firmware/src/mesh/udp/UdpMulticastHandler.h

#pragma once
#if HAS_UDP_MULTICAST
#include "configuration.h"
#include "main.h"
#include "mesh/Router.h"

#if HAS_ETHERNET && defined(ARCH_NRF52)
#include "mesh/eth/ethClient.h"
#else
#include <WiFi.h>
#endif

#include <AsyncUDP.h>

#if HAS_ETHERNET && defined(USE_WS5500)
#include <ETHClass2.h>
#define ETH ETH2
#endif // HAS_ETHERNET

#define UDP_MULTICAST_DEFAUL_PORT 4403 // Default port for UDP multicast is same as TCP api server

class UdpMulticastHandler final {
public:
  UdpMulticastHandler() { udpIpAddress = IPAddress(224, 0, 0, 69); }

  void start() {
    if (udp.listenMulticast(udpIpAddress, UDP_MULTICAST_DEFAUL_PORT, 64)) {
#if defined(ARCH_NRF52) || defined(ARCH_PORTDUINO)
      LOG_DEBUG("UDP Listening on IP: %u.%u.%u.%u:%u", udpIpAddress[0], udpIpAddress[1], udpIpAddress[2], udpIpAddress[3], UDP_MULTICAST_DEFAUL_PORT);
#else
      LOG_DEBUG("UDP Listening on IP: %s", WiFi.localIP().toString().c_str());
#endif
      udp.onPacket([this](AsyncUDPPacket packet) { onReceive(packet); });
    } else {
      LOG_DEBUG("Failed to listen on UDP");
    }
  }

  void onReceive(AsyncUDPPacket packet) {
    size_t packetLength = packet.length();
#if defined(ARCH_NRF52)
    IPAddress ip = packet.remoteIP();
    LOG_DEBUG("UDP broadcast from: %u.%u.%u.%u, len=%u", ip[0], ip[1], ip[2], ip[3], packetLength);
#elif !defined(ARCH_PORTDUINO)
    // FIXME(PORTDUINO): arduino lacks IPAddress::toString()
    LOG_DEBUG("UDP broadcast from: %s, len=%u", packet.remoteIP().toString().c_str(), packetLength);
#endif
    meshtastic_MeshPacket mp;
    LOG_DEBUG("Decoding MeshPacket from UDP len=%u", packetLength);
    bool isPacketDecoded = pb_decode_from_bytes(packet.data(), packetLength, &meshtastic_MeshPacket_msg, &mp);
    if (isPacketDecoded && router && mp.which_payload_variant == meshtastic_MeshPacket_encrypted_tag) {
      mp.transport_mechanism = meshtastic_MeshPacket_TransportMechanism_TRANSPORT_MULTICAST_UDP;
      mp.pki_encrypted = false;
      mp.public_key.size = 0;
      memset(mp.public_key.bytes, 0, sizeof(mp.public_key.bytes));
      UniquePacketPoolPacket p = packetPool.allocUniqueCopy(mp);
      // Unset received SNR/RSSI
      p->rx_snr = 0;
      p->rx_rssi = 0;
      router->enqueueReceivedMessage(p.release());
    }
  }

  bool onSend(const meshtastic_MeshPacket *mp) {
    if (!mp || !udp) {
      return false;
    }
#if defined(ARCH_NRF52)
    if (!isEthernetAvailable()) {
      return false;
    }
#elif !defined(ARCH_PORTDUINO)
    if (WiFi.status() != WL_CONNECTED) {
      return false;
    }
#endif
    if (mp->transport_mechanism == meshtastic_MeshPacket_TransportMechanism_TRANSPORT_MULTICAST_UDP) {
      LOG_ERROR("Attempt to send UDP sourced packet over UDP");
    }
    LOG_DEBUG("Broadcasting packet over UDP (id=%u)", mp->id);
    uint8_t buffer[meshtastic_MeshPacket_size];
    size_t encodedLength = pb_encode_to_bytes(buffer, sizeof(buffer), &meshtastic_MeshPacket_msg, mp);
    udp.writeTo(buffer, encodedLength, udpIpAddress, UDP_MULTICAST_DEFAUL_PORT);
    return true;
  }

private:
  IPAddress udpIpAddress;
  AsyncUDP udp;
};
#endif // HAS_UDP_MULTICAST