netdev - Re: [PATCH net-next v3] net/ipv6: Introduce accept_unsolicited_na knob to implement router-side changes for RFC9131

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Date:   Wed, 13 Apr 2022 15:03:13 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Ahern <dsahern@...nel.org>, Arun Ajith S <aajith@...sta.com>,
        netdev@...r.kernel.org
Cc:     davem@...emloft.net, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, yoshfuji@...ux-ipv6.org,
        kuba@...nel.org, pabeni@...hat.com, corbet@....net,
        prestwoj@...il.com, gilligan@...sta.com, noureddine@...sta.com,
        gk@...sta.com
Subject: Re: [PATCH net-next v3] net/ipv6: Introduce accept_unsolicited_na
 knob to implement router-side changes for RFC9131


On 4/13/22 15:00, David Ahern wrote:
> On 4/13/22 3:22 PM, Eric Dumazet wrote:
>> On 4/13/22 07:34, Arun Ajith S wrote:
>>> Add a new neighbour cache entry in STALE state for routers on receiving
>>> an unsolicited (gratuitous) neighbour advertisement with
>>> target link-layer-address option specified.
>>> This is similar to the arp_accept configuration for IPv4.
>>> A new sysctl endpoint is created to turn on this behaviour:
>>> /proc/sys/net/ipv6/conf/interface/accept_unsolicited_na.
>>
>> Do we really need to expose this to /proc/sys, for every interface added
>> in the host ?
>>
>> /proc files creations/deletion cost a lot in environments
>> adding/deleting netns very often.
> agree with the general intent (along with the increasing memory costs).
> I do think this case should be done as a /proc/sys entry for consistency
> with both ARP and existing related NA settings.
>
>> I would prefer using NETLINK attributes, a single recvmsg() syscall can
>> fetch/set hundreds of them.
> What do you have in mind here? A link attribute managed through `ip link
> set`?


Yes, something like that, if this is a netdevice/link attribute.