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Commit 85bbc6e0 authored by Quang Luong's avatar Quang Luong
Browse files

Increase ScanResult cache eviction timeout for failed/aborted scans 

Currently ScanResults are evicted from WifiTracker's cache when they
are more than 15 seconds old. Since scans are conducted every 10
seconds, one aborted scan will cause no fresh scans to be seen until
20 seconds later, resulting in all scans to be evicted and the
wifi-picker completely emptying.

This change doubles the eviction timeout to 30 seconds if the last
scan was aborted, avoiding this case.

Bug: 113132408
Test: atest WifiTrackerTest
Change-Id: I2e3aad3a1470f52c3d87e657262a2c4de1bd2418
parent c27024d9

packages/SettingsLib/src/com/android/settingslib/wifi/WifiTracker.java

+17 −3
Original line number Diff line number Diff line
@@ -84,7 +84,7 @@ public class WifiTracker implements LifecycleObserver, OnStart, OnStop, OnDestro 
    private static final long DEFAULT_MAX_CACHED_SCORE_AGE_MILLIS = 20 * DateUtils.MINUTE_IN_MILLIS;



    /** Maximum age of scan results to hold onto while actively scanning. **/

    private static final long MAX_SCAN_RESULT_AGE_MILLIS = 15000;

    @VisibleForTesting static final long MAX_SCAN_RESULT_AGE_MILLIS = 15000;



    private static final String TAG = "WifiTracker";

    private static final boolean DBG() {
@@ -142,6 +142,13 @@ public class WifiTracker implements LifecycleObserver, OnStart, OnStop, OnDestro 
     */

    private boolean mStaleScanResults = true;



    /**

     * Tracks whether the latest SCAN_RESULTS_AVAILABLE_ACTION contained new scans. If not, then

     * we treat the last scan as an aborted scan and increase the eviction timeout window to avoid

     * completely flushing the AP list before the next successful scan completes.

     */

    private boolean mLastScanSucceeded = true;



    // Does not need to be locked as it only updated on the worker thread, with the exception of

    // during onStart, which occurs before the receiver is registered on the work handler.

    private final HashMap<String, ScanResult> mScanResultCache = new HashMap<>();
@@ -478,17 +485,22 @@ public class WifiTracker implements LifecycleObserver, OnStart, OnStop, OnDestro 
    }



    /**

     * Remove old scan results from the cache.

     * Remove old scan results from the cache. If {@link #mLastScanSucceeded} is false, then

     * increase the timeout window to avoid completely flushing the AP list before the next

     * successful scan completes.

     *

     * <p>Should only ever be invoked from {@link #updateScanResultCache(List)} when

     * {@link #mStaleScanResults} is false.

     */

    private void evictOldScans() {

        long evictionTimeoutMillis = mLastScanSucceeded ? MAX_SCAN_RESULT_AGE_MILLIS

                : MAX_SCAN_RESULT_AGE_MILLIS * 2;



        long nowMs = SystemClock.elapsedRealtime();

        for (Iterator<ScanResult> iter = mScanResultCache.values().iterator(); iter.hasNext(); ) {

            ScanResult result = iter.next();

            // result timestamp is in microseconds

            if (nowMs - result.timestamp / 1000 > MAX_SCAN_RESULT_AGE_MILLIS) {

            if (nowMs - result.timestamp / 1000 > evictionTimeoutMillis) {

                iter.remove();

            }

        }
@@ -840,6 +852,8 @@ public class WifiTracker implements LifecycleObserver, OnStart, OnStop, OnDestro 
                                WifiManager.WIFI_STATE_UNKNOWN));

            } else if (WifiManager.SCAN_RESULTS_AVAILABLE_ACTION.equals(action)) {

                mStaleScanResults = false;

                mLastScanSucceeded =

                        intent.getBooleanExtra(WifiManager.EXTRA_RESULTS_UPDATED, true);



                fetchScansAndConfigsAndUpdateAccessPoints();

