Immediately create native networks when NetworkAgents register.

Currently, native networks for non-VPN networks are created only
when the NetworkAgent goes into the CONNECTED state. This is not
ideal, because until the network is connected:

- Nothing routes to the network, so no IP packets can be sent on
  it (except via packet sockets).
- Many network configuration changes (e.g., routes and DNS
  servers) fail to apply because the network does not exist yet.
  These cause ENONET errors in the logs.

Fix this starting in U by creating the native network as soon as
the agent registers. This should not impact apps because
NetworkCallbacks are not sent until networks are connected.

Bug: 143158421
Test: new coverage in NetworkAgentTest
Change-Id: I26bfa8630c085422175558645c47a6c64be96ae6

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

@@ -2597,7 +2597,8 @@ public class ConnectivityService extends IConnectivityManager.Stub
         final ArrayList<NetworkStateSnapshot> result = new ArrayList<>();
         for (Network network : getAllNetworks()) {
             final NetworkAgentInfo nai = getNetworkAgentInfoForNetwork(network);
-            if (nai != null && nai.everConnected()) {
+            final boolean includeNetwork = (nai != null) && nai.isCreated();
+            if (includeNetwork) {
                 // TODO (b/73321673) : NetworkStateSnapshot contains a copy of the
                 // NetworkCapabilities, which may contain UIDs of apps to which the
                 // network applies. Should the UIDs be cleared so as not to leak or
@@ -3799,9 +3800,9 @@ public class ConnectivityService extends IConnectivityManager.Stub
                     break;
                 }
                 case NetworkAgent.EVENT_UNREGISTER_AFTER_REPLACEMENT: {
-                    if (!nai.isCreated()) {
+                    if (!nai.everConnected()) {
-                        Log.d(TAG, "unregisterAfterReplacement on uncreated " + nai.toShortString()
+                        Log.d(TAG, "unregisterAfterReplacement on never-connected "
-                                + ", tearing down instead");
+                                + nai.toShortString() + ", tearing down instead");
                         teardownUnneededNetwork(nai);
                         break;
                     }
@@ -4386,6 +4387,25 @@ public class ConnectivityService extends IConnectivityManager.Stub
         }
     }
 
+    @VisibleForTesting
+    protected static boolean shouldCreateNetworksImmediately() {
+        // Before U, physical networks are only created when the agent advances to CONNECTED.
+        // In U and above, all networks are immediately created when the agent is registered.
+        return SdkLevel.isAtLeastU();
+    }
+
+    private static boolean shouldCreateNativeNetwork(@NonNull NetworkAgentInfo nai,
+            @NonNull NetworkInfo.State state) {
+        if (nai.isCreated()) return false;
+        if (state == NetworkInfo.State.CONNECTED) return true;
+        if (state != NetworkInfo.State.CONNECTING) {
+            // TODO: throw if no WTFs are observed in the field.
+            Log.wtf(TAG, "Uncreated network in invalid state: " + state);
+            return false;
+        }
+        return nai.isVPN() || shouldCreateNetworksImmediately();
+    }
+
     private static boolean shouldDestroyNativeNetwork(@NonNull NetworkAgentInfo nai) {
         return nai.isCreated() && !nai.isDestroyed();
     }
@@ -7823,7 +7843,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
 
         if (isDefaultNetwork(networkAgent)) {
             handleApplyDefaultProxy(newLp.getHttpProxy());
-        } else {
+        } else if (networkAgent.everConnected()) {
             updateProxy(newLp, oldLp);
         }
 
@@ -7857,6 +7877,10 @@ public class ConnectivityService extends IConnectivityManager.Stub
         mKeepaliveTracker.handleCheckKeepalivesStillValid(networkAgent);
     }
 
+    private void applyInitialLinkProperties(@NonNull NetworkAgentInfo nai) {
+        updateLinkProperties(nai, new LinkProperties(nai.linkProperties), null);
+    }
+
     /**
      * @param naData captive portal data from NetworkAgent
      * @param apiData captive portal data from capport API
@@ -9608,21 +9632,32 @@ public class ConnectivityService extends IConnectivityManager.Stub
                     + oldInfo.getState() + " to " + state);
         }
 
