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Code Issues Releases Wiki Activity

SMACK-225 Fixed DNS SRV handling, as per RFC 2782. Added support for multiple DNS SRV resolvers namely javax and org.xbill.dns (aka dnsjava).

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git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/branches/smack_3_3_0@13561 b35dd754-fafc-0310-a699-88a17e54d16e
This commit is contained in:
Florian Schmaus 2013-03-18 08:53:11 +00:00 • committed by flow
parent 21be8c55ee
commit 2eb13f48d2
12 changed files with 756 additions and 210 deletions
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318
source/org/jivesoftware/smack/util/DNSUtil.java
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@ -19,18 +19,20 @@
package org.jivesoftware.smack.util;
import java.util.Hashtable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
import javax.naming.NamingEnumeration;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
import org.jivesoftware.smack.util.dns.DNSResolver;
import org.jivesoftware.smack.util.dns.HostAddress;
import org.jivesoftware.smack.util.dns.SRVRecord;
/**
* Utilty class to perform DNS lookups for XMPP services.
* Utility class to perform DNS lookups for XMPP services.
*
* @author Matt Tucker
*/
@ -40,23 +42,30 @@ public class DNSUtil {
* Create a cache to hold the 100 most recently accessed DNS lookups for a period of
* 10 minutes.
*/
private static Map<String, HostAddress> cache = new Cache<String, HostAddress>(100, 1000*60*10);
private static Map<String, List<HostAddress>> cache = new Cache<String, List<HostAddress>>(100, 1000*60*10);
private static DirContext context;
private static DNSResolver dnsResolver = null;
static {
try {
Hashtable<String, String> env = new Hashtable<String, String>();
env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
context = new InitialDirContext(env);
}
catch (Exception e) {
// Ignore.
}
/**
* Set the DNS resolver that should be used to perform DNS lookups.
*
* @param resolver
*/
public static void setDNSResolver(DNSResolver resolver) {
dnsResolver = resolver;
}
/**
* Returns the host name and port that the specified XMPP server can be
* Returns the current DNS resolved used to perform DNS lookups.
*
* @return
*/
public static DNSResolver getDNSResolver() {
return dnsResolver;
}
/**
* 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
@ -67,81 +76,17 @@ public class DNSUtil {
* of 5222.<p>
*
* As an example, a lookup for "example.com" may return "im.example.com:5269".
*
* Note on SRV record selection.
* We now check priority and weight, but we still don't do this correctly.
* The missing behavior is this: if we fail to reach a host based on its SRV
* record then we need to select another host from the other SRV records.
* In Smack 3.1.1 we're not going to be able to do the major system redesign to
* correct this.
*
* @param domain the domain.
* @return a HostAddress, which encompasses the hostname and port that the XMPP
* server can be reached at for the specified domain.
* @return List of HostAddress, which encompasses the hostname and port that the
* XMPP server can be reached at for the specified domain.
*/
public static HostAddress resolveXMPPDomain(String domain) {
if (context == null) {
return new HostAddress(domain, 5222);
}
String key = "c" + domain;
// Return item from cache if it exists.
if (cache.containsKey(key)) {
HostAddress address = (HostAddress)cache.get(key);
if (address != null) {
return address;
}
}
String bestHost = domain;
int bestPort = 5222;
int bestPriority = 0;
int bestWeight = 0;
try {
Attributes dnsLookup = context.getAttributes("_xmpp-client._tcp." + domain, new String[]{"SRV"});
Attribute srvAttribute = dnsLookup.get("SRV");
NamingEnumeration<String> srvRecords = (NamingEnumeration<String>) srvAttribute.getAll();
while(srvRecords.hasMore()) {
String srvRecord = srvRecords.next();
String [] srvRecordEntries = srvRecord.split(" ");
int priority = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 4]);
int port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length-2]);
int weight = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 3]);
String host = srvRecordEntries[srvRecordEntries.length-1];
// Randomize the weight.
weight *= Math.random() * weight;
if ((bestPriority == 0) || (priority < bestPriority)) {
// Choose a server with the lowest priority.
bestPriority = priority;
bestWeight = weight;
bestHost = host;
bestPort = port;
} else if (priority == bestPriority) {
// When we have like priorities then randomly choose a server based on its weight
// The weights were randomized above.
if (weight > bestWeight) {
bestWeight = weight;
bestHost = host;
bestPort = port;
}
}
}
}
catch (Exception e) {
// Ignore.
}
// Host entries in DNS should end with a ".".
if (bestHost.endsWith(".")) {
bestHost = bestHost.substring(0, bestHost.length()-1);
}
HostAddress address = new HostAddress(bestHost, bestPort);
// Add item to cache.
cache.put(key, address);
return address;
public static List<HostAddress> resolveXMPPDomain(String domain) {
return resolveDomain(domain, 'c');
}
/**
* Returns the host name and port that 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 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
@ -154,104 +99,131 @@ public class DNSUtil {
* As an example, a lookup for "example.com" may return "im.example.com:5269".
*
* @param domain the domain.
* @return a HostAddress, which encompasses the hostname and port that the XMPP
* server can be reached at for the specified domain.
