fix(network-segment): make dual-stack metrics deterministic

[pbreton]

Summary

Network-segment compatibility metrics expose one prefix per segment. The controller selected prefixes[0], but database prefix aggregation does not guarantee row order, so a dual-stack segment could alternate between IPv4 and IPv6 labels and counts.

This change explicitly prefers the IPv4 prefix for the existing compatibility series and retains the IPv6 prefix for IPv6-only segments. Metric names and label names remain unchanged.

Related issues

Fixes #5402.

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• No testing required (docs, internal refactor, etc.)

Validation performed:

• cargo test -p carbide-network-segment-controller
• cargo clippy -p carbide-network-segment-controller --all-targets --all-features -- -D warnings
• cargo +nightly fmt --all -- --check
• cargo check -p carbide-api-core --lib --no-default-features
• git diff --check

The reversed-prefix regression was confirmed to fail before the fix and pass afterward.

Additional Notes

This is an attempt at fully automated issue resolution using Codex.

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[pbreton]

@coderabbitai full review.

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• crates/network-segment-controller/src/handler.rs

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Summary by CodeRabbit

• Bug Fixes
  • Improved network-segment metrics for dual-stack configurations by consistently prioritizing IPv4 address ranges.
  • Added reliable fallback handling for IPv6-only configurations.
  • Corrected metric values and address-space calculations that could vary based on prefix ordering.
  • Improved consistency and accuracy of network capacity reporting across different segment configurations.

Walkthrough

The handler now selects an IPv4 prefix for network-segment metrics when available. IPv6-only segments use their first prefix. Tests cover dual-stack prefix order and IPv6 fallback.

Changes

Network-segment metrics

Layer / File(s)	Summary
Compatibility prefix selection crates/network-segment-controller/src/handler.rs	The handler prefers the first IPv4 prefix and falls back to the first available prefix.
Metric integration and validation crates/network-segment-controller/src/handler.rs	Available IPs, reserved IPs, reported prefixes, and address-space calculations use the selected prefix. Tests cover dual-stack order independence and IPv6-only fallback.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to db503

The change makes compatibility metrics deterministic while preserving the existing metric interface. No actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 28.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes satisfy issue #5402 by removing prefix-order dependence, defining deterministic dual-stack selection, preserving IPv6-only behavior, and keeping metric names unchanged.
Out of Scope Changes check	✅ Passed	The reported changes are limited to network-segment metric prefix selection and related regression tests. No unrelated code changes are identified.
Title check	✅ Passed	The title clearly and concisely describes the primary change: deterministic dual-stack metrics for network segments.
Description check	✅ Passed	The description directly explains the prefix-order bug, the IPv4 preference and IPv6 fallback, the compatibility constraints, and the validation performed.

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[pbreton]

@coderabbitai full review.

[coderabbitai]

@pbreton I will perform a complete review of #5632.

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[coderabbitai]

@pbreton I will perform a complete review of #5632.

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Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-01T19:44:16.039420Z	db503f6	Draft marked ready

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