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

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Message-ID: <88b507b7-1b60-5100-3e31-b68263f0f631@gmail.com>
Date:   Thu, 10 Aug 2017 10:55:01 -0600
From:   David Ahern <dsahern@...il.com>
To:     David Miller <davem@...emloft.net>, andrew@...n.ch
Cc:     vkuznets@...hat.com, eric.dumazet@...il.com,
        netdev@...r.kernel.org, edumazet@...gle.com,
        stephen@...workplumber.org
Subject: Re: [PATCH RFC net-next] net: Allow name change of IFF_UP interfaces

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