Switch SkDestroyListener based on the flag.

Switch existing C SkDestroyListener and new Java SkDestroyListener based
on the experiment flag.

Bug: 217624062
Test: atest SkDestroyListenerTest
Change-Id: I7031ba7c155edb43e0e7b77449587058d6ba38fb

service-t/src/com/android/server/net/NetworkStatsService.java

@@ -162,11 +162,13 @@ import com.android.net.module.util.IBpfMap;
 import com.android.net.module.util.LocationPermissionChecker;
 import com.android.net.module.util.NetworkStatsUtils;
 import com.android.net.module.util.PermissionUtils;
+import com.android.net.module.util.SharedLog;
 import com.android.net.module.util.Struct;
 import com.android.net.module.util.Struct.U32;
 import com.android.net.module.util.Struct.U8;
 import com.android.net.module.util.bpf.CookieTagMapKey;
 import com.android.net.module.util.bpf.CookieTagMapValue;
+import com.android.server.BpfNetMaps;
 
 import java.io.File;
 import java.io.FileDescriptor;
@@ -454,6 +456,9 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
     @NonNull
     private final BpfInterfaceMapUpdater mInterfaceMapUpdater;
 
+    @Nullable
+    private final SkDestroyListener mSkDestroyListener;
+
     private static @NonNull Clock getDefaultClock() {
         return new BestClock(ZoneOffset.UTC, SystemClock.currentNetworkTimeClock(),
                 Clock.systemUTC());
@@ -587,6 +592,18 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
         mStatsMapA = mDeps.getStatsMapA();
         mStatsMapB = mDeps.getStatsMapB();
         mAppUidStatsMap = mDeps.getAppUidStatsMap();
+
+        // TODO: Remove bpfNetMaps creation and always start SkDestroyListener
+        // Following code is for the experiment to verify the SkDestroyListener refactoring. Based
+        // on the experiment flag, BpfNetMaps starts C SkDestroyListener (existing code) or
+        // NetworkStatsService starts Java SkDestroyListener (new code).
+        final BpfNetMaps bpfNetMaps = mDeps.makeBpfNetMaps(mContext);
+        if (bpfNetMaps.isSkDestroyListenerRunning()) {
+            mSkDestroyListener = null;
+        } else {
+            mSkDestroyListener = mDeps.makeSkDestroyListener(mCookieTagMap, mHandler);
+            mHandler.post(mSkDestroyListener::start);
+        }
     }
 
     /**
@@ -782,6 +799,17 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
         public boolean isDebuggable() {
             return Build.isDebuggable();
         }
+
+        /** Create a new BpfNetMaps. */
+        public BpfNetMaps makeBpfNetMaps(Context ctx) {
+            return new BpfNetMaps(ctx);
+        }
+
+        /** Create a new SkDestroyListener. */
+        public SkDestroyListener makeSkDestroyListener(
+                IBpfMap<CookieTagMapKey, CookieTagMapValue> cookieTagMap, Handler handler) {
+            return new SkDestroyListener(cookieTagMap, handler, new SharedLog(TAG));
+        }
     }
 
