1package eu.siacs.conversations.utils;
2
3import java.io.ByteArrayOutputStream;
4import java.io.IOException;
5import java.net.DatagramPacket;
6import java.net.DatagramSocket;
7import java.net.InetAddress;
8import java.util.Random;
9
10import android.os.Bundle;
11
12public class DNSHelper {
13 public static Bundle getSRVRecord(String host) throws IOException {
14 Bundle namePort = new Bundle();
15 String[] hostParts = host.split("\\.");
16 byte[] transId = new byte[2];
17 Random random = new Random();
18 random.nextBytes(transId);
19 byte[] header = { 0x01, 0x20, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
20 0x00, 0x01, 0x0c, 0x5f, 0x78, 0x6d, 0x70, 0x70, 0x2d, 0x63,
21 0x6c, 0x69, 0x65, 0x6e, 0x74, 0x04, 0x5f, 0x74, 0x63, 0x70 };
22 byte[] rest = { 0x00, 0x00, 0x21, 0x00, 0x01, 0x00, 0x00, 0x29,
23 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
24 ByteArrayOutputStream output = new ByteArrayOutputStream();
25 output.write(transId);
26 output.write(header);
27 for (int i = 0; i < hostParts.length; ++i) {
28 char[] tmpChars = hostParts[i].toCharArray();
29 byte[] tmp = new byte[tmpChars.length];
30 for (int j = 0; j < tmpChars.length; ++j) {
31 tmp[j] = (byte) tmpChars[j];
32 }
33 output.write(tmp.length);
34 output.write(tmp);
35 }
36 output.write(rest);
37 byte[] sendPaket = output.toByteArray();
38 byte[] addr = { 0x8, 0x8, 0x8, 0x8 };
39 int realLenght = sendPaket.length - 11;
40 DatagramPacket packet = new DatagramPacket(sendPaket,
41 sendPaket.length, InetAddress.getByAddress(addr), 53);
42 DatagramSocket datagramSocket = new DatagramSocket();
43 datagramSocket.send(packet);
44 byte[] receiveData = new byte[1024];
45
46 DatagramPacket receivePacket = new DatagramPacket(receiveData,
47 receiveData.length);
48 datagramSocket.setSoTimeout(2000);
49 datagramSocket.receive(receivePacket);
50 if (receiveData[3]!=-128) {
51 namePort.putString("error", "nosrv");
52 return namePort;
53 }
54 namePort.putInt("port",calcPort(receiveData[realLenght + 16],
55 receiveData[realLenght + 17]));
56 int i = realLenght + 18;
57 int wordLenght = 0;
58 StringBuilder builder = new StringBuilder();
59 while (receiveData[i] != 0) {
60 if (wordLenght > 0) {
61 builder.append((char) receiveData[i]);
62 --wordLenght;
63 } else {
64 wordLenght = receiveData[i];
65 builder.append(".");
66 }
67 ++i;
68 }
69 builder.replace(0, 1, "");
70 namePort.putString("name",builder.toString());
71 return namePort;
72 }
73
74 static int calcPort(byte hb, byte lb) {
75 return ((int) hb << 8) | ((int) lb & 0xFF);
76 }
77
78 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
79 public static String bytesToHex(byte[] bytes) {
80 char[] hexChars = new char[bytes.length * 2];
81 for ( int j = 0; j < bytes.length; j++ ) {
82 int v = bytes[j] & 0xFF;
83 hexChars[j * 2] = hexArray[v >>> 4];
84 hexChars[j * 2 + 1] = hexArray[v & 0x0F];
85 }
86 return new String(hexChars);
87 }
88}