diff --git a/core/java/android/net/CaptivePortal.java b/core/java/android/net/CaptivePortal.java
index 7873fc0..1339432 100644
--- a/core/java/android/net/CaptivePortal.java
+++ b/core/java/android/net/CaptivePortal.java
@@ -15,6 +15,7 @@
  */
 package android.net;
 
+import android.annotation.NonNull;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.os.IBinder;
@@ -63,9 +64,7 @@
     private final IBinder mBinder;
 
     /** @hide */
-    @SystemApi
-    @TestApi
-    public CaptivePortal(IBinder binder) {
+    public CaptivePortal(@NonNull IBinder binder) {
         mBinder = binder;
     }
 
@@ -142,7 +141,7 @@
      */
     @SystemApi
     @TestApi
-    public void logEvent(int eventId, String packageName) {
+    public void logEvent(int eventId, @NonNull String packageName) {
         try {
             ICaptivePortal.Stub.asInterface(mBinder).logEvent(eventId, packageName);
         } catch (RemoteException e) {
diff --git a/core/java/android/net/ConnectivityManager.java b/core/java/android/net/ConnectivityManager.java
index e5802c2..ae93cf0 100644
--- a/core/java/android/net/ConnectivityManager.java
+++ b/core/java/android/net/ConnectivityManager.java
@@ -44,6 +44,7 @@
 import android.os.Looper;
 import android.os.Message;
 import android.os.Messenger;
+import android.os.ParcelFileDescriptor;
 import android.os.Process;
 import android.os.RemoteException;
 import android.os.ResultReceiver;
@@ -64,6 +65,8 @@
 import libcore.net.event.NetworkEventDispatcher;
 
 import java.io.FileDescriptor;
+import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.net.InetAddress;
@@ -1345,12 +1348,15 @@
     }
 
     /**
-     * Gets the URL that should be used for resolving whether a captive portal is present.
+     * Gets a URL that can be used for resolving whether a captive portal is present.
      * 1. This URL should respond with a 204 response to a GET request to indicate no captive
      *    portal is present.
      * 2. This URL must be HTTP as redirect responses are used to find captive portal
      *    sign-in pages. Captive portals cannot respond to HTTPS requests with redirects.
      *
+     * The system network validation may be using different strategies to detect captive portals,
+     * so this method does not necessarily return a URL used by the system. It only returns a URL
+     * that may be relevant for other components trying to detect captive portals.
      * @hide
      */
     @SystemApi
@@ -1920,14 +1926,22 @@
      * @return A {@link SocketKeepalive} object that can be used to control the keepalive on the
      *         given socket.
      **/
-    public SocketKeepalive createSocketKeepalive(@NonNull Network network,
+    public @NonNull SocketKeepalive createSocketKeepalive(@NonNull Network network,
             @NonNull UdpEncapsulationSocket socket,
             @NonNull InetAddress source,
             @NonNull InetAddress destination,
             @NonNull @CallbackExecutor Executor executor,
             @NonNull Callback callback) {
-        return new NattSocketKeepalive(mService, network, socket.getFileDescriptor(),
-            socket.getResourceId(), source, destination, executor, callback);
+        ParcelFileDescriptor dup;
+        try {
+            dup = ParcelFileDescriptor.dup(socket.getFileDescriptor());
+        } catch (IOException ignored) {
+            // Construct an invalid fd, so that if the user later calls start(), it will fail with
+            // ERROR_INVALID_SOCKET.
+            dup = new ParcelFileDescriptor(new FileDescriptor());
+        }
+        return new NattSocketKeepalive(mService, network, dup, socket.getResourceId(), source,
+                destination, executor, callback);
     }
 
     /**
@@ -1935,9 +1949,9 @@
      * by system apps which don't use IpSecService to create {@link UdpEncapsulationSocket}.
      *
      * @param network The {@link Network} the socket is on.
-     * @param fd The {@link FileDescriptor} that needs to be kept alive. The provided
-     *        {@link FileDescriptor} must be bound to a port and the keepalives will be sent from
-     *        that port.
+     * @param pfd The {@link ParcelFileDescriptor} that needs to be kept alive. The provided
+     *        {@link ParcelFileDescriptor} must be bound to a port and the keepalives will be sent
+     *        from that port.
      * @param source The source address of the {@link UdpEncapsulationSocket}.
      * @param destination The destination address of the {@link UdpEncapsulationSocket}. The
      *        keepalive packets will always be sent to port 4500 of the given {@code destination}.
@@ -1953,14 +1967,22 @@
      */
     @SystemApi
     @RequiresPermission(android.Manifest.permission.PACKET_KEEPALIVE_OFFLOAD)
-    public SocketKeepalive createNattKeepalive(@NonNull Network network,
-            @NonNull FileDescriptor fd,
+    public @NonNull SocketKeepalive createNattKeepalive(@NonNull Network network,
+            @NonNull ParcelFileDescriptor pfd,
             @NonNull InetAddress source,
             @NonNull InetAddress destination,
             @NonNull @CallbackExecutor Executor executor,
             @NonNull Callback callback) {
-        return new NattSocketKeepalive(mService, network, fd, INVALID_RESOURCE_ID /* Unused */,
-                source, destination, executor, callback);
+        ParcelFileDescriptor dup;
+        try {
+            dup = pfd.dup();
+        } catch (IOException ignored) {
+            // Construct an invalid fd, so that if the user later calls start(), it will fail with
+            // ERROR_INVALID_SOCKET.
+            dup = new ParcelFileDescriptor(new FileDescriptor());
+        }
+        return new NattSocketKeepalive(mService, network, dup,
+                INVALID_RESOURCE_ID /* Unused */, source, destination, executor, callback);
     }
 
     /**
@@ -1984,11 +2006,19 @@
      */
     @SystemApi
     @RequiresPermission(android.Manifest.permission.PACKET_KEEPALIVE_OFFLOAD)
-    public SocketKeepalive createSocketKeepalive(@NonNull Network network,
+    public @NonNull SocketKeepalive createSocketKeepalive(@NonNull Network network,
             @NonNull Socket socket,
             @NonNull Executor executor,
             @NonNull Callback callback) {
-        return new TcpSocketKeepalive(mService, network, socket, executor, callback);
+        ParcelFileDescriptor dup;
+        try {
+            dup = ParcelFileDescriptor.fromSocket(socket);
+        } catch (UncheckedIOException ignored) {
+            // Construct an invalid fd, so that if the user later calls start(), it will fail with
+            // ERROR_INVALID_SOCKET.
+            dup = new ParcelFileDescriptor(new FileDescriptor());
+        }
+        return new TcpSocketKeepalive(mService, network, dup, executor, callback);
     }
 
     /**
@@ -3320,7 +3350,7 @@
          * @param network The {@link Network} whose blocked status has changed.
          * @param blocked The blocked status of this {@link Network}.
          */
-        public void onBlockedStatusChanged(Network network, boolean blocked) {}
+        public void onBlockedStatusChanged(@NonNull Network network, boolean blocked) {}
 
         private NetworkRequest networkRequest;
     }
@@ -4088,7 +4118,7 @@
     @SystemApi
     @TestApi
     @RequiresPermission(NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK)
-    public void startCaptivePortalApp(Network network, Bundle appExtras) {
+    public void startCaptivePortalApp(@NonNull Network network, @NonNull Bundle appExtras) {
         try {
             mService.startCaptivePortalAppInternal(network, appExtras);
         } catch (RemoteException e) {
@@ -4101,9 +4131,12 @@
      * @hide
      */
     @SystemApi
-    public boolean getAvoidBadWifi() {
+    @RequiresPermission(anyOf = {
+            NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK,
+            android.Manifest.permission.NETWORK_STACK})
+    public boolean shouldAvoidBadWifi() {
         try {
-            return mService.getAvoidBadWifi();
+            return mService.shouldAvoidBadWifi();
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
diff --git a/core/java/android/net/DnsResolver.java b/core/java/android/net/DnsResolver.java
index 93b8cf8..5980251 100644
--- a/core/java/android/net/DnsResolver.java
+++ b/core/java/android/net/DnsResolver.java
@@ -16,6 +16,7 @@
 
 package android.net;
 
+import static android.net.NetworkUtils.resNetworkCancel;
 import static android.net.NetworkUtils.resNetworkQuery;
 import static android.net.NetworkUtils.resNetworkResult;
 import static android.net.NetworkUtils.resNetworkSend;
@@ -26,6 +27,7 @@
 import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
+import android.os.CancellationSignal;
 import android.os.Looper;
 import android.system.ErrnoException;
 import android.util.Log;
@@ -191,11 +193,18 @@
      * @param query blob message
      * @param flags flags as a combination of the FLAGS_* constants
      * @param executor The {@link Executor} that the callback should be executed on.
+     * @param cancellationSignal used by the caller to signal if the query should be
+     *    cancelled. May be {@code null}.
      * @param callback an {@link AnswerCallback} which will be called to notify the caller
-     *         of the result of dns query.
+     *    of the result of dns query.
      */
     public <T> void query(@Nullable Network network, @NonNull byte[] query, @QueryFlag int flags,
-            @NonNull @CallbackExecutor Executor executor, @NonNull AnswerCallback<T> callback) {
+            @NonNull @CallbackExecutor Executor executor,
+            @Nullable CancellationSignal cancellationSignal,
+            @NonNull AnswerCallback<T> callback) {
+        if (cancellationSignal != null && cancellationSignal.isCanceled()) {
+            return;
+        }
         final FileDescriptor queryfd;
         try {
             queryfd = resNetworkSend((network != null
@@ -205,6 +214,7 @@
             return;
         }
 
+        maybeAddCancellationSignal(cancellationSignal, queryfd);
         registerFDListener(executor, queryfd, callback);
     }
 
@@ -219,12 +229,19 @@
      * @param nsType dns resource record (RR) type as one of the TYPE_* constants
      * @param flags flags as a combination of the FLAGS_* constants
      * @param executor The {@link Executor} that the callback should be executed on.
+     * @param cancellationSignal used by the caller to signal if the query should be
+     *    cancelled. May be {@code null}.
      * @param callback an {@link AnswerCallback} which will be called to notify the caller
-     *         of the result of dns query.
+     *    of the result of dns query.
      */
     public <T> void query(@Nullable Network network, @NonNull String domain,
             @QueryClass int nsClass, @QueryType int nsType, @QueryFlag int flags,
-            @NonNull @CallbackExecutor Executor executor, @NonNull AnswerCallback<T> callback) {
+            @NonNull @CallbackExecutor Executor executor,
+            @Nullable CancellationSignal cancellationSignal,
+            @NonNull AnswerCallback<T> callback) {
+        if (cancellationSignal != null && cancellationSignal.isCanceled()) {
+            return;
+        }
         final FileDescriptor queryfd;
         try {
             queryfd = resNetworkQuery((network != null
@@ -233,6 +250,8 @@
             callback.onQueryException(e);
             return;
         }
+
+        maybeAddCancellationSignal(cancellationSignal, queryfd);
         registerFDListener(executor, queryfd, callback);
     }
 
@@ -264,6 +283,17 @@
                 });
     }
 
+    private void maybeAddCancellationSignal(@Nullable CancellationSignal cancellationSignal,
+            @NonNull FileDescriptor queryfd) {
+        if (cancellationSignal == null) return;
+        cancellationSignal.setOnCancelListener(
+                () -> {
+                    Looper.getMainLooper().getQueue()
+                            .removeOnFileDescriptorEventListener(queryfd);
+                    resNetworkCancel(queryfd);
+            });
+    }
+
     private static class DnsAddressAnswer extends DnsPacket {
         private static final String TAG = "DnsResolver.DnsAddressAnswer";
         private static final boolean DBG = false;
diff --git a/core/java/android/net/IConnectivityManager.aidl b/core/java/android/net/IConnectivityManager.aidl
index 24e6a85..61648dc 100644
--- a/core/java/android/net/IConnectivityManager.aidl
+++ b/core/java/android/net/IConnectivityManager.aidl
@@ -182,7 +182,7 @@
     void startCaptivePortalApp(in Network network);
     void startCaptivePortalAppInternal(in Network network, in Bundle appExtras);
 
-    boolean getAvoidBadWifi();
+    boolean shouldAvoidBadWifi();
     int getMultipathPreference(in Network Network);
 
     NetworkRequest getDefaultRequest();
diff --git a/core/java/android/net/IpPrefix.java b/core/java/android/net/IpPrefix.java
index 21bbd30..402bffd 100644
--- a/core/java/android/net/IpPrefix.java
+++ b/core/java/android/net/IpPrefix.java
@@ -16,6 +16,7 @@
 
 package android.net;
 
+import android.annotation.NonNull;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.os.Parcel;
@@ -70,7 +71,7 @@
      *
      * @hide
      */
-    public IpPrefix(byte[] address, int prefixLength) {
+    public IpPrefix(@NonNull byte[] address, int prefixLength) {
         this.address = address.clone();
         this.prefixLength = prefixLength;
         checkAndMaskAddressAndPrefixLength();
@@ -87,7 +88,7 @@
      */
     @SystemApi
     @TestApi
-    public IpPrefix(InetAddress address, int prefixLength) {
+    public IpPrefix(@NonNull InetAddress address, int prefixLength) {
         // We don't reuse the (byte[], int) constructor because it calls clone() on the byte array,
         // which is unnecessary because getAddress() already returns a clone.
         this.address = address.getAddress();
@@ -106,7 +107,7 @@
      */
     @SystemApi
     @TestApi
-    public IpPrefix(String prefix) {
+    public IpPrefix(@NonNull String prefix) {
         // We don't reuse the (InetAddress, int) constructor because "error: call to this must be
         // first statement in constructor". We could factor out setting the member variables to an
         // init() method, but if we did, then we'd have to make the members non-final, or "error:
diff --git a/core/java/android/net/LinkAddress.java b/core/java/android/net/LinkAddress.java
index 78a4e72..333603f 100644
--- a/core/java/android/net/LinkAddress.java
+++ b/core/java/android/net/LinkAddress.java
@@ -26,6 +26,7 @@
 import static android.system.OsConstants.RT_SCOPE_UNIVERSE;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.annotation.UnsupportedAppUsage;
@@ -107,8 +108,8 @@
      *
      * Per RFC 4193 section 8, fc00::/7 identifies these addresses.
      */
-    private boolean isIPv6ULA() {
-        if (isIPv6()) {
+    private boolean isIpv6ULA() {
+        if (isIpv6()) {
             byte[] bytes = address.getAddress();
             return ((bytes[0] & (byte)0xfe) == (byte)0xfc);
         }
@@ -121,17 +122,29 @@
      */
     @TestApi
     @SystemApi
-    public boolean isIPv6() {
+    public boolean isIpv6() {
         return address instanceof Inet6Address;
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return true if the address is IPv6.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean isIPv6() {
+        return isIpv6();
+    }
+
+    /**
      * @return true if the address is IPv4 or is a mapped IPv4 address.
      * @hide
      */
     @TestApi
     @SystemApi
-    public boolean isIPv4() {
+    public boolean isIpv4() {
         return address instanceof Inet4Address;
     }
 
@@ -217,7 +230,7 @@
      */
     @SystemApi
     @TestApi
-    public LinkAddress(String address, int flags, int scope) {
+    public LinkAddress(@NonNull String address, int flags, int scope) {
         // This may throw an IllegalArgumentException; catching it is the caller's responsibility.
         // TODO: consider rejecting mapped IPv4 addresses such as "::ffff:192.0.2.5/24".
         Pair<InetAddress, Integer> ipAndMask = NetworkUtils.parseIpAndMask(address);
@@ -276,7 +289,10 @@
      */
     @TestApi
     @SystemApi
-    public boolean isSameAddressAs(LinkAddress other) {
+    public boolean isSameAddressAs(@Nullable LinkAddress other) {
+        if (other == null) {
+            return false;
+        }
         return address.equals(other.address) && prefixLength == other.prefixLength;
     }
 
@@ -331,10 +347,10 @@
          * state has cleared either DAD has succeeded or failed, and both
          * flags are cleared regardless).
          */
-        return (scope == RT_SCOPE_UNIVERSE &&
-                !isIPv6ULA() &&
-                (flags & (IFA_F_DADFAILED | IFA_F_DEPRECATED)) == 0L &&
-                ((flags & IFA_F_TENTATIVE) == 0L || (flags & IFA_F_OPTIMISTIC) != 0L));
+        return (scope == RT_SCOPE_UNIVERSE
+                && !isIpv6ULA()
+                && (flags & (IFA_F_DADFAILED | IFA_F_DEPRECATED)) == 0L
+                && ((flags & IFA_F_TENTATIVE) == 0L || (flags & IFA_F_OPTIMISTIC) != 0L));
     }
 
     /**
diff --git a/core/java/android/net/LinkProperties.java b/core/java/android/net/LinkProperties.java
index b52b15e..d5ca664 100644
--- a/core/java/android/net/LinkProperties.java
+++ b/core/java/android/net/LinkProperties.java
@@ -54,11 +54,11 @@
     // The interface described by the network link.
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)
     private String mIfaceName;
-    private ArrayList<LinkAddress> mLinkAddresses = new ArrayList<>();
-    private ArrayList<InetAddress> mDnses = new ArrayList<>();
+    private final ArrayList<LinkAddress> mLinkAddresses = new ArrayList<>();
+    private final ArrayList<InetAddress> mDnses = new ArrayList<>();
     // PCSCF addresses are addresses of SIP proxies that only exist for the IMS core service.
-    private ArrayList<InetAddress> mPcscfs = new ArrayList<InetAddress>();
-    private ArrayList<InetAddress> mValidatedPrivateDnses = new ArrayList<>();
+    private final ArrayList<InetAddress> mPcscfs = new ArrayList<InetAddress>();
+    private final ArrayList<InetAddress> mValidatedPrivateDnses = new ArrayList<>();
     private boolean mUsePrivateDns;
     private String mPrivateDnsServerName;
     private String mDomains;
@@ -150,8 +150,8 @@
             // connections getting stuck until timeouts fire and other
             // baffling failures. Therefore, loss of either IPv4 or IPv6 on a
             // previously dual-stack network is deemed a lost of provisioning.
-            if ((before.isIPv4Provisioned() && !after.isIPv4Provisioned()) ||
-                (before.isIPv6Provisioned() && !after.isIPv6Provisioned())) {
+            if ((before.isIpv4Provisioned() && !after.isIpv4Provisioned())
+                    || (before.isIpv6Provisioned() && !after.isIpv6Provisioned())) {
                 return ProvisioningChange.LOST_PROVISIONING;
             }
             return ProvisioningChange.STILL_PROVISIONED;
@@ -165,9 +165,8 @@
     }
 
     /**
-     * @hide
+     * Constructs a new {@code LinkProperties} with default values.
      */
-    @SystemApi
     public LinkProperties() {
     }
 