-        if (!networkAgent.isCreated()
+        if (shouldCreateNativeNetwork(networkAgent, state)) {
-                && (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);
 
             if (!createNativeNetwork(networkAgent)) return;
+
+            networkAgent.setCreated();
+
+            // If the network is created immediately on register, then apply the LinkProperties now.
+            // Otherwise, this is done further down when the network goes into connected state.
+            // Applying the LinkProperties means that the network is ready to carry traffic -
+            // interfaces and routing rules have been added, DNS servers programmed, etc.
+            // For VPNs, this must be done before the capabilities are updated, because as soon as
+            // that happens, UIDs are routed to the network.
+            if (shouldCreateNetworksImmediately()) {
+                applyInitialLinkProperties(networkAgent);
+            }
+
+            // TODO: should this move earlier? It doesn't seem to have anything to do with whether
+            // a network is created or not.
             if (networkAgent.propagateUnderlyingCapabilities()) {
                 // Initialize the network's capabilities to their starting values according to the
                 // underlying networks. This ensures that the capabilities are correct before
                 // anything happens to the network.
                 updateCapabilitiesForNetwork(networkAgent);
             }
-            networkAgent.setCreated();
             networkAgent.onNetworkCreated();
             updateAllowedUids(networkAgent, null, networkAgent.networkCapabilities);
             updateProfileAllowedNetworks();
@@ -9636,8 +9671,19 @@ public class ConnectivityService extends IConnectivityManager.Stub
             networkAgent.getAndSetNetworkCapabilities(networkAgent.networkCapabilities);
 
             handlePerNetworkPrivateDnsConfig(networkAgent, mDnsManager.getPrivateDnsConfig());
-            updateLinkProperties(networkAgent, new LinkProperties(networkAgent.linkProperties),
+            if (!shouldCreateNetworksImmediately()) {
-                    null);
+                applyInitialLinkProperties(networkAgent);
+            } else {
+                // The network was created when the agent registered, and the LinkProperties are
+                // already up-to-date. However, updateLinkProperties also makes some changes only
+                // when the network connects. Apply those changes here. On T and below these are
+                // handled by the applyInitialLinkProperties call just above.
+                // TODO: stop relying on updateLinkProperties(..., null) to do this.
+                // If something depends on both LinkProperties and connected state, it should be in
+                // this method as well.
+                networkAgent.clatd.update();
+                updateProxy(networkAgent.linkProperties, null);
+            }
 
             // If a rate limit has been configured and is applicable to this network (network
             // provides internet connectivity), apply it. The tc police filter cannot be attached

tests/cts/net/src/android/net/cts/NetworkAgentTest.kt

@@ -29,9 +29,9 @@ import android.net.LinkProperties
 import android.net.NattKeepalivePacketData
 import android.net.Network
 import android.net.NetworkAgent
-import android.net.NetworkAgentConfig
 import android.net.NetworkAgent.INVALID_NETWORK
 import android.net.NetworkAgent.VALID_NETWORK
+import android.net.NetworkAgentConfig
 import android.net.NetworkCapabilities
 import android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET
 import android.net.NetworkCapabilities.NET_CAPABILITY_NOT_CONGESTED
@@ -46,21 +46,23 @@ import android.net.NetworkCapabilities.NET_CAPABILITY_TRUSTED
 import android.net.NetworkCapabilities.NET_CAPABILITY_VALIDATED
 import android.net.NetworkCapabilities.TRANSPORT_CELLULAR
 import android.net.NetworkCapabilities.TRANSPORT_TEST
-import android.net.NetworkCapabilities.TRANSPORT_WIFI
 import android.net.NetworkCapabilities.TRANSPORT_VPN
+import android.net.NetworkCapabilities.TRANSPORT_WIFI
 import android.net.NetworkInfo
 import android.net.NetworkProvider
 import android.net.NetworkReleasedException
 import android.net.NetworkRequest
 import android.net.NetworkScore
-import android.net.RouteInfo
 import android.net.QosCallback
-import android.net.QosCallbackException
 import android.net.QosCallback.QosCallbackRegistrationException
+import android.net.QosCallbackException
 import android.net.QosSession
 import android.net.QosSessionAttributes
 import android.net.QosSocketInfo
+import android.net.RouteInfo
 import android.net.SocketKeepalive
+import android.net.TestNetworkInterface
+import android.net.TestNetworkManager
 import android.net.Uri
 import android.net.VpnManager
 import android.net.VpnTransportInfo
@@ -71,6 +73,7 @@ import android.os.Build
 import android.os.Handler
 import android.os.HandlerThread
 import android.os.Message
+import android.os.Process
 import android.os.SystemClock
 import android.platform.test.annotations.AppModeFull
 import android.system.OsConstants.IPPROTO_TCP
@@ -89,6 +92,7 @@ import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo
 import com.android.testutils.DevSdkIgnoreRunner
 import com.android.testutils.RecorderCallback.CallbackEntry.Available
 import com.android.testutils.RecorderCallback.CallbackEntry.BlockedStatus
+import com.android.testutils.RecorderCallback.CallbackEntry.CapabilitiesChanged
 import com.android.testutils.RecorderCallback.CallbackEntry.LinkPropertiesChanged
 import com.android.testutils.RecorderCallback.CallbackEntry.Losing
 import com.android.testutils.RecorderCallback.CallbackEntry.Lost
@@ -178,6 +182,7 @@ class NetworkAgentTest {
     private val agentsToCleanUp = mutableListOf<NetworkAgent>()
     private val callbacksToCleanUp = mutableListOf<TestableNetworkCallback>()
     private var qosTestSocket: Closeable? = null // either Socket or DatagramSocket
+    private val ifacesToCleanUp = mutableListOf<TestNetworkInterface>()
 
