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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.Data;
import java.io.IOException;
import java.net.InetAddress;
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 {
Log.d("xmppService", "using dns server: " + dnsServer.getHostAddress()
+ " to look up " + host);
DNSMessage message =
client.query(
"_xmpp-client._tcp." + host,
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>>();
for (Record rr : message.getAnswers()) {
Data d = rr.getPayload();
if (d instanceof SRV) {
SRV srv = (SRV) d;
if (!priorities.containsKey(srv.getPriority())) {
priorities.put(srv.getPriority(), new ArrayList<SRV>(2));
}
priorities.get(srv.getPriority()).add(srv);
}
}
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
namePort.putString("name", result.get(0).getName());
namePort.putInt("port", result.get(0).getPort());
// 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 (IOException e) {
Log.e("xmppService", "io execpiton during dns", e);
namePort.putString("error", "timeout");
}
return namePort;
}
static int calcPort(byte hb, byte lb) {
int port = ((int) hb << 8) | ((int) lb & 0xFF);
if (port >= 0) {
return port;
} else {
return 65536 + port;
}
}
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);
}
}
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