server: Add an open_file() function to the object operations.
diff --git a/server/sock.c b/server/sock.c
index e8d6ef3..f1b7255 100644
--- a/server/sock.c
+++ b/server/sock.c
@@ -114,6 +114,7 @@
     sock_get_fd,                  /* get_fd */
     sock_map_access,              /* map_access */
     no_lookup_name,               /* lookup_name */
+    no_open_file,                 /* open_file */
     fd_close_handle,              /* close_handle */
     sock_destroy                  /* destroy */
 };