MeshCoreTel-firmware/examples/simple_room_server/MyMesh.cpp

#include "MyMesh.h"

#define REPLY_DELAY_MILLIS          1500
#define PUSH_NOTIFY_DELAY_MILLIS    2000
#define SYNC_PUSH_INTERVAL          1200

#define PUSH_ACK_TIMEOUT_FLOOD      12000
#define PUSH_TIMEOUT_BASE           4000
#define PUSH_ACK_TIMEOUT_FACTOR     2000

#define POST_SYNC_DELAY_SECS        6

#define FIRMWARE_VER_LEVEL       1

#define REQ_TYPE_GET_STATUS         0x01 // same as _GET_STATS
#define REQ_TYPE_KEEP_ALIVE         0x02
#define REQ_TYPE_GET_TELEMETRY_DATA 0x03
#define REQ_TYPE_GET_ACCESS_LIST    0x05

#define RESP_SERVER_LOGIN_OK        0 // response to ANON_REQ

#define LAZY_CONTACTS_WRITE_DELAY    5000

struct ServerStats {
  uint16_t batt_milli_volts;
  uint16_t curr_tx_queue_len;
  int16_t noise_floor;
  int16_t last_rssi;
  uint32_t n_packets_recv;
  uint32_t n_packets_sent;
  uint32_t total_air_time_secs;
  uint32_t total_up_time_secs;
  uint32_t n_sent_flood, n_sent_direct;
  uint32_t n_recv_flood, n_recv_direct;
  uint16_t err_events; // was 'n_full_events'
  int16_t last_snr;    // x 4
  uint16_t n_direct_dups, n_flood_dups;
  uint16_t n_posted, n_post_push;
};

void MyMesh::addPost(ClientInfo *client, const char *postData) {
  // TODO: suggested postData format: <title>/<descrption>
  posts[next_post_idx].author = client->id; // add to cyclic queue
  StrHelper::strncpy(posts[next_post_idx].text, postData, MAX_POST_TEXT_LEN);

  posts[next_post_idx].post_timestamp = getRTCClock()->getCurrentTimeUnique();
  next_post_idx = (next_post_idx + 1) % MAX_UNSYNCED_POSTS;

  next_push = futureMillis(PUSH_NOTIFY_DELAY_MILLIS);
  _num_posted++; // stats
}

void MyMesh::pushPostToClient(ClientInfo *client, PostInfo &post) {
  int len = 0;
  memcpy(&reply_data[len], &post.post_timestamp, 4);
  len += 4; // this is a PAST timestamp... but should be accepted by client

  uint8_t attempt;
  getRNG()->random(&attempt, 1); // need this for re-tries, so packet hash (and ACK) will be different
  reply_data[len++] = (TXT_TYPE_SIGNED_PLAIN << 2) | (attempt & 3); // 'signed' plain text

  // encode prefix of post.author.pub_key
  memcpy(&reply_data[len], post.author.pub_key, 4);
  len += 4; // just first 4 bytes

  int text_len = strlen(post.text);
  memcpy(&reply_data[len], post.text, text_len);
  len += text_len;

  // calc expected ACK reply
  mesh::Utils::sha256((uint8_t *)&client->extra.room.pending_ack, 4, reply_data, len, client->id.pub_key, PUB_KEY_SIZE);
  client->extra.room.push_post_timestamp = post.post_timestamp;

  auto reply = createDatagram(PAYLOAD_TYPE_TXT_MSG, client->id, client->shared_secret, reply_data, len);
  if (reply) {
    if (client->out_path_len == OUT_PATH_UNKNOWN) {
      unsigned long delay_millis = 0;
      sendFlood(reply, delay_millis, _prefs.path_hash_mode + 1);
      client->extra.room.ack_timeout = futureMillis(PUSH_ACK_TIMEOUT_FLOOD);
    } else {
      sendDirect(reply, client->out_path, client->out_path_len);

      uint8_t path_hash_count = client->out_path_len & 63;
      client->extra.room.ack_timeout = futureMillis(PUSH_TIMEOUT_BASE + PUSH_ACK_TIMEOUT_FACTOR * (path_hash_count + 1));
    }
    _num_post_pushes++; // stats
  } else {
    client->extra.room.pending_ack = 0;
    MESH_DEBUG_PRINTLN("Unable to push post to client");
  }
}

uint8_t MyMesh::getUnsyncedCount(ClientInfo *client) {
  uint8_t count = 0;
  for (int k = 0; k < MAX_UNSYNCED_POSTS; k++) {
    if (posts[k].post_timestamp > client->extra.room.sync_since // is new post for this Client?
        && !posts[k].author.matches(client->id)) {   // don't push posts to the author
      count++;
    }
  }
  return count;
}

bool MyMesh::processAck(const uint8_t *data) {
  for (int i = 0; i < acl.getNumClients(); i++) {
    auto client = acl.getClientByIdx(i);
    if (client->extra.room.pending_ack && memcmp(data, &client->extra.room.pending_ack, 4) == 0) { // got an ACK from Client!
      client->extra.room.pending_ack = 0; // clear this, so next push can happen
      client->extra.room.push_failures = 0;
      client->extra.room.sync_since = client->extra.room.push_post_timestamp; // advance Client's SINCE timestamp, to sync next post
      return true;
    }
  }
  return false;
}

