從剛接觸WiFi時跟過wifi的開啟流程，當時還是android9。到了Android11代碼架構有了不小的改動，在這里重新梳理一遍，便于在工作中更快速的跟蹤代碼。

一、Settings里改動不大，還是從WifiEnabler開始，調用WiFiManager的setWifiEnabled。
packages/apps/Settings/src/com/android/settings/wifi/WifiEnabler.java

if (!mWifiManager.setWifiEnabled(isChecked)) {// ErrormSwitchWidget.setEnabled(true);Toast.makeText(mContext, R.string.wifi_error, Toast.LENGTH_SHORT).show();}

二、這里要注意了，Android11默認加入了支持雙WiFi的代碼。這里打開WiFi就提供了倆個接口
frameworks/base/wifi/java/android/net/wifi/WifiManager.java
正常打開WiFi是調用這個單參的函數。

public boolean setWifiEnabled(boolean enabled) {try {return mService.setWifiEnabled(mContext.getOpPackageName(), enabled);} catch (RemoteException e) {throw e.rethrowFromSystemServer();} }

如果是指定打開哪個STA，就要調用雙參的函數。

public boolean setWifiEnabled(int staId, boolean enabled) {try {return mService.setWifiEnabled2(mContext.getOpPackageName(), staId, enabled);} catch (RemoteException e) {throw e.rethrowFromSystemServer();} }

三、可以看到Wifimanager中正常打開WiFi和指定打開哪個STA的區別就是在WifiServiceImpl中setWifiEnabled2的參數不同。如果是打開第一個WiFi，則參數2為STA_PRIMARY，如果是打開其他WiFi，則參數2為傳入的staId。
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiServiceImpl.java

public synchronized boolean setWifiEnabled(String packageName, boolean enable) {return setWifiEnabled2(packageName, STA_PRIMARY, enable); } public synchronized boolean setWifiEnabled2(String packageName, int staId,boolean enable) {if (enforceChangePermission(packageName) != MODE_ALLOWED) {return false;}boolean isPrivileged = isPrivileged(Binder.getCallingPid(), Binder.getCallingUid());if (!isPrivileged && !isDeviceOrProfileOwner(Binder.getCallingUid(), packageName)&& !mWifiPermissionsUtil.isTargetSdkLessThan(packageName, Build.VERSION_CODES.Q,Binder.getCallingUid())&& !isSystem(packageName, Binder.getCallingUid())) {mLog.info("setWifiEnabled not allowed for uid=%").c(Binder.getCallingUid()).flush();return false;}// If Airplane mode is enabled, only privileged apps are allowed to toggle Wifiif (mSettingsStore.isAirplaneModeOn() && !isPrivileged) {mLog.err("setWifiEnabled in Airplane mode: only Settings can toggle wifi").flush();return false;}// If SoftAp is enabled, only privileged apps are allowed to toggle wifiif (!isPrivileged && mTetheredSoftApTracker.getState() == WIFI_AP_STATE_ENABLED) {mLog.err("setWifiEnabled with SoftAp enabled: only Settings can toggle wifi").flush();return false;}mLog.info("setWifiEnabled package=% uid=% enable=%").c(packageName).c(Binder.getCallingUid()).c(enable).flush();long ident = Binder.clearCallingIdentity();try {if (staId == STA_PRIMARY && !mSettingsStore.handleWifiToggled(enable)) {// Nothing to do if wifi cannot be toggledreturn true;}} finally {Binder.restoreCallingIdentity(ident);}if (mWifiPermissionsUtil.checkNetworkSettingsPermission(Binder.getCallingUid())) {mWifiMetrics.logUserActionEvent(enable ? UserActionEvent.EVENT_TOGGLE_WIFI_ON: UserActionEvent.EVENT_TOGGLE_WIFI_OFF);}if (!mIsControllerStarted) {Log.e(TAG,"WifiController is not yet started, abort setWifiEnabled");return false;}mWifiMetrics.incrementNumWifiToggles(isPrivileged, enable); if(staId == STA_PRIMARY)mActiveModeWarden.wifiToggled(); else if(staId == STA_SECONDARY && (getNumConcurrentStaSupported() > 1) && (getWifiEnabledState() == WifiManager.WIFI_STATE_ENABLED)) mActiveModeWarden.qtiWifiToggled(staId, enable);elseLog.e(TAG,"setWifiEnabled not allowed for Id: " + staId);return true; }

四、可以看到wifiservice調用了ActiveModeWarden的wifiToggled，發送了CMD_WIFI_TOGGLED的消息，通知WiFi切換了。
frameworks/opt/net/wifi/service/java/com/android/server/wifi/ActiveModeWarden.java

public void wifiToggled() {mWifiController.sendMessage(WifiController.CMD_WIFI_TOGGLED); }