            } else if (WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION.equals(action)

packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java

+37 −4
Original line number Diff line number Diff line
@@ -270,7 +270,7 @@ public class WifiTrackerTest { 
                SystemClock.elapsedRealtime() * 1000 /* microsecond timestamp */);

    }



    private static ScanResult buildStaleScanResult() {

    private static ScanResult buildScanResultWithTimestamp(long timestampMillis) {

        return new ScanResult(

                WifiSsid.createFromAsciiEncoded(SSID_3),

                BSSID_3,
@@ -280,7 +280,7 @@ public class WifiTrackerTest { 
                "", // capabilities

                RSSI_3,

                0, // frequency

                0 /* microsecond timestamp */);

                timestampMillis * 1000 /* microsecond timestamp */);

    }



    private static WifiConfiguration buildPasspointConfiguration(String fqdn, String friendlyName) {
@@ -379,6 +379,12 @@ public class WifiTrackerTest { 
        tracker.mReceiver.onReceive(mContext, i);

    }



    private void sendFailedScanResults(WifiTracker tracker) throws InterruptedException {

        Intent i = new Intent(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);

        i.putExtra(WifiManager.EXTRA_RESULTS_UPDATED, false);

        tracker.mReceiver.onReceive(mContext, i);

    }



    private void sendUpdatedScores() throws InterruptedException {

        Bundle attr1 = new Bundle();

        attr1.putParcelable(ScoredNetwork.ATTRIBUTES_KEY_BADGING_CURVE, mockBadgeCurve1);
@@ -982,8 +988,8 @@ public class WifiTrackerTest { 


    @Test

    public void onStart_updateScanResults_evictOldScanResult() {

        when(mockWifiManager.getScanResults()).thenReturn(

                Arrays.asList(buildScanResult1(), buildScanResult2(), buildStaleScanResult()));

        when(mockWifiManager.getScanResults()).thenReturn(Arrays.asList(

                buildScanResult1(), buildScanResult2(), buildScanResultWithTimestamp(0)));

        WifiTracker tracker = createMockedWifiTracker();



        tracker.forceUpdate();
@@ -994,6 +1000,33 @@ public class WifiTrackerTest { 
        assertThat(tracker.getAccessPoints().get(1).getBssid()).isEqualTo(BSSID_2);

    }



    /**

     * Verifies that a failed scan reported on SCAN_RESULTS_AVAILABLE_ACTION should increase the

     * ScanResult eviction timeout to twice the default.

     */

    @Test

    public void failedScan_increasesEvictionTimeout() throws InterruptedException {

        when(mockWifiManager.getScanResults()).thenReturn(Arrays.asList(

                buildScanResult1(), buildScanResult2(), buildScanResultWithTimestamp(

                        SystemClock.elapsedRealtime() - WifiTracker.MAX_SCAN_RESULT_AGE_MILLIS)));

        WifiTracker tracker = createMockedWifiTracker();



        sendFailedScanResults(tracker);



        // Failed scan increases timeout window to include the stale scan

        assertThat(tracker.getAccessPoints()).hasSize(3);

        assertThat(tracker.getAccessPoints().get(0).getBssid()).isEqualTo(BSSID_1);

        assertThat(tracker.getAccessPoints().get(1).getBssid()).isEqualTo(BSSID_2);

        assertThat(tracker.getAccessPoints().get(2).getBssid()).isEqualTo(BSSID_3);



        sendScanResults(tracker);



        // Successful scan resets the timeout window to remove the stale scan

        assertThat(tracker.getAccessPoints()).hasSize(2);

        assertThat(tracker.getAccessPoints().get(0).getBssid()).isEqualTo(BSSID_1);

        assertThat(tracker.getAccessPoints().get(1).getBssid()).isEqualTo(BSSID_2);

    }



    /**

     * Verifies that updatePasspointAccessPoints will only return AccessPoints whose

     * isPasspoint() evaluates as true.