chore(rt): address review nits from #1968 and #1974

[edipascale]

Follow-ups to comments that were marked addressed but were not:

• record that the proto-port probe semaphore only covers its own phase, since the server-to-server phase keeps pinging concurrently
• release that semaphore via defer, so a future early exit between the acquire and the release cannot stall the phase on its single slot
• fail loudly when a NAT test finds no servers to probe: an empty source list reads as "no filter" downstream and probes the whole matrix
• run Gateway Peering Overlap NAT last in the gateway NAT/ACL suite; it creates an IPv4Namespace and a VPC and re-attaches a server, and without a wipe between tests the rest of the suite inherits whatever its reverts miss
• fix the -D -O ping fixture timestamps, which were non-monotonic and duplicated

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: ff7c4e48-60ad-4b1a-9301-60419308da03

📥 Commits

Reviewing files that changed from the base of the PR and between c4d9ba7 and 5e8adcb.

📒 Files selected for processing (4)

• pkg/hhfab/matrix.go
• pkg/hhfab/rt_gw_nat_acl_suite.go
• pkg/hhfab/rt_nat_tests.go
• pkg/hhfab/testing_test.go

Included review availability: 3 reviews are currently available. Based on recent review activity, included reviews refill at 5 per hour.

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📝 Walkthrough

Walkthrough

Changes

Probe and NAT testing

Layer / File(s)	Summary
Probe dispatch semaphore cleanup pkg/hhfab/matrix.go	The proto-port semaphore now releases through deferred cleanup for all protocol outcomes. Its documentation distinguishes proto-port probes from concurrent server-to-server probes.
NAT test selection and gateway suite ordering pkg/hhfab/rt_nat_tests.go, pkg/hhfab/rt_gw_nat_acl_suite.go	NAT tests now fail when no probe servers exist. Probe selection comments define outside-VPC and shared-server handling. Gateway peering overlap NAT runs separately at the end of the gateway suite.
Ping fixture alignment pkg/hhfab/testing_test.go	The middleLostReported fixture uses timestamped replies for ICMP sequences 4 and 5.

Possibly related PRs

• githedgehog/fabricator#1761: Introduced related matrix-based connectivity and NAT testing.
• githedgehog/fabricator#1835: Added related lost-sequence parsing that uses timestamped ping output.
• githedgehog/fabricator#1991: Shares gateway NAT/ACL suite and NAT probe-scope changes.

Suggested reviewers: frostman, pau-hedgehog

Merge Risk: ⚪ Minimal · up to 5e8ad

The PR is merge-ready after normal checks and review; no actionable merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the changes as follow-up review fixes for the referenced runtime pull requests.
Description check	✅ Passed	The description directly explains each follow-up fix implemented in the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

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[github-actions]

Release Tests

  8 files   -  1   40 suites   - 5   3h 4m 30s ⏱️ - 1h 24m 58s
 58 tests ± 0   41 ✅  - 15   17 💤 +15  0 ❌ ±0 
464 runs   - 58  201 ✅  - 55  263 💤  -  3  0 ❌ ±0 

Results for commit 6711e57. ± Comparison against base commit 58a74b0.

♻️ This comment has been updated with latest results.

[Copilot]

Pull request overview

Follow-up cleanup to the hhfab runtime connectivity/NAT test harness to ensure probes are correctly scoped/serialized, test selection order avoids state leakage, and fixtures reflect the ping output formats the probes now parse.

Changes:

• Make proto-port probe semaphore usage explicit and safer (release via defer within the proto-port probe scope).
• Make NAT tests fail loudly when no probe servers are found (preventing unintended “probe everything” behavior).
• Reorder “Gateway Peering Overlap NAT” to run last in the Gateway NAT/ACL suite and fix ping fixture timestamps for -D -O output.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
pkg/hhfab/testing_test.go	Fixes ping -D -O fixture timestamps to be monotonic/unique to match real output expectations.
pkg/hhfab/rt_nat_tests.go	Adds an explicit error when probe sources are empty; clarifies probe-server selection behavior; removes overlap test from the general NAT list.
pkg/hhfab/rt_gw_nat_acl_suite.go	Appends “Gateway Peering Overlap NAT” last to reduce cross-test state contamination in the suite.
pkg/hhfab/matrix.go	Clarifies probe semaphore scope and releases the semaphore via defer to prevent stalls on early exits.

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