（七十一）Android O WiFi热点 开启流程梳理

前言：之前主要梳理了WiFi开启扫描连接的流程，现在梳理下WiFi 热点 的开启流程。

时序图mdj样式：https://download.csdn.net/download/sinat_20059415/10542186

1. wifi热点简介

wifi热点是将手机接收的GPRS、3G或4G信号转化为wifi信号发出去的技术，手机必须有无线AP功能，才能当做热点。有些系统自带建热点这个功能比如 IOS（比如 iPhone 4s）。

如果你把你的iPhone当做热点，那么像TOUCH，PAD这样有WIFI功能的，都可以搜索到你手机建立的WIFI网络，连接上以后，TOUCH等使用WIFI产生的流量上网都是消耗的乐WIFI里的手机卡的GPRS或3G流量，所以iphone里最好放一张包大流量的上网卡。还有，把手机当做热点很费电，最好用的时候插上充电器。

2. WiFi热点开启流程梳理

2.1 Settings

Android O的Settings引入了PreferenceController这个包装类来实现对Preference的精细化控制，让代码结构更加地鲜明，很好地体现了单一职责原则，以前的Preference都是一大坨代码冗余在一起，看的都头疼。

TetherSettings->WifiTetherPreferenceController->WifiTetherSwitchBarController

TetherSettings是WiFi热点对应的界面，WifiTetherSwitchBarController是用来负责热点开关的相关逻辑处理的。

/packages/apps/Settings/src/com/android/settings/wifi/tether/WifiTetherSwitchBarController.java

public class WifiTetherSwitchBarController implements SwitchWidgetController.OnSwitchChangeListener,
        LifecycleObserver, OnStart, OnStop {
...
   @Override
    public boolean onSwitchToggled(boolean isChecked) {
        if (isChecked) {
            startTether();
        } else {
            stopTether();
        }
        return true;
    }

    void stopTether() {
        mSwitchBar.setEnabled(false);
        mConnectivityManager.stopTethering(TETHERING_WIFI);
    }

    void startTether() {
        mSwitchBar.setEnabled(false);
        mConnectivityManager.startTethering(TETHERING_WIFI, true /* showProvisioningUi */,
                NoOpOnStartTetheringCallback.newInstance(), new Handler(Looper.getMainLooper()));
    }

可以看到WiFi热点代开是通过ConnectivityManager的startTethering方法。

附

1) callback(抽象类直接new出来的，内部实现还没有。。。)

class NoOpOnStartTetheringCallback {

    public static ConnectivityManager.OnStartTetheringCallback newInstance() {
        return new ConnectivityManager.OnStartTetheringCallback() {
        };
    }   
}

    /**
     * Callback for use with {@link #startTethering} to find out whether tethering succeeded.
     * @hide
     */
    @SystemApi
    public static abstract class OnStartTetheringCallback {
        /**
         * Called when tethering has been successfully started.
         */
        public void onTetheringStarted() {}

        /**
         * Called when starting tethering failed.
         */
        public void onTetheringFailed() {}
    }

2)状态监听：

    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (WifiManager.WIFI_AP_STATE_CHANGED_ACTION.equals(action)) {
                final int state = intent.getIntExtra(
                        WifiManager.EXTRA_WIFI_AP_STATE, WifiManager.WIFI_AP_STATE_FAILED);
                handleWifiApStateChanged(state);
            } else if (Intent.ACTION_AIRPLANE_MODE_CHANGED.equals(action)) {
                enableWifiSwitch();
            }
        }
    };  