     @Before
     fun setUp() {
@@ -189,6 +194,7 @@ class NetworkAgentTest {
     fun tearDown() {
         agentsToCleanUp.forEach { it.unregister() }
         callbacksToCleanUp.forEach { mCM.unregisterNetworkCallback(it) }
+        ifacesToCleanUp.forEach { it.fileDescriptor.close() }
         qosTestSocket?.close()
         mHandlerThread.quitSafely()
         mHandlerThread.join()
@@ -269,7 +275,7 @@ class NetworkAgentTest {
         removeCapability(NET_CAPABILITY_INTERNET)
         addCapability(NET_CAPABILITY_NOT_SUSPENDED)
         addCapability(NET_CAPABILITY_NOT_ROAMING)
-        addCapability(NET_CAPABILITY_NOT_VPN)
+        if (!transports.contains(TRANSPORT_VPN)) addCapability(NET_CAPABILITY_NOT_VPN)
         if (SdkLevel.isAtLeastS()) {
             addCapability(NET_CAPABILITY_NOT_VCN_MANAGED)
         }
@@ -304,7 +310,7 @@ class NetworkAgentTest {
         context: Context = realContext,
         specifier: String? = UUID.randomUUID().toString(),
         initialConfig: NetworkAgentConfig? = null,
-        expectedInitSignalStrengthThresholds: IntArray? = intArrayOf(),
+        expectedInitSignalStrengthThresholds: IntArray = intArrayOf(),
         transports: IntArray = intArrayOf()
     ): Pair<TestableNetworkAgent, TestableNetworkCallback> {
         val callback = TestableNetworkCallback()
@@ -317,8 +323,7 @@ class NetworkAgentTest {
         agent.register()
         agent.markConnected()
         agent.expectCallback<OnNetworkCreated>()
-        agent.expectSignalStrengths(expectedInitSignalStrengthThresholds)
+        agent.expectPostConnectionCallbacks(expectedInitSignalStrengthThresholds)
-        agent.expectValidationBypassedStatus()
         callback.expectAvailableThenValidatedCallbacks(agent.network!!)
         return agent to callback
     }
@@ -336,6 +341,19 @@ class NetworkAgentTest {
         mFakeConnectivityService.connect(it.registerForTest(Network(FAKE_NET_ID)))
     }
 
