NHA_OIF
{ .type = NHA_OIF, .off = _OUT(nha_oif), .cb = snl_attr_get_uint32 },
nlattr_add_u32(nw, NHA_OIF, if_getindex(nh->nh_ifp));
{ .type = NHA_OIF, .off = _OUT(nha_oif), .cb = nlattr_get_ifp },