aboutsummaryrefslogtreecommitdiffstats
path: root/src/eu/siacs/conversations/utils/DNSHelper.java
blob: fd3b195348c21b42fa395bceaeeaf9d615a80dfd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
package eu.siacs.conversations.utils;

import de.measite.minidns.Client;
import de.measite.minidns.DNSMessage;
import de.measite.minidns.Record;
import de.measite.minidns.Record.TYPE;
import de.measite.minidns.Record.CLASS;
import de.measite.minidns.record.SRV;
import de.measite.minidns.record.A;
import de.measite.minidns.record.AAAA;
import de.measite.minidns.record.Data;
import de.measite.minidns.util.NameUtil;
import eu.siacs.conversations.Config;

import java.io.IOException;
import java.net.InetAddress;
import java.net.SocketTimeoutException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;
import java.util.TreeMap;

import android.os.Bundle;
import android.util.Log;

public class DNSHelper {
	protected static Client client = new Client();

	public static Bundle getSRVRecord(String host) throws IOException {
		String dns[] = client.findDNS();

		if (dns != null) {
			// we have a list of DNS servers, let's go
			for (String dnsserver : dns) {
				InetAddress ip = InetAddress.getByName(dnsserver);
				Bundle b = queryDNS(host, ip);
				if (b.containsKey("name")) {
					return b;
				}
			}
		}

		// fallback
		return queryDNS(host, InetAddress.getByName("8.8.8.8"));
	}

	public static Bundle queryDNS(String host, InetAddress dnsServer) {
		Bundle namePort = new Bundle();
		try {
			String qname = "_xmpp-client._tcp." + host;
			Log.d(Config.LOGTAG,
					"using dns server: " + dnsServer.getHostAddress()
							+ " to look up " + host);
			DNSMessage message = client.query(qname, TYPE.SRV, CLASS.IN,
					dnsServer.getHostAddress());

			// How should we handle priorities and weight?
			// Wikipedia has a nice article about priorities vs. weights:
			// https://en.wikipedia.org/wiki/SRV_record#Provisioning_for_high_service_availability

			// we bucket the SRV records based on priority, pick per priority
			// a random order respecting the weight, and dump that priority by
			// priority

			TreeMap<Integer, ArrayList<SRV>> priorities = new TreeMap<Integer, ArrayList<SRV>>();
			TreeMap<String, ArrayList<String>> ips4 = new TreeMap<String, ArrayList<String>>();
			TreeMap<String, ArrayList<String>> ips6 = new TreeMap<String, ArrayList<String>>();

			for (Record[] rrset : new Record[][] { message.getAnswers(),
					message.getAdditionalResourceRecords() }) {
				for (Record rr : rrset) {
					Data d = rr.getPayload();
					if (d instanceof SRV
							&& NameUtil.idnEquals(qname, rr.getName())) {
						SRV srv = (SRV) d;
						if (!priorities.containsKey(srv.getPriority())) {
							priorities.put(srv.getPriority(),
									new ArrayList<SRV>(2));
						}
						priorities.get(srv.getPriority()).add(srv);
					}
					if (d instanceof A) {
						A arecord = (A) d;
						if (!ips4.containsKey(rr.getName())) {
							ips4.put(rr.getName(), new ArrayList<String>(3));
						}
						ips4.get(rr.getName()).add(arecord.toString());
					}
					if (d instanceof AAAA) {
						AAAA aaaa = (AAAA) d;
						if (!ips6.containsKey(rr.getName())) {
							ips6.put(rr.getName(), new ArrayList<String>(3));
						}
						ips6.get(rr.getName()).add("[" + aaaa.toString() + "]");
					}
				}
			}

			Random rnd = new Random();
			ArrayList<SRV> result = new ArrayList<SRV>(
					priorities.size() * 2 + 1);
			for (ArrayList<SRV> s : priorities.values()) {

				// trivial case
				if (s.size() <= 1) {
					result.addAll(s);
					continue;
				}

				long totalweight = 0l;
				for (SRV srv : s) {
					totalweight += srv.getWeight();
				}

				while (totalweight > 0l && s.size() > 0) {
					long p = (rnd.nextLong() & 0x7fffffffffffffffl)
							% totalweight;
					int i = 0;
					while (p > 0) {
						p -= s.get(i++).getPriority();
					}
					i--;
					// remove is expensive, but we have only a few entries
					// anyway
					SRV srv = s.remove(i);
					totalweight -= srv.getWeight();
					result.add(srv);
				}

				Collections.shuffle(s, rnd);
				result.addAll(s);

			}

			if (result.size() == 0) {
				namePort.putString("error", "nosrv");
				return namePort;
			}
			// we now have a list of servers to try :-)

			// classic name/port pair
			String resultName = result.get(0).getName();
			namePort.putString("name", resultName);
			namePort.putInt("port", result.get(0).getPort());

			if (ips4.containsKey(resultName)) {
				// we have an ip!
				ArrayList<String> ip = ips4.get(resultName);
				Collections.shuffle(ip, rnd);
				namePort.putString("ipv4", ip.get(0));
			}
			if (ips6.containsKey(resultName)) {
				ArrayList<String> ip = ips6.get(resultName);
				Collections.shuffle(ip, rnd);
				namePort.putString("ipv6", ip.get(0));
			}

			// add all other records
			int i = 0;
			for (SRV srv : result) {
				namePort.putString("name" + i, srv.getName());
				namePort.putInt("port" + i, srv.getPort());
				i++;
			}

		} catch (SocketTimeoutException e) {
			Log.d(Config.LOGTAG, "timeout during dns");
			namePort.putString("error", "timeout");
		} catch (Exception e) {
			Log.d(Config.LOGTAG, "unhandled exception in sub project");
			namePort.putString("error", "unhandled");
		}
		return namePort;
	}

	final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();

	public static String bytesToHex(byte[] bytes) {
		char[] hexChars = new char[bytes.length * 2];
		for (int j = 0; j < bytes.length; j++) {
			int v = bytes[j] & 0xFF;
			hexChars[j * 2] = hexArray[v >>> 4];
			hexChars[j * 2 + 1] = hexArray[v & 0x0F];
		}
		return new String(hexChars);
	}
}