From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1294FC4338F for ; Mon, 2 Aug 2021 12:57:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0CF160F6D for ; Mon, 2 Aug 2021 12:57:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233761AbhHBM5Y (ORCPT ); Mon, 2 Aug 2021 08:57:24 -0400 Received: from mailgw01.mediatek.com ([60.244.123.138]:45230 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S233678AbhHBM5W (ORCPT ); Mon, 2 Aug 2021 08:57:22 -0400 X-UUID: be321d17faa848ce8adf61ad9d539a67-20210802 X-UUID: be321d17faa848ce8adf61ad9d539a67-20210802 Received: from mtkcas06.mediatek.inc [(172.21.101.30)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 1587694583; Mon, 02 Aug 2021 20:57:10 +0800 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs07n2.mediatek.inc (172.21.101.141) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 2 Aug 2021 20:57:08 +0800 Received: from localhost.localdomain (10.15.20.246) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Mon, 2 Aug 2021 20:57:07 +0800 From: Rocco Yue To: David Ahern CC: "David S . Miller" , Jakub Kicinski , Hideaki YOSHIFUJI , , , , , , , , Rocco Yue Subject: Re: [PATCH net-next v2] ipv6: add IFLA_INET6_RA_MTU to expose mtu value in the RA message Date: Mon, 2 Aug 2021 20:40:39 +0800 Message-ID: <20210802124039.13231-1-rocco.yue@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20210802031924.3256-1-rocco.yue@mediatek.com> References: <20210802031924.3256-1-rocco.yue@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, 2021-07-31 at 11:17 -0600, David Ahern wrote: On 7/30/21 7:52 PM, Rocco Yue wrote: > IFLA_INET6_RA_MTU set. You can set "reject_message" in the policy to > return a message that "IFLA_INET6_RA_MTU can not be set". Hi David, Regarding setting "reject_message" in the policy, after reviewing the code, I fell that it is unnecessary, because the cost of implementing it seems to be a bit high, which requires modifying the function interface. The reasons is as follows: The parameter "struct netlink_ext_ack *extack" is not exposed in the function inet6_validate_link_af(), and the last argument when calling nla_parse_nested_deprecated() is NULL, which makes the user space not notified even if reject_message is set. static int inet6_validate_link_af(...) { ... err = nla_parse_nested_deprecated(tb, IFLA_INET6_MAX, nla, inet6_af_policy, NULL); ... } Only when extack is not NULL, reject_message is valid. static int validate_nla(...) { ... switch (pt->type) { case NLA_REJECT: if (extack && pt->reject_message) { NL_SET_BAD_ATTR(extack, nla); extack->_msg = pt->reject_message; return -EINVAL; } err = -EINVAL; goto out_err; ... } Thanks Rocco