selftests: netfilter: nft_queue.sh: avoid flakes on debug kernels

Jakub reports test flakes on debug kernels:
 FAIL: test_udp_gro_ct: Expected software segmentation to occur, had 23 and 17

This test assumes that the kernels nfnetlink_queue module sees N GSO
packets, segments them into M skbs and queues them to userspace for
reinjection.

Hence, if M >= N, no segmentation occurred.

However, its possible that this happens:
- nfnetlink_queue gets GSO packet
- segments that into n skbs
- userspace buffer is full, kernel drops the segmented skbs

-> "toqueue" counter incremented by 1, "fromqueue" is unchanged.

If this happens often enough in a single run, M >= N check triggers
incorrectly.

To solve this, allow the nf_queue.c test program to set the FAIL_OPEN
flag so that the segmented skbs bypass the queueing step in the kernel
if the receive buffer is full.

Also, reduce number of sending socat instances, decrease their priority
and increase nice value for the nf_queue program itself to reduce the
probability of overruns happening in the first place.

Fixes: 59ecffa3995e ("selftests: netfilter: nft_queue.sh: add udp fraglist gro test case")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Closes: https://lore.kernel.org/netdev/20260218184114.0b405b72@kernel.org/
Signed-off-by: Florian Westphal <fw@strlen.de>
Link: https://patch.msgid.link/20260226161920.1205-1-fw@strlen.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions