Wifi: enhance pre-scan check and simplify network selection sufficiency check.

1) Skip single scan scheduled by periodic scan alarm if current RSSI ssufficient
2) Simplify pre-network-selection sufficiency check. Skip selection only if
 +) Current network has internet access, active traffic and sufficient RSSI.
 +) or current network is in OSU process.
3) Move to rely on network selection scorer to stick with user selected network.

Bug: 141714375
Test: unit test with atest com.android.server.wifi
Test: manual test with phone.
Change-Id: Id232b59a546271d7f0798bc6a85ca6ccd65621e9

5 files changed, 73 insertions, 82 deletions

diff --git a/service/java/com/android/server/wifi/ScoringParams.java b/service/java/com/android/server/wifi/ScoringParams.java
index 94efde198..216848771 100644
--- a/service/java/com/android/server/wifi/ScoringParams.java
+++ b/service/java/com/android/server/wifi/ScoringParams.java
@@ -48,6 +48,8 @@ public class ScoringParams {
     private static final int SUFFICIENT = 2;
     private static final int GOOD = 3;
 
+    private static final int ACTIVE_TRAFFIC = 1;
+    private static final int HIGH_TRAFFIC = 2;
     /**
      * Parameter values are stored in a separate container so that a new collection of values can
      * be checked for consistency before activating them.
@@ -284,7 +286,10 @@ public class ScoringParams {
                 R.integer.config_wifiFrameworkSecureNetworkBonus);
         mVal.lastSelectionBonus = context.getResources().getInteger(
                 R.integer.config_wifiFrameworkLastSelectionBonus);
-
+        mVal.pps[ACTIVE_TRAFFIC] = context.getResources().getInteger(
+                R.integer.config_wifiFrameworkMinPacketPerSecondActiveTraffic);
+        mVal.pps[HIGH_TRAFFIC] = context.getResources().getInteger(
+                R.integer.config_wifiFrameworkMinPacketPerSecondHighTraffic);
         try {
             mVal.validate();
         } catch (IllegalArgumentException e) {
@@ -409,7 +414,15 @@ public class ScoringParams {
      */
     public int getYippeeSkippyPacketsPerSecond() {
         loadResources(mContext);
-        return mVal.pps[2];
+        return mVal.pps[HIGH_TRAFFIC];
+    }
+
+    /**
+     * Returns a packet rate that should be considered acceptable to skip scan or network selection
+     */
+    public int getActiveTrafficPacketsPerSecond() {
+        loadResources(mContext);
+        return mVal.pps[ACTIVE_TRAFFIC];
     }
 
     /**
diff --git a/service/java/com/android/server/wifi/WifiConnectivityManager.java b/service/java/com/android/server/wifi/WifiConnectivityManager.java
index 5c67fa591..53261d36e 100644
--- a/service/java/com/android/server/wifi/WifiConnectivityManager.java
+++ b/service/java/com/android/server/wifi/WifiConnectivityManager.java
@@ -268,8 +268,8 @@ public class WifiConnectivityManager {
     /**
      * Set whether bluetooth is in the connected state
      */
-    public void setBluetoothConnected(boolean isBlueToothConnected) {
-        mNetworkSelector.setBluetoothConnected(isBlueToothConnected);
+    public void setBluetoothConnected(boolean isBluetoothConnected) {
+        mNetworkSelector.setBluetoothConnected(isBluetoothConnected);
     }
 
     // All single scan results listener.
@@ -574,7 +574,6 @@ public class WifiConnectivityManager {
         mClock = clock;
         mScoringParams = scoringParams;
         mConnectionAttemptTimeStamps = new LinkedList<>();
-
         mPnoScanIntervalMs = MOVING_PNO_SCAN_INTERVAL_MS;
 
