# OTA Manager Component Specification

**Component ID:** C-OTA-001  
**Component Name:** OTA Manager  
**Version:** 1.0  
**Date:** 2025-02-01  

## 1. Component Overview

### 1.1 Purpose
The OTA Manager is responsible for managing over-the-air firmware updates with A/B partitioning and automatic rollback capabilities. It provides secure, reliable firmware update functionality while ensuring system availability and data integrity throughout the update process.

### 1.2 Scope
- OTA update negotiation and readiness validation
- Secure firmware reception and temporary storage
- Firmware integrity validation and verification
- Safe firmware activation with controlled teardown
- A/B partitioning management with automatic rollback
- Update status reporting and error handling

### 1.3 Responsibilities
- Negotiate OTA updates with Main Hub
- Validate system readiness for firmware updates
- Receive and store firmware images securely
- Verify firmware integrity using cryptographic methods
- Manage A/B partition switching and boot control
- Implement automatic rollback on update failures
- Coordinate with system teardown and reinitialization
- Report update status and results to Main Hub

## 2. Component Architecture

### 2.1 Static View

```mermaid
graph TB
    subgraph "OTA Manager"
        OM[OTA Controller]
        UN[Update Negotiator]
        FR[Firmware Receiver]
        IV[Integrity Validator]
        FA[Firmware Activator]
        RM[Rollback Manager]
        PM[Partition Manager]
    end
    
    subgraph "Storage Layer"
        FS[Firmware Storage]
        PS[Partition Service]
        DP[Data Pool]
    end
    
    subgraph "Security Layer"
        SB[Secure Boot]
        FE[Flash Encryption]
        CV[Certificate Validator]
        CM[Crypto Manager]
    end
    
    OM --> UN
    OM --> FR
    OM --> IV
    OM --> FA
    OM --> RM
    OM --> PM
    
    FR --> FS
    IV --> CV
    IV --> CM
    FA --> PS
    RM --> PM
    FS --> DP
    PS --> SB
    PS --> FE
```

### 2.2 Internal Components

#### 2.2.1 OTA Controller
- Central coordination of OTA operations
- State management for update process
- Error handling and recovery coordination

#### 2.2.2 Update Negotiator
- OTA update negotiation with Main Hub
- System readiness validation
- Update acceptance/rejection logic

#### 2.2.3 Firmware Receiver
- Secure firmware image reception
- Chunked download management
- Progress tracking and resume capability

#### 2.2.4 Integrity Validator
- Firmware integrity verification
- Cryptographic signature validation
- Metadata and compatibility checking

#### 2.2.5 Firmware Activator
- Controlled firmware activation process
- System teardown coordination
- Boot partition management

#### 2.2.6 Rollback Manager
- Automatic rollback detection and execution
- Boot failure recovery
- Rollback status reporting

#### 2.2.7 Partition Manager
- A/B partition management
- Boot partition selection
- Partition health monitoring

## 3. Interfaces

### 3.1 Provided Interfaces

#### 3.1.1 IOTAManager
```cpp
class IOTAManager {
public:
    virtual ~IOTAManager() = default;
    
    // OTA Lifecycle Management
    virtual Result<void> initialize() = 0;
    virtual Result<void> shutdown() = 0;
    virtual OTAState getCurrentState() const = 0;
    
    // Update Negotiation
    virtual Result<void> receiveUpdateNotification(const UpdateNotification& notification) = 0;
    virtual Result<bool> validateSystemReadiness() const = 0;
    virtual Result<void> acceptUpdate(const UpdateAcceptance& acceptance) = 0;
    virtual Result<void> rejectUpdate(const UpdateRejection& rejection) = 0;
    
    // Firmware Reception
    virtual Result<void> startFirmwareDownload(const FirmwareMetadata& metadata) = 0;
    virtual Result<void> receiveFirmwareChunk(const FirmwareChunk& chunk) = 0;
    virtual Result<void> completeFirmwareDownload() = 0;
    virtual DownloadProgress getDownloadProgress() const = 0;
    
    // Firmware Validation and Activation
    virtual Result<void> validateFirmware() = 0;
    virtual Result<void> activateFirmware() = 0;
    virtual Result<void> confirmFirmware() = 0;
    
    // Rollback Management
    virtual Result<void> rollbackFirmware() = 0;
    virtual bool isRollbackAvailable() const = 0;
    virtual RollbackInfo getRollbackInfo() const = 0;
    
    // Status and Information
    virtual OTAStatus getOTAStatus() const = 0;
    virtual FirmwareInfo getCurrentFirmwareInfo() const = 0;
    virtual FirmwareInfo getPendingFirmwareInfo() const = 0;
    virtual std::vector<OTAEvent> getOTAHistory() const = 0;
};
```

