8231260: (dc) DatagramChannel::disconnect changes the port of the local address to 0 (lnx)

DatagramChannel::disconnect will attempt to rebind to the original port if the local port switches back to 0 after the association is disolved by the system.

Reviewed-by: alanb, chegar, fweimer

src/java.base/share/classes/java/nio/channels/DatagramChannel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -328,6 +328,10 @@ public abstract class DatagramChannel
      * <p> If this channel's socket is not connected, or if the channel is
      * closed, then invoking this method has no effect.  </p>
      *
+     * @apiNote If this method throws an IOException, the channel's socket
+     * may be left in an unspecified state. It is strongly recommended that
+     * the channel be closed when disconnect fails.
+     *
      * @return  This datagram channel
      *
      * @throws  IOException

src/java.base/share/classes/sun/nio/ch/DatagramChannelImpl.java

@@ -875,6 +875,11 @@ class DatagramChannelImpl
                     if (state == ST_CONNECTED)
                         throw new AlreadyConnectedException();
 
+                    // ensure that the socket is bound
+                    if (localAddress == null) {
+                        bindInternal(null);
+                    }
+
                     int n = Net.connect(family,
                                         fd,
                                         isa.getAddress(),
@@ -932,8 +937,21 @@ class DatagramChannelImpl
                     remoteAddress = null;
                     state = ST_UNCONNECTED;
 
-                    // refresh local address
+                    // check whether rebind is needed
-                    localAddress = Net.localAddress(fd);
+                    InetSocketAddress isa = Net.localAddress(fd);
+                    if (isa.getPort() == 0) {
+                        // On Linux, if bound to ephemeral port,
+                        // disconnect does not preserve that port.
+                        // In this case, try to rebind to the previous port.
+                        int port = localAddress.getPort();
+                        localAddress = isa; // in case Net.bind fails
+                        Net.bind(family, fd, isa.getAddress(), port);
+                        isa = Net.localAddress(fd); // refresh address
+                        assert isa.getPort() == port;
+                    }
+
+                    // refresh localAddress
+                    localAddress = isa;
                 }
             } finally {
                 writeLock.unlock();

test/jdk/java/nio/channels/DatagramChannel/AddressesAfterDisconnect.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @library /test/lib
+ * @summary Test DatagramChannel local address after disconnect.
+ * @requires (os.family != "mac")
+ * @run testng/othervm AddressesAfterDisconnect
+ * @run testng/othervm -Djava.net.preferIPv6Addresses=true AddressesAfterDisconnect
+ * @run testng/othervm -Djava.net.preferIPv4Stack=true AddressesAfterDisconnect
+ */
+
+import jdk.test.lib.net.IPSupport;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.net.StandardProtocolFamily;
+import java.nio.channels.DatagramChannel;
+
+import org.testng.annotations.Test;
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertTrue;
+import static org.testng.Assert.assertFalse;
+
+public class AddressesAfterDisconnect {
+
+    public static void main(String[] args) throws IOException {
+        new AddressesAfterDisconnect().execute();
+    }
+
+    @Test
+    public void execute() throws IOException {
+        IPSupport.throwSkippedExceptionIfNonOperational();
+        boolean preferIPv6 = Boolean.getBoolean("java.net.preferIPv6Addresses");
+
+        // test with default protocol family
+        try (DatagramChannel dc = DatagramChannel.open()) {
+            System.out.println("Test with default");
+            dc.bind(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0));
+            test(dc);
+            test(dc);
+        }
+
+        if (IPSupport.hasIPv6()) {
+            // test with IPv6 only
+            System.out.println("Test with IPv6 only");
+            try (DatagramChannel dc = DatagramChannel.open(StandardProtocolFamily.INET6)) {
+                dc.bind(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0));
+                test(dc);
+                test(dc);
+            }
+        }
+
+        if (IPSupport.hasIPv4() && !preferIPv6) {
+            // test with IPv4 only
+            System.out.println("Test with IPv4 only");
+            try (DatagramChannel dc = DatagramChannel.open(StandardProtocolFamily.INET)) {
+                dc.bind(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0));
+                test(dc);
+                test(dc);
+            }
+        }
+    }
+
+    /**
+     * Connect DatagramChannel to a server, write a datagram and disconnect. Invoke
+     * a second or subsequent time with the same DatagramChannel instance to check
+     * that disconnect works as expected.
+     */
+    static void test(DatagramChannel dc) throws IOException {
+        SocketAddress local = dc.getLocalAddress();
+        try (DatagramChannel server = DatagramChannel.open()) {
+            server.bind(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0));
+            SocketAddress remote = server.getLocalAddress();
+            dc.connect(remote);
+            assertTrue(dc.isConnected());
+            // comment the following two lines on OS X to see JDK-8231259
+            assertEquals(dc.getLocalAddress(), local, "local address after connect");
+            assertEquals(dc.getRemoteAddress(), remote, "remote address after connect");
+            dc.disconnect();
+            assertFalse(dc.isConnected());
+            assertEquals(dc.getLocalAddress(), local, "local address after disconnect");
+            assertEquals(dc.getRemoteAddress(), null, "remote address after disconnect");
+        }
+    }
+
+}