netdev - Re: [patch net-next rfc 3/7] net: rtnetlink: add commands to add and delete alternative ifnames

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Date:   Fri, 9 Aug 2019 10:14:03 -0600
From:   David Ahern <dsahern@...il.com>
To:     Roopa Prabhu <roopa@...ulusnetworks.com>,
        Jiri Pirko <jiri@...nulli.us>
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>, dcbw@...hat.com,
        Michal Kubecek <mkubecek@...e.cz>,
        Andrew Lunn <andrew@...n.ch>, parav@...lanox.com,
        Saeed Mahameed <saeedm@...lanox.com>,
        mlxsw <mlxsw@...lanox.com>
Subject: Re: [patch net-next rfc 3/7] net: rtnetlink: add commands to add and
 delete alternative ifnames

On 8/9/19 9:40 AM, Roopa Prabhu wrote:
>>>> diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
>>>> index ce2a623abb75..b36cfd83eb76 100644
>>>> --- a/include/uapi/linux/rtnetlink.h
>>>> +++ b/include/uapi/linux/rtnetlink.h
>>>> @@ -164,6 +164,13 @@ enum {
>>>>         RTM_GETNEXTHOP,
>>>>  #define RTM_GETNEXTHOP RTM_GETNEXTHOP
>>>>
>>>> +       RTM_NEWALTIFNAME = 108,
>>>> +#define RTM_NEWALTIFNAME       RTM_NEWALTIFNAME
>>>> +       RTM_DELALTIFNAME,
>>>> +#define RTM_DELALTIFNAME       RTM_DELALTIFNAME
>>>> +       RTM_GETALTIFNAME,
>>>> +#define RTM_GETALTIFNAME       RTM_GETALTIFNAME
>>>> +
>>>
>>> I might have missed the prior discussion, why do we need new commands
>>> ?. can't this simply be part of RTM_*LINK and we use RTM_SETLINK to
>>> set alternate names ?
>>
>> How? This is to add/remove. How do you suggest to to add/remove by
>> setlink?
> 
> to that point, I am also not sure why we have a new API For multiple
> names. I mean why support more than two names  (existing old name and
> a new name to remove the length limitation) ?
> 
> Your patch series addresses a very important problem (we run into this
> limitation all  the time and its hard to explain it to network
> operators) and
>  its already unfortunate that we have to have more than one name
> because we cannot resize the existing one.
> 
> The best we can do for simpler transition/management from user-space
> is to keep the api simple..
> ie keep it close to the management of existing link attributes. Hence
> the question.
> 
> I assumed this would be like alias. A single new field that can be
> referenced in lieu of the old one.
> 
> Your series is very useful to many of us...but when i think about
> changing our network manager to accommodate this, I am worried about
> how many apps will have to change.
> I agree they have to change regardless but now they will have to
> listen to yet another notification and msg format for names ?
> 
> (apologies for joining the thread late and if i missed prior discussion on this)

I agree with Roopa. I do not understand why new RTM commands are needed.
The existing IFLA + ifinfomsg struct give more than enough ways to id
the device for adding / deleting an alternate name.