+    private fun TestableNetworkAgent.expectPostConnectionCallbacks(
+        thresholds: IntArray = intArrayOf()
+    ) {
+        expectSignalStrengths(thresholds)
+        expectValidationBypassedStatus()
+        assertNoCallback()
+    }
+
+    private fun createTunInterface(): TestNetworkInterface = realContext.getSystemService(
+                TestNetworkManager::class.java)!!.createTunInterface(emptyList()).also {
+            ifacesToCleanUp.add(it)
+    }
+
     fun assertLinkPropertiesEventually(
         n: Network,
         description: String,
@@ -1291,8 +1309,12 @@ class NetworkAgentTest {
         requestNetwork(makeTestNetworkRequest(specifier = specifier6), callback)
         val agent6 = createNetworkAgent(specifier = specifier6)
         val network6 = agent6.register()
-        // No callbacks are sent, so check the LinkProperties to see if the network has connected.
+        if (SdkLevel.isAtLeastU()) {
-        assertLinkPropertiesEventuallyNotNull(agent6.network!!)
+            agent6.expectCallback<OnNetworkCreated>()
+        } else {
+            // No callbacks are sent, so check LinkProperties to wait for the network to be created.
+            assertLinkPropertiesEventuallyNotNull(agent6.network!!)
+        }
 
         // unregisterAfterReplacement tears down the network immediately.
         // Approximately check that this is the case by picking an unregister timeout that's longer
@@ -1301,8 +1323,9 @@ class NetworkAgentTest {
         val timeoutMs = agent6.DEFAULT_TIMEOUT_MS.toInt() + 1_000
         agent6.unregisterAfterReplacement(timeoutMs)
         agent6.expectCallback<OnNetworkUnwanted>()
-        if (!SdkLevel.isAtLeastT()) {
+        if (!SdkLevel.isAtLeastT() || SdkLevel.isAtLeastU()) {
             // Before T, onNetworkDestroyed is called even if the network was never created.
+            // On U+, the network was created by register(). Destroying it sends onNetworkDestroyed.
             agent6.expectCallback<OnNetworkDestroyed>()
         }
         // Poll for LinkProperties becoming null, because when onNetworkUnwanted is called, the
@@ -1375,4 +1398,101 @@ class NetworkAgentTest {
         callback.expect<Available>(agent.network!!)
         callback.eventuallyExpect<Lost> { it.network == agent.network }
     }
+
+    fun doTestNativeNetworkCreation(expectCreatedImmediately: Boolean, transports: IntArray) {
+        val iface = createTunInterface()
+        val ifName = iface.interfaceName
+        val nc = makeTestNetworkCapabilities(ifName, transports).also {
+            if (transports.contains(TRANSPORT_VPN)) {
+                val sessionId = "NetworkAgentTest-${Process.myPid()}"
+                it.transportInfo = VpnTransportInfo(VpnManager.TYPE_VPN_PLATFORM, sessionId,
+                    /*bypassable=*/ false, /*longLivedTcpConnectionsExpensive=*/ false)
+                it.underlyingNetworks = listOf()
+            }
+        }
+        val lp = LinkProperties().apply {
+            interfaceName = ifName
+            addLinkAddress(LinkAddress("2001:db8::1/64"))
+            addRoute(RouteInfo(IpPrefix("2001:db8::/64"), null /* nextHop */, ifName))
+            addRoute(RouteInfo(IpPrefix("::/0"),
+                    InetAddresses.parseNumericAddress("fe80::abcd"),
+                    ifName))
+        }
+
+        // File a request containing the agent's specifier to receive callbacks and to ensure that
