dnsproxylookup.java

Java SIP

/*
 * Copyright (c) 2001 The MITRE Corporation <[e-mail]>
 *
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Library General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 *
 */

/**
 * Class to provide a means to lookup DNS SRV records
 *
 */

package org.mitre.jsip.proxy;

import java.util.*;
import javax.naming.*;
import javax.naming.directory.*;
import org.mitre.jsip.*;

public class DNSProxyLookup implements ProxyLookup {

    private String domainName;
    private String dnsServer = "linus.mitre.org";

    private Hashtable uriCache = new Hashtable();

    DNSProxyLookup( String domainName, String dnsServer ) {
	this.domainName = domainName;
	this.dnsServer = dnsServer;
    }

    public SipUri getProxyUri( ) throws SipProxyException {

	if ( uriCache.contains( domainName ) ) {
	    return (SipUri) uriCache.get( domainName );
	}

	Hashtable env = new Hashtable();
	env.put( "java.naming.factory.initial", "com.sun.jndi.dns.DnsFactoryContext" );
	env.put( "java.naming.provider.url", "dns://" + dnsServer + "/" + domainName );

	String proxyName = null;
	try {
	    DirContext ictx = new InitialDirContext( env );
	    
	    String sipName = "_sip." + domainName;
	    Attributes attr = ictx.getAttributes( sipName, new String [] { "SRV" } ); 
	
	    //	String proxyName = attr.get( "A" ); // ??????? should be a hostname
	    proxyName = "stars.mitre.org";
	} catch ( NamingException ne ) {
	    throw new SipProxyException( ne.toString() );
	}

	SipUri returnUri = new SipUri( "sip:" + proxyName );
	uriCache.put( domainName, returnUri );

	return returnUri;
    }

    public SipUri getConnectionUri( String host ) throws SipProxyException {
	// check the cache first to see if we've already done this lookup
	if ( uriCache.contains( host ) ) {
	    return (SipUri) uriCache.get( host );
	}

	// now check DNS. If this host has an SOA record, treat it as a domain.
	// if not, treat it as a host 
	Attributes attrs = null;
	DirContext ictx = null;
	try {
	    ictx = getDirContext( host );
	    attrs = ictx.getAttributes( "", new String [] {"SOA"} );
	} catch ( NamingException nex ) {
	    throw new SipProxyException( nex.toString() );
	}

	String sipHost = null;
	if ( attrs.size() > 0 ) {
	    // this appears to be a domain. Try to contact its SIP proxy
	    String sipName = "_sip";
	    try {
		Attributes attr = ictx.getAttributes( sipName, new String[]{ "SRV" } ); 
		
		if ( attr.size() == 0 ) { // no proxy server found
		    throw new SipProxyException( "No SIP proxy found in DNS tables" );
		}
		
		Attribute at = attr.get( "SRV" );
		sipHost = (String) at.get();
	    } catch ( NamingException ne ) {
		throw new SipProxyException( ne.toString() );
	    }
	} else {
	    // believe this is a host. Pass uri back as such
	    sipHost = host;
	}

	SipUri returnUri = new SipUri( sipHost );
	uriCache.put( host, returnUri );

	return returnUri;
    }
	
    protected void testDNSLookup(String hostname) throws NamingException 
    {
	this.domainName = domainName;

	Hashtable env = new Hashtable();
	env.put( "java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory" );
	env.put( "java.naming.provider.url", "dns://" + dnsServer + "/" + domainName );

	DirContext ictx = new InitialDirContext( env );
	
	Attributes attr = ictx.getAttributes( hostname, new String [] {"SOA"} );
	//	Attributes attr = ictx.getAttributes( hostname );

	NamingEnumeration ne = attr.getAll();
	
	for ( ; ne.hasMore(); ) {
	    Attribute at = (Attribute)ne.next();
	    System.out.print( "Found attribute: " + at.getID() + " with value of " );
	    String atVal = (String)at.get();
	    System.out.println( atVal );
	}
    }

    private DirContext getDirContext( String dname ) throws NamingException {

	Hashtable env = new Hashtable();
	env.put( "java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory" );
	env.put( "java.naming.provider.url", "dns://" + dnsServer + "/" + dname );

	return new InitialDirContext( env );
    }

    public static void main( String [] argc ) {

	DNSProxyLookup dpl = new DNSProxyLookup( argc[0], "linus.mitre.org" );

	// just test
	try {
	    dpl.testDNSLookup( argc[1] );
	} catch ( NamingException nex ) {
	    System.err.println( "Got a problem: " + nex );
	}

	System.exit(0);
    }
}