diff --git a/core/java/android/net/ConnectivityManager.java b/core/java/android/net/ConnectivityManager.java
index b9e9b28..0afb546 100644
--- a/core/java/android/net/ConnectivityManager.java
+++ b/core/java/android/net/ConnectivityManager.java
@@ -1825,6 +1825,16 @@
         return (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
     }
 
+    /* TODO: These permissions checks don't belong in client-side code. Move them to
+     * services.jar, possibly in com.android.server.net. */
+
+    /** {@hide} */
+    public static final boolean checkChangePermission(Context context) {
+        int uid = Binder.getCallingUid();
+        return Settings.checkAndNoteChangeNetworkStateOperation(context, uid, Settings
+                .getPackageNameForUid(context, uid), false /* throwException */);
+    }
+
     /** {@hide} */
     public static final void enforceChangePermission(Context context) {
         int uid = Binder.getCallingUid();
diff --git a/core/java/android/net/NetworkCapabilities.java b/core/java/android/net/NetworkCapabilities.java
index 6243f46..56eba4f 100644
--- a/core/java/android/net/NetworkCapabilities.java
+++ b/core/java/android/net/NetworkCapabilities.java
@@ -182,8 +182,15 @@
      */
     public static final int NET_CAPABILITY_CAPTIVE_PORTAL = 17;
 
+    /**
+     * Indicates that this network is available for use by apps, and not a network that is being
+     * kept up in the background to facilitate fast network switching.
+     * @hide
+     */
+    public static final int NET_CAPABILITY_FOREGROUND = 18;
+
     private static final int MIN_NET_CAPABILITY = NET_CAPABILITY_MMS;
-    private static final int MAX_NET_CAPABILITY = NET_CAPABILITY_CAPTIVE_PORTAL;
+    private static final int MAX_NET_CAPABILITY = NET_CAPABILITY_FOREGROUND;
 
     /**
      * Network capabilities that are expected to be mutable, i.e., can change while a particular
@@ -194,7 +201,8 @@
             // http://b/18206275
             (1 << NET_CAPABILITY_TRUSTED) |
             (1 << NET_CAPABILITY_VALIDATED) |
-            (1 << NET_CAPABILITY_CAPTIVE_PORTAL);
+            (1 << NET_CAPABILITY_CAPTIVE_PORTAL) |
+            (1 << NET_CAPABILITY_FOREGROUND);
 
     /**
      * Network specifier for factories which want to match any network specifier
@@ -217,8 +225,7 @@
      * get immediately torn down because they do not have the requested capability.
      */
     private static final long NON_REQUESTABLE_CAPABILITIES =
-            (1 << NET_CAPABILITY_VALIDATED) |
-            (1 << NET_CAPABILITY_CAPTIVE_PORTAL);
+            MUTABLE_CAPABILITIES & ~(1 << NET_CAPABILITY_TRUSTED);
 
     /**
      * Capabilities that are set by default when the object is constructed.
@@ -325,6 +332,7 @@
     public String describeFirstNonRequestableCapability() {
         if (hasCapability(NET_CAPABILITY_VALIDATED)) return "NET_CAPABILITY_VALIDATED";
         if (hasCapability(NET_CAPABILITY_CAPTIVE_PORTAL)) return "NET_CAPABILITY_CAPTIVE_PORTAL";
+        if (hasCapability(NET_CAPABILITY_FOREGROUND)) return "NET_CAPABILITY_FOREGROUND";
         // This cannot happen unless the preceding checks are incomplete.
         if ((mNetworkCapabilities & NON_REQUESTABLE_CAPABILITIES) != 0) {
             return "unknown non-requestable capabilities " + Long.toHexString(mNetworkCapabilities);
@@ -352,6 +360,11 @@
                 (that.mNetworkCapabilities & ~MUTABLE_CAPABILITIES));
     }
 
+    private boolean equalsNetCapabilitiesRequestable(NetworkCapabilities that) {
+        return ((this.mNetworkCapabilities & ~NON_REQUESTABLE_CAPABILITIES) ==
+                (that.mNetworkCapabilities & ~NON_REQUESTABLE_CAPABILITIES));
+    }
+
     /**
      * Removes the NET_CAPABILITY_NOT_RESTRICTED capability if all the capabilities it provides are
      * typically provided by restricted networks.
@@ -749,6 +762,19 @@
                 equalsSpecifier(nc));
     }
 
+    /**
+     * Checks that our requestable capabilities are the same as those of the given
+     * {@code NetworkCapabilities}.
+     *
+     * @hide
+     */
+    public boolean equalRequestableCapabilities(NetworkCapabilities nc) {
+        if (nc == null) return false;
+        return (equalsNetCapabilitiesRequestable(nc) &&
+                equalsTransportTypes(nc) &&
+                equalsSpecifier(nc));
+    }
+
     @Override
     public boolean equals(Object obj) {
         if (obj == null || (obj instanceof NetworkCapabilities == false)) return false;
@@ -833,6 +859,7 @@
                 case NET_CAPABILITY_NOT_VPN:        capabilities += "NOT_VPN"; break;
                 case NET_CAPABILITY_VALIDATED:      capabilities += "VALIDATED"; break;
                 case NET_CAPABILITY_CAPTIVE_PORTAL: capabilities += "CAPTIVE_PORTAL"; break;
+                case NET_CAPABILITY_FOREGROUND:     capabilities += "FOREGROUND"; break;
             }
             if (++i < types.length) capabilities += "&";
         }
diff --git a/core/java/android/net/NetworkRequest.java b/core/java/android/net/NetworkRequest.java
index 4501f7b..ae72470 100644
--- a/core/java/android/net/NetworkRequest.java
+++ b/core/java/android/net/NetworkRequest.java
@@ -49,7 +49,7 @@
     public final int legacyType;
 
     /**
-     * A NetworkRequest as used by the system can be one of three types:
+     * A NetworkRequest as used by the system can be one of the following types:
      *
      *     - LISTEN, for which the framework will issue callbacks about any
      *       and all networks that match the specified NetworkCapabilities,
@@ -64,7 +64,20 @@
      *       current network (if any) that matches the capabilities of the
      *       default Internet request (mDefaultRequest), but which cannot cause
      *       the framework to either create or retain the existence of any
-     *       specific network.
+     *       specific network. Note that from the point of view of the request
+     *       matching code, TRACK_DEFAULT is identical to REQUEST: its special
+     *       behaviour is not due to different semantics, but to the fact that
+     *       the system will only ever create a TRACK_DEFAULT with capabilities
+     *       that are identical to the default request's capabilities, thus
+     *       causing it to share fate in every way with the default request.
+     *
+     *     - BACKGROUND_REQUEST, like REQUEST but does not cause any networks
+     *       to retain the NET_CAPABILITY_FOREGROUND capability. A network with
+     *       no foreground requests is in the background. A network that has
+     *       one or more background requests and loses its last foreground
+     *       request to a higher-scoring network will not go into the
+     *       background immediately, but will linger and go into the background
+     *       after the linger timeout.
      *
      *     - The value NONE is used only by applications. When an application
      *       creates a NetworkRequest, it does not have a type; the type is set
@@ -77,7 +90,8 @@
         NONE,
         LISTEN,
         TRACK_DEFAULT,
-        REQUEST
+        REQUEST,
+        BACKGROUND_REQUEST,
     };
 
     /**
@@ -140,7 +154,7 @@
          * Add the given capability requirement to this builder.  These represent
          * the requested network's required capabilities.  Note that when searching
          * for a network to satisfy a request, all capabilities requested must be
-         * satisfied.  See {@link NetworkCapabilities} for {@code NET_CAPABILITIY_*}
+         * satisfied.  See {@link NetworkCapabilities} for {@code NET_CAPABILITY_*}
          * definitions.
          *
          * @param capability The {@code NetworkCapabilities.NET_CAPABILITY_*} to add.
@@ -284,7 +298,7 @@
         };
 
     /**
-     * Returns true iff. the contained NetworkRequest is of type LISTEN.
+     * Returns true iff. this NetworkRequest is of type LISTEN.
      *
      * @hide
      */
@@ -298,8 +312,9 @@
      *     - should be associated with at most one satisfying network
      *       at a time;
      *
-     *     - should cause a network to be kept up if it is the best network
-     *       which can satisfy the NetworkRequest.
+     *     - should cause a network to be kept up, but not necessarily in
+     *       the foreground, if it is the best network which can satisfy the
+     *       NetworkRequest.
      *
      * For full detail of how isRequest() is used for pairing Networks with
      * NetworkRequests read rematchNetworkAndRequests().
@@ -307,9 +322,36 @@
      * @hide
      */
     public boolean isRequest() {
+        return isForegroundRequest() || isBackgroundRequest();
+    }
+
+    /**
+     * Returns true iff. the contained NetworkRequest is one that:
+     *
+     *     - should be associated with at most one satisfying network
+     *       at a time;
+     *
+     *     - should cause a network to be kept up and in the foreground if
+     *       it is the best network which can satisfy the NetworkRequest.
+     *
+     * For full detail of how isRequest() is used for pairing Networks with
+     * NetworkRequests read rematchNetworkAndRequests().
+     *
+     * @hide
+     */
+    public boolean isForegroundRequest() {
         return type == Type.TRACK_DEFAULT || type == Type.REQUEST;
     }
 