五、我們看WifiController是怎么處理這個消息的。WifiController是ActiveModeWarden中的一個狀態機，用來管理WiFi的操作，包括熱點啊飛行模式什么的。
打開WiFi之前，狀態機應該是在Disabled狀態，我們看Disable狀態里的處理。

class DisabledState extends BaseState {public boolean processMessageFiltered(Message msg) {switch (msg.what) {case CMD_WIFI_TOGGLED:case CMD_SCAN_ALWAYS_MODE_CHANGED:if (shouldEnableSta()) {startClientModeManager();transitionTo(mEnabledState);}break;

啟動一個新的客戶端管理。

private boolean startClientModeManager() {Log.d(TAG, "Starting ClientModeManager");ClientListener listener = new ClientListener();ClientModeManager manager = mWifiInjector.makeClientModeManager(listener);listener.setActiveModeManager(manager);manager.start();if (!switchClientModeManagerRole(manager)) {return false;}mActiveModeManagers.add(manager);return true; }

六、start了ClientModeManager
frameworks/opt/net/wifi/service/java/com/android/server/wifi/ClientModeManager.java

public void start() {Log.d(TAG, "Starting with role ROLE_CLIENT_SCAN_ONLY");mRole = ROLE_CLIENT_SCAN_ONLY;mTargetRole = ROLE_CLIENT_SCAN_ONLY;mStateMachine.sendMessage(ClientModeStateMachine.CMD_START); }

看一下是誰處理了這個START消息呢

private class IdleState extends State {@Overridepublic boolean processMessage(Message message) {switch (message.what) {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;} }

七、這里可以看出，WifiNative先去啟動HAL
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiNative.java

public String setupInterfaceForClientInScanMode(@NonNull InterfaceCallback interfaceCallback) {synchronized (mLock) {if (!startHal()) {mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToHal();return null;}Iface iface = mIfaceMgr.allocateIface(Iface.IFACE_TYPE_STA_FOR_SCAN);iface.externalListener = interfaceCallback;iface.name = createStaIface(iface);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;}iface.networkObserver = new NetworkObserverInternal(iface.id);if (!registerNetworkObserver(iface.networkObserver)) {teardownInterface(iface.name);return null;}mWifiMonitor.startMonitoring(iface.name);onInterfaceStateChanged(iface, isInterfaceUp(iface.name));iface.featureSet = getSupportedFeatureSetInternal(iface.name);return iface.name;} }

八、啟動HAL

WifiVendorHal.java-->startVendorHal --> HalDeviceManager.java --> startWifi --> IWifi.start

mWifi.start()方法是啟動實際加載WiFi動作的調用，這里涉及HIDL機制調用。通過獲取IWifi接口對象，調用其方法。這里IWifi接口對象是IWifi.hal文件中實現。

android/hardware/interfaces/wifi/1.0/IWifi.hal

在編譯時，編譯器會將IWifi.hal解析為IWifi.java文件,直接看該文件中的start方法實現即可。

android/out/soong//.intermediates/hardware/interfaces/wifi/1.0/android.hardware.wifi-V1.0-java_gen_java/gen/srcs/android/hardware/wifi/V1_0/IWifi.javapublic android.hardware.wifi.V1_0.WifiStatus start() throws android.os.RemoteException {try {... ... ... ...mRemote.transact(3 /* start */, _hidl_request, _hidl_reply, 0 /* flags */);_hidl_reply.verifySuccess();_hidl_request.releaseTemporaryStorage();return _hidl_out_status;} finally {_hidl_reply.release();}}

通過binder調用，將調用到wifi.cpp中的start()方法.

android/hardware/interfaces/wifi/1.4/default/wifi.cppReturn<void> Wifi::start(start_cb hidl_status_cb) {return validateAndCall(this, WifiStatusCode::ERROR_UNKNOWN,&Wifi::startInternal, hidl_status_cb);}wifi.cpp->start() ==> wifi.cpp->startInternal() ==> wifi.cpp->initializeModeControllerAndLegacyHal()==> WifiModeController->initialize() ==> DriverTool->LoadDriver()

通過調用DriverTool->LoadDriver將返回到Android framework中。下面是LoadDriver()的實現。

android/frameworks/opt/net/wifi/libwifi_hal/include/wifi_hal/driver_tool.cppbool DriverTool::LoadDriver() {return ::wifi_load_driver() == 0;}

