Detect SR-IOV VFs via AZURE_UNMANAGED_SRIOV udev property

[s4heid]

Replace the sriov-vf ifalias check in the MAC address detector with detection of the AZURE_UNMANAGED_SRIOV=1 udev property applied by azure-vm-utils to SR-IOV VF devices bonded under hv_netvsc.

This makes MAC-based interface detection correct on stemcells that ship azure-vm-utils (e.g. Ubuntu Noble) without requiring a parallel stemcell-side ifalias workaround.

Stemcells that currently set ATTR{ifalias}="sriov-vf" (e.g. Ubuntu Jammy) already set ENV{AZURE_UNMANAGED_SRIOV}="1" alongside, so the new check is a strict superset of the previous behaviour.

The property is read from /run/udev/data/n<ifindex>, where udev persists per-device properties as lines of the form "E:KEY=VALUE".

Self-Validation

Built the agent, baked it into the latest noble stemcell and re-deployed with accelerated-networking enabled on Azure. Based on the logs it looks like the agent is going the right code path and ignores the VF interface (which uses mlx5_core driver):

zookeeper/df0f0087-4274-4862-aa82-04d601f3b1ea: ~# zgrep "Ignoring SR-IOV VF interface" /var/vcap/bosh/log/*
2026-06-26T15:32:47.924626+00:00 ab4fdf5c-2b60-431f-9995-5c53890866ae bosh-agent[1755]: [MacAddressDetectorl 2026/06/
6 15:32:47 DEBUG - Ignoring SR-IOV VF interface: eth1 (AZURE_UNMANAGED_SRIOV=1)
2026-06-26T15:32:52.694369+00:00 ab4fdf5c-2b60-431f-9995-5c53890866ae bosh-agent[3214]: [MacAddressDetector] 2026/06/
6 15:32:52 DEBUG - Ignoring SR-IOV VF interface: eth1 (AZURE_UNMANAGED_SRIOV=1)

zookeeper/df0f0087-4274-4862-aa82-04d601f3b1ea:~# ethtool -i eth1 | grep driver
driver: mlx5_core

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 073cce6d-3395-403e-b69d-b8ac32b7c731

📥 Commits

Reviewing files that changed from the base of the PR and between a2b2878 and 4cb6955.

📒 Files selected for processing (1)

• platform/net/mac_address_detector_test.go

Walkthrough

Linux MAC address detection now checks per-interface udev records for AZURE_UNMANAGED_SRIOV=1 and skips matching interfaces instead of using ifalias SR-IOV VF text. The detector reads the interface ifindex, loads /run/udev/data/n<ifindex>, and searches the udev contents for the tag. Tests were updated to cover unmanaged VF interfaces, missing udev data, and non-matching udev entries.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: detecting SR-IOV VFs via the AZURE_UNMANAGED_SRIOV udev property.
Description check	✅ Passed	The description is directly related to the code changes and explains the detection switch, compatibility, and validation.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@platform/net/mac_address_detector_test.go`:
- Around line 143-151: The test in mac_address_detector_test.go does not reach
the missing-udev-data branch because stubInterfacesWithVirtual only creates
address/ifalias and never an ifindex, causing isAzureUnmanagedSRIOV to fail
earlier. Update the test setup so the interface has a valid ifindex file while
intentionally omitting the /run/udev/data/n<ifindex> file, then keep the
DetectMacAddresses assertion in the same test to verify the missing-udev-data
path is exercised. Use the existing helpers and the isAzureUnmanagedSRIOV flow
to ensure the branch under test is actually hit.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: f6a411a7-cb17-4226-a7b0-06a1c22cc1cf

📥 Commits

Reviewing files that changed from the base of the PR and between cb03d31 and a2b2878.

📒 Files selected for processing (2)

• platform/net/mac_address_detector.go
• platform/net/mac_address_detector_test.go