[KA05] Export keepalive offload api for IpSec Nat-T file descriptor

Adds system api of createSocketKeepalive to take file descriptor,
so privileged apps could use it without the need of IpSecService.

Bug: 114151147
Test: atest FrameworksNetTests
Change-Id: If926c21704b6ed73a0adfcadad732b97b42bacae
diff --git a/core/java/android/net/ConnectivityManager.java b/core/java/android/net/ConnectivityManager.java
index 90eb13e..5bb24ba 100644
--- a/core/java/android/net/ConnectivityManager.java
+++ b/core/java/android/net/ConnectivityManager.java
@@ -15,6 +15,8 @@
  */
 package android.net;
 
+import static android.net.IpSecManager.INVALID_RESOURCE_ID;
+
 import android.annotation.CallbackExecutor;
 import android.annotation.IntDef;
 import android.annotation.NonNull;
@@ -61,6 +63,7 @@
 
 import libcore.net.event.NetworkEventDispatcher;
 
+import java.io.FileDescriptor;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.net.InetAddress;
@@ -1849,8 +1852,39 @@
             @NonNull InetAddress destination,
             @NonNull @CallbackExecutor Executor executor,
             @NonNull Callback callback) {
-        return new NattSocketKeepalive(mService, network, socket, source, destination, executor,
-                callback);
+        return new NattSocketKeepalive(mService, network, socket.getFileDescriptor(),
+            socket.getResourceId(), source, destination, executor, callback);
+    }
+
+    /**
+     * Request that keepalives be started on a IPsec NAT-T socket file descriptor. Directly called
+     * 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 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}.
+     * @param executor The executor on which callback will be invoked. The provided {@link Executor}
+     *                 must run callback sequentially, otherwise the order of callbacks cannot be
+     *                 guaranteed.
+     * @param callback A {@link SocketKeepalive.Callback}. Used for notifications about keepalive
+     *        changes. Must be extended by applications that use this API.
+     *
+     * @hide
+     */
+    @SystemApi
+    @RequiresPermission(android.Manifest.permission.PACKET_KEEPALIVE_OFFLOAD)
+    public SocketKeepalive createNattKeepalive(@NonNull Network network,
+            @NonNull FileDescriptor fd,
+            @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);
     }
 
     /**
diff --git a/core/java/android/net/IConnectivityManager.aidl b/core/java/android/net/IConnectivityManager.aidl
index 131925e..e97060a 100644
--- a/core/java/android/net/IConnectivityManager.aidl
+++ b/core/java/android/net/IConnectivityManager.aidl
@@ -181,6 +181,10 @@
     void startNattKeepalive(in Network network, int intervalSeconds, in Messenger messenger,
             in IBinder binder, String srcAddr, int srcPort, String dstAddr);
 
+    void startNattKeepaliveWithFd(in Network network, in FileDescriptor fd, int resourceId,
+            int intervalSeconds, in Messenger messenger, in IBinder binder, String srcAddr,
+            String dstAddr);
+
     void stopKeepalive(in Network network, int slot);
 
     String getCaptivePortalServerUrl();
diff --git a/core/java/android/net/NattSocketKeepalive.java b/core/java/android/net/NattSocketKeepalive.java
index 94f2da5..88631ae 100644
--- a/core/java/android/net/NattSocketKeepalive.java
+++ b/core/java/android/net/NattSocketKeepalive.java
@@ -17,11 +17,11 @@
 package android.net;
 
 import android.annotation.NonNull;
-import android.net.IpSecManager.UdpEncapsulationSocket;
 import android.os.Binder;
 import android.os.RemoteException;
 import android.util.Log;
 
+import java.io.FileDescriptor;
 import java.net.InetAddress;
 import java.util.concurrent.Executor;
 
@@ -32,11 +32,13 @@
 
     @NonNull private final InetAddress mSource;
     @NonNull private final InetAddress mDestination;
-    @NonNull private final UdpEncapsulationSocket mSocket;
+    @NonNull private final FileDescriptor mFd;
+    private final int mResourceId;
 
     NattSocketKeepalive(@NonNull IConnectivityManager service,
             @NonNull Network network,
-            @NonNull UdpEncapsulationSocket socket,
+            @NonNull FileDescriptor fd,
+            int resourceId,
             @NonNull InetAddress source,
             @NonNull InetAddress destination,
             @NonNull Executor executor,
@@ -44,15 +46,15 @@
         super(service, network, executor, callback);
         mSource = source;
         mDestination = destination;
-        mSocket = socket;
+        mFd = fd;
+        mResourceId = resourceId;
     }
 
