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二、向wpa_supplicant发送命令
想象一下在应用程序我们怎么连接wifi:
1打开和关闭wifi
WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
wifi.setWifiEnabled(true);
2扫描附近热点
startScan();之后,接受WifiManager.SCAN_RESULTS_AVAILABLE_ACTION的广播会触发,在这个广播中调用getScanResults()方法可以获得一个List,它里面的每一个条目就是一个可连接的热点。
wifi.startScan();
results = wifi.getScanResults();
一般我们可能都需要做这两步吧,那么这两步会导致wifi状态机做怎么样的改变呢?
首先,用一张图来概括这个过程,然后大家可以顺着这个图的思路分析代码:
2 打开wifi
应用程序中调用
WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
wifi.setWifiEnabled(true);
首先从setWifiEnabled开始,wifi是一个WifiServiceImpl的客户端WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE); ,它会通过binder和WifiServiceImpl的实例交互,也就是我们在WifiService中通过addService方法向系统注册的mImpl对象,忘记的可以回头看看前面。
frameworks/base/wifi/java/android/net/wifi/WifiManager.java
public boolean setWifiEnabled(boolean enabled) {
try {
return mService.setWifiEnabled(enabled);
} catch (RemoteException e) {
return false;
}
}
最终调用的的是WifiServiceImpl中的setWifiEnabled方法:
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiServiceImpl.java
public synchronized boolean setWifiEnabled(boolean enable) {
enforceChangePermission();
Slog.d(TAG, "setWifiEnabled: " + enable + " pid=" + Binder.getCallingPid()
+ ", uid=" + Binder.getCallingUid());
if (DBG) {
Slog.e(TAG, "Invoking mWifiStateMachine.setWifiEnabled\n");
}
/*
* Caller might not have WRITE_SECURE_SETTINGS,
* only CHANGE_WIFI_STATE is enforced
*/
long ident = Binder.clearCallingIdentity();
try {
if (! mSettingsStore.handleWifiToggled(enable)) {
// Nothing to do if wifi cannot be toggled
return true;
}
} finally {
Binder.restoreCallingIdentity(ident);
}
mWifiController.sendMessage(CMD_WIFI_TOGGLED);
return true;
}
这个方法首先要使用mSettingsStore.handleWifiToggled(enable)来判断wifi状态是否可以切换,不能切换就直接返回。如果wifi状态可以切换,那么接下来会使用mWifiController.sendMessage(CMD_WIFI_TOGGLED);来给mWifiController状态机发送一条消息,我们说过mWifiController状态机控制wifi设备的开关灯状态,由此开来这句话是对的哈。
WifiController的processMessage方法会被调用,但是我们还不知道是调用WifiController状态机中哪个状态的processMessage。下面我们先来看一下WifiController的构造函数中添加的状态和初始状态。
WifiController(Context context, WifiServiceImpl service, Looper looper) {
super(TAG, looper);
mContext = context;
mWifiStateMachine = service.mWifiStateMachine;
mSettingsStore = service.mSettingsStore;
mLocks = service.mLocks;
mAlarmManager = (AlarmManager)mContext.getSystemService(Context.ALARM_SERVICE);
Intent idleIntent = new Intent(ACTION_DEVICE_IDLE, null);
mIdleIntent = PendingIntent.getBroadcast(mContext, IDLE_REQUEST, idleIntent, 0);
addState(mDefaultState);
addState(mApStaDisabledState, mDefaultState);
addState(mStaEnabledState, mDefaultState);
addState(mDeviceActiveState, mStaEnabledState);
addState(mDeviceInactiveState, mStaEnabledState);
addState(mScanOnlyLockHeldState, mDeviceInactiveState);
addState(mFullLockHeldState, mDeviceInactiveState);
addState(mFullHighPerfLockHeldState, mDeviceInactiveState);
addState(mNoLockHeldState, mDeviceInactiveState);
addState(mStaDisabledWithScanState, mDefaultState);
addState(mApEnabledState, mDefaultState);
addState(mEcmState, mDefaultState);
boolean isAirplaneModeOn = mSettingsStore.isAirplaneModeOn();
boolean isWifiEnabled = mSettingsStore.isWifiToggleEnabled();
boolean isScanningAlwaysAvailable = mSettingsStore.isScanAlwaysAvailable();
log("isAirplaneModeOn = " + isAirplaneModeOn +
", isWifiEnabled = " + isWifiEnabled +
", isScanningAvailable = " + isScanningAlwaysAvailable);
if (isScanningAlwaysAvailable) {
setInitialState(mStaDisabledWithScanState);
} else {
setInitialState(mApStaDisabledState);