+    /**
+     * Returns true iff. this NetworkRequest is of type BACKGROUND_REQUEST.
+     *
+     * @hide
+     */
+    public boolean isBackgroundRequest() {
+        return type == Type.BACKGROUND_REQUEST;
+    }
+
     public String toString() {
         return "NetworkRequest [ " + type + " id=" + requestId +
                 (legacyType != ConnectivityManager.TYPE_NONE ? ", legacyType=" + legacyType : "") +
diff --git a/core/tests/coretests/src/android/net/NetworkStatsTest.java b/core/tests/coretests/src/android/net/NetworkStatsTest.java
index 9074f8a..d48a67a 100644
--- a/core/tests/coretests/src/android/net/NetworkStatsTest.java
+++ b/core/tests/coretests/src/android/net/NetworkStatsTest.java
@@ -454,7 +454,7 @@
             .addValues(underlyingIface, tunUid, SET_FOREGROUND, TAG_NONE, 0L, 0L, 0L, 0L, 0L);
 
         assertTrue(delta.migrateTun(tunUid, tunIface, underlyingIface));
-        assertEquals(21, delta.size());
+        assertEquals(20, delta.size());
 
         // tunIface and TEST_IFACE entries are not changed.
         assertValues(delta, 0, tunIface, 10100, SET_DEFAULT, TAG_NONE, ROAMING_NO,
@@ -478,38 +478,89 @@
 
         // Existing underlying Iface entries are updated
         assertValues(delta, 9, underlyingIface, 10100, SET_DEFAULT, TAG_NONE, ROAMING_NO,
-                44783L, 54L, 13829L, 60L, 0L);
+                44783L, 54L, 14178L, 62L, 0L);
         assertValues(delta, 10, underlyingIface, 10100, SET_FOREGROUND, TAG_NONE, ROAMING_NO,
                 0L, 0L, 0L, 0L, 0L);
 
         // VPN underlying Iface entries are updated
         assertValues(delta, 11, underlyingIface, tunUid, SET_DEFAULT, TAG_NONE, ROAMING_NO,
-                28304L, 27L, 1719L, 12L, 0L);
+                28304L, 27L, 1L, 2L, 0L);
         assertValues(delta, 12, underlyingIface, tunUid, SET_FOREGROUND, TAG_NONE, ROAMING_NO,
                 0L, 0L, 0L, 0L, 0L);
 
         // New entries are added for new application's underlying Iface traffic
         assertContains(delta, underlyingIface, 10120, SET_DEFAULT, TAG_NONE, ROAMING_NO,
-                72667L, 197L, 41872L, 219L, 0L);
+                72667L, 197L, 43123L, 227L, 0L);
         assertContains(delta, underlyingIface, 10120, SET_FOREGROUND, TAG_NONE, ROAMING_NO,
-                9297L, 17L, 3936, 19L, 0L);
+                9297L, 17L, 4054, 19L, 0L);
         assertContains(delta, underlyingIface, 10120, SET_DEFAULT, testTag1, ROAMING_NO,
-                21691L, 41L, 13179L, 46L, 0L);
+                21691L, 41L, 13572L, 48L, 0L);
         assertContains(delta, underlyingIface, 10120, SET_FOREGROUND, testTag1, ROAMING_NO,
-                1281L, 2L, 634L, 1L, 0L);
+                1281L, 2L, 653L, 1L, 0L);
 
         // New entries are added for debug purpose
         assertContains(delta, underlyingIface, 10100, SET_DBG_VPN_IN, TAG_NONE, ROAMING_NO,
-                39605L, 46L, 11690, 49, 0);
+                39605L, 46L, 12039, 51, 0);
         assertContains(delta, underlyingIface, 10120, SET_DBG_VPN_IN, TAG_NONE, ROAMING_NO,
-                81964, 214, 45808, 238, 0);
-        assertContains(delta, underlyingIface, tunUid, SET_DBG_VPN_IN, TAG_NONE, ROAMING_NO,
-                4983, 10, 1717, 10, 0);
+                81964, 214, 47177, 246, 0);
         assertContains(delta, underlyingIface, tunUid, SET_DBG_VPN_OUT, TAG_NONE, ROAMING_ALL,
-                126552, 270, 59215, 297, 0);
+                121569, 260, 59216, 297, 0);
 
     }
 
+    // Tests a case where all of the data received by the tun0 interface is echo back into the tun0
+    // interface by the vpn app before it's sent out of the underlying interface. The VPN app should
+    // not be charged for the echoed data but it should still be charged for any extra data it sends
+    // via the underlying interface.
+    public void testMigrateTun_VpnAsLoopback() {
+        final int tunUid = 10030;
+        final String tunIface = "tun0";
+        final String underlyingIface = "wlan0";
+        NetworkStats delta = new NetworkStats(TEST_START, 9)
+            // 2 different apps sent/receive data via tun0.
+            .addValues(tunIface, 10100, SET_DEFAULT, TAG_NONE, 50000L, 25L, 100000L, 50L, 0L)
+            .addValues(tunIface, 20100, SET_DEFAULT, TAG_NONE, 500L, 2L, 200L, 5L, 0L)
+            // VPN package resends data through the tunnel (with exaggerated overhead)
+            .addValues(tunIface, tunUid, SET_DEFAULT, TAG_NONE, 240000, 100L, 120000L, 60L, 0L)
+            // 1 app already has some traffic on the underlying interface, the other doesn't yet
+            .addValues(underlyingIface, 10100, SET_DEFAULT, TAG_NONE, 1000L, 10L, 2000L, 20L, 0L)
+            // Traffic through the underlying interface via the vpn app.
+            // This test should redistribute this data correctly.
+            .addValues(underlyingIface, tunUid, SET_DEFAULT, TAG_NONE,
+                    75500L, 37L, 130000L, 70L, 0L);
+
+        assertTrue(delta.migrateTun(tunUid, tunIface, underlyingIface));
+        assertEquals(9, delta.size());
+
+        // tunIface entries should not be changed.
+        assertValues(delta, 0, tunIface, 10100, SET_DEFAULT, TAG_NONE, ROAMING_NO,
+                50000L, 25L, 100000L, 50L, 0L);
+        assertValues(delta, 1, tunIface, 20100, SET_DEFAULT, TAG_NONE, ROAMING_NO,
+                500L, 2L, 200L, 5L, 0L);
+        assertValues(delta, 2, tunIface, tunUid, SET_DEFAULT, TAG_NONE, ROAMING_NO,
+                240000L, 100L, 120000L, 60L, 0L);
+
+        // Existing underlying Iface entries are updated
+        assertValues(delta, 3, underlyingIface, 10100, SET_DEFAULT, TAG_NONE, ROAMING_NO,
+                51000L, 35L, 102000L, 70L, 0L);
+
+        // VPN underlying Iface entries are updated
+        assertValues(delta, 4, underlyingIface, tunUid, SET_DEFAULT, TAG_NONE, ROAMING_NO,
+                25000L, 10L, 29800L, 15L, 0L);
+
+        // New entries are added for new application's underlying Iface traffic
+        assertContains(delta, underlyingIface, 20100, SET_DEFAULT, TAG_NONE, ROAMING_NO,
+                500L, 2L, 200L, 5L, 0L);
+
+        // New entries are added for debug purpose
+        assertContains(delta, underlyingIface, 10100, SET_DBG_VPN_IN, TAG_NONE, ROAMING_NO,
+                50000L, 25L, 100000L, 50L, 0L);
+        assertContains(delta, underlyingIface, 20100, SET_DBG_VPN_IN, TAG_NONE, ROAMING_NO,
+                500, 2L, 200L, 5L, 0L);
+        assertContains(delta, underlyingIface, tunUid, SET_DBG_VPN_OUT, TAG_NONE, ROAMING_ALL,
+                50500L, 27L, 100200L, 55, 0);
+    }
+
     private static void assertContains(NetworkStats stats,  String iface, int uid, int set,
             int tag, int roaming, long rxBytes, long rxPackets, long txBytes, long txPackets,
             long operations) {
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 989892f..5f59e32 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -24,6 +24,7 @@
 import static android.net.ConnectivityManager.getNetworkTypeName;
 import static android.net.ConnectivityManager.isNetworkTypeValid;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_CAPTIVE_PORTAL;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_FOREGROUND;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_NOT_METERED;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED;
@@ -263,6 +264,11 @@
         DONT_REAP
     };
 
+    private enum UnneededFor {
+        LINGER,    // Determine whether this network is unneeded and should be lingered.
+        TEARDOWN,  // Determine whether this network is unneeded and should be torn down.
+    }
+
     /**
      * used internally to change our mobile data enabled flag
      */
@@ -700,13 +706,13 @@
         if (DBG) log("ConnectivityService starting up");
 
         mMetricsLog = logger;
-        mDefaultRequest = createInternetRequestForTransport(-1);
+        mDefaultRequest = createInternetRequestForTransport(-1, NetworkRequest.Type.REQUEST);
         NetworkRequestInfo defaultNRI = new NetworkRequestInfo(null, mDefaultRequest, new Binder());
         mNetworkRequests.put(mDefaultRequest, defaultNRI);
         mNetworkRequestInfoLogs.log("REGISTER " + defaultNRI);
 
         mDefaultMobileDataRequest = createInternetRequestForTransport(
-                NetworkCapabilities.TRANSPORT_CELLULAR);
+                NetworkCapabilities.TRANSPORT_CELLULAR, NetworkRequest.Type.BACKGROUND_REQUEST);
 
         mHandlerThread = createHandlerThread();
         mHandlerThread.start();
@@ -809,7 +815,7 @@
         mTestMode = SystemProperties.get("cm.test.mode").equals("true")
                 && SystemProperties.get("ro.build.type").equals("eng");
 
