ESP32-PaxCounter/src/wifiscan.cpp

// Basic Config
#include "globals.h"
#include "wifiscan.h"

// Local logging tag
static const char TAG[] = "wifi";

static wifi_country_t wifi_country = {WIFI_MY_COUNTRY, WIFI_CHANNEL_MIN,
                                      WIFI_CHANNEL_MAX, 0,
                                      WIFI_COUNTRY_POLICY_MANUAL};

// using IRAM_:ATTR here to speed up callback function
IRAM_ATTR void wifi_sniffer_packet_handler(void *buff,
                                           wifi_promiscuous_pkt_type_t type) {
  const wifi_promiscuous_pkt_t *ppkt = (wifi_promiscuous_pkt_t *)buff;
  const wifi_ieee80211_packet_t *ipkt =
      (wifi_ieee80211_packet_t *)ppkt->payload;
  const wifi_ieee80211_mac_hdr_t *hdr = &ipkt->hdr;

  if ((cfg.rssilimit) &&
      (ppkt->rx_ctrl.rssi < cfg.rssilimit)) // rssi is negative value
    ESP_LOGD(TAG, "WiFi RSSI %d -> ignoring (limit: %d)", ppkt->rx_ctrl.rssi,
             cfg.rssilimit);
  else // count seen MAC
    mac_add((uint8_t *)hdr->addr2, ppkt->rx_ctrl.rssi, MAC_SNIFF_WIFI);
}

void wifi_sniffer_init(void) {
  wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
  cfg.nvs_enable = 0; // we don't need any wifi settings from NVRAM
  wifi_promiscuous_filter_t filter = {
      .filter_mask = WIFI_PROMIS_FILTER_MASK_MGMT}; // we need only MGMT frames
  ESP_ERROR_CHECK(esp_wifi_init(&cfg));             // configure Wifi with cfg
  ESP_ERROR_CHECK(
      esp_wifi_set_country(&wifi_country)); // set locales for RF and channels
  ESP_ERROR_CHECK(
      esp_wifi_set_storage(WIFI_STORAGE_RAM)); // we don't need NVRAM
  ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_NULL));
  ESP_ERROR_CHECK(esp_wifi_stop());
  ESP_ERROR_CHECK(
      esp_wifi_set_promiscuous_filter(&filter)); // set MAC frame filter
  ESP_ERROR_CHECK(esp_wifi_set_promiscuous_rx_cb(&wifi_sniffer_packet_handler));
  ESP_ERROR_CHECK(esp_wifi_set_promiscuous(true)); // now switch on monitor mode
}

// Wifi channel rotation task
void wifi_channel_loop(void *pvParameters) {

  configASSERT(((uint32_t)pvParameters) == 1); // FreeRTOS check

  while (1) {

    if (ChannelTimerIRQ) {
      portENTER_CRITICAL(&timerMux);
      ChannelTimerIRQ = 0;
      portEXIT_CRITICAL(&timerMux);
      // rotates variable channel 1..WIFI_CHANNEL_MAX
      channel = (channel % WIFI_CHANNEL_MAX) + 1;
      esp_wifi_set_channel(channel, WIFI_SECOND_CHAN_NONE);
      ESP_LOGD(TAG, "Wifi set channel %d", channel);

      vTaskDelay(1 / portTICK_PERIOD_MS); // reset watchdog
    }

  } // end of infinite wifi channel rotation loop
}

// IRQ handler
void IRAM_ATTR ChannelSwitchIRQ() {
  portENTER_CRITICAL(&timerMux);
  ChannelTimerIRQ++;
  portEXIT_CRITICAL(&timerMux);
}