mesh::Packet *MyMesh::createSelfAdvert() {
  uint8_t app_data[MAX_ADVERT_DATA_SIZE];
  uint8_t app_data_len = _cli.buildAdvertData(ADV_TYPE_ROOM, app_data);

  return createAdvert(self_id, app_data, app_data_len);
}

File MyMesh::openAppend(const char *fname) {
#if defined(NRF52_PLATFORM)
  return _fs->open(fname, FILE_O_WRITE);
#elif defined(RP2040_PLATFORM)
  return _fs->open(fname, "a");
#else
  return _fs->open(fname, "a", true);
#endif
}

int MyMesh::handleRequest(ClientInfo *sender, uint32_t sender_timestamp, uint8_t *payload,
                          size_t payload_len) {
  // uint32_t now = getRTCClock()->getCurrentTimeUnique();
  // memcpy(reply_data, &now, 4);   // response packets always prefixed with timestamp
  memcpy(reply_data, &sender_timestamp, 4); // reflect sender_timestamp back in response packet (kind of like a 'tag')

  if (payload[0] == REQ_TYPE_GET_STATUS) {
    ServerStats stats;
    stats.batt_milli_volts = board.getBattMilliVolts();
    stats.curr_tx_queue_len = _mgr->getOutboundTotal();
    stats.noise_floor = (int16_t)_radio->getNoiseFloor();
    stats.last_rssi = (int16_t)radio_driver.getLastRSSI();
    stats.n_packets_recv = radio_driver.getPacketsRecv();
    stats.n_packets_sent = radio_driver.getPacketsSent();
    stats.total_air_time_secs = getTotalAirTime() / 1000;
    stats.total_up_time_secs = uptime_millis / 1000;
    stats.n_sent_flood = getNumSentFlood();
    stats.n_sent_direct = getNumSentDirect();
    stats.n_recv_flood = getNumRecvFlood();
    stats.n_recv_direct = getNumRecvDirect();
    stats.err_events = _err_flags;
    stats.last_snr = (int16_t)(radio_driver.getLastSNR() * 4);
    stats.n_direct_dups = ((SimpleMeshTables *)getTables())->getNumDirectDups();
    stats.n_flood_dups = ((SimpleMeshTables *)getTables())->getNumFloodDups();
    stats.n_posted = _num_posted;
    stats.n_post_push = _num_post_pushes;

    memcpy(&reply_data[4], &stats, sizeof(stats));
    return 4 + sizeof(stats);
  }
  if (payload[0] == REQ_TYPE_GET_TELEMETRY_DATA) {
    uint8_t perm_mask = ~(payload[1]); // NEW: first reserved byte (of 4), is now inverse mask to apply to permissions

    telemetry.reset();
    telemetry.addVoltage(TELEM_CHANNEL_SELF, (float)board.getBattMilliVolts() / 1000.0f);
    // query other sensors -- target specific
    if ((sender->permissions & PERM_ACL_ROLE_MASK) == PERM_ACL_GUEST) {
      perm_mask = 0x00;  // just base telemetry allowed
    }
    sensors.querySensors(perm_mask, telemetry);

    // This default temperature will be overridden by external sensors (if any)
    float temperature = board.getMCUTemperature();
    if(!isnan(temperature)) { // Supported boards with built-in temperature sensor. ESP32-C3 may return NAN
      telemetry.addTemperature(TELEM_CHANNEL_SELF, temperature); // Built-in MCU Temperature
    }

    uint8_t tlen = telemetry.getSize();
    memcpy(&reply_data[4], telemetry.getBuffer(), tlen);
    return 4 + tlen; // reply_len
  }
  if (payload[0] == REQ_TYPE_GET_ACCESS_LIST && sender->isAdmin()) {
    uint8_t res1 = payload[1];   // reserved for future  (extra query params)
    uint8_t res2 = payload[2];
    if (res1 == 0 && res2 == 0) {
      uint8_t ofs = 4;
      for (int i = 0; i < acl.getNumClients() && ofs + 7 <= sizeof(reply_data) - 4; i++) {
        auto c = acl.getClientByIdx(i);
        if (!c->isAdmin()) continue;  // skip non-Admin entries
        memcpy(&reply_data[ofs], c->id.pub_key, 6); ofs += 6;  // just 6-byte pub_key prefix
        reply_data[ofs++] = c->permissions;
      }
      return ofs;
    }
  }
  return 0; // unknown command
}

void MyMesh::logRxRaw(float snr, float rssi, const uint8_t raw[], int len) {
#if MESH_PACKET_LOGGING
  Serial.print(getLogDateTime());
  Serial.print(" RAW: ");
  mesh::Utils::printHex(Serial, raw, len);
  Serial.println();
#endif
}

void MyMesh::logRx(mesh::Packet *pkt, int len, float score) {
  if (_logging) {
    File f = openAppend(PACKET_LOG_FILE);
    if (f) {
      f.print(getLogDateTime());
      f.printf(": RX, len=%d (type=%d, route=%s, payload_len=%d) SNR=%d RSSI=%d score=%d", len,
               pkt->getPayloadType(), pkt->isRouteDirect() ? "D" : "F", pkt->payload_len,
               (int)_radio->getLastSNR(), (int)_radio->getLastRSSI(), (int)(score * 1000));

