mirror of https://github.com/meshcore-dev/MeshCore
João Brázio
9 months ago
6 changed files with 512 additions and 61 deletions
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#include "ESPNowBridge.h" |
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#include <RTClib.h> |
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#include <WiFi.h> |
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#include <esp_wifi.h> |
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#ifdef WITH_ESPNOW_BRIDGE |
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// Static member to handle callbacks
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ESPNowBridge *ESPNowBridge::_instance = nullptr; |
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// Static callback wrappers
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void ESPNowBridge::recv_cb(const uint8_t *mac, const uint8_t *data, int len) { |
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if (_instance) { |
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_instance->onDataRecv(mac, data, len); |
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} |
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} |
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void ESPNowBridge::send_cb(const uint8_t *mac, esp_now_send_status_t status) { |
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if (_instance) { |
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_instance->onDataSent(mac, status); |
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} |
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} |
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// Fletcher16 checksum calculation
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static uint16_t fletcher16(const uint8_t *data, size_t len) { |
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uint16_t sum1 = 0; |
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uint16_t sum2 = 0; |
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while (len--) { |
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sum1 = (sum1 + *data++) % 255; |
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sum2 = (sum2 + sum1) % 255; |
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} |
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return (sum2 << 8) | sum1; |
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} |
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ESPNowBridge::ESPNowBridge(mesh::PacketManager *mgr, mesh::RTCClock *rtc) |
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: _mgr(mgr), _rtc(rtc), _rx_buffer_pos(0) { |
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_instance = this; |
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} |
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void ESPNowBridge::begin() { |
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// Initialize WiFi in station mode
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WiFi.mode(WIFI_STA); |
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// Initialize ESP-NOW
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if (esp_now_init() != ESP_OK) { |
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Serial.printf("%s: ESPNOW BRIDGE: Error initializing ESP-NOW\n", getLogDateTime()); |
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return; |
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} |
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// Register callbacks
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esp_now_register_recv_cb(recv_cb); |
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esp_now_register_send_cb(send_cb); |
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// Add broadcast peer
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esp_now_peer_info_t peerInfo = {}; |
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memset(&peerInfo, 0, sizeof(peerInfo)); |
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memset(peerInfo.peer_addr, 0xFF, ESP_NOW_ETH_ALEN); // Broadcast address
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peerInfo.channel = 0; |
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peerInfo.encrypt = false; |
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if (esp_now_add_peer(&peerInfo) != ESP_OK) { |
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Serial.printf("%s: ESPNOW BRIDGE: Failed to add broadcast peer\n", getLogDateTime()); |
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return; |
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} |
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} |
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void ESPNowBridge::loop() { |
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// Nothing to do here - ESP-NOW is callback based
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} |
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void ESPNowBridge::xorCrypt(uint8_t *data, size_t len) { |
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size_t keyLen = strlen(_secret); |
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for (size_t i = 0; i < len; i++) { |
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data[i] ^= _secret[i % keyLen]; |
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} |
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} |
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void ESPNowBridge::onDataRecv(const uint8_t *mac, const uint8_t *data, int len) { |
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// Ignore packets that are too small
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if (len < 3) { |
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#if MESH_PACKET_LOGGING |
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Serial.printf("%s: ESPNOW BRIDGE: RX packet too small, len=%d\n", getLogDateTime(), len); |
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#endif |
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return; |
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} |
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// Check packet header magic
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if (data[0] != ESPNOW_HEADER_MAGIC) { |
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#if MESH_PACKET_LOGGING |
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Serial.printf("%s: ESPNOW BRIDGE: RX invalid magic 0x%02X\n", getLogDateTime(), data[0]); |
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#endif |
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return; |
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} |
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// Make a copy we can decrypt
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uint8_t decrypted[MAX_ESPNOW_PACKET_SIZE]; |
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memcpy(decrypted, data + 1, len - 1); // Skip magic byte
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// Try to decrypt
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xorCrypt(decrypted, len - 1); |
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// Validate checksum
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uint16_t received_checksum = (decrypted[0] << 8) | decrypted[1]; |
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uint16_t calculated_checksum = fletcher16(decrypted + 2, len - 3); |
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if (received_checksum != calculated_checksum) { |
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// Failed to decrypt - likely from a different network
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#if MESH_PACKET_LOGGING |
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Serial.printf("%s: ESPNOW BRIDGE: RX checksum mismatch, rcv=0x%04X calc=0x%04X\n", getLogDateTime(), |
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received_checksum, calculated_checksum); |
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#endif |
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return; |
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} |
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#if MESH_PACKET_LOGGING |
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Serial.printf("%s: ESPNOW BRIDGE: RX, len=%d\n", getLogDateTime(), len - 3); |
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#endif |
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// Create mesh packet
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mesh::Packet *pkt = _instance->_mgr->allocNew(); |
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if (!pkt) return; |
