Node / meshcore / MeshCore / files / src / helpers / bridges / ESPNowBridge.h

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Tff7b72#Tff7b72pragma once

Tff7b72#Tff7b72include T8b949e"MeshCore.h"

Tff7b72#Tff7b72include T8b949e"esp_now.h"

Tff7b72#Tff7b72include T8b949e"helpers/bridges/BridgeBase.h"

Tff7b72#Tff7b72ifdef WITH_ESPNOW_BRIDGE

T8b949e/**

* @brief Bridge implementation using ESP-NOW protocol for packet transport

*

* This bridge enables mesh packet transport over ESP-NOW, a connectionless communication

* protocol provided by Espressif that allows ESP32 devices to communicate directly

* without WiFi router infrastructure.

*

* Features:

* - Broadcast-based communication (all bridges receive all packets)

* - Network isolation using XOR encryption with shared secret

* - Duplicate packet detection using SimpleMeshTables tracking

* - Maximum packet size of 250 bytes (ESP-NOW limitation)

*

* Packet Structure:

* [2 bytes] Magic Header - Used to identify ESPNowBridge packets

* [2 bytes] Fletcher-16 checksum of encrypted payload (calculated over payload only)

* [246 bytes max] Encrypted payload containing the mesh packet

*

* The Fletcher-16 checksum is used to validate packet integrity and detect

* corrupted or tampered packets. It's calculated over the encrypted payload

* and provides a simple but effective way to verify packets are both

* uncorrupted and from the same network (since the checksum is calculated

* after encryption).

*

* Configuration:

* - Define WITH_ESPNOW_BRIDGE to enable this bridge

* - Define _prefs->bridge_secret with a string to set the network encryption key

*

* Network Isolation:

* Multiple independent mesh networks can coexist by using different

* _prefs->bridge_secret values. Packets encrypted with a different key will

* fail the checksum validation and be discarded.

*/

Te6edf3class Te6edf3ESPNowBridge Tff7b72: Te6edf3public Te6edf3BridgeBase Tb4b4b4{

Te6edf3privateTff7b72:

Tff7b72static Te6edf3ESPNowBridge Tff7b72*Te6edf3_instanceTb4b4b4;

Tff7b72static Tffa657void Td2a8ffrecv_cbTb4b4b4(Tff7b72const Tffa657uint8_t Tff7b72*Te6edf3macTb4b4b4, Tff7b72const Tffa657uint8_t Tff7b72*Te6edf3dataTb4b4b4, Tffa657int32_t Te6edf3lenTb4b4b4)Tb4b4b4;

Tff7b72static Tffa657void Td2a8ffsend_cbTb4b4b4(Tff7b72const Tffa657uint8_t Tff7b72*Te6edf3macTb4b4b4, Te6edf3esp_now_send_status_t Te6edf3statusTb4b4b4)Tb4b4b4;

T8b949e/**

* ESP-NOW Protocol Structure:

* - ESP-NOW header: 20 bytes (handled by ESP-NOW protocol)

* - ESP-NOW payload: 250 bytes maximum

* Total ESP-NOW packet: 270 bytes

*

* Our Bridge Packet Structure (must fit in ESP-NOW payload):

* - Magic header: 2 bytes

* - Checksum: 2 bytes

* - Available payload: 246 bytes

*/

Tff7b72static Tff7b72const Tffa657size_t Te6edf3MAX_ESPNOW_PACKET_SIZE Tff7b72= T79c0ff250Tb4b4b4;

T8b949e/**

* Size constants for packet parsing

*/

Tff7b72static Tff7b72const Tffa657size_t Te6edf3MAX_PAYLOAD_SIZE Tff7b72= Te6edf3MAX_ESPNOW_PACKET_SIZE Tff7b72- Tb4b4b4(Te6edf3BRIDGE_MAGIC_SIZE Tff7b72+ Te6edf3BRIDGE_CHECKSUM_SIZETb4b4b4)Tb4b4b4;

T8b949e/** Buffer for receiving ESP-NOW packets */

Tffa657uint8_t Te6edf3_rx_bufferTb4b4b4[Te6edf3MAX_ESPNOW_PACKET_SIZETb4b4b4]Tb4b4b4;

T8b949e/** Current position in receive buffer */

Tffa657size_t Te6edf3_rx_buffer_posTb4b4b4;

T8b949e/**

* Performs XOR encryption/decryption of data

* Used to isolate different mesh networks

*

* Uses _prefs->bridge_secret as the key in a simple XOR operation.

