Android 11 WiFi启动流程 |
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Android 11 WiFi启动流程
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欢迎大家一起学习探讨通信之WLAN。本节重点基于Android11分析讨论WiFi开启流程。用户点击一下“WiFi”开关，WiFi开启了。看似如此简单操作，但系统流程调用还是相当复杂。因Android11版本框架中WiFi打开流程有一部分变化。接下来我们一起分析下Android 11 WiFi的打开流程是怎么样的呢？ 【1】系统启动时，system_server进程中会启动Wifiservice服务，启动该服务在SystemServer.java文件。 private static final String WIFI_SERVICE_CLASS ="com.android.server.wifi.WifiService"; if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WIFI)) { // Wifi Service must be started first for wifi-related services. mSystemServiceManager.startService(WIFI_SERVICE_CLASS); mSystemServiceManager.startService("com.android.server.wifi.scanner.WifiScanningService"); }
该方法在启动Wifiservice服务时将会被调用到，作用是将服务注册到ServiceManager中。 protected final void publishBinderService(String name, IBinder service, boolean allowIsolated, int dumpPriority) { ServiceManager.addService(name, service, allowIsolated, dumpPriority); }【2】在Wifiservice启动时，创建WifiServiceImpl实例对象，并将WiFiserviceimpl对象注册到servicemanager中。 这个对象很重要，它是整个系统WiFi服务的管理者，所有的用户端操作请求都将由它初步预处理，然后分发给不同的服务处理执行。 android/frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiService.java public WifiService(Context contextBase) { super(contextBase); mWifiContext = new WifiContext(contextBase); WifiInjector injector = new WifiInjector(mWifiContext); WifiAsyncChannel channel = new WifiAsyncChannel(TAG); mImpl = new WifiServiceImpl(mWifiContext, injector, channel); } public void onStart() { Log.i(TAG, "Registering " + Context.WIFI_SERVICE); publishBinderService(Context.WIFI_SERVICE, mImpl); }【3】好，接下来到了WifiServiceImpl初始化过程，首先，看下该类的构造函数。 public WifiServiceImpl(Context context, WifiInjector wifiInjector, AsyncChannel asyncChannel) { mContext = context; mWifiInjector = wifiInjector; ... ... ... ... mClientModeImpl = mWifiInjector.getClientModeImpl(); mActiveModeWarden = mWifiInjector.getActiveModeWarden(); ... ... ... ... }
看到WiFiserviceimpl构造函数，基本上做了与WiFi服务管理的相关类的初始化动作。下面简单看下Android11 相对Android9 新增加与Wifi打开相关的几个初始化类： ClientModeImpl 作为客户端的模式实现，作为客户端事件处理在这里完成，并所有的连接状态变化在这里初始化。ActiveModeWarden 提供WiFi不同操作模式的配置实现。
到这里，系统启动完成，WifiService服务已正常运行，接下来分析用户“打开WiFi”这个简单的操作，Android11 系统背后的运行流程。
【4】用户点击WiFi开关按钮打开WiFi，通过Android提供的WiFiManager的接口类，通过AIDL机制将事件传递至WifiSerivce管理服务，在WifiServiceImpl对象中对其处理。 public synchronized boolean setWifiEnabled(String packageName, boolean enable) { //权限检查 boolean isPrivileged = isPrivileged(Binder.getCallingPid(), Binder.getCallingUid()); //检查飞行模式是否打开，同时只运行授权的app打开WiFi if (mSettingsStore.isAirplaneModeOn() && !isPrivileged) { mLog.err("setWifiEnabled in Airplane mode: only Settings can toggle wifi").flush(); return false; } //检查调用客户端是否拥有NETWORK_SETTINGS权限，如有在将事件数据记录。 if (mWifiPermissionsUtil.checkNetworkSettingsPermission(Binder.getCallingUid())) { mWifiMetrics.logUserActionEvent(enable ? UserActionEvent.EVENT_TOGGLE_WIFI_ON : UserActionEvent.EVENT_TOGGLE_WIFI_OFF); } //记录WiFi切换状态。 mWifiMetrics.incrementNumWifiToggles(isPrivileged, enable); //触发WiFi打开动作。 mActiveModeWarden.wifiToggled(); } private boolean isPrivileged(int pid, int uid) { return checkNetworkSettingsPermission(pid, uid) || checkNetworkSetupWizardPermission(pid, uid) || checkNetworkStackPermission(pid, uid) || checkNetworkManagedProvisioningPermission(pid, uid); }
