1 /* 2 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 import sun.security.util.HexDumpEncoder; 25 26 import java.io.PrintStream; 27 import java.net.DatagramPacket; 28 import java.net.DatagramSocket; 29 import java.net.InetAddress; 30 import java.net.InetSocketAddress; 31 import java.net.SocketAddress; 32 import java.net.SocketException; 33 import java.nio.ByteBuffer; 34 import java.util.Arrays; 35 36 /* 37 * A DNS UDP message tracer. 38 * 39 * It listens for DNS UDP requests, forward request to real DNS server, receives 40 * response message and sends back to requester, at same time dump all messages 41 * into capture file 42 * 43 * The capture file contains an DNS protocol exchange in the hexadecimal 44 * dump format emitted by HexDumpEncoder: 45 * 46 * xxxx: 00 11 22 33 44 55 66 77 88 99 aa bb cc dd ee ff ................ 47 * 48 * Typically, the capture file data will be used by DNSServer for playback 49 */ 50 public class DNSTracer extends Thread implements Server { 51 public static final int DNS_DEFAULT_PORT = 53; 52 public static final int DNS_PACKET_SIZE = 512; 53 static HexDumpEncoder encoder = new HexDumpEncoder(); 54 55 private DatagramSocket inSocket; 56 private SocketAddress dnsServerAddress; 57 private ByteBuffer reqBuffer = ByteBuffer.allocate(DNS_PACKET_SIZE); 58 private ByteBuffer resBuffer = ByteBuffer.allocate(DNS_PACKET_SIZE); 59 private PrintStream out = null; 60 private volatile boolean isRunning; 61 62 public DNSTracer(String dnsHostname) throws SocketException { 63 this(dnsHostname, DNS_DEFAULT_PORT); 64 } 65 66 public DNSTracer(PrintStream outStream, String dnsHostname) 67 throws SocketException { 68 this(outStream, dnsHostname, DNS_DEFAULT_PORT); 69 } 70 71 public DNSTracer(String dnsHostname, int dnsPort) throws SocketException { 72 this(System.out, dnsHostname, dnsPort); 73 } 74 75 public DNSTracer(PrintStream outStream, String dnsHostname, int dnsPort) 76 throws SocketException { 77 inSocket = new DatagramSocket(0, InetAddress.getLoopbackAddress()); 78 out = outStream; 79 dnsServerAddress = new InetSocketAddress(dnsHostname, dnsPort); 80 } 81 82 public void run() { 83 isRunning = true; 84 System.out.println( 85 "DNSTracer: listening on port " + inSocket.getLocalPort()); 86 87 System.out.println("DNSTracer: will forward request to server " 88 + dnsServerAddress); 89 90 try (DatagramSocket outSocket = new DatagramSocket()) { 91 while (true) { 92 DatagramPacket reqPacket = new DatagramPacket(reqBuffer.array(), 93 reqBuffer.array().length); 94 inSocket.receive(reqPacket); 95 96 out.println("-> " + reqPacket.getSocketAddress()); 97 out.println(); 98 // dump dns request data 99 out.println(encoder.encodeBuffer( 100 Arrays.copyOf(reqPacket.getData(), 101 reqPacket.getLength()))); 102 out.println(); 103 104 outSocket.send(new DatagramPacket(reqPacket.getData(), 105 reqPacket.getLength(), dnsServerAddress)); 106 DatagramPacket resPacket = new DatagramPacket(resBuffer.array(), 107 resBuffer.array().length); 108 outSocket.receive(resPacket); 109 110 out.println("<- " + resPacket.getSocketAddress()); 111 out.println(); 112 // dump dns response data 113 out.println(encoder.encodeBuffer( 114 Arrays.copyOf(resPacket.getData(), 115 resPacket.getLength()))); 116 out.println(); 117 118 inSocket.send(new DatagramPacket(resPacket.getData(), 119 resPacket.getLength(), reqPacket.getSocketAddress())); 120 } 121 } catch (SocketException se) { 122 if (!isRunning) { 123 out.flush(); 124 System.out.println("DNSTracer: Exit"); 125 } else { 126 se.printStackTrace(); 127 } 128 } catch (Exception e) { 129 e.printStackTrace(); 130 } 131 } 132 133 @Override public void stopServer() { 134 isRunning = false; 135 if (inSocket != null) { 136 try { 137 inSocket.close(); 138 } catch (Exception e) { 139 // ignore 140 } 141 } 142 } 143 144 @Override public int getPort() { 145 if (inSocket != null) { 146 return inSocket.getLocalPort(); 147 } else { 148 return -1; 149 } 150 } 151 }