/*

 * Copyright (c) 2017, 2018, 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

 * @modules java.management java.base/java.io:+open java.base/java.net:+open

 * @run main/othervm UnreferencedDatagramSockets

 * @run main/othervm -Djava.net.preferIPv4Stack=true UnreferencedDatagramSockets

 * @summary Check that unreferenced datagram sockets are closed

 */

import java.io.FileDescriptor;

import java.lang.management.ManagementFactory;

import java.lang.management.OperatingSystemMXBean;

import java.lang.ref.ReferenceQueue;

import java.lang.ref.WeakReference;

import java.lang.reflect.Field;

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.DatagramSocketImpl;

import java.net.InetAddress;

import java.net.UnknownHostException;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.util.ArrayDeque;

import java.util.List;

import java.util.Optional;

import java.util.concurrent.TimeUnit;

import com.sun.management.UnixOperatingSystemMXBean;

public class UnreferencedDatagramSockets {

    /**

     * The set of sockets we have to check up on.

     */

    final static ArrayDeque<NamedWeak> pendingSockets = new ArrayDeque<>(5);

    /**

     * Queued objects when they are unreferenced.

     */

    final static ReferenceQueue<Object> pendingQueue = new ReferenceQueue<>();

    // Server to echo a datagram packet

    static class Server implements Runnable {

        DatagramSocket ss;

        Server() throws IOException {

            ss = new DatagramSocket(0);

            System.out.printf("  DatagramServer addr: %s: %d%n",

                    this.getHost(), this.getPort());

            pendingSockets.add(new NamedWeak(ss, pendingQueue, "serverDatagramSocket"));

            extractRefs(ss, "serverDatagramSocket");

        }

        InetAddress getHost() throws UnknownHostException {

            InetAddress localhost = InetAddress.getByName("localhost"); //.getLocalHost();

            return localhost;

        }

        int getPort() {

            return ss.getLocalPort();

        }

        // Receive a byte and send back a byte

        public void run() {

            try {

                byte[] buffer = new byte[50];

                DatagramPacket p = new DatagramPacket(buffer, buffer.length);

                ss.receive(p);

                buffer[0] += 1;

                ss.send(p);         // send back +1

                // do NOT close but 'forget' the datagram socket reference

                ss = null;

            } catch (Exception ioe) {

                ioe.printStackTrace();

            }

        }

    }

    public static void main(String args[]) throws Exception {

        // Create and close a DatagramSocket to warm up the FD count for side effects.

        try (DatagramSocket s = new DatagramSocket(0)) {

            // no-op; close immediately

            s.getLocalPort();   // no-op

        }

        long fdCount0 = getFdCount();

        listProcFD();

        // start a server

        Server svr = new Server();

        Thread thr = new Thread(svr);

        thr.start();

        DatagramSocket client = new DatagramSocket(0);

        client.connect(svr.getHost(), svr.getPort());

        pendingSockets.add(new NamedWeak(client, pendingQueue, "clientDatagramSocket"));

        extractRefs(client, "clientDatagramSocket");

        byte[] msg = new byte[1];

        msg[0] = 1;

        DatagramPacket p = new DatagramPacket(msg, msg.length, svr.getHost(), svr.getPort());

        client.send(p);

        p = new DatagramPacket(msg, msg.length);

        client.receive(p);

        System.out.printf("echo received from: %s%n", p.getSocketAddress());

        if (msg[0] != 2) {

            throw new AssertionError("incorrect data received: expected: 2, actual: " + msg[0]);

        }

        // Do NOT close the DatagramSocket; forget it

        Object ref;

        int loops = 20;

        while (!pendingSockets.isEmpty() && loops-- > 0) {

            ref = pendingQueue.remove(1000L);

            if (ref != null) {

                pendingSockets.remove(ref);

                System.out.printf("  ref freed: %s, remaining: %d%n", ref, pendingSockets.size());

            } else {

                client = null;

                p = null;

                msg = null;

                System.gc();

            }

        }

        thr.join();

        // List the open file descriptors

        long fdCount = getFdCount();

        System.out.printf("Initial fdCount: %d, final fdCount: %d%n", fdCount0, fdCount);

        listProcFD();

        if (loops == 0) {

            throw new AssertionError("Not all references reclaimed");

