Wifi笔记 | Android P 启动流程之startSup

一、WifiNative

WifiNative 主要工作：

• startHal
• startSupplicant
• createStaIface

这里主要讲第二点：startSupplicant

二、

2.1 startSupplicant

private boolean startSupplicant() {
        synchronized (mLock) {
            if (!mIfaceMgr.hasAnyStaIface()) {
                if (!mWificondControl.enableSupplicant()) {
                    Log.e(TAG, "Failed to enable supplicant");
                    return false;
                }
                if (!waitForSupplicantConnection()) {
                    Log.e(TAG, "Failed to connect to supplicant");
                    return false;
                }
                if (!mSupplicantStaIfaceHal.registerDeathHandler(
                        new SupplicantDeathHandlerInternal())) {
                    Log.e(TAG, "Failed to register supplicant death handler");
                    return false;
                }
            }
            return true;
        }
    }
private boolean waitForSupplicantConnection() {
        // Start initialization if not already started.
        if (!mSupplicantStaIfaceHal.isInitializationStarted()
                && !mSupplicantStaIfaceHal.initialize()) {
            return false;
        }
        boolean connected = false;
        int connectTries = 0;
        while (!connected && connectTries++ < CONNECT_TO_SUPPLICANT_RETRY_TIMES) {
            // Check if the initialization is complete.
            connected = mSupplicantStaIfaceHal.isInitializationComplete();
            if (connected) {
                break;
            }
            try {
                Thread.sleep(CONNECT_TO_SUPPLICANT_RETRY_INTERVAL_MS);
            } catch (InterruptedException ignore) {
            }
        }
        return connected;
    }

2.1 WificondControl::enableSupplicant

 /**
    * Enable wpa_supplicant via wificond.
    * @return Returns true on success.
    */
    public boolean enableSupplicant() {
        if (!retrieveWificondAndRegisterForDeath()) {
            return false;
        }
        try {
            return mWificond.enableSupplicant();
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to enable supplicant due to remote exception");
        }
        return false;
    }

2.2 Server::enableSupplicant

//system/connectivity/wificond/server.cpp
Status Server::enableSupplicant(bool* success) {
  *success = supplicant_manager_->StartSupplicant();
  return Status::ok();
}

2.3 SupplicantManager::StartSupplicant()

启动的两行代码：
property_set("ctl.start", kSupplicantServiceName);
sched_yield(); //---这个应当是异步调用直接返回的意思

//frameworks/opt/net/wifi/libwifi_system/supplicant_manager.cpp
bool SupplicantManager::StartSupplicant() {
  char supp_status[PROPERTY_VALUE_MAX] = {'\0'};
  int count = 200; /* wait at most 20 seconds for completion */
  const prop_info* pi;
  unsigned serial = 0;
 
  /* Check whether already running */
  if (property_get(kSupplicantInitProperty, supp_status, NULL) &&
      strcmp(supp_status, "running") == 0) {
    return true;
  }
 /*
   * Get a reference to the status property, so we can distinguish
   * the case where it goes stopped => running => stopped (i.e.,
   * it start up, but fails right away) from the case in which
   * it starts in the stopped state and never manages to start
   * running at all.
   */
  pi = __system_property_find(kSupplicantInitProperty);
  if (pi != NULL) {
    serial = __system_property_serial(pi);
  }
 
  property_set("ctl.start", kSupplicantServiceName);
  sched_yield();
 
  while (count-- > 0) {
    if (pi == NULL) {
      pi = __system_property_find(kSupplicantInitProperty);
    }
    if (pi != NULL) {
      /*
       * property serial updated means that init process is scheduled
       * after we sched_yield, further property status checking is based on this
       */
      if (__system_property_serial(pi) != serial) {
        __system_property_read(pi, NULL, supp_status);
        if (strcmp(supp_status, "running") == 0) {
          return true;
        } else if (strcmp(supp_status, "stopped") == 0) {
          return false;
        }
      }
    }
    usleep(100000);
  }
  return false;
}

2.4 总结

startSupplicant 是启动WIFI的协议栈登录认证接口，通过WificondControl::enableSupplicant调用Server::enableSupplicant，Server端启动了一个SupplicantManager来处理启动事件，最后调用
property_set("ctl.start", kSupplicantServiceName);
sched_yield();
通过 pi = __system_property_find(kSupplicantInitProperty); 来获取状态返回给上层等待函数：waitForSupplicantConnection。
这样就是一个完整的协议栈（startSupplicant）启动流程

完~~~
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