Add null check for clientInfo

If the binder death notification for a INsdManagerCallback was
received before any calls are received by NsdService, the
clientInfo would be cleared and cause NPE. Thus, add a null check
to prevent crash.

Bug: 241741274
Test: atest FrameworksNetTests
Change-Id: Iebe761cd579bf3ee46ead389620bed60a21e3154
diff --git a/service-t/src/com/android/server/NsdService.java b/service-t/src/com/android/server/NsdService.java
index 8818460..1226eea 100644
--- a/service-t/src/com/android/server/NsdService.java
+++ b/service-t/src/com/android/server/NsdService.java
@@ -295,6 +295,13 @@
                         if (DBG) Log.d(TAG, "Discover services");
                         args = (ListenerArgs) msg.obj;
                         clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in discovery");
+                            break;
+                        }
 
                         if (requestLimitReached(clientInfo)) {
                             clientInfo.onDiscoverServicesFailed(
@@ -321,6 +328,13 @@
                         if (DBG) Log.d(TAG, "Stop service discovery");
                         args = (ListenerArgs) msg.obj;
                         clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in stop discovery");
+                            break;
+                        }
 
                         try {
                             id = clientInfo.mClientIds.get(clientId);
@@ -341,6 +355,14 @@
                         if (DBG) Log.d(TAG, "Register service");
                         args = (ListenerArgs) msg.obj;
                         clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in registration");
+                            break;
+                        }
+
                         if (requestLimitReached(clientInfo)) {
                             clientInfo.onRegisterServiceFailed(
                                     clientId, NsdManager.FAILURE_MAX_LIMIT);
@@ -363,6 +385,9 @@
                         if (DBG) Log.d(TAG, "unregister service");
                         args = (ListenerArgs) msg.obj;
                         clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
                         if (clientInfo == null) {
                             Log.e(TAG, "Unknown connector in unregistration");
                             break;
@@ -380,6 +405,13 @@
                         if (DBG) Log.d(TAG, "Resolve service");
                         args = (ListenerArgs) msg.obj;
                         clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in resolution");
+                            break;
+                        }
 
                         if (clientInfo.mResolvedService != null) {
                             clientInfo.onResolveServiceFailed(
diff --git a/tests/unit/java/com/android/server/NsdServiceTest.java b/tests/unit/java/com/android/server/NsdServiceTest.java
index 1813393..5808beb 100644
--- a/tests/unit/java/com/android/server/NsdServiceTest.java
+++ b/tests/unit/java/com/android/server/NsdServiceTest.java
@@ -536,6 +536,25 @@
                 .onResolveFailed(any(), eq(FAILURE_INTERNAL_ERROR));
     }
 
+    @Test
+    public void testNoCrashWhenProcessResolutionAfterBinderDied() throws Exception {
+        final NsdManager client = connectClient(mService);
+        final INsdManagerCallback cb = getCallback();
+        final IBinder.DeathRecipient deathRecipient = verifyLinkToDeath(cb);
+        deathRecipient.binderDied();
+
+        final NsdServiceInfo request = new NsdServiceInfo(SERVICE_NAME, SERVICE_TYPE);
+        final ResolveListener resolveListener = mock(ResolveListener.class);
+        client.resolveService(request, resolveListener);
+        waitForIdle();
+
+        verify(mMockMDnsM, never()).registerEventListener(any());
+        verify(mMockMDnsM, never()).startDaemon();
+        verify(mMockMDnsM, never()).resolve(anyInt() /* id */, anyString() /* serviceName */,
+                anyString() /* registrationType */, anyString() /* domain */,
+                anyInt()/* interfaceIdx */);
+    }
+
     private void waitForIdle() {
         HandlerUtils.waitForIdle(mHandler, TIMEOUT_MS);
     }