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=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=unavailable 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 2C701C4338F for ; Tue, 10 Aug 2021 12:35:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 09ED860F56 for ; Tue, 10 Aug 2021 12:35:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240611AbhHJMgE (ORCPT ); Tue, 10 Aug 2021 08:36:04 -0400 Received: from mailgw02.mediatek.com ([210.61.82.184]:47416 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S236886AbhHJMfz (ORCPT ); Tue, 10 Aug 2021 08:35:55 -0400 X-UUID: 6f4aa03e1f494d4284d2cd45b99e0a48-20210810 X-UUID: 6f4aa03e1f494d4284d2cd45b99e0a48-20210810 Received: from mtkcas06.mediatek.inc [(172.21.101.30)] by mailgw02.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 1365449332; Tue, 10 Aug 2021 20:35:30 +0800 Received: from mtkcas07.mediatek.inc (172.21.101.84) by mtkmbs05n1.mediatek.inc (172.21.101.15) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 10 Aug 2021 20:35:28 +0800 Received: from localhost.localdomain (10.15.20.246) by mtkcas07.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Tue, 10 Aug 2021 20:35:27 +0800 From: Rocco Yue To: David Ahern CC: "David S . Miller" , Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , Matthias Brugger , , , , , , , , Rocco Yue Subject: Re: [PATCH net-next v3] ipv6: add IFLA_INET6_RA_MTU to expose mtu value in the RA message Date: Tue, 10 Aug 2021 20:33:27 +0800 Message-ID: <20210810123327.15998-1-rocco.yue@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2021-08-09 at 16:43 -0600, David Ahern wrote: > On 8/9/21 8:01 AM, Rocco Yue wrote: > + >> #ifdef CONFIG_SYSCTL >> >> static int addrconf_sysctl_forward(struct ctl_table *ctl, int write, >> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c >> index c467c6419893..a04164cbd77f 100644 >> --- a/net/ipv6/ndisc.c >> +++ b/net/ipv6/ndisc.c >> @@ -1496,6 +1496,12 @@ static void ndisc_router_discovery(struct sk_buff *skb) >> memcpy(&n, ((u8 *)(ndopts.nd_opts_mtu+1))+2, sizeof(mtu)); >> mtu = ntohl(n); >> >> + if (in6_dev->ra_mtu != mtu) { >> + in6_dev->ra_mtu = mtu; >> + inet6_iframtu_notify(in6_dev); >> + ND_PRINTK(2, info, "update ra_mtu to %d\n", in6_dev->ra_mtu); >> + } >> + >> if (mtu < IPV6_MIN_MTU || mtu > skb->dev->mtu) { >> ND_PRINTK(2, warn, "RA: invalid mtu: %d\n", mtu); >> } else if (in6_dev->cnf.mtu6 != mtu) { > > Since this MTU is getting reported via af_info infrastructure, > rtmsg_ifinfo should be sufficient. > > From there use 'ip monitor' to make sure you are not generating multiple > notifications; you may only need this on the error path. Hi David, To avoid generating multiple notifications, I added a separate ramtu notify function in this patch, and I added RTNLGRP_IPV6_IFINFO nl_mgrp to the ipmonitor.c to verify this patch was as expected. I look at the rtmsg_ifinfo code, it should be appropriate and I will use it and verify it. But there's one thing, I'm sorry I didn't fully understand the meaning of this sentence "you may only need this on the error path". Honestly, I'm not sure what the error patch refers to, do you mean "if (mtu < IPV6_MIN_MTU || mtu > skb->dev->mtu)" ? Thanks Rocco