Android WiFi的断开分析

1.wifi断开大体流程：

1.wifi断开 wlan-driver最先知道。

2.wlan-driver在与路由器连接的时候(未断开时), 会有周期性的beacon帧来维持连接，AP端一旦遇到突发事情，会立刻通过802.11协议的 deauth 帧/ reject 帧等 通知到 driver。

3. wlan-driver一旦收到802协议的 deauth帧/reject帧等后，马上断开与AP的连接。

4. 紧接着，wlan-driver的上层WifiStateMachine内部广播通知系统外部网络环境，系统跟Settings开始同步处理此次的断开。

2.wifi断开原因

3.wifi断开流程

4.代码流程

1. wpa_supplicant 部分

• wpa_driver_nl80211_drv_init 其核心完成与drv通道绑定(既是与driver建立好暗号信息交流通道)，一旦有变化及时通风报信
• nl80211_init_bss 埋下的是第一步棋，监听解读 bss 802.11 数据帧
• process_bss_event 专门处理 802.11 数据帧，将之送往到 mlme_event 处理，mlme 完成分拣之后，装往 wpa_supplicant_event 大车上
• wpa_supplicant_event 大车把每个event送到对应得cmd中心处理站，进行卸货进一步分发处理，处理完成后通过 wpas_notify_state_changed 上报给 wpas_hidl_notify_state_changed 
• wpas_hidl_notify_state_changed 完成接力赛最后一棒，将事件上报给到 SupplicantStaIfaceHal
• 这里，断开的所有原因（将在 wpa_supplicant_event 函数里可以找到），结合 driver行为和空中包

external/wpa_supplicant_8/hostapd/src/drivers/driver_nl80211.c
static void * wpa_driver_nl80211_drv_init(void *ctx, const char *ifname,void *global_priv, int hostapd,const u8 *set_addr,
const char *driver_params){
	if (nl80211_init_bss(bss))
		goto failed;
}
static int nl80211_init_bss(struct i802_bss *bss)
{
	... 
	 nl_cb_set(bss->nl_cb, NL_CB_VALID, NL_CB_CUSTOM,process_bss_event, bss);
}

external/wpa_supplicant_8/src/drivers/driver_nl80211_event.c
int process_bss_event(struct nl_msg *msg, void *arg)
{
		switch (gnlh->cmd) {
		case NL80211_CMD_FRAME:
		case NL80211_CMD_FRAME_TX_STATUS:
		mlme_event(bss, gnlh->cmd, tb[NL80211_ATTR_FRAME],
		   tb[NL80211_ATTR_MAC], tb[NL80211_ATTR_TIMED_OUT],
		   tb[NL80211_ATTR_WIPHY_FREQ], tb[NL80211_ATTR_ACK],
		   tb[NL80211_ATTR_COOKIE],
		   tb[NL80211_ATTR_RX_SIGNAL_DBM],
		   tb[NL80211_ATTR_STA_WME]);
	break;
}

external/wpa_supplicant_8/wpa_supplicant/events.c
void wpa_supplicant_event(void *ctx, enum wpa_event_type event,union wpa_event_data *data)
{
	case EVENT_AUTH: 
	case .... 
	...
}

wpa_supplicant_set_state --wpa_supplicant.c
	wpas_notify_state_changed	-- hidi_manager.cpp
		wpas_hidl_notify_state_changed	-- hidl.cpp
		

2.wpa_supplicant --> hidl --> SupplicantStaIfaceHal

• wpa_supplicant 把接力棒交给了 wpa_supplicant 下面的 hidl.cpp，由他来完成事件的上报以及通知WifiMonitor
• 仍然是老套路，自从Android的版本升级之后，cpp与java之间的通信也是在不断地变化，从之前的aidl到现在的hidl，总是在变
• SupplicantStaIfaceHal 收到上报事件之后，通过这一长期合作伙伴WifiMonitor,将消息通知到系统各个模块

external/wpa_supplicant_8/wpa_supplicant/hidl/1.1/hidl.cpp
{
	.... 
	hidl_manager->notifyStateChange(wpa_s);
}

external/wpa_supplicant_8/wpa_supplicant/hidl/1.0/hidl_manager.cpp
{
	....
	callWithEachStaIfaceCallback(
    wpa_s->ifname, std::bind(
		       &ISupplicantStaIfaceCallback::onStateChanged,
		       std::placeholders::_1,
		       static_cast(
			   wpa_s->wpa_state),
		       bssid, hidl_network_id, hidl_ssid));
}

frameworks/opt/net/wifi/service/java/com/android/server/wifi/SupplicantStaIfaceHal.java
	 public void onStateChanged(int newState, byte[/* 6 */] bssid, int id,ArrayList ssid) {
 		mWifiMonitor.broadcastSupplicantStateChangeEvent( mIfaceName, 
 			getCurrentNetworkId(mIfaceName), wifiSsid, bssidStr, 		newSupplicantState);
 }

3.WifiMonitor --> WifiStateMachine --> 广播通知系统

• WifiMonitor 传输 SUPPLICANT_STATE_CHANGE_EVENT cmd 给到 WifiStateMachine
• WifiStateMachine 是 cmd 核心处理枢纽，每个 wifi 相关的 cmd 都会送到这里被分发执行
• 这里重点有DisconnectingState与 ConnectModeState 状态机，将会根据 wpa_supplicant 所处的状态 （disconnect 或者 completed 状态），处理行为不一样
• 如为 disconnect， 则转到 handleNetworkDisconnect(); 处理；如为 completed，则开启 ip gaining
• 最后，发送广播 WifiManager.NETWORK_STATE_CHANGED_ACTION ， 通知wifi状态变化了，处理同步断开的状态flow

frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiMonitor.java
public void broadcastSupplicantStateChangeEvent(String iface, int networkId, WifiSsid wifiSsid,....)
{
 		sendMessage(iface, SUPPLICANT_STATE_CHANGE_EVENT, 0, 0,new StateChangeResult(networkId, wifiSsid, bssid, newSupplicantState));
}

frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiStateMachine.java
class ConnectModeState extends State {
{
     .....  
	 case WifiMonitor.SUPPLICANT_STATE_CHANGE_EVENT:
	 	SupplicantState state = handleSupplicantStateChange(message);
	 	 if (state == SupplicantState.DISCONNECTED
				   && mNetworkInfo.getState() != NetworkInfo.State.DISCONNECTED) {
			   if (mVerboseLoggingEnabled) {
				   log("Missed CTRL-EVENT-DISCONNECTED, disconnect");
			   }
			   handleNetworkDisconnect();
			   transitionTo(mDisconnectedState);
		   }
		   
		if (state == SupplicantState.COMPLETED) {
	       mIpClient.confirmConfiguration();
	       mWifiScoreReport.noteIpCheck();
	   }
}

 class DisconnectingState extends State {
	   case WifiMonitor.SUPPLICANT_STATE_CHANGE_EVENT:
	   	handleNetworkDisconnect();
	   	transitionTo(mDisconnectedState);
}