在wifi_load_driver()方法中，將調用系統接口加載WiFi驅動ko。關于系統insmod接口的調用，本文不做分析。到這里，已梳理完在WifiNative類中調用的startHal()方法。

android/frameworks/opt/net/wifi/libwifi_hal/wifi_hal_common.cppint wifi_load_driver() {... ... ... ...insmod(file,args);... ... ... ...}

調用WifiNl80211Manager類的setupInterfaceForClientMode()方法。

該類的主要對WiFi 80211nl管理接口的封裝，接口在WiFicond守護進程中呈現給WiFi框架。該類提供的接口僅使用與WiFi框架，訪問權限受selinux權限保護。

setupInterfaceForClientMode()方法主要為Station模式設置接口。

android/frameworks/base/wifi/java/android/net/wifi/nl80211/WifiNl80211Manager.javapublic boolean setupInterfaceForClientMode(@NonNull String ifaceName,@NonNull @CallbackExecutor Executor executor,@NonNull ScanEventCallback scanCallback, @NonNull ScanEventCallback pnoScanCallback) {... ... ... ...// Refresh HandlersmClientInterfaces.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);... ... ... ...}

到這里，ClientModeStateMachine狀態機在IdleState狀態成功處理完了CMD_START消息。狀態機將轉到“mScanOnlyModeState”狀態，將會執行以下調用流程(具體原因可查看狀態機機制)。

IdleState.exit()->StartedState.enter()->StartedState.exit()->ScanOnlyModeState.enter()。

九、啟動HAL以后，就要啟動supplicant了。
在第五步的時候我們調用了ActiveModeWarden.java的startClientModeManagerh函數。start以后會執行switchClientModeManagerRole

private boolean switchClientModeManagerRole(@NonNull ClientModeManager modeManager) {if (mSettingsStore.isWifiToggleEnabled()) {modeManager.setRole(ActiveModeManager.ROLE_CLIENT_PRIMARY);} else if (checkScanOnlyModeAvailable()) {modeManager.setRole(ActiveModeManager.ROLE_CLIENT_SCAN_ONLY);} else {Log.e(TAG, "Something is wrong, no client mode toggles enabled");return false;}return true; n true;}

十、從上一步可以看出setRole的參數為ROLE_CLIENT_SCAN_ONLY，所以這里發送的是CMD_SWITCH_TO_CONNECT_MODE廣播
frameworks/opt/net/wifi/service/java/com/android/server/wifi/ClientModeManager.java

public void setRole(@Role int role) {Preconditions.checkState(CLIENT_ROLES.contains(role));if (role == ROLE_CLIENT_SCAN_ONLY) {mTargetRole = role;// Switch client mode manager to scan only mode.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);} }

十一、看一下CMD_SWITCH_TO_CONNECT_MODE的處理，這里先執行了switchClientInterfaceToConnectivityMode

private class StartedState extends State {public boolean processMessage(Message message) {switch(message.what) {case CMD_SWITCH_TO_CONNECT_MODE:mRole = message.arg1; // could be any one of possible connect mode roles.updateConnectModeState(WifiManager.WIFI_STATE_ENABLING,WifiManager.WIFI_STATE_DISABLED);if (!mWifiNative.switchClientInterfaceToConnectivityMode(mClientInterfaceName)) {updateConnectModeState(WifiManager.WIFI_STATE_UNKNOWN,WifiManager.WIFI_STATE_ENABLING);updateConnectModeState(WifiManager.WIFI_STATE_DISABLED,WifiManager.WIFI_STATE_UNKNOWN);mModeListener.onStartFailure();break;}transitionTo(mConnectModeState);break;

十二、可以看到這里啟動了supplicant
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiNative.java

public boolean switchClientInterfaceToConnectivityMode(@NonNull String ifaceName) {synchronized (mLock) {final Iface iface = mIfaceMgr.getIface(ifaceName);if (!startSupplicant()) {Log.e(TAG, "Failed to start supplicant");teardownInterface(iface.name);mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToSupplicant();return false;}if (!mSupplicantStaIfaceHal.setupIface(iface.name)) {Log.e(TAG, "Failed to setup iface in supplicant on " + iface);teardownInterface(iface.name);mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToSupplicant();return false;}iface.type = Iface.IFACE_TYPE_STA_FOR_CONNECTIVITY;iface.featureSet = getSupportedFeatureSetInternal(iface.name);Log.i(TAG, "Successfully switched to connectivity mode on iface=" + iface);return true;}} private boolean startSupplicant() {synchronized (mLock) {if (!mIfaceMgr.hasAnyStaIfaceForConnectivity()) {if (!startAndWaitForSupplicantConnection()) {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;} }