【5】接下来将进入“ActiveModeWarden”类中。先看 WifiService服务调用的方法“mActiveModeWarden.wifiToggled()”。 android/frameworks/opt/net/wifi/service/java/com/android/server/wifi/ActiveModeWarden.java 在wifiToggled方法中，发送消息“WifiController.CMD_WIFI_TOGGLED”。 public void wifiToggled() { mWifiController.sendMessage(WifiController.CMD_WIFI_TOGGLED); }WifiController是ActiveModeWarden的内部类，继承StateMachine类，在ActiveModeWarden构造函数中对其进行初始化； WifiService服务启动后，在WifiServiceImpl中，调用mActiveModeWarden.start()对其启动。WifiController状态机状态有三个如下：
状态机启动时，根据WiFi开启状态进行状态机初始化。因WiFi是由关闭切换至打开，因此，状态机初始到“mDisabledState”状态。 public void start() { if (shouldEnableSta()) { startClientModeManager(); setInitialState(mEnabledState); } else { setInitialState(mDisabledState); } } private boolean shouldEnableSta() { return mSettingsStore.isWifiToggleEnabled() || checkScanOnlyModeAvailable(); }WifiController接收到CMD_WIFI_TOGGLED消息，将在“mDisabledState”状态进行处理， public boolean processMessageFiltered(Message msg) { ... ... ... ... case CMD_WIFI_TOGGLED: case CMD_SCAN_ALWAYS_MODE_CHANGED: if (shouldEnableSta()) { startClientModeManager(); transitionTo(mEnabledState); } break; ... ... ... ...这里调用startClientModeManager()方法，启动一个客户端管理对象。 private boolean startClientModeManager() { //ClientListener为ActiveModeWarden的内部监听类。 ClientListener listener = new ClientListener(); //获取客户端管理对象，并设置监听。 ClientModeManager manager = mWifiInjector.makeClientModeManager(listener); listener.setActiveModeManager(manager); manager.start(); //切换客户端模式 if (!switchClientModeManagerRole(manager)) { return false; } mActiveModeManagers.add(manager); return true; }
【6】好！到这里我们跳到ClientModeManager类中。在其构造函数中，实例化了ClientModeStateMachine内部类对象mStateMachine 。start方法中，触发设置Station模式“ROLE_CLIENT_SCAN_ONLY”，并发送 ClientModeStateMachine.CMD_START消息。 ClientModeManager(Context context, @NonNull Looper looper, Clock clock, WifiNative wifiNative, Listener listener, WifiMetrics wifiMetrics, SarManager sarManager, WakeupController wakeupController, ClientModeImpl clientModeImpl) { ... ... ... ... mStateMachine = new ClientModeStateMachine(looper); mDeferStopHandler = new DeferStopHandler(TAG, looper); ... ... ... ... } public void start() { mTargetRole = ROLE_CLIENT_SCAN_ONLY; mStateMachine.sendMessage(ClientModeStateMachine.CMD_START); }ClientModeStateMachine类的状态机状态如下，并初始到“mIdleState”状态和启动状态机。
