/*

 * Copyright (c) 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.

 */

import sun.security.util.HexDumpEncoder;

import java.io.PrintStream;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetSocketAddress;

import java.net.SocketAddress;

import java.net.SocketException;

import java.nio.ByteBuffer;

import java.util.Arrays;

/*

 * A DNS UDP message tracer.

 *

 * It listens for DNS UDP requests, forward request to real DNS server, receives

 * response message and sends back to requester, at same time dump all messages

 * into capture file

 *

 * The capture file contains an DNS protocol exchange in the hexadecimal

 * dump format emitted by HexDumpEncoder:

 *

 * xxxx: 00 11 22 33 44 55 66 77   88 99 aa bb cc dd ee ff  ................

 *

 * Typically, the capture file data will be used by DNSServer for playback

 */

    public static final int DNS_DEFAULT_PORT = 53;

    public static final int DNS_PACKET_SIZE = 512;

    static HexDumpEncoder encoder = new HexDumpEncoder();

    private DatagramSocket inSocket;

    private SocketAddress dnsServerAddress;

    private ByteBuffer reqBuffer = ByteBuffer.allocate(DNS_PACKET_SIZE);

    private ByteBuffer resBuffer = ByteBuffer.allocate(DNS_PACKET_SIZE);

    private PrintStream out = null;

    }

    }

    }

        out = outStream;

        dnsServerAddress = new InetSocketAddress(dnsHostname, dnsPort);

    }

    public void run() {

        System.out.println(

                "DNSTracer: listening on port " + inSocket.getLocalPort());

        System.out.println("DNSTracer: will forward request to server "

                + dnsServerAddress);

        try (DatagramSocket outSocket = new DatagramSocket()) {

            while (true) {

                DatagramPacket reqPacket = new DatagramPacket(reqBuffer.array(),

                        reqBuffer.array().length);

                inSocket.receive(reqPacket);

                out.println("-> " + reqPacket.getSocketAddress());

                out.println();

                // dump dns request data

                out.println(encoder.encodeBuffer(

                        Arrays.copyOf(reqPacket.getData(),

                                reqPacket.getLength())));

                out.println();

                outSocket.send(new DatagramPacket(reqPacket.getData(),

                        reqPacket.getLength(), dnsServerAddress));

                DatagramPacket resPacket = new DatagramPacket(resBuffer.array(),

                        resBuffer.array().length);

                outSocket.receive(resPacket);

                out.println("<- " + resPacket.getSocketAddress());

                out.println();

                // dump dns response data

                out.println(encoder.encodeBuffer(

                        Arrays.copyOf(resPacket.getData(),

                                resPacket.getLength())));

                out.println();

                inSocket.send(new DatagramPacket(resPacket.getData(),

                        resPacket.getLength(), reqPacket.getSocketAddress()));

            }

        } catch (SocketException se) {

                out.flush();

                System.out.println("DNSTracer: Exit");

            } else {

                se.printStackTrace();

            }

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

}