DNSUtil.java
- /**
- *
- * Copyright 2003-2005 Jive Software, 2016-2018 Florian Schmaus.
- *
- * 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;
- import java.util.ArrayList;
- import java.util.Collections;
- import java.util.LinkedList;
- import java.util.List;
- import java.util.SortedMap;
- import java.util.TreeMap;
- import java.util.logging.Level;
- import java.util.logging.Logger;
- import org.jivesoftware.smack.ConnectionConfiguration.DnssecMode;
- import org.jivesoftware.smack.util.dns.DNSResolver;
- import org.jivesoftware.smack.util.dns.HostAddress;
- import org.jivesoftware.smack.util.dns.SRVRecord;
- import org.jivesoftware.smack.util.dns.SmackDaneProvider;
- import org.minidns.dnsname.DnsName;
- /**
- * Utility class to perform DNS lookups for XMPP services.
- *
- * @author Matt Tucker
- * @author Florian Schmaus
- */
- public class DNSUtil {
- public static final String XMPP_CLIENT_DNS_SRV_PREFIX = "_xmpp-client._tcp";
- public static final String XMPP_SERVER_DNS_SRV_PREFIX = "_xmpp-server._tcp";
- private static final Logger LOGGER = Logger.getLogger(DNSUtil.class.getName());
- private static DNSResolver dnsResolver = null;
- private static SmackDaneProvider daneProvider;
- /**
- * Set the DNS resolver that should be used to perform DNS lookups.
- *
- * @param resolver
- */
- public static void setDNSResolver(DNSResolver resolver) {
- dnsResolver = Objects.requireNonNull(resolver);
- }
- /**
- * Returns the current DNS resolved used to perform DNS lookups.
- *
- * @return the active DNSResolver
- */
- public static DNSResolver getDNSResolver() {
- return dnsResolver;
- }
- /**
- * Set the DANE provider that should be used when DANE is enabled.
- *
- * @param daneProvider
- */
- public static void setDaneProvider(SmackDaneProvider daneProvider) {
- DNSUtil.daneProvider = Objects.requireNonNull(daneProvider);
- }
- /**
- * Returns the currently active DANE provider used when DANE is enabled.
- *
- * @return the active DANE provider
- */
- public static SmackDaneProvider getDaneProvider() {
- return daneProvider;
- }
- @SuppressWarnings("ImmutableEnumChecker")
- enum DomainType {
- server(XMPP_SERVER_DNS_SRV_PREFIX),
- client(XMPP_CLIENT_DNS_SRV_PREFIX),
- ;
- public final DnsName srvPrefix;
- DomainType(String srvPrefixString) {
- srvPrefix = DnsName.from(srvPrefixString);
- }
- }
- /**
- * 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.
- * @param failedAddresses on optional list that will be populated with host addresses that failed to resolve.
- * @param dnssecMode DNSSec mode.
- * @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> resolveXMPPServiceDomain(DnsName domain, List<HostAddress> failedAddresses, DnssecMode dnssecMode) {
- return resolveDomain(domain, DomainType.client, failedAddresses, dnssecMode);
- }
- /**
- * 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.
- * @param failedAddresses on optional list that will be populated with host addresses that failed to resolve.
- * @param dnssecMode DNSSec mode.
- * @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(DnsName domain, List<HostAddress> failedAddresses, DnssecMode dnssecMode) {
- return resolveDomain(domain, DomainType.server, failedAddresses, dnssecMode);
- }
- /**
- *
- * @param domain the domain.
- * @param domainType the XMPP domain type, server or client.
- * @param failedAddresses a 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(DnsName domain, DomainType domainType,
- List<HostAddress> failedAddresses, DnssecMode dnssecMode) {
- if (dnsResolver == null) {
- throw new IllegalStateException("No DNS Resolver active in Smack");
- }
- List<HostAddress> addresses = new ArrayList<HostAddress>();
- // Step one: Do SRV lookups
- DnsName srvDomain = DnsName.from(domainType.srvPrefix, domain);
- List<SRVRecord> srvRecords = dnsResolver.lookupSRVRecords(srvDomain, failedAddresses, dnssecMode);
- if (srvRecords != null && !srvRecords.isEmpty()) {
- 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);
- } else {
- LOGGER.info("Could not resolve DNS SRV resource records for " + srvDomain + ". Consider adding those.");
- }
- int defaultPort = -1;
- switch (domainType) {
- case client:
- defaultPort = 5222;
- break;
- case server:
- defaultPort = 5269;
- break;
- }
- // Step two: Add the hostname to the end of the list
- HostAddress hostAddress = dnsResolver.lookupHostAddress(domain, defaultPort, failedAddresses, dnssecMode);
- if (hostAddress != null) {
- addresses.add(hostAddress);
- }
- return addresses;
- }
- /**
- * 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 the list of resolved HostAddresses
- */
- private 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().isRootLabel())
- return Collections.emptyList();
- // sorting the records improves the performance of the bisection later
- Collections.sort(records);
- // 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);
- }
- 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[bucketSize];
- int running_total = 0;
- int count = 0;
- int zeroWeight = 1;
- for (SRVRecord r : bucket) {
- if (r.getWeight() > 0) {
- zeroWeight = 0;
- break;
- }
- }
- 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;
- }
- }