接下来在startClientModeManager()调用方法switchClientModeManagerRole(manager)切换客户端设置模式角色。 private boolean switchClientModeManagerRole(@NonNull ClientModeManager modeManager) { if (mSettingsStore.isWifiToggleEnabled()) { //打开WiFi将设置角色为“ROLE_CLIENT_PRIMARY”； modeManager.setRole(ActiveModeManager.ROLE_CLIENT_PRIMARY); } else if (checkScanOnlyModeAvailable()) { modeManager.setRole(ActiveModeManager.ROLE_CLIENT_SCAN_ONLY); } ... ... ... ... }在setRole()方法中，将role设置的值保存在mTargetRole变量，并发送消息给ClientModeStateMachine状态机。 public void setRole(@Role int role) { if (role == ROLE_CLIENT_SCAN_ONLY) { mTargetRole = role; mStateMachine.sendMessage(ClientModeStateMachine.CMD_SWITCH_TO_SCAN_ONLY_MODE) } else if (CLIENT_CONNECTIVITY_ROLES.contains(role)) { mTargetRole = role; // Switch client mode manager to connect mode mStateMachine.sendMessage(ClientModeStateMachine.CMD_SWITCH_TO_CONNECT_MODE, role); } }程序执行到此，ActiveModeWarden类中WiFicontroller状态机在DisabledState状态处理完了“CMD_WIFI_TOGGLED”这个消息，状态机将跳转至“EnabledState”。通过状态机机制可知，将会执行DisabledState.exit()方法退出DisabledState状态；执行EnabledState.enter()方法进入到EnabledState状态。WiFicontroller状态机在WiFi打开中将停留在该状态。
【7】从上流程可知，“ClientModeStateMachine.CMD_START”和“ClientModeStateMachine.CMD_SWITCH_TO_CONNECT_MODE”两条消息还处于待处理状态。 在ClientModeStateMachine类构造函数可知，状态机初始状态为“IdleState”，此时，将执行IdleState.enter()方法进入该状态，并开始处理CMD_START消息。 private class IdleState extends State { ... ... ... ... case CMD_START: // Always start in scan mode first. mClientInterfaceName =mWifiNative.setupInterfaceForClientInScanMode( mWifiNativeInterfaceCallback); if (TextUtils.isEmpty(mClientInterfaceName)) { Log.e(TAG, "Failed to create ClientInterface. Sit in Idle"); mModeListener.onStartFailure(); break; } transitionTo(mScanOnlyModeState); break; ... ... ... ...在处理CMD_START消息时，将调用WifiNative类中setupInterfaceForClientInScanMode()方法。 【8】好！先看WifiNative类中该方法的实现。 android/frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiNative.java public String setupInterfaceForClientInScanMode( @NonNull InterfaceCallback interfaceCallback) { synchronized (mLock) { //startwifi 加载WiFi驱动 if (!startHal()) { Log.e(TAG, "Failed to start Hal"); mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToHal(); return null; } //分配对应的接口 Iface iface = mIfaceMgr.allocateIface(Iface.IFACE_TYPE_STA_FOR_SCAN); if (iface == null) { Log.e(TAG, "Failed to allocate new STA iface"); return null; } iface.externalListener = interfaceCallback; //创建对应的station接口 iface.name = createStaIface(iface); if (TextUtils.isEmpty(iface.name)) { Log.e(TAG, "Failed to create iface in vendor HAL"); mIfaceMgr.removeIface(iface.id); mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToHal(); return null; } //设置客户端接口 if (!mWifiCondManager.setupInterfaceForClientMode(iface.name, Runnable::run, new NormalScanEventCallback(iface.name), new PnoScanEventCallback(iface.name))) { Log.e(TAG, "Failed to setup iface in wificond=" + iface.name); teardownInterface(iface.name); mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToWificond(); return null; } //设置接口up/down的检测通知 iface.networkObserver = new NetworkObserverInternal(iface.id); if (!registerNetworkObserver(iface.networkObserver)) { Log.e(TAG, "Failed to register network observer for iface=" + iface.name); teardownInterface(iface.name); return null; } //启动wpa_supplicant事件监听 mWifiMonitor.startMonitoring(iface.name); onInterfaceStateChanged(iface, isInterfaceUp(iface.name)); //获取WiFi支持的feature iface.featureSet = getSupportedFeatureSetInternal(iface.name); return iface.name; } }（1）startHal方法内部调用 startHal()->startHal()->WifiVendorHal.startVendorHal()->HalDeviceManager.start()->HalDeviceManager.startWifi() 这里看下启动WiFi的方法“HalDeviceManager.startWifi()”。