+
| Namespace Wide Data | 0xcafec0caf00dc0de                  |
+-----------------------------------------------------------+
| Schema ID           | 777                                 |
+-----------------------------------------------------------+
| Schema Data         | something that will be 4n-aligned   |
+-----------------------------------------------------------+

Note: When Gamma is the destination, Alpha adds an IOAM Pre-allocated Trace
      option inside a Hop-by-hop, where 164 bytes are pre-allocated for the
      trace, with 123 as the IOAM-Namespace and with 0xfff00200 as the trace
      type (= all available options at this time). As a result, and based on
      IOAM configurations here, only both Alpha and Beta should be capable of
      inserting their IOAM data while Gamma won't have enough space and will
      set the overflow bit.

Beta
+-----------------------------------------------------------+
| Type                | Value                               |
+-----------------------------------------------------------+
| Node ID             | 2                                   |
+-----------------------------------------------------------+
| Node Wide ID        | 22222222                            |
+-----------------------------------------------------------+
| Ingress ID          | 201                                 |
+-----------------------------------------------------------+
| Ingress Wide ID     | 201201                              |
+-----------------------------------------------------------+
| Egress ID           | 202                                 |
+-----------------------------------------------------------+
| Egress Wide ID      | 202202                              |
+-----------------------------------------------------------+
| Namespace Data      | 0xdeadbee1                          |
+-----------------------------------------------------------+
| Namespace Wide Data | 0xcafec0caf11dc0de                  |
+-----------------------------------------------------------+
| Schema ID           | 0xffffff (= None)                   |
+-----------------------------------------------------------+
| Schema Data         |                                     |
+-----------------------------------------------------------+

Gamma
+-----------------------------------------------------------+
| Type                | Value                               |
+-----------------------------------------------------------+
| Node ID             | 3                                   |
+-----------------------------------------------------------+
| Node Wide ID        | 33333333                            |
+-----------------------------------------------------------+
| Ingress ID          | 301                                 |
+-----------------------------------------------------------+
| Ingress Wide ID     | 301301                              |
+-----------------------------------------------------------+
| Egress ID           | 0xffff (default value)              |
+-----------------------------------------------------------+
| Egress Wide ID      | 0xffffffff (default value)          |
+-----------------------------------------------------------+
| Namespace Data      | 0xdeadbee2                          |
+-----------------------------------------------------------+
| Namespace Wide Data | 0xcafec0caf22dc0de                  |
+-----------------------------------------------------------+
| Schema ID           | 0xffffff (= None)                   |
+-----------------------------------------------------------+
| Schema Data         |                                     |
+-----------------------------------------------------------+

Signed-off-by: Justin Iurman <justin.iurman@uliege.be>
Signed-off-by: David S. Miller <davem@davemloft.net>