DNSUtil.java 4.16 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124
/**
 * $RCSfile: DNSUtil.java,v $
 * $Revision: 2867 $
 * $Date: 2005-09-22 03:40:04 -0300 (Thu, 22 Sep 2005) $
 *
 * Copyright (C) 2004-2005 Jive Software. All rights reserved.
 *
 * This software is published under the terms of the GNU Public License (GPL),
 * a copy of which is included in this distribution.
 */

package org.jivesoftware.wildfire.net;

import org.jivesoftware.util.Log;

import javax.naming.directory.Attributes;
import javax.naming.directory.InitialDirContext;
import javax.naming.directory.DirContext;
import java.util.Hashtable;

/**
 * Utilty class to perform DNS lookups for XMPP services.
 *
 * @author Matt Tucker
 */
public class DNSUtil {

    private static DirContext context;

    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) {
            Log.error(e);
        }
    }

    /**
     * Returns the host name and port that 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 specified default port.<p>
     *
     * As an example, a lookup for "example.com" may return "im.example.com:5269".
     *
     * @param domain the domain.
     * @param defaultPort default port to return if the DNS look up fails.
     * @return a 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, int defaultPort) {
        if (context == null) {
            return new HostAddress(domain, defaultPort);
        }
        String host = domain;
        int port = defaultPort;
        try {
            Attributes dnsLookup = context.getAttributes("_xmpp-server._tcp." + domain);
            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 e) {
            // Attempt lookup with older "jabber" name.
            try {
                Attributes dnsLookup = context.getAttributes("_jabber._tcp." + domain);
                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) { }
        }
        // Host entries in DNS should end with a ".".
        if (host.endsWith(".")) {
            host = host.substring(0, host.length()-1);
        }
        return new HostAddress(host, port);
    }

    /**
     * Encapsulates a hostname and port.
     */
    public static class HostAddress {

        private String host;
        private int port;

        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;
        }
    }
}