-        mTethering = new Tethering(mContext, mNetd, statsService);
+        mTethering = new Tethering(mContext, mNetd, statsService, mPolicyManager);
 
         mPermissionMonitor = new PermissionMonitor(mContext, mNetd);
 
@@ -860,15 +866,15 @@
                 mContext, mHandler, () -> rematchForAvoidBadWifiUpdate());
     }
 
-    private NetworkRequest createInternetRequestForTransport(int transportType) {
+    private NetworkRequest createInternetRequestForTransport(
+            int transportType, NetworkRequest.Type type) {
         NetworkCapabilities netCap = new NetworkCapabilities();
         netCap.addCapability(NET_CAPABILITY_INTERNET);
         netCap.addCapability(NET_CAPABILITY_NOT_RESTRICTED);
         if (transportType > -1) {
             netCap.addTransportType(transportType);
         }
-        return new NetworkRequest(netCap, TYPE_NONE, nextNetworkRequestId(),
-                NetworkRequest.Type.REQUEST);
+        return new NetworkRequest(netCap, TYPE_NONE, nextNetworkRequestId(), type);
     }
 
     // Used only for testing.
@@ -1982,8 +1988,12 @@
         for (NetworkAgentInfo nai : mNetworkAgentInfos.values()) {
             pw.println(nai.toString());
             pw.increaseIndent();
-            pw.println(String.format("Requests: %d request/%d total",
-                    nai.numRequestNetworkRequests(), nai.numNetworkRequests()));
+            pw.println(String.format(
+                    "Requests: REQUEST:%d LISTEN:%d BACKGROUND_REQUEST:%d total:%d",
+                    nai.numForegroundNetworkRequests(),
+                    nai.numNetworkRequests() - nai.numRequestNetworkRequests(),
+                    nai.numBackgroundNetworkRequests(),
+                    nai.numNetworkRequests()));
             pw.increaseIndent();
             for (int i = 0; i < nai.numNetworkRequests(); i++) {
                 pw.println(nai.requestAt(i).toString());
@@ -2144,14 +2154,10 @@
                 case NetworkAgent.EVENT_NETWORK_CAPABILITIES_CHANGED: {
                     final NetworkCapabilities networkCapabilities = (NetworkCapabilities) msg.obj;
                     if (networkCapabilities.hasCapability(NET_CAPABILITY_CAPTIVE_PORTAL) ||
-                            networkCapabilities.hasCapability(NET_CAPABILITY_VALIDATED)) {
+                            networkCapabilities.hasCapability(NET_CAPABILITY_VALIDATED) ||
+                            networkCapabilities.hasCapability(NET_CAPABILITY_FOREGROUND)) {
                         Slog.wtf(TAG, "BUG: " + nai + " has CS-managed capability.");
                     }
-                    if (nai.everConnected && !nai.networkCapabilities.equalImmutableCapabilities(
-                            networkCapabilities)) {
-                        Slog.wtf(TAG, "BUG: " + nai + " changed immutable capabilities: "
-                                + nai.networkCapabilities + " -> " + networkCapabilities);
-                    }
                     updateCapabilities(nai.getCurrentScore(), nai, networkCapabilities);
                     break;
                 }
@@ -2311,15 +2317,13 @@
         // 3. If this network is unneeded (which implies it is not lingering), and there is at least
         //    one lingered request, start lingering.
         nai.updateLingerTimer();
-        if (nai.isLingering() && nai.numRequestNetworkRequests() > 0) {
+        if (nai.isLingering() && nai.numForegroundNetworkRequests() > 0) {
             if (DBG) log("Unlingering " + nai.name());
             nai.unlinger();
             logNetworkEvent(nai, NetworkEvent.NETWORK_UNLINGER);
-        } else if (unneeded(nai) && nai.getLingerExpiry() > 0) {  // unneeded() calls isLingering()
+        } else if (unneeded(nai, UnneededFor.LINGER) && nai.getLingerExpiry() > 0) {
             int lingerTime = (int) (nai.getLingerExpiry() - now);
-            if (DBG) {
-                Log.d(TAG, "Lingering " + nai.name() + " for " + lingerTime + "ms");
-            }
+            if (DBG) log("Lingering " + nai.name() + " for " + lingerTime + "ms");
             nai.linger();
             logNetworkEvent(nai, NetworkEvent.NETWORK_LINGER);
             notifyNetworkCallbacks(nai, ConnectivityManager.CALLBACK_LOSING, lingerTime);
@@ -2498,15 +2502,37 @@
         }
     }
 
-    // Is nai unneeded by all NetworkRequests (and should be disconnected)?
-    // This is whether it is satisfying any NetworkRequests or were it to become validated,
-    // would it have a chance of satisfying any NetworkRequests.
-    private boolean unneeded(NetworkAgentInfo nai) {
-        if (!nai.everConnected || nai.isVPN() ||
-               nai.isLingering() || nai.numRequestNetworkRequests() > 0) {
+    // Determines whether the network is the best (or could become the best, if it validated), for
+    // none of a particular type of NetworkRequests. The type of NetworkRequests considered depends
+    // on the value of reason:
+    //
+    // - UnneededFor.TEARDOWN: non-listen NetworkRequests. If a network is unneeded for this reason,
+    //   then it should be torn down.
+    // - UnneededFor.LINGER: foreground NetworkRequests. If a network is unneeded for this reason,
+    //   then it should be lingered.
+    private boolean unneeded(NetworkAgentInfo nai, UnneededFor reason) {
+        final int numRequests;
+        switch (reason) {
+            case TEARDOWN:
+                numRequests = nai.numRequestNetworkRequests();
+                break;
+            case LINGER:
+                numRequests = nai.numForegroundNetworkRequests();
+                break;
+            default:
+                Slog.wtf(TAG, "Invalid reason. Cannot happen.");
+                return true;
+        }
+
+        if (!nai.everConnected || nai.isVPN() || nai.isLingering() || numRequests > 0) {
             return false;
         }
         for (NetworkRequestInfo nri : mNetworkRequests.values()) {
+            if (reason == UnneededFor.LINGER && nri.request.isBackgroundRequest()) {
+                // Background requests don't affect lingering.
+                continue;
+            }
+
             // If this Network is already the highest scoring Network for a request, or if
             // there is hope for it to become one if it validated, then it is needed.
             if (nri.request.isRequest() && nai.satisfies(nri.request) &&
@@ -2594,6 +2620,7 @@
             boolean wasKept = false;
             NetworkAgentInfo nai = mNetworkForRequestId.get(nri.request.requestId);
             if (nai != null) {
+                boolean wasBackgroundNetwork = nai.isBackgroundNetwork();
                 nai.removeRequest(nri.request.requestId);
                 if (VDBG) {
                     log(" Removing from current network " + nai.name() +
@@ -2602,13 +2629,17 @@
                 // If there are still lingered requests on this network, don't tear it down,
                 // but resume lingering instead.
                 updateLingerState(nai, SystemClock.elapsedRealtime());
-                if (unneeded(nai)) {
+                if (unneeded(nai, UnneededFor.TEARDOWN)) {
                     if (DBG) log("no live requests for " + nai.name() + "; disconnecting");
                     teardownUnneededNetwork(nai);
                 } else {
                     wasKept = true;
                 }
                 mNetworkForRequestId.remove(nri.request.requestId);
+                if (!wasBackgroundNetwork && nai.isBackgroundNetwork()) {
+                    // Went from foreground to background.
+                    updateCapabilities(nai.getCurrentScore(), nai, nai.networkCapabilities);
+                }
             }
 
             // TODO: remove this code once we know that the Slog.wtf is never hit.
@@ -2961,12 +2992,6 @@
         ConnectivityManager.enforceTetherChangePermission(mContext);
         if (isTetheringSupported()) {
             final int status = mTethering.tether(iface);
-            if (status == ConnectivityManager.TETHER_ERROR_NO_ERROR) {
-                try {
-                    mPolicyManager.onTetheringChanged(iface, true);
-                } catch (RemoteException e) {
-                }
-            }
             return status;
         } else {
             return ConnectivityManager.TETHER_ERROR_UNSUPPORTED;
@@ -2980,12 +3005,6 @@
 
         if (isTetheringSupported()) {
             final int status = mTethering.untether(iface);
-            if (status == ConnectivityManager.TETHER_ERROR_NO_ERROR) {
-                try {
-                    mPolicyManager.onTetheringChanged(iface, false);
-                } catch (RemoteException e) {
-                }
-            }
             return status;
         } else {
             return ConnectivityManager.TETHER_ERROR_UNSUPPORTED;
@@ -4255,8 +4274,17 @@
             enforceAccessPermission();
         }
 
-        NetworkRequest networkRequest = new NetworkRequest(
-                new NetworkCapabilities(networkCapabilities), TYPE_NONE, nextNetworkRequestId(),
+        NetworkCapabilities nc = new NetworkCapabilities(networkCapabilities);
+        if (!ConnectivityManager.checkChangePermission(mContext)) {
+            // Apps without the CHANGE_NETWORK_STATE permission can't use background networks, so
+            // make all their listens include NET_CAPABILITY_FOREGROUND. That way, they will get
+            // onLost and onAvailable callbacks when networks move in and out of the background.
+            // There is no need to do this for requests because an app without CHANGE_NETWORK_STATE
+            // can't request networks.
+            nc.addCapability(NET_CAPABILITY_FOREGROUND);
+        }
+
+        NetworkRequest networkRequest = new NetworkRequest(nc, TYPE_NONE, nextNetworkRequestId(),
                 NetworkRequest.Type.LISTEN);
         NetworkRequestInfo nri = new NetworkRequestInfo(messenger, networkRequest, binder);
         if (VDBG) log("listenForNetwork for " + nri);
@@ -4571,6 +4599,17 @@
         mNumDnsEntries = last;
     }
 