      if (pkt->getPayloadType() == PAYLOAD_TYPE_PATH || pkt->getPayloadType() == PAYLOAD_TYPE_REQ ||
          pkt->getPayloadType() == PAYLOAD_TYPE_RESPONSE || pkt->getPayloadType() == PAYLOAD_TYPE_TXT_MSG) {
        f.printf(" [%02X -> %02X]\n", (uint32_t)pkt->payload[1], (uint32_t)pkt->payload[0]);
      } else {
        f.printf("\n");
      }
      f.close();
    }
  }
}
void MyMesh::logTx(mesh::Packet *pkt, int len) {
  if (_logging) {
    File f = openAppend(PACKET_LOG_FILE);
    if (f) {
      f.print(getLogDateTime());
      f.printf(": TX, len=%d (type=%d, route=%s, payload_len=%d)", len, pkt->getPayloadType(),
               pkt->isRouteDirect() ? "D" : "F", pkt->payload_len);

      if (pkt->getPayloadType() == PAYLOAD_TYPE_PATH || pkt->getPayloadType() == PAYLOAD_TYPE_REQ ||
          pkt->getPayloadType() == PAYLOAD_TYPE_RESPONSE || pkt->getPayloadType() == PAYLOAD_TYPE_TXT_MSG) {
        f.printf(" [%02X -> %02X]\n", (uint32_t)pkt->payload[1], (uint32_t)pkt->payload[0]);
      } else {
        f.printf("\n");
      }
      f.close();
    }
  }
}
void MyMesh::logTxFail(mesh::Packet *pkt, int len) {
  if (_logging) {
    File f = openAppend(PACKET_LOG_FILE);
    if (f) {
      f.print(getLogDateTime());
      f.printf(": TX FAIL!, len=%d (type=%d, route=%s, payload_len=%d)\n", len, pkt->getPayloadType(),
               pkt->isRouteDirect() ? "D" : "F", pkt->payload_len);
      f.close();
    }
  }
}

int MyMesh::calcRxDelay(float score, uint32_t air_time) const {
  if (_prefs.rx_delay_base <= 0.0f) return 0;
  return (int)((pow(_prefs.rx_delay_base, 0.85f - score) - 1.0) * air_time);
}

const char *MyMesh::getLogDateTime() {
  static char tmp[32];
  uint32_t now = getRTCClock()->getCurrentTime();
  DateTime dt = DateTime(now);
  sprintf(tmp, "%02d:%02d:%02d - %d/%d/%d U", dt.hour(), dt.minute(), dt.second(), dt.day(), dt.month(),
          dt.year());
  return tmp;
}

uint32_t MyMesh::getRetransmitDelay(const mesh::Packet *packet) {
  uint32_t t = (_radio->getEstAirtimeFor(packet->getPathByteLen() + packet->payload_len + 2) * _prefs.tx_delay_factor);
  return getRNG()->nextInt(0, 5*t + 1);
}
uint32_t MyMesh::getDirectRetransmitDelay(const mesh::Packet *packet) {
  uint32_t t = (_radio->getEstAirtimeFor(packet->getPathByteLen() + packet->payload_len + 2) * _prefs.direct_tx_delay_factor);
  return getRNG()->nextInt(0, 5*t + 1);
}

bool MyMesh::allowPacketForward(const mesh::Packet *packet) {
  if (_prefs.disable_fwd) return false;
  if (packet->isRouteFlood() && packet->getPathHashCount() >= _prefs.flood_max) return false;
  return true;
}

void MyMesh::onAnonDataRecv(mesh::Packet *packet, const uint8_t *secret, const mesh::Identity &sender,
                            uint8_t *data, size_t len) {
  if (packet->getPayloadType() == PAYLOAD_TYPE_ANON_REQ) { // received an initial request by a possible admin
                                                           // client (unknown at this stage)
    uint32_t sender_timestamp, sender_sync_since;
    memcpy(&sender_timestamp, data, 4);
    memcpy(&sender_sync_since, &data[4], 4); // sender's "sync messags SINCE x" timestamp

    data[len] = 0;                                        // ensure null terminator

    ClientInfo* client = NULL;
    if (data[8] == 0) {   // blank password, just check if sender is in ACL
      client = acl.getClient(sender.pub_key, PUB_KEY_SIZE);
      if (client == NULL) {
      #if MESH_DEBUG
        MESH_DEBUG_PRINTLN("Login, sender not in ACL");
      #endif
      }
    }
    if (client == NULL) {
      uint8_t perm;
      if (strcmp((char *)&data[8], _prefs.password) == 0) { // check for valid admin password
        perm = PERM_ACL_ADMIN;
      } else {
        if (strcmp((char *)&data[8], _prefs.guest_password) == 0) {   // check the room/public password
          perm = PERM_ACL_READ_WRITE;
        } else if (_prefs.allow_read_only) {
          perm = PERM_ACL_GUEST;
        } else {
          MESH_DEBUG_PRINTLN("Incorrect room password");
          return; // no response. Client will timeout
        }
      }

      client = acl.putClient(sender, 0);  // add to known clients (if not already known)
      if (sender_timestamp <= client->last_timestamp) {
        MESH_DEBUG_PRINTLN("possible replay attack!");
        return;
      }

