android-wifi(7.1)漫游部分逻辑
漫游说明:一个场所有若干台AP,相同的SSID不同的BSSID,STA可以在这个场所的不同地方自动连接信号好的AP.
协议规定:
相关类
WifiQualifiedNetworkSelector.java
WifiStateMachine.java
WifiConnectivityManager.handleScanResults
{
WifiConfiguration candidate =
mQualifiedNetworkSelector.selectQualifiedNetwork//根据扫描结果选择候选得分最高的网络
//有得分较高的网络进行连接
connectToNetwork(candidate)
}
WifiQualifiedNetworkSelector.SelectQualifiedNetwork
{
<integer translatable="false" name="config_wifi_framework_RSSI_SCORE_OFFSET">85</integer>
<integer translatable="false" name="config_wifi_framework_RSSI_SCORE_SLOPE">4</integer>
mRssiScoreSlope = context.getResources().getInteger(
R.integer.config_wifi_framework_RSSI_SCORE_SLOPE);//4
mRssiScoreOffset = context.getResources().getInteger(
R.integer.config_wifi_framework_RSSI_SCORE_OFFSET);//85
mSameBssidAward = context.getResources().getInteger(
R.integer.config_wifi_framework_SAME_BSSID_AWARD);
//循环所有的扫描结果找到分数最高的候选网络
//iterate all scan results and find the best candidate with the highest score
for (ScanDetail scanDetail : mScanDetails) {
ScanResult scanResult = scanDetail.getScanResult();
//skip scan result with too weak signals
//跳过信号小于最小值的结果
if ((scanResult.is24GHz() && scanResult.level
< mWifiConfigManager.mThresholdMinimumRssi24.get())
|| (scanResult.is5GHz() && scanResult.level
< mWifiConfigManager.mThresholdMinimumRssi5.get())) {
continue;
}
int highestScore = Integer.MIN_VALUE;
int score;
//计算bssid的分数
score = calculateBssidScore(scanResult, network, mCurrentConnectedNetwork,
(mCurrentBssid == null ? false : mCurrentBssid.equals(scanResult.BSSID)),
(lastUserSelectedNetwork == null ? false : lastUserSelectedNetwork.networkId
== network.networkId), scoreHistory);
/*
//上面方法逻辑如下:
int score = 0;
//calculate the RSSI score
//1.第一个根据2.4和5G进行加分
int rssi = scanResult.level <= mWifiConfigManager.mThresholdSaturatedRssi24.get()
? scanResult.level : mWifiConfigManager.mThresholdSaturatedRssi24.get();
score += (rssi + mRssiScoreOffset) * mRssiScoreSlope;//(rssi+85)*4
if (scanResult.is5GHz()) {//5G的情况
//5GHz band
score += mWifiConfigManager.mBandAward5Ghz.get();
}
//last user selection award
//2.第一个根据上一次用户的选择进行减分
if (sameSelect) {
long timeDifference = mClock.elapsedRealtime()
- mWifiConfigManager.getLastSelectedTimeStamp();
if (timeDifference > 0) {
int bonus = mLastSelectionAward - (int) (timeDifference / 1000 / 60);
score += bonus > 0 ? bonus : 0;
sbuf.append(" User selected it last time " + (timeDifference / 1000 / 60)
+ " minutes ago, bonus:" + bonus);
}
}
//3.相同的网络进行加分
//same network award
if (network == currentNetwork || network.isLinked(currentNetwork)) {
score += mWifiConfigManager.mCurrentNetworkBoost.get();
}
//4.根据相同的BSSID来加分
//same BSSID award
if (sameBssid) {
score += mSameBssidAward;
sbuf.append(" Same BSSID with current association. Bonus: " + mSameBssidAward);
}
//5.根据是否是热点和加密方式设置加分点
if (network.isPasspoint()) {
score += mPasspointSecurityAward;
} else if (!mWifiConfigManager.isOpenNetwork(network)) {
score += mSecurityAward;
}
//6.不能访问网络的惩罚进行减分
if (network.numNoInternetAccessReports > 0 && !network.validatedInternetAccess) {
score -= mNoIntnetPenalty;
}
*/
//更新configurationCandidateForThisScan变量和highestScore 最高的那个网络network将会赋值给configurationCandidateForThisScan
if (score > highestScore) {
highestScore = score;
configurationCandidateForThisScan = network;
potentialCandidate = network;
}
//update the cached candidate 更新候选网络缓存
