[PATCH 5/5] bpf: sockmap, sockhash: test looking up fds

[Lorenz Bauer]

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@xxxxxxxxxxxxxx>
---
 .../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");
+
+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 */
-- 
2.20.1