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Refactor bridge packet handling to use common magic number and size constants

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This commit is contained in:
João Brázio
2025-09-08 11:15:28 +01:00
parent 7fca20475a
commit 1d25c87c57
6 changed files with 40 additions and 37 deletions
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src/helpers/bridges/BridgeBase.h
+20
View File
@@ -21,6 +21,26 @@ class BridgeBase : public AbstractBridge {
public:
virtual ~BridgeBase() = default;
/**
* @brief Common magic number used by all bridge implementations for packet identification
*
* This magic number is placed at the beginning of bridge packets to identify
* them as mesh bridge packets and provide frame synchronization.
*/
static constexpr uint16_t BRIDGE_PACKET_MAGIC = 0xC03E;
/**
* @brief Common field sizes used by bridge implementations
*
* These constants define the size of common packet fields used across bridges.
* BRIDGE_MAGIC_SIZE is used by all bridges for packet identification.
* BRIDGE_LENGTH_SIZE is used by bridges that need explicit length fields (like RS232).
* BRIDGE_CHECKSUM_SIZE is used by all bridges for Fletcher-16 checksums.
*/
static constexpr uint16_t BRIDGE_MAGIC_SIZE = sizeof(BRIDGE_PACKET_MAGIC);
static constexpr uint16_t BRIDGE_LENGTH_SIZE = sizeof(uint16_t);
static constexpr uint16_t BRIDGE_CHECKSUM_SIZE = sizeof(uint16_t);
protected:
/** Packet manager for allocating and queuing mesh packets */
mesh::PacketManager *_mgr;
src/helpers/bridges/ESPNowBridge.cpp
+12 -12
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@@ -66,7 +66,7 @@ void ESPNowBridge::xorCrypt(uint8_t *data, size_t len) {
void ESPNowBridge::onDataRecv(const uint8_t *mac, const uint8_t *data, int32_t len) {
// Ignore packets that are too small to contain header + checksum
if (len < (MAGIC_HEADER_SIZE + CHECKSUM_SIZE)) {
if (len < (BRIDGE_MAGIC_SIZE + BRIDGE_CHECKSUM_SIZE)) {
#if MESH_PACKET_LOGGING
Serial.printf("%s: ESPNOW BRIDGE: RX packet too small, len=%d\n", getLogDateTime(), len);
#endif
@@ -83,7 +83,7 @@ void ESPNowBridge::onDataRecv(const uint8_t *mac, const uint8_t *data, int32_t l
// Check packet header magic
uint16_t received_magic = (data[0] << 8) | data[1];
if (received_magic != ESPNOW_HEADER_MAGIC) {
if (received_magic != BRIDGE_PACKET_MAGIC) {
#if MESH_PACKET_LOGGING
Serial.printf("%s: ESPNOW BRIDGE: RX invalid magic 0x%04X\n", getLogDateTime(), received_magic);
#endif
@@ -92,17 +92,17 @@ void ESPNowBridge::onDataRecv(const uint8_t *mac, const uint8_t *data, int32_t l
// Make a copy we can decrypt
uint8_t decrypted[MAX_ESPNOW_PACKET_SIZE];
const size_t encryptedDataLen = len - MAGIC_HEADER_SIZE;
memcpy(decrypted, data + MAGIC_HEADER_SIZE, encryptedDataLen);
const size_t encryptedDataLen = len - BRIDGE_MAGIC_SIZE;
memcpy(decrypted, data + BRIDGE_MAGIC_SIZE, encryptedDataLen);
// Try to decrypt (checksum + payload)
xorCrypt(decrypted, encryptedDataLen);
// Validate checksum
uint16_t received_checksum = (decrypted[0] << 8) | decrypted[1];
const size_t payloadLen = encryptedDataLen - CHECKSUM_SIZE;
const size_t payloadLen = encryptedDataLen - BRIDGE_CHECKSUM_SIZE;
if (!validateChecksum(decrypted + CHECKSUM_SIZE, payloadLen, received_checksum)) {
if (!validateChecksum(decrypted + BRIDGE_CHECKSUM_SIZE, payloadLen, received_checksum)) {
// Failed to decrypt - likely from a different network
#if MESH_PACKET_LOGGING
Serial.printf("%s: ESPNOW BRIDGE: RX checksum mismatch, rcv=0x%04X\n", getLogDateTime(),
@@ -119,7 +119,7 @@ void ESPNowBridge::onDataRecv(const uint8_t *mac, const uint8_t *data, int32_t l
mesh::Packet *pkt = _instance->_mgr->allocNew();
if (!pkt) return;
if (pkt->readFrom(decrypted + CHECKSUM_SIZE, payloadLen)) {
if (pkt->readFrom(decrypted + BRIDGE_CHECKSUM_SIZE, payloadLen)) {
_instance->onPacketReceived(pkt);
} else {
_instance->_mgr->free(pkt);
@@ -161,11 +161,11 @@ void ESPNowBridge::onPacketTransmitted(mesh::Packet *packet) {
uint8_t buffer[MAX_ESPNOW_PACKET_SIZE];
// Write magic header (2 bytes)