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if (pkt->readFrom(decrypted + 2, len - 3)) { |
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_instance->onPacketReceived(pkt); |
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} else { |
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_instance->_mgr->free(pkt); |
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} |
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} |
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void ESPNowBridge::onDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) { |
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// Could add transmission error handling here if needed
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} |
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void ESPNowBridge::onPacketReceived(mesh::Packet *packet) { |
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if (!_seen_packets.hasSeen(packet)) { |
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_mgr->queueInbound(packet, 0); |
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} else { |
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_mgr->free(packet); |
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} |
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} |
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void ESPNowBridge::onPacketTransmitted(mesh::Packet *packet) { |
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if (!_seen_packets.hasSeen(packet)) { |
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uint8_t buffer[MAX_ESPNOW_PACKET_SIZE]; |
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buffer[0] = ESPNOW_HEADER_MAGIC; |
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// Write packet to buffer starting after magic byte and checksum
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uint16_t len = packet->writeTo(buffer + 3); |
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// Calculate and add checksum
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uint16_t checksum = fletcher16(buffer + 3, len); |
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buffer[1] = (checksum >> 8) & 0xFF; |
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buffer[2] = checksum & 0xFF; |
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// Encrypt payload (not including magic byte)
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xorCrypt(buffer + 1, len + 2); |
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// Broadcast using ESP-NOW
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uint8_t broadcastAddress[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }; |
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esp_err_t result = esp_now_send(broadcastAddress, buffer, len + 3); |
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#if MESH_PACKET_LOGGING |
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if (result == ESP_OK) { |
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Serial.printf("%s: ESPNOW BRIDGE: TX, len=%d\n", getLogDateTime(), len); |
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} else { |
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Serial.printf("%s: ESPNOW BRIDGE: TX FAILED!\n", getLogDateTime()); |
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} |
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#endif |
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} |
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} |
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const char *ESPNowBridge::getLogDateTime() { |
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static char tmp[32]; |
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uint32_t now = _rtc->getCurrentTime(); |
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DateTime dt = DateTime(now); |
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sprintf(tmp, "%02d:%02d:%02d - %d/%d/%d U", dt.hour(), dt.minute(), dt.second(), dt.day(), dt.month(), |
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dt.year()); |
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return tmp; |
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} |
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#endif |
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@ -0,0 +1,170 @@ |
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#pragma once |
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#include "MeshCore.h" |
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#include "esp_now.h" |
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#include "helpers/AbstractBridge.h" |
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#include "helpers/SimpleMeshTables.h" |
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#ifdef WITH_ESPNOW_BRIDGE |
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#ifndef WITH_ESPNOW_BRIDGE_SECRET |
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#error WITH_ESPNOW_BRIDGE_SECRET must be defined to use ESPNowBridge |
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#endif |
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/**
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* @brief Bridge implementation using ESP-NOW protocol for packet transport |
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* |
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* This bridge enables mesh packet transport over ESP-NOW, a connectionless communication |
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* protocol provided by Espressif that allows ESP32 devices to communicate directly |
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* without WiFi router infrastructure. |
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* |
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* Features: |
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* - Broadcast-based communication (all bridges receive all packets) |
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* - Network isolation using XOR encryption with shared secret |
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* - Duplicate packet detection using SimpleMeshTables tracking |
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* - Maximum packet size of 250 bytes (ESP-NOW limitation) |
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* |
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* Packet Structure: |
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* [1 byte] Magic Header (0xAB) - Used to identify ESPNowBridge packets |
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* [2 bytes] Fletcher-16 checksum of encrypted payload (calculated over payload only) |
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* [n bytes] Encrypted payload containing the mesh packet |
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* |
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* The Fletcher-16 checksum is used to validate packet integrity and detect |
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* corrupted or tampered packets. It's calculated over the encrypted payload |
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* and provides a simple but effective way to verify packets are both |
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* uncorrupted and from the same network (since the checksum is calculated |
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* after encryption). |
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* |
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* Configuration: |
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* - Define WITH_ESPNOW_BRIDGE to enable this bridge |
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* - Define WITH_ESPNOW_BRIDGE_SECRET with a string to set the network encryption key |
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* |
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* Network Isolation: |
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* Multiple independent mesh networks can coexist by using different |
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* WITH_ESPNOW_BRIDGE_SECRET values. Packets encrypted with a different key will |
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* fail the checksum validation and be discarded. |
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*/ |
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class ESPNowBridge : public AbstractBridge { |
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private: |
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static ESPNowBridge *_instance; |
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static void recv_cb(const uint8_t *mac, const uint8_t *data, int len); |