    private void handleWifiApStateChanged(int state) {
        switch (state) {
            case WifiManager.WIFI_AP_STATE_ENABLING:
                mSwitchBar.setEnabled(false);
                break;
            case WifiManager.WIFI_AP_STATE_ENABLED:
                if (!mSwitchBar.isChecked()) {
                    mSwitchBar.setChecked(true);
                }
                enableWifiSwitch();
                break;
            case WifiManager.WIFI_AP_STATE_DISABLING:
                if (mSwitchBar.isChecked()) {
                    mSwitchBar.setChecked(false);
                }
                mSwitchBar.setEnabled(false);
                break;
            case WifiManager.WIFI_AP_STATE_DISABLED:
                mSwitchBar.setChecked(false);
                enableWifiSwitch();
                break;
            default:
                mSwitchBar.setChecked(false);
                enableWifiSwitch();
                break;
        }
    }   

    private void enableWifiSwitch() {
        boolean isAirplaneMode = Settings.Global.getInt(mContext.getContentResolver(),
                Settings.Global.AIRPLANE_MODE_ON, 0) != 0;
        if (!isAirplaneMode) {
            mSwitchBar.setEnabled(!mDataSaverBackend.isDataSaverEnabled());
        } else {
            mSwitchBar.setEnabled(false);
        }
    }

2.2 ConnectivityManager

    /**
     * Runs tether provisioning for the given type if needed and then starts tethering if
     * the check succeeds. If no carrier provisioning is required for tethering, tethering is
     * enabled immediately. If provisioning fails, tethering will not be enabled. It also
     * schedules tether provisioning re-checks if appropriate.
     *
     * @param type The type of tethering to start. Must be one of
     *         {@link ConnectivityManager.TETHERING_WIFI},
     *         {@link ConnectivityManager.TETHERING_USB}, or
     *         {@link ConnectivityManager.TETHERING_BLUETOOTH}.
     * @param showProvisioningUi a boolean indicating to show the provisioning app UI if there
     *         is one. This should be true the first time this function is called and also any time
     *         the user can see this UI. It gives users information from their carrier about the
     *         check failing and how they can sign up for tethering if possible.
     * @param callback an {@link OnStartTetheringCallback} which will be called to notify the caller
     *         of the result of trying to tether.
     * @param handler {@link Handler} to specify the thread upon which the callback will be invoked.
     * @hide
     */
    @SystemApi
    @RequiresPermission(android.Manifest.permission.TETHER_PRIVILEGED)
    public void startTethering(int type, boolean showProvisioningUi,
            final OnStartTetheringCallback callback, Handler handler) {
        Preconditions.checkNotNull(callback, "OnStartTetheringCallback cannot be null.");

        ResultReceiver wrappedCallback = new ResultReceiver(handler) {
            @Override
            protected void onReceiveResult(int resultCode, Bundle resultData) {
                if (resultCode == TETHER_ERROR_NO_ERROR) {
                    callback.onTetheringStarted();
                } else {
                    callback.onTetheringFailed();
                }
            }
        };

        try {
            String pkgName = mContext.getOpPackageName();
            Log.i(TAG, "startTethering caller:" + pkgName);
            mService.startTethering(type, wrappedCallback, showProvisioningUi, pkgName);
        } catch (RemoteException e) {
            Log.e(TAG, "Exception trying to start tethering.", e);
            wrappedCallback.send(TETHER_ERROR_SERVICE_UNAVAIL, null);
        }
    }

至于mService:

        mConnectivityManager =
                (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

SystemServiceRegistry:

        registerService(Context.CONNECTIVITY_SERVICE, ConnectivityManager.class,
                new StaticApplicationContextServiceFetcher<ConnectivityManager>() {
            @Override
            public ConnectivityManager createService(Context context) throws ServiceNotFoundException {
                IBinder b = ServiceManager.getServiceOrThrow(Context.CONNECTIVITY_SERVICE);
                IConnectivityManager service = IConnectivityManager.Stub.asInterface(b);
                return new ConnectivityManager(context, service);
            }});

    /**
     * {@hide}
     */
    public ConnectivityManager(Context context, IConnectivityManager service) {
        mContext = Preconditions.checkNotNull(context, "missing context");
        mService = Preconditions.checkNotNull(service, "missing IConnectivityManager");
        sInstance = this;
    }

