Android13 wificond scan流程分析

我们通过代码分析wificond的scan流程，在WifiScanningService的startScan流程分析中我们分析了HAL层以上的流程，下面我们继续分析HAL层的流程，首先是ScannerImpl的scan方法：

//system/connectivity/wificond/scanning/ScannerImpl.h
class ScannerImpl : public android::net::wifi::nl80211::BnWifiScannerImpl {
 private:
ScanUtils* const scan_utils_;
}
//system/connectivity/wificond/scanning/ScannerImpl.cpp
class ScannerImpl : public android::net::wifi::nl80211::BnWifiScannerImpl {
Status ScannerImpl::scan(const SingleScanSettings& scan_settings,
                         bool* out_success) {
  if (!CheckIsValid()) {
    *out_success = false;
    return Status::ok();
  }


  if (scan_started_) {
    LOG(WARNING) << "Scan already started";
  }
  // Only request MAC address randomization when station is not associated.
  bool request_random_mac =
      wiphy_features_.supports_random_mac_oneshot_scan &&
      !client_interface_->IsAssociated();
  int scan_type = scan_settings.scan_type_;
          //wiphy_features_是硬件层直接返回的当前WLAN芯片支持的扫描类型
          //如果请求的类型不被硬件支持，则回落为SCAN_TYPE_DEFAULT
  if (!IsScanTypeSupported(scan_settings.scan_type_, wiphy_features_)) {
    LOG(DEBUG) << "Ignoring scan type because device does not support it";
    scan_type = SCAN_TYPE_DEFAULT;
  }


  // Initialize it with an empty ssid for a wild card scan.
  vector<vector<uint8_t>> ssids = {
  {}};


          //wiphy_features_是硬件层直接返回的当前WLAN芯片支持的扫描类型
          //如果请求的类型不被硬件支持，则回落为SCAN_TYPE_DEFAULT
  vector<vector<uint8_t>> skipped_scan_ssids;
  vector<vector<uint8_t>> skipped_long_ssids;
  for (auto& network : scan_settings.hidden_networks_) {
    if (ssids.size() + 1 > scan_capabilities_.max_num_scan_ssids) {
      skipped_scan_ssids.emplace_back(network.ssid_);
      continue;
    }
    if (network.ssid_.size() > 32) {
        skipped_long_ssids.emplace_back(network.ssid_);
        continue;
    }
    ssids.push_back(network.ssid_);
  }


  LogSsidList(skipped_scan_ssids, "Skip scan ssid for single scan");
  LogSsidList(skipped_long_ssids, "Skip too long ssid");


  //将扫描需要覆盖的信道频率添加到freqs向量中
  vector<uint32_t> freqs;
  for (auto& channel : scan_settings.channel_settings_) {
    freqs.push_back(channel.frequency_);
  }


  int error_code = 0;
  if (!scan_utils_->Scan(interface_index_, request_random_mac, scan_type,
                         scan_settings.enable_6ghz_rnr_, ssids, freqs, &error_code)) { //调用ScanUtils的Scan方法
    if (error_code == ENODEV) {
        nodev_counter_ ++;
        LOG(WARNING) << "Scan failed with error=nodev. counter=" << nodev_counter_;
    }
    CHECK(error_code != ENODEV || nodev_counter_ <= 3)
        << "Driver is in a bad state, restarting wificond";
    *out_success = false;
    return Status::ok();
  }
  nodev_counter_ = 0;
  scan_started_