Android(安卓)P WiFi自动连接评分机制

1、WifiConnectivityManager的初始化

frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiStateMachine.java

private void setupClientMode() {    Log.d(TAG, "setupClientMode() ifacename = " + mInterfaceName);    mWifiStateTracker.updateState(WifiStateTracker.INVALID);    if (mWifiConnectivityManager == null) {        synchronized (mWifiReqCountLock) {            mWifiConnectivityManager =                    mWifiInjector.makeWifiConnectivityManager(mWifiInfo,                                                              hasConnectionRequests());            mWifiConnectivityManager.setUntrustedConnectionAllowed(mUntrustedReqCount > 0);            mWifiConnectivityManager.handleScreenStateChanged(mScreenOn);        }    }

frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiInjector.java

public WifiConnectivityManager makeWifiConnectivityManager(WifiInfo wifiInfo,                                                           boolean hasConnectionRequests) {    return new WifiConnectivityManager(mContext, getScoringParams(),            mWifiStateMachine, getWifiScanner(),            mWifiConfigManager, wifiInfo, mWifiNetworkSelector, mWifiConnectivityHelper,            mWifiLastResortWatchdog, mOpenNetworkNotifier, mCarrierNetworkNotifier,            mCarrierNetworkConfig, mWifiMetrics, mWifiStateMachineHandlerThread.getLooper(),            mClock, mConnectivityLocalLog, hasConnectionRequests, mFrameworkFacade,            mSavedNetworkEvaluator, mScoredNetworkEvaluator, mPasspointNetworkEvaluator);}

构造方法里注册了3个NetworkEvaluator
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiConnectivityManager.java

WifiConnectivityManager(Context context, ScoringParams scoringParams,        WifiStateMachine stateMachine,        WifiScanner scanner, WifiConfigManager configManager, WifiInfo wifiInfo,    // Register the network evaluators    mNetworkSelector.registerNetworkEvaluator(savedNetworkEvaluator,            SAVED_NETWORK_EVALUATOR_PRIORITY);    if (hs2Enabled) {        mNetworkSelector.registerNetworkEvaluator(passpointNetworkEvaluator,                PASSPOINT_NETWORK_EVALUATOR_PRIORITY);    }    mNetworkSelector.registerNetworkEvaluator(scoredNetworkEvaluator,            SCORED_NETWORK_EVALUATOR_PRIORITY);}

注册方法就是初始化一个NetworkEvaluator数组，大小为6，即优先级从高到低0-5。
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiNetworkSelector.java

public boolean registerNetworkEvaluator(NetworkEvaluator evaluator, int priority) {    if (priority < 0 || priority >= EVALUATOR_MIN_PRIORITY) {        localLog("Invalid network evaluator priority: " + priority);        return false;    }    if (mEvaluators[priority] != null) {        localLog("Priority " + priority + " is already registered by "                + mEvaluators[priority].getName());        return false;    }    mEvaluators[priority] = evaluator;    return true;}private final NetworkEvaluator[] mEvaluators = new NetworkEvaluator[MAX_NUM_EVALUATORS];public static final int MAX_NUM_EVALUATORS = EVALUATOR_MIN_PRIORITY;/** * WiFi Network Selector supports various types of networks. Each type can * have its evaluator to choose the best WiFi network for the device to connect * to. When registering a WiFi network evaluator with the WiFi Network Selector, * the priority of the network must be specified, and it must be a value between * 0 and (EVALUATOR_MIN_PIRORITY - 1) with 0 being the highest priority. Wifi * Network Selector iterates through the registered scorers from the highest priority * to the lowest till a network is selected. */public static final int EVALUATOR_MIN_PRIORITY = 6;

