PACKET socket can retain its fanout membership through link down and up
and (obviously) leave a fanout while it is not RUNNING (link down).
However, socket was forbidden from joining a fanout while it was not
RUNNING.

This patch allows PACKET socket to join a fanout while not RUNNING.
Selftest psock_fanout is extended to test this scenario.
This is the only test that was performed.

This scenario was identified while studying DPDK pmd_af_packet_drv.
Since sockets are only created during initialization, there is no reason
to fail the initialization if a single link is temporarily down.

I hope it is not considered as breaking user space and that applications
are not designed to expect this failure.

Gur Stavi (4):
  af_packet: allow fanout_add when socket is not RUNNING
  selftests: net/psock_fanout: add loopback up/down toggle facility
  selftests: net/psock_fanout: restore loopback up/down state on exit
  selftests: net/psock_fanout: socket joins fanout when link is down

 net/packet/af_packet.c                     |  10 +-
 tools/testing/selftests/net/psock_fanout.c | 124 ++++++++++++++-------
 2 files changed, 90 insertions(+), 44 deletions(-)


base-commit: c824deb1a89755f70156b5cdaf569fca80698719
-- 
2.45.2