@@ -176,7 +175,7 @@
      */
     @SystemApi
     @TestApi
-    public LinkProperties(LinkProperties source) {
+    public LinkProperties(@Nullable LinkProperties source) {
         if (source != null) {
             mIfaceName = source.mIfaceName;
             mLinkAddresses.addAll(source.mLinkAddresses);
@@ -202,10 +201,8 @@
      * will have their interface changed to match this new value.
      *
      * @param iface The name of the network interface used for this link.
-     * @hide
      */
-    @SystemApi
-    public void setInterfaceName(String iface) {
+    public void setInterfaceName(@Nullable String iface) {
         mIfaceName = iface;
         ArrayList<RouteInfo> newRoutes = new ArrayList<>(mRoutes.size());
         for (RouteInfo route : mRoutes) {
@@ -227,7 +224,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public List<String> getAllInterfaceNames() {
+    public @NonNull List<String> getAllInterfaceNames() {
         List<String> interfaceNames = new ArrayList<>(mStackedLinks.size() + 1);
         if (mIfaceName != null) interfaceNames.add(mIfaceName);
         for (LinkProperties stacked: mStackedLinks.values()) {
@@ -247,8 +244,8 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public List<InetAddress> getAddresses() {
-        List<InetAddress> addresses = new ArrayList<>();
+    public @NonNull List<InetAddress> getAddresses() {
+        final List<InetAddress> addresses = new ArrayList<>();
         for (LinkAddress linkAddress : mLinkAddresses) {
             addresses.add(linkAddress.getAddress());
         }
@@ -260,7 +257,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public List<InetAddress> getAllAddresses() {
+    public @NonNull List<InetAddress> getAllAddresses() {
         List<InetAddress> addresses = new ArrayList<>();
         for (LinkAddress linkAddress : mLinkAddresses) {
             addresses.add(linkAddress.getAddress());
@@ -289,7 +286,7 @@
      */
     @SystemApi
     @TestApi
-    public boolean addLinkAddress(LinkAddress address) {
+    public boolean addLinkAddress(@NonNull LinkAddress address) {
         if (address == null) {
             return false;
         }
@@ -318,7 +315,10 @@
      */
     @SystemApi
     @TestApi
-    public boolean removeLinkAddress(LinkAddress toRemove) {
+    public boolean removeLinkAddress(@NonNull LinkAddress toRemove) {
+        if (toRemove == null) {
+            return false;
+        }
         int i = findLinkAddressIndex(toRemove);
         if (i >= 0) {
             mLinkAddresses.remove(i);
@@ -333,7 +333,7 @@
      *
      * @return An unmodifiable {@link List} of {@link LinkAddress} for this link.
      */
-    public List<LinkAddress> getLinkAddresses() {
+    public @NonNull List<LinkAddress> getLinkAddresses() {
         return Collections.unmodifiableList(mLinkAddresses);
     }
 
@@ -356,10 +356,8 @@
      *
      * @param addresses The {@link Collection} of {@link LinkAddress} to set in this
      *                  object.
-     * @hide
      */
-    @SystemApi
-    public void setLinkAddresses(Collection<LinkAddress> addresses) {
+    public void setLinkAddresses(@NonNull Collection<LinkAddress> addresses) {
         mLinkAddresses.clear();
         for (LinkAddress address: addresses) {
             addLinkAddress(address);
@@ -375,7 +373,7 @@
      */
     @TestApi
     @SystemApi
-    public boolean addDnsServer(InetAddress dnsServer) {
+    public boolean addDnsServer(@NonNull InetAddress dnsServer) {
         if (dnsServer != null && !mDnses.contains(dnsServer)) {
             mDnses.add(dnsServer);
             return true;
@@ -392,7 +390,7 @@
      */
     @TestApi
     @SystemApi
-    public boolean removeDnsServer(InetAddress dnsServer) {
+    public boolean removeDnsServer(@NonNull InetAddress dnsServer) {
         if (dnsServer != null) {
             return mDnses.remove(dnsServer);
         }
@@ -404,10 +402,8 @@
      * the given {@link Collection} of {@link InetAddress} objects.
      *
      * @param dnsServers The {@link Collection} of DNS servers to set in this object.
-     * @hide
      */
-    @SystemApi
-    public void setDnsServers(Collection<InetAddress> dnsServers) {
+    public void setDnsServers(@NonNull Collection<InetAddress> dnsServers) {
         mDnses.clear();
         for (InetAddress dnsServer: dnsServers) {
             addDnsServer(dnsServer);
@@ -420,7 +416,7 @@
      * @return An unmodifiable {@link List} of {@link InetAddress} for DNS servers on
      *         this link.
      */
-    public List<InetAddress> getDnsServers() {
+    public @NonNull List<InetAddress> getDnsServers() {
         return Collections.unmodifiableList(mDnses);
     }
 
@@ -490,7 +486,7 @@
      * @return true if the DNS server was added, false if it was already present.
      * @hide
      */
-    public boolean addValidatedPrivateDnsServer(InetAddress dnsServer) {
+    public boolean addValidatedPrivateDnsServer(@NonNull InetAddress dnsServer) {
         if (dnsServer != null && !mValidatedPrivateDnses.contains(dnsServer)) {
             mValidatedPrivateDnses.add(dnsServer);
             return true;
@@ -506,11 +502,8 @@
      * @return true if the DNS server was removed, false if it did not exist.
      * @hide
      */
-    public boolean removeValidatedPrivateDnsServer(InetAddress dnsServer) {
-        if (dnsServer != null) {
-            return mValidatedPrivateDnses.remove(dnsServer);
-        }
-        return false;
+    public boolean removeValidatedPrivateDnsServer(@NonNull InetAddress dnsServer) {
+        return mValidatedPrivateDnses.remove(dnsServer);
     }
 
     /**
@@ -523,7 +516,7 @@
      */
     @TestApi
     @SystemApi
-    public void setValidatedPrivateDnsServers(Collection<InetAddress> dnsServers) {
+    public void setValidatedPrivateDnsServers(@NonNull Collection<InetAddress> dnsServers) {
         mValidatedPrivateDnses.clear();
         for (InetAddress dnsServer: dnsServers) {
             addValidatedPrivateDnsServer(dnsServer);
@@ -534,13 +527,13 @@
      * Returns all the {@link InetAddress} for validated private DNS servers on this link.
      * These are resolved from the private DNS server name.
      *
-     * @return An umodifiable {@link List} of {@link InetAddress} for validated private
+     * @return An unmodifiable {@link List} of {@link InetAddress} for validated private
      *         DNS servers on this link.
      * @hide
      */
     @TestApi
     @SystemApi
-    public List<InetAddress> getValidatedPrivateDnsServers() {
+    public @NonNull List<InetAddress> getValidatedPrivateDnsServers() {
         return Collections.unmodifiableList(mValidatedPrivateDnses);
     }
 
@@ -551,7 +544,7 @@
      * @return true if the PCSCF server was added, false otherwise.
      * @hide
      */
-    public boolean addPcscfServer(InetAddress pcscfServer) {
+    public boolean addPcscfServer(@NonNull InetAddress pcscfServer) {
         if (pcscfServer != null && !mPcscfs.contains(pcscfServer)) {
             mPcscfs.add(pcscfServer);
             return true;
@@ -562,27 +555,24 @@
     /**
      * Removes the given {@link InetAddress} from the list of PCSCF servers.
      *
-     * @param pcscf Server The {@link InetAddress} to remove from the list of PCSCF servers.
+     * @param pcscfServer The {@link InetAddress} to remove from the list of PCSCF servers.
      * @return true if the PCSCF server was removed, false otherwise.
      * @hide
      */
-    public boolean removePcscfServer(InetAddress pcscfServer) {
-        if (pcscfServer != null) {
-            return mPcscfs.remove(pcscfServer);
-        }
-        return false;
+    public boolean removePcscfServer(@NonNull InetAddress pcscfServer) {
+        return mPcscfs.remove(pcscfServer);
     }
 
     /**
      * Replaces the PCSCF servers in this {@code LinkProperties} with
      * the given {@link Collection} of {@link InetAddress} objects.
      *
-     * @param addresses The {@link Collection} of PCSCF servers to set in this object.
+     * @param pcscfServers The {@link Collection} of PCSCF servers to set in this object.
      * @hide
      */
     @SystemApi
     @TestApi
-    public void setPcscfServers(Collection<InetAddress> pcscfServers) {
+    public void setPcscfServers(@NonNull Collection<InetAddress> pcscfServers) {
         mPcscfs.clear();
         for (InetAddress pcscfServer: pcscfServers) {
             addPcscfServer(pcscfServer);
@@ -598,7 +588,7 @@
      */
     @SystemApi
     @TestApi
-    public List<InetAddress> getPcscfServers() {
+    public @NonNull List<InetAddress> getPcscfServers() {
         return Collections.unmodifiableList(mPcscfs);
     }
 
@@ -607,20 +597,18 @@
      *
      * @param domains A {@link String} listing in priority order the comma separated
      *                domains to search when resolving host names on this link.
-     * @hide
      */
-    @SystemApi
-    public void setDomains(String domains) {
+    public void setDomains(@Nullable String domains) {
         mDomains = domains;
     }
 
     /**
-     * Get the DNS domains search path set for this link.
+     * Get the DNS domains search path set for this link. May be {@code null} if not set.
      *
-     * @return A {@link String} containing the comma separated domains to search when resolving
-     *         host names on this link.
+     * @return A {@link String} containing the comma separated domains to search when resolving host
+     *         names on this link or {@code null}.
      */
-    public String getDomains() {
+    public @Nullable String getDomains() {
         return mDomains;
     }
 
@@ -630,9 +618,7 @@
      * 10000 will be ignored.
      *
      * @param mtu The MTU to use for this link.
-     * @hide
      */
-    @SystemApi
     public void setMtu(int mtu) {
         mMtu = mtu;
     }
@@ -657,20 +643,20 @@
      */
     @TestApi
     @SystemApi
-    public void setTcpBufferSizes(String tcpBufferSizes) {
+    public void setTcpBufferSizes(@Nullable String tcpBufferSizes) {
         mTcpBufferSizes = tcpBufferSizes;
     }
 
     /**
-     * Gets the tcp buffer sizes.
+     * Gets the tcp buffer sizes. May be {@code null} if not set.
      *
-     * @return the tcp buffer sizes to use when this link is the system default.
+     * @return the tcp buffer sizes to use when this link is the system default or {@code null}.
      *
      * @hide
      */
     @TestApi
     @SystemApi
-    public String getTcpBufferSizes() {
+    public @Nullable String getTcpBufferSizes() {
         return mTcpBufferSizes;
     }
 
@@ -690,23 +676,18 @@
      *
      * @param route A {@link RouteInfo} to add to this object.
      * @return {@code false} if the route was already present, {@code true} if it was added.
-     *
-     * @hide
      */
-    @SystemApi
-    public boolean addRoute(RouteInfo route) {
-        if (route != null) {
-            String routeIface = route.getInterface();
-            if (routeIface != null && !routeIface.equals(mIfaceName)) {
-                throw new IllegalArgumentException(
-                   "Route added with non-matching interface: " + routeIface +
-                   " vs. " + mIfaceName);
-            }
-            route = routeWithInterface(route);
-            if (!mRoutes.contains(route)) {
-                mRoutes.add(route);
-                return true;
-            }
+    public boolean addRoute(@NonNull RouteInfo route) {
+        String routeIface = route.getInterface();
+        if (routeIface != null && !routeIface.equals(mIfaceName)) {
+            throw new IllegalArgumentException(
+                    "Route added with non-matching interface: " + routeIface
+                            + " vs. " + mIfaceName);
+        }
+        route = routeWithInterface(route);
+        if (!mRoutes.contains(route)) {
+            mRoutes.add(route);
+            return true;
         }
         return false;
     }
@@ -722,10 +703,8 @@
      */
     @TestApi
     @SystemApi
-    public boolean removeRoute(RouteInfo route) {
-        return route != null &&
-                Objects.equals(mIfaceName, route.getInterface()) &&
-                mRoutes.remove(route);
+    public boolean removeRoute(@NonNull RouteInfo route) {
+        return Objects.equals(mIfaceName, route.getInterface()) && mRoutes.remove(route);
     }
 
     /**
@@ -733,7 +712,7 @@
      *
      * @return An unmodifiable {@link List} of {@link RouteInfo} for this link.
      */
-    public List<RouteInfo> getRoutes() {
+    public @NonNull List<RouteInfo> getRoutes() {
         return Collections.unmodifiableList(mRoutes);
     }
 
@@ -753,7 +732,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public List<RouteInfo> getAllRoutes() {
+    public @NonNull List<RouteInfo> getAllRoutes() {
         List<RouteInfo> routes = new ArrayList<>(mRoutes);
         for (LinkProperties stacked: mStackedLinks.values()) {
             routes.addAll(stacked.getAllRoutes());
@@ -767,26 +746,24 @@
      * not enforce it and applications may ignore them.
      *
      * @param proxy A {@link ProxyInfo} defining the HTTP Proxy to use on this link.
-     * @hide
      */
-    @SystemApi
-    public void setHttpProxy(ProxyInfo proxy) {
+    public void setHttpProxy(@Nullable ProxyInfo proxy) {
         mHttpProxy = proxy;
     }
 
     /**
      * Gets the recommended {@link ProxyInfo} (or {@code null}) set on this link.
      *
-     * @return The {@link ProxyInfo} set on this link
+     * @return The {@link ProxyInfo} set on this link or {@code null}.
      */
-    public ProxyInfo getHttpProxy() {
+    public @Nullable ProxyInfo getHttpProxy() {
         return mHttpProxy;
     }
 
     /**
      * Returns the NAT64 prefix in use on this link, if any.
      *
-     * @return the NAT64 prefix.
+     * @return the NAT64 prefix or {@code null}.
      * @hide
      */
     @SystemApi
@@ -799,14 +776,14 @@
      * Sets the NAT64 prefix in use on this link.
      *
      * Currently, only 96-bit prefixes (i.e., where the 32-bit IPv4 address is at the end of the
-     * 128-bit IPv6 address) are supported.
+     * 128-bit IPv6 address) are supported or {@code null} for no prefix.
      *
      * @param prefix the NAT64 prefix.
      * @hide
      */
     @SystemApi
     @TestApi
-    public void setNat64Prefix(IpPrefix prefix) {
+    public void setNat64Prefix(@Nullable IpPrefix prefix) {
         if (prefix != null && prefix.getPrefixLength() != 96) {
             throw new IllegalArgumentException("Only 96-bit prefixes are supported: " + prefix);
         }
@@ -818,15 +795,15 @@
      *
      * If there is already a stacked link with the same interface name as link,
      * that link is replaced with link. Otherwise, link is added to the list
-     * of stacked links. If link is null, nothing changes.
+     * of stacked links.
      *
      * @param link The link to add.
      * @return true if the link was stacked, false otherwise.
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean addStackedLink(LinkProperties link) {
-        if (link != null && link.getInterfaceName() != null) {
+    public boolean addStackedLink(@NonNull LinkProperties link) {
+        if (link.getInterfaceName() != null) {
             mStackedLinks.put(link.getInterfaceName(), link);
             return true;
         }
@@ -843,12 +820,9 @@
      * @return true if the link was removed, false otherwise.
      * @hide
      */
-    public boolean removeStackedLink(String iface) {
-        if (iface != null) {
-            LinkProperties removed = mStackedLinks.remove(iface);
-            return removed != null;
-        }
-        return false;
+    public boolean removeStackedLink(@NonNull String iface) {
+        LinkProperties removed = mStackedLinks.remove(iface);
+        return removed != null;
     }
 
     /**
@@ -860,7 +834,7 @@
         if (mStackedLinks.isEmpty()) {
             return Collections.emptyList();
         }
-        List<LinkProperties> stacked = new ArrayList<>();
+        final List<LinkProperties> stacked = new ArrayList<>();
         for (LinkProperties link : mStackedLinks.values()) {
             stacked.add(new LinkProperties(link));
         }
@@ -869,9 +843,7 @@
 
     /**
      * Clears this object to its initial state.
-     * @hide
      */
-    @SystemApi
     public void clear() {
         mIfaceName = null;
         mLinkAddresses.clear();
@@ -988,7 +960,7 @@
      */
     @TestApi
     @SystemApi
-    public boolean hasIPv4Address() {
+    public boolean hasIpv4Address() {
         for (LinkAddress address : mLinkAddresses) {
             if (address.getAddress() instanceof Inet4Address) {
                 return true;
@@ -998,15 +970,27 @@
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return {@code true} if there is an IPv4 address, {@code false} otherwise.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean hasIPv4Address() {
+        return hasIpv4Address();
+    }
+
+    /**
      * Returns true if this link or any of its stacked interfaces has an IPv4 address.
      *
      * @return {@code true} if there is an IPv4 address, {@code false} otherwise.
      */
-    private boolean hasIPv4AddressOnInterface(String iface) {
+    private boolean hasIpv4AddressOnInterface(String iface) {
         // mIfaceName can be null.
-        return (Objects.equals(iface, mIfaceName) && hasIPv4Address()) ||
-                (iface != null && mStackedLinks.containsKey(iface) &&
-                        mStackedLinks.get(iface).hasIPv4Address());
+        return (Objects.equals(iface, mIfaceName) && hasIpv4Address())
+                || (iface != null && mStackedLinks.containsKey(iface)
+                        && mStackedLinks.get(iface).hasIpv4Address());
     }
 
     /**
@@ -1017,7 +1001,7 @@
      */
     @TestApi
     @SystemApi
-    public boolean hasGlobalIPv6Address() {
+    public boolean hasGlobalIpv6Address() {
         for (LinkAddress address : mLinkAddresses) {
           if (address.getAddress() instanceof Inet6Address && address.isGlobalPreferred()) {
             return true;
@@ -1027,13 +1011,25 @@
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return {@code true} if there is a global preferred IPv6 address, {@code false} otherwise.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean hasGlobalIPv6Address() {
+        return hasGlobalIpv6Address();
+    }
+
+    /**
      * Returns true if this link has an IPv4 default route.
      *
      * @return {@code true} if there is an IPv4 default route, {@code false} otherwise.
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean hasIPv4DefaultRoute() {
+    public boolean hasIpv4DefaultRoute() {
         for (RouteInfo r : mRoutes) {
             if (r.isIPv4Default()) {
                 return true;
@@ -1043,6 +1039,18 @@
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return {@code true} if there is an IPv4 default route, {@code false} otherwise.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean hasIPv4DefaultRoute() {
+        return hasIpv4DefaultRoute();
+    }
+
+    /**
      * Returns true if this link has an IPv6 default route.
      *
      * @return {@code true} if there is an IPv6 default route, {@code false} otherwise.
@@ -1050,7 +1058,7 @@
      */
     @TestApi
     @SystemApi
-    public boolean hasIPv6DefaultRoute() {
+    public boolean hasIpv6DefaultRoute() {
         for (RouteInfo r : mRoutes) {
             if (r.isIPv6Default()) {
                 return true;
@@ -1060,13 +1068,25 @@
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return {@code true} if there is an IPv6 default route, {@code false} otherwise.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean hasIPv6DefaultRoute() {
+        return hasIpv6DefaultRoute();
+    }
+
+    /**
      * Returns true if this link has an IPv4 DNS server.
      *
      * @return {@code true} if there is an IPv4 DNS server, {@code false} otherwise.
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean hasIPv4DnsServer() {
+    public boolean hasIpv4DnsServer() {
         for (InetAddress ia : mDnses) {
             if (ia instanceof Inet4Address) {
                 return true;
@@ -1076,13 +1096,25 @@
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return {@code true} if there is an IPv4 DNS server, {@code false} otherwise.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean hasIPv4DnsServer() {
+        return hasIpv4DnsServer();
+    }
+
+    /**
      * Returns true if this link has an IPv6 DNS server.
      *
      * @return {@code true} if there is an IPv6 DNS server, {@code false} otherwise.
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean hasIPv6DnsServer() {
+    public boolean hasIpv6DnsServer() {
         for (InetAddress ia : mDnses) {
             if (ia instanceof Inet6Address) {
                 return true;
@@ -1092,12 +1124,24 @@
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return {@code true} if there is an IPv6 DNS server, {@code false} otherwise.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean hasIPv6DnsServer() {
+        return hasIpv6DnsServer();
+    }
+
+    /**
      * Returns true if this link has an IPv4 PCSCF server.
      *
      * @return {@code true} if there is an IPv4 PCSCF server, {@code false} otherwise.
      * @hide
      */
-    public boolean hasIPv4PcscfServer() {
+    public boolean hasIpv4PcscfServer() {
         for (InetAddress ia : mPcscfs) {
           if (ia instanceof Inet4Address) {
             return true;
@@ -1112,7 +1156,7 @@
      * @return {@code true} if there is an IPv6 PCSCF server, {@code false} otherwise.
      * @hide
      */
-    public boolean hasIPv6PcscfServer() {
+    public boolean hasIpv6PcscfServer() {
         for (InetAddress ia : mPcscfs) {
           if (ia instanceof Inet6Address) {
             return true;
@@ -1130,10 +1174,10 @@
      */
     @TestApi
     @SystemApi
-    public boolean isIPv4Provisioned() {
-        return (hasIPv4Address() &&
-                hasIPv4DefaultRoute() &&
-                hasIPv4DnsServer());
+    public boolean isIpv4Provisioned() {
+        return (hasIpv4Address()
+                && hasIpv4DefaultRoute()
+                && hasIpv4DnsServer());
     }
 