SystemServer:

                traceBeginAndSlog("StartConnectivityService");
                try {
                    connectivity = new ConnectivityService(
                            context, networkManagement, networkStats, networkPolicy);
                    ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);
                    networkStats.bindConnectivityManager(connectivity);
                    networkPolicy.bindConnectivityManager(connectivity);
                } catch (Throwable e) {
                    reportWtf("starting Connectivity Service", e);
                }
                traceEnd();

所以mService是ConnectivityService。

2.3 ConnectivityService

    @Override
    public void startTethering(int type, ResultReceiver receiver, boolean showProvisioningUi,
            String callerPkg) {
        ConnectivityManager.enforceTetherChangePermission(mContext, callerPkg);
        if (!isTetheringSupported()) {
            receiver.send(ConnectivityManager.TETHER_ERROR_UNSUPPORTED, null);
            return;
        }
        mTethering.startTethering(type, receiver, showProvisioningUi);
    }

2.4 Tethering

    public void startTethering(int type, ResultReceiver receiver, boolean showProvisioningUi) {
        if (!isTetherProvisioningRequired()) {
            enableTetheringInternal(type, true, receiver);
            return;
        }

        if (showProvisioningUi) {
            runUiTetherProvisioningAndEnable(type, receiver);
        } else {
            runSilentTetherProvisioningAndEnable(type, receiver);
        }
    }

暂时先认为打开tethering需要provision吧，继续往下看。

   /**
     * Check if the device requires a provisioning check in order to enable tethering.
     *
     * @return a boolean - {@code true} indicating tether provisioning is required by the carrier.
     */
    @VisibleForTesting
    protected boolean isTetherProvisioningRequired() {
        final TetheringConfiguration cfg = mConfig;
        if (mSystemProperties.getBoolean(DISABLE_PROVISIONING_SYSPROP_KEY, false)
                || cfg.provisioningApp.length == 0) {
            return false;
        }
        if (carrierConfigAffirmsEntitlementCheckNotRequired()) {
            return false;
        }
        return (cfg.provisioningApp.length == 2);
    }

shouProvisioningUi由设置传入，是true

    private void runUiTetherProvisioningAndEnable(int type, ResultReceiver receiver) {
        ResultReceiver proxyReceiver = getProxyReceiver(type, receiver);
        sendUiTetherProvisionIntent(type, proxyReceiver);
    }

    /**
     * Creates a proxy {@link ResultReceiver} which enables tethering if the provisioning result
     * is successful before firing back up to the wrapped receiver.
     *
     * @param type The type of tethering being enabled.
     * @param receiver A ResultReceiver which will be called back with an int resultCode.
     * @return The proxy receiver.
     */
    private ResultReceiver getProxyReceiver(final int type, final ResultReceiver receiver) {
        ResultReceiver rr = new ResultReceiver(null) {
            @Override
            protected void onReceiveResult(int resultCode, Bundle resultData) {
                // If provisioning is successful, enable tethering, otherwise just send the error.
                if (resultCode == TETHER_ERROR_NO_ERROR) {
                    enableTetheringInternal(type, true, receiver);
                } else {
                    sendTetherResult(receiver, resultCode);
                }
            }
        };

        // The following is necessary to avoid unmarshalling issues when sending the receiver
        // across processes.
        Parcel parcel = Parcel.obtain();
        rr.writeToParcel(parcel,0);
        parcel.setDataPosition(0);
        ResultReceiver receiverForSending = ResultReceiver.CREATOR.createFromParcel(parcel);
        parcel.recycle();
        return receiverForSending;
    }

    private void sendUiTetherProvisionIntent(int type, ResultReceiver receiver) {
        Intent intent = new Intent(Settings.ACTION_TETHER_PROVISIONING);
        intent.putExtra(EXTRA_ADD_TETHER_TYPE, type);
        intent.putExtra(EXTRA_PROVISION_CALLBACK, receiver);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        final long ident = Binder.clearCallingIdentity();
        try {
            mContext.startActivityAsUser(intent, UserHandle.CURRENT);
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
    }

