diff --git a/core/java/android/net/NetworkStateSnapshot.java b/core/java/android/net/NetworkStateSnapshot.java
index 9df861a..3915634 100644
--- a/core/java/android/net/NetworkStateSnapshot.java
+++ b/core/java/android/net/NetworkStateSnapshot.java
@@ -104,7 +104,10 @@
         return mSubscriberId;
     }
 
-    /** Get the legacy type of the network associated with this snapshot. */
+    /**
+     * Get the legacy type of the network associated with this snapshot.
+     * @return the legacy network type. See {@code ConnectivityManager#TYPE_*}.
+     */
     public int getLegacyType() {
         return mLegacyType;
     }
diff --git a/core/java/android/net/nsd/NsdManager.java b/core/java/android/net/nsd/NsdManager.java
index 5a25cfc..ae8d010 100644
--- a/core/java/android/net/nsd/NsdManager.java
+++ b/core/java/android/net/nsd/NsdManager.java
@@ -23,6 +23,9 @@
 import android.annotation.SdkConstant;
 import android.annotation.SdkConstant.SdkConstantType;
 import android.annotation.SystemService;
+import android.app.compat.CompatChanges;
+import android.compat.annotation.ChangeId;
+import android.compat.annotation.EnabledSince;
 import android.content.Context;
 import android.os.Handler;
 import android.os.HandlerThread;
@@ -126,6 +129,24 @@
     private static final boolean DBG = false;
 
     /**
+     * When enabled, apps targeting < Android 12 are considered legacy for
+     * the NSD native daemon.
+     * The platform will only keep the daemon running as long as there are
+     * any legacy apps connected.
+     *
+     * After Android 12, directly communicate with native daemon might not
+     * work since the native damon won't always stay alive.
+     * Use the NSD APIs from NsdManager as the replacement is recommended.
+     * An another alternative could be bundling your own mdns solutions instead of
+     * depending on the system mdns native daemon.
+     *
+     * @hide
+     */
+    @ChangeId
+    @EnabledSince(targetSdkVersion = android.os.Build.VERSION_CODES.S)
+    public static final long RUN_NATIVE_NSD_ONLY_IF_LEGACY_APPS = 191844585L;
+
+    /**
      * Broadcast intent action to indicate whether network service discovery is
      * enabled or disabled. An extra {@link #EXTRA_NSD_STATE} provides the state
      * information as int.
@@ -203,6 +224,9 @@
     public static final int DAEMON_CLEANUP                          = BASE + 21;
 
     /** @hide */
+    public static final int DAEMON_STARTUP                          = BASE + 22;
+
+    /** @hide */
     public static final int ENABLE                                  = BASE + 24;
     /** @hide */
     public static final int DISABLE                                 = BASE + 25;
@@ -232,6 +256,8 @@
         EVENT_NAMES.put(RESOLVE_SERVICE, "RESOLVE_SERVICE");
         EVENT_NAMES.put(RESOLVE_SERVICE_FAILED, "RESOLVE_SERVICE_FAILED");
         EVENT_NAMES.put(RESOLVE_SERVICE_SUCCEEDED, "RESOLVE_SERVICE_SUCCEEDED");
+        EVENT_NAMES.put(DAEMON_CLEANUP, "DAEMON_CLEANUP");
+        EVENT_NAMES.put(DAEMON_STARTUP, "DAEMON_STARTUP");
         EVENT_NAMES.put(ENABLE, "ENABLE");
         EVENT_NAMES.put(DISABLE, "DISABLE");
         EVENT_NAMES.put(NATIVE_DAEMON_EVENT, "NATIVE_DAEMON_EVENT");
@@ -494,6 +520,12 @@
         } catch (InterruptedException e) {
             fatal("Interrupted wait at init");
         }
+        if (CompatChanges.isChangeEnabled(RUN_NATIVE_NSD_ONLY_IF_LEGACY_APPS)) {
+            return;
+        }
+        // Only proactively start the daemon if the target SDK < S, otherwise the internal service
+        // would automatically start/stop the native daemon as needed.
+        mAsyncChannel.sendMessage(DAEMON_STARTUP);
     }
 
