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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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70
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
* reached at for client-to-server communication. A DNS lookup for a SRV
* record in the form "_xmpp-client._tcp.example.com" is attempted, according
* to section 14.4 of RFC 3920. If that lookup fails, a lookup in the older form
* of "_jabber._tcp.example.com" is attempted since servers that implement an
* 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>
*
* Returns a list of HostAddresses under which the specified XMPP server can be reached at for client-to-server
* communication. A DNS lookup for a SRV 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
* 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".
* </p>
*
* @param domain the domain.
* @return List of HostAddress, which encompasses the hostname and port that the
* XMPP server can be reached at for the specified domain.
* @throws Exception
* @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(final String domain) throws Exception {
public static List<HostAddress> resolveXMPPDomain(final String domain) {
if (dnsResolver == null) {
List<HostAddress> addresses = new ArrayList<HostAddress>(1);
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
* reached at for server-to-server communication. A DNS lookup for a SRV
* record in the form "_xmpp-server._tcp.example.com" is attempted, according
* to section 14.4 of RFC 3920. If that lookup fails, a lookup in the older form
* of "_jabber._tcp.example.com" is attempted since servers that implement an
* 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>
*
* Returns a list of HostAddresses under which the specified XMPP server can be reached at for server-to-server
* communication. A DNS lookup for a SRV 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
* 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".
* </p>
*
* @param domain the domain.
* @return List of HostAddress, which encompasses the hostname and port that the
* XMPP server can be reached at for the specified domain.
* @throws Exception
* @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(final String domain) throws Exception {
public static List<HostAddress> resolveXMPPServerDomain(final String domain) {
if (dnsResolver == null) {
List<HostAddress> addresses = new ArrayList<HostAddress>(1);
addresses.add(new HostAddress(domain, 5269));
@ -138,7 +128,7 @@ public class DNSUtil {
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>();
// Step one: Do SRV lookups
@ -150,15 +140,21 @@ public class DNSUtil {
} else {
srvDomain = domain;
}
List<SRVRecord> srvRecords = dnsResolver.lookupSRVRecords(srvDomain);
if (LOGGER.isLoggable(Level.FINE)) {
String logMessage = "Resolved SRV RR for " + srvDomain + ":";
for (SRVRecord r : srvRecords)
logMessage += " " + r;
LOGGER.fine(logMessage);
try {
List<SRVRecord> srvRecords = dnsResolver.lookupSRVRecords(srvDomain);
if (LOGGER.isLoggable(Level.FINE)) {
String logMessage = "Resolved SRV RR for " + srvDomain + ":";
for (SRVRecord r : srvRecords)
logMessage += " " + r;
LOGGER.fine(logMessage);
}
List<HostAddress> sortedRecords = sortSRVRecords(srvRecords);
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");
}
List<HostAddress> sortedRecords = sortSRVRecords(srvRecords);
addresses.addAll(sortedRecords);
// Step two: Add the hostname to the end of the list
addresses.add(new HostAddress(domain));