+    private String getNetworkPermission(NetworkCapabilities nc) {
+        // TODO: make these permission strings AIDL constants instead.
+        if (!nc.hasCapability(NET_CAPABILITY_NOT_RESTRICTED)) {
+            return NetworkManagementService.PERMISSION_SYSTEM;
+        }
+        if (!nc.hasCapability(NET_CAPABILITY_FOREGROUND)) {
+            return NetworkManagementService.PERMISSION_NETWORK;
+        }
+        return null;
+    }
+
     /**
      * Update the NetworkCapabilities for {@code networkAgent} to {@code networkCapabilities}
      * augmented with any stateful capabilities implied from {@code networkAgent}
@@ -4583,6 +4622,12 @@
      */
     private void updateCapabilities(
             int oldScore, NetworkAgentInfo nai, NetworkCapabilities networkCapabilities) {
+        if (nai.everConnected && !nai.networkCapabilities.equalImmutableCapabilities(
+                networkCapabilities)) {
+            Slog.wtf(TAG, "BUG: " + nai + " changed immutable capabilities: "
+                    + nai.networkCapabilities + " -> " + networkCapabilities);
+        }
+
         // Don't modify caller's NetworkCapabilities.
         networkCapabilities = new NetworkCapabilities(networkCapabilities);
         if (nai.lastValidated) {
@@ -4595,20 +4640,38 @@
         } else {
             networkCapabilities.removeCapability(NET_CAPABILITY_CAPTIVE_PORTAL);
         }
-        if (!Objects.equals(nai.networkCapabilities, networkCapabilities)) {
-            if (nai.networkCapabilities.hasCapability(NET_CAPABILITY_NOT_RESTRICTED) !=
-                    networkCapabilities.hasCapability(NET_CAPABILITY_NOT_RESTRICTED)) {
-                try {
-                    mNetd.setNetworkPermission(nai.network.netId,
-                            networkCapabilities.hasCapability(NET_CAPABILITY_NOT_RESTRICTED) ?
-                                    null : NetworkManagementService.PERMISSION_SYSTEM);
-                } catch (RemoteException e) {
-                    loge("Exception in setNetworkPermission: " + e);
-                }
+        if (nai.isBackgroundNetwork()) {
+            networkCapabilities.removeCapability(NET_CAPABILITY_FOREGROUND);
+        } else {
+            networkCapabilities.addCapability(NET_CAPABILITY_FOREGROUND);
+        }
+
+        if (Objects.equals(nai.networkCapabilities, networkCapabilities)) return;
+
+        final String oldPermission = getNetworkPermission(nai.networkCapabilities);
+        final String newPermission = getNetworkPermission(networkCapabilities);
+        if (!Objects.equals(oldPermission, newPermission) && nai.created && !nai.isVPN()) {
+            try {
+                mNetd.setNetworkPermission(nai.network.netId, newPermission);
+            } catch (RemoteException e) {
+                loge("Exception in setNetworkPermission: " + e);
             }
-            synchronized (nai) {
-                nai.networkCapabilities = networkCapabilities;
-            }
+        }
+
+        final NetworkCapabilities prevNc = nai.networkCapabilities;
+        synchronized (nai) {
+            nai.networkCapabilities = networkCapabilities;
+        }
+        if (nai.getCurrentScore() == oldScore &&
+                networkCapabilities.equalRequestableCapabilities(prevNc)) {
+            // If the requestable capabilities haven't changed, and the score hasn't changed, then
+            // the change we're processing can't affect any requests, it can only affect the listens
+            // on this network. We might have been called by rematchNetworkAndRequests when a
+            // network changed foreground state.
+            processListenRequests(nai, true);
+        } else {
+            // If the requestable capabilities have changed or the score changed, we can't have been
+            // called by rematchNetworkAndRequests, so it's safe to start a rematch.
             rematchAllNetworksAndRequests(nai, oldScore);
             notifyNetworkCallbacks(nai, ConnectivityManager.CALLBACK_CAP_CHANGED);
         }
@@ -4731,8 +4794,13 @@
         // must be no other active linger timers, and we must stop lingering.
         oldNetwork.clearLingerState();
 
-        if (unneeded(oldNetwork)) {
+        if (unneeded(oldNetwork, UnneededFor.TEARDOWN)) {
+            // Tear the network down.
             teardownUnneededNetwork(oldNetwork);
+        } else {
+            // Put the network in the background.
+            updateCapabilities(oldNetwork.getCurrentScore(), oldNetwork,
+                    oldNetwork.networkCapabilities);
         }
     }
 
@@ -4750,6 +4818,31 @@
         setDefaultDnsSystemProperties(newNetwork.linkProperties.getDnsServers());
     }
 
+    private void processListenRequests(NetworkAgentInfo nai, boolean capabilitiesChanged) {
+        // For consistency with previous behaviour, send onLost callbacks before onAvailable.
+        for (NetworkRequestInfo nri : mNetworkRequests.values()) {
+            NetworkRequest nr = nri.request;
+            if (!nr.isListen()) continue;
+            if (nai.isSatisfyingRequest(nr.requestId) && !nai.satisfies(nr)) {
+                nai.removeRequest(nri.request.requestId);
+                callCallbackForRequest(nri, nai, ConnectivityManager.CALLBACK_LOST, 0);
+            }
+        }
+
+        if (capabilitiesChanged) {
+            notifyNetworkCallbacks(nai, ConnectivityManager.CALLBACK_CAP_CHANGED);
+        }
+
+        for (NetworkRequestInfo nri : mNetworkRequests.values()) {
+            NetworkRequest nr = nri.request;
+            if (!nr.isListen()) continue;
+            if (nai.satisfies(nr) && !nai.isSatisfyingRequest(nr.requestId)) {
+                nai.addRequest(nr);
+                notifyNetworkCallback(nai, nri);
+            }
+        }
+    }
+
     // Handles a network appearing or improving its score.
     //
     // - Evaluates all current NetworkRequests that can be
@@ -4783,13 +4876,25 @@
         boolean keep = newNetwork.isVPN();
         boolean isNewDefault = false;
         NetworkAgentInfo oldDefaultNetwork = null;
+
+        final boolean wasBackgroundNetwork = newNetwork.isBackgroundNetwork();
+        final int score = newNetwork.getCurrentScore();
+
         if (VDBG) log("rematching " + newNetwork.name());
+
         // Find and migrate to this Network any NetworkRequests for
         // which this network is now the best.
         ArrayList<NetworkAgentInfo> affectedNetworks = new ArrayList<NetworkAgentInfo>();
         ArrayList<NetworkRequestInfo> addedRequests = new ArrayList<NetworkRequestInfo>();
-        if (VDBG) log(" network has: " + newNetwork.networkCapabilities);
+        NetworkCapabilities nc = newNetwork.networkCapabilities;
+        if (VDBG) log(" network has: " + nc);
         for (NetworkRequestInfo nri : mNetworkRequests.values()) {
+            // Process requests in the first pass and listens in the second pass. This allows us to
+            // change a network's capabilities depending on which requests it has. This is only
+            // correct if the change in capabilities doesn't affect whether the network satisfies
+            // requests or not, and doesn't affect the network's score.
+            if (nri.request.isListen()) continue;
+
             final NetworkAgentInfo currentNetwork = mNetworkForRequestId.get(nri.request.requestId);
             final boolean satisfies = newNetwork.satisfies(nri.request);
             if (newNetwork == currentNetwork && satisfies) {
@@ -4804,22 +4909,14 @@
             // check if it satisfies the NetworkCapabilities
             if (VDBG) log("  checking if request is satisfied: " + nri.request);
             if (satisfies) {
-                if (nri.request.isListen()) {
-                    // This is not a request, it's a callback listener.
-                    // Add it to newNetwork regardless of score.
-                    if (newNetwork.addRequest(nri.request)) addedRequests.add(nri);
-                    continue;
-                }
-
                 // next check if it's better than any current network we're using for
                 // this request
                 if (VDBG) {
                     log("currentScore = " +
                             (currentNetwork != null ? currentNetwork.getCurrentScore() : 0) +
-                            ", newScore = " + newNetwork.getCurrentScore());
+                            ", newScore = " + score);
                 }
-                if (currentNetwork == null ||
-                        currentNetwork.getCurrentScore() < newNetwork.getCurrentScore()) {
+                if (currentNetwork == null || currentNetwork.getCurrentScore() < score) {
                     if (VDBG) log("rematch for " + newNetwork.name());
                     if (currentNetwork != null) {
                         if (VDBG) log("   accepting network in place of " + currentNetwork.name());
@@ -4841,7 +4938,7 @@
                     // TODO - this could get expensive if we have alot of requests for this
                     // network.  Think about if there is a way to reduce this.  Push
                     // netid->request mapping to each factory?
-                    sendUpdatedScoreToFactories(nri.request, newNetwork.getCurrentScore());
+                    sendUpdatedScoreToFactories(nri.request, score);
                     if (isDefaultRequest(nri)) {
                         isNewDefault = true;
                         oldDefaultNetwork = currentNetwork;
@@ -4867,16 +4964,14 @@
                     mNetworkForRequestId.remove(nri.request.requestId);
                     sendUpdatedScoreToFactories(nri.request, 0);
                 } else {
-                    if (nri.request.isRequest()) {
-                        Slog.wtf(TAG, "BUG: Removing request " + nri.request.requestId + " from " +
-                                newNetwork.name() +
-                                " without updating mNetworkForRequestId or factories!");
-                    }
+                    Slog.wtf(TAG, "BUG: Removing request " + nri.request.requestId + " from " +
+                            newNetwork.name() +
+                            " without updating mNetworkForRequestId or factories!");
                 }
-                // TODO: technically, sending CALLBACK_LOST here is
-                // incorrect if nri is a request (not a listen) and there
-                // is a replacement network currently connected that can
-                // satisfy it. However, the only capability that can both
+                // TODO: Technically, sending CALLBACK_LOST here is
+                // incorrect if there is a replacement network currently
+                // connected that can satisfy nri, which is a request
+                // (not a listen). However, the only capability that can both
                 // a) be requested and b) change is NET_CAPABILITY_TRUSTED,
                 // so this code is only incorrect for a network that loses
                 // the TRUSTED capability, which is a rare case.
@@ -4901,6 +4996,28 @@
             }
         }
 