* @return List of HostAddress, which encompasses the hostname and port that the
* XMPP server can be reached at for the specified domain.
*/
public static HostAddress resolveXMPPServerDomain(String domain) {
if (context == null) {
return new HostAddress(domain, 5269);
}
String key = "s" + domain;
public static List<HostAddress> resolveXMPPServerDomain(String domain) {
return resolveDomain(domain, 's');
}
private static List<HostAddress> resolveDomain(String domain, char keyPrefix) {
// Prefix the key with 's' to distinguish him from the client domain lookups
String key = keyPrefix + domain;
// Return item from cache if it exists.
if (cache.containsKey(key)) {
HostAddress address = (HostAddress)cache.get(key);
if (address != null) {
return address;
List<HostAddress> addresses = cache.get(key);
if (addresses != null) {
return addresses;
}
}
String host = domain;
int port = 5269;
try {
Attributes dnsLookup =
context.getAttributes("_xmpp-server._tcp." + domain, new String[]{"SRV"});
String srvRecord = (String)dnsLookup.get("SRV").get();
String [] srvRecordEntries = srvRecord.split(" ");
port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length-2]);
host = srvRecordEntries[srvRecordEntries.length-1];
if (dnsResolver == null)
throw new IllegalStateException("No DNS resolver active.");
List<HostAddress> addresses = new ArrayList<HostAddress>();
// Step one: Do SRV lookups
String srvDomain;
if (keyPrefix == 's') {
srvDomain = "_xmpp-server._tcp." + domain;
} else if (keyPrefix == 'c') {
srvDomain = "_xmpp-client._tcp." + domain;
} else {
srvDomain = domain;
}
catch (Exception e) {
// Attempt lookup with older "jabber" name.
try {
Attributes dnsLookup =
context.getAttributes("_jabber._tcp." + domain, new String[]{"SRV"});
String srvRecord = (String)dnsLookup.get("SRV").get();
String [] srvRecordEntries = srvRecord.split(" ");
port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length-2]);
host = srvRecordEntries[srvRecordEntries.length-1];
}
catch (Exception e2) {
// Ignore.
}
}
// Host entries in DNS should end with a ".".
if (host.endsWith(".")) {
host = host.substring(0, host.length()-1);
}
HostAddress address = new HostAddress(host, port);
List<SRVRecord> srvRecords = dnsResolver.lookupSRVRecords(srvDomain);
List<HostAddress> sortedRecords = sortSRVRecords(srvRecords);
if (sortedRecords != null)
addresses.addAll(sortedRecords);
// Step two: Add the hostname to the end of the list
addresses.add(new HostAddress(domain));
// Add item to cache.
cache.put(key, address);
return address;
cache.put(key, addresses);
return addresses;
}
/**
* Encapsulates a hostname and port.
* Sort a given list of SRVRecords as described in RFC 2782
* Note that we follow the RFC with one exception. In a group of the same priority, only the first entry
* is calculated by random. The others are ore simply ordered by their priority.
*
* @param records
* @return
*/
public static class HostAddress {
protected static List<HostAddress> sortSRVRecords(List<SRVRecord> records) {
// RFC 2782, Usage rules: "If there is precisely one SRV RR, and its Target is "."
// (the root domain), abort."
if (records.size() == 1 && records.get(0).getFQDN().equals("."))
return null;
private String host;
private int port;
// sorting the records improves the performance of the bisection later
Collections.sort(records);
private HostAddress(String host, int port) {
this.host = host;
this.port = port;
}
/**
* Returns the hostname.
*
* @return the hostname.
*/
public String getHost() {
return host;
}
/**
* Returns the port.
*
* @return the port.
*/
public int getPort() {
return port;
}
public String toString() {
return host + ":" + port;
}
public boolean equals(Object o) {
if (this == o) {
return true;
// create the priority buckets
SortedMap<Integer, List<SRVRecord>> buckets = new TreeMap<Integer, List<SRVRecord>>();
for (SRVRecord r : records) {
Integer priority = r.getPriority();
List<SRVRecord> bucket = buckets.get(priority);
// create the list of SRVRecords if it doesn't exist
if (bucket == null) {
bucket = new LinkedList<SRVRecord>();
buckets.put(priority, bucket);
}
if (!(o instanceof HostAddress)) {
return false;
}
final HostAddress address = (HostAddress) o;
if (!host.equals(address.host)) {
return false;
}
return port == address.port;
bucket.add(r);
}
List<HostAddress> res = new ArrayList<HostAddress>(records.size());
for (Integer priority : buckets.keySet()) {
List<SRVRecord> bucket = buckets.get(priority);
int bucketSize;
while ((bucketSize = bucket.size()) > 0) {
int[] totals = new int[bucket.size()];
int running_total = 0;
int count = 0;
int zeroWeight = 1;
for (SRVRecord r : bucket) {
if (r.getWeight() > 0)
zeroWeight = 0;
}
for (SRVRecord r : bucket) {
running_total += (r.getWeight() + zeroWeight);
totals[count] = running_total;
count++;
}
int selectedPos;
if (running_total == 0) {
// If running total is 0, then all weights in this priority
// group are 0. So we simply select one of the weights randomly
// as the other 'normal' algorithm is unable to handle this case
selectedPos = (int) (Math.random() * bucketSize);
} else {
double rnd = Math.random() * running_total;
selectedPos = bisect(totals, rnd);
}
// add the SRVRecord that was randomly chosen on it's weight
// to the start of the result list
SRVRecord chosenSRVRecord = bucket.remove(selectedPos);
res.add(chosenSRVRecord);
}
}
return res;
}
// TODO this is not yet really bisection just a stupid linear search
private static int bisect(int[] array, double value) {
int pos = 0;
for (int element : array) {
if (value < element)
break;
pos++;
}
return pos;
}
}