Settings有如下类会接收并处理消息

        <activity android:name="TetherProvisioningActivity"
            android:exported="true"
            android:permission="android.permission.TETHER_PRIVILEGED"
            android:excludeFromRecents="true"
            android:theme="@style/Theme.ProvisioningActivity">
            <intent-filter android:priority="1">
                <action android:name="android.settings.TETHER_PROVISIONING_UI" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

/**
 * Activity which acts as a proxy to the tether provisioning app for sanity checks and permission
 * restrictions. Specifically, the provisioning apps require
 * {@link android.permission.CONNECTIVITY_INTERNAL}, while this activity can be started by a caller
 * with {@link android.permission.TETHER_PRIVILEGED}.
 */
public class TetherProvisioningActivity extends Activity {
    private static final int PROVISION_REQUEST = 0;
    private static final String TAG = "TetherProvisioningAct";
    private static final String EXTRA_TETHER_TYPE = "TETHER_TYPE";
    private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
    private ResultReceiver mResultReceiver;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mResultReceiver = (ResultReceiver)getIntent().getParcelableExtra(
                ConnectivityManager.EXTRA_PROVISION_CALLBACK);

        int tetherType = getIntent().getIntExtra(ConnectivityManager.EXTRA_ADD_TETHER_TYPE,
                ConnectivityManager.TETHERING_INVALID);
        String[] provisionApp = getResources().getStringArray(
                com.android.internal.R.array.config_mobile_hotspot_provision_app);

        Intent intent = new Intent(Intent.ACTION_MAIN);
        intent.setClassName(provisionApp[0], provisionApp[1]);
        intent.putExtra(EXTRA_TETHER_TYPE, tetherType);
        if (DEBUG) {
            Log.d(TAG, "Starting provisioning app: " + provisionApp[0] + "." + provisionApp[1]);
        }

        if (getPackageManager().queryIntentActivities(intent,
                PackageManager.MATCH_DEFAULT_ONLY).isEmpty()) {
            Log.e(TAG, "Provisioning app is configured, but not available.");
            mResultReceiver.send(ConnectivityManager.TETHER_ERROR_PROVISION_FAILED, null);
            finish();
            return;
        }

        startActivityForResultAsUser(intent, PROVISION_REQUEST, UserHandle.CURRENT);
    }   

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent intent) {
        super.onActivityResult(requestCode, resultCode, intent);
        if (requestCode == PROVISION_REQUEST) {
            if (DEBUG) Log.d(TAG, "Got result from app: " + resultCode);
            int result = resultCode == Activity.RESULT_OK ?
                    ConnectivityManager.TETHER_ERROR_NO_ERROR :
                    ConnectivityManager.TETHER_ERROR_PROVISION_FAILED;
            mResultReceiver.send(result, null);
            finish();
        }
    }   
}

具体provision app需要vendor具体配置，看framework/base/core/res/res是空的

./values/config.xml:407:    <string-array translatable="false" name="config_mobile_hotspot_provision_app">
./values/config.xml-408-    <!--
./values/config.xml-409-        <item>com.example.provisioning</item>
./values/config.xml-410-        <item>com.example.provisioning.Activity</item>
./values/config.xml-411-    -->
./values/config.xml-412-    </string-array>

完成后回调onActivityResult，发送ConnectivityManager.TETHER_ERROR_NO_ERROR，继续调用enableTetheringInternal方法。

        ResultReceiver rr = new ResultReceiver(null) {
            @Override
            protected void onReceiveResult(int resultCode, Bundle resultData) {
                // If provisioning is successful, enable tethering, otherwise just send the error.
                if (resultCode == TETHER_ERROR_NO_ERROR) {
                    enableTetheringInternal(type, true, receiver);
                } else {
                    sendTetherResult(receiver, resultCode);
                }
            }
        };