#### 3.1.2 IUpdateController
```cpp
class IUpdateController {
public:
    virtual ~IUpdateController() = default;
    virtual Result<void> initiateUpdate(const UpdateRequest& request) = 0;
    virtual Result<void> cancelUpdate() = 0;
    virtual Result<void> pauseUpdate() = 0;
    virtual Result<void> resumeUpdate() = 0;
    virtual UpdateStatus getUpdateStatus() const = 0;
};
```

#### 3.1.3 IFirmwareStatus
```cpp
class IFirmwareStatus {
public:
    virtual ~IFirmwareStatus() = default;
    virtual FirmwareVersion getCurrentVersion() const = 0;
    virtual FirmwareVersion getPendingVersion() const = 0;
    virtual PartitionInfo getActivePartition() const = 0;
    virtual PartitionInfo getInactivePartition() const = 0;
    virtual bool isPendingFirmwareValid() const = 0;
};
```

### 3.2 Required Interfaces

#### 3.2.1 ICommunicationManager
- Reception of OTA notifications and firmware data
- Transmission of OTA status and acknowledgments
- Secure communication channel management

#### 3.2.2 ISystemStateManager
- System state management for OTA operations
- Controlled teardown initiation
- System reinitialization coordination

#### 3.2.3 IPersistenceManager
- Firmware image storage and retrieval
- OTA metadata persistence
- Backup and recovery data management

#### 3.2.4 ISecurityManager
- Firmware signature verification
- Certificate validation
- Cryptographic operations

#### 3.2.5 IDiagnosticsManager
- OTA event logging and reporting
- Error condition reporting
- Performance metrics collection

## 4. Dynamic View

### 4.1 OTA Negotiation Sequence

```mermaid
sequenceDiagram
    participant MH as Main Hub
    participant CM as Communication Manager
    participant OM as OTA Manager
    participant UN as Update Negotiator
    participant STM as System State Manager
    
    MH->>CM: otaUpdateAvailable(firmware_info)
    CM->>OM: receiveUpdateNotification(firmware_info)
    OM->>UN: negotiateUpdate(firmware_info)
    UN->>STM: checkSystemReadiness()
    STM-->>UN: system_status
    UN->>UN: validateUpdateCompatibility()
    
    alt System Ready and Compatible
        UN-->>OM: negotiation_success
        OM->>STM: transitionToOTAState()
        STM-->>OM: state_transition_complete
        OM->>CM: sendOTAAcceptance()
        CM->>MH: otaAccepted()
    else System Not Ready or Incompatible
        UN-->>OM: negotiation_failed(reason)
        OM->>CM: sendOTARejection(reason)
        CM->>MH: otaRejected(reason)
    end
```

