Re: Specifying names for tap interfaces

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Wed, Jun 20, 2012 at 01:05:55PM -0400, Mouse wrote:
> > So, we would like to be able to create interface alias, here is what
> > I think should be doable (from my PoV):
> 
> Here are some thoughts that come to mind.  I'm not sure they're all
> points worth worrying about.
> 
> > Adding a field to ifnet to contain that alias, something like
> > if_xalias, then being able to set that name with an ioctl [...]
> 
> Is a maximum of one alias per interface sufficient?  I once saw it said
> that "the number two is ludicrous" - having one of something is fine,
> but as soon as you have two, why not an unlimited number?  In this
> case, the "something" is names per interface.

We can probably make xalias a list instead of a single string. It shouldn't
change much things.

> 
> Why draw a distinction between the name and the alias?  (I actually can
> see some potential answers to this; I mention it more to provoke
> thought than because I think it's a serious issue.)

I think we want a name that stay attached to the hardware and won't be
arbitrary changed (at last not while you don't swap hardware).

> 
> > What I'm not sure is how to propagate that change to every tool that
> > interacts with network interfaces, we should of course change
> > ifconfig to be able to set/get this aliases, but then changes will
> > also be required to brconfig, pf...?
> 
> I see no need for all tools to be aware of aliases.  Many (most?) tools
> just use names to refer to interfaces and don't care about the finer
> points of it.  So as long as the names are valid for the purposes the
> tools are using them for, I see no reason for, eg, brconfig to care
> whether an interface it's trying to add is an alias or not.
> 
> > Also, when the user specifies something like ifconfig alias:foo up,
> > how do we know to what is alias:foo mapped to?
> 
> Who is "we"?  I see no reason for ifconfig to care; it just does the
> ioctl with "alias:foo" in the interface name field and doesn't care
> whether it's an alias, even, much less what it's an alias for.  Inside
> the kernel, for most purposes, this is entirely hidden within the "look
> up an interface given its name" code; as far as I can see, the only
> other things that have occasion to care are the specifcally alias-aware
> ones, like the code to set and get alias names.

Yes, that's what I have in mind.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--