Report failed DNS SRV lookup in ConnectionException

instead of just logging a warning if the XMPP domain has no DNS SRV
lookups, create the failedAddresses list now within DNSUtil and add the
information that the SRV lookup failed.

smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java

@@ -573,8 +573,10 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
     /**
      * Populates {@link #hostAddresses} with at least one host address.
      *
+     * @return a list of host addresses where DNS (SRV) RR resolution failed.
      */
-    protected void populateHostAddresses() {
+    protected List<HostAddress> populateHostAddresses() {
+        List<HostAddress> failedAddresses = new LinkedList<>();
         // N.B.: Important to use config.serviceName and not AbstractXMPPConnection.serviceName
         if (config.host != null) {
             hostAddresses = new ArrayList<HostAddress>(1);
@@ -582,11 +584,12 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
             hostAddress = new HostAddress(config.host, config.port);
             hostAddresses.add(hostAddress);
         } else {
-            hostAddresses = DNSUtil.resolveXMPPDomain(config.serviceName);
+            hostAddresses = DNSUtil.resolveXMPPDomain(config.serviceName, failedAddresses);
         }
         // If we reach this, then hostAddresses *must not* be empty, i.e. there is at least one host added, either the
         // config.host one or the host representing the service name by DNSUtil
         assert(!hostAddresses.isEmpty());
+        return failedAddresses;
     }
 
     protected Lock getConnectionLock() {

smack-core/src/main/java/org/jivesoftware/smack/util/DNSUtil.java

@@ -105,10 +105,11 @@ public class DNSUtil {
      * </p>
      *
      * @param domain the domain.
+     * @param failedAddresses on optional list that will be populated with host addresses that failed to resolve.
      * @return List of HostAddress, which encompasses the hostname and port that the
      *      XMPP server can be reached at for the specified domain.
      */
-    public static List<HostAddress> resolveXMPPDomain(String domain) {
+    public static List<HostAddress> resolveXMPPDomain(String domain, List<HostAddress> failedAddresses) {
         domain = idnaTransformer.transform(domain);
         if (dnsResolver == null) {
             LOGGER.warning("No DNS Resolver active in Smack, will be unable to perform DNS SRV lookups");
@@ -116,7 +117,7 @@ public class DNSUtil {
             addresses.add(new HostAddress(domain, 5222));
             return addresses;
         }
-        return resolveDomain(domain, DomainType.Client);
+        return resolveDomain(domain, DomainType.Client, failedAddresses);
     }
 
     /**
@@ -129,10 +130,11 @@ public class DNSUtil {
      * </p>
      *
      * @param domain the domain.
+     * @param failedAddresses on optional list that will be populated with host addresses that failed to resolve.
      * @return List of HostAddress, which encompasses the hostname and port that the
      *      XMPP server can be reached at for the specified domain.
      */
-    public static List<HostAddress> resolveXMPPServerDomain(String domain) {
+    public static List<HostAddress> resolveXMPPServerDomain(String domain, List<HostAddress> failedAddresses) {
         domain = idnaTransformer.transform(domain);
         if (dnsResolver == null) {
             LOGGER.warning("No DNS Resolver active in Smack, will be unable to perform DNS SRV lookups");
@@ -140,10 +142,17 @@ public class DNSUtil {
             addresses.add(new HostAddress(domain, 5269));
             return addresses;
         }
-        return resolveDomain(domain, DomainType.Server);
+        return resolveDomain(domain, DomainType.Server, failedAddresses);
     }
 
-    private static List<HostAddress> resolveDomain(String domain, DomainType domainType) {
+    /**
+     * 
+     * @param domain the domain.
+     * @param domainType the XMPP domain type, server or client.
+     * @param failedAddresses on optional list that will be populated with host addresses that failed to resolve.
+     * @return a list of resolver host addresses for this domain.
+     */
+    private static List<HostAddress> resolveDomain(String domain, DomainType domainType, List<HostAddress> failedAddresses) {
         List<HostAddress> addresses = new ArrayList<HostAddress>();
 
         // Step one: Do SRV lookups
@@ -172,6 +181,11 @@ public class DNSUtil {
         catch (Exception e) {
             LOGGER.log(Level.WARNING, "Exception while resovling SRV records for " + domain
                             + ". Consider adding '_xmpp-(server|client)._tcp' DNS SRV Records", e);
+            if (failedAddresses != null) {
+                HostAddress failedHostAddress = new HostAddress(srvDomain);
+                failedHostAddress.setException(e);
+                failedAddresses.add(failedHostAddress);
+            }
         }
 
         // Step two: Add the hostname to the end of the list

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java

@@ -517,9 +517,7 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
     }
 
     private void connectUsingConfiguration() throws IOException, ConnectionException {
-        populateHostAddresses();
+        List<HostAddress> failedAddresses = populateHostAddresses();
-
-        List<HostAddress> failedAddresses = new LinkedList<HostAddress>();
         SocketFactory socketFactory = config.getSocketFactory();
         if (socketFactory == null) {
             socketFactory = SocketFactory.getDefault();