netdev - Re: [PATCH net-next v4] ipv6: add IFLA_INET6_RA_MTU to expose mtu value in the RA message

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Date:   Tue, 17 Aug 2021 09:05:36 -0600
From:   David Ahern <dsahern@...il.com>
To:     Rocco Yue <rocco.yue@...iatek.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, rocco.yue@...il.com,
        chao.song@...iatek.com, zhuoliang.zhang@...iatek.com
Subject: Re: [PATCH net-next v4] ipv6: add IFLA_INET6_RA_MTU to expose mtu
 value in the RA message

On 8/17/21 1:26 AM, Rocco Yue wrote:
> @@ -1496,6 +1490,11 @@ 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;
> +			send_ifinfo_notify = true;
> +		}
> +
>  		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) {


If an RA no longer carries an MTU or if accept_ra_mtu is reset, then
in6_dev->ra_mtu should be reset to 0 right?

rest of the change looks good to me.