feat(opennebula): support ETHx_ROUTES static routes in network config

[mcanevet]

Proposed Commit Message

feat(opennebula): support ETHx_ROUTES static routes in network config

Add `get_routes()` to `OpenNebulaNetwork` to parse the `ETHx_ROUTES`
context variable (format: "NETWORK via GATEWAY, ...") and emit the
resulting routes into the Netplan v2 `routes:` list in `gen_conf()`.

Malformed entries are skipped with a warning. No `routes` key is
emitted when the variable is absent or empty, preserving backward
compatibility.

Additional Context

The OpenNebula context-linux package (one-apps) supports ETHx_ROUTES
to configure static routes per interface. cloud-init's OpenNebula
datasource was silently ignoring this variable, meaning any static
routes defined in the VM template were never applied.

Test Steps

On an OpenNebula VM, add to the VM template context section:

ETH0_ROUTES="10.0.0.0/8 via 192.168.1.1, 172.16.0.0/12 via 192.168.1.254"

After boot, verify the routes were applied:

ip route show
# expected: routes to 10.0.0.0/8 and 172.16.0.0/12 via 192.168.1.x

Also verify that a VM with no ETHx_ROUTES set continues to boot and
configure networking without any change in behaviour.

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[holmanb]

Hey @mcanevet. What is your goal and intent with these PRs? It doesn't look like you are trying to a single missing feature. Are you employed by Open Nebula?

[mcanevet]

I'm just trying to add support for context variables that are honored by Open Nebula's official agent. And I'm not working for them, just a simple user that would like to use cloud-init with complex network configuration. Do you prefer a single PR for all of this?

[mcanevet]

@holmanb do you prefer a single PR to implement this feature that reduces the gap between the OpenNebula agent (https://github.com/OpenNebula/one-apps/tree/master/context-linux) and Cloud-init? We basically need this to use cloud-init with standard OpenNebula context variables that the official agent support.

[holmanb]

I have a few concerns:

1. The proposed PR would change existing behavior, so stable distros would need to patch these changes out.
2. The OpenNebula Python datasource code type checking is disabled (see pyproject.toml). If the existing code first passed mypy's checks, it would be easier to have confidence in subsequent changes to this code.
3. Not something that you are responsible for or that I expect you to change, but Opennebula's design choice to provide a bash script as the source of platform information is not ideal for consuming that information from Python.

Additionally, I would like to see the the full cloud-init logs on the system that you tested these changes on as well as from an instance without these changes applied - as well as a context.sh file content.

[mcanevet]

Hi @holmanb,

regarding first concern about changing existing behavior:

Looking at the diff, I believe this change is purely additive. The get_routes() method is new, and in gen_conf() the routes key is only added to the device config when ETHx_ROUTES is explicitly present in the context variables:

extra_routes = self.get_routes(c_dev)
if extra_routes:
  devconf["routes"] = extra_routes

If ETHx_ROUTES is absent (as it would be in all existing deployments), get_routes() returns an empty list, the condition is false, and gen_conf() output is identical to today's. No existing context variables are reinterpreted or removed.

Could you clarify what specific behavior you see changing? I want to make sure I'm not missing something.

Regarding the second concern, I enabled type checking in #6827.

[mcanevet]

Here is a gist with context.sh, cloud-init.log and cloud-init-output.log:
https://gist.github.com/mcanevet/7561c97acd64c8ebd980843bc8ca90ee

[mcanevet]

you can see in the logs that before my patch, the ETH0_ROUTES context variable is not used.
here is the official documentation for the context variables: https://docs.opennebula.io/6.10/management_and_operations/references/template.html#context-section