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

[Kuniyuki Iwashima <kuniyu@amazon.co.jp>]

From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Fri, 30 Jul 2021 12:34:43 -0700
> 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

I'll use ASSERT_PTR_OK().


> 
> > +                 "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.

I'll make the two ternary operations of `sk->sk_socket ?` on single lines.

Thanks for your review!


> 
> > +                      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