netdev - Re: [RFC PATCH net-next] failover: allow name change on IFF

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Message-ID: <20190305112427.1a23822e@shemminger-XPS-13-9360>
Date:   Tue, 5 Mar 2019 11:24:27 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     si-wei liu <si-wei.liu@...cle.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Sridhar Samudrala <sridhar.samudrala@...el.com>,
        Jakub Kicinski <kubakici@...pl>, Jiri Pirko <jiri@...nulli.us>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org, liran.alon@...cle.com,
        boris.ostrovsky@...cle.com, vijay.balakrishna@...cle.com
Subject: Re: [RFC PATCH net-next] failover: allow name change on IFF_UP
 slave interfaces

On Tue, 5 Mar 2019 11:19:32 -0800
si-wei liu <si-wei.liu@...cle.com> wrote:

> > I have a vague idea: would it work to *not* set
> > IFF_UP on slave devices at all?  
> Hmm, I ever thought about this option, and it appears this solution is 
> more invasive than required to convert existing scripts, despite the 
> controversy of introducing internal netdev state to differentiate user 
> visible state. Either we disallow slave to be brought up by user, or to 
> not set IFF_UP flag but instead use the internal one, could end up with 
> substantial behavioral change that breaks scripts. Consider any admin 
> script that does `ip link set dev ... up' successfully just assumes the 
> link is up and subsequent operation can be done as usual. While it *may* 
> work for dracut (yet to be verified), I'm a bit concerned that there are 
> more scripts to be converted than those that don't follow volatile 
> failover slave names. It's technically doable, but may not worth the 
> effort (in terms of porting existing scripts/apps).
> 
> Thanks
> -Siwei

Won't work for most devices.  Many devices turn off PHY and link layer
if not IFF_UP