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Miller" , Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , Matthias Brugger , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, rocco.yue@gmail.com, chao.song@mediatek.com, zhuoliang.zhang@mediatek.com References: <20210810123327.15998-1-rocco.yue@mediatek.com> From: David Ahern Message-ID: <25dcf6e8-cdd6-6339-f499-5c3100a7d8c4@gmail.com> Date: Wed, 11 Aug 2021 07:56:59 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210810123327.15998-1-rocco.yue@mediatek.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/10/21 6:33 AM, Rocco Yue wrote: > 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)" ? > looks like nothing under: if (ndopts.nd_opts_mtu && in6_dev->cnf.accept_ra_mtu) { } is going to send a link notification so you can just replace inet6_iframtu_notify with rtmsg_ifinfo in your proposed change.