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.InetSocketAddress;
30 import java.net.SocketAddress;
31 import java.net.SocketException;
32 import java.nio.ByteBuffer;
33 import java.util.Arrays;
34
35 /*
36 * A DNS UDP message tracer.
37 *
38 * It listens for DNS UDP requests, forward request to real DNS server, receives
39 * response message and sends back to requester, at same time dump all messages
40 * into capture file
41 *
42 * The capture file contains an DNS protocol exchange in the hexadecimal
43 * dump format emitted by HexDumpEncoder:
44 *
45 * xxxx: 00 11 22 33 44 55 66 77 88 99 aa bb cc dd ee ff ................
46 *
47 * Typically, the capture file data will be used by DNSServer for playback
48 */
49 public class DNSTracer implements Runnable {
50 public static final int DNS_DEFAULT_PORT = 53;
51 public static final int DNS_PACKET_SIZE = 512;
52 static HexDumpEncoder encoder = new HexDumpEncoder();
53
54 private DatagramSocket inSocket;
55 private SocketAddress dnsServerAddress;
56 private ByteBuffer reqBuffer = ByteBuffer.allocate(DNS_PACKET_SIZE);
57 private ByteBuffer resBuffer = ByteBuffer.allocate(DNS_PACKET_SIZE);
58 private PrintStream out = null;
59
60 public DNSTracer(DatagramSocket socket, String dnsHostname) {
61 this(socket, dnsHostname, DNS_DEFAULT_PORT);
62 }
63
64 public DNSTracer(DatagramSocket socket, PrintStream outStream,
65 String dnsHostname) {
66 this(socket, outStream, dnsHostname, DNS_DEFAULT_PORT);
67 }
68
69 public DNSTracer(DatagramSocket socket, String dnsHostname, int dnsPort) {
70 this(socket, System.out, dnsHostname, dnsPort);
71 }
72
73 public DNSTracer(DatagramSocket socket, PrintStream outStream,
74 String dnsHostname, int dnsPort) {
75 inSocket = socket;
76 out = outStream;
77 dnsServerAddress = new InetSocketAddress(dnsHostname, dnsPort);
78 }
79
80 public void run() {
81 System.out.println(
82 "DNSTracer: listening on port " + inSocket.getLocalPort());
83
84 System.out.println("DNSTracer: will forward request to server "
85 + dnsServerAddress);
86
87 try (DatagramSocket outSocket = new DatagramSocket()) {
88 while (true) {
89 DatagramPacket reqPacket = new DatagramPacket(reqBuffer.array(),
90 reqBuffer.array().length);
91 inSocket.receive(reqPacket);
92
93 out.println("-> " + reqPacket.getSocketAddress());
94 out.println();
95 // dump dns request data
96 out.println(encoder.encodeBuffer(
97 Arrays.copyOf(reqPacket.getData(),
98 reqPacket.getLength())));
99 out.println();
100
101 outSocket.send(new DatagramPacket(reqPacket.getData(),
102 reqPacket.getLength(), dnsServerAddress));
103 DatagramPacket resPacket = new DatagramPacket(resBuffer.array(),
104 resBuffer.array().length);
105 outSocket.receive(resPacket);
106
107 out.println("<- " + resPacket.getSocketAddress());
108 out.println();
109 // dump dns response data
110 out.println(encoder.encodeBuffer(
111 Arrays.copyOf(resPacket.getData(),
112 resPacket.getLength())));
113 out.println();
114
115 inSocket.send(new DatagramPacket(resPacket.getData(),
116 resPacket.getLength(), reqPacket.getSocketAddress()));
117 }
118 } catch (SocketException se) {
119 if (inSocket.isClosed()) {
120 out.flush();
121 System.out.println("DNSTracer: Exit");
122 } else {
123 se.printStackTrace();
124 }
125 } catch (Exception e) {
126 e.printStackTrace();
127 }
128 }
129
130 }