1package eu.siacs.conversations.utils;
2
3import de.measite.minidns.Client;
4import de.measite.minidns.DNSMessage;
5import de.measite.minidns.Record;
6import de.measite.minidns.Record.TYPE;
7import de.measite.minidns.Record.CLASS;
8import de.measite.minidns.record.SRV;
9import de.measite.minidns.record.A;
10import de.measite.minidns.record.AAAA;
11import de.measite.minidns.record.Data;
12import de.measite.minidns.util.NameUtil;
13
14import java.io.IOException;
15import java.net.InetAddress;
16import java.util.ArrayList;
17import java.util.Collections;
18import java.util.Random;
19import java.util.TreeMap;
20
21import android.os.Bundle;
22import android.util.Log;
23
24public class DNSHelper {
25 protected static Client client = new Client();
26
27 public static Bundle getSRVRecord(String host) throws IOException {
28 String dns[] = client.findDNS();
29
30 if (dns != null) {
31 // we have a list of DNS servers, let's go
32 for (String dnsserver : dns) {
33 InetAddress ip = InetAddress.getByName(dnsserver);
34 Bundle b = queryDNS(host, ip);
35 if (b.containsKey("name")) {
36 return b;
37 }
38 }
39 }
40
41 // fallback
42 return queryDNS(host, InetAddress.getByName("8.8.8.8"));
43 }
44
45 public static Bundle queryDNS(String host, InetAddress dnsServer) {
46 Bundle namePort = new Bundle();
47 try {
48 String qname = "_xmpp-client._tcp." + host;
49 Log.d("xmppService", "using dns server: " + dnsServer.getHostAddress()
50 + " to look up " + host);
51 DNSMessage message =
52 client.query(
53 qname,
54 TYPE.ANY,
55 CLASS.IN,
56 dnsServer.getHostAddress());
57
58 // How should we handle priorities and weight?
59 // Wikipedia has a nice article about priorities vs. weights:
60 // https://en.wikipedia.org/wiki/SRV_record#Provisioning_for_high_service_availability
61
62 // we bucket the SRV records based on priority, pick per priority
63 // a random order respecting the weight, and dump that priority by
64 // priority
65
66 TreeMap<Integer, ArrayList<SRV>> priorities =
67 new TreeMap<Integer, ArrayList<SRV>>();
68 TreeMap<String, ArrayList<String>> ips4 =
69 new TreeMap<String, ArrayList<String>>();
70 TreeMap<String, ArrayList<String>> ips6 =
71 new TreeMap<String, ArrayList<String>>();
72
73 for (Record[] rrset : new Record[][]{ message.getAnswers(),
74 message.getAdditionalResourceRecords()}) {
75 for (Record rr : rrset) {
76 Data d = rr.getPayload();
77 if (d instanceof SRV && NameUtil.idnEquals(qname,rr.getName())) {
78 SRV srv = (SRV) d;
79 if (!priorities.containsKey(srv.getPriority())) {
80 priorities.put(srv.getPriority(), new ArrayList<SRV>(2));
81 }
82 priorities.get(srv.getPriority()).add(srv);
83 }
84 if (d instanceof A) {
85 A arecord = (A) d;
86 if (!ips4.containsKey(rr.getName())) {
87 ips4.put(rr.getName(), new ArrayList<String>(3));
88 }
89 ips4.get(rr.getName()).add(arecord.toString());
90 }
91 if (d instanceof AAAA) {
92 AAAA aaaa = (AAAA) d;
93 if (!ips6.containsKey(rr.getName())) {
94 ips6.put(rr.getName(), new ArrayList<String>(3));
95 }
96 ips6.get(rr.getName()).add("[" + aaaa.toString() + "]");
97 }
98 }
99 }
100
101 Random rnd = new Random();
102 ArrayList<SRV> result = new ArrayList<SRV>(priorities.size() * 2 + 1);
103 for (ArrayList<SRV> s: priorities.values()) {
104
105 // trivial case
106 if (s.size() <= 1) {
107 result.addAll(s);
108 continue;
109 }
110
111 long totalweight = 0l;
112 for (SRV srv: s) {
113 totalweight += srv.getWeight();
114 }
115
116 while (totalweight > 0l && s.size() > 0) {
117 long p = (rnd.nextLong() & 0x7fffffffffffffffl) % totalweight;
118 int i = 0;
119 while (p > 0) {
120 p -= s.get(i++).getPriority();
121 }
122 i--;
123 // remove is expensive, but we have only a few entries anyway
124 SRV srv = s.remove(i);
125 totalweight -= srv.getWeight();
126 result.add(srv);
127 }
128
129 Collections.shuffle(s, rnd);
130 result.addAll(s);
131
132 }
133
134 if (result.size() == 0) {
135 namePort.putString("error", "nosrv");
136 return namePort;
137 }
138 // we now have a list of servers to try :-)
139
140 // classic name/port pair
141 String resultName = result.get(0).getName();
142 namePort.putString("name", resultName);
143 namePort.putInt("port", result.get(0).getPort());
144
145 if (ips4.containsKey(resultName)) {
146 // we have an ip!
147 ArrayList<String> ip = ips4.get(resultName);
148 Collections.shuffle(ip, rnd);
149 namePort.putString("ipv4", ip.get(0));
150 }
151 if (ips6.containsKey(resultName)) {
152 ArrayList<String> ip = ips6.get(resultName);
153 Collections.shuffle(ip, rnd);
154 namePort.putString("ipv6", ip.get(0));
155 }
156
157 // add all other records
158 int i = 0;
159 for (SRV srv : result) {
160 namePort.putString("name" + i, srv.getName());
161 namePort.putInt("port" + i, srv.getPort());
162 i++;
163 }
164
165 } catch (IOException e) {
166 Log.e("xmppService", "io execpiton during dns", e);
167 namePort.putString("error", "timeout");
168 }
169 return namePort;
170 }
171
172 static int calcPort(byte hb, byte lb) {
173 int port = ((int) hb << 8) | ((int) lb & 0xFF);
174 if (port >= 0) {
175 return port;
176 } else {
177 return 65536 + port;
178 }
179 }
180
181 final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
182
183 public static String bytesToHex(byte[] bytes) {
184 char[] hexChars = new char[bytes.length * 2];
185 for (int j = 0; j < bytes.length; j++) {
186 int v = bytes[j] & 0xFF;
187 hexChars[j * 2] = hexArray[v >>> 4];
188 hexChars[j * 2 + 1] = hexArray[v & 0x0F];
189 }
190 return new String(hexChars);
191 }
192}