     /**

service-t/src/com/android/server/net/SkDestroyListener.java

@@ -0,0 +1,75 @@
+/*
+ * 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 com.android.server.net;
+
+import static android.system.OsConstants.NETLINK_INET_DIAG;
+
+import android.os.Handler;
+import android.system.ErrnoException;
+
+import com.android.net.module.util.IBpfMap;
+import com.android.net.module.util.SharedLog;
+import com.android.net.module.util.bpf.CookieTagMapKey;
+import com.android.net.module.util.bpf.CookieTagMapValue;
+import com.android.net.module.util.ip.NetlinkMonitor;
+import com.android.net.module.util.netlink.InetDiagMessage;
+import com.android.net.module.util.netlink.NetlinkMessage;
+import com.android.net.module.util.netlink.StructInetDiagSockId;
+
+/**
+ * Monitor socket destroy and delete entry from cookie tag bpf map.
+ */
+public class SkDestroyListener extends NetlinkMonitor {
+    private static final int SKNLGRP_INET_TCP_DESTROY = 1;
+    private static final int SKNLGRP_INET_UDP_DESTROY = 2;
+    private static final int SKNLGRP_INET6_TCP_DESTROY = 3;
+    private static final int SKNLGRP_INET6_UDP_DESTROY = 4;
+
+    // TODO: if too many sockets are closed too quickly, this can overflow the socket buffer, and
+    // some entries in mCookieTagMap will not be freed. In order to fix this it would be needed to
+    // periodically dump all sockets and remove the tag entries for sockets that have been closed.
+    // For now, set a large-enough buffer that hundreds of sockets can be closed without getting
+    // ENOBUFS and leaking mCookieTagMap entries.
+    private static final int SOCK_RCV_BUF_SIZE = 512 * 1024;
+
+    private final IBpfMap<CookieTagMapKey, CookieTagMapValue> mCookieTagMap;
+
+    SkDestroyListener(final IBpfMap<CookieTagMapKey, CookieTagMapValue> cookieTagMap,
+            final Handler handler, final SharedLog log) {
+        super(handler, log, "SkDestroyListener", NETLINK_INET_DIAG,
+                1 << (SKNLGRP_INET_TCP_DESTROY - 1)
+                        | 1 << (SKNLGRP_INET_UDP_DESTROY - 1)
+                        | 1 << (SKNLGRP_INET6_TCP_DESTROY - 1)
+                        | 1 << (SKNLGRP_INET6_UDP_DESTROY - 1),
+                SOCK_RCV_BUF_SIZE);
+        mCookieTagMap = cookieTagMap;
+    }
+
+    @Override
+    public void processNetlinkMessage(final NetlinkMessage nlMsg, final long whenMs) {
+        if (!(nlMsg instanceof InetDiagMessage)) {
+            mLog.e("Received non InetDiagMessage");
+            return;
+        }
+        final StructInetDiagSockId sockId = ((InetDiagMessage) nlMsg).inetDiagMsg.id;
+        try {
+            mCookieTagMap.deleteEntry(new CookieTagMapKey(sockId.cookie));
+        } catch (ErrnoException e) {
+            mLog.e("Failed to delete CookieTagMap entry for " + sockId.cookie  + ": " + e);
+        }
+    }
+}

service/src/com/android/server/BpfNetMaps.java

@@ -225,10 +225,14 @@ public class BpfNetMaps {
         Log.d(TAG, "BpfNetMaps is initialized with sEnableJavaBpfMap=" + sEnableJavaBpfMap);
 
         initBpfMaps();
-        native_init(true /* startSkDestroyListener */);
+        native_init(!sEnableJavaBpfMap /* startSkDestroyListener */);
         sInitialized = true;
     }
 
+    public boolean isSkDestroyListenerRunning() {
+        return !sEnableJavaBpfMap;
+    }
+
     /**
      * Dependencies of BpfNetMaps, for injection in tests.
      */

tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java

@@ -143,6 +143,7 @@ import com.android.net.module.util.Struct.U32;
 import com.android.net.module.util.Struct.U8;
 import com.android.net.module.util.bpf.CookieTagMapKey;
 import com.android.net.module.util.bpf.CookieTagMapValue;
+import com.android.server.BpfNetMaps;
 import com.android.server.net.NetworkStatsService.AlertObserver;
 import com.android.server.net.NetworkStatsService.NetworkStatsSettings;
 import com.android.server.net.NetworkStatsService.NetworkStatsSettings.Config;
@@ -248,6 +249,10 @@ public class NetworkStatsServiceTest extends NetworkStatsBaseTest {
     @Mock
     private LocationPermissionChecker mLocationPermissionChecker;
     private TestBpfMap<U32, U8> mUidCounterSetMap = spy(new TestBpfMap<>(U32.class, U8.class));
+    @Mock
+    private BpfNetMaps mBpfNetMaps;
+    @Mock
+    private SkDestroyListener mSkDestroyListener;
 
     private TestBpfMap<CookieTagMapKey, CookieTagMapValue> mCookieTagMap = new TestBpfMap<>(
             CookieTagMapKey.class, CookieTagMapValue.class);
@@ -500,6 +505,17 @@ public class NetworkStatsServiceTest extends NetworkStatsBaseTest {
             public boolean isDebuggable() {
                 return mIsDebuggable == Boolean.TRUE;
             }
+
+            @Override
+            public BpfNetMaps makeBpfNetMaps(Context ctx) {
+                return mBpfNetMaps;
+            }
+
+            @Override
+            public SkDestroyListener makeSkDestroyListener(
+                    IBpfMap<CookieTagMapKey, CookieTagMapValue> cookieTagMap, Handler handler) {
+                return mSkDestroyListener;
+            }
         };
     }