diff options
Diffstat (limited to 'conversations/src/main/java/eu/siacs/conversations/utils/DNSHelper.java')
| -rw-r--r-- | conversations/src/main/java/eu/siacs/conversations/utils/DNSHelper.java | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/conversations/src/main/java/eu/siacs/conversations/utils/DNSHelper.java b/conversations/src/main/java/eu/siacs/conversations/utils/DNSHelper.java new file mode 100644 index 00000000..c51a75ac --- /dev/null +++ b/conversations/src/main/java/eu/siacs/conversations/utils/DNSHelper.java @@ -0,0 +1,185 @@ +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) { + for (String dnsserver : dns) { + InetAddress ip = InetAddress.getByName(dnsserver); + Bundle b = queryDNS(host, ip); + if (b.containsKey("name")) { + 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 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) { + namePort.putString("error", "timeout"); + } catch (Exception e) { + 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); + } +} |