### 4.2 Firmware Download and Validation Sequence

```mermaid
sequenceDiagram
    participant MH as Main Hub
    participant FR as Firmware Receiver
    participant FS as Firmware Storage
    participant IV as Integrity Validator
    participant CV as Certificate Validator
    participant CM as Crypto Manager
    
    MH->>FR: startFirmwareTransfer(metadata)
    FR->>FS: initializeFirmwareStorage(metadata)
    FS-->>FR: storage_initialized
    
    loop Firmware Chunks
        MH->>FR: sendFirmwareChunk(chunk_data, chunk_id)
        FR->>FS: storeFirmwareChunk(chunk_data, chunk_id)
        FS-->>FR: chunk_stored
        FR->>FR: updateProgress()
    end
    
    FR->>IV: validateFirmwareIntegrity()
    IV->>FS: calculateSHA256Hash()
    FS-->>IV: calculated_hash
    IV->>IV: compareWithExpectedHash()
    
    alt Hash Valid
        IV->>CV: validateFirmwareSignature()
        CV->>CM: verifySignature(firmware, signature)
        CM-->>CV: signature_valid
        
        alt Signature Valid
            CV-->>IV: signature_validation_success
            IV-->>FR: firmware_validated
        else Signature Invalid
            CV-->>IV: signature_validation_failed
            IV-->>FR: validation_failed
        end
    else Hash Invalid
        IV-->>FR: integrity_check_failed
    end
```

### 4.3 Firmware Activation and Rollback Sequence

```mermaid
sequenceDiagram
    participant OM as OTA Manager
    participant FA as Firmware Activator
    participant PM as Partition Manager
    participant STM as System State Manager
    participant RM as Rollback Manager
    participant SB as Secure Boot
    
    OM->>FA: activateFirmware()
    FA->>STM: initiateTeardown()
    STM->>STM: executeTeardown()
    STM-->>FA: teardown_complete
    
    FA->>PM: flashFirmwareToInactivePartition()
    PM->>PM: writeFirmwareToPartition()
    PM-->>FA: flash_complete
    
    FA->>PM: setBootPartition(inactive_partition)
    PM->>PM: updatePartitionTable()
    PM-->>FA: boot_partition_set
    
    FA->>FA: rebootSystem()
    
    Note over FA: System Reboots
    
    alt Boot Success
        SB->>SB: validateNewFirmware()
        SB->>FA: firmwareBootSuccessful()
        FA->>FA: startConfirmationTimer()
        FA->>OM: sendHealthReport()
        
        alt Confirmation Received
            OM->>RM: confirmFirmwareStability()
            RM->>PM: markPartitionValid()
        else Confirmation Timeout
            RM->>PM: rollbackToPreviousPartition()
            PM->>PM: setBootPartition(previous_partition)
            PM->>PM: rebootSystem()
        end
    else Boot Failure
        SB->>RM: bootFailureDetected()
        RM->>PM: rollbackToPreviousPartition()
        PM->>PM: setBootPartition(previous_partition)
        PM->>PM: rebootSystem()
    end
```

## 5. OTA State Management

### 5.1 OTA States
```cpp
enum class OTAState {
    IDLE,                    // No OTA operation in progress
    NEGOTIATING,            // Negotiating update with Main Hub
    DOWNLOADING,            // Downloading firmware image
    VALIDATING,             // Validating firmware integrity
    READY_TO_ACTIVATE,      // Ready for firmware activation
    ACTIVATING,             // Activating new firmware
    CONFIRMING,             // Confirming firmware stability
    ROLLING_BACK,           // Rolling back to previous firmware
    COMPLETED,              // OTA operation completed successfully
    FAILED,                 // OTA operation failed
    CANCELLED               // OTA operation cancelled
};
```

### 5.2 State Transitions
```cpp
class OTAStateMachine {
public:
    bool isValidTransition(OTAState from, OTAState to) const;
    Result<void> transitionTo(OTAState new_state);
    OTAState getCurrentState() const;
    std::vector<OTAState> getValidNextStates() const;
    
private:
    OTAState current_state_;
    std::map<OTAState, std::vector<OTAState>> valid_transitions_;
};
```

## 6. A/B Partitioning

### 6.1 Partition Layout
```cpp
struct PartitionLayout {
    // Boot partitions
    Partition bootloader;      // ~32KB - Initial boot code
    Partition partition_table; // ~4KB - Partition table
    Partition factory;         // Optional - Factory/rescue firmware
    
    // Application partitions (A/B)
    Partition ota_0;          // 3.5MB - Primary application slot
    Partition ota_1;          // 3.5MB - Secondary application slot
    
    // Data partitions
    Partition nvs;            // 64KB - Non-volatile storage
    Partition phy_init;       // ~4KB - PHY initialization data
    Partition coredump;       // 64KB - Core dump storage
};
```

