selftests/bpf: improve netcnt test robustness

Change netcnt to demand at least 10K packets, as we frequently see some
stray packet arriving during the test in BPF CI. It seems more important
to make sure we haven't lost any packet than enforcing exact number of
packets.

Cc: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20230515204833.2832000-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Use bpf_num_possible_cpus() in per-cpu map allocations

bpf_map_value_size() uses num_possible_cpus() to determine map size, but
some of the tests only allocate enough memory for online cpus. This
results in out-of-bound writes in userspace during bpf(BPF_MAP_LOOKUP_ELEM)
syscalls in cases when number of online cpus is lower than the number of
possible cpus. Fix by switching from get_nprocs_conf() to
bpf_num_possible_cpus() when determining the number of processors in
these tests (test_progs/netcnt and test_cgroup_storage).

Signed-off-by: Artem Savkov <asavkov@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220406085408.339336-1-asavkov@redhat.com

selftests/bpf: Make netcnt selftests serial to avoid spurious failures

When running `./test_progs -j` test_netcnt fails with a very high
probability, undercounting number of packets received (9999 vs expected
10000). It seems to be conflicting with other cgroup/skb selftests. So
make it serial for now to make parallel mode more robust.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211103054113.2130582-1-andrii@kernel.org

selftests/bpf: Move netcnt test under test_progs

Rewrite to skel and ASSERT macros as well while we are at it.

v3:
- replace -f with -A to make it work with busybox ping.
-A is available on both busybox and iputils, from the man page:
On networks with low RTT this mode is essentially equivalent to
flood mode.

v2:
- don't check result of bpf_map__fd (Yonghong Song)
- remove from .gitignore (Andrii Nakryiko)
- move ping_command into network_helpers (Andrii Nakryiko)
- remove assert() (Andrii Nakryiko)

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210804205524.3748709-1-sdf@google.com