     @Override
     void startImpl(int intervalSec) {
         try {
-            // TODO: Create new interface in ConnectivityService and pass fd to it.
-            mService.startNattKeepalive(mNetwork, intervalSec, mMessenger, new Binder(),
-                    mSource.getHostAddress(), mSocket.getPort(), mDestination.getHostAddress());
+            mService.startNattKeepaliveWithFd(mNetwork, mFd, mResourceId, intervalSec, mMessenger,
+                    new Binder(), mSource.getHostAddress(), mDestination.getHostAddress());
         } catch (RemoteException e) {
             Log.e(TAG, "Error starting packet keepalive: ", e);
             stopLooper();
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 38594ef..2a7d025 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -73,6 +73,7 @@
 import android.net.LinkProperties;
 import android.net.LinkProperties.CompareResult;
 import android.net.MatchAllNetworkSpecifier;
+import android.net.NattSocketKeepalive;
 import android.net.Network;
 import android.net.NetworkAgent;
 import android.net.NetworkCapabilities;
@@ -6185,6 +6186,17 @@
     }
 
     @Override
+    public void startNattKeepaliveWithFd(Network network, FileDescriptor fd, int resourceId,
+            int intervalSeconds, Messenger messenger, IBinder binder, String srcAddr,
+            String dstAddr) {
+        enforceKeepalivePermission();
+        mKeepaliveTracker.startNattKeepalive(
+                getNetworkAgentInfoForNetwork(network), fd, resourceId,
+                intervalSeconds, messenger, binder,
+                srcAddr, dstAddr, NattSocketKeepalive.NATT_PORT);
+    }
+
+    @Override
     public void stopKeepalive(Network network, int slot) {
         mHandler.sendMessage(mHandler.obtainMessage(
                 NetworkAgent.CMD_STOP_PACKET_KEEPALIVE, slot, PacketKeepalive.SUCCESS, network));
diff --git a/services/core/java/com/android/server/connectivity/KeepaliveTracker.java b/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
index 8a3cdca..1559ba8 100644
--- a/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
+++ b/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
@@ -16,40 +16,49 @@
 
 package com.android.server.connectivity;
 
-import com.android.internal.util.HexDump;
-import com.android.internal.util.IndentingPrintWriter;
-import com.android.server.connectivity.NetworkAgentInfo;
-import android.net.ConnectivityManager;
+// TODO: Clean up imports and remove references of PacketKeepalive constants.
+
+import static android.net.ConnectivityManager.PacketKeepalive.ERROR_INVALID_INTERVAL;
+import static android.net.ConnectivityManager.PacketKeepalive.ERROR_INVALID_IP_ADDRESS;
+import static android.net.ConnectivityManager.PacketKeepalive.ERROR_INVALID_NETWORK;
+import static android.net.ConnectivityManager.PacketKeepalive.MIN_INTERVAL;
+import static android.net.ConnectivityManager.PacketKeepalive.NATT_PORT;
+import static android.net.ConnectivityManager.PacketKeepalive.NO_KEEPALIVE;
+import static android.net.ConnectivityManager.PacketKeepalive.SUCCESS;
+import static android.net.NetworkAgent.CMD_START_PACKET_KEEPALIVE;
+import static android.net.NetworkAgent.CMD_STOP_PACKET_KEEPALIVE;
+import static android.net.NetworkAgent.EVENT_PACKET_KEEPALIVE;
+import static android.net.SocketKeepalive.ERROR_INVALID_SOCKET;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.net.ConnectivityManager.PacketKeepalive;
 import android.net.KeepalivePacketData;
-import android.net.LinkAddress;
 import android.net.NetworkAgent;
 import android.net.NetworkUtils;
 import android.net.util.IpUtils;
 import android.os.Binder;
-import android.os.IBinder;
 import android.os.Handler;
+import android.os.IBinder;
 import android.os.Message;
 import android.os.Messenger;
 import android.os.Process;
 import android.os.RemoteException;
-import android.system.OsConstants;
+import android.system.ErrnoException;
+import android.system.Os;
 import android.util.Log;
 import android.util.Pair;
 
-import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
-import java.net.Inet4Address;
-import java.net.Inet6Address;
+import com.android.internal.util.HexDump;
+import com.android.internal.util.IndentingPrintWriter;
+
+import java.io.FileDescriptor;
 import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
 import java.util.ArrayList;
 import java.util.HashMap;
 
-import static android.net.ConnectivityManager.PacketKeepalive.*;
-import static android.net.NetworkAgent.CMD_START_PACKET_KEEPALIVE;
-import static android.net.NetworkAgent.CMD_STOP_PACKET_KEEPALIVE;
-import static android.net.NetworkAgent.EVENT_PACKET_KEEPALIVE;
-
 /**
  * Manages packet keepalive requests.
  *
@@ -300,7 +309,9 @@
         }
     }
 