+        // the agent is not torn down due to being unneeded.
+        val request = makeTestNetworkRequest(specifier = ifName)
+        val requestCallback = TestableNetworkCallback()
+        requestNetwork(request, requestCallback)
+
+        val listenCallback = TestableNetworkCallback()
+        registerNetworkCallback(request, listenCallback)
+
+        // Register the NetworkAgent...
+        val agent = createNetworkAgent(realContext, initialNc = nc, initialLp = lp)
+        val network = agent.register()
+
+        // ... and then change the NetworkCapabilities and LinkProperties.
+        nc.addCapability(NET_CAPABILITY_TEMPORARILY_NOT_METERED)
+        agent.sendNetworkCapabilities(nc)
+        lp.addLinkAddress(LinkAddress("192.0.2.2/25"))
+        lp.addRoute(RouteInfo(IpPrefix("192.0.2.0/25"), null /* nextHop */, ifName))
+        agent.sendLinkProperties(lp)
+
+        requestCallback.assertNoCallback()
+        listenCallback.assertNoCallback()
+        if (!expectCreatedImmediately) {
+            agent.assertNoCallback()
+            agent.markConnected()
+            agent.expectCallback<OnNetworkCreated>()
+        } else {
+            agent.expectCallback<OnNetworkCreated>()
+            agent.markConnected()
+        }
+        agent.expectPostConnectionCallbacks()
+
+        // onAvailable must be called only when the network connects, and no other callbacks may be
+        // called before that happens. The callbacks report the state of the network as it was when
+        // it connected, so they reflect the NC and LP changes made after registration.
+        requestCallback.expect<Available>(network)
+        listenCallback.expect<Available>(network)
+
+        requestCallback.expect<CapabilitiesChanged>(network) { it.caps.hasCapability(
+            NET_CAPABILITY_TEMPORARILY_NOT_METERED) }
+        listenCallback.expect<CapabilitiesChanged>(network) { it.caps.hasCapability(
+            NET_CAPABILITY_TEMPORARILY_NOT_METERED) }
+
+        requestCallback.expect<LinkPropertiesChanged>(network) { it.lp.equals(lp) }
+        listenCallback.expect<LinkPropertiesChanged>(network) { it.lp.equals(lp) }
+
+        requestCallback.expect<BlockedStatus>()
+        listenCallback.expect<BlockedStatus>()
+
+        // Except for network validation, ensure no more callbacks are sent.
+        requestCallback.expectCaps(network) {
+            it.hasCapability(NET_CAPABILITY_VALIDATED)
+        }
+        listenCallback.expectCaps(network) {
+            it.hasCapability(NET_CAPABILITY_VALIDATED)
+        }
+        unregister(agent)
+        // Lost implicitly checks that no further callbacks happened after connect.
+        requestCallback.expect<Lost>(network)
+        listenCallback.expect<Lost>(network)
+        assertNull(mCM.getLinkProperties(network))
+    }
+
+    @Test
+    fun testNativeNetworkCreation_PhysicalNetwork() {
+        // On T and below, the native network is only created when the agent connects.
+        // Starting in U, the native network is created as soon as the agent is registered.
+        doTestNativeNetworkCreation(expectCreatedImmediately = SdkLevel.isAtLeastU(),
+            intArrayOf(TRANSPORT_CELLULAR))
+    }
+
+    @Test
+    fun testNativeNetworkCreation_Vpn() {
+        // VPN networks are always created as soon as the agent is registered.
+        doTestNativeNetworkCreation(expectCreatedImmediately = true, intArrayOf(TRANSPORT_VPN))
+    }
 }