         // Listen to WifiConfigManager network update events
@@ -815,15 +814,12 @@ public class WifiConnectivityManager {
 
         boolean isScanNeeded = true;
         boolean isFullBandScan = true;
-        boolean isTrafficOverThreshold = mWifiInfo.getTxSuccessRate()
-                > mContext.getResources().getInteger(
-                        R.integer.config_wifi_framework_max_tx_rate_for_full_scan)
-                || mWifiInfo.getRxSuccessRate()
-                > mContext.getResources().getInteger(
-                        R.integer.config_wifi_framework_max_rx_rate_for_full_scan);
-
-        // If the WiFi traffic is heavy, only partial scan is proposed.
-        if (mWifiState == WIFI_STATE_CONNECTED && isTrafficOverThreshold) {
+
+        // If current network link quality is sufficient or has active stream,
+        // skip scan (with firmware roaming) or do partial scan only (without firmware roaming).
+        if (mWifiState == WIFI_STATE_CONNECTED
+                && (mNetworkSelector.hasSufficientLinkQuality(mWifiInfo, mScoringParams)
+                || mNetworkSelector.hasActiveStream(mWifiInfo, mScoringParams))) {
             // If only partial scan is proposed and firmware roaming control is supported,
             // we will not issue any scan because firmware roaming will take care of
             // intra-SSID roam.
@@ -831,7 +827,7 @@ public class WifiConnectivityManager {
                 localLog("No partial scan because firmware roaming is supported.");
                 isScanNeeded = false;
             } else {
-                localLog("No full band scan due to ongoing traffic");
+                localLog("No full band scan because current network is sufficient");
                 isFullBandScan = false;
             }
         }
diff --git a/service/java/com/android/server/wifi/WifiNetworkSelector.java b/service/java/com/android/server/wifi/WifiNetworkSelector.java
index 426a81424..fec8e0dde 100644
--- a/service/java/com/android/server/wifi/WifiNetworkSelector.java
+++ b/service/java/com/android/server/wifi/WifiNetworkSelector.java
@@ -214,7 +214,34 @@ public class WifiNetworkSelector {
         mLocalLog.log(log);
     }
 
-    private boolean isCurrentNetworkSufficient(WifiInfo wifiInfo, List<ScanDetail> scanDetails) {
+    /**
+     * Check if current network has sufficient RSSI
+     * @param wifiInfo info of currently connected network
+     * @param scoringParams scoring parameter set including RSSI sufficiency check threshold
+     * @return true if current link quality is sufficient, false otherwise.
+     */
+    public static boolean hasSufficientLinkQuality(WifiInfo wifiInfo, ScoringParams scoringParams) {
+        int currentRssi = wifiInfo.getRssi();
+        return  currentRssi >= scoringParams.getSufficientRssi(wifiInfo.getFrequency());
+    }
+
+    /**
+     * Check if current network has active Tx or Rx traffic
+     * @param wifiInfo info of currently connected network
+     * @param scoringParams scoring parameter set including active traffic check threshold
+     * @return true if it has active Tx or Rx traffic, false otherwise.
+     */
+    public static boolean hasActiveStream(WifiInfo wifiInfo, ScoringParams scoringParams) {
+        return (wifiInfo.getTxSuccessRate() > scoringParams.getActiveTrafficPacketsPerSecond())
+                || (wifiInfo.getRxSuccessRate() > scoringParams.getActiveTrafficPacketsPerSecond());
+    }
+
+    /**
+     * Check if one of following conditions is met to avoid a new network selection
+     * 1) current network is in OSU process
+     * 2) current network has internet access, sufficient link quality and active traffic
+     */
+    private boolean isCurrentNetworkSufficient(WifiInfo wifiInfo) {
         // Currently connected?
         if (wifiInfo.getSupplicantState() != SupplicantState.COMPLETED) {
             localLog("No current connected network.");
@@ -224,19 +251,6 @@ public class WifiNetworkSelector {
                     + " , ID: " + wifiInfo.getNetworkId());
         }
 
-        final int stayOnNetworkMinimumTxRate = mContext.getResources().getInteger(
-                R.integer.config_wifi_framework_min_tx_rate_for_staying_on_network);
-        final int stayOnNetworkMinimumRxRate = mContext.getResources().getInteger(
-                R.integer.config_wifi_framework_min_rx_rate_for_staying_on_network);
-        int currentRssi = wifiInfo.getRssi();
-        boolean hasQualifiedRssi = currentRssi
-                > mScoringParams.getSufficientRssi(wifiInfo.getFrequency());
-        boolean hasActiveStream = (wifiInfo.getTxSuccessRate() > stayOnNetworkMinimumTxRate)
-                || (wifiInfo.getRxSuccessRate() > stayOnNetworkMinimumRxRate);
-        if (hasQualifiedRssi && hasActiveStream) {
-            localLog("Stay on current network because of good RSSI and ongoing traffic");
-            return true;
-        }
         WifiConfiguration network =
                 mWifiConfigManager.getConfiguredNetwork(wifiInfo.getNetworkId());
 
@@ -245,58 +259,25 @@ public class WifiNetworkSelector {
             return false;
         }
 
-        if (mWifiConfigManager.getLastSelectedNetwork() == network.networkId
-                && (mClock.getElapsedSinceBootMillis()
-                    - mWifiConfigManager.getLastSelectedTimeStamp())
-                <= LAST_USER_SELECTION_SUFFICIENT_MS) {
-            localLog("Current network is recently user-selected.");
-            return true;
-        }
-
-        // OSU (Online Sign Up) network for Passpoint Release 2 is sufficient network.
+        // Set OSU (Online Sign Up) network for Passpoint Release 2 to sufficient
+        // so that network select selection is skipped and OSU process can complete.
         if (network.osu) {
             return true;
         }
 
-        // Ephemeral network is not qualified.
-        if (wifiInfo.isEphemeral()) {
-            localLog("Current network is an ephemeral one.");
-            return false;
-        }
-
-        if (wifiInfo.is24GHz()) {
-            // 2.4GHz networks is not qualified whenever 5GHz is available
-            if (is5GHzNetworkAvailable(scanDetails)) {
-                localLog("Current network is 2.4GHz. 5GHz networks available.");
-                return false;
-            }
-        }
-        if (!hasQualifiedRssi) {
-            localLog("Current network RSSI[" + currentRssi + "]-acceptable but not qualified.");
-            return false;
-        }
-
-        // Open network is not qualified.
-        if (WifiConfigurationUtil.isConfigForOpenNetwork(network)) {
-            localLog("Current network is a open one.");
-            return false;
-        }
-
-        // Network with no internet access reports is not qualified.
+        // Network with no internet access reports is not sufficient
         if (network.numNoInternetAccessReports > 0 && !network.noInternetAccessExpected) {
             localLog("Current network has [" + network.numNoInternetAccessReports
                     + "] no-internet access reports.");
             return false;
         }
-        return true;
-    }
 
-    // Determine whether there are any 5GHz networks in the scan result
-    private boolean is5GHzNetworkAvailable(List<ScanDetail> scanDetails) {
-        for (ScanDetail detail : scanDetails) {
-            ScanResult result = detail.getScanResult();
-            if (result.is5GHz()) return true;
+        if ((hasSufficientLinkQuality(wifiInfo, mScoringParams))
+                && hasActiveStream(wifiInfo, mScoringParams)) {
+            localLog("Stay on current network due to sufficient link quality and ongoing traffic");
+            return true;
         }
+
         return false;
     }
 
@@ -326,8 +307,10 @@ public class WifiNetworkSelector {
                     return false;
                 }
             }
-
-            if (isCurrentNetworkSufficient(wifiInfo, scanDetails)) {
+            // Please note other scans (e.g., location scan or app scan) may also trigger network
+            // selection and these scans may or may not run sufficiency check.
+            // So it is better to run sufficiency check here before network selection.
+            if (isCurrentNetworkSufficient(wifiInfo)) {
                 localLog("Current connected network already sufficient. Skip network selection.");
                 return false;
             } else {
@@ -828,6 +811,7 @@ public class WifiNetworkSelector {
         // Get a fresh copy of WifiConfiguration reflecting any scan result updates
         WifiConfiguration selectedNetwork =
                 mWifiConfigManager.getConfiguredNetwork(selectedNetworkId);
+        // TODO (b/136675430): the legacyOverrideWanted check seems unnecessary
         if (selectedNetwork != null && legacyOverrideWanted) {
             selectedNetwork = overrideCandidateWithUserConnectChoice(selectedNetwork);
             mLastNetworkSelectionTimeStamp = mClock.getElapsedSinceBootMillis();
diff --git a/service/res/values/config.xml b/service/res/values/config.xml
index ec8da0e50..29cd63456 100644
--- a/service/res/values/config.xml
+++ b/service/res/values/config.xml
@@ -98,12 +98,12 @@
          boundaries. -->
     <integer translatable="false" name="config_wifiFrameworkLastSelectionBonus">1999</integer>
 
-    <!-- Integers specifying the max packet Tx/Rx rates for full scan -->
-    <integer translatable="false" name="config_wifi_framework_max_tx_rate_for_full_scan">8</integer>
-    <integer translatable="false" name="config_wifi_framework_max_rx_rate_for_full_scan">16</integer>
-    <!-- Integers specifying the min packet Tx/Rx rates in packets per second for staying on the same network -->
-    <integer translatable="false" name="config_wifi_framework_min_tx_rate_for_staying_on_network">16</integer>
-    <integer translatable="false" name="config_wifi_framework_min_rx_rate_for_staying_on_network">16</integer>
+    <!-- Integer specifying the min packet Tx/Rx rates in packets per second to be considered
+         active traffic so that network selection and scan could be skipped-->
+    <integer translatable="false" name="config_wifiFrameworkMinPacketPerSecondActiveTraffic">16</integer>
+    <!-- Integer specifying the min packet Tx/Rx rates in packets per second to be considered
+         high traffic so that the device should stay on WiFi even if RSSI is very low -->
+    <integer translatable="false" name="config_wifiFrameworkMinPacketPerSecondHighTraffic">100</integer>
     <!-- Integer parameters of the wifi to cellular handover feature
          wifi should not stick to bad networks -->
     <!-- Integer threshold for low network score, should be somewhat less than the entry threshhold -->
diff --git a/service/res/values/overlayable.xml b/service/res/values/overlayable.xml
index e7b82ce64..a60e04d19 100644
--- a/service/res/values/overlayable.xml
+++ b/service/res/values/overlayable.xml
@@ -40,10 +40,8 @@
           <item type="integer" name="config_wifiFrameworkCurrentNetworkBonus" />
           <item type="integer" name="config_wifiFrameworkSecureNetworkBonus" />
           <item type="integer" name="config_wifiFrameworkLastSelectionBonus" />
-          <item type="integer" name="config_wifi_framework_max_tx_rate_for_full_scan" />
-          <item type="integer" name="config_wifi_framework_max_rx_rate_for_full_scan" />
-          <item type="integer" name="config_wifi_framework_min_tx_rate_for_staying_on_network" />
-          <item type="integer" name="config_wifi_framework_min_rx_rate_for_staying_on_network" />
+          <item type="integer" name="config_wifiFrameworkMinPacketPerSecondActiveTraffic" />
+          <item type="integer" name="config_wifiFrameworkMinPacketPerSecondHighTraffic" />
           <item type="integer" name="config_wifi_framework_wifi_score_bad_rssi_threshold_5GHz" />
           <item type="integer" name="config_wifi_framework_wifi_score_entry_rssi_threshold_5GHz" />
           <item type="integer" name="config_wifi_framework_wifi_score_low_rssi_threshold_5GHz" />