[WifiScoreReport] Stay on working wifi

If packets are actually moving in both directions at a sufficiently
high rate, stay on wifi.

Bug: 74613347
Test: Unit tests
Change-Id: I49862984c9c3f67d64669102bb929a07110797ba

3 files changed, 66 insertions, 0 deletions

diff --git a/service/java/com/android/server/wifi/ScoringParams.java b/service/java/com/android/server/wifi/ScoringParams.java
index 3fabfc4a5..0cad22531 100644
--- a/service/java/com/android/server/wifi/ScoringParams.java
+++ b/service/java/com/android/server/wifi/ScoringParams.java
@@ -54,6 +54,10 @@ public class ScoringParams {
         public static final String KEY_RSSI5 = "rssi5";
         public final int[] rssi5 = {-80, -77, -70, -57};
 
+        /** Guidelines based on packet rates (packets/sec) */
+        public static final String KEY_PPS = "pps";
+        public final int[] pps = {0, 1, 100};
+
         /** Number of seconds for RSSI forecast */
         public static final String KEY_HORIZON = "horizon";
         public static final int MIN_HORIZON = -9;
@@ -70,12 +74,16 @@ public class ScoringParams {
             for (int i = 0; i < rssi5.length; i++) {
                 rssi5[i] = source.rssi5[i];
             }
+            for (int i = 0; i < pps.length; i++) {
+                pps[i] = source.pps[i];
+            }
             horizon = source.horizon;
         }
 
         public void validate() throws IllegalArgumentException {
             validateRssiArray(rssi2);
             validateRssiArray(rssi5);
+            validateOrderedNonNegativeArray(pps);
             validateRange(horizon, MIN_HORIZON, MAX_HORIZON);
         }
 
@@ -94,6 +102,16 @@ public class ScoringParams {
             }
         }
 
+        private void validateOrderedNonNegativeArray(int[] a) throws IllegalArgumentException {
+            int low = 0;
+            for (int i = 0; i < a.length; i++) {
+                if (a[i] < low) {
+                    throw new IllegalArgumentException();
+                }
+                low = a[i];
+            }
+        }
+
         public void parseString(String kvList) throws IllegalArgumentException {
             KeyValueListParser parser = new KeyValueListParser(',');
             parser.setString(kvList);
@@ -102,6 +120,7 @@ public class ScoringParams {
             }
             updateIntArray(rssi2, parser, KEY_RSSI2);
             updateIntArray(rssi5, parser, KEY_RSSI5);
+            updateIntArray(pps, parser, KEY_PPS);
             horizon = updateInt(parser, KEY_HORIZON, horizon);
         }
 
@@ -134,6 +153,9 @@ public class ScoringParams {
             appendInts(sb, rssi2);
             appendKey(sb, KEY_RSSI5);
             appendInts(sb, rssi5);
+            //TODO(b/74613347) - leave these out, pending unit test updates
+            // appendKey(sb, KEY_PPS);
+            // appendInts(sb, pps);
             appendKey(sb, KEY_HORIZON);
             sb.append(horizon);
             return sb.toString();
@@ -297,6 +319,14 @@ public class ScoringParams {
         return mVal.horizon;
     }
 
+    /**
+     * Returns a packet rate that should be considered acceptable for staying on wifi,
+     * no matter how bad the RSSI gets (packets per second).
+     */
+    public int getYippeeSkippyPacketsPerSecond() {
+        return mVal.pps[2];
+    }
+
     private static final int MINIMUM_5GHZ_BAND_FREQUENCY_IN_MEGAHERTZ = 5000;
 
     private int[] getRssiArray(int frequency) {
diff --git a/service/java/com/android/server/wifi/WifiScoreReport.java b/service/java/com/android/server/wifi/WifiScoreReport.java
index e11b697b6..32529f88d 100644
--- a/service/java/com/android/server/wifi/WifiScoreReport.java
+++ b/service/java/com/android/server/wifi/WifiScoreReport.java
@@ -129,6 +129,13 @@ public class WifiScoreReport {
         score = s2;
 
         if (wifiInfo.score > ConnectedScore.WIFI_TRANSITION_SCORE
+                 && score <= ConnectedScore.WIFI_TRANSITION_SCORE
+                 && wifiInfo.txSuccessRate >= mScoringParams.getYippeeSkippyPacketsPerSecond()
+                 && wifiInfo.rxSuccessRate >= mScoringParams.getYippeeSkippyPacketsPerSecond()) {
+            score = ConnectedScore.WIFI_TRANSITION_SCORE + 1;
+        }
+
+        if (wifiInfo.score > ConnectedScore.WIFI_TRANSITION_SCORE
                  && score <= ConnectedScore.WIFI_TRANSITION_SCORE) {
             // We don't want to trigger a downward breach unless the rssi is
             // below the entry threshold.  There is noise in the measured rssi, and
diff --git a/tests/wifitests/src/com/android/server/wifi/WifiScoreReportTest.java b/tests/wifitests/src/com/android/server/wifi/WifiScoreReportTest.java
index d60264c61..bf662f01a 100644
--- a/tests/wifitests/src/com/android/server/wifi/WifiScoreReportTest.java
+++ b/tests/wifitests/src/com/android/server/wifi/WifiScoreReportTest.java
@@ -260,6 +260,35 @@ public class WifiScoreReportTest {
     }
 
     /**
+     * Don't breach if the success rates are great
+     *
+     * Ramp the RSSI down, but maintain a high packet throughput
+     *
+     * Expect score to stay above above threshold.
+     */
+    @Test
+    public void allowTerribleRssiIfDataIsMovingWell() throws Exception {
+        mWifiInfo.txSuccessRate = mScoringParams.getYippeeSkippyPacketsPerSecond() + 0.1;
+        mWifiInfo.rxSuccessRate = mScoringParams.getYippeeSkippyPacketsPerSecond() + 0.1;
+        assertTrue(mWifiInfo.txSuccessRate > 10);
+        mWifiInfo.setFrequency(5220);
+        for (int r = -30; r >= -200; r -= 2) {
+            mWifiInfo.setRssi(r);
+            mWifiScoreReport.calculateAndReportScore(mWifiInfo, mNetworkAgent, mWifiMetrics);
+            assertTrue(mWifiInfo.score > ConnectedScore.WIFI_TRANSITION_SCORE);
+        }
+        // If the throughput dips, we should let go
+        mWifiInfo.rxSuccessRate = mScoringParams.getYippeeSkippyPacketsPerSecond() - 0.1;
+        mWifiScoreReport.calculateAndReportScore(mWifiInfo, mNetworkAgent, mWifiMetrics);
+        assertTrue(mWifiInfo.score < ConnectedScore.WIFI_TRANSITION_SCORE);
+        // And even if throughput improves again, once we have decided to let go, disregard
+        // the good rates.
+        mWifiInfo.rxSuccessRate = mScoringParams.getYippeeSkippyPacketsPerSecond() + 0.1;
+        mWifiScoreReport.calculateAndReportScore(mWifiInfo, mNetworkAgent, mWifiMetrics);
+        assertTrue(mWifiInfo.score < ConnectedScore.WIFI_TRANSITION_SCORE);
+    }
+
+    /**
      * This setup causes some reports to be generated when println
      * methods are called, to check for "concurrent" modification
      * errors.