     /**
@@ -1145,13 +1189,26 @@
      */
     @TestApi
     @SystemApi
-    public boolean isIPv6Provisioned() {
-        return (hasGlobalIPv6Address() &&
-                hasIPv6DefaultRoute() &&
-                hasIPv6DnsServer());
+    public boolean isIpv6Provisioned() {
+        return (hasGlobalIpv6Address()
+                && hasIpv6DefaultRoute()
+                && hasIpv6DnsServer());
     }
 
     /**
+     * For backward compatibility.
+     * This was annotated with @UnsupportedAppUsage in P, so we can't remove the method completely
+     * just yet.
+     * @return {@code true} if the link is provisioned, {@code false} otherwise.
+     * @hide
+     */
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
+    public boolean isIPv6Provisioned() {
+        return isIpv6Provisioned();
+    }
+
+
+    /**
      * Returns true if this link is provisioned for global connectivity,
      * for at least one Internet Protocol family.
      *
@@ -1161,7 +1218,7 @@
     @TestApi
     @SystemApi
     public boolean isProvisioned() {
-        return (isIPv4Provisioned() || isIPv6Provisioned());
+        return (isIpv4Provisioned() || isIpv6Provisioned());
     }
 
     /**
@@ -1173,7 +1230,7 @@
      */
     @TestApi
     @SystemApi
-    public boolean isReachable(InetAddress ip) {
+    public boolean isReachable(@NonNull InetAddress ip) {
         final List<RouteInfo> allRoutes = getAllRoutes();
         // If we don't have a route to this IP address, it's not reachable.
         final RouteInfo bestRoute = RouteInfo.selectBestRoute(allRoutes, ip);
@@ -1185,7 +1242,7 @@
 
         if (ip instanceof Inet4Address) {
             // For IPv4, it suffices for now to simply have any address.
-            return hasIPv4AddressOnInterface(bestRoute.getInterface());
+            return hasIpv4AddressOnInterface(bestRoute.getInterface());
         } else if (ip instanceof Inet6Address) {
             if (ip.isLinkLocalAddress()) {
                 // For now, just make sure link-local destinations have
@@ -1196,7 +1253,7 @@
                 // For non-link-local destinations check that either the best route
                 // is directly connected or that some global preferred address exists.
                 // TODO: reconsider all cases (disconnected ULA networks, ...).
-                return (!bestRoute.hasGateway() || hasGlobalIPv6Address());
+                return (!bestRoute.hasGateway() || hasGlobalIpv6Address());
             }
         }
 
@@ -1211,7 +1268,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean isIdenticalInterfaceName(LinkProperties target) {
+    public boolean isIdenticalInterfaceName(@NonNull LinkProperties target) {
         return TextUtils.equals(getInterfaceName(), target.getInterfaceName());
     }
 
@@ -1223,7 +1280,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean isIdenticalAddresses(LinkProperties target) {
+    public boolean isIdenticalAddresses(@NonNull LinkProperties target) {
         Collection<InetAddress> targetAddresses = target.getAddresses();
         Collection<InetAddress> sourceAddresses = getAddresses();
         return (sourceAddresses.size() == targetAddresses.size()) ?
@@ -1238,7 +1295,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean isIdenticalDnses(LinkProperties target) {
+    public boolean isIdenticalDnses(@NonNull LinkProperties target) {
         Collection<InetAddress> targetDnses = target.getDnsServers();
         String targetDomains = target.getDomains();
         if (mDomains == null) {
@@ -1258,7 +1315,7 @@
      * @return {@code true} if both are identical, {@code false} otherwise.
      * @hide
      */
-    public boolean isIdenticalPrivateDns(LinkProperties target) {
+    public boolean isIdenticalPrivateDns(@NonNull LinkProperties target) {
         return (isPrivateDnsActive() == target.isPrivateDnsActive()
                 && TextUtils.equals(getPrivateDnsServerName(),
                 target.getPrivateDnsServerName()));
@@ -1272,7 +1329,7 @@
      * @return {@code true} if both are identical, {@code false} otherwise.
      * @hide
      */
-    public boolean isIdenticalValidatedPrivateDnses(LinkProperties target) {
+    public boolean isIdenticalValidatedPrivateDnses(@NonNull LinkProperties target) {
         Collection<InetAddress> targetDnses = target.getValidatedPrivateDnsServers();
         return (mValidatedPrivateDnses.size() == targetDnses.size())
                 ? mValidatedPrivateDnses.containsAll(targetDnses) : false;
@@ -1285,7 +1342,7 @@
      * @return {@code true} if both are identical, {@code false} otherwise.
      * @hide
      */
-    public boolean isIdenticalPcscfs(LinkProperties target) {
+    public boolean isIdenticalPcscfs(@NonNull LinkProperties target) {
         Collection<InetAddress> targetPcscfs = target.getPcscfServers();
         return (mPcscfs.size() == targetPcscfs.size()) ?
                     mPcscfs.containsAll(targetPcscfs) : false;
@@ -1299,7 +1356,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean isIdenticalRoutes(LinkProperties target) {
+    public boolean isIdenticalRoutes(@NonNull LinkProperties target) {
         Collection<RouteInfo> targetRoutes = target.getRoutes();
         return (mRoutes.size() == targetRoutes.size()) ?
                 mRoutes.containsAll(targetRoutes) : false;
@@ -1313,7 +1370,7 @@
      * @hide
      */
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)
-    public boolean isIdenticalHttpProxy(LinkProperties target) {
+    public boolean isIdenticalHttpProxy(@NonNull LinkProperties target) {
         return getHttpProxy() == null ? target.getHttpProxy() == null :
                 getHttpProxy().equals(target.getHttpProxy());
     }
@@ -1326,7 +1383,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public boolean isIdenticalStackedLinks(LinkProperties target) {
+    public boolean isIdenticalStackedLinks(@NonNull LinkProperties target) {
         if (!mStackedLinks.keySet().equals(target.mStackedLinks.keySet())) {
             return false;
         }
@@ -1347,7 +1404,7 @@
      * @return {@code true} if both are identical, {@code false} otherwise.
      * @hide
      */
-    public boolean isIdenticalMtu(LinkProperties target) {
+    public boolean isIdenticalMtu(@NonNull LinkProperties target) {
         return getMtu() == target.getMtu();
     }
 
@@ -1358,7 +1415,7 @@
      * @return {@code true} if both are identical, {@code false} otherwise.
      * @hide
      */
-    public boolean isIdenticalTcpBufferSizes(LinkProperties target) {
+    public boolean isIdenticalTcpBufferSizes(@NonNull LinkProperties target) {
         return Objects.equals(mTcpBufferSizes, target.mTcpBufferSizes);
     }
 
@@ -1369,7 +1426,7 @@
      * @return {@code true} if both are identical, {@code false} otherwise.
      * @hide
      */
-    public boolean isIdenticalNat64Prefix(LinkProperties target) {
+    public boolean isIdenticalNat64Prefix(@NonNull LinkProperties target) {
         return Objects.equals(mNat64Prefix, target.mNat64Prefix);
     }
 
@@ -1421,7 +1478,7 @@
      * @return the differences between the addresses.
      * @hide
      */
-    public CompareResult<LinkAddress> compareAddresses(LinkProperties target) {
+    public @NonNull CompareResult<LinkAddress> compareAddresses(@Nullable LinkProperties target) {
         /*
          * Duplicate the LinkAddresses into removed, we will be removing
          * address which are common between mLinkAddresses and target
@@ -1441,7 +1498,7 @@
      * @return the differences between the DNS addresses.
      * @hide
      */
-    public CompareResult<InetAddress> compareDnses(LinkProperties target) {
+    public @NonNull CompareResult<InetAddress> compareDnses(@Nullable LinkProperties target) {
         /*
          * Duplicate the InetAddresses into removed, we will be removing
          * dns address which are common between mDnses and target
@@ -1460,7 +1517,8 @@
      * @return the differences between the DNS addresses.
      * @hide
      */
-    public CompareResult<InetAddress> compareValidatedPrivateDnses(LinkProperties target) {
+    public @NonNull CompareResult<InetAddress> compareValidatedPrivateDnses(
+            @Nullable LinkProperties target) {
         return new CompareResult<>(mValidatedPrivateDnses,
                 target != null ? target.getValidatedPrivateDnsServers() : null);
     }
@@ -1473,7 +1531,7 @@
      * @return the differences between the routes.
      * @hide
      */
-    public CompareResult<RouteInfo> compareAllRoutes(LinkProperties target) {
+    public @NonNull CompareResult<RouteInfo> compareAllRoutes(@Nullable LinkProperties target) {
         /*
          * Duplicate the RouteInfos into removed, we will be removing
          * routes which are common between mRoutes and target
@@ -1491,7 +1549,8 @@
      * @return the differences between the interface names.
      * @hide
      */
-    public CompareResult<String> compareAllInterfaceNames(LinkProperties target) {
+    public @NonNull CompareResult<String> compareAllInterfaceNames(
+            @Nullable LinkProperties target) {
         /*
          * Duplicate the interface names into removed, we will be removing
          * interface names which are common between this and target
diff --git a/core/java/android/net/NattSocketKeepalive.java b/core/java/android/net/NattSocketKeepalive.java
index 84da294..b0ce0c7 100644
--- a/core/java/android/net/NattSocketKeepalive.java
+++ b/core/java/android/net/NattSocketKeepalive.java
@@ -17,10 +17,10 @@
 package android.net;
 
 import android.annotation.NonNull;
+import android.os.ParcelFileDescriptor;
 import android.os.RemoteException;
 import android.util.Log;
 
-import java.io.FileDescriptor;
 import java.net.InetAddress;
 import java.util.concurrent.Executor;
 
@@ -31,21 +31,19 @@
 
     @NonNull private final InetAddress mSource;
     @NonNull private final InetAddress mDestination;
-    @NonNull private final FileDescriptor mFd;
     private final int mResourceId;
 
     NattSocketKeepalive(@NonNull IConnectivityManager service,
             @NonNull Network network,
-            @NonNull FileDescriptor fd,
+            @NonNull ParcelFileDescriptor pfd,
             int resourceId,
             @NonNull InetAddress source,
             @NonNull InetAddress destination,
             @NonNull Executor executor,
             @NonNull Callback callback) {
-        super(service, network, executor, callback);
+        super(service, network, pfd, executor, callback);
         mSource = source;
         mDestination = destination;
-        mFd = fd;
         mResourceId = resourceId;
     }
 
@@ -53,8 +51,8 @@
     void startImpl(int intervalSec) {
         mExecutor.execute(() -> {
             try {
-                mService.startNattKeepaliveWithFd(mNetwork, mFd, mResourceId, intervalSec,
-                        mCallback,
+                mService.startNattKeepaliveWithFd(mNetwork, mPfd.getFileDescriptor(), mResourceId,
+                        intervalSec, mCallback,
                         mSource.getHostAddress(), mDestination.getHostAddress());
             } catch (RemoteException e) {
                 Log.e(TAG, "Error starting socket keepalive: ", e);
@@ -75,6 +73,5 @@
                 throw e.rethrowFromSystemServer();
             }
         });
-
     }
 }
diff --git a/core/java/android/net/Network.java b/core/java/android/net/Network.java
index 0fafdf7..3f56def 100644
--- a/core/java/android/net/Network.java
+++ b/core/java/android/net/Network.java
@@ -16,6 +16,7 @@
 
 package android.net;
 
+import android.annotation.NonNull;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.annotation.UnsupportedAppUsage;
@@ -125,7 +126,7 @@
      */
     @SystemApi
     @TestApi
-    public Network(Network that) {
+    public Network(@NonNull Network that) {
         this(that.netId, that.mPrivateDnsBypass);
     }
 
@@ -163,7 +164,7 @@
      */
     @TestApi
     @SystemApi
-    public Network getPrivateDnsBypassingCopy() {
+    public @NonNull Network getPrivateDnsBypassingCopy() {
         return new Network(netId, true);
     }
 
diff --git a/core/java/android/net/NetworkAgent.java b/core/java/android/net/NetworkAgent.java
index 273f8cd..419fa7a 100644
--- a/core/java/android/net/NetworkAgent.java
+++ b/core/java/android/net/NetworkAgent.java
@@ -488,14 +488,14 @@
      * Requests that the network hardware send the specified packet at the specified interval.
      */
     protected void startSocketKeepalive(Message msg) {
-        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_HARDWARE_UNSUPPORTED);
+        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_UNSUPPORTED);
     }
 
     /**
      * Requests that the network hardware send the specified packet at the specified interval.
      */
     protected void stopSocketKeepalive(Message msg) {
-        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_HARDWARE_UNSUPPORTED);
+        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_UNSUPPORTED);
     }
 
     /**
@@ -511,7 +511,7 @@
      * override this method.
      */
     protected void addKeepalivePacketFilter(Message msg) {
-        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_HARDWARE_UNSUPPORTED);
+        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_UNSUPPORTED);
     }
 
     /**
@@ -520,7 +520,7 @@
      * must override this method.
      */
     protected void removeKeepalivePacketFilter(Message msg) {
-        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_HARDWARE_UNSUPPORTED);
+        onSocketKeepaliveEvent(msg.arg1, SocketKeepalive.ERROR_UNSUPPORTED);
     }
 
     /**
diff --git a/core/java/android/net/NetworkCapabilities.java b/core/java/android/net/NetworkCapabilities.java
index c57ae0c..02145f2 100644
--- a/core/java/android/net/NetworkCapabilities.java
+++ b/core/java/android/net/NetworkCapabilities.java
@@ -17,6 +17,7 @@
 package android.net;
 
 import android.annotation.IntDef;
+import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
@@ -91,7 +92,7 @@
      * Set all contents of this object to the contents of a NetworkCapabilities.
      * @hide
      */
-    public void set(NetworkCapabilities nc) {
+    public void set(@NonNull NetworkCapabilities nc) {
         mNetworkCapabilities = nc.mNetworkCapabilities;
         mTransportTypes = nc.mTransportTypes;
         mLinkUpBandwidthKbps = nc.mLinkUpBandwidthKbps;
@@ -405,7 +406,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public NetworkCapabilities addCapability(@NetCapability int capability) {
+    public @NonNull NetworkCapabilities addCapability(@NetCapability int capability) {
         checkValidCapability(capability);
         mNetworkCapabilities |= 1 << capability;
         mUnwantedNetworkCapabilities &= ~(1 << capability);  // remove from unwanted capability list
@@ -442,7 +443,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public NetworkCapabilities removeCapability(@NetCapability int capability) {
+    public @NonNull NetworkCapabilities removeCapability(@NetCapability int capability) {
         checkValidCapability(capability);
         final long mask = ~(1 << capability);
         mNetworkCapabilities &= mask;
@@ -456,7 +457,8 @@
      *
      * @hide
      */
-    public NetworkCapabilities setCapability(@NetCapability int capability, boolean value) {
+    public @NonNull NetworkCapabilities setCapability(@NetCapability int capability,
+            boolean value) {
         if (value) {
             addCapability(capability);
         } else {
@@ -534,7 +536,7 @@
     }
 
     /** Note this method may result in having the same capability in wanted and unwanted lists. */
-    private void combineNetCapabilities(NetworkCapabilities nc) {
+    private void combineNetCapabilities(@NonNull NetworkCapabilities nc) {
         this.mNetworkCapabilities |= nc.mNetworkCapabilities;
         this.mUnwantedNetworkCapabilities |= nc.mUnwantedNetworkCapabilities;
     }
@@ -546,7 +548,7 @@
      *
      * @hide
      */
-    public String describeFirstNonRequestableCapability() {
+    public @Nullable String describeFirstNonRequestableCapability() {
         final long nonRequestable = (mNetworkCapabilities | mUnwantedNetworkCapabilities)
                 & NON_REQUESTABLE_CAPABILITIES;
 
@@ -558,7 +560,8 @@
         return null;
     }
 
-    private boolean satisfiedByNetCapabilities(NetworkCapabilities nc, boolean onlyImmutable) {
+    private boolean satisfiedByNetCapabilities(@NonNull NetworkCapabilities nc,
+            boolean onlyImmutable) {
         long requestedCapabilities = mNetworkCapabilities;
         long requestedUnwantedCapabilities = mUnwantedNetworkCapabilities;
         long providedCapabilities = nc.mNetworkCapabilities;
@@ -572,12 +575,12 @@
     }
 
     /** @hide */
-    public boolean equalsNetCapabilities(NetworkCapabilities nc) {
+    public boolean equalsNetCapabilities(@NonNull NetworkCapabilities nc) {
         return (nc.mNetworkCapabilities == this.mNetworkCapabilities)
                 && (nc.mUnwantedNetworkCapabilities == this.mUnwantedNetworkCapabilities);
     }
 
-    private boolean equalsNetCapabilitiesRequestable(NetworkCapabilities that) {
+    private boolean equalsNetCapabilitiesRequestable(@NonNull NetworkCapabilities that) {
         return ((this.mNetworkCapabilities & ~NON_REQUESTABLE_CAPABILITIES) ==
                 (that.mNetworkCapabilities & ~NON_REQUESTABLE_CAPABILITIES))
                 && ((this.mUnwantedNetworkCapabilities & ~NON_REQUESTABLE_CAPABILITIES) ==
@@ -713,7 +716,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public NetworkCapabilities addTransportType(@Transport int transportType) {
+    public @NonNull NetworkCapabilities addTransportType(@Transport int transportType) {
         checkValidTransportType(transportType);
         mTransportTypes |= 1 << transportType;
         setNetworkSpecifier(mNetworkSpecifier); // used for exception checking
@@ -727,7 +730,7 @@
      * @return This NetworkCapabilities instance, to facilitate chaining.
      * @hide
      */
-    public NetworkCapabilities removeTransportType(@Transport int transportType) {
+    public @NonNull NetworkCapabilities removeTransportType(@Transport int transportType) {
         checkValidTransportType(transportType);
         mTransportTypes &= ~(1 << transportType);
         setNetworkSpecifier(mNetworkSpecifier); // used for exception checking
@@ -740,7 +743,8 @@
      *
      * @hide
      */
-    public NetworkCapabilities setTransportType(@Transport int transportType, boolean value) {
+    public @NonNull NetworkCapabilities setTransportType(@Transport int transportType,
+            boolean value) {
         if (value) {
             addTransportType(transportType);
         } else {
@@ -757,7 +761,7 @@
      */
     @TestApi
     @SystemApi
-    public @Transport int[] getTransportTypes() {
+    @NonNull public @Transport int[] getTransportTypes() {
         return BitUtils.unpackBits(mTransportTypes);
     }
 
