selftests/bpf: Update bpf_clone_redirect expected return code

Commit 151e887d8ff9 ("veth: Fixing transmit return status for dropped
packets") started propagating proper NET_XMIT_DROP error to the caller
which means it's now possible to get positive error code when calling
bpf_clone_redirect() in this particular test. Update the test to reflect
that.

Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230911194731.286342-2-sdf@google.com

selftests/bpf: move SYS() macro into the test_progs.h

A lot of tests defined SYS() macro to run system calls with goto label.
Let's move this macro to test_progs.h and add configurable
"goto_label" as the first arg.

Suggested-by: Martin KaFai Lau <martin.lau@linux.dev>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20230224061343.506571-2-liuhangbin@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

selftests/bpf: Remove serial from tests using {open,close}_netns

After removing the mount/umount dance from {open,close}_netns()
in the pervious patch, "serial_" can be removed from
the tests using {open,close}_netns().

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20221129070900.3142427-7-martin.lau@linux.dev

selftests/bpf: Mount debugfs in setns_by_fd

Jiri reports broken test_progs after recent commit 68f8e3d4b916
("selftests/bpf: Make sure zero-len skbs aren't redirectable").
Apparently we don't remount debugfs when we switch back networking namespace.
Let's explicitly mount /sys/kernel/debug.

0: https://lore.kernel.org/bpf/63b85917-a2ea-8e35-620c-808560910819@meta.com/T/#ma66ca9c92e99eee0a25e40f422489b26ee0171c1

Fixes: a30338840fa5 ("selftests/bpf: Move open_netns() and close_netns() into network_helpers.c")
Reported-by: Jiri Olsa <olsajiri@gmail.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20221123200829.2226254-1-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Make sure zero-len skbs aren't redirectable

LWT_XMIT to test L3 case, TC to test L2 case.

v2:
- s/veth_ifindex/ipip_ifindex/ in two places (Martin)
- add comment about which condition triggers the rejection (Martin)

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20221121180340.1983627-2-sdf@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>