selftests: drv-net: add checksum tests

Run tools/testing/selftest/net/csum.c as part of drv-net.
This binary covers multiple scenarios, based on arguments given,
for both IPv4 and IPv6:

- Accept UDP correct checksum
- Detect UDP invalid checksum
- Accept TCP correct checksum
- Detect TCP invalid checksum

- Transmit UDP: basic checksum offload
- Transmit UDP: zero checksum conversion

The test direction is reversed between receive and transmit tests, so
that the NIC under test is always the local machine.

In total this adds up to 12 testcases, with more to follow. For
conciseness, I replaced individual functions with a function factory.

Also detect hardware offload feature availability using Ethtool
netlink and skip tests when either feature is off. This need may be
common for offload feature tests and eventually deserving of a thin
wrapper in lib.py.

Missing are the PF_PACKET based send tests ('-P'). These use
virtio_net_hdr to program hardware checksum offload. Which requires
looking up the local MAC address and (harder) the MAC of the next hop.
I'll have to give it some though how to do that robustly and where
that code would belong.

Tested:

make -C tools/testing/selftests/ \
TARGETS="drivers/net drivers/net/hw" \
install INSTALL_PATH=/tmp/ksft
cd /tmp/ksft

sudo NETIF=ens4 REMOTE_TYPE=ssh \
REMOTE_ARGS="root@10.40.0.2" \
LOCAL_V4="10.40.0.1" \
REMOTE_V4="10.40.0.2" \
./run_kselftest.sh -t drivers/net/hw:csum.py

Signed-off-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240507154216.501111-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests: drv-net-hw: add test for memory allocation failures with page pool

Bugs in memory allocation failure paths are quite common.
Add a test exercising those paths based on qstat and page pool
failure hook.

Running on bnxt:

# ./drivers/net/hw/pp_alloc_fail.py
KTAP version 1
1..1
# ethtool -G change retval: success
ok 1 pp_alloc_fail.test_pp_alloc
# Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

I initially wrote this test to validate commit be43b7489a3c ("net/mlx5e:
RX, Fix page_pool allocation failure recovery for striding rq") but mlx5
still doesn't have qstat. So I run it on bnxt, and while bnxt survives
I found the problem fixed in commit 730117730709 ("eth: bnxt: fix counting
packets discarded due to OOM and netpoll").

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240429144426.743476-7-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests: drv-net-hw: support using Python from net hw tests

We created a separate directory for HW-only tests, recently.
Glue in the Python test library there, Python is a bit annoying
when it comes to using library code located "lower"
in the directory structure.

Reuse the Env class, but let tests require non-nsim setup.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240429144426.743476-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests: forwarding: Move several selftests

The tests in net/forwarding are generally expected to be HW-independent.
There are however several tests that, while not depending on any HW in
particular, nevertheless depend on being used on HW interfaces. Placing
these selftests to net/forwarding is confusing, because the selftest will
just report it can't be run on veth pairs. At the same time, placing them
to a particular driver's selftests subdirectory would be wrong.

Instead, add a new directory, drivers/net/hw, where these generic but HW
independent selftests should be placed. Move over several such tests
including one helper library.

Since typically these tests will not be expected to run, omit the directory
drivers/net/hw from the TARGETS list in selftests/Makefile. Retain a
Makefile in the new directory itself, so that a user can make -C into that
directory and act on those tests explicitly.

Cc: Roger Quadros <rogerq@kernel.org>
Cc: Tobias Waldekranz <tobias@waldekranz.com>
Cc: Danielle Ratson <danieller@nvidia.com>
Cc: Davide Caratti <dcaratti@redhat.com>
Cc: Johannes Nixdorf <jnixdorf-oss@avm.de>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Link: https://lore.kernel.org/r/e11dae1f62703059e9fc2240004288ac7cc15756.1711464583.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>