linux-kernel - Re: [PATCH] hv_set_ifconfig.sh double check before setting ip

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Date:   Wed, 9 Aug 2017 11:02:12 +0200
From:   Eduardo Otubo <otubo@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org, sthemmin@...rosoft.com,
        haiyangz@...rosoft.com, kys@...rosoft.com
Subject: Re: [PATCH] hv_set_ifconfig.sh double check before setting ip

On 08/09/2017 06:11 AM, David Miller wrote:
> From: Eduardo Otubo <otubo@...hat.com>
> Date: Tue,  8 Aug 2017 15:53:45 +0200
> 
>> This patch fixes the behavior of the hv_set_ifconfig script when setting
>> the interface ip. Sometimes the interface has already been configured by
>> network daemon, in this case hv_set_ifconfig causes "RTNETLINK: file
>> exists error"; in order to avoid this error this patch makes sure double
>> checks the interface before trying anything.
>>
>> Signed-off-by: Eduardo Otubo <otubo@...hat.com>
> 
> And if the daemon sets the address after you test it but before
> you try to set it in the script, what happens?
> 
> This is why I hate changes like this.  They don't remove the problem,
> they make it smaller.  And smaller in a bad way.  Smaller makes the
> problem even more harder to diagnose when it happens.
> 
> There is implicitly no synchonization between network configuration
> daemons and things people run by hand like this script.
> 
> So, caveat emptor.
> 
> I'm not applying this, sorry.
> 

This is just part of the resolution, actually. For RHEL I also configure 
hyperv-daemons' systemd config file to be run only after network service 
is up.

So perhaps my solution should be distro-agnostic and only involve this 
script as part of it? In this case I'll elaborate a little more then.

Thanks for the comment.