2、WifiConnectivityManager的网络评估

处理扫描结果
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiConnectivityManager.java

private boolean handleScanResults(List<ScanDetail> scanDetails, String listenerName) {    // Check if any blacklisted BSSIDs can be freed.    refreshBssidBlacklist();    if (mStateMachine.isSupplicantTransientState()) {        localLog(listenerName                + " onResults: No network selection because supplicantTransientState is "                + mStateMachine.isSupplicantTransientState());        return false;    }    localLog(listenerName + " onResults: start network selection");    WifiConfiguration candidate =            mNetworkSelector.selectNetwork(scanDetails, buildBssidBlacklist(), mWifiInfo,            mStateMachine.isConnected(), mStateMachine.isDisconnected(),            mUntrustedConnectionAllowed);    mWifiLastResortWatchdog.updateAvailableNetworks(            mNetworkSelector.getConnectableScanDetails());    mWifiMetrics.countScanResults(scanDetails);    if (candidate != null) {        localLog(listenerName + ":  WNS candidate-" + candidate.SSID);        connectToNetwork(candidate);        return true;    } else {        if (mWifiState == WIFI_STATE_DISCONNECTED) {            mOpenNetworkNotifier.handleScanResults(                    mNetworkSelector.getFilteredScanDetailsForOpenUnsavedNetworks());            if (mCarrierNetworkConfig.isCarrierEncryptionInfoAvailable()) {                mCarrierNetworkNotifier.handleScanResults(                        mNetworkSelector.getFilteredScanDetailsForCarrierUnsavedNetworks(                                mCarrierNetworkConfig));            }        }        return false;    }}

如注释所说：处理周期性，单次和Pno ScanListener的“ onResult”回调。执行潜在网络候选者的选择，启动与该网络的连接尝试。

然后看candidate是如何生成的：
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiNetworkSelector.java

public WifiConfiguration selectNetwork(List<ScanDetail> scanDetails,        HashSet<String> bssidBlacklist, WifiInfo wifiInfo,        boolean connected, boolean disconnected, boolean untrustedNetworkAllowed) {    mFilteredNetworks.clear();    mConnectableNetworks.clear();    if (scanDetails.size() == 0) {        localLog("Empty connectivity scan result");        return null;    }    WifiConfiguration currentNetwork =            mWifiConfigManager.getConfiguredNetwork(wifiInfo.getNetworkId());    // Always get the current BSSID from WifiInfo in case that firmware initiated    // roaming happened.    String currentBssid = wifiInfo.getBSSID();    // Shall we start network selection at all?    if (!isNetworkSelectionNeeded(scanDetails, wifiInfo, connected, disconnected)) {        return null;    }    // Update the registered network evaluators.    for (NetworkEvaluator registeredEvaluator : mEvaluators) {        if (registeredEvaluator != null) {            registeredEvaluator.update(scanDetails);        }    }    // Filter out unwanted networks.    mFilteredNetworks = filterScanResults(scanDetails, bssidBlacklist,            connected, currentBssid);    if (mFilteredNetworks.size() == 0) {        return null;    }    // Go through the registered network evaluators from the highest priority    // one to the lowest till a network is selected.    WifiConfiguration selectedNetwork = null;    for (NetworkEvaluator registeredEvaluator : mEvaluators) {        if (registeredEvaluator != null) {            localLog("About to run " + registeredEvaluator.getName() + " :");            selectedNetwork = registeredEvaluator.evaluateNetworks(                    new ArrayList<>(mFilteredNetworks), currentNetwork, currentBssid, connected,                    untrustedNetworkAllowed, mConnectableNetworks);            if (selectedNetwork != null) {                localLog(registeredEvaluator.getName() + " selects "                        + WifiNetworkSelector.toNetworkString(selectedNetwork) + " : "                        + selectedNetwork.getNetworkSelectionStatus().getCandidate().BSSID);                break;            }        }    }    if (selectedNetwork != null) {        selectedNetwork = overrideCandidateWithUserConnectChoice(selectedNetwork);        mLastNetworkSelectionTimeStamp = mClock.getElapsedSinceBootMillis();    }    return selectedNetwork;}