在这个方法中，将加载WiFi驱动。 private boolean startWifi() { ... ... ... ... synchronized (mLock) { try { if (mWifi == null) { return false; } else { int triedCount = 0; //加载WiFi驱动将尝试4次，START_HAL_RETRY_TIMES=3。 while (triedCount start() ==> wifi.cpp->startInternal() ==> wifi.cpp->initializeModeControllerAndLegacyHal() ==> WifiModeController->initialize() ==> DriverTool->LoadDriver()通过调用DriverTool->LoadDriver将返回到Android framework中。下面是LoadDriver()的实现。 android/frameworks/opt/net/wifi/libwifi_hal/include/wifi_hal/driver_tool.cpp bool DriverTool::LoadDriver() { return ::wifi_load_driver() == 0; }在wifi_load_driver()方法中，将调用系统接口加载WiFi驱动ko。关于系统insmod接口的调用，本文不做分析。到这里，已梳理完在WifiNative类中调用的startHal()方法。 android/frameworks/opt/net/wifi/libwifi_hal/wifi_hal_common.cpp int wifi_load_driver() { ... ... ... ... insmod(file,args); ... ... ... ... }（2）调用WifiNl80211Manager类的setupInterfaceForClientMode()方法。 该类的主要对WiFi 80211nl管理接口的封装，接口在WiFicond守护进程中呈现给WiFi框架。该类提供的接口仅使用与WiFi框架，访问权限受selinux权限保护。 setupInterfaceForClientMode()方法主要为Station模式设置接口。 android/frameworks/base/wifi/java/android/net/wifi/nl80211/WifiNl80211Manager.java public boolean setupInterfaceForClientMode(@NonNull String ifaceName, @NonNull @CallbackExecutor Executor executor, @NonNull ScanEventCallback scanCallback, @NonNull ScanEventCallback pnoScanCallback) { ... ... ... ... // Refresh Handlers mClientInterfaces.put(ifaceName, clientInterface); try { IWifiScannerImpl wificondScanner = clientInterface.getWifiScannerImpl(); mWificondScanners.put(ifaceName, wificondScanner); Binder.allowBlocking(wificondScanner.asBinder()); ScanEventHandler scanEventHandler = new ScanEventHandler(executor, scanCallback); mScanEventHandlers.put(ifaceName, scanEventHandler); wificondScanner.subscribeScanEvents(scanEventHandler); PnoScanEventHandler pnoScanEventHandler = new PnoScanEventHandler(executor, pnoScanCallback); mPnoScanEventHandlers.put(ifaceName, pnoScanEventHandler); wificondScanner.subscribePnoScanEvents(pnoScanEventHandler); ... ... ... ... }
到这里，ClientModeStateMachine状态机在IdleState状态成功处理完了CMD_START消息。状态机将转到“mScanOnlyModeState”状态，将会执行以下调用流程(具体原因可查看状态机机制)。 IdleState.exit()->StartedState.enter()->StartedState.exit()->ScanOnlyModeState.enter()。
在状态转时，在StartedState.exit()中，将调用setOperationalMode方法。 public void exit() { mClientModeImpl.setOperationalMode(ClientModeImpl.DISABLED_MODE, null); }【9】这里将触及开篇提到的ClientModeImpl类。首先看下其构造函数，除了其他对象赋值初始化外，又一个状态机将与我们见面。
