switching to `ip=auto` for NetworkManager dracut defaults

[dustymabe]

Once NM#994 lands we'll want to switch to ip=auto to continue to get the same behavior we currently have.

• Currently ip=dhcp,dhcp6 gives us
  • both dhcp4 and dhcp6 tried, with an extra 20 second wait for ipv4
    • see NM#729
• In the future ip=dhcp,dhcp6 will give us:
  • both dhcp4 and dhcp6 tried, with an extra 20 second wait for ipv4 AND ipv6
    • see NM#994

The extra timeout for ipv6 is not really desired as a default IMO.

After talking with @bengal ip=auto generates the same config we have today (our desired config) so we'll switch to that when the time comes in order to maintain our current default behavior.

[jlebon]

Does ip=auto work today? If so, should we just switch to that now?

[dustymabe]

Does ip=auto work today? If so, should we just switch to that now?

good point, yes I think we could go ahead and switch to it now. Let's wait for the upstream PR to actually land (just to make sure it goes through and something else doesn't change) and then implement the change once we know it's coming.

[dustymabe]

The upstream PR merged. Here's what I think we need to do:

• update every place that hardcodes ip=dhcp,dhcp6 in our code bases to be ip=auto instead
• add a test that fails anytime the generated configuration from nm-initrd-generator changes
  • This will help us know when the defaults change and if we need to adjust anything