otbr: Automatically migrate OTBR settings to last-good backup

[puddly]

Current TLV parsing issues in Core appear to be the result of the "bad" tmp data file being loaded by the migration script and passed through to OTBR. It manages to start up and broadcast the broken 8 byte dataset, which breaks TLV parsing in Core and leaves the Thread network broken.

I've amended the migration script to run a data migration and revert to the last-known backup if we see that the current OTBR data file is invalid.

I'm not sure if this is acceptable but I've written a few unit tests using real data and test the migration script's behavior using them. These do not run as part of CI but they are in a tests/ folder. Is this fine to include in the addons repo?

[Copilot]

Pull request overview

This pull request adds automatic recovery functionality to the OTBR (OpenThread Border Router) settings migration script to handle corrupted data files. The PR addresses an issue where corrupted 8-byte datasets were being loaded by the migration script, causing TLV parsing failures and breaking Thread network functionality.

Changes:

• Enhanced error handling in the migration script by replacing assertions with explicit ValueError exceptions
• Added validation logic to detect corrupted OTBR settings files (active dataset < 32 bytes)
• Implemented automatic recovery mechanism that attempts to restore from backup files when corruption is detected
• Added unit tests using real test data to verify the migration script's behavior
• Replaced print statements with proper logging throughout the migration script

Reviewed changes

Copilot reviewed 2 out of 22 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
openthread_border_router/rootfs/usr/local/bin/migrate_otbr_settings.py	Core migration script with enhanced validation, recovery logic, refactored helper functions, and logging
openthread_border_router/tests/test_migration.py	Unit tests for migration script covering both normal and corrupted settings scenarios
openthread_border_router/tests/data/otbr_settings_complex_running/*	Test data files representing a working OTBR configuration with multiple adapters and backups
openthread_border_router/tests/data/otbr_settings_broken/*	Test data files representing a corrupted configuration (incomplete - missing required files)
openthread_border_router/.gitignore	Standard Python project ignore patterns for cache and system files

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[Copilot]

The sys.path manipulation on line 4 modifies the global Python path for the entire test session. This can cause issues if multiple tests run in the same session and have conflicting module names. Consider using a more isolated approach such as importlib or pytest fixtures that handle the path manipulation within the test scope only.

Suggested change

	sys.path.append(str(Path(__file__).parent.parent / "rootfs/usr/local/bin"))
	import pytest
	import shutil
	from unittest.mock import patch
	from migrate_otbr_settings import main, parse_otbr_settings, is_valid_otbr_settings_file
	import importlib.util
	import pytest
	import shutil
	from unittest.mock import patch
	_MIGRATE_OTBR_SETTINGS_PATH = (
	Path(__file__).parent.parent / "rootfs/usr/local/bin" / "migrate_otbr_settings.py"
	)
	_spec = importlib.util.spec_from_file_location(
	"migrate_otbr_settings", _MIGRATE_OTBR_SETTINGS_PATH
	)
	if _spec is None or _spec.loader is None:
	raise ImportError(f"Cannot load migrate_otbr_settings from {_MIGRATE_OTBR_SETTINGS_PATH}")
	_migrate_otbr_settings = importlib.util.module_from_spec(_spec)
	_spec.loader.exec_module(_migrate_otbr_settings) # type: ignore[union-attr]
	main = _migrate_otbr_settings.main
	parse_otbr_settings = _migrate_otbr_settings.parse_otbr_settings
	is_valid_otbr_settings_file = _migrate_otbr_settings.is_valid_otbr_settings_file