     private static void fatal(String msg) {
diff --git a/services/core/java/com/android/server/NsdService.java b/services/core/java/com/android/server/NsdService.java
index a9f3a1b..c9608a5 100644
--- a/services/core/java/com/android/server/NsdService.java
+++ b/services/core/java/com/android/server/NsdService.java
@@ -82,6 +82,8 @@
 
     private static final int INVALID_ID = 0;
     private int mUniqueId = 1;
+    // The count of the connected legacy clients.
+    private int mLegacyClientCount = 0;
 
     private class NsdStateMachine extends StateMachine {
 
@@ -107,7 +109,9 @@
             sendMessageDelayed(NsdManager.DAEMON_CLEANUP, mCleanupDelayMs);
         }
         private void maybeScheduleStop() {
-            if (!isAnyRequestActive()) {
+            // The native daemon should stay alive and can't be cleanup
+            // if any legacy client connected.
+            if (!isAnyRequestActive() && mLegacyClientCount == 0) {
                 scheduleStop();
             }
         }
@@ -175,11 +179,11 @@
                         if (cInfo != null) {
                             cInfo.expungeAllRequests();
                             mClients.remove(msg.replyTo);
+                            if (cInfo.isLegacy()) {
+                                mLegacyClientCount -= 1;
+                            }
                         }
-                        //Last client
-                        if (mClients.size() == 0) {
-                            scheduleStop();
-                        }
+                        maybeScheduleStop();
                         break;
                     case AsyncChannel.CMD_CHANNEL_FULL_CONNECTION:
                         AsyncChannel ac = new AsyncChannel();
@@ -208,6 +212,17 @@
                     case NsdManager.DAEMON_CLEANUP:
                         mDaemon.maybeStop();
                         break;
+                    // This event should be only sent by the legacy (target SDK < S) clients.
+                    // Mark the sending client as legacy.
+                    case NsdManager.DAEMON_STARTUP:
+                        cInfo = mClients.get(msg.replyTo);
+                        if (cInfo != null) {
+                            cancelStop();
+                            cInfo.setLegacy();
+                            mLegacyClientCount += 1;
+                            maybeStartDaemon();
+                        }
+                        break;
                     case NsdManager.NATIVE_DAEMON_EVENT:
                     default:
                         Slog.e(TAG, "Unhandled " + msg);
@@ -863,6 +878,9 @@
         /* A map from client id to the type of the request we had received */
         private final SparseIntArray mClientRequests = new SparseIntArray();
 
+        // The target SDK of this client < Build.VERSION_CODES.S
+        private boolean mIsLegacy = false;
+
         private ClientInfo(AsyncChannel c, Messenger m) {
             mChannel = c;
             mMessenger = m;
@@ -871,10 +889,11 @@
 
         @Override
         public String toString() {
-            StringBuffer sb = new StringBuffer();
+            StringBuilder sb = new StringBuilder();
             sb.append("mChannel ").append(mChannel).append("\n");
             sb.append("mMessenger ").append(mMessenger).append("\n");
             sb.append("mResolvedService ").append(mResolvedService).append("\n");
+            sb.append("mIsLegacy ").append(mIsLegacy).append("\n");
             for(int i = 0; i< mClientIds.size(); i++) {
                 int clientID = mClientIds.keyAt(i);
                 sb.append("clientId ").append(clientID).
@@ -884,6 +903,14 @@
             return sb.toString();
         }
 
