netdev - Re: [PATCH bpf-next v3 16/16] selftests/bpf: Tests for BPF_SK

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Date:   Wed, 8 Jul 2020 21:28:53 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jakub Sitnicki <jakub@...udflare.com>
Cc:     Lorenz Bauer <lmb@...udflare.com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH bpf-next v3 16/16] selftests/bpf: Tests for BPF_SK_LOOKUP
 attach point

On Thu, Jul 2, 2020 at 6:00 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
>
> On Thu, Jul 02, 2020 at 01:01 PM CEST, Lorenz Bauer wrote:
> > On Thu, 2 Jul 2020 at 10:24, Jakub Sitnicki <jakub@...udflare.com> wrote:
> >>
> >> Add tests to test_progs that exercise:
> >>
> >>  - attaching/detaching/querying programs to BPF_SK_LOOKUP hook,
> >>  - redirecting socket lookup to a socket selected by BPF program,
> >>  - failing a socket lookup on BPF program's request,
> >>  - error scenarios for selecting a socket from BPF program,
> >>  - accessing BPF program context,
> >>  - attaching and running multiple BPF programs.
> >>
> >> Run log:
> >> | # ./test_progs -n 68
> >> | #68/1 query lookup prog:OK
> >> | #68/2 TCP IPv4 redir port:OK
> >> | #68/3 TCP IPv4 redir addr:OK
> >> | #68/4 TCP IPv4 redir with reuseport:OK
> >> | #68/5 TCP IPv4 redir skip reuseport:OK
> >> | #68/6 TCP IPv6 redir port:OK
> >> | #68/7 TCP IPv6 redir addr:OK
> >> | #68/8 TCP IPv4->IPv6 redir port:OK
> >> | #68/9 TCP IPv6 redir with reuseport:OK
> >> | #68/10 TCP IPv6 redir skip reuseport:OK
> >> | #68/11 UDP IPv4 redir port:OK
> >> | #68/12 UDP IPv4 redir addr:OK
> >> | #68/13 UDP IPv4 redir with reuseport:OK
> >> | #68/14 UDP IPv4 redir skip reuseport:OK
> >> | #68/15 UDP IPv6 redir port:OK
> >> | #68/16 UDP IPv6 redir addr:OK
> >> | #68/17 UDP IPv4->IPv6 redir port:OK
> >> | #68/18 UDP IPv6 redir and reuseport:OK
> >> | #68/19 UDP IPv6 redir skip reuseport:OK
> >> | #68/20 TCP IPv4 drop on lookup:OK
> >> | #68/21 TCP IPv6 drop on lookup:OK
> >> | #68/22 UDP IPv4 drop on lookup:OK
> >> | #68/23 UDP IPv6 drop on lookup:OK
> >> | #68/24 TCP IPv4 drop on reuseport:OK
> >> | #68/25 TCP IPv6 drop on reuseport:OK
> >> | #68/26 UDP IPv4 drop on reuseport:OK
> >> | #68/27 TCP IPv6 drop on reuseport:OK
> >> | #68/28 sk_assign returns EEXIST:OK
> >> | #68/29 sk_assign honors F_REPLACE:OK
> >> | #68/30 access ctx->sk:OK
> >> | #68/31 sk_assign rejects TCP established:OK
> >> | #68/32 sk_assign rejects UDP connected:OK
> >> | #68/33 multi prog - pass, pass:OK
> >> | #68/34 multi prog - pass, inval:OK
> >> | #68/35 multi prog - inval, pass:OK
> >> | #68/36 multi prog - drop, drop:OK
> >> | #68/37 multi prog - pass, drop:OK
> >> | #68/38 multi prog - drop, pass:OK
> >> | #68/39 multi prog - drop, inval:OK
> >> | #68/40 multi prog - inval, drop:OK
> >> | #68/41 multi prog - pass, redir:OK
> >> | #68/42 multi prog - redir, pass:OK
> >> | #68/43 multi prog - drop, redir:OK
> >> | #68/44 multi prog - redir, drop:OK
> >> | #68/45 multi prog - inval, redir:OK
> >> | #68/46 multi prog - redir, inval:OK
> >> | #68/47 multi prog - redir, redir:OK
> >> | #68 sk_lookup:OK
> >> | Summary: 1/47 PASSED, 0 SKIPPED, 0 FAILED
> >>
> >> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
> >> ---
> >>
> >> Notes:
> >>     v3:
> >>     - Extend tests to cover new functionality in v3:
> >>       - multi-prog attachments (query, running, verdict precedence)
> >>       - socket selecting for the second time with bpf_sk_assign
> >>       - skipping over reuseport load-balancing
> >>
> >>     v2:
> >>      - Adjust for fields renames in struct bpf_sk_lookup.
> >>
> >>  .../selftests/bpf/prog_tests/sk_lookup.c      | 1353 +++++++++++++++++
> >>  .../selftests/bpf/progs/test_sk_lookup_kern.c |  399 +++++
> >>  2 files changed, 1752 insertions(+)
> >>  create mode 100644 tools/testing/selftests/bpf/prog_tests/sk_lookup.c
> >>  create mode 100644 tools/testing/selftests/bpf/progs/test_sk_lookup_kern.c
> >>
> >> diff --git a/tools/testing/selftests/bpf/prog_tests/sk_lookup.c b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
> >> new file mode 100644
> >> index 000000000000..2859dc7e65b0
> >> --- /dev/null
> >> +++ b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
>
> [...]
>

[...]

> >> +static void run_lookup_prog(const struct test *t)
> >> +{
> >> +       int client_fd, server_fds[MAX_SERVERS] = { -1 };
> >> +       struct bpf_link *lookup_link;
> >> +       int i, err;
> >> +
> >> +       lookup_link = attach_lookup_prog(t->lookup_prog);
> >> +       if (!lookup_link)
> >
> > Why doesn't this fail the test? Same for the other error paths in the
> > function, and the other helpers.
>
> I took the approach of placing CHECK_FAIL checks only right after the
> failure point. So a syscall or a call to libbpf.
>
> This way if I'm calling a helper, I know it already fails the test if
> anything goes wrong, and I can have less CHECK_FAILs peppered over the
> code.

Please prefere CHECK() over CHECK_FAIL(), unless you are making
hundreds of checks and it's extremely unlikely they will ever fail.
Using CHECK_FAIL makes even knowing where the test fails hard. CHECK()
leaves a trail, so it's easier to pinpoint what and why failed.


[...]