+        if (!newNetwork.networkCapabilities.equalRequestableCapabilities(nc)) {
+            Slog.wtf(TAG, String.format(
+                    "BUG: %s changed requestable capabilities during rematch: %s -> %s",
+                    nc, newNetwork.networkCapabilities));
+        }
+        if (newNetwork.getCurrentScore() != score) {
+            Slog.wtf(TAG, String.format(
+                    "BUG: %s changed score during rematch: %d -> %d",
+                    score, newNetwork.getCurrentScore()));
+        }
+
+        // Second pass: process all listens.
+        if (wasBackgroundNetwork != newNetwork.isBackgroundNetwork()) {
+            // If the network went from background to foreground or vice versa, we need to update
+            // its foreground state. It is safe to do this after rematching the requests because
+            // NET_CAPABILITY_FOREGROUND does not affect requests, as is not a requestable
+            // capability and does not affect the network's score (see the Slog.wtf call above).
+            updateCapabilities(score, newNetwork, newNetwork.networkCapabilities);
+        } else {
+            processListenRequests(newNetwork, false);
+        }
+
         // do this after the default net is switched, but
         // before LegacyTypeTracker sends legacy broadcasts
         for (NetworkRequestInfo nri : addedRequests) notifyNetworkCallback(newNetwork, nri);
@@ -4978,7 +5095,7 @@
         }
         if (reapUnvalidatedNetworks == ReapUnvalidatedNetworks.REAP) {
             for (NetworkAgentInfo nai : mNetworkAgentInfos.values()) {
-                if (unneeded(nai)) {
+                if (unneeded(nai, UnneededFor.TEARDOWN)) {
                     if (nai.getLingerExpiry() > 0) {
                         // This network has active linger timers and no requests, but is not
                         // lingering. Linger it.
@@ -5092,6 +5209,10 @@
         if (!networkAgent.created
                 && (state == NetworkInfo.State.CONNECTED
                 || (state == NetworkInfo.State.CONNECTING && networkAgent.isVPN()))) {
+
+            // A network that has just connected has zero requests and is thus a foreground network.
+            networkAgent.networkCapabilities.addCapability(NET_CAPABILITY_FOREGROUND);
+
             try {
                 // This should never fail.  Specifying an already in use NetID will cause failure.
                 if (networkAgent.isVPN()) {
@@ -5101,9 +5222,7 @@
                                 !networkAgent.networkMisc.allowBypass));
                 } else {
                     mNetd.createPhysicalNetwork(networkAgent.network.netId,
-                            networkAgent.networkCapabilities.hasCapability(
-                                    NET_CAPABILITY_NOT_RESTRICTED) ?
-                                    null : NetworkManagementService.PERMISSION_SYSTEM);
+                            getNetworkPermission(networkAgent.networkCapabilities));
                 }
             } catch (Exception e) {
                 loge("Error creating network " + networkAgent.network.netId + ": "
@@ -5253,6 +5372,8 @@
             NetworkRequest nr = networkAgent.requestAt(i);
             NetworkRequestInfo nri = mNetworkRequests.get(nr);
             if (VDBG) log(" sending notification for " + nr);
+            // TODO: if we're in the middle of a rematch, can we send a CAP_CHANGED callback for
+            // a network that no longer satisfies the listen?
             if (nri.mPendingIntent == null) {
                 callCallbackForRequest(nri, networkAgent, notifyType, arg1);
             } else {
@@ -5324,7 +5445,7 @@
 
     @Override
     public String getCaptivePortalServerUrl() {
-        return NetworkMonitor.getCaptivePortalServerUrl(mContext);
+        return NetworkMonitor.getCaptivePortalServerHttpUrl(mContext);
     }
 
     @Override
diff --git a/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java b/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
index 9c48aee..2a618bc 100644
--- a/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
+++ b/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
@@ -104,14 +104,16 @@
 // -----------------------------------------------
 // If a network has no chance of satisfying any requests (even if it were to become validated
 // and enter state #5), ConnectivityService will disconnect the NetworkAgent's AsyncChannel.
-// If the network ever for any period of time had satisfied a NetworkRequest (i.e. had been
-// the highest scoring that satisfied the NetworkRequest's constraints), but is no longer the
-// highest scoring network for any NetworkRequest, then there will be a 30s pause before
-// ConnectivityService disconnects the NetworkAgent's AsyncChannel.  During this pause the
-// network is considered "lingering".  This pause exists to allow network communication to be
-// wrapped up rather than abruptly terminated.  During this pause if the network begins satisfying
-// a NetworkRequest, ConnectivityService will cancel the future disconnection of the NetworkAgent's
-// AsyncChannel, and the network is no longer considered "lingering".
+//
+// If the network was satisfying a foreground NetworkRequest (i.e. had been the highest scoring that
+// satisfied the NetworkRequest's constraints), but is no longer the highest scoring network for any
+// foreground NetworkRequest, then there will be a 30s pause to allow network communication to be
+// wrapped up rather than abruptly terminated. During this pause the network is said to be
+// "lingering". During this pause if the network begins satisfying a foreground NetworkRequest,
+// ConnectivityService will cancel the future disconnection of the NetworkAgent's AsyncChannel, and
+// the network is no longer considered "lingering". After the linger timer expires, if the network
+// is satisfying one or more background NetworkRequests it is kept up in the background. If it is
+// not, ConnectivityService disconnects the NetworkAgent's AsyncChannel.
 public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
 
     public NetworkInfo networkInfo;
@@ -230,11 +232,13 @@
 
     // The list of NetworkRequests being satisfied by this Network.
     private final SparseArray<NetworkRequest> mNetworkRequests = new SparseArray<>();
-    // The list of NetworkRequests that this Network previously satisfied with the highest
-    // score.  A non-empty list indicates that if this Network was validated it is lingered.
+
     // How many of the satisfied requests are actual requests and not listens.
     private int mNumRequestNetworkRequests = 0;
 
+    // How many of the satisfied requests are of type BACKGROUND_REQUEST.
+    private int mNumBackgroundNetworkRequests = 0;
+
     public final Messenger messenger;
     public final AsyncChannel asyncChannel;
 
@@ -268,6 +272,32 @@
     //
     // These functions must only called on ConnectivityService's main thread.
 
+    private static final boolean ADD = true;
+    private static final boolean REMOVE = false;
+
+    private void updateRequestCounts(boolean add, NetworkRequest request) {
+        int delta = add ? +1 : -1;
+        switch (request.type) {
+            case REQUEST:
+            case TRACK_DEFAULT:
+                mNumRequestNetworkRequests += delta;
+                break;
+
+            case BACKGROUND_REQUEST:
+                mNumRequestNetworkRequests += delta;
+                mNumBackgroundNetworkRequests += delta;
+                break;
+
+            case LISTEN:
+                break;
+
+            case NONE:
+            default:
+                Log.wtf(TAG, "Unhandled request type " + request.type);
+                break;
+        }
+    }
+
     /**
      * Add {@code networkRequest} to this network as it's satisfied by this network.
      * @return true if {@code networkRequest} was added or false if {@code networkRequest} was
@@ -276,9 +306,15 @@
     public boolean addRequest(NetworkRequest networkRequest) {
         NetworkRequest existing = mNetworkRequests.get(networkRequest.requestId);
         if (existing == networkRequest) return false;
-        if (existing != null && existing.isRequest()) mNumRequestNetworkRequests--;
+        if (existing != null) {
+            // Should only happen if the requestId wraps. If that happens lots of other things will
+            // be broken as well.
+            Log.wtf(TAG, String.format("Duplicate requestId for %s and %s on %s",
+                    networkRequest, existing, name()));
+            updateRequestCounts(REMOVE, existing);
+        }
         mNetworkRequests.put(networkRequest.requestId, networkRequest);
-        if (networkRequest.isRequest()) mNumRequestNetworkRequests++;
+        updateRequestCounts(ADD, networkRequest);
         return true;
     }
 
@@ -288,9 +324,9 @@
     public void removeRequest(int requestId) {
         NetworkRequest existing = mNetworkRequests.get(requestId);
         if (existing == null) return;
+        updateRequestCounts(REMOVE, existing);
         mNetworkRequests.remove(requestId);
         if (existing.isRequest()) {
-            mNumRequestNetworkRequests--;
             unlingerRequest(existing);
         }
     }
@@ -319,12 +355,37 @@
     }
 