@@ -847,7 +851,7 @@
      * @param upKbps the estimated first hop upstream (device to network) bandwidth.
      * @hide
      */
-    public NetworkCapabilities setLinkUpstreamBandwidthKbps(int upKbps) {
+    public @NonNull NetworkCapabilities setLinkUpstreamBandwidthKbps(int upKbps) {
         mLinkUpBandwidthKbps = upKbps;
         return this;
     }
@@ -877,7 +881,7 @@
      * @param downKbps the estimated first hop downstream (network to device) bandwidth.
      * @hide
      */
-    public NetworkCapabilities setLinkDownstreamBandwidthKbps(int downKbps) {
+    public @NonNull NetworkCapabilities setLinkDownstreamBandwidthKbps(int downKbps) {
         mLinkDownBandwidthKbps = downKbps;
         return this;
     }
@@ -936,7 +940,7 @@
      * @return This NetworkCapabilities instance, to facilitate chaining.
      * @hide
      */
-    public NetworkCapabilities setNetworkSpecifier(NetworkSpecifier networkSpecifier) {
+    public @NonNull NetworkCapabilities setNetworkSpecifier(NetworkSpecifier networkSpecifier) {
         if (networkSpecifier != null && Long.bitCount(mTransportTypes) != 1) {
             throw new IllegalStateException("Must have a single transport specified to use " +
                     "setNetworkSpecifier");
@@ -955,20 +959,20 @@
      * @return This NetworkCapabilities instance, to facilitate chaining.
      * @hide
      */
-    public NetworkCapabilities setTransportInfo(TransportInfo transportInfo) {
+    public @NonNull NetworkCapabilities setTransportInfo(TransportInfo transportInfo) {
         mTransportInfo = transportInfo;
         return this;
     }
 
     /**
-     * Gets the optional bearer specific network specifier.
+     * Gets the optional bearer specific network specifier. May be {@code null} if not set.
      *
      * @return The optional {@link NetworkSpecifier} specifying the bearer specific network
-     *         specifier. See {@link #setNetworkSpecifier}.
+     *         specifier or {@code null}. See {@link #setNetworkSpecifier}.
      * @hide
      */
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)
-    public NetworkSpecifier getNetworkSpecifier() {
+    public @Nullable NetworkSpecifier getNetworkSpecifier() {
         return mNetworkSpecifier;
     }
 
@@ -1015,8 +1019,6 @@
     /**
      * Magic value that indicates no signal strength provided. A request specifying this value is
      * always satisfied.
-     *
-     * @hide
      */
     public static final int SIGNAL_STRENGTH_UNSPECIFIED = Integer.MIN_VALUE;
 
@@ -1024,7 +1026,7 @@
      * Signal strength. This is a signed integer, and higher values indicate better signal.
      * The exact units are bearer-dependent. For example, Wi-Fi uses RSSI.
      */
-    @UnsupportedAppUsage
+    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
     private int mSignalStrength = SIGNAL_STRENGTH_UNSPECIFIED;
 
     /**
@@ -1041,7 +1043,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public NetworkCapabilities setSignalStrength(int signalStrength) {
+    public @NonNull NetworkCapabilities setSignalStrength(int signalStrength) {
         mSignalStrength = signalStrength;
         return this;
     }
@@ -1060,9 +1062,7 @@
      * Retrieves the signal strength.
      *
      * @return The bearer-specific signal strength.
-     * @hide
      */
-    @SystemApi
     public int getSignalStrength() {
         return mSignalStrength;
     }
@@ -1120,7 +1120,7 @@
      * Convenience method to set the UIDs this network applies to to a single UID.
      * @hide
      */
-    public NetworkCapabilities setSingleUid(int uid) {
+    public @NonNull NetworkCapabilities setSingleUid(int uid) {
         final ArraySet<UidRange> identity = new ArraySet<>(1);
         identity.add(new UidRange(uid, uid));
         setUids(identity);
@@ -1132,7 +1132,7 @@
      * This makes a copy of the set so that callers can't modify it after the call.
      * @hide
      */
-    public NetworkCapabilities setUids(Set<UidRange> uids) {
+    public @NonNull NetworkCapabilities setUids(Set<UidRange> uids) {
         if (null == uids) {
             mUids = null;
         } else {
@@ -1146,7 +1146,7 @@
      * This returns a copy of the set so that callers can't modify the original object.
      * @hide
      */
-    public Set<UidRange> getUids() {
+    public @Nullable Set<UidRange> getUids() {
         return null == mUids ? null : new ArraySet<>(mUids);
     }
 
@@ -1179,7 +1179,7 @@
      * @hide
      */
     @VisibleForTesting
-    public boolean equalsUids(NetworkCapabilities nc) {
+    public boolean equalsUids(@NonNull NetworkCapabilities nc) {
         Set<UidRange> comparedUids = nc.mUids;
         if (null == comparedUids) return null == mUids;
         if (null == mUids) return false;
@@ -1212,7 +1212,7 @@
      * @see #appliesToUid
      * @hide
      */
-    public boolean satisfiedByUids(NetworkCapabilities nc) {
+    public boolean satisfiedByUids(@NonNull NetworkCapabilities nc) {
         if (null == nc.mUids || null == mUids) return true; // The network satisfies everything.
         for (UidRange requiredRange : mUids) {
             if (requiredRange.contains(nc.mEstablishingVpnAppUid)) return true;
@@ -1232,7 +1232,7 @@
      * @hide
      */
     @VisibleForTesting
-    public boolean appliesToUidRange(UidRange requiredRange) {
+    public boolean appliesToUidRange(@Nullable UidRange requiredRange) {
         if (null == mUids) return true;
         for (UidRange uidRange : mUids) {
             if (uidRange.containsRange(requiredRange)) {
@@ -1247,7 +1247,7 @@
      * NetworkCapabilities apply to.
      * nc is assumed nonnull.
      */
-    private void combineUids(NetworkCapabilities nc) {
+    private void combineUids(@NonNull NetworkCapabilities nc) {
         if (null == nc.mUids || null == mUids) {
             mUids = null;
             return;
@@ -1268,7 +1268,7 @@
      * Sets the SSID of this network.
      * @hide
      */
-    public NetworkCapabilities setSSID(String ssid) {
+    public @NonNull NetworkCapabilities setSSID(@Nullable String ssid) {
         mSSID = ssid;
         return this;
     }
@@ -1277,7 +1277,7 @@
      * Gets the SSID of this network, or null if none or unknown.
      * @hide
      */
-    public String getSSID() {
+    public @Nullable String getSSID() {
         return mSSID;
     }
 
@@ -1285,7 +1285,7 @@
      * Tests if the SSID of this network is the same as the SSID of the passed network.
      * @hide
      */
-    public boolean equalsSSID(NetworkCapabilities nc) {
+    public boolean equalsSSID(@NonNull NetworkCapabilities nc) {
         return Objects.equals(mSSID, nc.mSSID);
     }
 
@@ -1293,7 +1293,7 @@
      * Check if the SSID requirements of this object are matched by the passed object.
      * @hide
      */
-    public boolean satisfiedBySSID(NetworkCapabilities nc) {
+    public boolean satisfiedBySSID(@NonNull NetworkCapabilities nc) {
         return mSSID == null || mSSID.equals(nc.mSSID);
     }
 
@@ -1304,7 +1304,7 @@
      * equal.
      * @hide
      */
-    private void combineSSIDs(NetworkCapabilities nc) {
+    private void combineSSIDs(@NonNull NetworkCapabilities nc) {
         if (mSSID != null && !mSSID.equals(nc.mSSID)) {
             throw new IllegalStateException("Can't combine two SSIDs");
         }
@@ -1319,7 +1319,7 @@
      * both lists will never be satisfied.
      * @hide
      */
-    public void combineCapabilities(NetworkCapabilities nc) {
+    public void combineCapabilities(@NonNull NetworkCapabilities nc) {
         combineNetCapabilities(nc);
         combineTransportTypes(nc);
         combineLinkBandwidths(nc);
@@ -1359,7 +1359,7 @@
      */
     @TestApi
     @SystemApi
-    public boolean satisfiedByNetworkCapabilities(NetworkCapabilities nc) {
+    public boolean satisfiedByNetworkCapabilities(@Nullable NetworkCapabilities nc) {
         return satisfiedByNetworkCapabilities(nc, false);
     }
 
@@ -1370,7 +1370,7 @@
      *
      * @hide
      */
-    public boolean satisfiedByImmutableNetworkCapabilities(NetworkCapabilities nc) {
+    public boolean satisfiedByImmutableNetworkCapabilities(@Nullable NetworkCapabilities nc) {
         return satisfiedByNetworkCapabilities(nc, true);
     }
 
@@ -1381,7 +1381,7 @@
      *
      * @hide
      */
-    public String describeImmutableDifferences(NetworkCapabilities that) {
+    public String describeImmutableDifferences(@Nullable NetworkCapabilities that) {
         if (that == null) {
             return "other NetworkCapabilities was null";
         }
@@ -1420,7 +1420,7 @@
      *
      * @hide
      */
-    public boolean equalRequestableCapabilities(NetworkCapabilities nc) {
+    public boolean equalRequestableCapabilities(@Nullable NetworkCapabilities nc) {
         if (nc == null) return false;
         return (equalsNetCapabilitiesRequestable(nc) &&
                 equalsTransportTypes(nc) &&
@@ -1428,7 +1428,7 @@
     }
 
     @Override
-    public boolean equals(Object obj) {
+    public boolean equals(@Nullable Object obj) {
         if (obj == null || (obj instanceof NetworkCapabilities == false)) return false;
         NetworkCapabilities that = (NetworkCapabilities) obj;
         return (equalsNetCapabilities(that)
@@ -1502,7 +1502,7 @@
         };
 
     @Override
-    public String toString() {
+    public @NonNull String toString() {
         final StringBuilder sb = new StringBuilder("[");
         if (0 != mTransportTypes) {
             sb.append(" Transports: ");
@@ -1561,8 +1561,8 @@
     /**
      * @hide
      */
-    public static void appendStringRepresentationOfBitMaskToStringBuilder(StringBuilder sb,
-            long bitMask, NameOf nameFetcher, String separator) {
+    public static void appendStringRepresentationOfBitMaskToStringBuilder(@NonNull StringBuilder sb,
+            long bitMask, @NonNull NameOf nameFetcher, @NonNull String separator) {
         int bitPos = 0;
         boolean firstElementAdded = false;
         while (bitMask != 0) {
@@ -1580,7 +1580,7 @@
     }
 
     /** @hide */
-    public void writeToProto(ProtoOutputStream proto, long fieldId) {
+    public void writeToProto(@NonNull ProtoOutputStream proto, long fieldId) {
         final long token = proto.start(fieldId);
 
         for (int transport : getTransportTypes()) {
@@ -1610,7 +1610,7 @@
     /**
      * @hide
      */
-    public static String capabilityNamesOf(@NetCapability int[] capabilities) {
+    public static @NonNull String capabilityNamesOf(@Nullable @NetCapability int[] capabilities) {
         StringJoiner joiner = new StringJoiner("|");
         if (capabilities != null) {
             for (int c : capabilities) {
@@ -1623,7 +1623,7 @@
     /**
      * @hide
      */
-    public static String capabilityNameOf(@NetCapability int capability) {
+    public static @NonNull String capabilityNameOf(@NetCapability int capability) {
         switch (capability) {
             case NET_CAPABILITY_MMS:                  return "MMS";
             case NET_CAPABILITY_SUPL:                 return "SUPL";
@@ -1658,7 +1658,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public static String transportNamesOf(@Transport int[] types) {
+    public static @NonNull String transportNamesOf(@Nullable @Transport int[] types) {
         StringJoiner joiner = new StringJoiner("|");
         if (types != null) {
             for (int t : types) {
@@ -1671,7 +1671,7 @@
     /**
      * @hide
      */
-    public static String transportNameOf(@Transport int transport) {
+    public static @NonNull String transportNameOf(@Transport int transport) {
         if (!isValidTransport(transport)) {
             return "UNKNOWN";
         }
diff --git a/core/java/android/net/NetworkInfo.java b/core/java/android/net/NetworkInfo.java
index cd83531..92f105f 100644
--- a/core/java/android/net/NetworkInfo.java
+++ b/core/java/android/net/NetworkInfo.java
@@ -16,6 +16,7 @@
 
 package android.net;
 
+import android.annotation.NonNull;
 import android.annotation.UnsupportedAppUsage;
 import android.os.Parcel;
 import android.os.Parcelable;
@@ -138,7 +139,9 @@
     private int mSubtype;
     private String mTypeName;
     private String mSubtypeName;
+    @NonNull
     private State mState;
+    @NonNull
     private DetailedState mDetailedState;
     private String mReason;
     private String mExtraInfo;
@@ -451,7 +454,7 @@
      *             the device and let apps react more easily and quickly to changes.
      */
     @Deprecated
-    public DetailedState getDetailedState() {
+    public @NonNull DetailedState getDetailedState() {
         synchronized (this) {
             return mDetailedState;
         }
diff --git a/core/java/android/net/NetworkRequest.java b/core/java/android/net/NetworkRequest.java
index dcb027d..51cbed4 100644
--- a/core/java/android/net/NetworkRequest.java
+++ b/core/java/android/net/NetworkRequest.java
@@ -347,7 +347,7 @@
          * @hide
          */
         @SystemApi
-        public Builder setSignalStrength(int signalStrength) {
+        public @NonNull Builder setSignalStrength(int signalStrength) {
             mNetworkCapabilities.setSignalStrength(signalStrength);
             return this;
         }
diff --git a/core/java/android/net/NetworkUtils.java b/core/java/android/net/NetworkUtils.java
index ed410e2..5188866 100644
--- a/core/java/android/net/NetworkUtils.java
+++ b/core/java/android/net/NetworkUtils.java
@@ -177,6 +177,12 @@
     public static native byte[] resNetworkResult(FileDescriptor fd) throws ErrnoException;
 
     /**
+     * DNS resolver series jni method.
+     * Attempts to cancel the in-progress query associated with the {@code fd}.
+     */
+    public static native void resNetworkCancel(FileDescriptor fd);
+
+    /**
      * Add an entry into the ARP cache.
      */
     public static void addArpEntry(Inet4Address ipv4Addr, MacAddress ethAddr, String ifname,
diff --git a/core/java/android/net/RouteInfo.java b/core/java/android/net/RouteInfo.java
index c1c8f6e..b0239c8 100644
--- a/core/java/android/net/RouteInfo.java
+++ b/core/java/android/net/RouteInfo.java
@@ -16,6 +16,7 @@
 
 package android.net;
 
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.annotation.UnsupportedAppUsage;
@@ -112,7 +113,8 @@
      */
     @SystemApi
     @TestApi
-    public RouteInfo(IpPrefix destination, InetAddress gateway, String iface, int type) {
+    public RouteInfo(@Nullable IpPrefix destination, @Nullable InetAddress gateway,
+            @Nullable String iface, int type) {
         switch (type) {
             case RTN_UNICAST:
             case RTN_UNREACHABLE:
diff --git a/core/java/android/net/SocketKeepalive.java b/core/java/android/net/SocketKeepalive.java
index 0e768df..9d91620 100644
--- a/core/java/android/net/SocketKeepalive.java
+++ b/core/java/android/net/SocketKeepalive.java
@@ -21,8 +21,10 @@
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.os.Binder;
+import android.os.ParcelFileDescriptor;
 import android.os.RemoteException;
 
+import java.io.IOException;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.concurrent.Executor;
@@ -73,10 +75,15 @@
     /** The target socket is not idle. */
     public static final int ERROR_SOCKET_NOT_IDLE = -26;
 
-    /** The hardware does not support this request. */
-    public static final int ERROR_HARDWARE_UNSUPPORTED = -30;
+    /** The device does not support this request. */
+    public static final int ERROR_UNSUPPORTED = -30;
+    /** @hide TODO: delete when telephony code has been updated. */
+    public static final int ERROR_HARDWARE_UNSUPPORTED = ERROR_UNSUPPORTED;
     /** The hardware returned an error. */
     public static final int ERROR_HARDWARE_ERROR = -31;
+    /** The limitation of resource is reached. */
+    public static final int ERROR_INSUFFICIENT_RESOURCES = -32;
+
 
     /** @hide */
     @Retention(RetentionPolicy.SOURCE)
@@ -147,15 +154,18 @@
 
     @NonNull final IConnectivityManager mService;
     @NonNull final Network mNetwork;
+    @NonNull final ParcelFileDescriptor mPfd;
     @NonNull final Executor mExecutor;
     @NonNull final ISocketKeepaliveCallback mCallback;
     // TODO: remove slot since mCallback could be used to identify which keepalive to stop.
     @Nullable Integer mSlot;
 
     SocketKeepalive(@NonNull IConnectivityManager service, @NonNull Network network,
+            @NonNull ParcelFileDescriptor pfd,
             @NonNull Executor executor, @NonNull Callback callback) {
         mService = service;
         mNetwork = network;
+        mPfd = pfd;
         mExecutor = executor;
         mCallback = new ISocketKeepaliveCallback.Stub() {
             @Override
@@ -233,6 +243,11 @@
     @Override
     public final void close() {
         stop();
+        try {
+            mPfd.close();
+        } catch (IOException e) {
+            // Nothing much can be done.
+        }
     }
 
     /**
diff --git a/core/java/android/net/StaticIpConfiguration.java b/core/java/android/net/StaticIpConfiguration.java
index 8b264ee..565f36f 100644
--- a/core/java/android/net/StaticIpConfiguration.java
+++ b/core/java/android/net/StaticIpConfiguration.java
@@ -16,6 +16,8 @@
 
 package android.net;
 
+import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.annotation.UnsupportedAppUsage;
@@ -53,22 +55,26 @@
 public final class StaticIpConfiguration implements Parcelable {
     /** @hide */
     @UnsupportedAppUsage
+    @Nullable
     public LinkAddress ipAddress;
     /** @hide */
     @UnsupportedAppUsage
+    @Nullable
     public InetAddress gateway;
     /** @hide */
     @UnsupportedAppUsage
+    @NonNull
     public final ArrayList<InetAddress> dnsServers;
     /** @hide */
     @UnsupportedAppUsage
+    @Nullable
     public String domains;
 
     public StaticIpConfiguration() {
         dnsServers = new ArrayList<InetAddress>();
     }
 
-    public StaticIpConfiguration(StaticIpConfiguration source) {
+    public StaticIpConfiguration(@Nullable StaticIpConfiguration source) {
         this();
         if (source != null) {
             // All of these except dnsServers are immutable, so no need to make copies.
@@ -86,38 +92,38 @@
         domains = null;
     }
 
-    public LinkAddress getIpAddress() {
+    public @Nullable LinkAddress getIpAddress() {
         return ipAddress;
     }
 
-    public void setIpAddress(LinkAddress ipAddress) {
+    public void setIpAddress(@Nullable LinkAddress ipAddress) {
         this.ipAddress = ipAddress;
     }
 
-    public InetAddress getGateway() {
+    public @Nullable InetAddress getGateway() {
         return gateway;
     }
 
-    public void setGateway(InetAddress gateway) {
+    public void setGateway(@Nullable InetAddress gateway) {
         this.gateway = gateway;
     }
 
-    public List<InetAddress> getDnsServers() {
+    public @NonNull List<InetAddress> getDnsServers() {
         return dnsServers;
     }
 
-    public String getDomains() {
+    public @Nullable String getDomains() {
         return domains;
     }
 
-    public void setDomains(String newDomains) {
+    public void setDomains(@Nullable String newDomains) {
         domains = newDomains;
     }
 
     /**
      * Add a DNS server to this configuration.
      */
-    public void addDnsServer(InetAddress server) {
+    public void addDnsServer(@NonNull InetAddress server) {
         dnsServers.add(server);
     }
 
@@ -128,7 +134,7 @@
      * route to the gateway as well. This configuration is arguably invalid, but it used to work
      * in K and earlier, and other OSes appear to accept it.
      */
-    public List<RouteInfo> getRoutes(String iface) {
+    public @NonNull List<RouteInfo> getRoutes(@Nullable String iface) {
         List<RouteInfo> routes = new ArrayList<RouteInfo>(3);
         if (ipAddress != null) {
             RouteInfo connectedRoute = new RouteInfo(ipAddress, null, iface);
@@ -150,7 +156,7 @@
      * IPv6 configuration) will not be included.
      * @hide
      */
-    public LinkProperties toLinkProperties(String iface) {
+    public @NonNull LinkProperties toLinkProperties(String iface) {
         LinkProperties lp = new LinkProperties();
         lp.setInterfaceName(iface);
         if (ipAddress != null) {
diff --git a/core/java/android/net/TcpSocketKeepalive.java b/core/java/android/net/TcpSocketKeepalive.java
index 26cc8ff..436397e 100644
--- a/core/java/android/net/TcpSocketKeepalive.java
+++ b/core/java/android/net/TcpSocketKeepalive.java
@@ -17,25 +17,22 @@
 package android.net;
 
 import android.annotation.NonNull;
+import android.os.ParcelFileDescriptor;
 import android.os.RemoteException;
 import android.util.Log;
 
 import java.io.FileDescriptor;
-import java.net.Socket;
 import java.util.concurrent.Executor;
 