        }

    }

    // Get the count of open file descriptors, or -1 if not available

    private static long getFdCount() {

        OperatingSystemMXBean mxBean = ManagementFactory.getOperatingSystemMXBean();

        return (mxBean instanceof UnixOperatingSystemMXBean)

                ? ((UnixOperatingSystemMXBean) mxBean).getOpenFileDescriptorCount()

                : -1L;

    }

    // Reflect to find references in the datagram implementation that will be gc'd

    private static void extractRefs(DatagramSocket s, String name) {

        try {

            Field socketImplField = DatagramSocket.class.getDeclaredField("impl");

            socketImplField.setAccessible(true);

            Object socketImpl = socketImplField.get(s);

            Field fileDescriptorField = DatagramSocketImpl.class.getDeclaredField("fd");

            fileDescriptorField.setAccessible(true);

            FileDescriptor fileDescriptor = (FileDescriptor) fileDescriptorField.get(socketImpl);

            extractRefs(fileDescriptor, name);

            Class<?> socketImplClass = socketImpl.getClass();

            System.out.printf("socketImplClass: %s%n", socketImplClass);

            if (socketImplClass.getName().equals("java.net.TwoStacksPlainDatagramSocketImpl")) {

                Field fileDescriptor1Field = socketImplClass.getDeclaredField("fd1");

                fileDescriptor1Field.setAccessible(true);

                FileDescriptor fileDescriptor1 = (FileDescriptor) fileDescriptor1Field.get(socketImpl);

                extractRefs(fileDescriptor1, name + "::twoStacksFd1");

            } else {

                System.out.printf("socketImpl class name not matched: %s != %s%n",

                        socketImplClass.getName(), "java.net.TwoStacksPlainDatagramSocketImpl");

            }

        } catch (NoSuchFieldException | IllegalAccessException ex) {

            ex.printStackTrace();

            throw new AssertionError("missing field", ex);

        }

    }

    private static void extractRefs(FileDescriptor fileDescriptor, String name) {

        Object cleanup = null;

        int rawfd = -1;

        try {

            if (fileDescriptor != null) {

                Field fd1Field = FileDescriptor.class.getDeclaredField("fd");

                fd1Field.setAccessible(true);

                rawfd = fd1Field.getInt(fileDescriptor);

                Field cleanupfdField = FileDescriptor.class.getDeclaredField("cleanup");

                cleanupfdField.setAccessible(true);

                cleanup = cleanupfdField.get(fileDescriptor);

                pendingSockets.add(new NamedWeak(fileDescriptor, pendingQueue,

                        name + "::fileDescriptor: " + rawfd));

                pendingSockets.add(new NamedWeak(cleanup, pendingQueue, name + "::fdCleanup: " + rawfd));

            }

        } catch (NoSuchFieldException | IllegalAccessException ex) {

            ex.printStackTrace();

            throw new AssertionError("missing field", ex);

        } finally {

            System.out.print(String.format("  %s:: fd: %s, fd: %d, cleanup: %s%n",

                    name, fileDescriptor, rawfd, cleanup));

        }

    }

    /**

     * Method to list the open file descriptors (if supported by the 'lsof' command).

     */

    static void listProcFD() {

        List<String> lsofDirs = List.of("/usr/bin", "/usr/sbin");

        Optional<Path> lsof = lsofDirs.stream()

                .map(s -> Paths.get(s, "lsof"))

                .filter(f -> Files.isExecutable(f))

                .findFirst();

        lsof.ifPresent(exe -> {

            try {

                System.out.printf("Open File Descriptors:%n");

                long pid = ProcessHandle.current().pid();

                ProcessBuilder pb = new ProcessBuilder(exe.toString(), "-p", Integer.toString((int) pid));

                pb.inheritIO();

                Process p = pb.start();

                p.waitFor(10, TimeUnit.SECONDS);

            } catch (IOException | InterruptedException ie) {

                ie.printStackTrace();

            }

        });

    }

    // Simple class to identify which refs have been queued

    static class NamedWeak extends WeakReference<Object> {

        private final String name;

        NamedWeak(Object o, ReferenceQueue<Object> queue, String name) {

            super(o, queue);

            this.name = name;

        }

        public String toString() {

            return name + "; " + super.toString();

        }

    }

}