Search for best connection

To fix Connection for IPv6, use a kind of Round Trip Time to implement something like Happy Eyeballs

src/main/java/eu/siacs/conversations/utils/Resolver.java

@@ -7,8 +7,9 @@ import android.util.Log;
 
 import java.io.IOException;
 import java.lang.reflect.Field;
-import java.net.Inet4Address;
 import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.Socket;
 import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -38,7 +39,7 @@ import eu.siacs.conversations.services.XmppConnectionService;
 public class Resolver {
 
     private static final String DIRECT_TLS_SERVICE = "_xmpps-client";
-    private static final String STARTTLS_SERICE = "_xmpp-client";
+    private static final String STARTTLS_SERVICE = "_xmpp-client";
 
     private static XmppConnectionService SERVICE = null;
 
@@ -156,7 +157,7 @@ public class Resolver {
     }
 
     private static List<Result> resolveSrv(String domain, final boolean directTls) throws IOException {
-        DNSName dnsName = DNSName.from((directTls ? DIRECT_TLS_SERVICE : STARTTLS_SERICE) + "._tcp." + domain);
+        DNSName dnsName = DNSName.from((directTls ? DIRECT_TLS_SERVICE : STARTTLS_SERVICE) + "._tcp." + domain);
         ResolverResult<SRV> result = resolveWithFallback(dnsName, SRV.class);
         final List<Result> results = new ArrayList<>();
         final List<Thread> threads = new ArrayList<>();
@@ -164,24 +165,19 @@ public class Resolver {
             if (record.name.length() == 0 && record.priority == 0) {
                 continue;
             }
-            threads.add(new Thread(() -> {
-                final List<Result> ipv4s = resolveIp(record, A.class, result.isAuthenticData(), directTls);
-                if (ipv4s.size() == 0) {
-                    Result resolverResult = Result.fromRecord(record, directTls);
-                    resolverResult.authenticated = resolverResult.isAuthenticated();
-                    ipv4s.add(resolverResult);
-                }
-                synchronized (results) {
-                    results.addAll(ipv4s);
-                }
-
-            }));
             threads.add(new Thread(() -> {
                 final List<Result> ipv6s = resolveIp(record, AAAA.class, result.isAuthenticData(), directTls);
                 synchronized (results) {
                     results.addAll(ipv6s);
                 }
             }));
+            threads.add(new Thread(() -> {
+                final List<Result> ipv4s = resolveIp(record, A.class, result.isAuthenticData(), directTls);
+                synchronized (results) {
+                    results.addAll(ipv4s);
+                }
+
+            }));
         }
         for (Thread thread : threads) {
             thread.start();
@@ -189,6 +185,16 @@ public class Resolver {
         for (Thread thread : threads) {
             try {
                 thread.join();
+                if (results.size() == 0) {
+                    for (SRV record : result.getAnswersOrEmptySet()) {
+                        if (record.name.length() == 0 && record.priority == 0) {
+                            continue;
+                        }
+                        Result resolverResult = Result.fromRecord(record, directTls);
+                        resolverResult.authenticated = resolverResult.isAuthenticated();
+                        results.add(resolverResult);
+                    }
+                }
             } catch (InterruptedException e) {
                 return Collections.emptyList();
             }
@@ -204,6 +210,7 @@ public class Resolver {
                 Result resolverResult = Result.fromRecord(srv, directTls);
                 resolverResult.authenticated = results.isAuthenticData() && authenticated;
                 resolverResult.ip = record.getInetAddress();
+                resolverResult.rtt = rttTo(resolverResult.ip,resolverResult.port);
                 list.add(resolverResult);
             }
         } catch (Throwable t) {
@@ -215,12 +222,12 @@ public class Resolver {
     private static List<Result> resolveNoSrvRecords(DNSName dnsName, boolean withCnames) {
         List<Result> results = new ArrayList<>();
         try {
-            for (A a : resolveWithFallback(dnsName, A.class, false).getAnswersOrEmptySet()) {
-                results.add(Result.createDefault(dnsName, a.getInetAddress()));
-            }
             for (AAAA aaaa : resolveWithFallback(dnsName, AAAA.class, false).getAnswersOrEmptySet()) {
                 results.add(Result.createDefault(dnsName, aaaa.getInetAddress()));
             }
+            for (A a : resolveWithFallback(dnsName, A.class, false).getAnswersOrEmptySet()) {
+                results.add(Result.createDefault(dnsName, a.getInetAddress()));
+            }
             if (results.size() == 0 && withCnames) {
                 for (CNAME cname : resolveWithFallback(dnsName, CNAME.class, false).getAnswersOrEmptySet()) {
                     results.addAll(resolveNoSrvRecords(cname.name, false));
@@ -254,6 +261,18 @@ public class Resolver {
         return ResolverApi.INSTANCE.resolve(question);
     }
 
+    private static long rttTo(InetAddress ip, int port){
+        long time = System.currentTimeMillis();
+        try (Socket s = new Socket()) {
+            s.connect(new InetSocketAddress(ip, port), 200);
+            s.close();
+            return System.currentTimeMillis() - time;
+        }catch (Exception e){
+            Log.e(Config.LOGTAG, Resolver.class.getSimpleName() + ": error testing connection to " + (ip == null ? null : ip.getHostAddress()) + ":" + port);
+            return -1;
+        }
+    }
+
     private static boolean validateHostname() {
         return SERVICE != null && SERVICE.getBooleanPreference("validate_hostname", R.bool.validate_hostname);
     }
@@ -272,6 +291,7 @@ public class Resolver {
         private boolean directTls = false;
         private boolean authenticated = false;
         private int priority;
+        private long rtt = -1;
 
         static Result fromRecord(SRV srv, boolean directTls) {
             Result result = new Result();
@@ -287,6 +307,9 @@ public class Resolver {
             result.port = 5222;
             result.hostname = hostname;
             result.ip = ip;
+            if (ip != null) {
+                result.rtt = rttTo(result.ip, result.port);
+            }
             return result;
         }
 
@@ -365,6 +388,7 @@ public class Resolver {
                     ", directTls=" + directTls +
                     ", authenticated=" + authenticated +
                     ", priority=" + priority +
+                    ", rtt=" + rtt +
                     '}';
         }
 
@@ -375,11 +399,10 @@ public class Resolver {
                     if (ip == null && result.ip == null) {
                         return 0;
                     } else if (ip != null && result.ip != null) {
-                        if (ip instanceof Inet4Address && result.ip instanceof Inet4Address) {
+                        if (rtt == -1 || result.rtt == -1) {
-                            return 0;
+                            Log.e(Config.LOGTAG, Resolver.class.getSimpleName() + ": unable to read round trip time servers on compare between "+toString()+ " and "+result.toString());
-                        } else {
-                            return ip instanceof Inet4Address ? -1 : 1;
                         }
+                        return rtt < result.rtt ? -1 : 1;
                     } else {
                         return ip != null ? -1 : 1;
                     }