 /** @hide */
 final class TcpSocketKeepalive extends SocketKeepalive {
 
-    private final Socket mSocket;
-
     TcpSocketKeepalive(@NonNull IConnectivityManager service,
             @NonNull Network network,
-            @NonNull Socket socket,
+            @NonNull ParcelFileDescriptor pfd,
             @NonNull Executor executor,
             @NonNull Callback callback) {
-        super(service, network, executor, callback);
-        mSocket = socket;
+        super(service, network, pfd, executor, callback);
     }
 
     /**
@@ -57,7 +54,7 @@
     void startImpl(int intervalSec) {
         mExecutor.execute(() -> {
             try {
-                final FileDescriptor fd = mSocket.getFileDescriptor$();
+                final FileDescriptor fd = mPfd.getFileDescriptor();
                 mService.startTcpKeepalive(mNetwork, fd, intervalSec, mCallback);
             } catch (RemoteException e) {
                 Log.e(TAG, "Error starting packet keepalive: ", e);
diff --git a/core/java/android/net/apf/ApfCapabilities.java b/core/java/android/net/apf/ApfCapabilities.java
index d6023d7..17a03c7 100644
--- a/core/java/android/net/apf/ApfCapabilities.java
+++ b/core/java/android/net/apf/ApfCapabilities.java
@@ -16,6 +16,7 @@
 
 package android.net.apf;
 
+import android.annotation.NonNull;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.content.Context;
@@ -115,14 +116,14 @@
     /**
      * @return Whether the APF Filter in the device should filter out IEEE 802.3 Frames.
      */
-    public static boolean getApfDrop8023Frames(Context context) {
+    public static boolean getApfDrop8023Frames(@NonNull Context context) {
         return context.getResources().getBoolean(R.bool.config_apfDrop802_3Frames);
     }
 
     /**
      * @return An array of blacklisted EtherType, packets with EtherTypes within it will be dropped.
      */
-    public static int[] getApfEthTypeBlackList(Context context) {
+    public static @NonNull int[] getApfEthTypeBlackList(@NonNull Context context) {
         return context.getResources().getIntArray(R.array.config_apfEthTypeBlackList);
     }
 }
diff --git a/core/jni/android_net_NetUtils.cpp b/core/jni/android_net_NetUtils.cpp
index cfb2dd1..d7a981e 100644
--- a/core/jni/android_net_NetUtils.cpp
+++ b/core/jni/android_net_NetUtils.cpp
@@ -487,6 +487,11 @@
     return answer;
 }
 
+static void android_net_utils_resNetworkCancel(JNIEnv *env, jobject thiz, jobject javaFd) {
+    int fd = jniGetFDFromFileDescriptor(env, javaFd);
+    resNetworkCancel(fd);
+}
+
 static jobject android_net_utils_getTcpRepairWindow(JNIEnv *env, jobject thiz, jobject javaFd) {
     if (javaFd == NULL) {
         jniThrowNullPointerException(env, NULL);
@@ -546,6 +551,7 @@
     { "resNetworkSend", "(I[BII)Ljava/io/FileDescriptor;", (void*) android_net_utils_resNetworkSend },
     { "resNetworkQuery", "(ILjava/lang/String;III)Ljava/io/FileDescriptor;", (void*) android_net_utils_resNetworkQuery },
     { "resNetworkResult", "(Ljava/io/FileDescriptor;)[B", (void*) android_net_utils_resNetworkResult },
+    { "resNetworkCancel", "(Ljava/io/FileDescriptor;)V", (void*) android_net_utils_resNetworkCancel },
 };
 
 int register_android_net_NetworkUtils(JNIEnv* env)
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index b2ee686..2be92cd 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -988,7 +988,7 @@
 
         mUserManager = (UserManager) context.getSystemService(Context.USER_SERVICE);
 
-        mKeepaliveTracker = new KeepaliveTracker(mHandler);
+        mKeepaliveTracker = new KeepaliveTracker(mContext, mHandler);
         mNotifier = new NetworkNotificationManager(mContext, mTelephonyManager,
                 mContext.getSystemService(NotificationManager.class));
 
@@ -2174,7 +2174,7 @@
             if (VDBG) log("identical MTU - not setting");
             return;
         }
-        if (LinkProperties.isValidMtu(mtu, newLp.hasGlobalIPv6Address()) == false) {
+        if (!LinkProperties.isValidMtu(mtu, newLp.hasGlobalIpv6Address())) {
             if (mtu != 0) loge("Unexpected mtu value: " + mtu + ", " + iface);
             return;
         }
@@ -2561,19 +2561,16 @@
 
                     final boolean partialConnectivity =
                             (msg.arg1 == NETWORK_TEST_RESULT_PARTIAL_CONNECTIVITY)
-                                    // If user accepts partial connectivity network, NetworkMonitor
-                                    // will skip https probing. It will make partial connectivity
-                                    // network becomes valid. But user still need to know this
-                                    // network is limited. So, it's needed to refer to
-                                    // acceptPartialConnectivity to add
-                                    // NET_CAPABILITY_PARTIAL_CONNECTIVITY into NetworkCapabilities
-                                    // of this network. So that user can see "Limited connection"
-                                    // in the settings.
                                     || (nai.networkMisc.acceptPartialConnectivity
                                             && nai.partialConnectivity);
                     // Once a network is determined to have partial connectivity, it cannot
-                    // go back to full connectivity without a disconnect.
-                    final boolean partialConnectivityChange =
+                    // go back to full connectivity without a disconnect. This is because
+                    // NetworkMonitor can only communicate either PARTIAL_CONNECTIVITY or VALID,
+                    // but not both.
+                    // TODO: Provide multi-testResult to improve the communication between
+                    // ConnectivityService and NetworkMonitor, so that ConnectivityService could
+                    // know the real status of network.
+                    final boolean partialConnectivityChanged =
                             (partialConnectivity && !nai.partialConnectivity);
 
                     final boolean valid = (msg.arg1 == NETWORK_TEST_RESULT_VALID);
@@ -2584,17 +2581,6 @@
                         nai.captivePortalLoginNotified = true;
                         showNetworkNotification(nai, NotificationType.LOGGED_IN);
                     }
-                    // If this network has just connected and partial connectivity has just been
-                    // detected, tell NetworkMonitor if the user accepted partial connectivity on a
-                    // previous connect.
-                    if ((msg.arg1 == NETWORK_TEST_RESULT_PARTIAL_CONNECTIVITY)
-                            && nai.networkMisc.acceptPartialConnectivity) {
-                        try {
-                            nai.networkMonitor().notifyAcceptPartialConnectivity();
-                        } catch (RemoteException e) {
-                            e.rethrowFromSystemServer();
-                        }
-                    }
 
                     final String redirectUrl = (msg.obj instanceof String) ? (String) msg.obj : "";
 
@@ -2624,7 +2610,7 @@
                             mNotifier.clearNotification(nai.network.netId,
                                     NotificationType.LOST_INTERNET);
                         }
-                    } else if (partialConnectivityChange) {
+                    } else if (partialConnectivityChanged) {
                         nai.partialConnectivity = partialConnectivity;
                         updateCapabilities(nai.getCurrentScore(), nai, nai.networkCapabilities);
                     }
@@ -3378,8 +3364,11 @@
             // Tear down the network.
             teardownUnneededNetwork(nai);
         } else {
+            // Inform NetworkMonitor that partial connectivity is acceptable. This will likely
+            // result in a partial connectivity result which will be processed by
+            // maybeHandleNetworkMonitorMessage.
             try {
-                nai.networkMonitor().notifyAcceptPartialConnectivity();
+                nai.networkMonitor().setAcceptPartialConnectivity();
             } catch (RemoteException e) {
                 e.rethrowFromSystemServer();
             }
@@ -3486,8 +3475,12 @@
         return mMultinetworkPolicyTracker.getAvoidBadWifi();
     }
 
-    @Override
-    public boolean getAvoidBadWifi() {
+    /**
+     * Return whether the device should maintain continuous, working connectivity by switching away
+     * from WiFi networks having no connectivity.
+     * @see MultinetworkPolicyTracker#getAvoidBadWifi()
+     */
+    public boolean shouldAvoidBadWifi() {
         if (!checkNetworkStackPermission()) {
             throw new SecurityException("avoidBadWifi requires NETWORK_STACK permission");
         }
@@ -3587,6 +3580,9 @@
         // because we're already prompting the user to sign in.
         if (nai == null || nai.everValidated || nai.everCaptivePortalDetected
                 || !nai.networkMisc.explicitlySelected || nai.networkMisc.acceptUnvalidated
+                // TODO: Once the value of acceptPartialConnectivity is moved to IpMemoryStore,
+                // we should reevaluate how to handle acceptPartialConnectivity when network just
+                // connected.
                 || nai.networkMisc.acceptPartialConnectivity) {
             return;
         }
@@ -3594,9 +3590,7 @@
         // NetworkMonitor detects the network is partial connectivity. Need to change the design to
         // popup the notification immediately when the network is partial connectivity.
         if (nai.partialConnectivity) {
-            // Treat PARTIAL_CONNECTIVITY as NO_INTERNET temporary until Settings has been updated.
-            // TODO: Need to change back to PARTIAL_CONNECTIVITY when Settings part is merged.
-            showNetworkNotification(nai, NotificationType.NO_INTERNET);
+            showNetworkNotification(nai, NotificationType.PARTIAL_CONNECTIVITY);
         } else {
             showNetworkNotification(nai, NotificationType.NO_INTERNET);
         }
@@ -6395,6 +6389,9 @@
             // NetworkMonitor seeing the correct LinkProperties when starting.
             // TODO: pass LinkProperties to the NetworkMonitor in the notifyNetworkConnected call.
             try {
+                if (networkAgent.networkMisc.acceptPartialConnectivity) {
+                    networkAgent.networkMonitor().setAcceptPartialConnectivity();
+                }
                 networkAgent.networkMonitor().notifyNetworkConnected();
             } catch (RemoteException e) {
                 e.rethrowFromSystemServer();
@@ -6695,7 +6692,9 @@
     @Override
     public String getCaptivePortalServerUrl() {
         enforceConnectivityInternalPermission();
-        return NetworkMonitorUtils.getCaptivePortalServerHttpUrl(mContext);
+        final String defaultUrl = mContext.getResources().getString(
+                R.string.config_networkDefaultCaptivePortalServerUrl);
+        return NetworkMonitorUtils.getCaptivePortalServerHttpUrl(mContext, defaultUrl);
     }
 
     @Override
@@ -6703,7 +6702,7 @@
             ISocketKeepaliveCallback cb, String srcAddr, int srcPort, String dstAddr) {
         enforceKeepalivePermission();
         mKeepaliveTracker.startNattKeepalive(
-                getNetworkAgentInfoForNetwork(network),
+                getNetworkAgentInfoForNetwork(network), null /* fd */,
                 intervalSeconds, cb,
                 srcAddr, srcPort, dstAddr, NattSocketKeepalive.NATT_PORT);
     }
@@ -6712,7 +6711,6 @@
     public void startNattKeepaliveWithFd(Network network, FileDescriptor fd, int resourceId,
             int intervalSeconds, ISocketKeepaliveCallback cb, String srcAddr,
             String dstAddr) {
-        enforceKeepalivePermission();
         mKeepaliveTracker.startNattKeepalive(
                 getNetworkAgentInfoForNetwork(network), fd, resourceId,
                 intervalSeconds, cb,
diff --git a/services/core/java/com/android/server/connectivity/KeepaliveTracker.java b/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
index 35d6860..ce887eb 100644
--- a/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
+++ b/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
@@ -16,6 +16,7 @@
 
 package com.android.server.connectivity;
 
+import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 import static android.net.NattSocketKeepalive.NATT_PORT;
 import static android.net.NetworkAgent.CMD_ADD_KEEPALIVE_PACKET_FILTER;
 import static android.net.NetworkAgent.CMD_REMOVE_KEEPALIVE_PACKET_FILTER;
@@ -23,6 +24,7 @@
 import static android.net.NetworkAgent.CMD_STOP_SOCKET_KEEPALIVE;
 import static android.net.SocketKeepalive.BINDER_DIED;
 import static android.net.SocketKeepalive.DATA_RECEIVED;
+import static android.net.SocketKeepalive.ERROR_INSUFFICIENT_RESOURCES;
 import static android.net.SocketKeepalive.ERROR_INVALID_INTERVAL;
 import static android.net.SocketKeepalive.ERROR_INVALID_IP_ADDRESS;
 import static android.net.SocketKeepalive.ERROR_INVALID_NETWORK;
@@ -34,6 +36,7 @@
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
+import android.content.Context;
 import android.net.ISocketKeepaliveCallback;
 import android.net.KeepalivePacketData;
 import android.net.NattKeepalivePacketData;
@@ -42,7 +45,6 @@
 import android.net.SocketKeepalive.InvalidPacketException;
 import android.net.SocketKeepalive.InvalidSocketException;
 import android.net.TcpKeepalivePacketData;
-import android.net.TcpKeepalivePacketData.TcpSocketInfo;
 import android.net.util.IpUtils;
 import android.os.Binder;
 import android.os.Handler;
@@ -85,10 +87,13 @@
     private final Handler mConnectivityServiceHandler;
     @NonNull
     private final TcpKeepaliveController mTcpController;
+    @NonNull
+    private final Context mContext;
 
-    public KeepaliveTracker(Handler handler) {
+    public KeepaliveTracker(Context context, Handler handler) {
         mConnectivityServiceHandler = handler;
         mTcpController = new TcpKeepaliveController(handler);
+        mContext = context;
     }
 
     /**
@@ -102,6 +107,7 @@
         private final ISocketKeepaliveCallback mCallback;
         private final int mUid;
         private final int mPid;
+        private final boolean mPrivileged;
         private final NetworkAgentInfo mNai;
         private final int mType;
         private final FileDescriptor mFd;
@@ -109,6 +115,11 @@
         public static final int TYPE_NATT = 1;
         public static final int TYPE_TCP = 2;
 
+        // Max allowed unprivileged keepalive slots per network. Caller's permission will be
+        // enforced if number of existing keepalives reach this limit.
+        // TODO: consider making this limit configurable via resources.
+        private static final int MAX_UNPRIVILEGED_SLOTS = 3;
+
         // Keepalive slot. A small integer that identifies this keepalive among the ones handled
         // by this network.
         private int mSlot = NO_KEEPALIVE;
@@ -128,16 +139,33 @@
                 @NonNull KeepalivePacketData packet,
                 int interval,
                 int type,
-                @NonNull FileDescriptor fd) {
+                @Nullable FileDescriptor fd) throws InvalidSocketException {
             mCallback = callback;
             mPid = Binder.getCallingPid();
             mUid = Binder.getCallingUid();
+            mPrivileged = (PERMISSION_GRANTED == mContext.checkPermission(PERMISSION, mPid, mUid));
 
             mNai = nai;
             mPacket = packet;
             mInterval = interval;
             mType = type;
-            mFd = fd;
+
+            // For SocketKeepalive, a dup of fd is kept in mFd so the source port from which the
+            // keepalives are sent cannot be reused by another app even if the fd gets closed by
+            // the user. A null is acceptable here for backward compatibility of PacketKeepalive
+            // API.
+            // TODO: don't accept null fd after legacy packetKeepalive API is removed.
+            try {
+                if (fd != null) {
+                    mFd = Os.dup(fd);
+                }  else {
+                    Log.d(TAG, "uid/pid " + mUid + "/" + mPid + " calls with null fd");
+                    mFd = null;
+                }
+            } catch (ErrnoException e) {
+                Log.e(TAG, "Cannot dup fd: ", e);
+                throw new InvalidSocketException(ERROR_INVALID_SOCKET, e);
+            }
 
             try {
                 mCallback.asBinder().linkToDeath(this, 0);
@@ -168,7 +196,7 @@
                     + "->"
                     + IpUtils.addressAndPortToString(mPacket.dstAddress, mPacket.dstPort)
                     + " interval=" + mInterval
-                    + " uid=" + mUid + " pid=" + mPid
+                    + " uid=" + mUid + " pid=" + mPid + " privileged=" + mPrivileged
                     + " packetData=" + HexDump.toHexString(mPacket.getPacket())
                     + " ]";
         }
@@ -208,9 +236,27 @@
             return SUCCESS;
         }
 
+        private int checkPermission() {
+            final HashMap<Integer, KeepaliveInfo> networkKeepalives = mKeepalives.get(mNai);
+            int unprivilegedCount = 0;
+            if (networkKeepalives == null) {
+                return ERROR_INVALID_NETWORK;
+            }
+            for (KeepaliveInfo ki : networkKeepalives.values()) {
+                if (!ki.mPrivileged) {
+                    unprivilegedCount++;
+                }
+                if (unprivilegedCount >= MAX_UNPRIVILEGED_SLOTS) {
+                    return mPrivileged ? SUCCESS : ERROR_INSUFFICIENT_RESOURCES;
+                }
+            }
+            return SUCCESS;
+        }
+
         private int isValid() {
             synchronized (mNai) {
                 int error = checkInterval();
+                if (error == SUCCESS) error = checkPermission();
                 if (error == SUCCESS) error = checkNetworkConnected();
                 if (error == SUCCESS) error = checkSourceAddress();
                 return error;
@@ -273,6 +319,18 @@
                 }
             }
 
+            // Close the duplicated fd that maintains the lifecycle of socket whenever
+            // keepalive is running.
+            if (mFd != null) {
+                try {
+                    Os.close(mFd);
+                } catch (ErrnoException e) {
+                    // This should not happen since system server controls the lifecycle of fd when
+                    // keepalive offload is running.
+                    Log.wtf(TAG, "Error closing fd for keepalive " + mSlot + ": " + e);
+                }
+            }
+
             if (reason == SUCCESS) {
                 try {
                     mCallback.onStopped();
@@ -356,8 +414,9 @@
             return;
         }
         ki.stop(reason);
-        Log.d(TAG, "Stopped keepalive " + slot + " on " + networkName);
         networkKeepalives.remove(slot);
+        Log.d(TAG, "Stopped keepalive " + slot + " on " + networkName + ", "
+                + networkKeepalives.size() + " remains.");
         if (networkKeepalives.isEmpty()) {
             mKeepalives.remove(nai);
         }
@@ -390,7 +449,8 @@
             ki = mKeepalives.get(nai).get(slot);
         } catch(NullPointerException e) {}
         if (ki == null) {
-            Log.e(TAG, "Event for unknown keepalive " + slot + " on " + nai.name());
+            Log.e(TAG, "Event " + message.what + " for unknown keepalive " + slot + " on "
+                    + nai.name());
             return;
         }
 
@@ -438,6 +498,7 @@
      * {@link android.net.SocketKeepalive}.
      **/
     public void startNattKeepalive(@Nullable NetworkAgentInfo nai,
+            @Nullable FileDescriptor fd,
             int intervalSeconds,
             @NonNull ISocketKeepaliveCallback cb,
             @NonNull String srcAddrString,
@@ -466,8 +527,14 @@
             notifyErrorCallback(cb, e.error);
             return;
         }
-        KeepaliveInfo ki = new KeepaliveInfo(cb, nai, packet, intervalSeconds,
-                KeepaliveInfo.TYPE_NATT, null);
+        KeepaliveInfo ki = null;
+        try {
+            ki = new KeepaliveInfo(cb, nai, packet, intervalSeconds,
+                    KeepaliveInfo.TYPE_NATT, fd);
+        } catch (InvalidSocketException e) {
+            notifyErrorCallback(cb, ERROR_INVALID_SOCKET);
+            return;
+        }
         Log.d(TAG, "Created keepalive: " + ki.toString());
         mConnectivityServiceHandler.obtainMessage(
                 NetworkAgent.CMD_START_SOCKET_KEEPALIVE, ki).sendToTarget();
@@ -492,21 +559,21 @@
             return;
         }
 
