fix: add pre-create NIC readiness gate before New-HNSNetwork to avoid windows race condition

[timmy-wright]

Problem

When New-HNSNetwork is called while the primary NIC is still transitioning from its APIPA (169.254/16) address to its DHCP address, HNS latches the APIPA address as ProviderAddress. Since HNS doesn't proactively update ProviderAddress after creation, this persists and causes node provisioning failures.

Fix

Added a pre-create readiness gate in New-ExternalHnsNetwork (azurecnifunc.ps1) that polls the chosen network adapter for a stable, non-APIPA IPv4 address in Preferred state before calling New-HNSNetwork. The gate:

• Polls Get-NetIPAddress every 500ms, up to 120 seconds
• Proceeds immediately once a non-169.254.x.x Preferred IP is found
• If it times out, logs a warning and proceeds (existing post-create checks remain as the safety net)

Tests

Added Describe 'New-ExternalHnsNetwork' Pester tests covering:

• Stable Preferred IP found immediately → no retries, New-HNSNetwork called once
• APIPA initially, stable IP appears after retries → gate waits then proceeds
• Gate timeout (all APIPA) → logs warning but still calls New-HNSNetwork
• Dual-stack mode → correct dual-stack address prefixes passed

[Copilot]

Pull request overview

Addresses a Windows node provisioning race where New-HNSNetwork can latch an APIPA address as ProviderAddress if the primary NIC is still transitioning to its DHCP address.

Changes:

• Add a pre-create readiness gate in New-ExternalHnsNetwork to wait (up to 120s) for a stable, non-APIPA IPv4 in Preferred state before calling New-HNSNetwork.
• Add Pester tests for the new readiness-gate behaviors and dual-stack invocation shape.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
staging/cse/windows/azurecnifunc.ps1	Adds pre-create polling gate to avoid HNS latching APIPA ProviderAddress during NIC transition.
staging/cse/windows/azurecnifunc.tests.ps1	Adds Pester coverage for the readiness gate and dual-stack New-HNSNetwork call pattern.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.