      MESH_DEBUG_PRINTLN("Login success!");
      client->last_timestamp = sender_timestamp;
      client->extra.room.sync_since = sender_sync_since;
      client->extra.room.pending_ack = 0;
      client->extra.room.push_failures = 0;

      client->last_activity = getRTCClock()->getCurrentTime();
      client->permissions &= ~0x03;
      client->permissions |= perm;
      memcpy(client->shared_secret, secret, PUB_KEY_SIZE);

      dirty_contacts_expiry = futureMillis(LAZY_CONTACTS_WRITE_DELAY);
    }

    if (packet->isRouteFlood()) {
      client->out_path_len = OUT_PATH_UNKNOWN;  // need to rediscover out_path
    }

    uint32_t now = getRTCClock()->getCurrentTimeUnique();
    memcpy(reply_data, &now, 4); // response packets always prefixed with timestamp
    // TODO: maybe reply with count of messages waiting to be synced for THIS client?
    reply_data[4] = RESP_SERVER_LOGIN_OK;
    reply_data[5] = 0; // Legacy: was recommended keep-alive interval (secs / 16)
    reply_data[6] = (client->isAdmin() ? 1 : (client->permissions == 0 ? 2 : 0));
    // LEGACY: reply_data[7] = getUnsyncedCount(client);
    reply_data[7] = client->permissions; // NEW
    getRNG()->random(&reply_data[8], 4);   // random blob to help packet-hash uniqueness
    reply_data[12] = FIRMWARE_VER_LEVEL;  // New field

    next_push = futureMillis(PUSH_NOTIFY_DELAY_MILLIS); // delay next push, give RESPONSE packet time to arrive first

    if (packet->isRouteFlood()) {
      // let this sender know path TO here, so they can use sendDirect(), and ALSO encode the response
      mesh::Packet *path = createPathReturn(sender, client->shared_secret, packet->path, packet->path_len,
                                            PAYLOAD_TYPE_RESPONSE, reply_data, 13);
      if (path) sendFlood(path, SERVER_RESPONSE_DELAY, packet->getPathHashSize());
    } else {
      mesh::Packet *reply = createDatagram(PAYLOAD_TYPE_RESPONSE, sender, client->shared_secret, reply_data, 13);
      if (reply) {
        if (client->out_path_len != OUT_PATH_UNKNOWN) { // we have an out_path, so send DIRECT
          sendDirect(reply, client->out_path, client->out_path_len, SERVER_RESPONSE_DELAY);
        } else {
          sendFlood(reply, SERVER_RESPONSE_DELAY, packet->getPathHashSize());
        }
      }
    }
  }
}

int MyMesh::searchPeersByHash(const uint8_t *hash) {
  int n = 0;
  for (int i = 0; i < acl.getNumClients(); i++) {
    if (acl.getClientByIdx(i)->id.isHashMatch(hash)) {
      matching_peer_indexes[n++] = i; // store the INDEXES of matching contacts (for subsequent 'peer' methods)
    }
  }
  return n;
}

void MyMesh::getPeerSharedSecret(uint8_t *dest_secret, int peer_idx) {
  int i = matching_peer_indexes[peer_idx];
  if (i >= 0 && i < acl.getNumClients()) {
    // lookup pre-calculated shared_secret
    memcpy(dest_secret, acl.getClientByIdx(i)->shared_secret, PUB_KEY_SIZE);
  } else {
    MESH_DEBUG_PRINTLN("getPeerSharedSecret: Invalid peer idx: %d", i);
  }
}

void MyMesh::onPeerDataRecv(mesh::Packet *packet, uint8_t type, int sender_idx, const uint8_t *secret,
                            uint8_t *data, size_t len) {
  int i = matching_peer_indexes[sender_idx];
  if (i < 0 || i >= acl.getNumClients()) { // get from our known_clients table (sender SHOULD already be known in this context)
    MESH_DEBUG_PRINTLN("onPeerDataRecv: invalid peer idx: %d", i);
    return;
  }
  auto client = acl.getClientByIdx(i);
  if (type == PAYLOAD_TYPE_TXT_MSG && len > 5) { // a CLI command or new Post
    uint32_t sender_timestamp;
    memcpy(&sender_timestamp, data, 4); // timestamp (by sender's RTC clock - which could be wrong)
    uint8_t flags = (data[4] >> 2);        // message attempt number, and other flags

    if (!(flags == TXT_TYPE_PLAIN || flags == TXT_TYPE_CLI_DATA)) {
      MESH_DEBUG_PRINTLN("onPeerDataRecv: unsupported command flags received: flags=%02x", (uint32_t)flags);
    } else if (sender_timestamp >= client->last_timestamp) { // prevent replay attacks, but send Acks for retries
      bool is_retry = (sender_timestamp == client->last_timestamp);
      client->last_timestamp = sender_timestamp;

      uint32_t now = getRTCClock()->getCurrentTimeUnique();
      client->last_activity = now;
      client->extra.room.push_failures = 0; // reset so push can resume (if prev failed)