     /**
+     * Returns the number of requests currently satisfied by this network of type
+     * {@link android.net.NetworkRequest.Type.BACKGROUND_REQUEST}.
+     */
+    public int numBackgroundNetworkRequests() {
+        return mNumBackgroundNetworkRequests;
+    }
+
+    /**
+     * Returns the number of foreground requests currently satisfied by this network.
+     */
+    public int numForegroundNetworkRequests() {
+        return mNumRequestNetworkRequests - mNumBackgroundNetworkRequests;
+    }
+
+    /**
      * Returns the number of requests of any type currently satisfied by this network.
      */
     public int numNetworkRequests() {
         return mNetworkRequests.size();
     }
 
+    /**
+     * Returns whether the network is a background network. A network is a background network if it
+     * is satisfying no foreground requests and at least one background request. (If it did not have
+     * a background request, it would be a speculative network that is only being kept up because
+     * it might satisfy a request if it validated).
+     */
+    public boolean isBackgroundNetwork() {
+        return !isVPN() && numForegroundNetworkRequests() == 0 && mNumBackgroundNetworkRequests > 0;
+    }
+
     // Does this network satisfy request?
     public boolean satisfies(NetworkRequest request) {
         return created &&
diff --git a/services/tests/servicestests/src/com/android/server/ConnectivityServiceTest.java b/services/tests/servicestests/src/com/android/server/ConnectivityServiceTest.java
index a656acc..4af1cf1 100644
--- a/services/tests/servicestests/src/com/android/server/ConnectivityServiceTest.java
+++ b/services/tests/servicestests/src/com/android/server/ConnectivityServiceTest.java
@@ -597,7 +597,7 @@
 
         @Override
         protected CaptivePortalProbeResult isCaptivePortal() {
-            return new CaptivePortalProbeResult(gen204ProbeResult, gen204ProbeRedirectUrl);
+            return new CaptivePortalProbeResult(gen204ProbeResult, gen204ProbeRedirectUrl, null);
         }
     }
 
@@ -746,6 +746,7 @@
     }
 
     public void tearDown() throws Exception {
+        setMobileDataAlwaysOn(false);
         if (mCellNetworkAgent != null) { mCellNetworkAgent.disconnect(); }
         if (mWiFiNetworkAgent != null) { mWiFiNetworkAgent.disconnect(); }
         mCellNetworkAgent = mWiFiNetworkAgent = null;
@@ -1843,6 +1844,85 @@
         mCm.unregisterNetworkCallback(cellNetworkCallback);
     }
 
+    private void setMobileDataAlwaysOn(boolean enable) {
+        ContentResolver cr = mServiceContext.getContentResolver();
+        Settings.Global.putInt(cr, Settings.Global.MOBILE_DATA_ALWAYS_ON, enable ? 1 : 0);
+        mService.updateMobileDataAlwaysOn();
+        mService.waitForIdle();
+    }
+
+    private boolean isForegroundNetwork(MockNetworkAgent network) {
+        NetworkCapabilities nc = mCm.getNetworkCapabilities(network.getNetwork());
+        assertNotNull(nc);
+        return nc.hasCapability(NET_CAPABILITY_FOREGROUND);
+    }
+
+    @SmallTest
+    public void testBackgroundNetworks() throws Exception {
+        // Create a background request. We can't do this ourselves because ConnectivityService
+        // doesn't have an API for it. So just turn on mobile data always on.
+        setMobileDataAlwaysOn(true);
+        final NetworkRequest request = new NetworkRequest.Builder().build();
+        final NetworkRequest fgRequest = new NetworkRequest.Builder()
+                .addCapability(NET_CAPABILITY_FOREGROUND).build();
+        final TestNetworkCallback callback = new TestNetworkCallback();
+        final TestNetworkCallback fgCallback = new TestNetworkCallback();
+        mCm.registerNetworkCallback(request, callback);
+        mCm.registerNetworkCallback(fgRequest, fgCallback);
+
+        mCellNetworkAgent = new MockNetworkAgent(TRANSPORT_CELLULAR);
+        mCellNetworkAgent.connect(true);
+        callback.expectCallback(CallbackState.AVAILABLE, mCellNetworkAgent);
+        fgCallback.expectCallback(CallbackState.AVAILABLE, mCellNetworkAgent);
+        assertTrue(isForegroundNetwork(mCellNetworkAgent));
+
+        mWiFiNetworkAgent = new MockNetworkAgent(TRANSPORT_WIFI);
+        mWiFiNetworkAgent.connect(true);
+
+        // When wifi connects, cell lingers.
+        callback.expectCallback(CallbackState.AVAILABLE, mWiFiNetworkAgent);
+        fgCallback.expectCallback(CallbackState.AVAILABLE, mWiFiNetworkAgent);
+        callback.expectCallback(CallbackState.LOSING, mCellNetworkAgent);
+        fgCallback.expectCallback(CallbackState.LOSING, mCellNetworkAgent);
+        assertTrue(isForegroundNetwork(mCellNetworkAgent));
+        assertTrue(isForegroundNetwork(mWiFiNetworkAgent));
+
+        // When lingering is complete, cell is still there but is now in the background.
+        fgCallback.expectCallback(CallbackState.LOST, mCellNetworkAgent, TEST_LINGER_DELAY_MS);
+        callback.assertNoCallback();
+        assertFalse(isForegroundNetwork(mCellNetworkAgent));
+        assertTrue(isForegroundNetwork(mWiFiNetworkAgent));
+
+        // File a cell request and check that cell comes into the foreground.
+        final NetworkRequest cellRequest = new NetworkRequest.Builder()
+                .addTransportType(TRANSPORT_CELLULAR).build();
+        final TestNetworkCallback cellCallback = new TestNetworkCallback();
+        mCm.requestNetwork(cellRequest, cellCallback);
+        cellCallback.expectCallback(CallbackState.AVAILABLE, mCellNetworkAgent);
+        fgCallback.expectCallback(CallbackState.AVAILABLE, mCellNetworkAgent);
+        callback.assertNoCallback();  // Because the network is already up.
+        assertTrue(isForegroundNetwork(mCellNetworkAgent));
+        assertTrue(isForegroundNetwork(mWiFiNetworkAgent));
+
+        // Release the request. The network immediately goes into the background, since it was not
+        // lingering.
+        mCm.unregisterNetworkCallback(cellCallback);
+        fgCallback.expectCallback(CallbackState.LOST, mCellNetworkAgent);
+        callback.assertNoCallback();
+        assertFalse(isForegroundNetwork(mCellNetworkAgent));
+        assertTrue(isForegroundNetwork(mWiFiNetworkAgent));
+
+        // Disconnect wifi and check that cell is foreground again.
+        mWiFiNetworkAgent.disconnect();
+        callback.expectCallback(CallbackState.LOST, mWiFiNetworkAgent);
+        fgCallback.expectCallback(CallbackState.LOST, mWiFiNetworkAgent);
+        fgCallback.expectCallback(CallbackState.AVAILABLE, mCellNetworkAgent);
+        assertTrue(isForegroundNetwork(mCellNetworkAgent));
+
+        mCm.unregisterNetworkCallback(callback);
+        mCm.unregisterNetworkCallback(fgCallback);
+    }
+
     @SmallTest
     public void testRequestBenchmark() throws Exception {
         // Benchmarks connecting and switching performance in the presence of a large number of
@@ -1948,8 +2028,7 @@
 
         // Turn on mobile data always on. The factory starts looking again.
         testFactory.expectAddRequests(1);
-        Settings.Global.putInt(cr, Settings.Global.MOBILE_DATA_ALWAYS_ON, 1);
-        mService.updateMobileDataAlwaysOn();
+        setMobileDataAlwaysOn(true);
         testFactory.waitForNetworkRequests(2);
         assertTrue(testFactory.getMyStartRequested());
 
@@ -1969,8 +2048,7 @@
 
         // Turn off mobile data always on and expect the request to disappear...
         testFactory.expectRemoveRequests(1);
-        Settings.Global.putInt(cr, Settings.Global.MOBILE_DATA_ALWAYS_ON, 0);
-        mService.updateMobileDataAlwaysOn();
+        setMobileDataAlwaysOn(false);
         testFactory.waitForNetworkRequests(1);
 