buffer[0] = (ESPNOW_HEADER_MAGIC >> 8) & 0xFF;
buffer[1] = ESPNOW_HEADER_MAGIC & 0xFF;
buffer[0] = (BRIDGE_PACKET_MAGIC >> 8) & 0xFF;
buffer[1] = BRIDGE_PACKET_MAGIC & 0xFF;
// Write packet payload starting after magic header and checksum
const size_t packetOffset = MAGIC_HEADER_SIZE + CHECKSUM_SIZE;
const size_t packetOffset = BRIDGE_MAGIC_SIZE + BRIDGE_CHECKSUM_SIZE;
memcpy(buffer + packetOffset, sizingBuffer, meshPacketLen);
// Calculate and add checksum (only of the payload)
@@ -174,10 +174,10 @@ void ESPNowBridge::onPacketTransmitted(mesh::Packet *packet) {
buffer[3] = checksum & 0xFF; // Low byte
// Encrypt payload and checksum (not including magic header)
xorCrypt(buffer + MAGIC_HEADER_SIZE, meshPacketLen + CHECKSUM_SIZE);
xorCrypt(buffer + BRIDGE_MAGIC_SIZE, meshPacketLen + BRIDGE_CHECKSUM_SIZE);
// Total packet size: magic header + checksum + payload
const size_t totalPacketSize = MAGIC_HEADER_SIZE + CHECKSUM_SIZE + meshPacketLen;
const size_t totalPacketSize = BRIDGE_MAGIC_SIZE + BRIDGE_CHECKSUM_SIZE + meshPacketLen;
// Broadcast using ESP-NOW
uint8_t broadcastAddress[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
src/helpers/bridges/ESPNowBridge.h
+1 -8
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@@ -65,14 +65,7 @@ private:
/**
* Size constants for packet parsing
*/
static const size_t MAGIC_HEADER_SIZE = 2;
static const size_t CHECKSUM_SIZE = 2;
static const size_t MAX_PAYLOAD_SIZE = MAX_ESPNOW_PACKET_SIZE - (MAGIC_HEADER_SIZE + CHECKSUM_SIZE);
/**
* Magic bytes to identify ESPNowBridge packets
*/
static const uint16_t ESPNOW_HEADER_MAGIC = 0xC03E;
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];
src/helpers/bridges/RS232Bridge.cpp
+5 -5
View File
@@ -52,8 +52,8 @@ void RS232Bridge::onPacketTransmitted(mesh::Packet *packet) {
}
// Build packet header
buffer[0] = (SERIAL_PKT_MAGIC >> 8) & 0xFF; // Magic high byte
buffer[1] = SERIAL_PKT_MAGIC & 0xFF; // Magic low byte
buffer[0] = (BRIDGE_PACKET_MAGIC >> 8) & 0xFF; // Magic high byte
buffer[1] = BRIDGE_PACKET_MAGIC & 0xFF; // Magic low byte
buffer[2] = (len >> 8) & 0xFF; // Length high byte
buffer[3] = len & 0xFF; // Length low byte
@@ -77,14 +77,14 @@ void RS232Bridge::loop() {
if (_rx_buffer_pos < 2) {
// Waiting for magic word
if ((_rx_buffer_pos == 0 && b == ((SERIAL_PKT_MAGIC >> 8) & 0xFF)) ||
(_rx_buffer_pos == 1 && b == (SERIAL_PKT_MAGIC & 0xFF))) {
if ((_rx_buffer_pos == 0 && b == ((BRIDGE_PACKET_MAGIC >> 8) & 0xFF)) ||
(_rx_buffer_pos == 1 && b == (BRIDGE_PACKET_MAGIC & 0xFF))) {
_rx_buffer[_rx_buffer_pos++] = b;
} else {
// Invalid magic byte, reset and start over
_rx_buffer_pos = 0;
// Check if this byte could be the start of a new magic word
if (b == ((SERIAL_PKT_MAGIC >> 8) & 0xFF)) {
if (b == ((BRIDGE_PACKET_MAGIC >> 8) & 0xFF)) {
_rx_buffer[_rx_buffer_pos++] = b;
}
}
src/helpers/bridges/RS232Bridge.h
+1 -11
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@@ -113,21 +113,11 @@ private:
* Total overhead: 6 bytes
*/
/** Magic number to identify start of RS232Bridge packets */
static constexpr uint16_t SERIAL_PKT_MAGIC = 0xC03E;
/**
* Size constants for packet parsing and construction
*/
static constexpr uint16_t MAGIC_HEADER_SIZE = 2;
static constexpr uint16_t LENGTH_FIELD_SIZE = 2;
static constexpr uint16_t CHECKSUM_SIZE = 2;
/**
* @brief The total overhead of the serial protocol in bytes.
* Includes: MAGIC_WORD (2) + LENGTH (2) + CHECKSUM (2) = 6 bytes
*/
static constexpr uint16_t SERIAL_OVERHEAD = MAGIC_HEADER_SIZE + LENGTH_FIELD_SIZE + CHECKSUM_SIZE;
static constexpr uint16_t SERIAL_OVERHEAD = BRIDGE_MAGIC_SIZE + BRIDGE_LENGTH_SIZE + BRIDGE_CHECKSUM_SIZE;
/**
* @brief The maximum size of a complete packet on the serial line.
variants/lilygo_tlora_v2_1/platformio.ini
+1 -1
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@@ -198,7 +198,7 @@ build_flags =
-D MAX_NEIGHBOURS=8
-D WITH_ESPNOW_BRIDGE=1
-D WITH_ESPNOW_BRIDGE_SECRET='"shared-secret"'
; -D MESH_PACKET_LOGGING=1
-D MESH_PACKET_LOGGING=1
; -D MESH_DEBUG=1
; -D CORE_DEBUG_LEVEL=3
lib_deps =