Android -- WifiMonitor分析
Android -- WifiMonitor
在Android的Wifi体系中，WifiMonitor承担着分发来自wpa_supplicant底层事件的任务。当上层下达Wifi的扫描、连接等指令后， 底层驱动以及wpa_s进行实际的扫描、连接操作，操作完成后会向上层反馈一个event，通知framework扫描是否结束、连接是否成功。
WifiStateMachine在处理CMD_START_SUPPLICANT消息时，会执行驱动加载、启动wpa_s等操作：
case CMD_START_SUPPLICANT:
if (mWifiNative.loadDriver()) {
try {
mNwService.wifiFirmwareReload(mInterfaceName, "STA");
} catch (Exception e) {
loge("Failed to reload STA firmware " + e);
// Continue
}
try {
// A runtime crash can leave the interface up and
// IP addresses configured, and this affects
// connectivity when supplicant starts up.
// Ensure interface is down and we have no IP
// addresses before a supplicant start.
mNwService.setInterfaceDown(mInterfaceName);
mNwService.clearInterfaceAddresses(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.
*/
mWifiMonitor.killSupplicant(mP2pSupported);
if (WifiNative.startHal() == false) {
/* starting HAL is optional */
loge("Failed to start HAL");
}
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;
启动WifiMonitor，间接调用内部类WifiMonitorSingleton::startMonitoring()方法：
public synchronized void startMonitoring(String iface) {
WifiMonitor m = mIfaceMap.get(iface);
if (m == null) {
Log.e(TAG, "startMonitor called with unknown iface=" + iface);
return;
}
Log.d(TAG, "startMonitoring(" + iface + ") with mConnected = " + mConnected);
if (mConnected) {
m.mMonitoring = true;
m.mStateMachine.sendMessage(SUP_CONNECTION_EVENT);
} else {
if (DBG) Log.d(TAG, "connecting to supplicant");
int connectTries = 0;
while (true) {
if (mWifiNative.connectToSupplicant()) {
m.mMonitoring = true;
m.mStateMachine.sendMessage(SUP_CONNECTION_EVENT);
mConnected = true;
new MonitorThread(mWifiNative, this).start();
break;
}
if (connectTries++ < 5) {
try {
Thread.sleep(1000);
} catch (InterruptedException ignore) {
}
} else {
m.mStateMachine.sendMessage(SUP_DISCONNECTION_EVENT);
Log.e(TAG, "startMonitoring(" + iface + ") failed!");
break;
}
}
}
}
如果是第一次进行监听mConnected为false，进入else分支。先建立与wpa_s的消息通道，建立成功后会向WifiStateMachine发送SUP_CONNECTION_EVENT消息，通知Wifi状态机。
随后，开启事件监听线程：new MonitorThread(mWifiNative, this).start()：
private static class MonitorThread extends Thread {
private final WifiNative mWifiNative;
private final WifiMonitorSingleton mWifiMonitorSingleton;
private final LocalLog mLocalLog = WifiNative.getLocalLog();
public MonitorThread(WifiNative wifiNative, WifiMonitorSingleton wifiMonitorSingleton) {
super("WifiMonitor");
mWifiNative = wifiNative;
mWifiMonitorSingleton = wifiMonitorSingleton;
}
public void run() {
if (DBG) {
Log.d(TAG, "MonitorThread start with mConnected=" +
mWifiMonitorSingleton.mConnected);
}
//noinspection InfiniteLoopStatement
for (;;) {
if (!mWifiMonitorSingleton.mConnected) {
if (DBG) Log.d(TAG, "MonitorThread exit because mConnected is false");
break;
}
String eventStr = mWifiNative.waitForEvent();
// Skip logging the common but mostly uninteresting events
if (eventStr.indexOf(BSS_ADDED_STR) == -1
&& eventStr.indexOf(BSS_REMOVED_STR) == -1) {
if (DBG) Log.d(TAG, "Event [" + eventStr + "]");
mLocalLog.log("Event [" + eventStr + "]");
}
if (mWifiMonitorSingleton.dispatchEvent(eventStr)) {
if (DBG) Log.d(TAG, "Disconnecting from the supplicant, no more events");
break;
}
}
}
} private synchronized boolean dispatchEvent(String eventStr) {
String iface;
// IFNAME=wlan0 ANQP-QUERY-DONE addr=18:cf:5e:26:a4:88 result=SUCCESS
if (eventStr.startsWith("IFNAME=")) {
int space = eventStr.indexOf(' ');
if (space != -1) {
iface = eventStr.substring(7, space);
if (!mIfaceMap.containsKey(iface) && iface.startsWith("p2p-")) {
// p2p interfaces are created dynamically, but we have
// only one P2p state machine monitoring all of them; look
// for it explicitly, and send messages there ..
iface = "p2p0";
}
eventStr = eventStr.substring(space + 1);
} else {
// No point dispatching this event to any interface, the dispatched
// event string will begin with "IFNAME=" which dispatchEvent can't really
// do anything about.