【10】目前，还遗留一个消息“ClientModeStateMachine.CMD_SWITCH_TO_CONNECT_MODE”待处理。此时，轮到该消息要被处理了。 ClientModeStateMachine状态机已处于“ScanOnlyModeState”状态，接收到该消息后，在processMessage方法中并未处理，而抛给父状态“StartedState”处理。在StartedState.processMessage()方法中对该消息进行了处理。 public boolean processMessage(Message message) { ... ... ... ... case CMD_SWITCH_TO_CONNECT_MODE: mRole = message.arg1; // could be any one of possible connect mode roles. //更新WiFi打开状态，发送系统广播通知。 updateConnectModeState(WifiManager.WIFI_STATE_ENABLING, WifiManager.WIFI_STATE_DISABLED); //切换设置clinent接口到连接模式。 if (!mWifiNative.switchClientInterfaceToConnectivityMode( mClientInterfaceName)) { ... ... ... ... mModeListener.onStartFailure(); break; } ... ... ... ... transitionTo(mConnectModeState); break; }（1）WifiNative类中，mWifiNative.switchClientInterfaceToConnectivityMode()方法 public boolean switchClientInterfaceToConnectivityMode(@NonNull String ifaceName) { synchronized (mLock) { ... ... ... ... //获取设置的接口 final Iface iface = mIfaceMgr.getIface(ifaceName); if (iface == null) { return false; } if (iface.type == Iface.IFACE_TYPE_STA_FOR_CONNECTIVITY) { return true; } //调用启动wpa_supplicant服务进程 if (!startSupplicant()) { teardownInterface(iface.name); mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToSupplicant(); return false; } //注册设置接口 if (!mSupplicantStaIfaceHal.setupIface(iface.name)) { return false; } iface.type = Iface.IFACE_TYPE_STA_FOR_CONNECTIVITY; iface.featureSet = getSupportedFeatureSetInternal(iface.name); ... ... ... ... return true; } } WifiNative.startSupplicant()->WifiNative.startAndWaitForSupplicantConnection()-> SupplicantStaIfaceHal.startDaemon()->SupplicantStaIfaceHal.startDaemon_V1_1()-> SupplicantStaIfaceHal.getSupplicantMockableV1_1()-> SupplicantStaIfaceHal.getSupplicantMockable()
这里看下getSupplicantMockable()方法，将在getService的时候启动wpa_supplicant进程。 通过HIDL调用获取wpa_supplicant服务。ISupplicant.getService(supplicantName)调用到ISupplicant.java。 protected ISupplicant getSupplicantMockable() throws RemoteException, NoSuchElementException { synchronized (mLock) { ISupplicant iSupplicant = ISupplicant.getService(supplicantName); if (iSupplicant == null) { throw new NoSuchElementException("Cannot get root service."); } return iSupplicant; } } android/out/soong/intermediates/hardware/interfaces/wifi/supplicant/1.0/android.hardware.wifi.supplicant-V1.0-java_gen_java/gen/srcs/android/hardware/wifi/supplicant/V1_0/ISupplicant.java public static ISupplicant getService(String serviceName) throws android.os.RemoteException { return ISupplicant.asInterface(android.os.HwBinder.getService("[email protected]::ISupplicant", serviceName)); }
在这个方法中将触发启动wpa_supplicant进程，这里需要注意，在manifest.xml中对其需要进行配置，运行时会将服务名称注册到hwservicemanager中。 wpa_supplicant目录下文件调用： main.c ==> wpa_supplicant.c->wpa_supplicant_init() ==> notify.c->wpas_notify_supplicant_initialized() ==> hidl.cpp->wpas_hidl_init() ==> Hidl_manager.cpp->registerHidlService() int HidlManager::registerHidlService(struct wpa_global *global) { // Create the main hidl service object and register it. supplicant_object_ = new Supplicant(global); if (supplicant_object_->registerAsService("wpa_supplicant") != android::NO_ERROR) { return 1; } return 0; }