      // len can be > original length, but 'text' will be padded with zeroes
      data[len] = 0; // need to make a C string again, with null terminator

      uint32_t ack_hash; // calc truncated hash of the message timestamp + text + sender pub_key, to prove to
                         // sender that we got it
      mesh::Utils::sha256((uint8_t *)&ack_hash, 4, data, 5 + strlen((char *)&data[5]), client->id.pub_key,
                          PUB_KEY_SIZE);

      uint8_t temp[166];
      bool send_ack;
      if (flags == TXT_TYPE_CLI_DATA) {
        if (client->isAdmin()) {
          if (is_retry) {
            temp[5] = 0; // no reply
          } else {
            handleCommand(sender_timestamp, (char *)&data[5], (char *)&temp[5]);
            temp[4] = (TXT_TYPE_CLI_DATA << 2); // attempt and flags,  (NOTE: legacy was: TXT_TYPE_PLAIN)
          }
          send_ack = false;
        } else {
          temp[5] = 0;      // no reply
          send_ack = false; // and no ACK...  user shoudn't be sending these
        }
      } else { // TXT_TYPE_PLAIN
        if ((client->permissions & PERM_ACL_ROLE_MASK) == PERM_ACL_GUEST) {
          temp[5] = 0;      // no reply
          send_ack = false; // no ACK
        } else {
          if (!is_retry) {
            addPost(client, (const char *)&data[5]);
          }
          temp[5] = 0; // no reply (ACK is enough)
          send_ack = true;
        }
      }

      uint32_t delay_millis;
      if (send_ack) {
        if (client->out_path_len == OUT_PATH_UNKNOWN) {
          mesh::Packet *ack = createAck(ack_hash);
          if (ack) sendFlood(ack, TXT_ACK_DELAY, packet->getPathHashSize());
          delay_millis = TXT_ACK_DELAY + REPLY_DELAY_MILLIS;
        } else {
          uint32_t d = TXT_ACK_DELAY;
          if (getExtraAckTransmitCount() > 0) {
            mesh::Packet *a1 = createMultiAck(ack_hash, 1);
            if (a1) sendDirect(a1, client->out_path, client->out_path_len, d);
            d += 300;
          }

          mesh::Packet *a2 = createAck(ack_hash);
          if (a2) sendDirect(a2, client->out_path, client->out_path_len, d);
          delay_millis = d + REPLY_DELAY_MILLIS;
        }
      } else {
        delay_millis = 0;
      }

      int text_len = strlen((char *)&temp[5]);
      if (text_len > 0) {
        if (now == sender_timestamp) {
          // WORKAROUND: the two timestamps need to be different, in the CLI view
          now++;
        }
        memcpy(temp, &now, 4); // mostly an extra blob to help make packet_hash unique

        // calc expected ACK reply
        // mesh::Utils::sha256((uint8_t *)&expected_ack_crc, 4, temp, 5 + text_len, self_id.pub_key,
        // PUB_KEY_SIZE);

        auto reply = createDatagram(PAYLOAD_TYPE_TXT_MSG, client->id, secret, temp, 5 + text_len);
        if (reply) {
          if (client->out_path_len == OUT_PATH_UNKNOWN) {
            sendFlood(reply, delay_millis + SERVER_RESPONSE_DELAY, packet->getPathHashSize());
          } else {
            sendDirect(reply, client->out_path, client->out_path_len, delay_millis + SERVER_RESPONSE_DELAY);
          }
        }
      }
    } else {
      MESH_DEBUG_PRINTLN("onPeerDataRecv: possible replay attack detected");
    }
  } else if (type == PAYLOAD_TYPE_REQ && len >= 5) {
    uint32_t sender_timestamp;
    memcpy(&sender_timestamp, data, 4); // timestamp (by sender's RTC clock - which could be wrong)
    if (sender_timestamp < client->last_timestamp) { // prevent replay attacks
      MESH_DEBUG_PRINTLN("onPeerDataRecv: possible replay attack detected");
    } else {
      client->last_timestamp = sender_timestamp;

      uint32_t now = getRTCClock()->getCurrentTime();
      client->last_activity = now; // <-- THIS will keep client connection alive
      client->extra.room.push_failures = 0;   // reset so push can resume (if prev failed)

      if (data[4] == REQ_TYPE_KEEP_ALIVE && packet->isRouteDirect()) { // request type
        uint32_t forceSince = 0;
        if (len >= 9) {                     // optional - last post_timestamp client received
          memcpy(&forceSince, &data[5], 4); // NOTE: this may be 0, if part of decrypted PADDING!
        } else {
          memcpy(&data[5], &forceSince, 4); // make sure there are zeroes in payload (for ack_hash calc below)
        }
        if (forceSince > 0) {
          client->extra.room.sync_since = forceSince; // force-update the 'sync since'
        }

        client->extra.room.pending_ack = 0;

        // TODO: Throttle KEEP_ALIVE requests!
        // if client sends too quickly, evict()