-        TcpKeepalivePacketData packet = null;
+        final TcpKeepalivePacketData packet;
         try {
-            TcpSocketInfo tsi = TcpKeepaliveController.switchToRepairMode(fd);
-            packet = TcpKeepalivePacketData.tcpKeepalivePacket(tsi);
+            packet = TcpKeepaliveController.getTcpKeepalivePacket(fd);
         } catch (InvalidPacketException | InvalidSocketException e) {
-            try {
-                TcpKeepaliveController.switchOutOfRepairMode(fd);
-            } catch (ErrnoException e1) {
-                Log.e(TAG, "Couldn't move fd out of repair mode after failure to start keepalive");
-            }
             notifyErrorCallback(cb, e.error);
             return;
         }
-        KeepaliveInfo ki = new KeepaliveInfo(cb, nai, packet, intervalSeconds,
-                KeepaliveInfo.TYPE_TCP, fd);
+        KeepaliveInfo ki = null;
+        try {
+            ki = new KeepaliveInfo(cb, nai, packet, intervalSeconds,
+                    KeepaliveInfo.TYPE_TCP, fd);
+        } catch (InvalidSocketException e) {
+            notifyErrorCallback(cb, ERROR_INVALID_SOCKET);
+            return;
+        }
         Log.d(TAG, "Created keepalive: " + ki.toString());
         mConnectivityServiceHandler.obtainMessage(CMD_START_SOCKET_KEEPALIVE, ki).sendToTarget();
     }
@@ -541,7 +608,7 @@
         }
 
         // Forward request to old API.
-        startNattKeepalive(nai, intervalSeconds, cb, srcAddrString, srcPort,
+        startNattKeepalive(nai, fd, intervalSeconds, cb, srcAddrString, srcPort,
                 dstAddrString, dstPort);
     }
 
diff --git a/services/core/java/com/android/server/connectivity/Nat464Xlat.java b/services/core/java/com/android/server/connectivity/Nat464Xlat.java
index 2646d76..262ba7a 100644
--- a/services/core/java/com/android/server/connectivity/Nat464Xlat.java
+++ b/services/core/java/com/android/server/connectivity/Nat464Xlat.java
@@ -107,8 +107,8 @@
         // Only run clat on networks that have a global IPv6 address and don't have a native IPv4
         // address.
         LinkProperties lp = nai.linkProperties;
-        final boolean isIpv6OnlyNetwork = (lp != null) && lp.hasGlobalIPv6Address()
-                && !lp.hasIPv4Address();
+        final boolean isIpv6OnlyNetwork = (lp != null) && lp.hasGlobalIpv6Address()
+                && !lp.hasIpv4Address();
 
         // If the network tells us it doesn't use clat, respect that.
         final boolean skip464xlat = (nai.netMisc() != null) && nai.netMisc().skip464xlat;
diff --git a/services/core/java/com/android/server/connectivity/NetworkDiagnostics.java b/services/core/java/com/android/server/connectivity/NetworkDiagnostics.java
index c471f0c..948c690 100644
--- a/services/core/java/com/android/server/connectivity/NetworkDiagnostics.java
+++ b/services/core/java/com/android/server/connectivity/NetworkDiagnostics.java
@@ -34,10 +34,12 @@
 
 import com.android.internal.util.IndentingPrintWriter;
 
+import libcore.io.IoUtils;
+
 import java.io.Closeable;
 import java.io.FileDescriptor;
-import java.io.InterruptedIOException;
 import java.io.IOException;
+import java.io.InterruptedIOException;
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
@@ -48,17 +50,13 @@
 import java.net.UnknownHostException;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.TimeUnit;
-import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
-
-import libcore.io.IoUtils;
-
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 
 /**
  * NetworkDiagnostics
@@ -186,7 +184,7 @@
         // TODO: we could use mLinkProperties.isReachable(TEST_DNS6) here, because we won't set any
         // DNS servers for which isReachable() is false, but since this is diagnostic code, be extra
         // careful.
-        if (mLinkProperties.hasGlobalIPv6Address() || mLinkProperties.hasIPv6DefaultRoute()) {
+        if (mLinkProperties.hasGlobalIpv6Address() || mLinkProperties.hasIpv6DefaultRoute()) {
             mLinkProperties.addDnsServer(TEST_DNS6);
         }
 
diff --git a/services/core/java/com/android/server/connectivity/TcpKeepaliveController.java b/services/core/java/com/android/server/connectivity/TcpKeepaliveController.java
index 3e21b5b..e570ef1 100644
--- a/services/core/java/com/android/server/connectivity/TcpKeepaliveController.java
+++ b/services/core/java/com/android/server/connectivity/TcpKeepaliveController.java
@@ -16,20 +16,25 @@
 package com.android.server.connectivity;
 
 import static android.net.SocketKeepalive.DATA_RECEIVED;
-import static android.net.SocketKeepalive.ERROR_HARDWARE_UNSUPPORTED;
 import static android.net.SocketKeepalive.ERROR_INVALID_SOCKET;
 import static android.net.SocketKeepalive.ERROR_SOCKET_NOT_IDLE;
+import static android.net.SocketKeepalive.ERROR_UNSUPPORTED;
 import static android.os.MessageQueue.OnFileDescriptorEventListener.EVENT_ERROR;
 import static android.os.MessageQueue.OnFileDescriptorEventListener.EVENT_INPUT;
 import static android.system.OsConstants.ENOPROTOOPT;
 import static android.system.OsConstants.FIONREAD;
+import static android.system.OsConstants.IPPROTO_IP;
 import static android.system.OsConstants.IPPROTO_TCP;
+import static android.system.OsConstants.IP_TOS;
+import static android.system.OsConstants.IP_TTL;
 import static android.system.OsConstants.TIOCOUTQ;
 
 import android.annotation.NonNull;
 import android.net.NetworkUtils;
+import android.net.SocketKeepalive.InvalidPacketException;
 import android.net.SocketKeepalive.InvalidSocketException;
-import android.net.TcpKeepalivePacketData.TcpSocketInfo;
+import android.net.TcpKeepalivePacketData;
+import android.net.TcpKeepalivePacketDataParcelable;
 import android.net.TcpRepairWindow;
 import android.os.Handler;
 import android.os.MessageQueue;
@@ -44,7 +49,6 @@
 import com.android.server.connectivity.KeepaliveTracker.KeepaliveInfo;
 
 import java.io.FileDescriptor;
-import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.net.SocketException;
@@ -103,26 +107,30 @@
         mFdHandlerQueue = connectivityServiceHandler.getLooper().getQueue();
     }
 
+    /** Build tcp keepalive packet. */
+    public static TcpKeepalivePacketData getTcpKeepalivePacket(@NonNull FileDescriptor fd)
+            throws InvalidPacketException, InvalidSocketException {
+        try {
+            final TcpKeepalivePacketDataParcelable tcpDetails = switchToRepairMode(fd);
+            return TcpKeepalivePacketData.tcpKeepalivePacket(tcpDetails);
+        } catch (InvalidPacketException | InvalidSocketException e) {
+            switchOutOfRepairMode(fd);
+            throw e;
+        }
+    }
     /**
-     * Switch the tcp socket to repair mode and query tcp socket information.
+     * Switch the tcp socket to repair mode and query detail tcp information.
      *
-     * @param fd the fd of socket on which to use keepalive offload
-     * @return a {@link TcpKeepalivePacketData#TcpSocketInfo} object for current
+     * @param fd the fd of socket on which to use keepalive offload.
+     * @return a {@link TcpKeepalivePacketData#TcpKeepalivePacketDataParcelable} object for current
      * tcp/ip information.
      */
-    // TODO : make this private. It's far too confusing that this gets called from outside
-    // at a time that nobody can understand.
-    public static TcpSocketInfo switchToRepairMode(FileDescriptor fd)
+    private static TcpKeepalivePacketDataParcelable switchToRepairMode(FileDescriptor fd)
             throws InvalidSocketException {
         if (DBG) Log.i(TAG, "switchToRepairMode to start tcp keepalive : " + fd);
+        final TcpKeepalivePacketDataParcelable tcpDetails = new TcpKeepalivePacketDataParcelable();
         final SocketAddress srcSockAddr;
         final SocketAddress dstSockAddr;
-        final InetAddress srcAddress;
-        final InetAddress dstAddress;
-        final int srcPort;
-        final int dstPort;
-        int seq;
-        final int ack;
         final TcpRepairWindow trw;
 
         // Query source address and port.
@@ -133,8 +141,8 @@
             throw new InvalidSocketException(ERROR_INVALID_SOCKET, e);
         }
         if (srcSockAddr instanceof InetSocketAddress) {
-            srcAddress = getAddress((InetSocketAddress) srcSockAddr);
-            srcPort = getPort((InetSocketAddress) srcSockAddr);
+            tcpDetails.srcAddress = getAddress((InetSocketAddress) srcSockAddr);
+            tcpDetails.srcPort = getPort((InetSocketAddress) srcSockAddr);
         } else {
             Log.e(TAG, "Invalid or mismatched SocketAddress");
             throw new InvalidSocketException(ERROR_INVALID_SOCKET);
@@ -147,8 +155,8 @@
             throw new InvalidSocketException(ERROR_INVALID_SOCKET, e);
         }
         if (dstSockAddr instanceof InetSocketAddress) {
-            dstAddress = getAddress((InetSocketAddress) dstSockAddr);
-            dstPort = getPort((InetSocketAddress) dstSockAddr);
+            tcpDetails.dstAddress = getAddress((InetSocketAddress) dstSockAddr);
+            tcpDetails.dstPort = getPort((InetSocketAddress) dstSockAddr);
         } else {
             Log.e(TAG, "Invalid or mismatched peer SocketAddress");
             throw new InvalidSocketException(ERROR_INVALID_SOCKET);
@@ -157,34 +165,49 @@
         // Query sequence and ack number
         dropAllIncomingPackets(fd, true);
         try {
-            // Enter tcp repair mode.
+            // Switch to tcp repair mode.
             Os.setsockoptInt(fd, IPPROTO_TCP, TCP_REPAIR, TCP_REPAIR_ON);
+
             // Check if socket is idle.
             if (!isSocketIdle(fd)) {
+                Log.e(TAG, "Socket is not idle");
                 throw new InvalidSocketException(ERROR_SOCKET_NOT_IDLE);
             }
             // Query write sequence number from SEND_QUEUE.
             Os.setsockoptInt(fd, IPPROTO_TCP, TCP_REPAIR_QUEUE, TCP_SEND_QUEUE);
-            seq = Os.getsockoptInt(fd, IPPROTO_TCP, TCP_QUEUE_SEQ);
+            tcpDetails.seq = Os.getsockoptInt(fd, IPPROTO_TCP, TCP_QUEUE_SEQ);
             // Query read sequence number from RECV_QUEUE.
             Os.setsockoptInt(fd, IPPROTO_TCP, TCP_REPAIR_QUEUE, TCP_RECV_QUEUE);
-            ack = Os.getsockoptInt(fd, IPPROTO_TCP, TCP_QUEUE_SEQ);
+            tcpDetails.ack = Os.getsockoptInt(fd, IPPROTO_TCP, TCP_QUEUE_SEQ);
             // Switch to NO_QUEUE to prevent illegal socket read/write in repair mode.
             Os.setsockoptInt(fd, IPPROTO_TCP, TCP_REPAIR_QUEUE, TCP_NO_QUEUE);
             // Finally, check if socket is still idle. TODO : this check needs to move to
             // after starting polling to prevent a race.
-            if (!isSocketIdle(fd)) {
+            if (!isReceiveQueueEmpty(fd)) {
+                Log.e(TAG, "Fatal: receive queue of this socket is not empty");
                 throw new InvalidSocketException(ERROR_INVALID_SOCKET);
             }
+            if (!isSendQueueEmpty(fd)) {
+                Log.e(TAG, "Socket is not idle");
+                throw new InvalidSocketException(ERROR_SOCKET_NOT_IDLE);
+            }
 
             // Query tcp window size.
             trw = NetworkUtils.getTcpRepairWindow(fd);
+            tcpDetails.rcvWnd = trw.rcvWnd;
+            tcpDetails.rcvWndScale = trw.rcvWndScale;
+            if (tcpDetails.srcAddress.length == 4 /* V4 address length */) {
+                // Query TOS.
+                tcpDetails.tos = Os.getsockoptInt(fd, IPPROTO_IP, IP_TOS);
+                // Query TTL.
+                tcpDetails.ttl = Os.getsockoptInt(fd, IPPROTO_IP, IP_TTL);
+            }
         } catch (ErrnoException e) {
             Log.e(TAG, "Exception reading TCP state from socket", e);
             if (e.errno == ENOPROTOOPT) {
                 // ENOPROTOOPT may happen in kernel version lower than 4.8.
-                // Treat it as ERROR_HARDWARE_UNSUPPORTED.
-                throw new InvalidSocketException(ERROR_HARDWARE_UNSUPPORTED, e);
+                // Treat it as ERROR_UNSUPPORTED.
+                throw new InvalidSocketException(ERROR_UNSUPPORTED, e);
             } else {
                 throw new InvalidSocketException(ERROR_INVALID_SOCKET, e);
             }
@@ -194,10 +217,9 @@
 
         // Keepalive sequence number is last sequence number - 1. If it couldn't be retrieved,
         // then it must be set to -1, so decrement in all cases.
-        seq = seq - 1;
+        tcpDetails.seq = tcpDetails.seq - 1;
 
-        return new TcpSocketInfo(srcAddress, srcPort, dstAddress, dstPort, seq, ack, trw.rcvWnd,
-                trw.rcvWndScale);
+        return tcpDetails;
     }
 
     /**
@@ -205,10 +227,13 @@
      *
      * @param fd the fd of socket to switch back to normal.
      */
-    // TODO : make this private.
-    public static void switchOutOfRepairMode(@NonNull final FileDescriptor fd)
-            throws ErrnoException {
-        Os.setsockoptInt(fd, IPPROTO_TCP, TCP_REPAIR, TCP_REPAIR_OFF);
+    private static void switchOutOfRepairMode(@NonNull final FileDescriptor fd) {
+        try {
+            Os.setsockoptInt(fd, IPPROTO_TCP, TCP_REPAIR, TCP_REPAIR_OFF);
+        } catch (ErrnoException e) {
+            Log.e(TAG, "Cannot switch socket out of repair mode", e);
+            // Well, there is not much to do here to recover
+        }
     }
 
     /**
@@ -262,17 +287,12 @@
             mListeners.remove(slot);
         }
         mFdHandlerQueue.removeOnFileDescriptorEventListener(fd);
-        try {
-            if (DBG) Log.d(TAG, "Moving socket out of repair mode for stop : " + fd);
-            switchOutOfRepairMode(fd);
-        } catch (ErrnoException e) {
-            Log.e(TAG, "Cannot switch socket out of repair mode", e);
-            // Well, there is not much to do here to recover
-        }
+        if (DBG) Log.d(TAG, "Moving socket out of repair mode for stop : " + fd);
+        switchOutOfRepairMode(fd);
     }
 
-    private static InetAddress getAddress(InetSocketAddress inetAddr) {
-        return inetAddr.getAddress();
+    private static byte [] getAddress(InetSocketAddress inetAddr) {
+        return inetAddr.getAddress().getAddress();
     }
 
     private static int getPort(InetSocketAddress inetAddr) {
diff --git a/tests/net/java/android/net/LinkAddressTest.java b/tests/net/java/android/net/LinkAddressTest.java
index be7bd1b..d462441 100644
--- a/tests/net/java/android/net/LinkAddressTest.java
+++ b/tests/net/java/android/net/LinkAddressTest.java
@@ -81,14 +81,14 @@
         assertEquals(25, address.getPrefixLength());
         assertEquals(0, address.getFlags());
         assertEquals(RT_SCOPE_UNIVERSE, address.getScope());
-        assertTrue(address.isIPv4());
+        assertTrue(address.isIpv4());
 
         address = new LinkAddress(V6_ADDRESS, 127);
         assertEquals(V6_ADDRESS, address.getAddress());
         assertEquals(127, address.getPrefixLength());
         assertEquals(0, address.getFlags());
         assertEquals(RT_SCOPE_UNIVERSE, address.getScope());
-        assertTrue(address.isIPv6());
+        assertTrue(address.isIpv6());
 
         // Nonsensical flags/scopes or combinations thereof are acceptable.
         address = new LinkAddress(V6 + "/64", IFA_F_DEPRECATED | IFA_F_PERMANENT, RT_SCOPE_LINK);
@@ -96,14 +96,14 @@
         assertEquals(64, address.getPrefixLength());
         assertEquals(IFA_F_DEPRECATED | IFA_F_PERMANENT, address.getFlags());
         assertEquals(RT_SCOPE_LINK, address.getScope());
-        assertTrue(address.isIPv6());
+        assertTrue(address.isIpv6());
 
         address = new LinkAddress(V4 + "/23", 123, 456);
         assertEquals(V4_ADDRESS, address.getAddress());
         assertEquals(23, address.getPrefixLength());
         assertEquals(123, address.getFlags());
         assertEquals(456, address.getScope());
-        assertTrue(address.isIPv4());
+        assertTrue(address.isIpv4());
 
         // InterfaceAddress doesn't have a constructor. Fetch some from an interface.
         List<InterfaceAddress> addrs = NetworkInterface.getByName("lo").getInterfaceAddresses();
diff --git a/tests/net/java/android/net/LinkPropertiesTest.java b/tests/net/java/android/net/LinkPropertiesTest.java
index 9a7d487..4177291 100644
--- a/tests/net/java/android/net/LinkPropertiesTest.java
+++ b/tests/net/java/android/net/LinkPropertiesTest.java
@@ -405,8 +405,8 @@
         LinkProperties lp = new LinkProperties();
 
         // No addresses.
-        assertFalse(lp.hasIPv4Address());
-        assertFalse(lp.hasGlobalIPv6Address());
+        assertFalse(lp.hasIpv4Address());
+        assertFalse(lp.hasGlobalIpv6Address());
 
         // Addresses on stacked links don't count.
         LinkProperties stacked = new LinkProperties();
@@ -414,53 +414,53 @@
         lp.addStackedLink(stacked);
         stacked.addLinkAddress(LINKADDRV4);
         stacked.addLinkAddress(LINKADDRV6);
-        assertTrue(stacked.hasIPv4Address());
-        assertTrue(stacked.hasGlobalIPv6Address());
-        assertFalse(lp.hasIPv4Address());
-        assertFalse(lp.hasGlobalIPv6Address());
+        assertTrue(stacked.hasIpv4Address());
+        assertTrue(stacked.hasGlobalIpv6Address());
+        assertFalse(lp.hasIpv4Address());
+        assertFalse(lp.hasGlobalIpv6Address());
         lp.removeStackedLink("stacked");
-        assertFalse(lp.hasIPv4Address());
-        assertFalse(lp.hasGlobalIPv6Address());
+        assertFalse(lp.hasIpv4Address());
+        assertFalse(lp.hasGlobalIpv6Address());
 