【11】将wpa_supplicant添加注册到hwservicemanager，SupplicantStaIfaceHal.getSupplicantMockable()执行完成返回。 这里再深入看下“supplicant_object_->registerAsService("wpa_supplicant")”是如何通过调用注册的呢？ android/out/soong/.intermediates/hardware/interfaces/wifi/supplicant/1.3/[email protected]_genc++/gen/android/hardware/wifi/supplicant/1.3/SupplicantAll.cpp android/system/libhidl/transport/ServiceManagement.cpp android/system/hwservicemanager/ServiceManager.cpp supplicant_object_->registerAsService("wpa_supplicant") ==> ISupplicant.hal ==> ISupplicantAll.cpp->registerAsService() ==> ::android::hardware::details::registerAsServiceInternal(this, serviceName) ==> ServiceManagement.cpp->registerAsServiceInternal() ==> ServiceManager->addWithChain() ==> ServiceManager->addImpl()
【12】wpa_supplicant注册完成后，SupplicantStaIfaceHal类中将收到回调通知信息， private final IServiceNotification mServiceNotificationCallback = new IServiceNotification.Stub() { public void onRegistration(String fqName, String name, boolean preexisting) { synchronized (mLock) { if (!initSupplicantService()) { supplicantServiceDiedHandler(mDeathRecipientCookie); } else { } } } };返回通知的调用逻辑。 SupplicantStaIfaceHal.initSupplicantService() -> SupplicantStaIfaceHal.getSupplicantMockable()经过一系列调用，wpa_supplicant进程服务已启动完成。现回到WifiNative类中switchClientInterfaceToConnectivityMode()方法。 在该方法中，wpa_supplicant启动完成后，将调用SupplicantStaIfaceHal.setupIface()方法设置接口。 设置成功将执行完WifiNative.switchClientInterfaceToConnectivityMode()方法并退出。 [关键log打印]：WifiNative: Successfully switched to connectivity mode on iface=Iface:{Name=wlan0,Id=1,Type=STA_CONNECTIVITY}
【13】ClientModeManager类中，状态机ClientModeStateMachine在StartedState状态成功处理完“CMD_SWITCH_TO_CONNECT_MODE”消息。状态将转到“mConnectModeState”， 调用mConnectModeState.enter()方法。 public void enter() { //设置客户端模式为连接模式 mClientModeImpl.setOperationalMode(ClientModeImpl.CONNECT_MODE, mClientInterfaceName); mModeListener.onStarted(); //发送系统广播，通知WiFi已打开。 updateConnectModeState(WifiManager.WIFI_STATE_ENABLED, WifiManager.WIFI_STATE_ENABLING); //通知SAR管理着WiFi已打开 mSarManager.setClientWifiState(WifiManager.WIFI_STATE_ENABLED); }ClientModeImpl.setOperationalMode方法实现如下，设置模式为CONNECT_MODE。因此将走else流程。ClientModeImpl类中状态机将由DefaultState转到“DisconnectedState”状态。 状态机转到DisconnectedState状态，执行流程如下： ConnectModeState.() ->disconnectedstate.enter() public void setOperationalMode(int mode, String ifaceName) { mModeChange = true; if (mode != CONNECT_MODE) { transitionTo(mDefaultState); } else { if (ifaceName != null) { mInterfaceName = ifaceName; //更新设置是否支持80211ax。 updateInterfaceCapabilities(ifaceName); //状态转到DisconnectedState transitionTo(mDisconnectedState); mWifiScoreReport.setInterfaceName(ifaceName); } else { transitionTo(mDefaultState); } } sendMessageAtFrontOfQueue(CMD_SET_OPERATIONAL_MODE); }
【14】在此过程中，ActiveModeWarden类中设置的ClientLister将被触发回调。 wifiScaner.setScanningEnabled()发送消息CMD_ENABLE，给到WiFiscanningSerivceimpl类中。 系统调用到这里，WiFi已处于打开状态，并将进行扫描网络，待连接。WiFi打开流程分析完成。 ActiveModeWarden.ClientListener -> ScanRequestProxy.enableScanning() -> ScanRequestProxy.enableScanningInternal() -> wifiScaner.setScanningEnabled()注： 对以上所述专业知识有修正意见或建议，可随时留言反馈。如感兴趣更多通信知识，可关注“通信之WLAN”微信公众号。 谢谢大家支持~！
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