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#pragma once
#include "MeshCore.h"
#include "esp_now.h"
#include "helpers/bridges/BridgeBase.h"
#ifdef WITH_ESPNOW_BRIDGE
/**
* @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.
*/
class ESPNowBridge : public BridgeBase {
private:
static ESPNowBridge *_instance;
static void recv_cb(const uint8_t *mac, const uint8_t *data, int32_t len);
static void send_cb(const uint8_t *mac, esp_now_send_status_t status);
/**
* 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
*/
static const size_t MAX_ESPNOW_PACKET_SIZE = 250;
/**
* Size constants for packet parsing
*/
static const size_t MAX_PAYLOAD_SIZE = MAX_ESPNOW_PACKET_SIZE - (BRIDGE_MAGIC_SIZE + BRIDGE_CHECKSUM_SIZE);
/** Buffer for receiving ESP-NOW packets */
uint8_t _rx_buffer[MAX_ESPNOW_PACKET_SIZE];
/** Current position in receive buffer */
size_t _rx_buffer_pos;
/**
* 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
*/
void xorCrypt(uint8_t *data, size_t len);
/**
* 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
*/
void onDataRecv(const uint8_t *mac, const uint8_t *data, int32_t len);
/**
* ESP-NOW send callback
* Called by ESP-NOW after a transmission attempt
*
* @param mac_addr Destination MAC address
* @param status Transmission status
*/
void onDataSent(const uint8_t *mac_addr, esp_now_send_status_t status);
public:
/**
* 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
*/
ESPNowBridge(NodePrefs *prefs, mesh::PacketManager *mgr, mesh::RTCClock *rtc);
/**
* Initializes the ESP-NOW bridge
*
* - Configures WiFi in station mode
* - Initializes ESP-NOW protocol
* - Registers callbacks
* - Sets up broadcast peer
*/
void begin() override;
/**
* Stops the ESP-NOW bridge
*
* - Removes broadcast peer
* - Unregisters callbacks
* - Deinitializes ESP-NOW protocol
* - Turns off WiFi to release radio resources
*/
void end() override;
/**
* Main loop handler
* ESP-NOW is callback-based, so this is currently empty
*/
void loop() override;
/**
* 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
*/
void onPacketReceived(mesh::Packet *packet) override;
/**
* 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
*/
void sendPacket(mesh::Packet *packet) override;
};
#endif
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