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 <redacted>
---
 .../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",

+                 "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),