Merge branch 'bpf-xdp-offload-fixes'

Toke Høiland-Jørgensen says:

====================
This series restores the test_offload.py selftest to working order. It seems a
number of subtle behavioural changes have crept into various subsystems which
broke test_offload.py in a number of ways. Most of these are fairly benign
changes where small adjustments to the test script seems to be the best fix,
but one is an actual kernel bug that I've observed in the wild caused by a bad
interaction between xdp_attachment_flags_ok() and the rework of XDP program
handling in the core netdev code.

Patch 1 fixes the bug by removing xdp_attachment_flags_ok(), and the reminder of
the patches are adjustments to test_offload.py, including a new feature for
netdevsim to force a BPF verification fail. Please see the individual patches
for details.

Changelog:

v4:
  - Accidentally truncated the Fixes: hashes in patches 3/4 to 11 chars
v3:
  - Add Fixes: tags
v2:
  - Replace xdp_attachment_flags_ok() with a check in dev_xdp_attach()
  - Better packing of struct nsim_dev
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>