tests/unit/java/com/android/server/ConnectivityServiceTest.java

@@ -3783,6 +3783,12 @@ public class ConnectivityServiceTest {
 
         mWiFiAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI, callbacks);
 
+        if (mService.shouldCreateNetworksImmediately()) {
+            assertEquals("onNetworkCreated", eventOrder.poll(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+        } else {
+            assertNull(eventOrder.poll());
+        }
+
         // Connect a network, and file a request for it after it has come up, to ensure the nascent
         // timer is cleared and the test does not have to wait for it. Filing the request after the
         // network has come up is necessary because ConnectivityService does not appear to clear the
@@ -3790,7 +3796,12 @@ public class ConnectivityServiceTest {
         // connected.
         // TODO: fix this bug, file the request before connecting, and remove the waitForIdle.
         mWiFiAgent.connectWithoutInternet();
-        waitForIdle();
+        if (!mService.shouldCreateNetworksImmediately()) {
+            assertEquals("onNetworkCreated", eventOrder.poll(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+        } else {
+            waitForIdle();
+            assertNull(eventOrder.poll());
+        }
         mCm.requestNetwork(request, callback);
         callback.expectAvailableCallbacksUnvalidated(mWiFiAgent);
 
@@ -3807,7 +3818,6 @@ public class ConnectivityServiceTest {
 
         // Disconnect the network and check that events happened in the right order.
         mCm.unregisterNetworkCallback(callback);
-        assertEquals("onNetworkCreated", eventOrder.poll(TIMEOUT_MS, TimeUnit.MILLISECONDS));
         assertEquals("onNetworkUnwanted", eventOrder.poll(TIMEOUT_MS, TimeUnit.MILLISECONDS));
         assertEquals("timePasses", eventOrder.poll(TIMEOUT_MS, TimeUnit.MILLISECONDS));
         assertEquals("onNetworkDisconnected", eventOrder.poll(TIMEOUT_MS, TimeUnit.MILLISECONDS));
@@ -7593,7 +7603,9 @@ public class ConnectivityServiceTest {
         // Simple connection with initial LP should have updated ifaces.
         mCellAgent.connect(false);
         waitForIdle();
-        expectNotifyNetworkStatus(onlyCell(), onlyCell(), MOBILE_IFNAME);
+        List<Network> allNetworks = mService.shouldCreateNetworksImmediately()
+                ? cellAndWifi() : onlyCell();
+        expectNotifyNetworkStatus(allNetworks, onlyCell(), MOBILE_IFNAME);
         reset(mStatsManager);
 
         // Verify change fields other than interfaces does not trigger a notification to NSS.
@@ -7902,9 +7914,13 @@ public class ConnectivityServiceTest {
         setPrivateDnsSettings(PRIVATE_DNS_MODE_OPPORTUNISTIC, "ignored.example.com");
 
         mCellAgent = new TestNetworkAgentWrapper(TRANSPORT_CELLULAR);
+        final int netId = mCellAgent.getNetwork().netId;
         waitForIdle();
-        verify(mMockDnsResolver, never()).setResolverConfiguration(any());
+        if (mService.shouldCreateNetworksImmediately()) {
-        verifyNoMoreInteractions(mMockDnsResolver);
+            verify(mMockDnsResolver, times(1)).createNetworkCache(netId);
+        } else {
+            verify(mMockDnsResolver, never()).setResolverConfiguration(any());
+        }
 
         final LinkProperties cellLp = new LinkProperties();
         cellLp.setInterfaceName(MOBILE_IFNAME);
@@ -7920,10 +7936,13 @@ public class ConnectivityServiceTest {
         mCellAgent.sendLinkProperties(cellLp);
         mCellAgent.connect(false);
         waitForIdle();
-
+        if (!mService.shouldCreateNetworksImmediately()) {
-        verify(mMockDnsResolver, times(1)).createNetworkCache(eq(mCellAgent.getNetwork().netId));
+            // CS tells dnsresolver about the empty DNS config for this network.
-        // CS tells dnsresolver about the empty DNS config for this network.
+            verify(mMockDnsResolver, times(1)).createNetworkCache(netId);
+        }
         verify(mMockDnsResolver, atLeastOnce()).setResolverConfiguration(any());
+
+        verifyNoMoreInteractions(mMockDnsResolver);
         reset(mMockDnsResolver);
 
         cellLp.addDnsServer(InetAddress.getByName("2001:db8::1"));
@@ -8038,10 +8057,13 @@ public class ConnectivityServiceTest {
         mCm.requestNetwork(cellRequest, cellNetworkCallback);
 
         mCellAgent = new TestNetworkAgentWrapper(TRANSPORT_CELLULAR);
+        final int netId = mCellAgent.getNetwork().netId;
         waitForIdle();
-        // CS tells netd about the empty DNS config for this network.
+        if (mService.shouldCreateNetworksImmediately()) {
-        verify(mMockDnsResolver, never()).setResolverConfiguration(any());
+            verify(mMockDnsResolver, times(1)).createNetworkCache(netId);
-        verifyNoMoreInteractions(mMockDnsResolver);
+        } else {
+            verify(mMockDnsResolver, never()).setResolverConfiguration(any());
+        }
 