-    public void handleEventPacketKeepalive(NetworkAgentInfo nai, Message message) {
+    /** Handle keepalive events from lower layer. */
+    public void handleEventPacketKeepalive(@NonNull NetworkAgentInfo nai,
+            @NonNull Message message) {
         int slot = message.arg1;
         int reason = message.arg2;
 
@@ -330,8 +341,18 @@
         }
     }
 
-    public void startNattKeepalive(NetworkAgentInfo nai, int intervalSeconds, Messenger messenger,
-            IBinder binder, String srcAddrString, int srcPort, String dstAddrString, int dstPort) {
+    /**
+     * Called when requesting that keepalives be started on a IPsec NAT-T socket. See
+     * {@link android.net.SocketKeepalive}.
+     **/
+    public void startNattKeepalive(@Nullable NetworkAgentInfo nai,
+            int intervalSeconds,
+            @NonNull Messenger messenger,
+            @NonNull IBinder binder,
+            @NonNull String srcAddrString,
+            int srcPort,
+            @NonNull String dstAddrString,
+            int dstPort) {
         if (nai == null) {
             notifyMessenger(messenger, NO_KEEPALIVE, ERROR_INVALID_NETWORK);
             return;
@@ -360,6 +381,56 @@
                 NetworkAgent.CMD_START_PACKET_KEEPALIVE, ki).sendToTarget();
     }
 
+   /**
+    * Called when requesting that keepalives be started on a IPsec NAT-T socket. This function is
+    * identical to {@link #startNattKeepalive}, but also takes a {@code resourceId}, which is the
+    * resource index bound to the {@link UdpEncapsulationSocket} when creating by
+    * {@link com.android.server.IpSecService} to verify whether the given
+    * {@link UdpEncapsulationSocket} is legitimate.
+    **/
+    public void startNattKeepalive(@Nullable NetworkAgentInfo nai,
+            @Nullable FileDescriptor fd,
+            int resourceId,
+            int intervalSeconds,
+            @NonNull Messenger messenger,
+            @NonNull IBinder binder,
+            @NonNull String srcAddrString,
+            @NonNull String dstAddrString,
+            int dstPort) {
+        // Ensure that the socket is created by IpSecService.
+        if (!isNattKeepaliveSocketValid(fd, resourceId)) {
+            notifyMessenger(messenger, NO_KEEPALIVE, ERROR_INVALID_SOCKET);
+        }
+
+        // Get src port to adopt old API.
+        int srcPort = 0;
+        try {
+            final SocketAddress srcSockAddr = Os.getsockname(fd);
+            srcPort = ((InetSocketAddress) srcSockAddr).getPort();
+        } catch (ErrnoException e) {
+            notifyMessenger(messenger, NO_KEEPALIVE, ERROR_INVALID_SOCKET);
+        }
+
+        // Forward request to old API.
+        startNattKeepalive(nai, intervalSeconds, messenger, binder, srcAddrString, srcPort,
+                dstAddrString, dstPort);
+    }
+
+    /**
+     * Verify if the IPsec NAT-T file descriptor and resource Id hold for IPsec keepalive is valid.
+     **/
+    public static boolean isNattKeepaliveSocketValid(@Nullable FileDescriptor fd, int resourceId) {
+        // TODO: 1. confirm whether the fd is called from system api or created by IpSecService.
+        //       2. If the fd is created from the system api, check that it's bounded. And
+        //          call dup to keep the fd open.
+        //       3. If the fd is created from IpSecService, check if the resource ID is valid. And
+        //          hold the resource needed in IpSecService.
+        if (null == fd) {
+            return false;
+        }
+        return true;
+    }
+
     public void dump(IndentingPrintWriter pw) {
         pw.println("Packet keepalives:");
         pw.increaseIndent();
diff --git a/tests/net/java/com/android/server/ConnectivityServiceTest.java b/tests/net/java/com/android/server/ConnectivityServiceTest.java
index 4d6f27b..b5d5f61 100644
--- a/tests/net/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/net/java/com/android/server/ConnectivityServiceTest.java
@@ -3778,6 +3778,7 @@
         // TODO: 1. Move this outside of ConnectivityServiceTest.
         //       2. Add helper function to test against newSingleThreadExecutor as well as inline
         //          executor.
+        //       3. Make test to verify that Nat-T keepalive socket is created by IpSecService.
         final int srcPort = 12345;
         final InetAddress myIPv4 = InetAddress.getByName("192.0.2.129");
         final InetAddress notMyIPv4 = InetAddress.getByName("192.0.2.35");