* The same operation is used for both encryption and decryption.

* While not cryptographically secure, it provides basic network isolation.

*

* @param data Pointer to data to encrypt/decrypt

* @param len Length of data in bytes

*/

Tffa657void Td2a8ffxorCryptTb4b4b4(Tffa657uint8_t Tff7b72*Te6edf3dataTb4b4b4, Tffa657size_t Te6edf3lenTb4b4b4)Tb4b4b4;

T8b949e/**

* ESP-NOW receive callback

* Called by ESP-NOW when a packet is received

*

* @param mac Source MAC address

* @param data Received data

* @param len Length of received data

*/

Tffa657void Td2a8ffonDataRecvTb4b4b4(Tff7b72const Tffa657uint8_t Tff7b72*Te6edf3macTb4b4b4, Tff7b72const Tffa657uint8_t Tff7b72*Te6edf3dataTb4b4b4, Tffa657int32_t Te6edf3lenTb4b4b4)Tb4b4b4;

T8b949e/**

* ESP-NOW send callback

* Called by ESP-NOW after a transmission attempt

*

* @param mac_addr Destination MAC address

* @param status Transmission status

*/

Tffa657void Td2a8ffonDataSentTb4b4b4(Tff7b72const Tffa657uint8_t Tff7b72*Te6edf3mac_addrTb4b4b4, Te6edf3esp_now_send_status_t Te6edf3statusTb4b4b4)Tb4b4b4;

Te6edf3publicTff7b72:

T8b949e/**

* Constructs an ESPNowBridge instance

*

* @param prefs Node preferences for configuration settings

* @param mgr PacketManager for allocating and queuing packets

* @param rtc RTCClock for timestamping debug messages

*/

Te6edf3ESPNowBridgeTb4b4b4(Te6edf3NodePrefs Tff7b72*Te6edf3prefsTb4b4b4, Te6edf3meshTff7b72:Tff7b72:Te6edf3PacketManager Tff7b72*Te6edf3mgrTb4b4b4, Te6edf3meshTff7b72:Tff7b72:Te6edf3RTCClock Tff7b72*Te6edf3rtcTb4b4b4)Tb4b4b4;

T8b949e/**

* Initializes the ESP-NOW bridge

*

* - Configures WiFi in station mode

* - Initializes ESP-NOW protocol

* - Registers callbacks

* - Sets up broadcast peer

*/

Tffa657void Td2a8ffbeginTb4b4b4(Tb4b4b4) Te6edf3overrideTb4b4b4;

T8b949e/**

* Stops the ESP-NOW bridge

*

* - Removes broadcast peer

* - Unregisters callbacks

* - Deinitializes ESP-NOW protocol

* - Turns off WiFi to release radio resources

*/

Tffa657void Td2a8ffendTb4b4b4(Tb4b4b4) Te6edf3overrideTb4b4b4;

T8b949e/**

* Main loop handler

* ESP-NOW is callback-based, so this is currently empty

*/

Tffa657void Td2a8ffloopTb4b4b4(Tb4b4b4) Te6edf3overrideTb4b4b4;

T8b949e/**

* Called when a packet is received via ESP-NOW

* Queues the packet for mesh processing if not seen before

*

* @param packet The received mesh packet

*/

Tffa657void Td2a8ffonPacketReceivedTb4b4b4(Te6edf3meshTff7b72:Tff7b72:Te6edf3Packet Tff7b72*Te6edf3packetTb4b4b4) Te6edf3overrideTb4b4b4;

T8b949e/**

* Called when a packet needs to be transmitted via ESP-NOW

* Encrypts and broadcasts the packet if not seen before

*

* @param packet The mesh packet to transmit

*/

Tffa657void Td2a8ffsendPacketTb4b4b4(Te6edf3meshTff7b72:Tff7b72:Te6edf3Packet Tff7b72*Te6edf3packetTb4b4b4) Te6edf3overrideTb4b4b4;

Tb4b4b4}Tb4b4b4;

Tff7b72#Tff7b72endif