         // Addresses on the base link.
-        // Check the return values of hasIPvXAddress and ensure the add/remove methods return true
+        // Check the return values of hasIpvXAddress and ensure the add/remove methods return true
         // iff something changes.
         assertEquals(0, lp.getLinkAddresses().size());
         assertTrue(lp.addLinkAddress(LINKADDRV6));
         assertEquals(1, lp.getLinkAddresses().size());
-        assertFalse(lp.hasIPv4Address());
-        assertTrue(lp.hasGlobalIPv6Address());
+        assertFalse(lp.hasIpv4Address());
+        assertTrue(lp.hasGlobalIpv6Address());
 
         assertTrue(lp.removeLinkAddress(LINKADDRV6));
         assertEquals(0, lp.getLinkAddresses().size());
 
         assertTrue(lp.addLinkAddress(LINKADDRV6LINKLOCAL));
         assertEquals(1, lp.getLinkAddresses().size());
-        assertFalse(lp.hasGlobalIPv6Address());
+        assertFalse(lp.hasGlobalIpv6Address());
 
         assertTrue(lp.addLinkAddress(LINKADDRV4));
         assertEquals(2, lp.getLinkAddresses().size());
-        assertTrue(lp.hasIPv4Address());
-        assertFalse(lp.hasGlobalIPv6Address());
+        assertTrue(lp.hasIpv4Address());
+        assertFalse(lp.hasGlobalIpv6Address());
 
         assertTrue(lp.addLinkAddress(LINKADDRV6));
         assertEquals(3, lp.getLinkAddresses().size());
-        assertTrue(lp.hasIPv4Address());
-        assertTrue(lp.hasGlobalIPv6Address());
+        assertTrue(lp.hasIpv4Address());
+        assertTrue(lp.hasGlobalIpv6Address());
 
         assertTrue(lp.removeLinkAddress(LINKADDRV6LINKLOCAL));
         assertEquals(2, lp.getLinkAddresses().size());
-        assertTrue(lp.hasIPv4Address());
-        assertTrue(lp.hasGlobalIPv6Address());
+        assertTrue(lp.hasIpv4Address());
+        assertTrue(lp.hasGlobalIpv6Address());
 
         // Adding an address twice has no effect.
         // Removing an address that's not present has no effect.
         assertFalse(lp.addLinkAddress(LINKADDRV4));
         assertEquals(2, lp.getLinkAddresses().size());
-        assertTrue(lp.hasIPv4Address());
+        assertTrue(lp.hasIpv4Address());
         assertTrue(lp.removeLinkAddress(LINKADDRV4));
         assertEquals(1, lp.getLinkAddresses().size());
-        assertFalse(lp.hasIPv4Address());
+        assertFalse(lp.hasIpv4Address());
         assertFalse(lp.removeLinkAddress(LINKADDRV4));
         assertEquals(1, lp.getLinkAddresses().size());
 
@@ -546,8 +546,8 @@
         assertFalse("v4only:addr+dns", lp4.isProvisioned());
         lp4.addRoute(new RouteInfo(GATEWAY1));
         assertTrue("v4only:addr+dns+route", lp4.isProvisioned());
-        assertTrue("v4only:addr+dns+route", lp4.isIPv4Provisioned());
-        assertFalse("v4only:addr+dns+route", lp4.isIPv6Provisioned());
+        assertTrue("v4only:addr+dns+route", lp4.isIpv4Provisioned());
+        assertFalse("v4only:addr+dns+route", lp4.isIpv6Provisioned());
 
         LinkProperties lp6 = new LinkProperties();
         assertFalse("v6only:empty", lp6.isProvisioned());
@@ -558,11 +558,11 @@
         lp6.addRoute(new RouteInfo(GATEWAY61));
         assertFalse("v6only:fe80+dns+route", lp6.isProvisioned());
         lp6.addLinkAddress(LINKADDRV6);
-        assertTrue("v6only:fe80+global+dns+route", lp6.isIPv6Provisioned());
+        assertTrue("v6only:fe80+global+dns+route", lp6.isIpv6Provisioned());
         assertTrue("v6only:fe80+global+dns+route", lp6.isProvisioned());
         lp6.removeLinkAddress(LINKADDRV6LINKLOCAL);
-        assertFalse("v6only:global+dns+route", lp6.isIPv4Provisioned());
-        assertTrue("v6only:global+dns+route", lp6.isIPv6Provisioned());
+        assertFalse("v6only:global+dns+route", lp6.isIpv4Provisioned());
+        assertTrue("v6only:global+dns+route", lp6.isIpv6Provisioned());
         assertTrue("v6only:global+dns+route", lp6.isProvisioned());
 
         LinkProperties lp46 = new LinkProperties();
@@ -572,12 +572,12 @@
         lp46.addDnsServer(DNS6);
         assertFalse("dualstack:missing-routes", lp46.isProvisioned());
         lp46.addRoute(new RouteInfo(GATEWAY1));
-        assertTrue("dualstack:v4-provisioned", lp46.isIPv4Provisioned());
-        assertFalse("dualstack:v4-provisioned", lp46.isIPv6Provisioned());
+        assertTrue("dualstack:v4-provisioned", lp46.isIpv4Provisioned());
+        assertFalse("dualstack:v4-provisioned", lp46.isIpv6Provisioned());
         assertTrue("dualstack:v4-provisioned", lp46.isProvisioned());
         lp46.addRoute(new RouteInfo(GATEWAY61));
-        assertTrue("dualstack:both-provisioned", lp46.isIPv4Provisioned());
-        assertTrue("dualstack:both-provisioned", lp46.isIPv6Provisioned());
+        assertTrue("dualstack:both-provisioned", lp46.isIpv4Provisioned());
+        assertTrue("dualstack:both-provisioned", lp46.isIpv6Provisioned());
         assertTrue("dualstack:both-provisioned", lp46.isProvisioned());
 
         // A link with an IPv6 address and default route, but IPv4 DNS server.
@@ -585,8 +585,8 @@
         mixed.addLinkAddress(LINKADDRV6);
         mixed.addDnsServer(DNS1);
         mixed.addRoute(new RouteInfo(GATEWAY61));
-        assertFalse("mixed:addr6+route6+dns4", mixed.isIPv4Provisioned());
-        assertFalse("mixed:addr6+route6+dns4", mixed.isIPv6Provisioned());
+        assertFalse("mixed:addr6+route6+dns4", mixed.isIpv4Provisioned());
+        assertFalse("mixed:addr6+route6+dns4", mixed.isIpv6Provisioned());
         assertFalse("mixed:addr6+route6+dns4", mixed.isProvisioned());
     }
 
@@ -617,16 +617,16 @@
         v6lp.addLinkAddress(LINKADDRV6);
         v6lp.addRoute(new RouteInfo(GATEWAY61));
         v6lp.addDnsServer(DNS6);
-        assertFalse(v6lp.isIPv4Provisioned());
-        assertTrue(v6lp.isIPv6Provisioned());
+        assertFalse(v6lp.isIpv4Provisioned());
+        assertTrue(v6lp.isIpv6Provisioned());
         assertTrue(v6lp.isProvisioned());
 
         LinkProperties v46lp = new LinkProperties(v6lp);
         v46lp.addLinkAddress(LINKADDRV4);
         v46lp.addRoute(new RouteInfo(GATEWAY1));
         v46lp.addDnsServer(DNS1);
-        assertTrue(v46lp.isIPv4Provisioned());
-        assertTrue(v46lp.isIPv6Provisioned());
+        assertTrue(v46lp.isIpv4Provisioned());
+        assertTrue(v46lp.isIpv6Provisioned());
         assertTrue(v46lp.isProvisioned());
 
         assertEquals(ProvisioningChange.STILL_PROVISIONED,
diff --git a/tests/net/java/android/net/TcpKeepalivePacketDataTest.java b/tests/net/java/android/net/TcpKeepalivePacketDataTest.java
index 1f2dd27..e0b7227 100644
--- a/tests/net/java/android/net/TcpKeepalivePacketDataTest.java
+++ b/tests/net/java/android/net/TcpKeepalivePacketDataTest.java
@@ -21,12 +21,9 @@
 import static org.junit.Assert.fail;
 
 import android.net.SocketKeepalive.InvalidPacketException;
-import android.net.TcpKeepalivePacketData.TcpSocketInfo;
 
 import com.android.internal.util.TestUtils;
 
-import libcore.net.InetAddressUtils;
-
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -37,52 +34,69 @@
 
 @RunWith(JUnit4.class)
 public final class TcpKeepalivePacketDataTest {
+    private static final byte[] IPV4_KEEPALIVE_SRC_ADDR = {10, 0, 0, 1};
+    private static final byte[] IPV4_KEEPALIVE_DST_ADDR = {10, 0, 0, 5};
 
     @Before
     public void setUp() {}
 
     @Test
-    public void testV4TcpKeepalivePacket() {
-        final InetAddress srcAddr = InetAddressUtils.parseNumericAddress("192.168.0.1");
-        final InetAddress dstAddr = InetAddressUtils.parseNumericAddress("192.168.0.10");
+    public void testV4TcpKeepalivePacket() throws Exception {
         final int srcPort = 1234;
         final int dstPort = 4321;
         final int seq = 0x11111111;
         final int ack = 0x22222222;
         final int wnd = 8000;
         final int wndScale = 2;
+        final int tos = 4;
+        final int ttl = 64;
         TcpKeepalivePacketData resultData = null;
-        TcpSocketInfo testInfo = new TcpSocketInfo(
-                srcAddr, srcPort, dstAddr, dstPort, seq, ack, wnd, wndScale);
+        final TcpKeepalivePacketDataParcelable testInfo = new TcpKeepalivePacketDataParcelable();
+        testInfo.srcAddress = IPV4_KEEPALIVE_SRC_ADDR;
+        testInfo.srcPort = srcPort;
+        testInfo.dstAddress = IPV4_KEEPALIVE_DST_ADDR;
+        testInfo.dstPort = dstPort;
+        testInfo.seq = seq;
+        testInfo.ack = ack;
+        testInfo.rcvWnd = wnd;
+        testInfo.rcvWndScale = wndScale;
+        testInfo.tos = tos;
+        testInfo.ttl = ttl;
         try {
             resultData = TcpKeepalivePacketData.tcpKeepalivePacket(testInfo);
         } catch (InvalidPacketException e) {
             fail("InvalidPacketException: " + e);
         }
 
-        assertEquals(testInfo.srcAddress, resultData.srcAddress);
-        assertEquals(testInfo.dstAddress, resultData.dstAddress);
+        assertEquals(InetAddress.getByAddress(testInfo.srcAddress), resultData.srcAddress);
+        assertEquals(InetAddress.getByAddress(testInfo.dstAddress), resultData.dstAddress);
         assertEquals(testInfo.srcPort, resultData.srcPort);
         assertEquals(testInfo.dstPort, resultData.dstPort);
         assertEquals(testInfo.seq, resultData.tcpSeq);
         assertEquals(testInfo.ack, resultData.tcpAck);
+        assertEquals(testInfo.rcvWnd, resultData.tcpWnd);
         assertEquals(testInfo.rcvWndScale, resultData.tcpWndScale);
+        assertEquals(testInfo.tos, resultData.ipTos);
+        assertEquals(testInfo.ttl, resultData.ipTtl);
 
         TestUtils.assertParcelingIsLossless(resultData, TcpKeepalivePacketData.CREATOR);
 
         final byte[] packet = resultData.getPacket();
-        // IP version and TOS.
-        ByteBuffer buf = ByteBuffer.wrap(packet);
-        assertEquals(buf.getShort(), 0x4500);
+        // IP version and IHL
+        assertEquals(packet[0], 0x45);
+        // TOS
+        assertEquals(packet[1], tos);
+        // TTL
+        assertEquals(packet[8], ttl);
         // Source IP address.
         byte[] ip = new byte[4];
-        buf = ByteBuffer.wrap(packet, 12, 4);
+        ByteBuffer buf = ByteBuffer.wrap(packet, 12, 4);
         buf.get(ip);
-        assertArrayEquals(ip, srcAddr.getAddress());
+        assertArrayEquals(ip, IPV4_KEEPALIVE_SRC_ADDR);
         // Destination IP address.
         buf = ByteBuffer.wrap(packet, 16, 4);
         buf.get(ip);
-        assertArrayEquals(ip, dstAddr.getAddress());
+        assertArrayEquals(ip, IPV4_KEEPALIVE_DST_ADDR);
 
         buf = ByteBuffer.wrap(packet, 20, 12);
         // Source port.
@@ -102,25 +116,38 @@
 
     @Test
     public void testParcel() throws Exception {
-        final InetAddress srcAddr = InetAddresses.parseNumericAddress("192.168.0.1");
-        final InetAddress dstAddr = InetAddresses.parseNumericAddress("192.168.0.10");
         final int srcPort = 1234;
         final int dstPort = 4321;
         final int sequence = 0x11111111;
         final int ack = 0x22222222;
         final int wnd = 48_000;
         final int wndScale = 2;
+        final int tos = 4;
+        final int ttl = 64;
+        final TcpKeepalivePacketDataParcelable testInfo = new TcpKeepalivePacketDataParcelable();
+        testInfo.srcAddress = IPV4_KEEPALIVE_SRC_ADDR;
+        testInfo.srcPort = srcPort;
+        testInfo.dstAddress = IPV4_KEEPALIVE_DST_ADDR;
+        testInfo.dstPort = dstPort;
+        testInfo.seq = sequence;
+        testInfo.ack = ack;
+        testInfo.rcvWnd = wnd;
+        testInfo.rcvWndScale = wndScale;
+        testInfo.tos = tos;
+        testInfo.ttl = ttl;
         TcpKeepalivePacketData testData = null;
         TcpKeepalivePacketDataParcelable resultData = null;
-        TcpSocketInfo testInfo = new TcpSocketInfo(
-                srcAddr, srcPort, dstAddr, dstPort, sequence, ack, wnd, wndScale);
         testData = TcpKeepalivePacketData.tcpKeepalivePacket(testInfo);
         resultData = testData.toStableParcelable();
-        assertArrayEquals(resultData.srcAddress, srcAddr.getAddress());
-        assertArrayEquals(resultData.dstAddress, dstAddr.getAddress());
+        assertArrayEquals(resultData.srcAddress, IPV4_KEEPALIVE_SRC_ADDR);
+        assertArrayEquals(resultData.dstAddress, IPV4_KEEPALIVE_DST_ADDR);
         assertEquals(resultData.srcPort, srcPort);
         assertEquals(resultData.dstPort, dstPort);
         assertEquals(resultData.seq, sequence);
         assertEquals(resultData.ack, ack);
+        assertEquals(resultData.rcvWnd, wnd);
+        assertEquals(resultData.rcvWndScale, wndScale);
+        assertEquals(resultData.tos, tos);
+        assertEquals(resultData.ttl, ttl);
     }
 }
diff --git a/tests/net/java/com/android/server/ConnectivityServiceTest.java b/tests/net/java/com/android/server/ConnectivityServiceTest.java
index 3263ef9..1151214 100644
--- a/tests/net/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/net/java/com/android/server/ConnectivityServiceTest.java
@@ -144,12 +144,14 @@
 import android.os.Looper;
 import android.os.Message;
 import android.os.Parcel;
+import android.os.ParcelFileDescriptor;
 import android.os.Parcelable;
 import android.os.Process;
 import android.os.RemoteException;
 import android.os.SystemClock;
 import android.os.UserHandle;
 import android.provider.Settings;
+import android.system.Os;
 import android.test.mock.MockContentResolver;
 import android.text.TextUtils;
 import android.util.ArraySet;
@@ -188,6 +190,8 @@
 import org.mockito.Spy;
 import org.mockito.stubbing.Answer;
 
+import java.io.IOException;
+import java.net.DatagramSocket;
 import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
@@ -421,7 +425,7 @@
         private final ConditionVariable mPreventReconnectReceived = new ConditionVariable();
         private int mScore;
         private NetworkAgent mNetworkAgent;
-        private int mStartKeepaliveError = SocketKeepalive.ERROR_HARDWARE_UNSUPPORTED;
+        private int mStartKeepaliveError = SocketKeepalive.ERROR_UNSUPPORTED;
         private int mStopKeepaliveError = SocketKeepalive.NO_KEEPALIVE;
         private Integer mExpectedKeepaliveSlot = null;
         // Contains the redirectUrl from networkStatus(). Before reading, wait for
@@ -495,7 +499,7 @@
             try {
                 doAnswer(validateAnswer).when(mNetworkMonitor).notifyNetworkConnected();
                 doAnswer(validateAnswer).when(mNetworkMonitor).forceReevaluation(anyInt());
-                doAnswer(validateAnswer).when(mNetworkMonitor).notifyAcceptPartialConnectivity();
+                doAnswer(validateAnswer).when(mNetworkMonitor).setAcceptPartialConnectivity();
             } catch (RemoteException e) {
                 fail(e.getMessage());
             }
@@ -2550,7 +2554,7 @@
         verifyActiveNetwork(TRANSPORT_CELLULAR);
     }
 
-    // TODO: deflake and re-enable
+    // TODO(b/128426024): deflake and re-enable
     // @Test
     public void testPartialConnectivity() {
         // Register network callback.
@@ -2585,7 +2589,7 @@
         waitForIdle();
         try {
             verify(mWiFiNetworkAgent.mNetworkMonitor,
-                    timeout(TIMEOUT_MS).times(1)).notifyAcceptPartialConnectivity();
+                    timeout(TIMEOUT_MS).times(1)).setAcceptPartialConnectivity();
         } catch (RemoteException e) {
             fail(e.getMessage());
         }
@@ -2641,7 +2645,7 @@
         waitForIdle();
         try {
             verify(mWiFiNetworkAgent.mNetworkMonitor,
-                    timeout(TIMEOUT_MS).times(1)).notifyAcceptPartialConnectivity();
+                    timeout(TIMEOUT_MS).times(1)).setAcceptPartialConnectivity();
         } catch (RemoteException e) {
             fail(e.getMessage());
         }
@@ -4032,6 +4036,7 @@
         runTestWithSerialExecutors(executor -> {
             try {
                 doTestNattSocketKeepalivesWithExecutor(executor);
+                doTestNattSocketKeepalivesFdWithExecutor(executor);
             } catch (Exception e) {
                 fail(e.getMessage());
             }
@@ -4041,6 +4046,8 @@
     private void doTestNattSocketKeepalivesWithExecutor(Executor executor) throws Exception {
         // TODO: 1. Move this outside of ConnectivityServiceTest.
         //       2. Make test to verify that Nat-T keepalive socket is created by IpSecService.
+        //       3. Mock ipsec service.
+        //       4. Find a free port instead of a fixed port.
         final int srcPort = 12345;
         final InetAddress myIPv4 = InetAddress.getByName("192.0.2.129");
         final InetAddress notMyIPv4 = InetAddress.getByName("192.0.2.35");
@@ -4065,89 +4072,106 @@
         Network myNet = connectKeepaliveNetwork(lp);
 
         TestSocketKeepaliveCallback callback = new TestSocketKeepaliveCallback(executor);
-        SocketKeepalive ka;
 
         // Attempt to start keepalives with invalid parameters and check for errors.
         // Invalid network.
-        ka = mCm.createSocketKeepalive(notMyNet, testSocket, myIPv4, dstIPv4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_NETWORK);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                notMyNet, testSocket, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_NETWORK);
+        }
 
         // Invalid interval.
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv4, dstIPv4, executor, callback);
-        ka.start(invalidKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_INTERVAL);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(invalidKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_INTERVAL);
+        }
 
         // Invalid destination.
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv4, dstIPv6, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv4, dstIPv6, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+        }
 
         // Invalid source;
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv6, dstIPv4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv6, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+        }
 
         // NAT-T is only supported for IPv4.
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv6, dstIPv6, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv6, dstIPv6, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+        }
 
         // Sanity check before testing started keepalive.
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv4, dstIPv4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_HARDWARE_UNSUPPORTED);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_UNSUPPORTED);
+        }
 
         // Check that a started keepalive can be stopped.
         mWiFiNetworkAgent.setStartKeepaliveError(SocketKeepalive.SUCCESS);
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv4, dstIPv4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectStarted();
-        mWiFiNetworkAgent.setStopKeepaliveError(SocketKeepalive.SUCCESS);
-        ka.stop();
-        callback.expectStopped();
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectStarted();
+            mWiFiNetworkAgent.setStopKeepaliveError(SocketKeepalive.SUCCESS);
+            ka.stop();
+            callback.expectStopped();
 
