refactor: resolve the boot NIC through one shared step

[chet]

Four Redfish boot steps -- the three boot-order substates (SetBootOrder,
WaitForHttpBootDeviceApplied, CheckBootOrder) and host boot repair -- each
opened with the same fifteen-line block resolving the host's boot NIC, with
only the wait message differing. The resolution step now lives in one helper,
require_boot_interface, and each caller states just the activity it's
blocked on: a zero-DPU host still discovering its boot NIC maps to the
caller's wait outcome, and a host with no resolvable interface stays a hard
error.

• One source of truth for the resolve-or-wait-or-fail choreography, so the
  boot steps can't drift apart as the state machine grows.
• Behavior-preserving: every caller keeps its exact wait message (the helper
  templates "before "), and wait-vs-error semantics are unchanged.
• Call sites shrink from fifteen lines to a handful each.

This supports #3193

Signed-off-by: Chet Nichols III chetn@nvidia.com

Closes #3193

[chet]

@coderabbitai full_review, thanks!

[coderabbitai]

@chet, you got it — kicking off a full review of all changes now.

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• crates/machine-controller/src/handler.rs

---

Summary by CodeRabbit

• Bug Fixes
  • Improved host boot-device handling so NIC discovery “wait” behavior is consistent across boot configuration checks and boot-order state transitions.
  • Missing boot interfaces now produce the same clear terminal error across affected flows.
• Tests
  • Added unit coverage for boot-interface resolution outcomes (Ready, awaiting NIC, and Missing) to prevent regressions.

Walkthrough

Refactors boot-interface resolution in crates/machine-controller/src/handler.rs by introducing RequiredBootInterface and require_boot_interface, consolidating wait/error handling across check_host_boot_config and three set_host_boot_order state-machine arms.

Changes

Boot interface resolution refactor

Layer / File(s)	Summary
RequiredBootInterface helper crates/machine-controller/src/handler.rs	Adds the private RequiredBootInterface<W> enum, the require_boot_interface wrapper, and tests for Ready, AwaitingNic, and Missing mappings.
Boot interface call-site integration crates/machine-controller/src/handler.rs	check_host_boot_config and the SetBootOrder, WaitForHttpBootDeviceApplied, and CheckBootOrder arms delegate to require_boot_interface, preserving their wait outcomes and treating Missing as terminal.

Estimated code review effort: 2 (Simple) | ~15 minutes

Possibly related issues

• Extract a shared boot-NIC resolution step for the boot-order substates #3193: Refactors the same boot-order state-machine boot-interface handling in handler.rs.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the shared boot NIC resolution refactor across the boot flow.
Description check	✅ Passed	The description matches the change set and accurately explains the shared helper refactor.
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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• Create PR with unit tests

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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 `@crates/machine-controller/src/handler.rs`:
- Around line 4930-4960: Add direct unit coverage for require_boot_interface in
handler.rs, since it wraps resolve_boot_interface and currently lacks focused
tests. Create cases for RequiredBootInterface::Ready,
RequiredBootInterface::Wait from BootInterfaceResolution::AwaitingNic (verify
the wait constructor is invoked with the expected message), and the Missing path
returning StateHandlerError::GenericError. Use the require_boot_interface and
RequiredBootInterface symbols to locate the code and assert the wrapper’s
mapping behavior independently of resolve_boot_interface.

🪄 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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• crates/machine-controller/src/handler.rs

[chet]

@coderabbitai full_review, thanks!

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🔍 Container Scan Summary

Service	Total	Critical	High	Medium	Low	Other
boot-artifacts-aarch64	3	0	0	3	0	0
boot-artifacts-x86_64	3	0	0	3	0	0
forge-admin-cli-x86_64	270	5	25	89	7	144
machine-validation-runner	771	25	207	278	40	221
machine_validation	771	25	207	278	40	221
machine_validation-aarch64	771	25	207	278	40	221
nvmetal-carbide	771	25	207	278	40	221
TOTAL	3360	105	853	1207	167	1028

Per-CVE detail lives in the per-service grype-* artifacts (JSON + SARIF). Severity counts only — no CVE IDs published here.