        // RULE: only send keep_alive response DIRECT!
        if (client->out_path_len != OUT_PATH_UNKNOWN) {
          uint32_t ack_hash; // calc ACK to prove to sender that we got request
          mesh::Utils::sha256((uint8_t *)&ack_hash, 4, data, 9, client->id.pub_key, PUB_KEY_SIZE);

          auto reply = createAck(ack_hash);
          if (reply) {
            reply->payload[reply->payload_len++] = getUnsyncedCount(client); // NEW: add unsynced counter to end of ACK packet
            sendDirect(reply, client->out_path, client->out_path_len, SERVER_RESPONSE_DELAY);
          }
        }
      } else {
        int reply_len = handleRequest(client, sender_timestamp, &data[4], len - 4);
        if (reply_len > 0) { // valid command
          if (packet->isRouteFlood()) {
            // let this sender know path TO here, so they can use sendDirect(), and ALSO encode the response
            mesh::Packet *path = createPathReturn(client->id, secret, packet->path, packet->path_len,
                                                  PAYLOAD_TYPE_RESPONSE, reply_data, reply_len);
            if (path) sendFlood(path, SERVER_RESPONSE_DELAY, packet->getPathHashSize());
          } else {
            mesh::Packet *reply = createDatagram(PAYLOAD_TYPE_RESPONSE, client->id, secret, reply_data, reply_len);
            if (reply) {
              if (client->out_path_len != OUT_PATH_UNKNOWN) { // we have an out_path, so send DIRECT
                sendDirect(reply, client->out_path, client->out_path_len, SERVER_RESPONSE_DELAY);
              } else {
                sendFlood(reply, SERVER_RESPONSE_DELAY, packet->getPathHashSize());
              }
            }
          }
        }
      }
    }
  }
}

bool MyMesh::onPeerPathRecv(mesh::Packet *packet, int sender_idx, const uint8_t *secret, uint8_t *path,
                            uint8_t path_len, uint8_t extra_type, uint8_t *extra, uint8_t extra_len) {
  // TODO: prevent replay attacks
  int i = matching_peer_indexes[sender_idx];

  if (i >= 0 && i < acl.getNumClients()) { // get from our known_clients table (sender SHOULD already be known in this context)
    MESH_DEBUG_PRINTLN("PATH to client, path_len=%d", (uint32_t)path_len);
    auto client = acl.getClientByIdx(i);
    client->out_path_len = mesh::Packet::copyPath(client->out_path, path, path_len); // store a copy of path, for sendDirect()
    client->last_activity = getRTCClock()->getCurrentTime();
  } else {
    MESH_DEBUG_PRINTLN("onPeerPathRecv: invalid peer idx: %d", i);
  }

  if (extra_type == PAYLOAD_TYPE_ACK && extra_len >= 4) {
    // also got an encoded ACK!
    processAck(extra);
  }

  // NOTE: no reciprocal path send!!
  return false;
}

void MyMesh::onAckRecv(mesh::Packet *packet, uint32_t ack_crc) {
  if (processAck((uint8_t *)&ack_crc)) {
    packet->markDoNotRetransmit(); // ACK was for this node, so don't retransmit
  }
}

MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondClock &ms, mesh::RNG &rng,
               mesh::RTCClock &rtc, mesh::MeshTables &tables)
    : mesh::Mesh(radio, ms, rng, rtc, *new StaticPoolPacketManager(32), tables),
      _cli(board, rtc, sensors, acl, &_prefs, this), telemetry(MAX_PACKET_PAYLOAD - 4) {
  last_millis = 0;
  uptime_millis = 0;
  next_local_advert = next_flood_advert = 0;
  dirty_contacts_expiry = 0;
  _logging = false;
  set_radio_at = revert_radio_at = 0;

  // defaults
  memset(&_prefs, 0, sizeof(_prefs));
  _prefs.airtime_factor = 1.0;
  _prefs.rx_delay_base = 0.0f;   // off by default, was 10.0
  _prefs.tx_delay_factor = 0.5f; // was 0.25f;
  _prefs.direct_tx_delay_factor = 0.2f; // was zero
  StrHelper::strncpy(_prefs.node_name, ADVERT_NAME, sizeof(_prefs.node_name));
  _prefs.node_lat = ADVERT_LAT;
  _prefs.node_lon = ADVERT_LON;
  StrHelper::strncpy(_prefs.password, ADMIN_PASSWORD, sizeof(_prefs.password));
  _prefs.freq = LORA_FREQ;
  _prefs.sf = LORA_SF;
  _prefs.bw = LORA_BW;
  _prefs.cr = LORA_CR;
  _prefs.tx_power_dbm = LORA_TX_POWER;
  _prefs.disable_fwd = 1;
  _prefs.advert_interval = 1;        // default to 2 minutes for NEW installs
  _prefs.flood_advert_interval = 12; // 12 hours
  _prefs.flood_max = 64;
  _prefs.interference_threshold = 0; // disabled
#ifdef ROOM_PASSWORD
  StrHelper::strncpy(_prefs.guest_password, ROOM_PASSWORD, sizeof(_prefs.guest_password));
#endif

  // GPS defaults
  _prefs.gps_enabled = 0;
  _prefs.gps_interval = 0;
  _prefs.advert_loc_policy = ADVERT_LOC_PREFS;

  next_post_idx = 0;
  next_client_idx = 0;
  next_push = 0;
  memset(posts, 0, sizeof(posts));
  _num_posted = _num_post_pushes = 0;
}

void MyMesh::begin(FILESYSTEM *fs) {
  mesh::Mesh::begin();
  _fs = fs;
  // load persisted prefs
  _cli.loadPrefs(_fs);

  acl.load(_fs, self_id);

  radio_set_params(_prefs.freq, _prefs.bw, _prefs.sf, _prefs.cr);
  radio_set_tx_power(_prefs.tx_power_dbm);

  updateAdvertTimer();
  updateFloodAdvertTimer();

  board.setAdcMultiplier(_prefs.adc_multiplier);

