selftests/bpf: Add selftests for netkit

Add a bigger batch of test coverage to assert correct operation of
netkit devices and their BPF program management:

# ./test_progs -t tc_netkit
[...]
[ 1.166267] bpf_testmod: loading out-of-tree module taints kernel.
[ 1.166831] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
[ 1.270957] tsc: Refined TSC clocksource calibration: 3407.988 MHz
[ 1.272579] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fc932722, max_idle_ns: 440795381586 ns
[ 1.275336] clocksource: Switched to clocksource tsc
#257 tc_netkit_basic:OK
#258 tc_netkit_device:OK
#259 tc_netkit_multi_links:OK
#260 tc_netkit_multi_opts:OK
#261 tc_netkit_neigh_links:OK
Summary: 5/0 PASSED, 0 SKIPPED, 0 FAILED
[...]

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20231024214904.29825-8-daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

selftests/bpf: Make seen_tc* variable tests more robust

Martin reported that on his local dev machine the test_tc_chain_mixed() fails as
"test_tc_chain_mixed:FAIL:seen_tc5 unexpected seen_tc5: actual 1 != expected 0"
and others occasionally, too.

However, when running in a more isolated setup (qemu in particular), it works fine
for him. The reason is that there is a small race-window where seen_tc* could turn
into true for various test cases when there is background traffic, e.g. after the
asserts they often get reset. In such case when subsequent detach takes place,
unrelated background traffic could have already flipped the bool to true beforehand.

Add a small helper tc_skel_reset_all_seen() to reset all bools before we do the ping
test. At this point, everything is set up as expected and therefore no race can occur.
All tc_{opts,links} tests continue to pass after this change.

Reported-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20231006220655.1653-7-daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

selftests/bpf: Adapt assert_mprog_count to always expect 0 count

Simplify __assert_mprog_count() to remove the -ENOENT corner case as the
bpf_prog_query() now returns 0 when no bpf_mprog is attached. This also
allows to convert a few test cases from using raw __assert_mprog_count()
over to plain assert_mprog_count() helper.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20231006220655.1653-5-daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

selftests/bpf: Add mprog API tests for BPF tcx opts

Add a big batch of test coverage to assert all aspects of the tcx opts
attach, detach and query API:

# ./vmtest.sh -- ./test_progs -t tc_opts
[...]
#238 tc_opts_after:OK
#239 tc_opts_append:OK
#240 tc_opts_basic:OK
#241 tc_opts_before:OK
#242 tc_opts_chain_classic:OK
#243 tc_opts_demixed:OK
#244 tc_opts_detach:OK
#245 tc_opts_detach_after:OK
#246 tc_opts_detach_before:OK
#247 tc_opts_dev_cleanup:OK
#248 tc_opts_invalid:OK
#249 tc_opts_mixed:OK
#250 tc_opts_prepend:OK
#251 tc_opts_replace:OK
#252 tc_opts_revision:OK
Summary: 15/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20230719140858.13224-8-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>