This series extends the iou-zcrx selftests to be multithreaded while
preserving existing single-threaded tests.

Patches 1 and 2 are prep fixes/cleanups. Patch 3 refactors the server's
global state. Patches 4 and 5 add the multithreaded client and server.
Finally, patch 6 adds the python side multithreaded test case.

Changes since v6:
- moving listen() after workers have registered their zcrx ifqs
  (Sashiko, Paolo, Bobby)
- worker verifies its own connections received the fully payload (to
  deal with the 0 connection per worker case passing (Sashiko, Paolo)

v6: https://lore.kernel.org/all/20260831-iou-zcrx-v6-0-02d1d012f0fd@fastmail.com/
v5: https://lore.kernel.org/all/20260814012348.46958-1-juanlu@fastmail.com/
v4: https://lore.kernel.org/netdev/20260729221825.42773-1-juanlu@fastmail.com/
v3: https://lore.kernel.org/netdev/20260722203950.58550-1-juanlu@fastmail.com/
v2: https://lore.kernel.org/netdev/cover.1776444379.git.juanlu@fastmail.com/
v1: https://lore.kernel.org/netdev/20260408163816.2760-1-juanlu@fastmail.com/

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Juanlu Herrero <juanlu@fastmail.com>
---
Juanlu Herrero (6):
      selftests: net: fix get_refill_ring_size() to use its local variable
      selftests: net: remove unused variable in process_recvzc()
      selftests: net: refactor server state into struct thread_ctx
      selftests: net: add multithread client support to iou-zcrx
      selftests: net: add multithread server support to iou-zcrx
      selftests: net: add rss_multiqueue test variant to iou-zcrx

 tools/testing/selftests/drivers/net/hw/Makefile    |   7 +-
 tools/testing/selftests/drivers/net/hw/iou-zcrx.c  | 422 +++++++++++++++------
 tools/testing/selftests/drivers/net/hw/iou-zcrx.py |  50 ++-
 3 files changed, 347 insertions(+), 132 deletions(-)
---
base-commit: 548b86839f7fb819a4d6c83b71c73ec378d24275
change-id: 20260817-iou-zcrx-e8e46108a0bc

Best regards,
--  
Juanlu Herrero