Re: [PATCH net-next] selftests: drv-net: devmem: set reuseaddr on the sender's source port
From: Breno Leitao <leitao@debian.org>
Date: 2026-09-09 09:19:32
Also in:
linux-kselftest
On Tue, Sep 08, 2026 at 11:34:20AM -0700, Jakub Kicinski wrote:
devmem.py fails on the HW runners with:
CMD[remote]: dd if=/dev/zero bs=512 count=1 2>/dev/null | socat -b 512 \
-u - TCP6:[fd00:2::1]:50051,bind=[fd00:2::2]:50051,nodelay
STDERR: socat[41018] W bind(5, {AF=10 [fd00:2::2]:50051}, 28): \
Address already in use
ncdevmem installs a 5-tuple flow rule which matches the source port, so
socat has to bind it explicitly. The port comes from rand_port(), which
checks availability on the DUT - but we bind on the remote...
That said the failure rate seems to high to be random collisions
(~2% per sub-test). It's probably TIME_WAIT sockets on the remote,
run_rx_hds() alone creates 12 of them.
Set reuseaddr so a TIME_WAIT socket does not fail the bind. Collisions
with a live socket are still possible, we'll see if they are frequent
enough to care.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>Reviewed-by: Breno Leitao <leitao@debian.org>
quoted hunk ↗ jump to hunk
--- a/tools/testing/selftests/drivers/net/hw/devmem_lib.py +++ b/tools/testing/selftests/drivers/net/hw/devmem_lib.py@@ -201,7 +201,7 @@ def ncdevmem_rx(cfg, port, verify=True, fail_on_linear=False, flow_steer=False, else: addr = cfg.baddr - suffix = f",bind={cfg.remote_baddr}:{port}" + suffix = f",bind={cfg.remote_baddr}:{port},reuseaddr"
socat_listen(), used by run_tx() and run_tx_chunks(), still builds without reuseaddr. From my reading, I understand we don't need it given ncdevmem does the active close on those tests. Leaving it alone seems right.