Log.e(TAG, "Dropping malformed event (unparsable iface): " + eventStr);
return false;
}
} else {
// events without prefix belong to p2p0 monitor
iface = "p2p0";
}
if (VDBG) Log.d(TAG, "Dispatching event to interface: " + iface);
WifiMonitor m = mIfaceMap.get(iface);
if (m != null) {
if (m.mMonitoring) {
if (m.dispatchEvent(eventStr, iface)) {
mConnected = false;
return true;
}
return false;
} else {
if (DBG) Log.d(TAG, "Dropping event because (" + iface + ") is stopped");
return false;
}
} else {
if (DBG) Log.d(TAG, "Sending to all monitors because there's no matching iface");
boolean done = false;
boolean isMonitoring = false;
boolean isTerminating = false;
if (eventStr.startsWith(EVENT_PREFIX_STR)
&& eventStr.contains(TERMINATING_STR)) {
isTerminating = true;
}
for (WifiMonitor monitor : mIfaceMap.values()) {
if (monitor.mMonitoring) {
isMonitoring = true;
if (monitor.dispatchEvent(eventStr, iface)) {
done = true;
}
}
}
if (!isMonitoring && isTerminating) {
done = true;
}
if (done) {
mConnected = false;
}
return done;
}
} /* @return true if the event was supplicant disconnection */
private boolean dispatchEvent(String eventStr, String iface) {
if (DBG) {
// Dont log CTRL-EVENT-BSS-ADDED which are too verbose and not handled
if (eventStr != null && !eventStr.contains("CTRL-EVENT-BSS-ADDED")) {
logDbg("WifiMonitor:" + iface + " cnt=" + Integer.toString(eventLogCounter)
+ " dispatchEvent: " + eventStr);
}
}
if (!eventStr.startsWith(EVENT_PREFIX_STR)) {
if (eventStr.startsWith(WPA_EVENT_PREFIX_STR) &&
0 < eventStr.indexOf(PASSWORD_MAY_BE_INCORRECT_STR)) {
mStateMachine.sendMessage(AUTHENTICATION_FAILURE_EVENT, eventLogCounter);
} else if (eventStr.startsWith(WPS_SUCCESS_STR)) {
mStateMachine.sendMessage(WPS_SUCCESS_EVENT);
} else if (eventStr.startsWith(WPS_FAIL_STR)) {
handleWpsFailEvent(eventStr);
} else if (eventStr.startsWith(WPS_OVERLAP_STR)) {
mStateMachine.sendMessage(WPS_OVERLAP_EVENT);
} else if (eventStr.startsWith(WPS_TIMEOUT_STR)) {
mStateMachine.sendMessage(WPS_TIMEOUT_EVENT);
} else if (eventStr.startsWith(P2P_EVENT_PREFIX_STR)) {
handleP2pEvents(eventStr);
} else if (eventStr.startsWith(HOST_AP_EVENT_PREFIX_STR)) {
handleHostApEvents(eventStr);
} else if (eventStr.startsWith(ANQP_DONE_STR)) {
try {
handleAnqpResult(eventStr);
}
catch (IllegalArgumentException iae) {
Log.e(TAG, "Bad ANQP event string: '" + eventStr + "': " + iae);
}
} else if (eventStr.startsWith(GAS_QUERY_PREFIX_STR)) { // !!! clean >>End
handleGasQueryEvents(eventStr);
} else if (eventStr.startsWith(RX_HS20_ANQP_ICON_STR)) {
if (mStateMachine2 != null)
mStateMachine2.sendMessage(RX_HS20_ANQP_ICON_EVENT,
eventStr.substring(RX_HS20_ANQP_ICON_STR_LEN + 1));
} else if (eventStr.startsWith(HS20_PREFIX_STR)) { // !!! <else if (eventName.equals(SCAN_RESULTS_STR))
event = SCAN_RESULTS; /**
* Handle all supplicant events except STATE-CHANGE
* @param event the event type
* @param remainder the rest of the string following the
* event name and " — "
*/
void handleEvent(int event, String remainder) {
if (DBG) {
logDbg("handleEvent " + Integer.toString(event) + " " + remainder);
}
switch (event) {
case DISCONNECTED:
handleNetworkStateChange(NetworkInfo.DetailedState.DISCONNECTED, remainder);
break;
case CONNECTED:
handleNetworkStateChange(NetworkInfo.DetailedState.CONNECTED, remainder);
break;
case SCAN_RESULTS:
mStateMachine.sendMessage(SCAN_RESULTS_EVENT);
break;
case SCAN_FAILED:
mStateMachine.sendMessage(SCAN_FAILED_EVENT);
break;
case UNKNOWN:
if (DBG) {
logDbg("handleEvent unknown: " + Integer.toString(event) + " " + remainder);
}
break;
default:
break;
}
}
WifiStateMachine收到此消息后，调用WifiStateMachine::setScanResults()方法从wpa_s读取扫描结果，并向外界发送WifiManager.SCAN_RESULTS_AVAILABLE_ACTION广播通知应用。
此时一些注册过该广播的应用，例如手机中的Setting app，就能通过调用WifiManager::getScanResults()读取扫描结果了。至此，一个简单的WifiMonitor分发事件的流程结束，其他类型事件的分发跟此过程相似。