The combination of checksum offload disabled (that causes software GSO)
and a debug kernel is inherently slow. Depending on the CPU power and
load, RTT may increase, limiting sk_pacing_rate, so tcp_tso_autosize
caps SKBs at around 40 segments, and zero BIG TCP packets are produced.
Increase sysctl net.ipv4.tcp_min_tso_segs and set a bigger initial value
of CWND in these configurations to force BIG TCP.
Fixes: 5cb53743e1 ("selftests: net: Add a test for BIG TCP in UDP tunnels")
Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260822120308.1165200-5-alice.kernel@fastmail.im
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
With checksum offload disabled, much fewer BIG TCP packets are generated
due to overall loss of throughput. Use a separate threshold in these
tests, which is 1/10 of the threshold set for the rest of tests.
Fixes: 5cb53743e1 ("selftests: net: Add a test for BIG TCP in UDP tunnels")
Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260822120308.1165200-4-alice.kernel@fastmail.im
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Debug kernels on upstream CI runners run slower and generate fewer BIG
TCP packets, making the test flaky on upstream CI runners. Lower the
default threshold for those kernels.
Fixes: 5cb53743e1 ("selftests: net: Add a test for BIG TCP in UDP tunnels")
Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260822120308.1165200-3-alice.kernel@fastmail.im
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Use wait_local_port_listen after starting netserver in
big_tcp_tunnels.sh to ensure it's listening when the test starts.
Fixes: 5cb53743e1 ("selftests: net: Add a test for BIG TCP in UDP tunnels")
Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260822120308.1165200-2-alice.kernel@fastmail.im
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The test sets up VXLAN and GENEVE tunnels over IPv4 and IPv6 and runs
IPv4 and IPv6 traffic through them with BIG TCP enabled. It checks that
a non-negligible amount of big aggregated packets are seen by setting up
iptables counters.
Check the number of packets on both TX and RX sides to verify that GSO
packets are valid and not dropped. Capture on the lower netdev (veth),
when checksum offload is on, to verify that encapsulated BIG TCP packets
can get to their destination. In the test with TX checksum offload off,
software GSO splits aggregated VXLAN packets before passing them to
veth, so capture inside the tunnel instead to check that the big packets
are not dropped.
Check that the amount of SACKs is negligible. On unsupported kernels,
some amount of broken GSO packets bigger than 65536 bytes can be
produced in VXLAN tunnels, but they don't reach the destination. Seeing
TCP SACKs is a sign that such packets could have been dropped (in such
cases, the amount of SACKs is a few times bigger than the number of
attempts to send BIG TCP packets).
Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Link: https://patch.msgid.link/20260710134242.216538-10-alice.kernel@fastmail.im
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
