OpenStack single-stack IPv6 support

[mdbooth]

Feature Request

Ignition can fetch metadata from OpenStack's IPv4 metadata endpoint¹. However, since OpenStack Victoria, the metadata service now supports both an IPv4 and an IPv6 endpoint². In single-stack IPv6 environments we only have the IPv6 endpoint, which prevents ignition from fetching metadata.

Environment

OpenStack

Desired Feature

Add support for the IPv6 metadata endpoint to the OpenStack provider.

Other Information

Footnotes

1. https://github.com/coreos/ignition/blob/7548ac6dafbb93fe89baf8853e97b71123cc5aed/internal/providers/openstack/openstack.go#L46-L53 ↩

2. https://docs.openstack.org/nova/2024.1/user/metadata.html ↩

[mdbooth]

/cc @MaysaMacedo

[travier]

How the work to get this could be split:

1. Get an OpenStack VM running with IPv6 metada endpoint available
2. Figure out the right URL / paths to fetch using curl commands
3. Reproduce that in a small Go binary that does just that
4. Add that to Ignition and test in Fedora CoreOS
5. Add a kola test for it

[tormath1]

Hey folks,

There is a similar ask for Scaleway here: flatcar/Flatcar#1696

I think the implementation should be done internally and not per provider:

1. A provider defines a map of two endpoints ("v4" and "v6")
2. Ignition detects if the network runtime is ipv4 only, ipv6 only or dual-stack
3. The fetcher uses the associated endpoint

The challenge seats in 2) "Ignition detects if the runtime is ipv4 only, ipv6 only or dual-stack" - especially for systems where network setup is not immediate.

For example if we set "ipv6" only because "ipv4" was unreachable because of slow network setup, this would be incorrect.