Instead of returning an error call the ioctl() handler of the interface

when we get request that we cannot handle ourself. This allows userland
to reach the ATM interfaces for ioctls.

sys/netnatm/natm.c

@@ -381,9 +381,12 @@ natm_usr_control(struct socket *so, u_long cmd, caddr_t arg,
 	    else
 		npcb->npcb_flags &= ~(NPCB_RAW);
 	}
+    } else {
+        splx(s);
+	if (ifp == NULL || ifp->if_ioctl == NULL)
+		return (EOPNOTSUPP);
+	return ((*ifp->if_ioctl)(ifp, cmd, arg));
     }
-    else
-	error = EOPNOTSUPP;
 
  out:
     splx(s);