         final LinkProperties cellLp = new LinkProperties();
         cellLp.setInterfaceName(MOBILE_IFNAME);
@@ -8060,7 +8082,9 @@ public class ConnectivityServiceTest {
         mCellAgent.sendLinkProperties(cellLp);
         mCellAgent.connect(false);
         waitForIdle();
-        verify(mMockDnsResolver, times(1)).createNetworkCache(eq(mCellAgent.getNetwork().netId));
+        if (!mService.shouldCreateNetworksImmediately()) {
+            verify(mMockDnsResolver, times(1)).createNetworkCache(netId);
+        }
         verify(mMockDnsResolver, atLeastOnce()).setResolverConfiguration(
                 mResolverParamsParcelCaptor.capture());
         ResolverParamsParcel resolvrParams = mResolverParamsParcelCaptor.getValue();
@@ -8071,6 +8095,7 @@ public class ConnectivityServiceTest {
         assertEquals(2, resolvrParams.tlsServers.length);
         assertTrue(new ArraySet<>(resolvrParams.tlsServers).containsAll(
                 asList("2001:db8::1", "192.0.2.1")));
+        verifyNoMoreInteractions(mMockDnsResolver);
         reset(mMockDnsResolver);
         cellNetworkCallback.expect(AVAILABLE, mCellAgent);
         cellNetworkCallback.expect(NETWORK_CAPS_UPDATED, mCellAgent);
@@ -10388,7 +10413,8 @@ public class ConnectivityServiceTest {
         if (inOrder != null) {
             return inOrder.verify(t);
         } else {
-            return verify(t);
+            // times(1) for consistency with the above. InOrder#verify always implies times(1).
+            return verify(t, times(1));
         }
     }
 
@@ -10437,6 +10463,21 @@ public class ConnectivityServiceTest {
         }
     }
 
+    private void expectNativeNetworkCreated(int netId, int permission, String iface,
+            InOrder inOrder) throws Exception {
+        verifyWithOrder(inOrder, mMockNetd).networkCreate(nativeNetworkConfigPhysical(netId,
+                permission));
+        verifyWithOrder(inOrder, mMockDnsResolver).createNetworkCache(eq(netId));
+        if (iface != null) {
+            verifyWithOrder(inOrder, mMockNetd).networkAddInterface(netId, iface);
+        }
+    }
+
+    private void expectNativeNetworkCreated(int netId, int permission, String iface)
+            throws Exception {
+        expectNativeNetworkCreated(netId, permission, iface, null /* inOrder */);
+    }
+
     @Test
     public void testStackedLinkProperties() throws Exception {
         final LinkAddress myIpv4 = new LinkAddress("1.2.3.4/24");
@@ -10474,11 +10515,8 @@ public class ConnectivityServiceTest {
         int cellNetId = mCellAgent.getNetwork().netId;
         waitForIdle();
 
-        verify(mMockNetd, times(1)).networkCreate(nativeNetworkConfigPhysical(cellNetId,
+        expectNativeNetworkCreated(cellNetId, INetd.PERMISSION_NONE, MOBILE_IFNAME);
-                INetd.PERMISSION_NONE));
         assertRoutesAdded(cellNetId, ipv6Subnet, ipv6Default);
-        verify(mMockDnsResolver, times(1)).createNetworkCache(eq(cellNetId));
-        verify(mMockNetd, times(1)).networkAddInterface(cellNetId, MOBILE_IFNAME);
         final ArrayTrackRecord<ReportedInterfaces>.ReadHead readHead =
                 mDeps.mReportedInterfaceHistory.newReadHead();
         assertNotNull(readHead.poll(TIMEOUT_MS, ri -> ri.contentEquals(mServiceContext,
@@ -14993,7 +15031,7 @@ public class ConnectivityServiceTest {
             UserHandle testHandle,
             TestNetworkCallback profileDefaultNetworkCallback,
             TestNetworkCallback disAllowProfileDefaultNetworkCallback) throws Exception {
-        final InOrder inOrder = inOrder(mMockNetd);
+        final InOrder inOrder = inOrder(mMockNetd, mMockDnsResolver);
 
         mCellAgent = new TestNetworkAgentWrapper(TRANSPORT_CELLULAR);
         mCellAgent.connect(true);
@@ -15009,8 +15047,16 @@ public class ConnectivityServiceTest {
 
         final TestNetworkAgentWrapper workAgent =
                 makeEnterpriseNetworkAgent(profileNetworkPreference.getPreferenceEnterpriseId());
+        if (mService.shouldCreateNetworksImmediately()) {
+            expectNativeNetworkCreated(workAgent.getNetwork().netId, INetd.PERMISSION_SYSTEM,
+                    null /* iface */, inOrder);
+        }
         if (connectWorkProfileAgentAhead) {
             workAgent.connect(false);
+            if (!mService.shouldCreateNetworksImmediately()) {
+                expectNativeNetworkCreated(workAgent.getNetwork().netId, INetd.PERMISSION_SYSTEM,
+                        null /* iface */, inOrder);
+            }
         }
 