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source/org/jivesoftware/smack/util/dns/DNSJavaResolver.java Normal file
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@ -0,0 +1,72 @@
/**
* Copyright 2013 Florian Schmaus
*
* All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smack.util.dns;
import java.util.ArrayList;
import java.util.List;
import org.xbill.DNS.Lookup;
import org.xbill.DNS.Record;
import org.xbill.DNS.Type;
public class DNSJavaResolver extends DNSResolver {
private static DNSJavaResolver instance;
private DNSJavaResolver() {
}
public static DNSResolver getInstance() {
if (instance == null) {
instance = new DNSJavaResolver();
}
return instance;
}
@Override
public List<SRVRecord> lookupSRVRecords(String name) {
List<SRVRecord> res = new ArrayList<SRVRecord>();
try {
Lookup lookup = new Lookup(name, Type.SRV);
Record recs[] = lookup.run();
if (recs == null)
return res;
for (Record record : recs) {
org.xbill.DNS.SRVRecord srvRecord = (org.xbill.DNS.SRVRecord) record;
if (srvRecord != null && srvRecord.getTarget() != null) {
String host = srvRecord.getTarget().toString();
int port = srvRecord.getPort();
int priority = srvRecord.getPriority();
int weight = srvRecord.getWeight();
SRVRecord r;
try {
r = new SRVRecord(host, port, priority, weight);
} catch (Exception e) {
continue;
}
res.add(r);
}
}
} catch (Exception e) {
}
return res;
}
}

24
source/org/jivesoftware/smack/util/dns/DNSResolver.java Normal file
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@ -0,0 +1,24 @@
/**
* Copyright 2013 Florian Schmaus
*
* All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smack.util.dns;
import java.util.List;
public abstract class DNSResolver {
public abstract List<SRVRecord> lookupSRVRecords(String name);
}

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source/org/jivesoftware/smack/util/dns/HostAddress.java Normal file
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@ -0,0 +1,93 @@
/**
* Copyright 2013 Florian Schmaus
*
* All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smack.util.dns;
public class HostAddress {
private String fqdn;
private int port;
private Exception exception;
/**
* Creates a new HostAddress with the given FQDN. The port will be set to the default XMPP client port: 5222
*
* @param fqdn
* @throws IllegalArgumentException
*/
public HostAddress(String fqdn) throws IllegalArgumentException {
if (fqdn == null)
throw new IllegalArgumentException("FQDN is null");
if (fqdn.charAt(fqdn.length() - 1) == '.') {
this.fqdn = fqdn.substring(0, fqdn.length() - 1);
}
else {
this.fqdn = fqdn;
}
// Set port to the default port for XMPP client communication
this.port = 5222;
}
public HostAddress(String fqdn, int port) throws IllegalArgumentException {
this(fqdn);
if (port < 0 || port > 65535)
throw new IllegalArgumentException(
"DNS SRV records weight must be a 16-bit unsiged integer (i.e. between 0-65535. Port was: " + port);
this.port = port;
}
public String getFQDN() {
return fqdn;
}
public int getPort() {
return port;
}
public void setException(Exception e) {
this.exception = e;
}
public String toString() {
return fqdn + ":" + port;
}
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof HostAddress)) {
return false;
}
final HostAddress address = (HostAddress) o;
if (!fqdn.equals(address.fqdn)) {
return false;
}
return port == address.port;
}
public String getErrorMessage() {
String error;
if (exception == null) {
error = "No error logged";
}
else {
error = exception.getMessage();
}
return toString() + " Exception: " + error;
}
}

