Re: [PATCH bpf-next 2/2] selftest/bpf: Implement sample UNIX domain socket iterator program.

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Thu, Jul 29, 2021 at 4:37 PM Kuniyuki Iwashima <kuniyu@amazon.co.jp> wrote:
>
> If there are no abstract sockets, this prog can output the same result
> compared to /proc/net/unix.
>
>   # cat /sys/fs/bpf/unix | head -n 2
>   Num       RefCount Protocol Flags    Type St Inode Path
>   ffff9ab7122db000: 00000002 00000000 00010000 0001 01 10623 private/defer
>
>   # cat /proc/net/unix | head -n 2
>   Num       RefCount Protocol Flags    Type St Inode Path
>   ffff9ab7122db000: 00000002 00000000 00010000 0001 01 10623 private/defer
>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
> ---
>  .../selftests/bpf/prog_tests/bpf_iter.c       | 17 +++++
>  .../selftests/bpf/progs/bpf_iter_unix.c       | 75 +++++++++++++++++++
>  2 files changed, 92 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_unix.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> index 1f1aade56504..4746bac68d36 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> @@ -13,6 +13,7 @@
>  #include "bpf_iter_tcp6.skel.h"
>  #include "bpf_iter_udp4.skel.h"
>  #include "bpf_iter_udp6.skel.h"
> +#include "bpf_iter_unix.skel.h"
>  #include "bpf_iter_test_kern1.skel.h"
>  #include "bpf_iter_test_kern2.skel.h"
>  #include "bpf_iter_test_kern3.skel.h"
> @@ -313,6 +314,20 @@ static void test_udp6(void)
>         bpf_iter_udp6__destroy(skel);
>  }
>
> +static void test_unix(void)
> +{
> +       struct bpf_iter_unix *skel;
> +
> +       skel = bpf_iter_unix__open_and_load();
> +       if (CHECK(!skel, "bpf_iter_unix__open_and_load",

please use new ASSERT_PTR_OK() macro instead

> +                 "skeleton open_and_load failed\n"))
> +               return;
> +
> +       do_dummy_read(skel->progs.dump_unix);
> +
> +       bpf_iter_unix__destroy(skel);
> +}
> +
>  /* The expected string is less than 16 bytes */
>  static int do_read_with_fd(int iter_fd, const char *expected,
>                            bool read_one_char)
> @@ -1255,6 +1270,8 @@ void test_bpf_iter(void)
>                 test_udp4();
>         if (test__start_subtest("udp6"))
>                 test_udp6();
> +       if (test__start_subtest("unix"))
> +               test_unix();
>         if (test__start_subtest("anon"))
>                 test_anon_iter(false);
>         if (test__start_subtest("anon-read-one-char"))
> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_unix.c b/tools/testing/selftests/bpf/progs/bpf_iter_unix.c
> new file mode 100644
> index 000000000000..285ec2f7944d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_unix.c
> @@ -0,0 +1,75 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright Amazon.com Inc. or its affiliates. */
> +#include "bpf_iter.h"
> +#include "bpf_tracing_net.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_endian.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#define __SO_ACCEPTCON         (1 << 16)
> +#define UNIX_HASH_SIZE         256
> +#define UNIX_ABSTRACT(unix_sk) (unix_sk->addr->hash < UNIX_HASH_SIZE)
> +
> +static long sock_i_ino(const struct sock *sk)
> +{
> +       const struct socket *sk_socket = sk->sk_socket;
> +       const struct inode *inode;
> +       unsigned long ino;
> +
> +       if (!sk_socket)
> +               return 0;
> +
> +       inode = &container_of(sk_socket, struct socket_alloc, socket)->vfs_inode;
> +       bpf_probe_read_kernel(&ino, sizeof(ino), &inode->i_ino);
> +       return ino;
> +}
> +
> +SEC("iter/unix")
> +int dump_unix(struct bpf_iter__unix *ctx)
> +{
> +       struct unix_sock *unix_sk = ctx->unix_sk;
> +       struct sock *sk = (struct sock *)unix_sk;
> +       struct seq_file *seq;
> +       __u32 seq_num;
> +
> +       if (!unix_sk)
> +               return 0;
> +
> +       seq = ctx->meta->seq;
> +       seq_num = ctx->meta->seq_num;
> +       if (seq_num == 0)
> +               BPF_SEQ_PRINTF(seq, "Num       RefCount Protocol Flags    "
> +                              "Type St Inode Path\n");
> +
> +       BPF_SEQ_PRINTF(seq, "%pK: %08X %08X %08X %04X %02X %5lu",
> +                      unix_sk,
> +                      sk->sk_refcnt.refs.counter,
> +                      0,
> +                      sk->sk_state == TCP_LISTEN ? __SO_ACCEPTCON : 0,
> +                      sk->sk_type,
> +                      sk->sk_socket ?
> +                      (sk->sk_state == TCP_ESTABLISHED ?
> +                       SS_CONNECTED : SS_UNCONNECTED) :
> +                      (sk->sk_state == TCP_ESTABLISHED ?
> +                       SS_CONNECTING : SS_DISCONNECTING),

nit: I'd keep these ternary operators on a single line for
readability. Same for header PRINTF above.

> +                      sock_i_ino(sk));
> +
> +       if (unix_sk->addr) {
> +               if (UNIX_ABSTRACT(unix_sk))
> +                       /* Abstract UNIX domain socket can contain '\0' in
> +                        * the path, and it should be escaped.  However, it
> +                        * requires loops and the BPF verifier rejects it.
> +                        * So here, print only the escaped first byte to
> +                        * indicate it is an abstract UNIX domain socket.
> +                        * (See: unix_seq_show() and commit e7947ea770d0d)
> +                        */
> +                       BPF_SEQ_PRINTF(seq, " @");
> +               else
> +                       BPF_SEQ_PRINTF(seq, " %s", unix_sk->addr->name->sun_path);
> +       }
> +
> +       BPF_SEQ_PRINTF(seq, "\n");
> +
> +       return 0;
> +}
> --
> 2.30.2
>