Fix NullPointerException happens in dumpCheckin

Currently dumpCheckin passes a null object to create
the contructor of NetworkStatsCollection.Key but the
constructor requires non-null object. Thus, it caused
the NPE in dumpCheckin. To fix this exception, create
an NetworkIdentitySet() object instead of using an
null object.

Bug: 225131008
Bug: 226539404
Test: dumpsys netstats --checkin is fine
      FrameworksNetTests
Change-Id: I7f2dadf0647b3f42e0f667d96291d2ae37e23faf

framework-t/src/android/net/NetworkIdentitySet.java

@@ -206,6 +206,7 @@ public class NetworkIdentitySet extends HashSet<NetworkIdentity> {
     public static int compare(@NonNull NetworkIdentitySet left, @NonNull NetworkIdentitySet right) {
         Objects.requireNonNull(left);
         Objects.requireNonNull(right);
+        if (left.isEmpty() && right.isEmpty()) return 0;
         if (left.isEmpty()) return -1;
         if (right.isEmpty()) return 1;
 

framework-t/src/android/net/NetworkStatsCollection.java

@@ -776,7 +776,7 @@ public class NetworkStatsCollection implements FileRotator.Reader, FileRotator.W
             if (!templateMatches(groupTemplate, key.ident)) continue;
             if (key.set >= NetworkStats.SET_DEBUG_START) continue;
 
-            final Key groupKey = new Key(null, key.uid, key.set, key.tag);
+            final Key groupKey = new Key(new NetworkIdentitySet(), key.uid, key.set, key.tag);
             NetworkStatsHistory groupHistory = grouped.get(groupKey);
             if (groupHistory == null) {
                 groupHistory = new NetworkStatsHistory(value.getBucketDuration());

tests/unit/Android.bp

@@ -63,6 +63,7 @@ filegroup {
         "java/android/net/IpSecManagerTest.java",
         "java/android/net/IpSecTransformTest.java",
         "java/android/net/KeepalivePacketDataUtilTest.java",
+        "java/android/net/NetworkIdentitySetTest.kt",
         "java/android/net/NetworkIdentityTest.kt",
         "java/android/net/NetworkStats*.java",
         "java/android/net/NetworkTemplateTest.kt",

tests/unit/java/android/net/NetworkIdentitySetTest.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.net
+
+import android.content.Context
+import android.net.ConnectivityManager.TYPE_MOBILE
+import android.os.Build
+import android.telephony.TelephonyManager
+import com.android.testutils.DevSdkIgnoreRule
+import com.android.testutils.DevSdkIgnoreRunner
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.Mockito.mock
+import kotlin.test.assertEquals
+
+private const val TEST_IMSI1 = "testimsi1"
+
+@DevSdkIgnoreRule.IgnoreUpTo(Build.VERSION_CODES.S_V2)
+@RunWith(DevSdkIgnoreRunner::class)
+class NetworkIdentitySetTest {
+    private val mockContext = mock(Context::class.java)
+
+    private fun buildMobileNetworkStateSnapshot(
+        caps: NetworkCapabilities,
+        subscriberId: String
+    ): NetworkStateSnapshot {
+        return NetworkStateSnapshot(mock(Network::class.java), caps,
+                LinkProperties(), subscriberId, TYPE_MOBILE)
+    }
+
+    @Test
+    fun testCompare() {
+        val ident1 = NetworkIdentity.buildNetworkIdentity(mockContext,
+            buildMobileNetworkStateSnapshot(NetworkCapabilities(), TEST_IMSI1),
+            false /* defaultNetwork */, TelephonyManager.NETWORK_TYPE_UMTS)
+        val ident2 = NetworkIdentity.buildNetworkIdentity(mockContext,
+            buildMobileNetworkStateSnapshot(NetworkCapabilities(), TEST_IMSI1),
+            true /* defaultNetwork */, TelephonyManager.NETWORK_TYPE_UMTS)
+
+        // Verify that the results of comparing two empty sets are equal
+        assertEquals(0, NetworkIdentitySet.compare(NetworkIdentitySet(), NetworkIdentitySet()))
+
+        val identSet1 = NetworkIdentitySet()
+        val identSet2 = NetworkIdentitySet()
+        identSet1.add(ident1)
+        identSet2.add(ident2)
+        assertEquals(-1, NetworkIdentitySet.compare(NetworkIdentitySet(), identSet1))
+        assertEquals(1, NetworkIdentitySet.compare(identSet1, NetworkIdentitySet()))
+        assertEquals(0, NetworkIdentitySet.compare(identSet1, identSet1))
+        assertEquals(-1, NetworkIdentitySet.compare(identSet1, identSet2))
+    }
+}