+        private boolean isLegacy() {
+            return mIsLegacy;
+        }
+
+        private void setLegacy() {
+            mIsLegacy = true;
+        }
+
         // Remove any pending requests from the global map when we get rid of a client,
         // and send cancellations to the daemon.
         private void expungeAllRequests() {
diff --git a/services/core/java/com/android/server/net/NetworkStatsAccess.java b/services/core/java/com/android/server/net/NetworkStatsAccess.java
index ddc5ef2..d25eae4 100644
--- a/services/core/java/com/android/server/net/NetworkStatsAccess.java
+++ b/services/core/java/com/android/server/net/NetworkStatsAccess.java
@@ -27,6 +27,7 @@
 import android.app.admin.DevicePolicyManagerInternal;
 import android.content.Context;
 import android.content.pm.PackageManager;
+import android.os.Binder;
 import android.os.Process;
 import android.os.UserHandle;
 import android.telephony.TelephonyManager;
@@ -108,10 +109,17 @@
                 DevicePolicyManagerInternal.class);
         final TelephonyManager tm = (TelephonyManager)
                 context.getSystemService(Context.TELEPHONY_SERVICE);
-        boolean hasCarrierPrivileges = tm != null &&
-                tm.checkCarrierPrivilegesForPackageAnyPhone(callingPackage) ==
-                        TelephonyManager.CARRIER_PRIVILEGE_STATUS_HAS_ACCESS;
-        boolean isDeviceOwner = dpmi != null && dpmi.isActiveDeviceOwner(callingUid);
+        boolean hasCarrierPrivileges;
+        final long token = Binder.clearCallingIdentity();
+        try {
+            hasCarrierPrivileges = tm != null
+                    && tm.checkCarrierPrivilegesForPackageAnyPhone(callingPackage)
+                            == TelephonyManager.CARRIER_PRIVILEGE_STATUS_HAS_ACCESS;
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
+
+        final boolean isDeviceOwner = dpmi != null && dpmi.isActiveDeviceOwner(callingUid);
         final int appId = UserHandle.getAppId(callingUid);
         if (hasCarrierPrivileges || isDeviceOwner
                 || appId == Process.SYSTEM_UID || appId == Process.NETWORK_STACK_UID) {
diff --git a/services/core/java/com/android/server/net/NetworkStatsCollection.java b/services/core/java/com/android/server/net/NetworkStatsCollection.java
index a090c1a..df372b1 100644
--- a/services/core/java/com/android/server/net/NetworkStatsCollection.java
+++ b/services/core/java/com/android/server/net/NetworkStatsCollection.java
@@ -54,6 +54,8 @@
 
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.ArrayUtils;
+import com.android.internal.util.FastDataInput;
+import com.android.internal.util.FastDataOutput;
 import com.android.internal.util.FileRotator;
 import com.android.internal.util.IndentingPrintWriter;
 
@@ -89,6 +91,9 @@
     /** File header magic number: "ANET" */
     private static final int FILE_MAGIC = 0x414E4554;
 
+    /** Default buffer size from BufferedInputStream */
+    private static final int BUFFER_SIZE = 8192;
+
     private static final int VERSION_NETWORK_INIT = 1;
 
     private static final int VERSION_UID_INIT = 1;
@@ -435,7 +440,8 @@
 
     @Override
     public void read(InputStream in) throws IOException {
-        read((DataInput) new DataInputStream(in));
+        final FastDataInput dataIn = new FastDataInput(in, BUFFER_SIZE);
+        read(dataIn);
     }
 
     private void read(DataInput in) throws IOException {
@@ -474,8 +480,9 @@
 
     @Override
     public void write(OutputStream out) throws IOException {
-        write((DataOutput) new DataOutputStream(out));
-        out.flush();
+        final FastDataOutput dataOut = new FastDataOutput(out, BUFFER_SIZE);
+        write(dataOut);
+        dataOut.flush();
     }
 
     private void write(DataOutput out) throws IOException {
diff --git a/services/tests/servicestests/src/com/android/server/net/IpConfigStoreTest.java b/services/tests/servicestests/src/com/android/server/net/IpConfigStoreTest.java
index 401d6e3..2f77126 100644
--- a/services/tests/servicestests/src/com/android/server/net/IpConfigStoreTest.java
+++ b/services/tests/servicestests/src/com/android/server/net/IpConfigStoreTest.java
@@ -39,6 +39,8 @@
 import java.io.DataOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.InetAddress;
+import java.util.ArrayList;
 import java.util.Arrays;
 
 /**
@@ -53,8 +55,8 @@
         ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
         DataOutputStream outputStream = new DataOutputStream(byteStream);
 
