selftests/tc-testing: Add DualPI2 GSO backlog accounting test

Add a regression test for DualPI2 GSO backlog accounting when it is
used as a child qdisc of QFQ.

The test sends one UDP GSO datagram through a QFQ class with DualPI2 as
the leaf qdisc. DualPI2 splits the skb into two segments. After the
traffic drains, both QFQ and DualPI2 must report zero backlog and zero
qlen.

On kernels with the broken accounting, QFQ can keep a stale non-zero
qlen after all real packets have been dequeued.

Signed-off-by: Xingquan Liu <b1n@b1n.io>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Link: https://patch.msgid.link/20260619151447.223640-2-b1n@b1n.io
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions