WifiConnectivityManager: enforce minimum single scan interval

am: c2963eb076

* commit 'c2963eb07660a06592c60224279685166390217d':
  WifiConnectivityManager: enforce minimum single scan interval

Change-Id: I8e95d793334a7d4df96d3e1c61d05b12e226e5e8

2 files changed, 95 insertions, 8 deletions

diff --git a/service/java/com/android/server/wifi/WifiConnectivityManager.java b/service/java/com/android/server/wifi/WifiConnectivityManager.java
index d99b65f8f..3071fbf12 100644
--- a/service/java/com/android/server/wifi/WifiConnectivityManager.java
+++ b/service/java/com/android/server/wifi/WifiConnectivityManager.java
@@ -65,6 +65,7 @@ public class WifiConnectivityManager {
             "WifiConnectivityManager Restart Scan";
 
     private static final String TAG = "WifiConnectivityManager";
+    private static final long INVALID_TIME_STAMP = Long.MIN_VALUE;
     // Periodic scan interval in milli-seconds. This is the scan
     // performed when screen is on.
     @VisibleForTesting
@@ -142,6 +143,7 @@ public class WifiConnectivityManager {
     private int mTotalConnectivityAttemptsRateLimited = 0;
     private String mLastConnectionAttemptBssid = null;
     private int mPeriodicSingleScanInterval = PERIODIC_SCAN_INTERVAL_MS;
+    private long mLastPeriodicSingleScanTimeStamp = INVALID_TIME_STAMP;
 
     // PNO settings
     private int mMin5GHzRssi;
@@ -662,6 +664,18 @@ public class WifiConnectivityManager {
 
     // Start a single scan and set up the interval for next single scan.
     private void startPeriodicSingleScan() {
+        long currentTimeStamp = mClock.elapsedRealtime();
+
+        if (mLastPeriodicSingleScanTimeStamp != INVALID_TIME_STAMP) {
+            long msSinceLastScan = currentTimeStamp - mLastPeriodicSingleScanTimeStamp;
+            if (msSinceLastScan < PERIODIC_SCAN_INTERVAL_MS) {
+                localLog("Last periodic single scan started " + msSinceLastScan
+                        + "ms ago, defer this new scan request.");
+                schedulePeriodicScanTimer(PERIODIC_SCAN_INTERVAL_MS - (int) msSinceLastScan);
+                return;
+            }
+        }
+
         boolean isFullBandScan = true;
 
         // If the WiFi traffic is heavy, only partial scan is initiated.
@@ -676,6 +690,7 @@ public class WifiConnectivityManager {
             isFullBandScan = false;
         }
 
+        mLastPeriodicSingleScanTimeStamp = currentTimeStamp;
         startSingleScan(false, isFullBandScan);
         schedulePeriodicScanTimer(mPeriodicSingleScanInterval);
 
diff --git a/tests/wifitests/src/com/android/server/wifi/WifiConnectivityManagerTest.java b/tests/wifitests/src/com/android/server/wifi/WifiConnectivityManagerTest.java
index a2379330c..aa48cadf5 100644
--- a/tests/wifitests/src/com/android/server/wifi/WifiConnectivityManagerTest.java
+++ b/tests/wifitests/src/com/android/server/wifi/WifiConnectivityManagerTest.java
@@ -533,11 +533,17 @@ public class WifiConnectivityManagerTest {
      */
     @Test
     public void checkPeriodicScanIntervalWhenDisconnected() {
-        when(mClock.elapsedRealtime()).thenReturn(CURRENT_SYSTEM_TIME_MS);
+        long currentTimeStamp = CURRENT_SYSTEM_TIME_MS;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
 
         // Set screen to ON
         mWifiConnectivityManager.handleScreenStateChanged(true);
 
+        // Wait for MAX_PERIODIC_SCAN_INTERVAL_MS so that any impact triggered
+        // by screen state change can settle
+        currentTimeStamp += WifiConnectivityManager.MAX_PERIODIC_SCAN_INTERVAL_MS;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
         // Set WiFi to disconnected state to trigger periodic scan
         mWifiConnectivityManager.handleConnectionStateChanged(
                 WifiConnectivityManager.WIFI_STATE_DISCONNECTED);
@@ -545,9 +551,12 @@ public class WifiConnectivityManagerTest {
         // Get the first periodic scan interval
         long firstIntervalMs = mAlarmManager
                     .getTriggerTimeMillis(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG)
-                    - CURRENT_SYSTEM_TIME_MS;
+                    - currentTimeStamp;
         assertEquals(firstIntervalMs, WifiConnectivityManager.PERIODIC_SCAN_INTERVAL_MS);
 
+        currentTimeStamp += firstIntervalMs;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
         // Now fire the first periodic scan alarm timer
         mAlarmManager.dispatch(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG);
         mLooper.dispatchAll();
@@ -555,11 +564,14 @@ public class WifiConnectivityManagerTest {
         // Get the second periodic scan interval
         long secondIntervalMs = mAlarmManager
                     .getTriggerTimeMillis(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG)
-                    - CURRENT_SYSTEM_TIME_MS;
+                    - currentTimeStamp;
 
         // Verify the intervals are exponential back off
         assertEquals(firstIntervalMs * 2, secondIntervalMs);
 
+        currentTimeStamp += secondIntervalMs;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
         // Make sure we eventually stay at the maximum scan interval.
         long intervalMs = 0;
         for (int i = 0; i < 5; i++) {
@@ -567,7 +579,9 @@ public class WifiConnectivityManagerTest {
             mLooper.dispatchAll();
             intervalMs = mAlarmManager
                     .getTriggerTimeMillis(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG)
-                    - CURRENT_SYSTEM_TIME_MS;
+                    - currentTimeStamp;
+            currentTimeStamp += intervalMs;
+            when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
         }
 
         assertEquals(intervalMs, WifiConnectivityManager.MAX_PERIODIC_SCAN_INTERVAL_MS);
@@ -582,11 +596,17 @@ public class WifiConnectivityManagerTest {
      */
     @Test
     public void checkPeriodicScanIntervalWhenConnected() {
-        when(mClock.elapsedRealtime()).thenReturn(CURRENT_SYSTEM_TIME_MS);
+        long currentTimeStamp = CURRENT_SYSTEM_TIME_MS;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
 
         // Set screen to ON
         mWifiConnectivityManager.handleScreenStateChanged(true);
 
+        // Wait for MAX_PERIODIC_SCAN_INTERVAL_MS so that any impact triggered
+        // by screen state change can settle
+        currentTimeStamp += WifiConnectivityManager.MAX_PERIODIC_SCAN_INTERVAL_MS;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
         // Set WiFi to connected state to trigger periodic scan
         mWifiConnectivityManager.handleConnectionStateChanged(
                 WifiConnectivityManager.WIFI_STATE_CONNECTED);
@@ -594,9 +614,12 @@ public class WifiConnectivityManagerTest {
         // Get the first periodic scan interval
         long firstIntervalMs = mAlarmManager
                     .getTriggerTimeMillis(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG)
-                    - CURRENT_SYSTEM_TIME_MS;
+                    - currentTimeStamp;
         assertEquals(firstIntervalMs, WifiConnectivityManager.PERIODIC_SCAN_INTERVAL_MS);
 
+        currentTimeStamp += firstIntervalMs;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
         // Now fire the first periodic scan alarm timer
         mAlarmManager.dispatch(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG);
         mLooper.dispatchAll();
@@ -604,11 +627,14 @@ public class WifiConnectivityManagerTest {
         // Get the second periodic scan interval
         long secondIntervalMs = mAlarmManager
                     .getTriggerTimeMillis(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG)
-                    - CURRENT_SYSTEM_TIME_MS;
+                    - currentTimeStamp;
 
         // Verify the intervals are exponential back off
         assertEquals(firstIntervalMs * 2, secondIntervalMs);
 
+        currentTimeStamp += secondIntervalMs;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
         // Make sure we eventually stay at the maximum scan interval.
         long intervalMs = 0;
         for (int i = 0; i < 5; i++) {
@@ -616,13 +642,59 @@ public class WifiConnectivityManagerTest {
             mLooper.dispatchAll();
             intervalMs = mAlarmManager
                     .getTriggerTimeMillis(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG)
-                    - CURRENT_SYSTEM_TIME_MS;
+                    - currentTimeStamp;
+            currentTimeStamp += intervalMs;
+            when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
         }
 
         assertEquals(intervalMs, WifiConnectivityManager.MAX_PERIODIC_SCAN_INTERVAL_MS);
     }
 
     /**
+     *  When screen on trigger two connection state change events back to back to
+     *  verify that the minium scan interval is enforced.
+     *
+     * Expected behavior: WifiConnectivityManager start the second periodic single
+     * scan PERIODIC_SCAN_INTERVAL_MS after the first one.
+     */
+    @Test
+    public void checkMinimumPeriodicScanIntervalWhenScreenOn() {
+        long currentTimeStamp = CURRENT_SYSTEM_TIME_MS;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
+        // Set screen to ON
+        mWifiConnectivityManager.handleScreenStateChanged(true);
+
+        // Wait for MAX_PERIODIC_SCAN_INTERVAL_MS so that any impact triggered
+        // by screen state change can settle
+        currentTimeStamp += WifiConnectivityManager.MAX_PERIODIC_SCAN_INTERVAL_MS;
+        long firstScanTimeStamp = currentTimeStamp;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
+        // Set WiFi to connected state to trigger the periodic scan
+        mWifiConnectivityManager.handleConnectionStateChanged(
+                WifiConnectivityManager.WIFI_STATE_CONNECTED);
+
+        // Set the second scan attempt time stamp.
+        currentTimeStamp += 2000;
+        when(mClock.elapsedRealtime()).thenReturn(currentTimeStamp);
+
+        // Set WiFi to disconnected state to trigger another periodic scan
+        mWifiConnectivityManager.handleConnectionStateChanged(
+                WifiConnectivityManager.WIFI_STATE_DISCONNECTED);
+
+        // Get the second periodic scan actual time stamp
+        long secondScanTimeStamp = mAlarmManager
+                    .getTriggerTimeMillis(WifiConnectivityManager.PERIODIC_SCAN_TIMER_TAG);
+
+        // Verify that the second scan is scheduled PERIODIC_SCAN_INTERVAL_MS after the
+        // very first scan.
+        assertEquals(secondScanTimeStamp, firstScanTimeStamp
+                       + WifiConnectivityManager.PERIODIC_SCAN_INTERVAL_MS);
+
+    }
+
+    /**
      * Verify that we perform full band scan when the currently connected network's tx/rx success
      * rate is low.
      *