-        // Check that keepalive could be restarted.
-        ka.start(validKaInterval);
-        callback.expectStarted();
-        ka.stop();
-        callback.expectStopped();
+            // Check that keepalive could be restarted.
+            ka.start(validKaInterval);
+            callback.expectStarted();
+            ka.stop();
+            callback.expectStopped();
 
-        // Check that keepalive can be restarted without waiting for callback.
-        ka.start(validKaInterval);
-        callback.expectStarted();
-        ka.stop();
-        ka.start(validKaInterval);
-        callback.expectStopped();
-        callback.expectStarted();
-        ka.stop();
-        callback.expectStopped();
+            // Check that keepalive can be restarted without waiting for callback.
+            ka.start(validKaInterval);
+            callback.expectStarted();
+            ka.stop();
+            ka.start(validKaInterval);
+            callback.expectStopped();
+            callback.expectStarted();
+            ka.stop();
+            callback.expectStopped();
+        }
 
         // Check that deleting the IP address stops the keepalive.
         LinkProperties bogusLp = new LinkProperties(lp);
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv4, dstIPv4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectStarted();
-        bogusLp.removeLinkAddress(new LinkAddress(myIPv4, 25));
-        bogusLp.addLinkAddress(new LinkAddress(notMyIPv4, 25));
-        mWiFiNetworkAgent.sendLinkProperties(bogusLp);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
-        mWiFiNetworkAgent.sendLinkProperties(lp);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectStarted();
+            bogusLp.removeLinkAddress(new LinkAddress(myIPv4, 25));
+            bogusLp.addLinkAddress(new LinkAddress(notMyIPv4, 25));
+            mWiFiNetworkAgent.sendLinkProperties(bogusLp);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+            mWiFiNetworkAgent.sendLinkProperties(lp);
+        }
 
         // Check that a started keepalive is stopped correctly when the network disconnects.
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv4, dstIPv4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectStarted();
-        mWiFiNetworkAgent.disconnect();
-        waitFor(mWiFiNetworkAgent.getDisconnectedCV());
-        callback.expectError(SocketKeepalive.ERROR_INVALID_NETWORK);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectStarted();
+            mWiFiNetworkAgent.disconnect();
+            waitFor(mWiFiNetworkAgent.getDisconnectedCV());
+            callback.expectError(SocketKeepalive.ERROR_INVALID_NETWORK);
 
-        // ... and that stopping it after that has no adverse effects.
-        waitForIdle();
-        final Network myNetAlias = myNet;
-        assertNull(mCm.getNetworkCapabilities(myNetAlias));
-        ka.stop();
-        callback.assertNoCallback();
+            // ... and that stopping it after that has no adverse effects.
+            waitForIdle();
+            final Network myNetAlias = myNet;
+            assertNull(mCm.getNetworkCapabilities(myNetAlias));
+            ka.stop();
+            callback.assertNoCallback();
+        }
 
         // Reconnect.
         myNet = connectKeepaliveNetwork(lp);
@@ -4155,27 +4179,30 @@
 
         // Check that keepalive slots start from 1 and increment. The first one gets slot 1.
         mWiFiNetworkAgent.setExpectedKeepaliveSlot(1);
-        ka = mCm.createSocketKeepalive(myNet, testSocket, myIPv4, dstIPv4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectStarted();
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+                myNet, testSocket, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectStarted();
 
-        // The second one gets slot 2.
-        mWiFiNetworkAgent.setExpectedKeepaliveSlot(2);
-        final UdpEncapsulationSocket testSocket2 = mIpSec.openUdpEncapsulationSocket(6789);
-        TestSocketKeepaliveCallback callback2 = new TestSocketKeepaliveCallback(executor);
-        SocketKeepalive ka2 =
-                mCm.createSocketKeepalive(myNet, testSocket2, myIPv4, dstIPv4, executor, callback2);
-        ka2.start(validKaInterval);
-        callback2.expectStarted();
+            // The second one gets slot 2.
+            mWiFiNetworkAgent.setExpectedKeepaliveSlot(2);
+            final UdpEncapsulationSocket testSocket2 = mIpSec.openUdpEncapsulationSocket(6789);
+            TestSocketKeepaliveCallback callback2 = new TestSocketKeepaliveCallback(executor);
+            try (SocketKeepalive ka2 = mCm.createSocketKeepalive(
+                    myNet, testSocket2, myIPv4, dstIPv4, executor, callback2)) {
+                ka2.start(validKaInterval);
+                callback2.expectStarted();
 
-        ka.stop();
-        callback.expectStopped();
+                ka.stop();
+                callback.expectStopped();
 
-        ka2.stop();
-        callback2.expectStopped();
+                ka2.stop();
+                callback2.expectStopped();
 
-        testSocket.close();
-        testSocket2.close();
+                testSocket.close();
+                testSocket2.close();
+            }
+        }
 
         mWiFiNetworkAgent.disconnect();
         waitFor(mWiFiNetworkAgent.getDisconnectedCV());
@@ -4200,7 +4227,6 @@
         final InetAddress myIPv6 = InetAddress.getByName("::1");
 
         final int validKaInterval = 15;
-        final int invalidKaInterval = 9;
 
         final LinkProperties lp = new LinkProperties();
         lp.setInterfaceName("wlan12");
@@ -4216,37 +4242,46 @@
         final Socket testSocketV6 = new Socket();
 
         TestSocketKeepaliveCallback callback = new TestSocketKeepaliveCallback(executor);
-        SocketKeepalive ka;
 
         // Attempt to start Tcp keepalives with invalid parameters and check for errors.
         // Invalid network.
-        ka = mCm.createSocketKeepalive(notMyNet, testSocketV4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_NETWORK);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+            notMyNet, testSocketV4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_NETWORK);
+        }
 
         // Invalid Socket (socket is not bound with IPv4 address).
-        ka = mCm.createSocketKeepalive(myNet, testSocketV4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+            myNet, testSocketV4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        }
 
         // Invalid Socket (socket is not bound with IPv6 address).
-        ka = mCm.createSocketKeepalive(myNet, testSocketV6, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+            myNet, testSocketV6, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        }
 
         // Bind the socket address
         testSocketV4.bind(new InetSocketAddress(myIPv4, srcPortV4));
         testSocketV6.bind(new InetSocketAddress(myIPv6, srcPortV6));
 
         // Invalid Socket (socket is bound with IPv4 address).
-        ka = mCm.createSocketKeepalive(myNet, testSocketV4, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+            myNet, testSocketV4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        }
 
         // Invalid Socket (socket is bound with IPv6 address).
-        ka = mCm.createSocketKeepalive(myNet, testSocketV6, executor, callback);
-        ka.start(validKaInterval);
-        callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        try (SocketKeepalive ka = mCm.createSocketKeepalive(
+            myNet, testSocketV6, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectError(SocketKeepalive.ERROR_INVALID_SOCKET);
+        }
 
         testSocketV4.close();
         testSocketV6.close();
@@ -4256,6 +4291,66 @@
         mWiFiNetworkAgent = null;
     }
 
+    private void doTestNattSocketKeepalivesFdWithExecutor(Executor executor) throws Exception {
+        final int srcPort = 12345;
+        final InetAddress myIPv4 = InetAddress.getByName("192.0.2.129");
+        final InetAddress anyIPv4 = InetAddress.getByName("0.0.0.0");
+        final InetAddress dstIPv4 = InetAddress.getByName("8.8.8.8");
+        final int validKaInterval = 15;
+
+        // Prepare the target network.
+        LinkProperties lp = new LinkProperties();
+        lp.setInterfaceName("wlan12");
+        lp.addLinkAddress(new LinkAddress(myIPv4, 25));
+        lp.addRoute(new RouteInfo(InetAddress.getByName("192.0.2.254")));
+        Network myNet = connectKeepaliveNetwork(lp);
+        mWiFiNetworkAgent.setStartKeepaliveError(SocketKeepalive.SUCCESS);
+        mWiFiNetworkAgent.setStopKeepaliveError(SocketKeepalive.SUCCESS);
+
+        TestSocketKeepaliveCallback callback = new TestSocketKeepaliveCallback(executor);
+
+        // Prepare the target file descriptor, keep only one instance.
+        final IpSecManager mIpSec = (IpSecManager) mContext.getSystemService(Context.IPSEC_SERVICE);
+        final UdpEncapsulationSocket testSocket = mIpSec.openUdpEncapsulationSocket(srcPort);
+        final ParcelFileDescriptor testPfd =
+                ParcelFileDescriptor.dup(testSocket.getFileDescriptor());
+        testSocket.close();
+        assertTrue(isUdpPortInUse(srcPort));
+
+        // Start keepalive and explicit make the variable goes out of scope with try-with-resources
+        // block.
+        try (SocketKeepalive ka = mCm.createNattKeepalive(
+                myNet, testPfd, myIPv4, dstIPv4, executor, callback)) {
+            ka.start(validKaInterval);
+            callback.expectStarted();
+            ka.stop();
+            callback.expectStopped();
+        }
+
+        // Check that the ParcelFileDescriptor is still valid after keepalive stopped,
+        // ErrnoException with EBADF will be thrown if the socket is closed when checking local
+        // address.
+        assertTrue(isUdpPortInUse(srcPort));
+        final InetSocketAddress sa =
+                (InetSocketAddress) Os.getsockname(testPfd.getFileDescriptor());
+        assertEquals(anyIPv4, sa.getAddress());
+
+        testPfd.close();
+        assertFalse(isUdpPortInUse(srcPort));
+
+        mWiFiNetworkAgent.disconnect();
+        waitFor(mWiFiNetworkAgent.getDisconnectedCV());
+        mWiFiNetworkAgent = null;
+    }
+
+    private static boolean isUdpPortInUse(int port) {
+        try (DatagramSocket ignored = new DatagramSocket(port)) {
+            return false;
+        } catch (IOException ignored) {
+            return true;
+        }
+    }
+
     @Test
     public void testGetCaptivePortalServerUrl() throws Exception {
         String url = mCm.getCaptivePortalServerUrl();
diff --git a/tests/net/java/com/android/server/NetworkManagementServiceTest.java b/tests/net/java/com/android/server/NetworkManagementServiceTest.java
index 6fb3225..968b307 100644
--- a/tests/net/java/com/android/server/NetworkManagementServiceTest.java
+++ b/tests/net/java/com/android/server/NetworkManagementServiceTest.java
@@ -16,6 +16,7 @@
 
 package com.android.server;
 
+import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.reset;
@@ -23,11 +24,11 @@
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 
+import android.annotation.NonNull;
 import android.content.Context;
 import android.net.INetd;
+import android.net.INetdUnsolicitedEventListener;
 import android.net.LinkAddress;
-import android.net.LocalServerSocket;
-import android.net.LocalSocket;
 import android.os.BatteryStats;
 import android.os.Binder;
 import android.os.IBinder;
@@ -43,12 +44,11 @@
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
-import java.io.IOException;
-import java.io.OutputStream;
-
 /**
  * Tests for {@link NetworkManagementService}.
  */
@@ -56,16 +56,16 @@
 @SmallTest
 public class NetworkManagementServiceTest {
 
-    private static final String SOCKET_NAME = "__test__NetworkManagementServiceTest";
     private NetworkManagementService mNMService;
-    private LocalServerSocket mServerSocket;
-    private LocalSocket mSocket;
-    private OutputStream mOutputStream;
 
     @Mock private Context mContext;
     @Mock private IBatteryStats.Stub mBatteryStatsService;
     @Mock private INetd.Stub mNetdService;
 
+    @NonNull
+    @Captor
+    private ArgumentCaptor<INetdUnsolicitedEventListener> mUnsolListenerCaptor;
+
     private final SystemServices mServices = new SystemServices() {
         @Override
         public IBinder getService(String name) {
@@ -88,32 +88,15 @@
     @Before
     public void setUp() throws Exception {
         MockitoAnnotations.initMocks(this);
-
-        // Set up a sheltered test environment.
-        mServerSocket = new LocalServerSocket(SOCKET_NAME);
-
+        doNothing().when(mNetdService)
+                .registerUnsolicitedEventListener(mUnsolListenerCaptor.capture());
         // Start the service and wait until it connects to our socket.
-        mNMService = NetworkManagementService.create(mContext, SOCKET_NAME, mServices);
-        mSocket = mServerSocket.accept();
-        mOutputStream = mSocket.getOutputStream();
+        mNMService = NetworkManagementService.create(mContext, mServices);
     }
 
     @After
     public void tearDown() throws Exception {
         mNMService.shutdown();
-        // Once NetworkManagementService#shutdown() actually does something and shutdowns
-        // the underlying NativeDaemonConnector, the block below should be uncommented.
-        // if (mOutputStream != null) mOutputStream.close();
-        // if (mSocket != null) mSocket.close();
-        // if (mServerSocket != null) mServerSocket.close();
-    }
-
-    /**
-     * Sends a message on the netd socket and gives the events some time to make it back.
-     */
-    private void sendMessage(String message) throws IOException {
-        // Strings are null-terminated, so add "\0" at the end.
-        mOutputStream.write((message + "\0").getBytes());
     }
 
     private static <T> T expectSoon(T mock) {
@@ -131,125 +114,78 @@
 
         // Forget everything that happened to the mock so far, so we can explicitly verify
         // everything that happens and does not happen to it from now on.
-        reset(observer);
 
-        // Now send NetworkManagementService messages and ensure that the observer methods are
-        // called. After every valid message we expect a callback soon after; to ensure that
+        INetdUnsolicitedEventListener unsolListener = mUnsolListenerCaptor.getValue();
+        reset(observer);
+        // Now call unsolListener methods and ensure that the observer methods are
+        // called. After every method we expect a callback soon after; to ensure that
         // invalid messages don't cause any callbacks, we call verifyNoMoreInteractions at the end.
 
         /**
          * Interface changes.
          */
-        sendMessage("600 Iface added rmnet12");
+        unsolListener.onInterfaceAdded("rmnet12");
         expectSoon(observer).interfaceAdded("rmnet12");
 
-        sendMessage("600 Iface removed eth1");
+        unsolListener.onInterfaceRemoved("eth1");
         expectSoon(observer).interfaceRemoved("eth1");
 
-        sendMessage("607 Iface removed eth1");
-        // Invalid code.
-
-        sendMessage("600 Iface borked lo down");
-        // Invalid event.
-
-        sendMessage("600 Iface changed clat4 up again");
-        // Extra tokens.
-
-        sendMessage("600 Iface changed clat4 up");
+        unsolListener.onInterfaceChanged("clat4", true);
         expectSoon(observer).interfaceStatusChanged("clat4", true);
 
-        sendMessage("600 Iface linkstate rmnet0 down");
+        unsolListener.onInterfaceLinkStateChanged("rmnet0", false);
         expectSoon(observer).interfaceLinkStateChanged("rmnet0", false);
 
-        sendMessage("600 IFACE linkstate clat4 up");
-        // Invalid group.
-
         /**
          * Bandwidth control events.
          */
-        sendMessage("601 limit alert data rmnet_usb0");
+        unsolListener.onQuotaLimitReached("data", "rmnet_usb0");
         expectSoon(observer).limitReached("data", "rmnet_usb0");
 
-        sendMessage("601 invalid alert data rmnet0");
-        // Invalid group.
-
-        sendMessage("601 limit increased data rmnet0");
-        // Invalid event.
-
-
         /**
          * Interface class activity.
          */
-
-        sendMessage("613 IfaceClass active 1 1234 10012");
+        unsolListener.onInterfaceClassActivityChanged(true, 1, 1234, 0);
         expectSoon(observer).interfaceClassDataActivityChanged("1", true, 1234);
 
-        sendMessage("613 IfaceClass idle 9 5678");
+        unsolListener.onInterfaceClassActivityChanged(false, 9, 5678, 0);
         expectSoon(observer).interfaceClassDataActivityChanged("9", false, 5678);
 
-        sendMessage("613 IfaceClass reallyactive 9 4321");
+        unsolListener.onInterfaceClassActivityChanged(false, 9, 4321, 0);
         expectSoon(observer).interfaceClassDataActivityChanged("9", false, 4321);
 
-        sendMessage("613 InterfaceClass reallyactive 1");
-        // Invalid group.
-
-
         /**
          * IP address changes.
          */
-        sendMessage("614 Address updated fe80::1/64 wlan0 128 253");
+        unsolListener.onInterfaceAddressUpdated("fe80::1/64", "wlan0", 128, 253);
         expectSoon(observer).addressUpdated("wlan0", new LinkAddress("fe80::1/64", 128, 253));
 
-        // There is no "added", so we take this as "removed".
-        sendMessage("614 Address added fe80::1/64 wlan0 128 253");
+        unsolListener.onInterfaceAddressRemoved("fe80::1/64", "wlan0", 128, 253);
         expectSoon(observer).addressRemoved("wlan0", new LinkAddress("fe80::1/64", 128, 253));
 
-        sendMessage("614 Address removed 2001:db8::1/64 wlan0 1 0");
+        unsolListener.onInterfaceAddressRemoved("2001:db8::1/64", "wlan0", 1, 0);
         expectSoon(observer).addressRemoved("wlan0", new LinkAddress("2001:db8::1/64", 1, 0));
 
-        sendMessage("614 Address removed 2001:db8::1/64 wlan0 1");
-        // Not enough arguments.
-
-        sendMessage("666 Address removed 2001:db8::1/64 wlan0 1 0");
-        // Invalid code.
-
-
         /**
          * DNS information broadcasts.
          */
-        sendMessage("615 DnsInfo servers rmnet_usb0 3600 2001:db8::1");
+        unsolListener.onInterfaceDnsServerInfo("rmnet_usb0", 3600, new String[]{"2001:db8::1"});
         expectSoon(observer).interfaceDnsServerInfo("rmnet_usb0", 3600,
                 new String[]{"2001:db8::1"});
 
-        sendMessage("615 DnsInfo servers wlan0 14400 2001:db8::1,2001:db8::2");
+        unsolListener.onInterfaceDnsServerInfo("wlan0", 14400,
+                new String[]{"2001:db8::1", "2001:db8::2"});
         expectSoon(observer).interfaceDnsServerInfo("wlan0", 14400,
                 new String[]{"2001:db8::1", "2001:db8::2"});
 
         // We don't check for negative lifetimes, only for parse errors.
-        sendMessage("615 DnsInfo servers wlan0 -3600 ::1");
+        unsolListener.onInterfaceDnsServerInfo("wlan0", -3600, new String[]{"::1"});
         expectSoon(observer).interfaceDnsServerInfo("wlan0", -3600,
                 new String[]{"::1"});
 
-        sendMessage("615 DnsInfo servers wlan0 SIXHUNDRED ::1");
-        // Non-numeric lifetime.
-
-        sendMessage("615 DnsInfo servers wlan0 2001:db8::1");
-        // Missing lifetime.
-
-        sendMessage("615 DnsInfo servers wlan0 3600");
-        // No servers.
-
-        sendMessage("615 DnsInfo servers 3600 wlan0 2001:db8::1,2001:db8::2");
-        // Non-numeric lifetime.
-
-        sendMessage("615 DnsInfo wlan0 7200 2001:db8::1,2001:db8::2");
-        // Invalid tokens.
-
-        sendMessage("666 DnsInfo servers wlan0 5400 2001:db8::1");
-        // Invalid code.
-
         // No syntax checking on the addresses.
-        sendMessage("615 DnsInfo servers wlan0 600 ,::,,foo,::1,");
+        unsolListener.onInterfaceDnsServerInfo("wlan0", 600,
+                new String[]{"", "::", "", "foo", "::1"});
         expectSoon(observer).interfaceDnsServerInfo("wlan0", 600,
                 new String[]{"", "::", "", "foo", "::1"});