### 6.2 Partition Management
```cpp
class PartitionManager {
public:
    Result<void> initialize();
    
    // Partition Information
    PartitionInfo getActivePartition() const;
    PartitionInfo getInactivePartition() const;
    std::vector<PartitionInfo> getAllPartitions() const;
    
    // Partition Operations
    Result<void> setBootPartition(PartitionId partition_id);
    Result<void> markPartitionValid(PartitionId partition_id);
    Result<void> markPartitionInvalid(PartitionId partition_id);
    
    // Firmware Operations
    Result<void> writeFirmwareToPartition(PartitionId partition_id, 
                                         const FirmwareImage& firmware);
    Result<void> eraseFirmwarePartition(PartitionId partition_id);
    Result<bool> validatePartitionFirmware(PartitionId partition_id);
    
    // Rollback Support
    Result<void> rollbackToPartition(PartitionId partition_id);
    bool isRollbackAvailable() const;
    PartitionId getPreviousValidPartition() const;
};
```

## 7. Firmware Validation

### 7.1 Validation Methods
```cpp
class FirmwareValidator {
public:
    struct ValidationResult {
        bool is_valid;
        std::vector<ValidationError> errors;
        ValidationMetrics metrics;
    };
    
    // Integrity Validation
    ValidationResult validateIntegrity(const FirmwareImage& firmware) const;
    ValidationResult validateSHA256Hash(const FirmwareImage& firmware, 
                                       const std::string& expected_hash) const;
    
    // Signature Validation
    ValidationResult validateSignature(const FirmwareImage& firmware,
                                      const DigitalSignature& signature) const;
    ValidationResult validateCertificateChain(const CertificateChain& chain) const;
    
    // Compatibility Validation
    ValidationResult validateCompatibility(const FirmwareMetadata& metadata) const;
    ValidationResult validateHardwareCompatibility(const HardwareRequirements& requirements) const;
    ValidationResult validateVersionCompatibility(const VersionInfo& version) const;
    
    // Metadata Validation
    ValidationResult validateMetadata(const FirmwareMetadata& metadata) const;
    ValidationResult validateSize(const FirmwareImage& firmware, size_t expected_size) const;
};
```

### 7.2 Security Validation
- **SHA-256 Hash**: Firmware integrity verification
- **RSA-3072/ECDSA-P256**: Digital signature verification
- **Certificate Chain**: Certificate validation and trust verification
- **Anti-Rollback**: Version downgrade protection
- **Secure Boot**: Boot-time firmware validation

## 8. Rollback Management

### 8.1 Rollback Triggers
```cpp
enum class RollbackTrigger {
    BOOT_FAILURE,           // System failed to boot with new firmware
    HEALTH_CHECK_TIMEOUT,   // No health report within confirmation window
    APPLICATION_CRASH,      // Application crash during confirmation period
    MANUAL_ROLLBACK,        // Manual rollback command from Main Hub
    VALIDATION_FAILURE,     // Post-boot validation failure
    WATCHDOG_TIMEOUT        // Watchdog timeout indicating system hang
};
```

### 8.2 Rollback Process
1. **Failure Detection**: Detect rollback trigger condition
2. **Rollback Decision**: Determine if rollback is appropriate
3. **Partition Switch**: Switch boot partition to previous valid firmware
4. **System Reboot**: Reboot into previous firmware
5. **Rollback Verification**: Verify successful rollback
6. **Status Reporting**: Report rollback event and reason

### 8.3 Rollback Prevention
- **Confirmation Window**: 60-120 seconds for firmware confirmation
- **Health Monitoring**: Continuous health checks during confirmation
- **Graceful Degradation**: Attempt recovery before rollback
- **Rollback Limits**: Prevent infinite rollback loops

