1. File locking for config operations
- add_server_to_config() and remove_server_from_config() now use
exclusive file locking (fcntl.LOCK_EX) to prevent race conditions
- Prevents data loss from concurrent modifications
2. Bulk server limit
- Add MAX_BULK_SERVERS = 10 constant
- haproxy_add_servers() now rejects requests exceeding limit
- Prevents potential DoS via large payloads
3. HAProxy command response validation
- Add haproxy_cmd_checked() helper function
- Validates responses for error indicators (No such, not found, etc.)
- State-modifying commands now properly detect and report failures
- Read-only commands continue using haproxy_cmd()
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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