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source/org/jivesoftware/smack/util/dns/JavaxResolver.java Normal file
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@ -0,0 +1,99 @@
/**
* Copyright 2013 Florian Schmaus
*
* All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smack.util.dns;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import javax.naming.NamingEnumeration;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
import org.jivesoftware.smack.util.DNSUtil;
/**
* A DNS resolver (mostly for SRV records), which makes use of the API provided in the javax.* namepsace.
*
* @author Florian Schmaus
*
*/
public class JavaxResolver extends DNSResolver {
private static JavaxResolver instance;
private static DirContext dirContext;
static {
try {
Hashtable<String, String> env = new Hashtable<String, String>();
env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
dirContext = new InitialDirContext(env);
} catch (Exception e) {
// Ignore.
}
// Try to set this DNS resolver as primary one
DNSUtil.setDNSResolver(maybeGetInstance());
}
private JavaxResolver() {
}
public static DNSResolver maybeGetInstance() {
if (instance == null && isSupported()) {
instance = new JavaxResolver();
}
return instance;
}
public static boolean isSupported() {
return dirContext != null;
}
@Override
public List<SRVRecord> lookupSRVRecords(String name) {
List<SRVRecord> res = new ArrayList<SRVRecord>();
try {
Attributes dnsLookup = dirContext.getAttributes(name, new String[]{"SRV"});
Attribute srvAttribute = dnsLookup.get("SRV");
@SuppressWarnings("unchecked")
NamingEnumeration<String> srvRecords = (NamingEnumeration<String>) srvAttribute.getAll();
while (srvRecords.hasMore()) {
String srvRecordString = srvRecords.next();
String[] srvRecordEntries = srvRecordString.split(" ");
int priority = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 4]);
int port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 2]);
int weight = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 3]);
String host = srvRecordEntries[srvRecordEntries.length - 1];
SRVRecord srvRecord;
try {
srvRecord = new SRVRecord(host, port, priority, weight);
} catch (Exception e) {
continue;
}
res.add(srvRecord);
}
} catch (Exception e) {
}
return res;
}
}

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source/org/jivesoftware/smack/util/dns/SRVRecord.java Normal file
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@ -0,0 +1,77 @@
/**
* Copyright 2013 Florian Schmaus
*
* All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smack.util.dns;
/**
* @see <a href="http://tools.ietf.org/html/rfc2782>RFC 2782: A DNS RR for specifying the location of services (DNS
* SRV)<a>
* @author Florian Schmaus
*
*/
public class SRVRecord extends HostAddress implements Comparable<SRVRecord> {
private int weight;
private int priority;
/**
* Create a new SRVRecord
*
* @param fqdn
* @param port
* @param priority
* @param weight
* @throws IllegalArgumentException
*/
public SRVRecord(String fqdn, int port, int priority, int weight) throws IllegalArgumentException {
super(fqdn, port);
if (weight < 0 || weight > 65535)
throw new IllegalArgumentException(
"DNS SRV records weight must be a 16-bit unsiged integer (i.e. between 0-65535. Weight was: "
+ weight);
if (priority < 0 || priority > 65535)
throw new IllegalArgumentException(
"DNS SRV records priority must be a 16-bit unsiged integer (i.e. between 0-65535. Priority was: "
+ priority);
this.priority = priority;
this.weight = weight;
}
public int getPriority() {
return priority;
}
public int getWeight() {
return weight;
}
public int compareTo(SRVRecord other) {
// According to RFC2782,
// "[a] client MUST attempt to contact the target host with the lowest-numbered priority it can reach".
// This means that a SRV record with a higher priority is 'less' then one with a lower.
int res = other.priority - this.priority;
if (res == 0) {
res = this.weight - other.weight;
}
return res;
}
public String toString() {
return super.toString() + " prio:" + priority + ":w:" + weight;
}
}