         // ...  and cell data to be torn down.
diff --git a/services/tests/servicestests/src/com/android/server/connectivity/IpConnectivityEventBuilderTest.java b/services/tests/servicestests/src/com/android/server/connectivity/IpConnectivityEventBuilderTest.java
new file mode 100644
index 0000000..aed3635
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/connectivity/IpConnectivityEventBuilderTest.java
@@ -0,0 +1,359 @@
+/*
+ * Copyright (C) 2016 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.connectivity;
+
+import android.net.ConnectivityMetricsEvent;
+import android.net.metrics.ApfProgramEvent;
+import android.net.metrics.ApfStats;
+import android.net.metrics.DefaultNetworkEvent;
+import android.net.metrics.DhcpClientEvent;
+import android.net.metrics.DhcpErrorEvent;
+import android.net.metrics.DnsEvent;
+import android.net.metrics.IpManagerEvent;
+import android.net.metrics.IpReachabilityEvent;
+import android.net.metrics.NetworkEvent;
+import android.net.metrics.RaEvent;
+import android.net.metrics.ValidationProbeEvent;
+import com.google.protobuf.nano.MessageNano;
+import java.util.Arrays;
+import junit.framework.TestCase;
+
+import static com.android.server.connectivity.metrics.IpConnectivityLogClass.IpConnectivityLog;
+import static com.android.server.connectivity.MetricsTestUtil.aBool;
+import static com.android.server.connectivity.MetricsTestUtil.aByteArray;
+import static com.android.server.connectivity.MetricsTestUtil.aLong;
+import static com.android.server.connectivity.MetricsTestUtil.aString;
+import static com.android.server.connectivity.MetricsTestUtil.aType;
+import static com.android.server.connectivity.MetricsTestUtil.anInt;
+import static com.android.server.connectivity.MetricsTestUtil.anIntArray;
+import static com.android.server.connectivity.MetricsTestUtil.b;
+import static com.android.server.connectivity.MetricsTestUtil.describeIpEvent;
+import static com.android.server.connectivity.MetricsTestUtil.ipEv;
+
+public class IpConnectivityEventBuilderTest extends TestCase {
+
+    public void testDefaultNetworkEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(DefaultNetworkEvent.class),
+                anInt(102),
+                anIntArray(1, 2, 3),
+                anInt(101),
+                aBool(true),
+                aBool(false));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  default_network_event <",
+                "    network_id <",
+                "      network_id: 102",
+                "    >",
+                "    previous_network_id <",
+                "      network_id: 101",
+                "    >",
+                "    previous_network_ip_support: 1",
+                "    transport_types: 1",
+                "    transport_types: 2",
+                "    transport_types: 3",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testDhcpClientEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(DhcpClientEvent.class),
+                aString("wlan0"),
+                aString("SomeState"),
+                anInt(192));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  dhcp_event <",
+                "    duration_ms: 192",
+                "    error_code: 0",
+                "    if_name: \"wlan0\"",
+                "    state_transition: \"SomeState\"",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testDhcpErrorEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(DhcpErrorEvent.class),
+                aString("wlan0"),
+                anInt(DhcpErrorEvent.L4_NOT_UDP));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  dhcp_event <",
+                "    duration_ms: 0",
+                "    error_code: 50397184",
+                "    if_name: \"wlan0\"",
+                "    state_transition: \"\"",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testDnsEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(DnsEvent.class),
+                anInt(101),
+                aByteArray(b(1), b(1), b(2), b(1), b(1), b(1), b(2), b(2)),
+                aByteArray(b(0), b(0), b(22), b(3), b(1), b(0), b(200), b(178)),
+                anIntArray(3456, 267, 1230, 45, 2111, 450, 638, 1300));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  dns_lookup_batch <",
+                "    event_types: 1",
+                "    event_types: 1",
+                "    event_types: 2",
+                "    event_types: 1",
+                "    event_types: 1",
+                "    event_types: 1",
+                "    event_types: 2",
+                "    event_types: 2",
+                "    latencies_ms: 3456",
+                "    latencies_ms: 267",
+                "    latencies_ms: 1230",
+                "    latencies_ms: 45",
+                "    latencies_ms: 2111",
+                "    latencies_ms: 450",
+                "    latencies_ms: 638",
+                "    latencies_ms: 1300",
+                "    network_id <",
+                "      network_id: 101",
+                "    >",
+                "    return_codes: 0",
+                "    return_codes: 0",
+                "    return_codes: 22",
+                "    return_codes: 3",
+                "    return_codes: 1",
+                "    return_codes: 0",
+                "    return_codes: 200",
+                "    return_codes: 178",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testIpManagerEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(IpManagerEvent.class),
+                aString("wlan0"),
+                anInt(IpManagerEvent.PROVISIONING_OK),
+                aLong(5678));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  ip_provisioning_event <",
+                "    event_type: 1",
+                "    if_name: \"wlan0\"",
+                "    latency_ms: 5678",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testIpReachabilityEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(IpReachabilityEvent.class),
+                aString("wlan0"),
+                anInt(IpReachabilityEvent.NUD_FAILED));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  ip_reachability_event <",
+                "    event_type: 512",
+                "    if_name: \"wlan0\"",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testNetworkEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(NetworkEvent.class),
+                anInt(100),
+                anInt(5),
+                aLong(20410));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  network_event <",
+                "    event_type: 5",
+                "    latency_ms: 20410",
+                "    network_id <",
+                "      network_id: 100",
+                "    >",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testValidationProbeEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(ValidationProbeEvent.class),
+                anInt(120),
+                aLong(40730),
+                anInt(ValidationProbeEvent.PROBE_HTTP),
+                anInt(204));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  time_ms: 1",
+                "  validation_probe_event <",
+                "    latency_ms: 40730",
+                "    network_id <",
+                "      network_id: 120",
+                "    >",
+                "    probe_result: 204",
+                "    probe_type: 1",
+                "  >",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testApfProgramEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(ApfProgramEvent.class),
+                aLong(200),
+                anInt(7),
+                anInt(9),
+                anInt(2048),
+                anInt(3));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  apf_program_event <",
+                "    current_ras: 9",
+                "    drop_multicast: true",
+                "    filtered_ras: 7",
+                "    has_ipv4_addr: true",
+                "    lifetime: 200",
+                "    program_length: 2048",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testApfStatsSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(ApfStats.class),
+                aLong(45000),
+                anInt(10),
+                anInt(2),
+                anInt(2),
+                anInt(1),
+                anInt(2),
+                anInt(4),
+                anInt(2048));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  apf_statistics <",
+                "    dropped_ras: 2",
+                "    duration_ms: 45000",
+                "    matching_ras: 2",
+                "    max_program_size: 2048",
+                "    parse_errors: 2",
+                "    program_updates: 4",
+                "    received_ras: 10",
+                "    zero_lifetime_ras: 1",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    public void testRaEventSerialization() {
+        ConnectivityMetricsEvent ev = describeIpEvent(
+                aType(RaEvent.class),
+                aLong(2000),
+                aLong(400),
+                aLong(300),
+                aLong(-1),
+                aLong(1000),
+                aLong(-1));
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  ra_event <",
+                "    dnssl_lifetime: -1",
+                "    prefix_preferred_lifetime: 300",
+                "    prefix_valid_lifetime: 400",
+                "    rdnss_lifetime: 1000",
+                "    route_info_lifetime: -1",
+                "    router_lifetime: 2000",
+                "  >",
+                "  time_ms: 1",
+                ">");
+
+        verifySerialization(want, ev);
+    }
+
+    static void verifySerialization(String want, ConnectivityMetricsEvent... input) {
+        try {
+            byte[] got = IpConnectivityEventBuilder.serialize(0, Arrays.asList(input));
+            IpConnectivityLog log = new IpConnectivityLog();
+            MessageNano.mergeFrom(log, got);
+            assertEquals(want, log.toString());
+        } catch (Exception e) {
+            fail(e.toString());
+        }
+    }
+
+    static String joinLines(String ... elems) {
+        StringBuilder b = new StringBuilder();
+        for (String s : elems) {
+            b.append(s);
+            b.append("\n");
+        }
+        return b.toString();
+    }
+}
diff --git a/services/tests/servicestests/src/com/android/server/connectivity/IpConnectivityMetricsTest.java b/services/tests/servicestests/src/com/android/server/connectivity/IpConnectivityMetricsTest.java
new file mode 100644
index 0000000..3fc89b9
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/connectivity/IpConnectivityMetricsTest.java
@@ -0,0 +1,269 @@
+/*
+ * Copyright (C) 2016, 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.connectivity;
+
+import android.content.Context;
+import android.net.ConnectivityMetricsEvent;
+import android.net.IIpConnectivityMetrics;
+import android.net.metrics.ApfStats;
+import android.net.metrics.DefaultNetworkEvent;
+import android.net.metrics.DhcpClientEvent;
+import android.net.metrics.IpConnectivityLog;
+import android.net.metrics.IpManagerEvent;
+import android.net.metrics.IpReachabilityEvent;
+import android.net.metrics.RaEvent;
+import android.net.metrics.ValidationProbeEvent;
+import android.os.Parcelable;
+import android.util.Base64;
+import com.android.server.connectivity.metrics.IpConnectivityLogClass;
+import com.google.protobuf.nano.MessageNano;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.List;
+import junit.framework.TestCase;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import static org.mockito.Mockito.timeout;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+public class IpConnectivityMetricsTest extends TestCase {
