feat(opennebula): support ETHx_METHOD and ETHx_IP6_METHOD

[mcanevet]

Proposed Commit Message

feat(opennebula): support ETHx_METHOD and ETHx_IP6_METHOD

cloud-init's OpenNebula datasource always generated static Netplan
configuration, ignoring ETHx_METHOD and ETHx_IP6_METHOD entirely.

Add get_method() and get_ip6_method() helpers and rework the IPv4/IPv6
blocks in gen_conf() to branch on the configured method:

IPv4 (ETHx_METHOD):
- static (default): existing behaviour, no regression
- dhcp: emit dhcp4: true, no addresses
- skip: omit interface from Netplan output entirely

IPv6 (ETHx_IP6_METHOD):
- static (default when ETHx_IP6 or ETHx_IP6_GATEWAY is present):
  existing behaviour
- dhcp/dhcp6: emit dhcp6: true
- auto/slaac: emit accept-ra: true
- disable/skip: suppress all IPv6 config

Additional Context

Part of a series bringing cloud-init's OpenNebula datasource to feature
parity with the context-linux package from one-apps.

The get_ip6_method() helper infers the default IPv6 method from context:
if ETHx_IP6 or ETHx_IP6_GATEWAY is present, it defaults to static;
otherwise disable. This preserves backwards-compatible behaviour for all
existing tests.

Test Steps

In an OpenNebula VM context, set:

ETH0_METHOD="dhcp"

After boot, verify the interface obtains its IP via DHCP (no static
address in ip addr show).

For IPv6 SLAAC:

ETH0_IP6_METHOD="auto"

After boot, verify ip addr show shows a SLAAC-derived IPv6 address.

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>)

[github-actions]

Hello! Thank you for this proposed change to cloud-init. This pull request is now marked as stale as it has not seen any activity in 14 days. If no activity occurs within the next 7 days, this pull request will automatically close.

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[mcanevet]

@blackboxsw rebased

[Copilot]

Pull request overview

This PR extends cloud-init’s OpenNebula datasource network generation to honor OpenNebula context variables ETH<x>_METHOD (IPv4) and ETH<x>_IP6_METHOD (IPv6), enabling DHCP, SLAAC/RA, and skipping behavior instead of always emitting static Netplan configuration.

Changes:

• Add get_method() and get_ip6_method() helpers to interpret ETH<x>_METHOD and infer/parse ETH<x>_IP6_METHOD.
• Rework OpenNebulaNetwork.gen_conf() to emit dhcp4: true, dhcp6: true, accept-ra: true, omit IPv6 config, or omit the interface entirely based on method selection.
• Add/extend unit tests and update OpenNebula datasource documentation to describe the new context variables.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
cloudinit/sources/DataSourceOpenNebula.py	Add IPv4/IPv6 method helpers and branch Netplan output on ETH<x>_METHOD / ETH<x>_IP6_METHOD.
doc/rtd/reference/datasources/opennebula.rst	Document the new OpenNebula context variables and their effects on generated Netplan.
tests/unittests/sources/test_opennebula.py	Add unit tests covering new method parsing and Netplan generation branches.

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