#if ENV_INCLUDE_GPS == 1
  applyGpsPrefs();
#endif
}

void MyMesh::applyTempRadioParams(float freq, float bw, uint8_t sf, uint8_t cr, int timeout_mins) {
  set_radio_at = futureMillis(2000); // give CLI reply some time to be sent back, before applying temp radio params
  pending_freq = freq;
  pending_bw = bw;
  pending_sf = sf;
  pending_cr = cr;

  revert_radio_at = futureMillis(2000 + timeout_mins * 60 * 1000); // schedule when to revert radio params
}

bool MyMesh::formatFileSystem() {
#if defined(NRF52_PLATFORM)
  return InternalFS.format();
#elif defined(RP2040_PLATFORM)
  return LittleFS.format();
#elif defined(ESP32)
  return SPIFFS.format();
#else
#error "need to implement file system erase"
  return false;
#endif
}

void MyMesh::sendSelfAdvertisement(int delay_millis, bool flood) {
  mesh::Packet *pkt = createSelfAdvert();
  if (pkt) {
    if (flood) {
      sendFlood(pkt, delay_millis, _prefs.path_hash_mode + 1);
    } else {
      sendZeroHop(pkt, delay_millis);
    }
  } else {
    MESH_DEBUG_PRINTLN("ERROR: unable to create advertisement packet!");
  }
}

void MyMesh::updateAdvertTimer() {
  if (_prefs.advert_interval > 0) { // schedule local advert timer
    next_local_advert = futureMillis((uint32_t)_prefs.advert_interval * 2 * 60 * 1000);
  } else {
    next_local_advert = 0; // stop the timer
  }
}
void MyMesh::updateFloodAdvertTimer() {
  if (_prefs.flood_advert_interval > 0) { // schedule flood advert timer
    next_flood_advert = futureMillis(((uint32_t)_prefs.flood_advert_interval) * 60 * 60 * 1000);
  } else {
    next_flood_advert = 0; // stop the timer
  }
}

void MyMesh::dumpLogFile() {
#if defined(RP2040_PLATFORM)
  File f = _fs->open(PACKET_LOG_FILE, "r");
#else
  File f = _fs->open(PACKET_LOG_FILE);
#endif
  if (f) {
    while (f.available()) {
      int c = f.read();
      if (c < 0) break;
      Serial.print((char)c);
    }
    f.close();
  }
}

void MyMesh::setTxPower(int8_t power_dbm) {
  radio_set_tx_power(power_dbm);
}

void MyMesh::saveIdentity(const mesh::LocalIdentity &new_id) {
#if defined(NRF52_PLATFORM) || defined(STM32_PLATFORM)
  IdentityStore store(*_fs, "");
#elif defined(ESP32)
  IdentityStore store(*_fs, "/identity");
#elif defined(RP2040_PLATFORM)
  IdentityStore store(*_fs, "/identity");
#else
#error "need to define saveIdentity()"
#endif
  store.save("_main", new_id);
}

void MyMesh::clearStats() {
  radio_driver.resetStats();
  resetStats();
  ((SimpleMeshTables *)getTables())->resetStats();
}

void MyMesh::formatStatsReply(char *reply) {
  StatsFormatHelper::formatCoreStats(reply, board, *_ms, _err_flags, _mgr);
}

void MyMesh::formatRadioStatsReply(char *reply) {
  StatsFormatHelper::formatRadioStats(reply, _radio, radio_driver, getTotalAirTime(), getReceiveAirTime());
}

void MyMesh::formatPacketStatsReply(char *reply) {
  StatsFormatHelper::formatPacketStats(reply, radio_driver, getNumSentFlood(), getNumSentDirect(), 
                                       getNumRecvFlood(), getNumRecvDirect());
}

void MyMesh::handleCommand(uint32_t sender_timestamp, char *command, char *reply) {
  while (*command == ' ')
    command++; // skip leading spaces

  if (strlen(command) > 4 && command[2] == '|') { // optional prefix (for companion radio CLI)
    memcpy(reply, command, 3);                    // reflect the prefix back
    reply += 3;
    command += 3;
  }

  // handle ACL related commands
  if (memcmp(command, "setperm ", 8) == 0) {   // format:  setperm {pubkey-hex} {permissions-int8}
    char* hex = &command[8];
    char* sp = strchr(hex, ' ');   // look for separator char
    if (sp == NULL) {
      strcpy(reply, "Err - bad params");
    } else {
      *sp++ = 0;   // replace space with null terminator

      uint8_t pubkey[PUB_KEY_SIZE];
      int hex_len = min(sp - hex, PUB_KEY_SIZE*2);
      if (mesh::Utils::fromHex(pubkey, hex_len / 2, hex)) {
        uint8_t perms = atoi(sp);
        if (acl.applyPermissions(self_id, pubkey, hex_len / 2, perms)) {
          dirty_contacts_expiry = futureMillis(LAZY_CONTACTS_WRITE_DELAY);   // trigger acl.save()
          strcpy(reply, "OK");
        } else {
          strcpy(reply, "Err - invalid params");
        }
      } else {
        strcpy(reply, "Err - bad pubkey");
      }
    }
  } else if (sender_timestamp == 0 && strcmp(command, "get acl") == 0) {
    Serial.println("ACL:");
    for (int i = 0; i < acl.getNumClients(); i++) {
      auto c = acl.getClientByIdx(i);
      if (c->permissions == 0) continue;  // skip deleted (or guest) entries

