Add a module-lib API for constructing a LocalSocket from an fd. am: 8093d78d1c am: 15bf48abb2 am: 39000cbc73

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1954386

Change-Id: Ib066a914ea652a712d894665f002bae91f200514

core/api/module-lib-current.txt

@@ -240,6 +240,10 @@ package android.net {
     method public int getResourceId();
   }
 
+  public class LocalSocket implements java.io.Closeable {
+    ctor public LocalSocket(@NonNull java.io.FileDescriptor);
+  }
+
   public class NetworkIdentity {
     method public int getOemManaged();
     method public int getRatType();

core/java/android/net/LocalServerSocket.java

@@ -55,7 +55,9 @@ public class LocalServerSocket implements Closeable {
      * Create a LocalServerSocket from a file descriptor that's already
      * been created and bound. listen() will be called immediately on it.
      * Used for cases where file descriptors are passed in via environment
-     * variables
+     * variables. The passed-in FileDescriptor is not managed by this class
+     * and must be closed by the caller. Calling {@link #close()} on a socket
+     * created by this method has no effect.
      *
      * @param fd bound file descriptor
      * @throws IOException

core/java/android/net/LocalSocket.java

@@ -16,7 +16,14 @@
 
 package android.net;
 
+import static android.annotation.SystemApi.Client.MODULE_LIBRARIES;
+
+import android.annotation.NonNull;
+import android.annotation.SuppressLint;
+import android.annotation.SystemApi;
 import android.compat.annotation.UnsupportedAppUsage;
+import android.system.ErrnoException;
+import android.system.Os;
 
 import java.io.Closeable;
 import java.io.FileDescriptor;
@@ -74,32 +81,52 @@ public class LocalSocket implements Closeable {
         this.isBound = false;
     }
 
+    private void checkConnected() {
+        try {
+            Os.getpeername(impl.getFileDescriptor());
+        } catch (ErrnoException e) {
+            throw new IllegalArgumentException("Not a connected socket", e);
+        }
+        isConnected = true;
+        isBound = true;
+        implCreated = true;
+    }
+
+    /**
+     * Creates a LocalSocket instance using the {@link FileDescriptor} for an already-connected
+     * AF_LOCAL/UNIX domain stream socket. The passed-in FileDescriptor is not managed by this class
+     * and must be closed by the caller. Calling {@link #close()} on a socket created by this
+     * method has no effect.
+     *
+     * @param fd the filedescriptor to adopt
+     *
+     * @hide
+     */
+    @SystemApi(client = MODULE_LIBRARIES)
+    public LocalSocket(@NonNull @SuppressLint("UseParcelFileDescriptor") FileDescriptor fd) {
+        this(new LocalSocketImpl(fd), SOCKET_UNKNOWN);
+        checkConnected();
+    }
+
     /**
      * Creates a LocalSocket instances using the FileDescriptor for an already-connected
      * AF_LOCAL/UNIX domain stream socket. Note: the FileDescriptor must be closed by the caller:
      * closing the LocalSocket will not close it.
      *
-     * @hide - used by BluetoothSocket.
+     * TODO: delete this method when Bluetooth is no longer using it.
+     *
+     * @hide
      */
     public static LocalSocket createConnectedLocalSocket(FileDescriptor fd) {
-        return createConnectedLocalSocket(new LocalSocketImpl(fd), SOCKET_UNKNOWN);
+        return new LocalSocket(fd);
     }
 
     /**
      * for use with LocalServerSocket.accept()
      */
     static LocalSocket createLocalSocketForAccept(LocalSocketImpl impl) {
-        return createConnectedLocalSocket(impl, SOCKET_UNKNOWN);
-    }
-
-    /**
-     * Creates a LocalSocket from an existing LocalSocketImpl that is already connected.
-     */
-    private static LocalSocket createConnectedLocalSocket(LocalSocketImpl impl, int sockType) {
-        LocalSocket socket = new LocalSocket(impl, sockType);
-        socket.isConnected = true;
-        socket.isBound = true;
-        socket.implCreated = true;
+        LocalSocket socket = new LocalSocket(impl, SOCKET_UNKNOWN);
+        socket.checkConnected();
         return socket;
     }