-        IpConfiguration expectedConfig = new IpConfiguration(IpAssignment.DHCP,
-                ProxySettings.NONE, null, null);
+        final IpConfiguration expectedConfig =
+                newIpConfiguration(IpAssignment.DHCP, ProxySettings.NONE, null, null);
 
         // Emulate writing to old format.
         writeDhcpConfigV2(outputStream, KEY_CONFIG, expectedConfig);
@@ -78,18 +80,23 @@
         final String DNS_IP_ADDR_1 = "1.2.3.4";
         final String DNS_IP_ADDR_2 = "5.6.7.8";
 
-        StaticIpConfiguration staticIpConfiguration = new StaticIpConfiguration();
-        staticIpConfiguration.ipAddress = new LinkAddress(IP_ADDR_1);
-        staticIpConfiguration.dnsServers.add(InetAddresses.parseNumericAddress(DNS_IP_ADDR_1));
-        staticIpConfiguration.dnsServers.add(InetAddresses.parseNumericAddress(DNS_IP_ADDR_2));
+        final ArrayList<InetAddress> dnsServers = new ArrayList<>();
+        dnsServers.add(InetAddresses.parseNumericAddress(DNS_IP_ADDR_1));
+        dnsServers.add(InetAddresses.parseNumericAddress(DNS_IP_ADDR_2));
+        final StaticIpConfiguration staticIpConfiguration1 = new StaticIpConfiguration.Builder()
+                .setIpAddress(new LinkAddress(IP_ADDR_1))
+                .setDnsServers(dnsServers).build();
+        final StaticIpConfiguration staticIpConfiguration2 = new StaticIpConfiguration.Builder()
+                .setIpAddress(new LinkAddress(IP_ADDR_2))
+                .setDnsServers(dnsServers).build();
 
         ProxyInfo proxyInfo =
                 ProxyInfo.buildDirectProxy("10.10.10.10", 88, Arrays.asList("host1", "host2"));
 
-        IpConfiguration expectedConfig1 = new IpConfiguration(IpAssignment.STATIC,
-                ProxySettings.STATIC, staticIpConfiguration, proxyInfo);
-        IpConfiguration expectedConfig2 = new IpConfiguration(expectedConfig1);
-        expectedConfig2.getStaticIpConfiguration().ipAddress = new LinkAddress(IP_ADDR_2);
+        IpConfiguration expectedConfig1 = newIpConfiguration(IpAssignment.STATIC,
+                ProxySettings.STATIC, staticIpConfiguration1, proxyInfo);
+        IpConfiguration expectedConfig2 = newIpConfiguration(IpAssignment.STATIC,
+                ProxySettings.STATIC, staticIpConfiguration2, proxyInfo);
 
         ArrayMap<String, IpConfiguration> expectedNetworks = new ArrayMap<>();
         expectedNetworks.put(IFACE_1, expectedConfig1);
@@ -107,14 +114,24 @@
         assertEquals(expectedNetworks.get(IFACE_2), actualNetworks.get(IFACE_2));
     }
 
+    private IpConfiguration newIpConfiguration(IpAssignment ipAssignment,
+            ProxySettings proxySettings, StaticIpConfiguration staticIpConfig, ProxyInfo info) {
+        final IpConfiguration config = new IpConfiguration();
+        config.setIpAssignment(ipAssignment);
+        config.setProxySettings(proxySettings);
+        config.setStaticIpConfiguration(staticIpConfig);
+        config.setHttpProxy(info);
+        return config;
+    }
+
     // This is simplified snapshot of code that was used to store values in V2 format (key as int).
     private static void writeDhcpConfigV2(DataOutputStream out, int configKey,
             IpConfiguration config) throws IOException {
         out.writeInt(2);  // VERSION 2
-        switch (config.ipAssignment) {
+        switch (config.getIpAssignment()) {
             case DHCP:
                 out.writeUTF("ipAssignment");
-                out.writeUTF(config.ipAssignment.toString());
+                out.writeUTF(config.getIpAssignment().toString());
                 break;
             default:
                 fail("Not supported in test environment");