      Serial.printf("%02X ", c->permissions);
      mesh::Utils::printHex(Serial, c->id.pub_key, PUB_KEY_SIZE);
      Serial.printf("\n");
    }
    reply[0] = 0;
  } else{
    _cli.handleCommand(sender_timestamp, command, reply);  // common CLI commands
  }
}

bool MyMesh::saveFilter(ClientInfo* client) {
  return client->isAdmin();    // only save Admins
}

void MyMesh::loop() {
  mesh::Mesh::loop();

  if (millisHasNowPassed(next_push) && acl.getNumClients() > 0) {
    // check for ACK timeouts
    for (int i = 0; i < acl.getNumClients(); i++) {
      auto c = acl.getClientByIdx(i);
      if (c->extra.room.pending_ack && millisHasNowPassed(c->extra.room.ack_timeout)) {
        c->extra.room.push_failures++;
        c->extra.room.pending_ack = 0; // reset  (TODO: keep prev expected_ack's in a list, incase they arrive LATER, after we retry)
        MESH_DEBUG_PRINTLN("pending ACK timed out: push_failures: %d", (uint32_t)c->extra.room.push_failures);
      }
    }
    // check next Round-Robin client, and sync next new post
    auto client = acl.getClientByIdx(next_client_idx);
    bool did_push = false;
    if (client->extra.room.pending_ack == 0 && client->last_activity != 0 &&
        client->extra.room.push_failures < 3) { // not already waiting for ACK, AND not evicted, AND retries not max
      MESH_DEBUG_PRINTLN("loop - checking for client %02X", (uint32_t)client->id.pub_key[0]);
      uint32_t now = getRTCClock()->getCurrentTime();
      for (int k = 0, idx = next_post_idx; k < MAX_UNSYNCED_POSTS; k++) {
        auto p = &posts[idx];
        if (now >= p->post_timestamp + POST_SYNC_DELAY_SECS &&
            p->post_timestamp > client->extra.room.sync_since // is new post for this Client?
            && !p->author.matches(client->id)) {   // don't push posts to the author
          // push this post to Client, then wait for ACK
          pushPostToClient(client, *p);
          did_push = true;
          MESH_DEBUG_PRINTLN("loop - pushed to client %02X: %s", (uint32_t)client->id.pub_key[0], p->text);
          break;
        }
        idx = (idx + 1) % MAX_UNSYNCED_POSTS; // wrap to start of cyclic queue
      }
    } else {
      MESH_DEBUG_PRINTLN("loop - skipping busy (or evicted) client %02X", (uint32_t)client->id.pub_key[0]);
    }
    next_client_idx = (next_client_idx + 1) % acl.getNumClients(); // round robin polling for each client

    if (did_push) {
      next_push = futureMillis(SYNC_PUSH_INTERVAL);
    } else {
      // were no unsynced posts for curr client, so proccess next client much quicker! (in next loop())
      next_push = futureMillis(SYNC_PUSH_INTERVAL / 8);
    }
  }

  if (next_flood_advert && millisHasNowPassed(next_flood_advert)) {
    mesh::Packet *pkt = createSelfAdvert();
    uint32_t delay_millis = 0;
    if (pkt) sendFlood(pkt, delay_millis, _prefs.path_hash_mode + 1);

    updateFloodAdvertTimer(); // schedule next flood advert
    updateAdvertTimer();      // also schedule local advert (so they don't overlap)
  } else if (next_local_advert && millisHasNowPassed(next_local_advert)) {
    mesh::Packet *pkt = createSelfAdvert();
    if (pkt) sendZeroHop(pkt);

    updateAdvertTimer(); // schedule next local advert
  }

  if (set_radio_at && millisHasNowPassed(set_radio_at)) { // apply pending (temporary) radio params
    set_radio_at = 0;                                     // clear timer
    radio_set_params(pending_freq, pending_bw, pending_sf, pending_cr);
    MESH_DEBUG_PRINTLN("Temp radio params");
  }

  if (revert_radio_at && millisHasNowPassed(revert_radio_at)) { // revert radio params to orig
    revert_radio_at = 0;                                        // clear timer
    radio_set_params(_prefs.freq, _prefs.bw, _prefs.sf, _prefs.cr);
    MESH_DEBUG_PRINTLN("Radio params restored");
  }

  // is pending dirty contacts write needed?
  if (dirty_contacts_expiry && millisHasNowPassed(dirty_contacts_expiry)) {
    acl.save(_fs, MyMesh::saveFilter);
    dirty_contacts_expiry = 0;
  }

  // TODO: periodically check for OLD/inactive entries in known_clients[], and evict

  // update uptime
  uint32_t now = millis();
  uptime_millis += now - last_millis;
  last_millis = now;
}