Bug#982688: wireless interface name unstable across reboots

[Yuri D'Elia]

On Sun, Feb 14 2021, Michael Biebl wrote:
>> I'd like, ideally, to keep stable interface names. I'm not sure if this
>> is intended, but so far after masking 80-iwd and removing "keep" from
>> the NamePolicy it seems that udev is always able to rename the interface
>> across reboots.
>>
>> It might entirely be because iwd started to operate on the original
>> device name, but didn't have time to bring it up before the rename
>> happens I guess.
>
> See also
> https://iwd.wiki.kernel.org/interface_lifecycle#udev_interface_renaming

I don't think there's anything specific to iwd here though.

My main point is that the race can technically affect anything that
needs to use the interface name during boot:

- interface names might change
- we're not using dbus
- as a result we'd like to rely on "stable" names provided by the udev
  policy
- but there's no way to wait for udev to settle without polling
  apparently?

this somehow contradicts the usefulness of the stable interface names
feature.

As an example, when loading ipt/nft rulesets I'd like to set the rules
*before* the interface is brought up. How to I sequence the service so
that this happens after the rename but before the interface is brought
up? Looks like I can incur in the same race as iwd.