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Fallback to host if DNS SRV lookup fails

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Also fix javadoc for DNSUtil, _jabber SRV records are no longer tried.

Fixes SMACK-616.
This commit is contained in:
Florian Schmaus 2014-11-10 21:17:55 +01:00
parent 1ade4cbc64
commit 4000adb70c
1 changed files with 33 additions and 37 deletions
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54
smack-core/src/main/java/org/jivesoftware/smack/util/DNSUtil.java
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@ -85,24 +85,19 @@ public class DNSUtil {
} }
/** /**
* Returns a list of HostAddresses under which the specified XMPP server can be * Returns a list of HostAddresses under which the specified XMPP server can be reached at for client-to-server
* reached at for client-to-server communication. A DNS lookup for a SRV * communication. A DNS lookup for a SRV record in the form "_xmpp-client._tcp.example.com" is attempted, according
* record in the form "_xmpp-client._tcp.example.com" is attempted, according * to section 3.2.1 of RFC 6120. If that lookup fails, it's assumed that the XMPP server lives at the host resolved
* to section 14.4 of RFC 3920. If that lookup fails, a lookup in the older form * by a DNS lookup at the specified domain on the default port of 5222.
* of "_jabber._tcp.example.com" is attempted since servers that implement an * <p>
* older version of the protocol may be listed using that notation. If that
* lookup fails as well, it's assumed that the XMPP server lives at the
* host resolved by a DNS lookup at the specified domain on the default port
* of 5222.<p>
*
* As an example, a lookup for "example.com" may return "im.example.com:5269". * As an example, a lookup for "example.com" may return "im.example.com:5269".
* </p>
* *
* @param domain the domain. * @param domain the domain.
* @return List of HostAddress, which encompasses the hostname and port that the * @return List of HostAddress, which encompasses the hostname and port that the XMPP server can be reached at for
* XMPP server can be reached at for the specified domain. * the specified domain.
* @throws Exception
*/ */
public static List<HostAddress> resolveXMPPDomain(final String domain) throws Exception { public static List<HostAddress> resolveXMPPDomain(final String domain) {
if (dnsResolver == null) { if (dnsResolver == null) {
List<HostAddress> addresses = new ArrayList<HostAddress>(1); List<HostAddress> addresses = new ArrayList<HostAddress>(1);
addresses.add(new HostAddress(domain, 5222)); addresses.add(new HostAddress(domain, 5222));
@ -112,24 +107,19 @@ public class DNSUtil {
} }
/** /**
* Returns a list of HostAddresses under which the specified XMPP server can be * Returns a list of HostAddresses under which the specified XMPP server can be reached at for server-to-server
* reached at for server-to-server communication. A DNS lookup for a SRV * communication. A DNS lookup for a SRV record in the form "_xmpp-server._tcp.example.com" is attempted, according
* record in the form "_xmpp-server._tcp.example.com" is attempted, according * to section 3.2.1 of RFC 6120. If that lookup fails , it's assumed that the XMPP server lives at the host resolved
* to section 14.4 of RFC 3920. If that lookup fails, a lookup in the older form * by a DNS lookup at the specified domain on the default port of 5269.
* of "_jabber._tcp.example.com" is attempted since servers that implement an * <p>
* older version of the protocol may be listed using that notation. If that
* lookup fails as well, it's assumed that the XMPP server lives at the
* host resolved by a DNS lookup at the specified domain on the default port
* of 5269.<p>
*
* As an example, a lookup for "example.com" may return "im.example.com:5269". * As an example, a lookup for "example.com" may return "im.example.com:5269".
* </p>
* *
* @param domain the domain. * @param domain the domain.
* @return List of HostAddress, which encompasses the hostname and port that the * @return List of HostAddress, which encompasses the hostname and port that the XMPP server can be reached at for
* XMPP server can be reached at for the specified domain. * the specified domain.
* @throws Exception
*/ */
public static List<HostAddress> resolveXMPPServerDomain(final String domain) throws Exception { public static List<HostAddress> resolveXMPPServerDomain(final String domain) {
if (dnsResolver == null) { if (dnsResolver == null) {
List<HostAddress> addresses = new ArrayList<HostAddress>(1); List<HostAddress> addresses = new ArrayList<HostAddress>(1);
addresses.add(new HostAddress(domain, 5269)); addresses.add(new HostAddress(domain, 5269));
@ -138,7 +128,7 @@ public class DNSUtil {
return resolveDomain(domain, 's'); return resolveDomain(domain, 's');
} }
private static List<HostAddress> resolveDomain(String domain, char keyPrefix) throws Exception { private static List<HostAddress> resolveDomain(String domain, char keyPrefix) {
List<HostAddress> addresses = new ArrayList<HostAddress>(); List<HostAddress> addresses = new ArrayList<HostAddress>();
// Step one: Do SRV lookups // Step one: Do SRV lookups
@ -150,6 +140,7 @@ public class DNSUtil {
} else { } else {
srvDomain = domain; srvDomain = domain;
} }
try {
List<SRVRecord> srvRecords = dnsResolver.lookupSRVRecords(srvDomain); List<SRVRecord> srvRecords = dnsResolver.lookupSRVRecords(srvDomain);
if (LOGGER.isLoggable(Level.FINE)) { if (LOGGER.isLoggable(Level.FINE)) {
String logMessage = "Resolved SRV RR for " + srvDomain + ":"; String logMessage = "Resolved SRV RR for " + srvDomain + ":";
@ -159,6 +150,11 @@ public class DNSUtil {
} }
List<HostAddress> sortedRecords = sortSRVRecords(srvRecords); List<HostAddress> sortedRecords = sortSRVRecords(srvRecords);
addresses.addAll(sortedRecords); addresses.addAll(sortedRecords);
}
catch (Exception e) {
LOGGER.log(Level.WARNING, "Exception while resovling SRV records for " + domain
+ ". Consider adding '_xmpp-(server|client)._tcp' DNS SRV Records");
}
// Step two: Add the hostname to the end of the list // Step two: Add the hostname to the end of the list
addresses.add(new HostAddress(domain)); addresses.add(new HostAddress(domain));