2.1、判断是否需要网络选择

private boolean isNetworkSelectionNeeded(List<ScanDetail> scanDetails, WifiInfo wifiInfo,                    boolean connected, boolean disconnected) {    if (scanDetails.size() == 0) {        localLog("Empty connectivity scan results. Skip network selection.");        return false;    }    if (connected) {        // Is roaming allowed?        if (!mEnableAutoJoinWhenAssociated) {            localLog("Switching networks in connected state is not allowed."                    + " Skip network selection.");            return false;        }        // Has it been at least the minimum interval since last network selection?        if (mLastNetworkSelectionTimeStamp != INVALID_TIME_STAMP) {            long gap = mClock.getElapsedSinceBootMillis()                        - mLastNetworkSelectionTimeStamp;            if (gap < MINIMUM_NETWORK_SELECTION_INTERVAL_MS) {                localLog("Too short since last network selection: " + gap + " ms."                        + " Skip network selection.");                return false;            }        }        if (isCurrentNetworkSufficient(wifiInfo, scanDetails)) {            localLog("Current connected network already sufficient. Skip network selection.");            return false;        } else {            localLog("Current connected network is not sufficient.");            return true;        }    } else if (disconnected) {        return true;    } else {        // No network selection if WifiStateMachine is in a state other than        // CONNECTED or DISCONNECTED.        localLog("WifiStateMachine is in neither CONNECTED nor DISCONNECTED state."                + " Skip network selection.");        return false;    }}

2.2、SavedNetworkEvaluator的筛选

根据扫描结果评估所有网络，并返回选择用于连接的网络的WifiConfiguration
frameworks/opt/net/wifi/service/java/com/android/server/wifi/SavedNetworkEvaluator.java

/** * Evaluate all the networks from the scan results and return * the WifiConfiguration of the network chosen for connection. * * @return configuration of the chosen network; *         null if no network in this category is available. */public WifiConfiguration evaluateNetworks(List<ScanDetail> scanDetails,                WifiConfiguration currentNetwork, String currentBssid, boolean connected,                boolean untrustedNetworkAllowed,                List<Pair<ScanDetail, WifiConfiguration>> connectableNetworks) {    int highestScore = Integer.MIN_VALUE;    ScanResult scanResultCandidate = null;    WifiConfiguration candidate = null;    StringBuffer scoreHistory = new StringBuffer();    for (ScanDetail scanDetail : scanDetails) {        ScanResult scanResult = scanDetail.getScanResult();        // One ScanResult can be associated with more than one networks, hence we calculate all        // the scores and use the highest one as the ScanResult's score.        WifiConfiguration network =                mWifiConfigManager.getConfiguredNetworkForScanDetailAndCache(scanDetail);        if (network == null) {            continue;        }        /**         * Ignore Passpoint and Ephemeral networks. They are configured networks,         * but without being persisted to the storage. They are evaluated by         * {@link PasspointNetworkEvaluator} and {@link ScoredNetworkEvaluator}         * respectively.         */        if (network.isPasspoint() || network.isEphemeral()) {            continue;        }        WifiConfiguration.NetworkSelectionStatus status =                network.getNetworkSelectionStatus();        status.setSeenInLastQualifiedNetworkSelection(true);        if (!status.isNetworkEnabled()) {            continue;        } else if (network.BSSID != null &&  !network.BSSID.equals("any")                && !network.BSSID.equals(scanResult.BSSID)) {            // App has specified the only BSSID to connect for this            // configuration. So only the matching ScanResult can be a candidate.            localLog("Network " + WifiNetworkSelector.toNetworkString(network)                    + " has specified BSSID " + network.BSSID + ". Skip "                    + scanResult.BSSID);            continue;        } else if (TelephonyUtil.isSimConfig(network)                && !mWifiConfigManager.isSimPresent()) {            // Don't select if security type is EAP SIM/AKA/AKA' when SIM is not present.            continue;        }        int score = calculateBssidScore(scanResult, network, currentNetwork, currentBssid,                scoreHistory);        // Set candidate ScanResult for all saved networks to ensure that users can        // override network selection. See WifiNetworkSelector#setUserConnectChoice.        // TODO(b/36067705): consider alternative designs to push filtering/selecting of        // user connect choice networks to RecommendedNetworkEvaluator.        if (score > status.getCandidateScore() || (score == status.getCandidateScore()                && status.getCandidate() != null                && scanResult.level > status.getCandidate().level)) {            mWifiConfigManager.setNetworkCandidateScanResult(                    network.networkId, scanResult, score);        }        // If the network is marked to use external scores, or is an open network with        // curate saved open networks enabled, do not consider it for network selection.        if (network.useExternalScores) {            localLog("Network " + WifiNetworkSelector.toNetworkString(network)                    + " has external score.");            continue;        }        if (connectableNetworks != null) {            connectableNetworks.add(Pair.create(scanDetail,                    mWifiConfigManager.getConfiguredNetwork(network.networkId)));        }        if (score > highestScore                || (score == highestScore                && scanResultCandidate != null                && scanResult.level > scanResultCandidate.level)) {            highestScore = score;            scanResultCandidate = scanResult;            mWifiConfigManager.setNetworkCandidateScanResult(                    network.networkId, scanResultCandidate, highestScore);            // Reload the network config with the updated info.            candidate = mWifiConfigManager.getConfiguredNetwork(network.networkId);        }    }    if (scoreHistory.length() > 0) {        localLog("\n" + scoreHistory.toString());    }    if (scanResultCandidate == null) {        localLog("did not see any good candidates.");    }    return candidate;}

