1package eu.siacs.conversations.utils;
2
3import java.io.ByteArrayOutputStream;
4import java.io.IOException;
5import java.lang.reflect.InvocationTargetException;
6import java.lang.reflect.Method;
7import java.net.DatagramPacket;
8import java.net.DatagramSocket;
9import java.net.InetAddress;
10import java.util.ArrayList;
11import java.util.Random;
12
13import android.os.Bundle;
14import android.util.Log;
15
16public class DNSHelper {
17 public static Bundle getSRVRecord(String host) throws IOException {
18 InetAddress ip = InetAddress.getByName("8.8.8.8");
19 try {
20 Class<?> SystemProperties = Class.forName("android.os.SystemProperties");
21 Method method = SystemProperties.getMethod("get", new Class[] { String.class });
22 ArrayList<String> servers = new ArrayList<String>();
23 for (String name : new String[] { "net.dns1", "net.dns2", "net.dns3", "net.dns4", }) {
24 String value = (String) method.invoke(null, name);
25
26 if (value != null && !"".equals(value) && !servers.contains(value))
27 ip = InetAddress.getByName(value);
28 servers.add(value);
29 }
30 } catch (ClassNotFoundException e) {
31 ip = InetAddress.getByName("8.8.8.8");
32 } catch (NoSuchMethodException e) {
33 ip = InetAddress.getByName("8.8.8.8");
34 } catch (IllegalAccessException e) {
35 ip = InetAddress.getByName("8.8.8.8");
36 } catch (IllegalArgumentException e) {
37 ip = InetAddress.getByName("8.8.8.8");
38 } catch (InvocationTargetException e) {
39 ip = InetAddress.getByName("8.8.8.8");
40 }
41
42 Log.d("xmppService","using dns server: "+ip.toString()+" to look up SRV records");
43
44 Bundle namePort = new Bundle();
45 String[] hostParts = host.split("\\.");
46 byte[] transId = new byte[2];
47 Random random = new Random();
48 random.nextBytes(transId);
49 byte[] header = { 0x01, 0x20, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
50 0x00, 0x01, 0x0c, 0x5f, 0x78, 0x6d, 0x70, 0x70, 0x2d, 0x63,
51 0x6c, 0x69, 0x65, 0x6e, 0x74, 0x04, 0x5f, 0x74, 0x63, 0x70 };
52 byte[] rest = { 0x00, 0x00, 0x21, 0x00, 0x01, 0x00, 0x00, 0x29,
53 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
54 ByteArrayOutputStream output = new ByteArrayOutputStream();
55 output.write(transId);
56 output.write(header);
57 for (int i = 0; i < hostParts.length; ++i) {
58 char[] tmpChars = hostParts[i].toCharArray();
59 byte[] tmp = new byte[tmpChars.length];
60 for (int j = 0; j < tmpChars.length; ++j) {
61 tmp[j] = (byte) tmpChars[j];
62 }
63 output.write(tmp.length);
64 output.write(tmp);
65 }
66 output.write(rest);
67 byte[] sendPaket = output.toByteArray();
68 int realLenght = sendPaket.length - 11;
69 DatagramPacket packet = new DatagramPacket(sendPaket,
70 sendPaket.length, ip, 53);
71 DatagramSocket datagramSocket = new DatagramSocket();
72 datagramSocket.send(packet);
73 byte[] receiveData = new byte[1024];
74
75 DatagramPacket receivePacket = new DatagramPacket(receiveData,
76 receiveData.length);
77 datagramSocket.setSoTimeout(2000);
78 datagramSocket.receive(receivePacket);
79 if (receiveData[3]!=-128) {
80 namePort.putString("error", "nosrv");
81 return namePort;
82 }
83 namePort.putInt("port",calcPort(receiveData[realLenght + 16],
84 receiveData[realLenght + 17]));
85 int i = realLenght + 18;
86 int wordLenght = 0;
87 StringBuilder builder = new StringBuilder();
88 while (receiveData[i] != 0) {
89 if (wordLenght > 0) {
90 builder.append((char) receiveData[i]);
91 --wordLenght;
92 } else {
93 wordLenght = receiveData[i];
94 builder.append(".");
95 }
96 ++i;
97 }
98 builder.replace(0, 1, "");
99 namePort.putString("name",builder.toString());
100 return namePort;
101 }
102
103 static int calcPort(byte hb, byte lb) {
104 return ((int) hb << 8) | ((int) lb & 0xFF);
105 }
106
107 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
108 public static String bytesToHex(byte[] bytes) {
109 char[] hexChars = new char[bytes.length * 2];
110 for ( int j = 0; j < bytes.length; j++ ) {
111 int v = bytes[j] & 0xFF;
112 hexChars[j * 2] = hexArray[v >>> 4];
113 hexChars[j * 2 + 1] = hexArray[v & 0x0F];
114 }
115 return new String(hexChars);
116 }
117}