netdev - Re: [PATCH v6 bpf-next 3/4] selftest/bpf: Implement sample UNIX domain socket iterator program.

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Date:   Sun, 15 Aug 2021 00:21:04 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.co.jp>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Benjamin Herrenschmidt <benh@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH v6 bpf-next 3/4] selftest/bpf: Implement sample UNIX
 domain socket iterator program.

On Fri, Aug 13, 2021 at 6:58 PM Kuniyuki Iwashima <kuniyu@...zon.co.jp> wrote:
>
> The iterator can output almost the same result compared to /proc/net/unix.
> The header line is aligned, and the Inode column uses "%8lu" because "%5lu"
> can be easily overflown.
>
>   # cat /sys/fs/bpf/unix
>   Num               RefCount Protocol Flags    Type St    Inode Path
>   ffff963c06689800: 00000002 00000000 00010000 0001 01    18697 private/defer
>   ffff963c7c979c00: 00000002 00000000 00000000 0001 01   598245 @Hello@...ld@
>
>   # cat /proc/net/unix
>   Num       RefCount Protocol Flags    Type St Inode Path
>   ffff963c06689800: 00000002 00000000 00010000 0001 01 18697 private/defer
>   ffff963c7c979c00: 00000002 00000000 00000000 0001 01 598245 @Hello@...ld@
>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
> Acked-by: Yonghong Song <yhs@...com>
> ---
>  .../selftests/bpf/prog_tests/bpf_iter.c       | 16 ++++
>  tools/testing/selftests/bpf/progs/bpf_iter.h  |  8 ++
>  .../selftests/bpf/progs/bpf_iter_unix.c       | 80 +++++++++++++++++++
>  .../selftests/bpf/progs/bpf_tracing_net.h     |  4 +
>  4 files changed, 108 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_unix.c

[...]

> +       if (unix_sk->addr) {
> +               if (!UNIX_ABSTRACT(unix_sk)) {
> +                       BPF_SEQ_PRINTF(seq, " %s", unix_sk->addr->name->sun_path);
> +               } else {
> +                       /* The name of the abstract UNIX domain socket starts
> +                        * with '\0' and can contain '\0'.  The null bytes
> +                        * should be escaped as done in unix_seq_show().
> +                        */
> +                       __u64 i, len;
> +
> +                       len = unix_sk->addr->len - sizeof(short);
> +
> +                       BPF_SEQ_PRINTF(seq, " @");
> +
> +                       for (i = 1; i < len; i++) {
> +                               /* unix_mkname() tests this upper bound. */
> +                               if (len >= sizeof(struct sockaddr_un))

I've changed this to (i >= sizeof(...)) which made more sense to me
than checking len multiple times. Both test_progs and
test_progs-no_alu32 passed on my local slightly older clang which
doesn't yet have Yonghong's fix, so I hope I didn't regress anything.

Applied to bpf-next.

> +                                       break;
> +
> +                               BPF_SEQ_PRINTF(seq, "%c",
> +                                              unix_sk->addr->name->sun_path[i] ?:
> +                                              '@');
> +                       }
> +               }
> +       }
> +
> +       BPF_SEQ_PRINTF(seq, "\n");
> +
> +       return 0;
> +}
> diff --git a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
> index 3af0998a0623..eef5646ddb19 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
> +++ b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
> @@ -5,6 +5,10 @@
>  #define AF_INET                        2
>  #define AF_INET6               10
>
> +#define __SO_ACCEPTCON         (1 << 16)
> +#define UNIX_HASH_SIZE         256
> +#define UNIX_ABSTRACT(unix_sk) (unix_sk->addr->hash < UNIX_HASH_SIZE)
> +
>  #define SOL_TCP                        6
>  #define TCP_CONGESTION         13
>  #define TCP_CA_NAME_MAX                16
> --
> 2.30.2
>