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 eu.siacs.conversations.xmpp.jid.Jid; 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(final Jid jid) throws IOException { final String host = jid.getDomainpart(); String dns[] = client.findDNS(); if (dns != null) { for (String dnsserver : dns) { InetAddress ip = InetAddress.getByName(dnsserver); Bundle b = queryDNS(host, ip); if (b.containsKey("values")) { return b; } else if (b.containsKey("error") && "nosrv".equals(b.getString("error", null))) { return b; } } } return queryDNS(host, InetAddress.getByName("8.8.8.8")); } public static Bundle queryDNS(String host, InetAddress dnsServer) { Bundle bundle = 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> priorities = new TreeMap<>(); TreeMap> ips4 = new TreeMap<>(); TreeMap> ips6 = new TreeMap<>(); 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(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(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(3)); } ips6.get(rr.getName()).add("[" + aaaa.toString() + "]"); } } } 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) { bundle.putString("error", "nosrv"); return bundle; } ArrayList values = new ArrayList<>(); for (SRV srv : result) { Bundle namePort = new Bundle(); namePort.putString("name", srv.getName()); namePort.putInt("port", srv.getPort()); if (ips6.containsKey(srv.getName())) { ArrayList ip = ips6.get(srv.getName()); Collections.shuffle(ip, rnd); namePort.putString("ip", ip.get(0)); values.add(namePort); } if (ips4.containsKey(srv.getName())) { ArrayList ip = ips4.get(srv.getName()); Collections.shuffle(ip, rnd); namePort.putString("ip", ip.get(0)); values.add(namePort); } if (!ips6.containsKey(srv.getName()) && !ips4.containsKey(srv.getName())) { values.add(namePort); } } bundle.putParcelableArrayList("values", values); } catch (SocketTimeoutException e) { bundle.putString("error", "timeout"); } catch (Exception e) { bundle.putString("error", "unhandled"); } return bundle; } 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); } }