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.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 { 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> priorities = new TreeMap>(); 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(2)); } priorities.get(srv.getPriority()).add(srv); } } Random rnd = new Random(); ArrayList result = new ArrayList(priorities.size() * 2 + 1); for (ArrayList 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 (SocketTimeoutException e) { Log.d("xmppService", "timeout during dns"); namePort.putString("error", "timeout"); } catch (IOException e) { Log.d("xmppService","io exception during dns"); namePort.putString("error", "timeout"); } 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); } }