忽略Passpoint和临时网络。

/** * Ignore Passpoint and Ephemeral networks. They are configured networks, * but without being persisted to the storage. They are evaluated by * {@link PasspointNetworkEvaluator} and {@link ScoredNetworkEvaluator} * respectively. */if (network.isPasspoint() || network.isEphemeral()) {    continue;}

判断当前网络是否允许加入网络选择，如果不允许，则过滤掉

if (!status.isNetworkEnabled()) {    continue;} else if (network.BSSID != null &&  !network.BSSID.equals("any")        && !network.BSSID.equals(scanResult.BSSID)) {    // App has specified the only BSSID to connect for this    // configuration. So only the matching ScanResult can be a candidate.    localLog("Network " + WifiNetworkSelector.toNetworkString(network)            + " has specified BSSID " + network.BSSID + ". Skip "            + scanResult.BSSID);    continue;

如果该网络被标记为使用外部得分，或者该网络是启用了保存已保存的开放网络的开放网络，则不要将其视为网络选择

if (network.useExternalScores) {    localLog("Network " + WifiNetworkSelector.toNetworkString(network)            + " has external score.");    continue;}

2.3、评分机制

frameworks/opt/net/wifi/service/java/com/android/server/wifi/SavedNetworkEvaluator.java

private int calculateBssidScore(ScanResult scanResult, WifiConfiguration network,                    WifiConfiguration currentNetwork, String currentBssid,                    StringBuffer sbuf) {    int score = 0;    boolean is5GHz = scanResult.is5GHz();    sbuf.append("[ ").append(scanResult.SSID).append(" ").append(scanResult.BSSID)            .append(" RSSI:").append(scanResult.level).append(" ] ");    // Calculate the RSSI score.    int rssiSaturationThreshold = mScoringParams.getGoodRssi(scanResult.frequency);    int rssi = scanResult.level < rssiSaturationThreshold ? scanResult.level            : rssiSaturationThreshold;    score += (rssi + mRssiScoreOffset) * mRssiScoreSlope;    sbuf.append(" RSSI score: ").append(score).append(",");    // 5GHz band bonus.    if (is5GHz) {        score += mBand5GHzAward;        sbuf.append(" 5GHz bonus: ").append(mBand5GHzAward).append(",");    }    // Last user selection award.    int lastUserSelectedNetworkId = mWifiConfigManager.getLastSelectedNetwork();    if (lastUserSelectedNetworkId != WifiConfiguration.INVALID_NETWORK_ID            && lastUserSelectedNetworkId == network.networkId) {        long timeDifference = mClock.getElapsedSinceBootMillis()                - mWifiConfigManager.getLastSelectedTimeStamp();        if (timeDifference > 0) {            int bonus = mLastSelectionAward - (int) (timeDifference / 1000 / 60);            score += bonus > 0 ? bonus : 0;            sbuf.append(" User selection ").append(timeDifference / 1000 / 60)                    .append(" minutes ago, bonus: ").append(bonus).append(",");        }    }    // Same network award.    if (currentNetwork != null            && (network.networkId == currentNetwork.networkId            //TODO(b/36788683): re-enable linked configuration check            /* || network.isLinked(currentNetwork) */)) {        score += mSameNetworkAward;        sbuf.append(" Same network bonus: ").append(mSameNetworkAward).append(",");        // When firmware roaming is supported, equivalent BSSIDs (the ones under the        // same network as the currently connected one) get the same BSSID award.        if (mConnectivityHelper.isFirmwareRoamingSupported()                && currentBssid != null && !currentBssid.equals(scanResult.BSSID)) {            score += mSameBssidAward;            sbuf.append(" Equivalent BSSID bonus: ").append(mSameBssidAward).append(",");        }    }    // Same BSSID award.    if (currentBssid != null && currentBssid.equals(scanResult.BSSID)) {        score += mSameBssidAward;        sbuf.append(" Same BSSID bonus: ").append(mSameBssidAward).append(",");    }    // Security award.    if (!WifiConfigurationUtil.isConfigForOpenNetwork(network)) {        score += mSecurityAward;        sbuf.append(" Secure network bonus: ").append(mSecurityAward).append(",");    }    sbuf.append(" ## Total score: ").append(score).append("\n");    return score;}