   /**
     * Enables or disables tethering for the given type. This should only be called once
     * provisioning has succeeded or is not necessary. It will also schedule provisioning rechecks
     * for the specified interface.
     */
    private void enableTetheringInternal(int type, boolean enable, ResultReceiver receiver) {
        boolean isProvisioningRequired = enable && isTetherProvisioningRequired();
        int result;
        switch (type) {
            case TETHERING_WIFI:
                result = setWifiTethering(enable);
                if (isProvisioningRequired && result == TETHER_ERROR_NO_ERROR) {
                    scheduleProvisioningRechecks(type);
                }
                sendTetherResult(receiver, result);
                break;
            case TETHERING_USB:
                result = setUsbTethering(enable);
                if (isProvisioningRequired && result == TETHER_ERROR_NO_ERROR) {
                    scheduleProvisioningRechecks(type);
                }
                sendTetherResult(receiver, result);
                break;
            case TETHERING_BLUETOOTH:
                setBluetoothTethering(enable, receiver);
                break;
            default:
                Log.w(TAG, "Invalid tether type.");
                sendTetherResult(receiver, TETHER_ERROR_UNKNOWN_IFACE);
        }
    }

可以看到tethering不特指WiFi热点，总体包含蓝牙WiFi热点和Usb。

我们还是走不需要provision的流程把。。。

    private int setWifiTethering(final boolean enable) {
        int rval = TETHER_ERROR_MASTER_ERROR;
        final long ident = Binder.clearCallingIdentity();
        try {
            synchronized (mPublicSync) {
                mWifiTetherRequested = enable;
                final WifiManager mgr = getWifiManager();
                if ((enable && mgr.startSoftAp(null /* use existing wifi config */)) ||
                    (!enable && mgr.stopSoftAp())) {
                    rval = TETHER_ERROR_NO_ERROR;
                }
            }
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
        return rval;
    }

这边会走到WifiManager里去，wifi config为空表示使用已有的WiFi config。后面的senTetherResult就是回调之前的receiver通知执行结果。

2.5 WifiManager

    /**
     * Start SoftAp mode with the specified configuration.
     * Note that starting in access point mode disables station
     * mode operation
     * @param wifiConfig SSID, security and channel details as
     *        part of WifiConfiguration
     * @return {@code true} if the operation succeeds, {@code false} otherwise
     *
     * @hide
     */
    public boolean startSoftAp(@Nullable WifiConfiguration wifiConfig) {
        try {
            return mService.startSoftAp(wifiConfig);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

2.6 WifiServiceImpl

    /**
     * see {@link android.net.wifi.WifiManager#startSoftAp(WifiConfiguration)}
     * @param wifiConfig SSID, security and channel details as part of WifiConfiguration
     * @return {@code true} if softap start was triggered
     * @throws SecurityException if the caller does not have permission to start softap
     */
    @Override
    public boolean startSoftAp(WifiConfiguration wifiConfig) {
        // NETWORK_STACK is a signature only permission.
        enforceNetworkStackPermission();

        mLog.info("startSoftAp uid=%").c(Binder.getCallingUid()).flush();

        synchronized (mLocalOnlyHotspotRequests) {
            // If a tethering request comes in while we have LOHS running (or requested), call stop
            // for softap mode and restart softap with the tethering config.
            if (!mLocalOnlyHotspotRequests.isEmpty()) {
                stopSoftApInternal();
            }

            return startSoftApInternal(wifiConfig, WifiManager.IFACE_IP_MODE_TETHERED);
        }
    }

    /**
     * Internal method to start softap mode. Callers of this method should have already checked
     * proper permissions beyond the NetworkStack permission.
     */
    private boolean startSoftApInternal(WifiConfiguration wifiConfig, int mode) {
        mLog.trace("startSoftApInternal uid=% mode=%")
                .c(Binder.getCallingUid()).c(mode).flush();