}
我们刚开始打开wifi,WifiController状态机刚运行,所以此时状态机的状态一定是初始状态,可以看到我们的初始状态是mApStaDisabledState,所以下面我们来看一下WifiController的mApStaDisabledState的processMessage方法
class ApStaDisabledState extends State {
private int mDeferredEnableSerialNumber = 0;
private boolean mHaveDeferredEnable = false;
private long mDisabledTimestamp;
@Override
public void enter() {
mWifiStateMachine.setSupplicantRunning(false);
// Supplicant can't restart right away, so not the time we switched off
mDisabledTimestamp = SystemClock.elapsedRealtime();
mDeferredEnableSerialNumber++;
mHaveDeferredEnable = false;
mWifiStateMachine.clearANQPCache();
}
@Override
public boolean processMessage(Message msg) {
switch (msg.what) {
case CMD_WIFI_TOGGLED:
case CMD_AIRPLANE_TOGGLED:
if (mSettingsStore.isWifiToggleEnabled()) {
if (doDeferEnable(msg)) {
if (mHaveDeferredEnable) {
// have 2 toggles now, inc serial number an ignore both
mDeferredEnableSerialNumber++;
}
mHaveDeferredEnable = !mHaveDeferredEnable;
break;
}
if (mDeviceIdle == false) {
transitionTo(mDeviceActiveState);
} else {
checkLocksAndTransitionWhenDeviceIdle();
}
} else if (mSettingsStore.isScanAlwaysAvailable()) {
transitionTo(mStaDisabledWithScanState);
}
break;
....
上面主要做了如下两个操作:
1.若500毫秒内重复打开或者关闭wifi不做处理
2.将当前WifiController中的ApStaDisabledState状态转换到DeviceActiveState
DeviceActiveState为StaEnabledState的子状态,所以会先调用父状态的enter()函数,然后调用子状态的enter()函数。
2.1DeviceActiveState
但是我们这里先来看看最后调到的DeviceActiveState的enter()函数,为什么先看DeviceActiveState呢,因为DeviceActiveState的enter()函数没干什么
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiController.java
/* Parent: StaEnabledState */
class DeviceActiveState extends State {
@Override
public void enter() {
mWifiStateMachine.setOperationalMode(WifiStateMachine.CONNECT_MODE);
mWifiStateMachine.setDriverStart(true);
mWifiStateMachine.setHighPerfModeEnabled(false);
}
...
}
2.1.1.setOperationalMode 这里设置模式 可扫描、可连接。
STA的3个操作状态:CONNECT_MODE,SCAN_ONLY_MODE,SCAN_ONLY_WIFI_OFF_MODE
*在CONNECT_MODE中,STA可以扫描并连接到接入点
*在SCAN_ONLY_MODE中,STA只能扫描接入点
*在SCAN_ONLY_WIFI_OFF_MODE中,STA只能扫描(wifi关闭状态下)
2.1.2.setDriverStart(true) 发送CMD_START_DRIVER 消息。该消息在DriverStartedState中处理。
case CMD_START_DRIVER:
if (mInDelayedStop) {
mInDelayedStop = false;
mDelayedStopCounter++;
mAlarmManager.cancel(mDriverStopIntent);
if (DBG) log("Delayed stop ignored due to start");
if (mOperationalMode == CONNECT_MODE) {
mWifiConfigStore.enableAllNetworks();
}
}
break;
如果正在延时关闭驱动,则取消关闭。并将保存的wifi都Enable。
2.1.3.setHighPerfModeEnabled暂时不清楚什么情况。
2.2 StaEnabledState
再来看看DeviceActiveState父状态StaEnabledState的enter()函数:
class StaEnabledState extends State {
@Override
public void enter() {
mWifiStateMachine.setSupplicantRunning(true);
}
...
}
}
调用mWifiStateMachine.setSupplicantRunning(true);
/**
* TODO: doc
*/
public void setSupplicantRunning(boolean enable) {
if (enable) {
sendMessage(CMD_START_SUPPLICANT);
} else {
sendMessage(CMD_STOP_SUPPLICANT);
}
}
mWifiStateMachine.setSupplicantRunning(true),WifiStateMachine发送Message--CMD_STAET_SUPPLICANT。
WIfiStateMachine初始状态为InitialState
看看WIfiStateMachine的InitialState处理该消息
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiStateMachine.java
class InitialState extends State {
@Override
public boolean processMessage(Message message) {
switch (message.what) {
case CMD_START_SUPPLICANT:
//加载Wifi驱动
if (mWifiNative.loadDriver()) {
try {//加载固件
mNwService.wifiFirmwareReload(mInterfaceName, "STA");
} catch (Exception e) {
}
try {
// A runtime crash can leave the interface up and
// this affects connectivity when supplicant starts up.