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static void send_cb(const uint8_t *mac, esp_now_send_status_t status); |
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/** Packet manager for allocating and queuing mesh packets */ |
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mesh::PacketManager *_mgr; |
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/** RTC clock for timestamping debug messages */ |
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mesh::RTCClock *_rtc; |
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/** Tracks seen packets to prevent loops in broadcast communications */ |
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SimpleMeshTables _seen_packets; |
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/**
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* Maximum ESP-NOW packet size (250 bytes) |
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* This is a hardware limitation of ESP-NOW protocol: |
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* - ESP-NOW header: 20 bytes |
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* - Max payload: 250 bytes |
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* Source: ESP-NOW API documentation |
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*/ |
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static const size_t MAX_ESPNOW_PACKET_SIZE = 250; |
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/**
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* Magic byte to identify ESPNowBridge packets (0xAB) |
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*/ |
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static const uint8_t ESPNOW_HEADER_MAGIC = 0xAB; |
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/** Buffer for receiving ESP-NOW packets */ |
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uint8_t _rx_buffer[MAX_ESPNOW_PACKET_SIZE]; |
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/** Current position in receive buffer */ |
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size_t _rx_buffer_pos; |
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/**
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* Network encryption key from build define |
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* Must be defined with WITH_ESPNOW_BRIDGE_SECRET |
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* Used for XOR encryption to isolate different mesh networks |
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*/ |
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const char *_secret = WITH_ESPNOW_BRIDGE_SECRET; |
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/**
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* Performs XOR encryption/decryption of data |
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* |
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* Uses WITH_ESPNOW_BRIDGE_SECRET as the key in a simple XOR operation. |
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* The same operation is used for both encryption and decryption. |
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* While not cryptographically secure, it provides basic network isolation. |
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* |
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* @param data Pointer to data to encrypt/decrypt |
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* @param len Length of data in bytes |
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*/ |
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void xorCrypt(uint8_t *data, size_t len); |
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/**
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* ESP-NOW receive callback |
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* Called by ESP-NOW when a packet is received |
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* |
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* @param mac Source MAC address |
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* @param data Received data |
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* @param len Length of received data |
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*/ |
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void onDataRecv(const uint8_t *mac, const uint8_t *data, int len); |
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/**
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* ESP-NOW send callback |
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* Called by ESP-NOW after a transmission attempt |
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* |
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* @param mac_addr Destination MAC address |
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* @param status Transmission status |
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*/ |
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void onDataSent(const uint8_t *mac_addr, esp_now_send_status_t status); |
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public: |
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/**
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* Constructs an ESPNowBridge instance |
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* |
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* @param mgr PacketManager for allocating and queuing packets |
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* @param rtc RTCClock for timestamping debug messages |
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*/ |
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ESPNowBridge(mesh::PacketManager *mgr, mesh::RTCClock *rtc); |
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/**
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* Initializes the ESP-NOW bridge |
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* |
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* - Configures WiFi in station mode |
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* - Initializes ESP-NOW protocol |
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* - Registers callbacks |
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* - Sets up broadcast peer |
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*/ |
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void begin() override; |
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/**
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* Main loop handler |
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* ESP-NOW is callback-based, so this is currently empty |
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*/ |
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void loop() override; |
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/**
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* Called when a packet is received via ESP-NOW |
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* Queues the packet for mesh processing if not seen before |
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* |
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* @param packet The received mesh packet |
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*/ |
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void onPacketReceived(mesh::Packet *packet) override; |
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/**
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* Called when a packet needs to be transmitted via ESP-NOW |
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* Encrypts and broadcasts the packet if not seen before |
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* |
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* @param packet The mesh packet to transmit |
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*/ |
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void onPacketTransmitted(mesh::Packet *packet) override; |
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/**
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* Gets formatted date/time string for logging |
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* Format: "HH:MM:SS - DD/MM/YYYY U" |
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* |
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* @return Formatted date/time string |
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*/ |
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const char *getLogDateTime(); |
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}; |
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#endif |
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