netdev - Re: [RFC] longer netdev names proposal

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Message-ID: <20190628084447.186a0efb@hermes.lan>
Date:   Fri, 28 Jun 2019 08:44:47 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Andrew Lunn <andrew@...n.ch>, Michal Kubecek <mkubecek@...e.cz>,
        netdev@...r.kernel.org, David Ahern <dsahern@...il.com>,
        davem@...emloft.net, jakub.kicinski@...ronome.com,
        mlxsw@...lanox.com
Subject: Re: [RFC] longer netdev names proposal

On Fri, 28 Jun 2019 15:55:53 +0200
Jiri Pirko <jiri@...nulli.us> wrote:

> Fri, Jun 28, 2019 at 03:14:01PM CEST, andrew@...n.ch wrote:
> >On Fri, Jun 28, 2019 at 01:12:16PM +0200, Jiri Pirko wrote:  
> >> Thu, Jun 27, 2019 at 09:20:41PM CEST, stephen@...workplumber.org wrote:  
> >> >On Thu, 27 Jun 2019 20:39:48 +0200
> >> >Michal Kubecek <mkubecek@...e.cz> wrote:
> >> >  
> >> >> > 
> >> >> > $ ip li set dev enp3s0 alias "Onboard Ethernet"
> >> >> > # ip link show "Onboard Ethernet"
> >> >> > Device "Onboard Ethernet" does not exist.
> >> >> > 
> >> >> > So it does not really appear to be an alias, it is a label. To be
> >> >> > truly useful, it needs to be more than a label, it needs to be a real
> >> >> > alias which you can use.    
> >> >> 
> >> >> That's exactly what I meant: to be really useful, one should be able to
> >> >> use the alias(es) for setting device options, for adding routes, in
> >> >> netfilter rules etc.
> >> >> 
> >> >> Michal  
> >> >
> >> >The kernel doesn't enforce uniqueness of alias.
> >> >Also current kernel RTM_GETLINK doesn't do filter by alias (easily fixed).
> >> >
> >> >If it did, then handling it in iproute would be something like:  
> >> 
> >> I think that it is desired for kernel to work with "real alias" as a
> >> handle. Userspace could either pass ifindex, IFLA_NAME or "real alias".
> >> Userspace mapping like you did here might be perhaps okay for iproute2,
> >> but I think that we need something and easy to use for all.
> >> 
> >> Let's call it "altname". Get would return:
> >> 
> >> IFLA_NAME  eth0
> >> IFLA_ALT_NAME_LIST
> >>    IFLA_ALT_NAME  eth0
> >>    IFLA_ALT_NAME  somethingelse
> >>    IFLA_ALT_NAME  somenamethatisreallylong  
> >
> >Hi Jiri
> >
> >What is your user case for having multiple IFLA_ALT_NAME for the same
> >IFLA_NAME?  
> 
> I don't know about specific usecase for having more. Perhaps Michal
> does.
> 
> From the implementation perspective it is handy to have the ifname as
> the first alt name in kernel, so the userspace would just pass
> IFLA_ALT_NAME always. Also for avoiding name collisions etc.

I like the alternate name proposal. The kernel would have to impose  uniqueness.
Does alt_name have to be unique across both regular and alt_name?
Having multiple names list seems less interesting but it could be useful.