On Wed, 11 Mar 2020 at 13:52, Jakub Sitnicki jakub@cloudflare.com wrote:

On Tue, Mar 10, 2020 at 06:47 PM CET, Lorenz Bauer wrote:

...

Make sure that looking up an element from the map succeeds, and that the fd is valid by using it an fcntl call.

Signed-off-by: Lorenz Bauer lmb@cloudflare.com

.../selftests/bpf/prog_tests/sockmap_listen.c | 26 ++++++++++++++----- 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c index 52aa468bdccd..929e1e77ecc6 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c @@ -453,7 +453,7 @@ static void test_lookup_after_delete(int family, int sotype, int mapfd) xclose(s); }

-static void test_lookup_32_bit_value(int family, int sotype, int mapfd) +static void test_lookup_fd(int family, int sotype, int mapfd) { u32 key, value32; int err, s; @@ -466,7 +466,7 @@ static void test_lookup_32_bit_value(int family, int sotype, int mapfd) sizeof(value32), 1, 0); if (mapfd < 0) { FAIL_ERRNO("map_create");

•         goto close;
  

•         goto close_sock;
  }
  
  key = 0;
  

@@ -475,11 +475,25 @@ static void test_lookup_32_bit_value(int family, int sotype, int mapfd)

  errno = 0;
  err = bpf_map_lookup_elem(mapfd, &key, &value32);

• if (!err || errno != ENOSPC)
  

•         FAIL_ERRNO("map_lookup: expected ENOSPC");
  

• if (err) {
  

•         FAIL_ERRNO("map_lookup");
  

•         goto close_map;
  

• }
  
  

• if ((int)value32 == s) {
  

•         FAIL("return value is identical");
  

•         goto close;
  

• }
  

• err = fcntl(value32, F_GETFD);
  

• if (err == -1)
  

•         FAIL_ERRNO("fcntl");
  

I would call getsockopt()/getsockname() to assert that the FD lookup succeeded. We want to know not only that it's an FD (-EBADFD case), but also that it's associated with a socket (-ENOTSOCK).

We can go even further, and compare socket cookies to ensure we got an FD for the expected socket.

Good idea, thanks!

Also, I'm wondering if we could keep the -ENOSPC case test-covered by temporarily dropping NET_ADMIN capability.

You mean EPERM? ENOSPC isn't reachable, since the map can only be created with a map_value of 4 or 8.

...

+close:

• xclose(value32);
  

+close_map: xclose(mapfd); -close: +close_sock: xclose(s); }

@@ -1456,7 +1470,7 @@ static void test_ops(struct test_sockmap_listen *skel, struct bpf_map *map, /* lookup */ TEST(test_lookup_after_insert), TEST(test_lookup_after_delete),

•         TEST(test_lookup_32_bit_value),
  

•         TEST(test_lookup_fd),
          /* update */
          TEST(test_update_existing),
          /* races with insert/delete */