+    static final IpReachabilityEvent FAKE_EV =
+            new IpReachabilityEvent("wlan0", IpReachabilityEvent.NUD_FAILED);
+
+    @Mock Context mCtx;
+    @Mock IIpConnectivityMetrics mMockService;
+
+    IpConnectivityMetrics mService;
+
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mService = new IpConnectivityMetrics(mCtx);
+    }
+
+    public void testLoggingEvents() throws Exception {
+        IpConnectivityLog logger = new IpConnectivityLog(mMockService);
+
+        assertTrue(logger.log(1, FAKE_EV));
+        assertTrue(logger.log(2, FAKE_EV));
+        assertTrue(logger.log(3, FAKE_EV));
+
+        List<ConnectivityMetricsEvent> got = verifyEvents(3);
+        assertEventsEqual(expectedEvent(1), got.get(0));
+        assertEventsEqual(expectedEvent(2), got.get(1));
+        assertEventsEqual(expectedEvent(3), got.get(2));
+    }
+
+    public void testLoggingEventsWithMultipleCallers() throws Exception {
+        IpConnectivityLog logger = new IpConnectivityLog(mMockService);
+
+        final int nCallers = 10;
+        final int nEvents = 10;
+        for (int n = 0; n < nCallers; n++) {
+            final int i = n;
+            new Thread() {
+                public void run() {
+                    for (int j = 0; j < nEvents; j++) {
+                        assertTrue(logger.log(i * 100 + j, FAKE_EV));
+                    }
+                }
+            }.start();
+        }
+
+        List<ConnectivityMetricsEvent> got = verifyEvents(nCallers * nEvents, 100);
+        Collections.sort(got, EVENT_COMPARATOR);
+        Iterator<ConnectivityMetricsEvent> iter = got.iterator();
+        for (int i = 0; i < nCallers; i++) {
+            for (int j = 0; j < nEvents; j++) {
+                int expectedTimestamp = i * 100 + j;
+                assertEventsEqual(expectedEvent(expectedTimestamp), iter.next());
+            }
+        }
+    }
+
+    public void testBufferFlushing() {
+        String output1 = getdump("flush");
+        assertEquals("", output1);
+
+        new IpConnectivityLog(mService.impl).log(1, FAKE_EV);
+        String output2 = getdump("flush");
+        assertFalse("".equals(output2));
+
+        String output3 = getdump("flush");
+        assertEquals("", output3);
+    }
+
+    public void testEndToEndLogging() {
+        IpConnectivityLog logger = new IpConnectivityLog(mService.impl);
+
+        Parcelable[] events = {
+            new IpReachabilityEvent("wlan0", IpReachabilityEvent.NUD_FAILED),
+            new DhcpClientEvent("wlan0", "SomeState", 192),
+            new DefaultNetworkEvent(102, new int[]{1,2,3}, 101, true, false),
+            new IpManagerEvent("wlan0", IpManagerEvent.PROVISIONING_OK, 5678),
+            new ValidationProbeEvent(120, 40730, ValidationProbeEvent.PROBE_HTTP, 204),
+            new ApfStats(45000, 10, 2, 2, 1, 2, 4, 2048),
+            new RaEvent(2000, 400, 300, -1, 1000, -1)
+        };
+
+        for (int i = 0; i < events.length; i++) {
+            logger.log(100 * (i + 1), events[i]);
+        }
+
+        String want = joinLines(
+                "dropped_events: 0",
+                "events <",
+                "  ip_reachability_event <",
+                "    event_type: 512",
+                "    if_name: \"wlan0\"",
+                "  >",
+                "  time_ms: 100",
+                ">",
+                "events <",
+                "  dhcp_event <",
+                "    duration_ms: 192",
+                "    error_code: 0",
+                "    if_name: \"wlan0\"",
+                "    state_transition: \"SomeState\"",
+                "  >",
+                "  time_ms: 200",
+                ">",
+                "events <",
+                "  default_network_event <",
+                "    network_id <",
+                "      network_id: 102",
+                "    >",
+                "    previous_network_id <",
+                "      network_id: 101",
+                "    >",
+                "    previous_network_ip_support: 1",
+                "    transport_types: 1",
+                "    transport_types: 2",
+                "    transport_types: 3",
+                "  >",
+                "  time_ms: 300",
+                ">",
+                "events <",
+                "  ip_provisioning_event <",
+                "    event_type: 1",
+                "    if_name: \"wlan0\"",
+                "    latency_ms: 5678",
+                "  >",
+                "  time_ms: 400",
+                ">",
+                "events <",
+                "  time_ms: 500",
+                "  validation_probe_event <",
+                "    latency_ms: 40730",
+                "    network_id <",
+                "      network_id: 120",
+                "    >",
+                "    probe_result: 204",
+                "    probe_type: 1",
+                "  >",
+                ">",
+                "events <",
+                "  apf_statistics <",
+                "    dropped_ras: 2",
+                "    duration_ms: 45000",
+                "    matching_ras: 2",
+                "    max_program_size: 2048",
+                "    parse_errors: 2",
+                "    program_updates: 4",
+                "    received_ras: 10",
+                "    zero_lifetime_ras: 1",
+                "  >",
+                "  time_ms: 600",
+                ">",
+                "events <",
+                "  ra_event <",
+                "    dnssl_lifetime: -1",
+                "    prefix_preferred_lifetime: 300",
+                "    prefix_valid_lifetime: 400",
+                "    rdnss_lifetime: 1000",
+                "    route_info_lifetime: -1",
+                "    router_lifetime: 2000",
+                "  >",
+                "  time_ms: 700",
+                ">");
+
+        verifySerialization(want, getdump("flush"));
+    }
+
+    String getdump(String ... command) {
+        StringWriter buffer = new StringWriter();
+        PrintWriter writer = new PrintWriter(buffer);
+        mService.impl.dump(null, writer, command);
+        return buffer.toString();
+    }
+
+    List<ConnectivityMetricsEvent> verifyEvents(int n, int timeoutMs) throws Exception {
+        ArgumentCaptor<ConnectivityMetricsEvent> captor =
+                ArgumentCaptor.forClass(ConnectivityMetricsEvent.class);
+        verify(mMockService, timeout(timeoutMs).times(n)).logEvent(captor.capture());
+        return captor.getAllValues();
+    }
+
+    List<ConnectivityMetricsEvent> verifyEvents(int n) throws Exception {
+        return verifyEvents(n, 10);
+    }
+
+    static void verifySerialization(String want, String output) {
+        try {
+            byte[] got = Base64.decode(output, Base64.DEFAULT);
+            IpConnectivityLogClass.IpConnectivityLog log =
+                    new IpConnectivityLogClass.IpConnectivityLog();
+            MessageNano.mergeFrom(log, got);
+            assertEquals(want, log.toString());
+        } catch (Exception e) {
+            fail(e.toString());
+        }
+    }
+
+    static String joinLines(String ... elems) {
+        StringBuilder b = new StringBuilder();
+        for (String s : elems) {
+            b.append(s).append("\n");
+        }
+        return b.toString();
+    }
+
+    static ConnectivityMetricsEvent expectedEvent(int timestamp) {
+        return new ConnectivityMetricsEvent((long)timestamp, 0, 0, FAKE_EV);
+    }
+
+    /** Outer equality for ConnectivityMetricsEvent to avoid overriding equals() and hashCode(). */
+    static void assertEventsEqual(ConnectivityMetricsEvent expected, ConnectivityMetricsEvent got) {
+        assertEquals(expected.timestamp, got.timestamp);
+        assertEquals(expected.componentTag, got.componentTag);
+        assertEquals(expected.eventTag, got.eventTag);
+        assertEquals(expected.data, got.data);
+    }
+
+    static final Comparator<ConnectivityMetricsEvent> EVENT_COMPARATOR =
+        new Comparator<ConnectivityMetricsEvent>() {
+            @Override
+            public int compare(ConnectivityMetricsEvent ev1, ConnectivityMetricsEvent ev2) {
+                return (int) (ev1.timestamp - ev2.timestamp);
+            }
+        };
+}
diff --git a/services/tests/servicestests/src/com/android/server/connectivity/MetricsTestUtil.java b/services/tests/servicestests/src/com/android/server/connectivity/MetricsTestUtil.java
new file mode 100644
index 0000000..e201012
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/connectivity/MetricsTestUtil.java
@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2016 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.connectivity;
+
+import android.net.ConnectivityMetricsEvent;
+import android.net.ConnectivityMetricsLogger;
+import android.os.Bundle;
+import android.os.Parcel;
+import android.os.Parcelable;
+
+abstract public class MetricsTestUtil {
+    private MetricsTestUtil() {
+    }
+
+    static ConnectivityMetricsEvent ipEv(Parcelable p) {
+        return ev(ConnectivityMetricsLogger.COMPONENT_TAG_CONNECTIVITY, p);
+    }
+
+    static ConnectivityMetricsEvent telephonyEv() {
+        return ev(ConnectivityMetricsLogger.COMPONENT_TAG_TELEPHONY, new Bundle());
+    }
+
+    static ConnectivityMetricsEvent ev(int tag, Parcelable p) {
+        return new ConnectivityMetricsEvent(1L, tag, 0, p);
+    }
+
+    // Utiliy interface for describing the content of a Parcel. This relies on
+    // the implementation defails of Parcelable and on the fact that the fully
+    // qualified Parcelable class names are written as string in the Parcels.
+    interface ParcelField {
+        void write(Parcel p);
+    }
+
+    static ConnectivityMetricsEvent describeIpEvent(ParcelField... fs) {
+        Parcel p = Parcel.obtain();
+        for (ParcelField f : fs) {
+            f.write(p);
+        }
+        p.setDataPosition(0);
+        return ipEv(p.readParcelable(ClassLoader.getSystemClassLoader()));
+    }
+
+    static ParcelField aType(Class<?> c) {
+        return new ParcelField() {
+            public void write(Parcel p) {
+                p.writeString(c.getName());
+            }
+        };
+    }
+
+    static ParcelField aBool(boolean b) {
+        return aByte((byte) (b ? 1 : 0));
+    }
+
+    static ParcelField aByte(byte b) {
+        return new ParcelField() {
+            public void write(Parcel p) {
+                p.writeByte(b);
+            }
+        };
+    }
+
+    static ParcelField anInt(int i) {
+        return new ParcelField() {
+            public void write(Parcel p) {
+                p.writeInt(i);
+            }
+        };
+    }
+
+    static ParcelField aLong(long l) {
+        return new ParcelField() {
+            public void write(Parcel p) {
+                p.writeLong(l);
+            }
+        };
+    }
+
+    static ParcelField aString(String s) {
+        return new ParcelField() {
+            public void write(Parcel p) {
+                p.writeString(s);
+            }
+        };
+    }
+
+    static ParcelField aByteArray(byte... ary) {
+        return new ParcelField() {
+            public void write(Parcel p) {
+                p.writeByteArray(ary);
+            }
+        };
+    }
+
+    static ParcelField anIntArray(int... ary) {
+        return new ParcelField() {
+            public void write(Parcel p) {
+                p.writeIntArray(ary);
+            }
+        };
+    }
+
+    static byte b(int i) {
+        return (byte) i;
+    }
+}