Android -- WifiMonitor

時間 2019-11-16

原文原文鏈接

在Android的Wifi體系中，WifiMonitor承擔着分發來自wpa_supplicant底層事件的任務。當上層下達Wifi的掃描、鏈接等指令後，底層驅動以及wpa_s進行實際的掃描、鏈接操做，操做完成後會向上層反饋一個event，通知framework掃描是否結束、鏈接是否成功。app

WifiStateMachine在處理CMD_START_SUPPLICANT消息時，會執行驅動加載、啓動wpa_s等操做：
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;
同時調用WifiMonitor::startMonitoring()來開啓WifiMonitor進程。ide

啓動WifiMonitor，間接調用內部類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;
}
}
}
}
爲了監聽wpa_supplicant的事件，須要先創建與wpa_s的消息通道，這一步調用WifiNative.connectToSupplicant()實現。函數

若是是第一次進行監聽mConnected爲false，進入else分支。先創建與wpa_s的消息通道，創建成功後會向WifiStateMachine發送SUP_CONNECTION_EVENT消息，通知Wifi狀態機。oop

隨後，開啓事件監聽線程：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;
}
}
}
}
這裏有兩個重要函數：調用WifiNative.waitForEvent()接受來自wpa_s的事件；調用WifiMonitorSingleton.dispatchEvent(eventStr)分發來自wpa_s的底層event：
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;
}
}
解析eventStr，調用相應interface的WifiMonitor::dispatchEvent()方法分發具體的事件給WifiStateMachine處理：
/* @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)) { // !!! <<End
handleHs20Events(eventStr);
} else if (eventStr.startsWith(REQUEST_PREFIX_STR)) {
handleRequests(eventStr);
} else if (eventStr.startsWith(TARGET_BSSID_STR)) {
handleTargetBSSIDEvent(eventStr);
} else if (eventStr.startsWith(ASSOCIATED_WITH_STR)) {
handleAssociatedBSSIDEvent(eventStr);
} else if (eventStr.startsWith(AUTH_EVENT_PREFIX_STR) &&
eventStr.endsWith(AUTH_TIMEOUT_STR)) {
mStateMachine.sendMessage(AUTHENTICATION_FAILURE_EVENT);
} else {
if (DBG) Log.w(TAG, "couldn't identify event type - " + eventStr);
}
eventLogCounter++;
return false;
}

String eventName = eventStr.substring(EVENT_PREFIX_LEN_STR);
int nameEnd = eventName.indexOf(' ');
if (nameEnd != -1)
eventName = eventName.substring(0, nameEnd);
if (eventName.length() == 0) {
if (DBG) Log.i(TAG, "Received wpa_supplicant event with empty event name");
eventLogCounter++;
return false;
}
/*
* Map event name into event enum
*/
int event;
if (eventName.equals(CONNECTED_STR))
event = CONNECTED;
else if (eventName.equals(DISCONNECTED_STR))
event = DISCONNECTED;
else if (eventName.equals(STATE_CHANGE_STR))
event = STATE_CHANGE;
else if (eventName.equals(SCAN_RESULTS_STR))
event = SCAN_RESULTS;
else if (eventName.equals(SCAN_FAILED_STR))
event = SCAN_FAILED;
else if (eventName.equals(LINK_SPEED_STR))
event = LINK_SPEED;
else if (eventName.equals(TERMINATING_STR))
event = TERMINATING;
else if (eventName.equals(DRIVER_STATE_STR))
event = DRIVER_STATE;
else if (eventName.equals(EAP_FAILURE_STR))
event = EAP_FAILURE;
else if (eventName.equals(ASSOC_REJECT_STR))
event = ASSOC_REJECT;
else if (eventName.equals(TEMP_DISABLED_STR)) {
event = SSID_TEMP_DISABLE;
} else if (eventName.equals(REENABLED_STR)) {
event = SSID_REENABLE;
} else if (eventName.equals(BSS_ADDED_STR)) {
event = BSS_ADDED;
} else if (eventName.equals(BSS_REMOVED_STR)) {
event = BSS_REMOVED;
} else
event = UNKNOWN;

