Do not immediately send new queries on cache hit

If a listener request is fulfilled immediately from cache, do not
restart queries immediately, but just schedule the next run.

This avoids doubling the number of queries when discovery, then resolve
is requested.

Bug: 281793453
Test: atest
(cherry picked from https://android-review.googlesource.com/q/commit:58bb0a129a4eb1f19904265104af2a14db248cb3)
Merged-In: Ibe41ee20427068a1ccdbc1f04525988a89a58899
Change-Id: Ibe41ee20427068a1ccdbc1f04525988a89a58899

service-t/src/com/android/server/connectivity/mdns/MdnsServiceTypeClient.java

@@ -175,6 +175,7 @@ public class MdnsServiceTypeClient {
             @NonNull MdnsSearchOptions searchOptions) {
         synchronized (lock) {
             this.searchOptions = searchOptions;
+            boolean hadReply = false;
             if (listeners.put(listener, searchOptions) == null) {
                 for (MdnsResponse existingResponse : instanceNameToResponse.values()) {
                     if (!responseMatchesOptions(existingResponse, searchOptions)) continue;
@@ -183,6 +184,7 @@ public class MdnsServiceTypeClient {
                     listener.onServiceNameDiscovered(info);
                     if (existingResponse.isComplete()) {
                         listener.onServiceFound(info);
+                        hadReply = true;
                     }
                 }
             }
@@ -192,14 +194,16 @@ public class MdnsServiceTypeClient {
             }
             // Keep tracking the ScheduledFuture for the task so we can cancel it if caller is not
             // interested anymore.
-            requestTaskFuture =
-                    executor.submit(
-                            new QueryTask(
-                                    new QueryTaskConfig(
-                                            searchOptions.getSubtypes(),
-                                            searchOptions.isPassiveMode(),
-                                            ++currentSessionId,
-                                            searchOptions.getNetwork())));
+            final QueryTaskConfig taskConfig = new QueryTaskConfig(
+                    searchOptions.getSubtypes(),
+                    searchOptions.isPassiveMode(),
+                    ++currentSessionId,
+                    searchOptions.getNetwork());
+            if (hadReply) {
+                requestTaskFuture = scheduleNextRunLocked(taskConfig);
+            } else {
+                requestTaskFuture = executor.submit(new QueryTask(taskConfig));
+            }
         }
     }
 
@@ -552,11 +556,14 @@ public class MdnsServiceTypeClient {
                         }
                     }
                 }
-                QueryTaskConfig config = this.config.getConfigForNextRun();
-                requestTaskFuture =
-                        executor.schedule(
-                                new QueryTask(config), config.timeToRunNextTaskInMs, MILLISECONDS);
+                requestTaskFuture = scheduleNextRunLocked(this.config);
             }
         }
     }
+
+    @NonNull
+    private Future<?> scheduleNextRunLocked(@NonNull QueryTaskConfig lastRunConfig) {
+        QueryTaskConfig config = lastRunConfig.getConfigForNextRun();
+        return executor.schedule(new QueryTask(config), config.timeToRunNextTaskInMs, MILLISECONDS);
+    }
 }

tests/unit/java/com/android/server/connectivity/mdns/MdnsServiceTypeClientTests.java

@@ -21,6 +21,7 @@ import static com.android.testutils.DevSdkIgnoreRuleKt.SC_V2;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
@@ -422,6 +423,34 @@ public class MdnsServiceTypeClientTests {
         assertNull(currentThreadExecutor.getAndClearLastScheduledRunnable());
     }
 
+    @Test
+    public void testQueryScheduledWhenAnsweredFromCache() {
+        final MdnsSearchOptions searchOptions = MdnsSearchOptions.getDefaultOptions();
+        client.startSendAndReceive(mockListenerOne, searchOptions);
+        assertNotNull(currentThreadExecutor.getAndClearSubmittedRunnable());
+
+        client.processResponse(createResponse(
+                "service-instance-1", "192.0.2.123", 5353,
+                SERVICE_TYPE_LABELS,
+                Collections.emptyMap(), TEST_TTL), /* interfaceIndex= */ 20, mockNetwork);
+
+        verify(mockListenerOne).onServiceNameDiscovered(any());
+        verify(mockListenerOne).onServiceFound(any());
+
+        // File another identical query
+        client.startSendAndReceive(mockListenerTwo, searchOptions);
+
+        verify(mockListenerTwo).onServiceNameDiscovered(any());
+        verify(mockListenerTwo).onServiceFound(any());
+
+        // This time no query is submitted, only scheduled
+        assertNull(currentThreadExecutor.getAndClearSubmittedRunnable());
+        assertNotNull(currentThreadExecutor.getAndClearLastScheduledRunnable());
+        // This just skips the first query of the first burst
+        assertEquals(MdnsConfigs.timeBetweenQueriesInBurstMs(),
+                currentThreadExecutor.getAndClearLastScheduledDelayInMs());
+    }
+
     private static void verifyServiceInfo(MdnsServiceInfo serviceInfo, String serviceName,
             String[] serviceType, List<String> ipv4Addresses, List<String> ipv6Addresses, int port,
             List<String> subTypes, Map<String, String> attributes, int interfaceIndex,