         final TestOnCompleteListener listener = new TestOnCompleteListener();
@@ -15050,6 +15096,11 @@ public class ConnectivityServiceTest {
 
         if (!connectWorkProfileAgentAhead) {
             workAgent.connect(false);
+            if (!mService.shouldCreateNetworksImmediately()) {
+                inOrder.verify(mMockNetd).networkCreate(
+                        nativeNetworkConfigPhysical(workAgent.getNetwork().netId,
+                                INetd.PERMISSION_SYSTEM));
+            }
         }
 
         profileDefaultNetworkCallback.expectAvailableCallbacksUnvalidated(workAgent);
@@ -15058,8 +15109,6 @@ public class ConnectivityServiceTest {
         }
         mSystemDefaultNetworkCallback.assertNoCallback();
         mDefaultNetworkCallback.assertNoCallback();
-        inOrder.verify(mMockNetd).networkCreate(
-                nativeNetworkConfigPhysical(workAgent.getNetwork().netId, INetd.PERMISSION_SYSTEM));
         inOrder.verify(mMockNetd).networkAddUidRangesParcel(new NativeUidRangeConfig(
                 workAgent.getNetwork().netId,
                 uidRangeFor(testHandle, profileNetworkPreference),
@@ -17578,6 +17627,22 @@ public class ConnectivityServiceTest {
         verify(mMockNetd, never()).interfaceSetMtu(eq(WIFI_IFNAME), anyInt());
     }
 
+    private void verifyMtuSetOnWifiInterfaceOnlyUpToT(int mtu) throws Exception {
+        if (!mService.shouldCreateNetworksImmediately()) {
+            verify(mMockNetd, times(1)).interfaceSetMtu(WIFI_IFNAME, mtu);
+        } else {
+            verify(mMockNetd, never()).interfaceSetMtu(eq(WIFI_IFNAME), anyInt());
+        }
+    }
+
+    private void verifyMtuSetOnWifiInterfaceOnlyStartingFromU(int mtu) throws Exception {
+        if (mService.shouldCreateNetworksImmediately()) {
+            verify(mMockNetd, times(1)).interfaceSetMtu(WIFI_IFNAME, mtu);
+        } else {
+            verify(mMockNetd, never()).interfaceSetMtu(eq(WIFI_IFNAME), anyInt());
+        }
+    }
+
     @Test
     public void testSendLinkPropertiesSetInterfaceMtuBeforeConnect() throws Exception {
         final int mtu = 1281;
@@ -17592,8 +17657,8 @@ public class ConnectivityServiceTest {
         reset(mMockNetd);
 
         mWiFiAgent.connect(false /* validated */);
-        // The MTU is always (re-)applied when the network connects.
+        // Before U, the MTU is always (re-)applied when the network connects.
-        verifyMtuSetOnWifiInterface(mtu);
+        verifyMtuSetOnWifiInterfaceOnlyUpToT(mtu);
     }
 
     @Test
@@ -17603,13 +17668,13 @@ public class ConnectivityServiceTest {
         lp.setInterfaceName(WIFI_IFNAME);
         lp.setMtu(mtu);
 
-        // Registering an agent with an MTU doesn't set the MTU...
+        // Registering an agent with an MTU only sets the MTU on U+.
         mWiFiAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI, lp);
         waitForIdle();
-        verifyMtuNeverSetOnWifiInterface();
+        verifyMtuSetOnWifiInterfaceOnlyStartingFromU(mtu);
         reset(mMockNetd);
 
-        // ... but prevents future updates with the same MTU from setting the MTU.
+        // Future updates with the same MTU don't set the MTU even on T when it's not set initially.
         mWiFiAgent.sendLinkProperties(lp);
         waitForIdle();
         verifyMtuNeverSetOnWifiInterface();
@@ -17622,8 +17687,8 @@ public class ConnectivityServiceTest {
         reset(mMockNetd);
 
         mWiFiAgent.connect(false /* validated */);
-        // The MTU is always (re-)applied when the network connects.
+        // Before U, the MTU is always (re-)applied when the network connects.
-        verifyMtuSetOnWifiInterface(mtu + 1);
+        verifyMtuSetOnWifiInterfaceOnlyUpToT(mtu + 1);
     }
 
     @Test