PFLOWNL_GET_ID
{ .type = PFLOWNL_GET_ID, .off = _OUT(id), .cb = snl_attr_get_int32 },
snl_add_msg_attr_s32(&nw, PFLOWNL_GET_ID, id);
{ .type = PFLOWNL_GET_ID, .off = _OUT(id), .cb = nlattr_get_uint32 },
nlattr_add_u32(nw, PFLOWNL_GET_ID, sc->sc_id);