// Ensure interface is down before a supplicant start.
mNwService.setInterfaceDown(mInterfaceName);
// Set privacy extensions
mNwService.setInterfaceIpv6PrivacyExtensions(mInterfaceName, true);
// IPv6 is enabled only as long as access point is connected since:
// - IPv6 addresses and routes stick around after disconnection
// - kernel is unaware when connected and fails to start IPv6 negotiation
// - kernel can start autoconfiguration when 802.1x is not complete
mNwService.disableIpv6(mInterfaceName);
} catch (RemoteException re) {
loge("Unable to change interface settings: " + re);
} catch (IllegalStateException ie) {
loge("Unable to change interface settings: " + ie);
}
/* Stop a running supplicant after a runtime restart
* Avoids issues with drivers that do not handle interface down
* on a running supplicant properly.
*/
mWifiNative.killSupplicant(mP2pSupported);
//开启wpa_supplicant
if(mWifiNative.startSupplicant(mP2pSupported)) {
setWifiState(WIFI_STATE_ENABLING);
if (DBG) log("Supplicant start successful");
mWifiMonitor.startMonitoring();
transitionTo(mSupplicantStartingState);
} else {
loge("Failed to start supplicant!");
}
} else {
loge("Failed to load driver");
}
break;
//.......
}
1.WifiNative.loadDriver():加载Wifi驱动。
WifiNative.loadDriver()–>android_net_wifi_wifi.cpp(android_net_wifi_loadDriver)
->wifi.c(wifi_load_driver)。
2.mNwService.wifiFirmwareReload(mInterfaceName, “STA”); 加载固件
3.mWifiNative.startSupplicant(mP2pSupported) 先保证没有运行的wpa supplicant,然后开启wpa supplicant,其中参数mP2pSupported表示是否支持wifi 直连。
WifiNative.startSupplicant()–>android_net_wifi_wifi.cpp(android_net_wifi_startSupplicant)
->wifi.c(wifi_start_supplicant)。
4.setWifiState(WIFI_STATE_ENABLING) 发送广播(wifi状态改变 ,正在开启)。
5.mWifiMonitor.startMonitoring()
WifiMonitor创建一个线程MonitorThrad
1)connectToSupplicant最终调到wifi.c 中的wifi_connect_on_socket_path。在该函数中,将通过wpa_ctrl_open函数分别创 建两个socket,一个是ctrl_conn, 用于向wpa_supplicant发送命令并接收response, 另一个是monitor_conn, 它一直阻塞等待从wpa_supplicant过来的event。连接成功后WifiMonitor会向WifiStateMachine发送一个代表socket通信建立成功的消息:SUP_CONNECTION_EVENT。
2)mWifiNative.waitForEvent-》wifi_wait_on_socket ,循环调用该函数,接收底层事件并分发处理。
6.transitionTo(mSupplicantStartingState): WifiStateMachine切换到SupplicantStartingState状态。步骤5是在另一个线程中运行,并且是耗时操作,所以WifiStateMachine先切换到SupplicantStartingState状态,然后接收到SUP_CONNECTION_EVENT消息。
2.3 SupplicantStartingState
下面看看如何处理SUP_CONNECTION_EVENT消息。
class SupplicantStartingState extends State {
@Override
public boolean processMessage(Message message) {
switch(message.what) {
case WifiMonitor.SUP_CONNECTION_EVENT:
if (DBG) log("Supplicant connection established");
setWifiState(WIFI_STATE_ENABLED);
mSupplicantRestartCount = 0;
/* Reset the supplicant state to indicate the supplicant
* state is not known at this time */
mSupplicantStateTracker.sendMessage(CMD_RESET_SUPPLICANT_STATE);
/* Initialize data structures */
mLastBssid = null;
mLastNetworkId = WifiConfiguration.INVALID_NETWORK_ID;
mLastSignalLevel = -1;
mWifiInfo.setMacAddress(mWifiNative.getMacAddress());
mWifiConfigStore.loadAndEnableAllNetworks();
initializeWpsDetails();
sendSupplicantConnectionChangedBroadcast(true);
transitionTo(mDriverStartedState);
break;
//......