2.3.1、RSSI

int rssiSaturationThreshold = mScoringParams.getGoodRssi(scanResult.frequency);int rssi = scanResult.level < rssiSaturationThreshold ? scanResult.level        : rssiSaturationThreshold;score += (rssi + mRssiScoreOffset) * mRssiScoreSlope;

2.3.2、5G

如果频率是5G，会加分

if (is5GHz) {    score += mBand5GHzAward;    sbuf.append(" 5GHz bonus: ").append(mBand5GHzAward).append(",");}

2.3.3、Last user selection award

最后一个使用的网络会加分

// Last user selection award.int lastUserSelectedNetworkId = mWifiConfigManager.getLastSelectedNetwork();if (lastUserSelectedNetworkId != WifiConfiguration.INVALID_NETWORK_ID        && lastUserSelectedNetworkId == network.networkId) {    long timeDifference = mClock.getElapsedSinceBootMillis()            - mWifiConfigManager.getLastSelectedTimeStamp();    if (timeDifference > 0) {        int bonus = mLastSelectionAward - (int) (timeDifference / 1000 / 60);        score += bonus > 0 ? bonus : 0;        sbuf.append(" User selection ").append(timeDifference / 1000 / 60)                .append(" minutes ago, bonus: ").append(bonus).append(",");    }}

2.3.4、Same network award

相同的networkId会加分，相同的networkId且支持漫游也会加分

// Same network award.if (currentNetwork != null        && (network.networkId == currentNetwork.networkId        //TODO(b/36788683): re-enable linked configuration check        /* || network.isLinked(currentNetwork) */)) {    score += mSameNetworkAward;    sbuf.append(" Same network bonus: ").append(mSameNetworkAward).append(",");    // When firmware roaming is supported, equivalent BSSIDs (the ones under the    // same network as the currently connected one) get the same BSSID award.    if (mConnectivityHelper.isFirmwareRoamingSupported()            && currentBssid != null && !currentBssid.equals(scanResult.BSSID)) {        score += mSameBssidAward;        sbuf.append(" Equivalent BSSID bonus: ").append(mSameBssidAward).append(",");    }}

2.3.5、Same BSSID award

相同的BSSID会加分

// Same BSSID award.if (currentBssid != null && currentBssid.equals(scanResult.BSSID)) {    score += mSameBssidAward;    sbuf.append(" Same BSSID bonus: ").append(mSameBssidAward).append(",");}

2.3.6、Security award

不是开放的网络会加分

// Security award.if (!WifiConfigurationUtil.isConfigForOpenNetwork(network)) {    score += mSecurityAward;    sbuf.append(" Secure network bonus: ").append(mSecurityAward).append(",");}

3、总结

SavedNetworkEvaluator评分几大要素：
rssi
5G
Last user selection award
Same network award 支持漫游
Same BSSID award
Security award

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