netdev - Re: [PATCH net] ipv6: Reflect MTU changes on PMTU of exceptions for MTU-less routes

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Message-ID: <d955bd59-e8a7-4c6f-603e-eaa4174a815f@gmail.com>
Date:   Sun, 4 Mar 2018 18:11:41 -0700
From:   David Ahern <dsahern@...il.com>
To:     Stefano Brivio <sbrivio@...hat.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Wei Wang <weiwan@...gle.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Maciej Żenczykowski <maze@...gle.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv6: Reflect MTU changes on PMTU of exceptions for
 MTU-less routes

On 3/4/18 4:12 PM, Stefano Brivio wrote:
> On Sat, 3 Mar 2018 12:22:36 +0100
> Stefano Brivio <sbrivio@...hat.com> wrote:
> 
>>> And please codify the above expectation as a test under
>>> tools/testing/selftests/net  
>>
>> And this, along with v2.
> 
> On a second thought: I start thinking it doesn't make much sense,
> especially given the current context of self-tests, to explicitly test
> this, because it's a rather particular corner case.
> 
> I think it would make more sense to introduce generic tests first.
> About, say, PMTU, or route exceptions, but not "tunnel causes route
> exception and administrative change doesn't affect PMTU".
> 

I would argue corner cases in particular should be documented.

>From the commit message it seems like you took the time to create a test
setup using network namespaces. Throw those commands into a shell script
-- tools/testing/selftests/net/mtu.sh. It can evolve from there.