Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
Date:   Fri, 30 Jun 2023 13:51:25 +0200
From:   Stefan Agner <stefan@agner.ch>
To:     Eric Dumazet <edumazet@google.com>
Cc:     davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org,
        pabeni@redhat.com, netdev@vger.kernel.org,
        john.carr@unrouted.co.uk, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] ipv6: add option to explicitly enable reachability
 test
In-Reply-To: <CANn89iKxcqDO3-LyuroUkFUfG2dtZOLE4n2UJQ3y-ft5BRm30g@mail.gmail.com>
References: <b9182b02829b158d55acc53a0bcec1ed667b2668.1680000784.git.stefan@agner.ch>
 <CANn89iKxcqDO3-LyuroUkFUfG2dtZOLE4n2UJQ3y-ft5BRm30g@mail.gmail.com>
Message-ID: <f2b8dc05f1c73c0f0625a695b25c2886@agner.ch>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

Hi Eric,

On 2023-03-28 19:54, Eric Dumazet wrote:
> On Tue, Mar 28, 2023 at 5:39 PM Stefan Agner <stefan@agner.ch> wrote:
>>
>> Systems which act as host as well as router might prefer the host
>> behavior. Currently the kernel does not allow to use IPv6 forwarding
>> globally and at the same time use route reachability probing.
>>
>> Add a compile time flag to enable route reachability probe in any
>> case.
>>
>> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> ---
>> My use case is a OpenThread device which at the same time can also act as a
>> client communicating with Thread devices. Thread Border routers use the Route
>> Information mechanism to publish routes with a lifetime of up to 1800s. If
>> one of the Thread Border router goes offline, the lack of reachability probing
>> currenlty leads to outages of up to 30 minutes.
>>
>> Not sure if the chosen method is acceptable. Maybe a runtime flag is preferred?
> 
> I guess so. Because distros would have to choose a compile option.
> 
> Not a new sysfs, only an IFLA_INET6_REACHABILITY_PROBE ?
>

Wouldn't that be a per interface config? From what I can tell currently
the reachability probing is disabled when IPv6 forwarding is enabled on
a global level only. So I'd need something which disables that behavior
on a global only as well.

--
Stefan