if (score > status.getCandidateScore() || (score == status.getCandidateScore()
&& status.getCandidate() != null
&& scanResult.level > status.getCandidate().level)) {
status.setCandidate(scanResult);
status.setCandidateScore(score);
}
//用currentHighestScore 来记录当前最高分 如果此次highestScore分和前面的最高分相等则要比较此次和前面最高分的网络的级别
//把最高分的网络类型赋值给scanResultCandidate 并保存在最高分的WifiConfiguration文件中
if (highestScore > currentHighestScore || (highestScore == currentHighestScore
&& scanResultCandidate != null
&& scanResult.level > scanResultCandidate.level)) {
currentHighestScore = highestScore;
scanResultCandidate = scanResult;
networkCandidate = configurationCandidateForThisScan;
networkCandidate.getNetworkSelectionStatus().setCandidate(scanResultCandidate);
}
}
//循环体结束
//其它一些简单步骤后返回networkCandidate
}
WifiConnectivityManager.connectToNetwork
{
//获取当前得分最高的网络
ScanResult scanResultCandidate = candidate.getNetworkSelectionStatus().getCandidate();
String targetBssid = scanResultCandidate.BSSID;
String targetAssociationId = candidate.SSID + " : " + targetBssid;
//漫游状态下networkId是否相同???
if (currentConnectedNetwork != null
&& (currentConnectedNetwork.networkId == candidate.networkId
|| currentConnectedNetwork.isLinked(candidate))) {
localLog("connectToNetwork: Roaming from " + currentAssociationId + " to "
+ targetAssociationId);
mStateMachine.autoRoamToNetwork(candidate.networkId, scanResultCandidate);
} else {
localLog("connectToNetwork: Reconnect from " + currentAssociationId + " to "
+ targetAssociationId);
mStateMachine.autoConnectToNetwork(candidate.networkId, scanResultCandidate.BSSID);
}
}
WifiStateMachine.connectToNetwork()
{
//获取候选网络 得分较高的网络
ScanResult scanResultCandidate = candidate.getNetworkSelectionStatus().getCandidate();
if (scanResultCandidate == null) {
Log.e(TAG, "connectToNetwork: bad candidate - " + candidate
+ " scanResult: " + scanResultCandidate);
return;
}
}
WifiStateMachine.autoRoamToNetwork(int networkId, ScanResult scanResult)
{
sendMessage(CMD_AUTO_ROAM, networkId, 0, scanResult);
}
在ConnectedState会接收和处理此消息
ConnectedState
{
case CMD_AUTO_ROAM:
setTargetBssid(config, bssid);//设置需要漫游到目标的bssid
mTargetNetworkId = netId;//保存漫游网络ID
/* Determine if this is a regular roam (between BSSIDs sharing the same SSID),
or a DBDC roam (between 2.4 & 5GHz networks on different SSID's, but with
matching 16 byte BSSID prefixes):
*/
//确定是正常的漫游-不同的bssid相同的网络名称还是 双频同步-DBDC
WifiConfiguration currentConfig = getCurrentWifiConfiguration();
if (currentConfig != null && currentConfig.isLinked(config)) {
// This is dual band roaming
mWifiMetrics.startConnectionEvent(config, mTargetRoamBSSID,
WifiMetricsProto.ConnectionEvent.ROAM_DBDC);//双频同步记录信息
} else {
// This is regular roaming
mWifiMetrics.startConnectionEvent(config, mTargetRoamBSSID,
WifiMetricsProto.ConnectionEvent.ROAM_ENTERPRISE);//正常的漫游记录信息
}
if (mLastNetworkId != netId) {
//进行漫游连接
if (mWifiConfigManager.selectNetwork(config, /* updatePriorities = */ false,
WifiConfiguration.UNKNOWN_UID) && mWifiNative.reconnect()) {
ret = true;
}
} else {
ret = mWifiNative.reassociate();//重新关联
}
if (ret) {
lastConnectAttemptTimestamp = System.currentTimeMillis();
targetWificonfiguration = mWifiConfigManager.getWifiConfiguration(netId);
// replyToMessage(message, WifiManager.CONNECT_NETWORK_SUCCEEDED);
mAutoRoaming = true;
transitionTo(mRoamingState);//连接成功后转换到漫游状态
}
}
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