}
1.setWifiState(WIFI_STATE_ENABLED),发送WIFI_STATE_ENABLED的广播。
2.WifiConfigStore.loadAndEnableAllNetworks() 加载并enable所有保存在wpa_supplicant中的AP。这样会使这些保存的wifi实现自动重连。
3.transitionTo(mDriverStartedState)切换到DriverStartedState状态。
DriverStartedState是SupplicantStartedState的子状态,所以先后运行SupplicantStartedState、DriverStartedState的enter方法。
2.4 SupplicantStartedState
class SupplicantStartedState extends State {
@Override
public void enter() {
/* Wifi is available as long as we have a connection to supplicant */
mNetworkInfo.setIsAvailable(true);
int defaultInterval = mContext.getResources().getInteger(
R.integer.config_wifi_supplicant_scan_interval);
mSupplicantScanIntervalMs = Settings.Global.getLong(mContext.getContentResolver(),
Settings.Global.WIFI_SUPPLICANT_SCAN_INTERVAL_MS,
defaultInterval);
//设置扫描时间间隔。
mWifiNative.setScanInterval((int)mSupplicantScanIntervalMs / 1000);
}
//.....
1.mNetworkInfo.setIsAvailable(true); 连接到wpa_supplicant,就可以使用wifi。
2.frameworks/base/core/res/res/values/config.xml中可以修改config_wifi_supplicant_scan_interval 的值。
3.setScanInterval 设置wifi扫描间隔时间。
***2.5 DriverStartedState***
class DriverStartedState extends State {
@Override
public void enter() {
mIsRunning = true;
mInDelayedStop = false;
mDelayedStopCounter++;
updateBatteryWorkSource(null);
/**
* Enable bluetooth coexistence scan mode when bluetooth connection is active.
* When this mode is on, some of the low-level scan parameters used by the
* driver are changed to reduce interference with bluetooth
*/
mWifiNative.setBluetoothCoexistenceScanMode(mBluetoothConnectionActive);
/* set country code */
setCountryCode();
/* set frequency band of operation */
setFrequencyBand();
/* initialize network state */
setNetworkDetailedState(DetailedState.DISCONNECTED);
/* Remove any filtering on Multicast v6 at start */
mWifiNative.stopFilteringMulticastV6Packets();
/* Reset Multicast v4 filtering state */
if (mFilteringMulticastV4Packets.get()) {
mWifiNative.startFilteringMulticastV4Packets();
} else {
mWifiNative.stopFilteringMulticastV4Packets();
}
if (mOperationalMode != CONNECT_MODE) {
mWifiNative.disconnect();
transitionTo(mScanModeState);
} else {
/* Driver stop may have disabled networks, enable right after start */
mWifiConfigStore.enableAllNetworks();
mWifiNative.reconnect();
// Status pulls in the current supplicant state and network connection state
// events over the monitor connection. This helps framework sync up with
// current supplicant state
mWifiNative.status();
transitionTo(mDisconnectedState);
}
// We may have missed screen update at boot
if (mScreenBroadcastReceived.get() == false) {
PowerManager powerManager = (PowerManager)mContext.getSystemService(
Context.POWER_SERVICE);
handleScreenStateChanged(powerManager.isScreenOn());
} else {
// Set the right suspend mode settings
mWifiNative.setSuspendOptimizations(mSuspendOptNeedsDisabled == 0
&& mUserWantsSuspendOpt.get());
}
mWifiNative.setPowerSave(true);
if (mP2pSupported) mWifiP2pChannel.sendMessage(WifiStateMachine.CMD_ENABLE_P2P);
final Intent intent = new Intent(WifiManager.WIFI_SCAN_AVAILABLE);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);
intent.putExtra(WifiManager.EXTRA_SCAN_AVAILABLE, WIFI_STATE_ENABLED);
mContext.sendStickyBroadcastAsUser(intent, UserHandle.ALL);
}
//.....
setBluetoothCoexistenceScanMode 启用蓝牙连接时启用蓝牙共存扫描模式。当此模式打开时,驱动程序使用的一些低级扫描参数会被更改,以减少对蓝牙的干扰。
mOperationalMode 默认为CONNECT_MODE,enableAllNetworks 将保存的wifi置为可连接的,并进行重连。
mWifiNative.status() 将wpa_supplicant中状态进行同步。
切换到DisconnectedState状态。