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-rw-r--r--src/main/java/de/thedevstack/conversationsplus/utils/DNSHelper.java183
1 files changed, 183 insertions, 0 deletions
diff --git a/src/main/java/de/thedevstack/conversationsplus/utils/DNSHelper.java b/src/main/java/de/thedevstack/conversationsplus/utils/DNSHelper.java
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index 00000000..1eedfdfd
--- /dev/null
+++ b/src/main/java/de/thedevstack/conversationsplus/utils/DNSHelper.java
@@ -0,0 +1,183 @@
+package de.thedevstack.conversationsplus.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 de.thedevstack.conversationsplus.Config;
+import de.thedevstack.conversationsplus.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<Integer, ArrayList<SRV>> priorities = new TreeMap<>();
+ TreeMap<String, ArrayList<String>> ips4 = new TreeMap<>();
+ TreeMap<String, ArrayList<String>> 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<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<>(
+ 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) {
+ bundle.putString("error", "nosrv");
+ return bundle;
+ }
+ ArrayList<Bundle> values = new ArrayList<>();
+ for (SRV srv : result) {
+ if (ips6.containsKey(srv.getName())) {
+ values.add(createNamePortBundle(srv.getName(),srv.getPort(),ips6));
+ }
+ if (ips4.containsKey(srv.getName())) {
+ values.add(createNamePortBundle(srv.getName(),srv.getPort(),ips4));
+ }
+ values.add(createNamePortBundle(srv.getName(),srv.getPort(),null));
+ }
+ bundle.putParcelableArrayList("values", values);
+ } catch (SocketTimeoutException e) {
+ bundle.putString("error", "timeout");
+ } catch (Exception e) {
+ bundle.putString("error", "unhandled");
+ }
+ return bundle;
+ }
+
+ private static Bundle createNamePortBundle(String name, int port, TreeMap<String, ArrayList<String>> ips) {
+ Bundle namePort = new Bundle();
+ namePort.putString("name", name);
+ namePort.putInt("port", port);
+ if (ips!=null) {
+ ArrayList<String> ip = ips.get(name);
+ Collections.shuffle(ip, new Random());
+ namePort.putString("ip", ip.get(0));
+ }
+ 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);
+ }
+}