[systemd-devel] Udev won't rename interfaces that are already UP

[Tom Gundersen]

On Thu, Feb 19, 2015 at 2:06 PM, Giancarlo Razzolini
<grazzolini at gmail.com> wrote:
> On 19-02-2015 10:50, Tom Gundersen wrote:
>>
>> Won't work. Imagine you have two cards with the same driver. Now you
>> are back to having to number the cards. And that is what open BSD
>> does: numbers the cards based on probe order. The probe order is
>> nondeterministic so you are not guaranteed the same order and hence
>> the same name on every boot.
>>
>
> I believe that this might have been the case in a remote past. But,
> afaik, the current way is deterministic. I never ended up having name
> switchs with the same driver for a very long time.

Even on Linux you are mostly fine. It is the last 1% of cases or
something like that we have to worry about. If OpenBSD is doing some
magic we could steal the idea, but so far I have not seen anything
non-trivial there. Happy to be proven wrong.

>> In general any name that may be affected by other cards on the machine
>> won't work as there is no way to know what cards will be present, nor
>> the order in which they appear. So you can name your card based on
>> properties of the card or properties of its parents, but that's about it.
>>
>
> I agree that other cards interference is undesired.
>
>> We have infrastructure in the kernel for informing us that it already
>> picked a good name, so if you come up with a nice kernel scheme you
>> could indicate to us that we should back off. Please make it
>> deterministic though...
> It's not my intention,

Well, maybe someone else reading the list... :)

> since I'm not a kernel nor systemd hacker. I can
> read the code, possibly understand it and even perhaps make some minor
> changes. But I don't believe I have the skill set for this kind of major
> revamp. I was just reminiscing. Never mind.

Cheers,

Tom