String eventData = eventStr;
if (event == DRIVER_STATE || event == LINK_SPEED)
eventData = eventData.split(" ")[1];
else if (event == STATE_CHANGE || event == EAP_FAILURE) {
int ind = eventStr.indexOf(" ");
if (ind != -1) {
eventData = eventStr.substring(ind + 1);
}
} else {
int ind = eventStr.indexOf(" - ");
if (ind != -1) {
eventData = eventStr.substring(ind + 3);
}
}

if ((event == SSID_TEMP_DISABLE)||(event == SSID_REENABLE)) {
String substr = null;
int netId = -1;
int ind = eventStr.indexOf(" ");
if (ind != -1) {
substr = eventStr.substring(ind + 1);
}
if (substr != null) {
String status[] = substr.split(" ");
for (String key : status) {
if (key.regionMatches(0, "id=", 0, 3)) {
int idx = 3;
netId = 0;
while (idx < key.length()) {
char c = key.charAt(idx);
if ((c >= 0x30) && (c <= 0x39)) {
netId *= 10;
netId += c - 0x30;
idx++;
} else {
break;
}
}
}
}
}
mStateMachine.sendMessage((event == SSID_TEMP_DISABLE)?
SSID_TEMP_DISABLED:SSID_REENABLED, netId, 0, substr);
} else if (event == STATE_CHANGE) {
handleSupplicantStateChange(eventData);
} else if (event == DRIVER_STATE) {
handleDriverEvent(eventData);
} else if (event == TERMINATING) {
/**
* Close the supplicant connection if we see
* too many recv errors
*/
if (eventData.startsWith(WPA_RECV_ERROR_STR)) {
if (++sRecvErrors > MAX_RECV_ERRORS) {
if (DBG) {
Log.d(TAG, "too many recv errors, closing connection");
}
} else {
eventLogCounter++;
return false;
}
}

// Notify and exit
mStateMachine.sendMessage(SUP_DISCONNECTION_EVENT, eventLogCounter);
return true;
} else if (event == EAP_FAILURE) {
if (eventData.startsWith(EAP_AUTH_FAILURE_STR)) {
logDbg("WifiMonitor send auth failure (EAP_AUTH_FAILURE) ");
mStateMachine.sendMessage(AUTHENTICATION_FAILURE_EVENT, eventLogCounter);
}
} else if (event == ASSOC_REJECT) {
Matcher match = mAssocRejectEventPattern.matcher(eventData);
String BSSID = "";
int status = -1;
if (!match.find()) {
if (DBG) Log.d(TAG, "Assoc Reject: Could not parse assoc reject string");
} else {
BSSID = match.group(1);
try {
status = Integer.parseInt(match.group(2));
} catch (NumberFormatException e) {
status = -1;
}
}
mStateMachine.sendMessage(ASSOCIATION_REJECTION_EVENT, eventLogCounter, status, BSSID);
} else if (event == BSS_ADDED && !VDBG) {
// Ignore that event - it is not handled, and dont log it as it is too verbose
} else if (event == BSS_REMOVED && !VDBG) {
// Ignore that event - it is not handled, and dont log it as it is too verbose
} else {
handleEvent(event, eventData);
}
sRecvErrors = 0;
eventLogCounter++;
return false;
}
這裏咱們假設事先下發的是一個wifi掃描的指令，wpa_s反饋event通知wifi掃描的結果：
else if (eventName.equals(SCAN_RESULTS_STR))
event = SCAN_RESULTS;
根據實現的一些匹配規則，最後進入handleEvent()函數：
/**
* 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;
}
}
此處event是SCAN_RESULTS，向WifiStateMachine發送SCAN_RESULTS_EVENT消息，告知它掃描已經結束，能夠去讀取掃描結果了。這樣，處理流程就用返回到Wifi狀態機中。this

WifiStateMachine收到此消息後，調用WifiStateMachine::setScanResults()方法從wpa_s讀取掃描結果，並向外界發送WifiManager.SCAN_RESULTS_AVAILABLE_ACTION廣播通知應用。spa

此時一些註冊過該廣播的應用，例如手機中的Setting app，就能經過調用WifiManager::getScanResults()讀取掃描結果了。至此，一個簡單的WifiMonitor分發事件的流程結束，其餘類型事件的分發跟此過程類似。
.net

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