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Subject: Re: [PATCH] ipv6: create ra_mtu proc file to only record mtu in RA
To:     Rocco Yue <rocco.yue@mediatek.com>,
        "David S . Miller" <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com,
        rocco.yue@gmail.com
References: <20210601091619.19372-1-rocco.yue@mediatek.com>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <7087f518-f86e-58fb-6f32-a7cda77fb065@gmail.com>
Date:   Tue, 1 Jun 2021 18:38:24 -0600
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On 6/1/21 3:16 AM, Rocco Yue wrote:
> For this patch set, if RA message carries the mtu option,
> "proc/sys/net/ipv6/conf/<iface>/ra_mtu" will be updated to the
> mtu value carried in the last RA message received, and ra_mtu
> is an independent proc file, which is not affected by the update
> of interface mtu value.

I am not a fan of more /proc/sys files.

You are adding it to devconf which is good. You can add another link
attribute, e.g., IFLA_RA_MTU, and have it returned on link queries.

Make sure the attribute can not be sent in a NEWLINK or SETLINK request;
it should be read-only for GETLINK.