feat(opennebula): support PCIx_* passthrough network interfaces

[mcanevet]

Proposed Commit Message

feat(opennebula): support PCIx_* passthrough network interfaces

OpenNebula's context-linux package configures PCI passthrough NICs
using PCIx_ADDRESS / PCIx_IP / PCIx_MASK / PCIx_GATEWAY / PCIx_MTU /
PCIx_VLAN_ID variables. cloud-init ignored these entirely.

Add _get_pci_context_ifaces() to scan context keys for PCIx_ADDRESS
entries, and _pci_addr_to_dev() to resolve a PCI address to a system
device name via /sys/bus/pci/devices/<addr>/net/. Extend gen_conf() to
emit ethernets: entries for each PCI device, with optional VLAN support
matching the existing ETHx_VLAN_ID behaviour. Devices whose sysfs path
cannot be found are skipped with a warning.

Additional Context

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

PCI passthrough NICs cannot be matched by MAC address (they have no
ETHx_MAC equivalent), so _pci_addr_to_dev() resolves via sysfs
instead. The _pci_sysfs_root class attribute is overridable in tests
to avoid touching the real filesystem.

Test Steps

In an OpenNebula VM with a PCI passthrough NIC at address 0000:00:06.0,
set:

PCI0_ADDRESS="0000:00:06.0"
PCI0_IP="10.5.0.1"
PCI0_MASK="255.255.255.0"
PCI0_GATEWAY="10.5.0.254"

After boot, verify ip addr show enp0s6 (or whatever the device is
named) shows 10.5.0.1/24.

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 the OpenNebula datasource’s network configuration generation to support PCI passthrough NICs configured via OpenNebula context variables (PCI<x>_*), resolving PCI addresses to interface names through sysfs and emitting corresponding netplan configuration.

Changes:

• Add helpers to discover PCI<x>_ADDRESS context entries and map PCI addresses to netdev names via /sys/bus/pci/devices/<addr>/net/.
• Extend OpenNebulaNetwork.gen_conf() to emit netplan entries for PCI passthrough NICs, including optional VLAN configuration.
• Add unit tests and update OpenNebula datasource documentation to describe the new PCI context variables.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
cloudinit/sources/DataSourceOpenNebula.py	Adds PCI context scanning + sysfs resolution and emits netplan config for PCI passthrough NICs (with VLAN support).
tests/unittests/sources/test_opennebula.py	Adds unit tests covering PCI context parsing, sysfs resolution, and basic PCI static config emission.
doc/rtd/reference/datasources/opennebula.rst	Documents supported PCI<x>_* context variables and behavior.

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