在這里等待與supplicant建立連接

private boolean startAndWaitForSupplicantConnection() {// Start initialization if not already started.if (!mSupplicantStaIfaceHal.isInitializationStarted()&& !mSupplicantStaIfaceHal.initialize()) {return false;}if (!mSupplicantStaIfaceHal.startDaemon()) {Log.e(TAG, "Failed to startup supplicant");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; }

十三、這里是通過HIDL來打開supplicant的
frameworks/opt/net/wifi/service/java/com/android/server/wifi/SupplicantStaIfaceHal.java

startDaemon -> startDaemon_V1_1 -> getSupplicantMockableV1_1 -> getSupplicantMockable protected ISupplicant getSupplicantMockable() throws RemoteException, NoSuchElementException {synchronized (mLock) {ISupplicant iSupplicant = ISupplicant.getService();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("android.hardware.wifi.supplicant@1.0::ISupplicant", serviceName)); }

十四、 在這個方法中將觸發啟動wpa_supplicant進程，這里需要注意，在manifest.xml中對其需要進行配置，運行時會將服務名稱注冊到hwservicemanager中。

wpa_supplicant目錄下文件調用：

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;}

十五、將wpa_supplicant添加注冊到hwservicemanager，SupplicantStaIfaceHal.getSupplicantMockable()執行完成返回。

這里再深入看下“supplicant_object_->registerAsService(“wpa_supplicant”)”是如何通過調用注冊的呢？

android/out/soong/.intermediates/hardware/interfaces/wifi/supplicant/1.3/android.hardware.wifi.supplicant@1.3_genc++/gen/android/hardware/wifi/supplicant/1.3/SupplicantAll.cppandroid/system/libhidl/transport/ServiceManagement.cppandroid/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()

十六、wpa_supplicant注冊完成后，SupplicantStaIfaceHal類中將收到回調通知信息，

private final IServiceNotification mServiceNotificationCallback = new IServiceNotification.Stub() { public void onRegistration(String fqName, String name, boolean preexisting) { synchronized (mLock) { if (!initSupplicantService()) { supplicantServiceDiedHandler(mDeathRecipientCookie); }

返回通知的調用邏輯。

SupplicantStaIfaceHal.initSupplicantService() -> SupplicantStaIfaceHal.getSupplicantMockable()

十七、到此位置supplicant已經啟動。
switchClientInterfaceToConnectivityMode會繼續調用SupplicantStaIfaceHal.setupIface()方法設置接口。設置成功后，就會打印成功的日志。

Log.i(TAG, "Successfully switched to connectivity mode on iface=" + iface);

十八、CMD_SWITCH_TO_CONNECT_MODE消息處理完以后狀態機就會切換到ConnectModeState。
這里會調用setOperationalMode

transitionTo(mConnectModeState); private class ConnectModeState extends State {@Overridepublic void enter() {Log.d(TAG, "entering ConnectModeState");mClientModeImpl.registerModeListener(mClientModeImplListener);mClientModeImpl.setOperationalMode(ClientModeImpl.CONNECT_MODE,mClientInterfaceName);}

十九、這里會進入到mDisconnectedState
frameworks/opt/net/wifi/service/java/com/android/server/wifi/ClientModeImpl.java

public void setOperationalMode(int mode, String ifaceName) {if (mVerboseLoggingEnabled) {log("setting operational mode to " + String.valueOf(mode) + " for iface: " + ifaceName);}mModeChange = true;if (mode != CONNECT_MODE) {// we are disabling client mode... need to exit connect mode nowtransitionTo(mDefaultState);} else {// do a quick sanity check on the iface name, make sure it isn't nullif (ifaceName != null) {mInterfaceName = ifaceName;updateInterfaceCapabilities(ifaceName);transitionTo(mDisconnectedState);mWifiScoreReport.setInterfaceName(ifaceName);} else {Log.e(TAG, "supposed to enter connect mode, but iface is null -> DefaultState");transitionTo(mDefaultState);}}// use the CMD_SET_OPERATIONAL_MODE to force the transitions before other messages are// handled.sendMessageAtFrontOfQueue(CMD_SET_OPERATIONAL_MODE); }

二十、ActiveModeWarden類中設置的ClientLister將被觸發回調。 wifiScaner.setScanningEnabled()發送消息CMD_ENABLE，給到WiFiscanningSerivceimpl類中。
到這里，WiFi已處于打開狀態，并將進行掃描網絡，待連接。WiFi打開流程分析完成。

ActiveModeWarden.ClientListener -> ScanRequestProxy.enableScanning() -> ScanRequestProxy.enableScanningInternal() -> wifiScaner.setScanningEnabled()

總結

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