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Subject: Re: [PATCH net-next] net: ipv6: add IFLA_RA_MTU to expose mtu value
 in the RA message
To:     Rocco Yue <rocco.yue@mediatek.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@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, chao.song@mediatek.com,
        zhuoliang.zhang@mediatek.com
References: <20210729090206.11138-1-rocco.yue@mediatek.com>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <c4099beb-1c22-ac71-ae05-e3f9a8ab69e2@gmail.com>
Date:   Thu, 29 Jul 2021 08:41:17 -0600
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On 7/29/21 3:02 AM, Rocco Yue wrote:
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 4882e81514b6..ea6c872c5f2c 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -347,7 +347,7 @@ enum {
>  	 */
>  	IFLA_PARENT_DEV_NAME,
>  	IFLA_PARENT_DEV_BUS_NAME,
> -
> +	IFLA_RA_MTU,
>  	__IFLA_MAX
>  };
>  
> diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
> index 70603775fe91..3dbcf212b766 100644
> --- a/include/uapi/linux/ipv6.h
> +++ b/include/uapi/linux/ipv6.h
> @@ -190,6 +190,7 @@ enum {
>  	DEVCONF_NDISC_TCLASS,
>  	DEVCONF_RPL_SEG_ENABLED,
>  	DEVCONF_RA_DEFRTR_METRIC,
> +	DEVCONF_RA_MTU,
>  	DEVCONF_MAX
>  };
>  

you do not need both IFLA and DEVCONF. Drop the DEVCONF completely. IFLA
attribute can be used for both inspection and notification on change.