## 9. Configuration

### 9.1 OTA Configuration
```cpp
struct OTAConfig {
    // Download Configuration
    size_t chunk_size;                    // Default: 4096 bytes
    std::chrono::seconds download_timeout;
    uint32_t max_retry_attempts;
    
    // Validation Configuration
    bool signature_validation_required;
    bool certificate_validation_required;
    std::vector<std::string> trusted_ca_certificates;
    
    // Activation Configuration
    std::chrono::seconds confirmation_timeout;  // Default: 90 seconds
    bool automatic_rollback_enabled;
    uint32_t max_rollback_attempts;
    
    // Storage Configuration
    std::string firmware_storage_path;
    size_t max_firmware_size;
    bool cleanup_after_activation;
    
    // Security Configuration
    bool secure_download_required;
    EncryptionMethod storage_encryption;
    bool anti_rollback_enabled;
};
```

## 10. Error Handling

### 10.1 Error Categories
- **Network Errors**: Download failures, communication timeouts
- **Storage Errors**: Insufficient space, write failures
- **Validation Errors**: Integrity check failures, signature validation failures
- **Activation Errors**: Partition switching failures, boot failures
- **Rollback Errors**: Rollback process failures

### 10.2 Error Recovery Strategies
- **Retry Logic**: Automatic retry with exponential backoff
- **Graceful Degradation**: Continue operation with current firmware
- **Automatic Rollback**: Rollback on activation failures
- **Error Reporting**: Detailed error reporting to Main Hub
- **Diagnostic Logging**: Comprehensive logging for troubleshooting

## 11. Performance Characteristics

### 11.1 Timing Requirements
- **OTA Negotiation**: < 30 seconds
- **Firmware Download**: Variable based on size and network speed
- **Firmware Validation**: < 60 seconds for typical firmware
- **Firmware Activation**: < 2 minutes including teardown and reboot
- **Total OTA Process**: < 10 minutes end-to-end

### 11.2 Resource Usage
- **Memory**: < 64KB for OTA operations and buffers
- **Storage**: Temporary storage equal to firmware size
- **CPU**: < 10% during download, higher during validation
- **Network**: Adaptive based on available bandwidth

## 12. Security Considerations

### 12.1 Secure Download
- All firmware downloads over encrypted channels (TLS 1.2)
- Firmware integrity verification during download
- Secure temporary storage with encryption

### 12.2 Firmware Validation
- Mandatory cryptographic signature verification
- Certificate chain validation with trusted root CAs
- Anti-rollback protection via eFuse version tracking

### 12.3 Activation Security
- Secure Boot V2 validation of new firmware
- Encrypted partition storage
- Rollback protection against unauthorized downgrades

## 13. Testing Strategy

### 13.1 Unit Tests
- OTA state machine transitions
- Firmware validation algorithms
- Partition management operations
- Error handling and recovery logic

### 13.2 Integration Tests
- End-to-end OTA update process
- Communication with Main Hub
- System teardown and reinitialization
- Rollback scenarios and recovery

### 13.3 System Tests
- OTA updates under various system conditions
- Network interruption and recovery
- Power failure during OTA process
- Security validation and attack resistance

## 14. Dependencies

### 14.1 Internal Dependencies
- Communication Manager for OTA communication
- System State Manager for teardown coordination
- Persistence Manager for firmware storage
- Security Manager for cryptographic operations
- Diagnostics Manager for event logging

### 14.2 External Dependencies
- ESP-IDF OTA APIs and partition management
- mbedTLS for cryptographic operations
- File system support for firmware storage
- Secure Boot and Flash Encryption hardware

## 15. Constraints and Assumptions

### 15.1 Constraints
- OTA process requires system restart
- Firmware size limited by partition size (3.5MB)
- Network connectivity required for firmware download
- Sufficient storage space required for temporary firmware storage

### 15.2 Assumptions
- Reliable network connectivity during download
- Valid firmware signatures and certificates
- Proper A/B partition configuration
- Sufficient system resources for OTA operations
- Main Hub provides valid firmware images and metadata