Merge branch 'selftests-net-add-netkit-container-env-and-test'

David Wei says:

====================
selftests/net: add netkit container env and test

Add a new Python selftest env NetDrvContEnv that sets up a pair of
netkit netdevs, with one inside of a netns, and a bpf prog that forwards
skbs from NETIF to the netkit inside the netns.

  NETIF           = "eth0"
  LOCAL_V6        = "2001:db8:1::1"
  REMOTE_V6       = "2001:db8:1::2"
  LOCAL_PREFIX_V6 = "2001:db8:2::0/64"

          +-----------------------------+        +------------------------------+
  dst     | INIT NS                     |        | TEST NS                      |
  2001:   | +---------------+           |        |                              |
  db8:2::2| | NETIF         |           |  bpf   |                              |
      +---|>| 2001:db8:1::1 |           |redirect| +-------------------------+  |
      |   | |               |-----------|--------|>| Netkit                  |  |
      |   | +---------------+           | _peer  | | nk_guest                |  |
      |   | +-------------+ Netkit pair |        | | fe80::2/64              |  |
      |   | | Netkit      |.............|........|>| 2001:db8:2::2/64        |  |
      |   | | nk_host     |             |        | +-------------------------+  |
      |   | | fe80::1/64  |             |        |                              |
      |   | +-------------+             |        | route:                       |
      |   |                             |        |   default                    |
      |   | route:                      |        |     via fe80::1 dev nk_guest |
      |   |   2001:db8:2::2/128         |        +------------------------------+
      |   |     via fe80::2 dev nk_host |
      |   +-----------------------------+
      |
      |   +---------------+
      |   | REMOTE        |
      +---| 2001:db8:1::2 |
          +---------------+

I will use this series for queue leasing selftests. Include a basic ping
test in this series as demonstration.
====================

Link: https://patch.msgid.link/20260305181803.2912736-1-dw@davidwei.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>