Add a packetdrill test for an in-sequence data segment carrying an
excessively old ACK.
Verify that the segment falls through from the TCP fast path to the slow
path, where the existing ACK validation rejects it and sends a challenge
ACK. The payload is not accepted and RCV.NXT remains unchanged.
Based on the reproducer from Commit 3d501dd326
("tcp: do not accept ACK of bytes we never sent").
Signed-off-by: Inbal Schussheim <inbal.lipshtat@mail.huji.ac.il>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260914090408.1435080-3-inbal.lipshtat@mail.huji.ac.il
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
d841cd7513