DAOS-14219 dfs: checker should not follow symlinks (#13625)

The DFS checker should mark the symlink oid and not dereference the
symlink value. the value can be invalid anyway and if a valid path in
the container, it would be reachable from the hardlink path.

Signed-off-by: Mohamad Chaarawi <mohamad.chaarawi@intel.com>

src/client/dfs/dfs.c

@@ -6591,7 +6591,7 @@ oit_mark_cb(dfs_t *dfs, dfs_obj_t *parent, const char name[], void *args)
 	}
 
 	/** open the entry name and get the oid */
-	rc = dfs_lookup_rel(dfs, parent, name, O_RDONLY, &obj, NULL, NULL);
+	rc = dfs_lookup_rel(dfs, parent, name, O_RDONLY | O_NOFOLLOW, &obj, NULL, NULL);
 	if (rc) {
 		D_ERROR("dfs_lookup_rel() of %s failed: %d\n", name, rc);
 		return rc;

src/tests/suite/dfs_unit_test.c

@@ -2432,7 +2432,7 @@ dfs_test_checker(void **state)
 	test_arg_t		*arg = *state;
 	dfs_t			*dfs;
 	int			nr = 100, i;
-	dfs_obj_t		*root, *lf;
+	dfs_obj_t               *root, *lf, *sym;
 	daos_obj_id_t		root_oid;
 	daos_handle_t		root_oh;
 	daos_handle_t		coh;
@@ -2503,6 +2503,12 @@ dfs_test_checker(void **state)
 		assert_int_equal(rc, 0);
 	}
 
+	/** create a symlink with a non-existent target in the container */
+	rc = dfs_open(dfs, NULL, "SL1", S_IFLNK | S_IWUSR | S_IRUSR, O_RDWR | O_CREAT | O_EXCL, 0,
+		      0, "/usr/local", &sym);
+	assert_int_equal(rc, 0);
+	rc = dfs_release(sym);
+
 	rc = dfs_disconnect(dfs);
 	assert_int_equal(rc, 0);
 	/** have to call fini to release the cached container handle for the checker to work */