+++ This bug was initially created as a clone of Bug #2084471 +++

Version:
4.10.11

$ openshift-install version
>built from commit 08bc665c50ff867ffd81cfe8f485f2b7c501506b
>release image quay.io/openshift-release-dev/ocp->release@sha256:0dc1a4b4d9ea7954987f63e506474a4f0dc55e5f1ea5c1f6f1179e2c09eaffda
>release architecture amd64

Platform:
baremetal

Please specify:
I believe this affects both of IPI and UPI, in this case Assisted Installer was used when this bug was noticed
* IPI (automated install with `openshift-install`. If you don't know, then it's IPI)
* UPI (semi-manual installation on customized infrastructure)

What happened?

Capital letters in install-config.yaml .platform.baremetal.hosts[].name caused bootkube errors

bootkube stuck looping with the following error on repeat:

>May 09 17:12:10 My-node-0 bootkube.sh[35010]: "99_openshift-cluster-api_hosts-4.yaml": failed to create baremetalhosts.v1alpha1.metal3.io/My-node-0 -n openshift-machine-api: BareMetalHost.metal3.io "My-node-0" is invalid: metadata.name: Invalid value: "My-node-0": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')

This happens because those install config names are used directly as BMH .metadata.name's, see [1]

What did you expect to happen?

Either one of:

1. The installer should transform the names to become valid k8s resource identifiers and make sure that there are no collisions post-transformation
or
2. The installer should have failed at a much earlier stage, with clear validation errors on those names

How to reproduce it (as minimally and precisely as possible)?

Use capital letters in install config metal host names

Anything else we need to know?
-

[1] https://github.com/openshift/installer/blob/8b3d14deea2e5360565b09173e6e448dff4883b5/pkg/asset/machines/baremetal/hosts.go#L96

--- Additional comment from W. Trevor King on 2022-05-12 19:11:33 UTC ---

Trying to pin down the lowercase requirement [1]:

  The syntax of a legal Internet host name was specified in RFC-952
  [DNS:4].  One aspect of host name syntax is hereby changed: the
  restriction on the first character is relaxed to allow either a
  letter or a digit.  Host software MUST support this more liberal
  syntax.

And [2]:

  No distinction is made between upper and lower case.

And moving over to [3]:

  For all parts of the DNS that are part of the official protocol, all
  comparisons between character strings (e.g., labels, domain names, etc.)
  are done in a case-insensitive manner.  At present, this rule is in
  force throughout the domain system without exception.  However, future
  additions beyond current usage may need to use the full binary octet
  capabilities in names, so attempts to store domain names in 7-bit ASCII
  or use of special bytes to terminate labels, etc., should be avoided.

  When data enters the domain system, its original case should be
  preserved whenever possible.

Rooting around upstream turned up [4] which replaced "RFC 1123" with "DNS-1123" (I don't understand why), pointing at [5] and claiming:

  #39635 was rejected because it wasn't clear to the author (me) that lower-case DNS labels are in fact a Kubernetes requirement rather than from the DNS RFC 1035 or/and DNS RFC 1123.

Then [6] moved us to "a lowercase RFC 1123 subdomain", which I expect means "Kubernetes requires RFC 1123 compliance and extend that to also require lowercasing".

So we should probably slot in k8s.io/apimachinery/pkg/util/validation's IsDNS1123Subdomain (which we already use [7]) for this field too, so we enforce both the RFC constrains and Kube's case extension.

[1]: https://www.rfc-editor.org/rfc/rfc1123.html#section-2
[2]: https://www.rfc-editor.org/rfc/rfc952
[3]: https://www.rfc-editor.org/rfc/rfc1035#section-2.3.3
[4]: https://github.com/kubernetes/kubernetes/pull/39675
[5]: https://github.com/kubernetes/kubernetes/pull/39635#issuecomment-271404975
[6]: https://github.com/kubernetes/kubernetes/pull/94182
[7]: https://github.com/openshift/installer/blob/c7bd7993409f003bc0fb9105d7231253f546f1cd/pkg/validate/validate.go#L49