PF_MET_OFFSET
snl_add_msg_attr_u8(nw, PF_MET_OFFSET, me->offset);
{ .type = PF_MET_OFFSET, .off = _OUT(offset), .cb = snl_attr_get_uint8 },
{ .type = PF_MET_OFFSET, .off = _OUT(offset), .cb = nlattr_get_uint8 },
nlattr_add_u8(nw, PF_MET_OFFSET, m->offset);