        // null wifiConfig is a meaningful input for CMD_SET_AP
        if (wifiConfig == null || isValid(wifiConfig)) {
            SoftApModeConfiguration softApConfig = new SoftApModeConfiguration(mode, wifiConfig);
            mWifiController.sendMessage(CMD_SET_AP, 1, 0, softApConfig);
            return true;
        }
        Slog.e(TAG, "Invalid WifiConfiguration");
        return false;
    }

这边对空的wificonfig包装成了SoftApModeConfiguration接由WifiController处理。

    /**
     * Enqueue a message to this state machine.
     *
     * Message is ignored if state machine has quit.
     */
    public void sendMessage(int what, int arg1, int arg2, Object obj) {
        // mSmHandler can be null if the state machine has quit.
        SmHandler smh = mSmHandler;
        if (smh == null) return;

        smh.sendMessage(obtainMessage(what, arg1, arg2, obj));
    }

2.7 WifiController

ApEnabledState会对该消息进行对应的处理

                case CMD_SET_AP:
                    if (msg.arg1 == 0) {
                        mWifiStateMachine.setHostApRunning(null, false);
                        mPendingState = getNextWifiState();
                    }
                    break;

2.8 WifiStateMachine

    /**
     * TODO: doc
     */
    public void setHostApRunning(SoftApModeConfiguration wifiConfig, boolean enable) {
        if (enable) {
            sendMessage(CMD_START_AP, wifiConfig);
        } else {
            sendMessage(CMD_STOP_AP);
        }
    }

看了一圈只有InitialState对该消息有正确响应

                case CMD_START_AP:
                    transitionTo(mSoftApState);
                    break;

InitialState exit()方法为空，看下SoftApState的enter方法

    class SoftApState extends State {
        private SoftApManager mSoftApManager;
        private String mIfaceName;
        private int mMode;

        private class SoftApListener implements SoftApManager.Listener {
            @Override
            public void onStateChanged(int state, int reason) {
                if (state == WIFI_AP_STATE_DISABLED) {
                    sendMessage(CMD_AP_STOPPED);
                } else if (state == WIFI_AP_STATE_FAILED) {
                    sendMessage(CMD_START_AP_FAILURE);
                }

                setWifiApState(state, reason, mIfaceName, mMode);
            }
        }

        @Override
        public void enter() {
            final Message message = getCurrentMessage();
            if (message.what != CMD_START_AP) {
                throw new RuntimeException("Illegal transition to SoftApState: " + message);
            }
            SoftApModeConfiguration config = (SoftApModeConfiguration) message.obj;
            mMode = config.getTargetMode();

            IApInterface apInterface = null;
            Pair<Integer, IApInterface> statusAndInterface = mWifiNative.setupForSoftApMode();
            if (statusAndInterface.first == WifiNative.SETUP_SUCCESS) {
                apInterface = statusAndInterface.second;
            } else {
                incrementMetricsForSetupFailure(statusAndInterface.first);
            }
            if (apInterface == null) {
                setWifiApState(WIFI_AP_STATE_FAILED,
                        WifiManager.SAP_START_FAILURE_GENERAL, null, mMode);
                /**
                 * Transition to InitialState to reset the
                 * driver/HAL back to the initial state.
                 */
                transitionTo(mInitialState);
                return;
            }

            try {
                mIfaceName = apInterface.getInterfaceName();
            } catch (RemoteException e) {
                // Failed to get the interface name. The name will not be available for
                // the enabled broadcast, but since we had an error getting the name, we most likely
                // won't be able to fully start softap mode.
            }

            checkAndSetConnectivityInstance();
            mSoftApManager = mWifiInjector.makeSoftApManager(mNwService,
                                                             new SoftApListener(),
                                                             apInterface,
                                                             config.getWifiConfiguration());
            mSoftApManager.start();
            mWifiStateTracker.updateState(WifiStateTracker.SOFT_AP);
        }

这边的调用流程和WiFi的启动流程有点类似。先梳理到这，后面应该是硬菜。。。

3. 总结