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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> <25dcf6e8-cdd6-6339-f499-5c3100a7d8c4@gmail.com> Message-ID: <4624cc10-1fc8-12cd-e9e1-9585f5b496a0@gmail.com> Date: Wed, 11 Aug 2021 12:05:54 -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: <25dcf6e8-cdd6-6339-f499-5c3100a7d8c4@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/11/21 7:56 AM, David Ahern wrote: > 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. > Taking a deeper dive on the code, you do not need to call rtmsg_ifinfo. Instead, the existing: /* * Send a notify if RA changed managed/otherconf flags or timer settings */ if (send_ifinfo_notify) inet6_ifinfo_notify(RTM_NEWLINK, in6_dev); is called too early. For one the RA can change the MTU and that is done after this notify. I think if you moved this down to the out: out: /* * Send a notify if RA changed managed/otherconf flags or timer settings */ if (send_ifinfo_notify) inet6_ifinfo_notify(RTM_NEWLINK, in6_dev); and then set send_ifinfo_notify when the mtu is *changed* by the RA you should be good.