netdev - Re: [PATCH RFC net-next] net: Allow name change of IFF

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Message-ID: <20170810101619.15142772@xeon-e3>
Date:   Thu, 10 Aug 2017 10:16:19 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     David Ahern <dsahern@...il.com>
Cc:     David Miller <davem@...emloft.net>, andrew@...n.ch,
        vkuznets@...hat.com, eric.dumazet@...il.com,
        netdev@...r.kernel.org, edumazet@...gle.com
Subject: Re: [PATCH RFC net-next] net: Allow name change of IFF_UP
 interfaces

On Thu, 10 Aug 2017 10:55:01 -0600
David Ahern <dsahern@...il.com> wrote:

> On 8/10/17 10:48 AM, David Miller wrote:
> > From: Andrew Lunn <andrew@...n.ch>
> > Date: Thu, 10 Aug 2017 18:27:22 +0200
> >   
> >> On Thu, Aug 10, 2017 at 05:24:55PM +0200, Vitaly Kuznetsov wrote:  
> >>> Andrew Lunn <andrew@...n.ch> writes:
> >>>  
> >>>>> We are - rtnetlink_event() does the job. We, however, don't have a
> >>>>> special IFLA_EVENT_* for name change and end up with IFLA_EVENT_NONE.  
> >>>>
> >>>> What is in this event? Old and new name? Just the new name?  
> >>>
> >>> Basically, it's everything we know about the interface - type, index,
> >>> name, mtu, qdisc, ... - see rtnl_fill_ifinfo(). Back to your question -
> >>> it's only the new name.  
> >>
> >> So the program needs to keep track of ifindex to know which interface
> >> has changed name. Doable.
> >>
> >> I still expect this has the potential to break something. You probably
> >> should be asking on linux-api for the API experts opinion.  
> > 
> > But a greater point is that nobody is monitoring device renames
> > explicitly right now.  
> 
> Just to throw in an example:
>   https://github.com/kobolabs/dhcpcd/blob/kobo/if-linux.c#L761
> 
> Learned of its use from a recent regression:
> https://bugzilla.kernel.org/show_bug.cgi?id=196355

Quagga is another example of what might break. Especially with all the new
forks..