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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>
Cc:     "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>,
        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: <7087f518-f86e-58fb-6f32-a7cda77fb065@gmail.com>
 <20210602031502.31600-1-rocco.yue@mediatek.com>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <05efe271-72f8-bc77-8869-ae4685af5ea4@gmail.com>
Date:   Tue, 1 Jun 2021 22:20:03 -0600
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On 6/1/21 9:15 PM, Rocco Yue wrote:
> On Tue, 2021-06-01 at 18:38 -0600, David Ahern wrote:
> 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.
> 
> Thanks for your review and advice.
> Do you mean that I should keep the ra_mtu proc and add an another extra netlink msg?
> Or only use netlink msg instead of ra_mtu proc?
> I will do it.
> 

I meant DEVCONF and notification to userspace was good, but using an
IFLA attribute and no proc/sys file is better.