dnsserver.java

java mail,java mailjava mailjava mailjava mail

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package org.apache.james.dnsserver;

import org.apache.avalon.framework.activity.Initializable;
import org.apache.avalon.framework.activity.Disposable;
import org.apache.avalon.framework.configuration.Configurable;
import org.apache.avalon.framework.configuration.Configuration;
import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.xbill.DNS.CNAMERecord;
import org.xbill.DNS.Cache;
import org.xbill.DNS.Credibility;
import org.xbill.DNS.DClass;
import org.xbill.DNS.ExtendedResolver;
import org.xbill.DNS.Lookup;
import org.xbill.DNS.Message;
import org.xbill.DNS.MXRecord;
import org.xbill.DNS.Name;
import org.xbill.DNS.Rcode;
import org.xbill.DNS.Record;
import org.xbill.DNS.Resolver;
import org.xbill.DNS.RRset;
import org.xbill.DNS.ResolverConfig;
import org.xbill.DNS.SetResponse;
import org.xbill.DNS.TextParseException;
import org.xbill.DNS.Type;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Random;

/**
 * Provides DNS client functionality to services running
 * inside James
 */
public class DNSServer
    extends AbstractLogEnabled
    implements Configurable, Initializable, Disposable,
    org.apache.james.services.DNSServer, DNSServerMBean {

    /**
     * A resolver instance used to retrieve DNS records.  This
     * is a reference to a third party library object.
     */
    protected Resolver resolver;

    /**
     * A TTL cache of results received from the DNS server.  This
     * is a reference to a third party library object.
     */
    private Cache cache;

    /**
     * Maximum number of RR to cache.
     */

    private int maxCacheSize = 50000;

    /**
     * Whether the DNS response is required to be authoritative
     */
    private int dnsCredibility;

    /**
     * The DNS servers to be used by this service
     */
    private List dnsServers = new ArrayList();

    /**
     * The MX Comparator used in the MX sort.
     */
    private Comparator mxComparator = new MXRecordComparator();

    /**
     * @see org.apache.avalon.framework.configuration.Configurable#configure(Configuration)
     */
    public void configure( final Configuration configuration )
        throws ConfigurationException {

        final boolean autodiscover =
            configuration.getChild( "autodiscover" ).getValueAsBoolean( true );

        if (autodiscover) {
            getLogger().info("Autodiscovery is enabled - trying to discover your system's DNS Servers");
            String[] serversArray = ResolverConfig.getCurrentConfig().servers();
            if (serversArray != null) {
                for ( int i = 0; i < serversArray.length; i++ ) {
                    dnsServers.add(serversArray[ i ]);
                    getLogger().info("Adding autodiscovered server " + serversArray[i]);
                }
            }
        }

        // Get the DNS servers that this service will use for lookups
        final Configuration serversConfiguration = configuration.getChild( "servers" );
        final Configuration[] serverConfigurations =
            serversConfiguration.getChildren( "server" );

        for ( int i = 0; i < serverConfigurations.length; i++ ) {
            dnsServers.add( serverConfigurations[ i ].getValue() );
        }

        if (dnsServers.isEmpty()) {
            getLogger().info("No DNS servers have been specified or found by autodiscovery - adding 127.0.0.1");
            dnsServers.add("127.0.0.1");
        }

        final boolean authoritative =
            configuration.getChild( "authoritative" ).getValueAsBoolean( false );
        // TODO: Check to see if the credibility field is being used correctly.  From the
        //       docs I don't think so
        dnsCredibility = authoritative ? Credibility.AUTH_ANSWER : Credibility.NONAUTH_ANSWER;

        maxCacheSize = (int) configuration.getChild( "maxcachesize" ).getValueAsLong( maxCacheSize );
    }

    /**
     * @see org.apache.avalon.framework.activity.Initializable#initialize()
     */
    public void initialize()
        throws Exception {

        getLogger().debug("DNSServer init...");

        // If no DNS servers were configured, default to local host
        if (dnsServers.isEmpty()) {
            try {
                dnsServers.add( InetAddress.getLocalHost().getHostName() );
            } catch ( UnknownHostException ue ) {
                dnsServers.add( "127.0.0.1" );
            }
        }

        //Create the extended resolver...
        final String[] serversArray = (String[])dnsServers.toArray(new String[0]);

        if (getLogger().isInfoEnabled()) {
            for(int c = 0; c < serversArray.length; c++) {
                getLogger().info("DNS Server is: " + serversArray[c]);
            }
        }

        try {
            resolver = new ExtendedResolver( serversArray );
            Lookup.setDefaultResolver(resolver);
        } catch (UnknownHostException uhe) {
            getLogger().fatalError("DNS service could not be initialized.  The DNS servers specified are not recognized hosts.", uhe);
            throw uhe;
        }

        cache = new Cache (DClass.IN);
        cache.setMaxEntries(maxCacheSize);
        Lookup.setDefaultCache(cache, DClass.IN);
        
        getLogger().debug("DNSServer ...init end");
    }

    /**
     * <p>Return the list of DNS servers in use by this service</p>
     *
     * @return an array of DNS server names
     */
    public String[] getDNSServers() {
        return (String[])dnsServers.toArray(new String[0]);
    }

    
    /**
     * <p>Return a prioritized unmodifiable list of MX records
     * obtained from the server.</p>
     *
     * @param hostname domain name to look up
     *
     * @return a list of MX records corresponding to this mail domain
     */
    public List findMXRecordsRaw(String hostname) {
        Record answers[] = lookup(hostname, Type.MX);
        List servers = new ArrayList();
        if (answers == null) {
            return servers;
        }

        MXRecord mxAnswers[] = new MXRecord[answers.length];
        for (int i = 0; i < answers.length; i++) {
            mxAnswers[i] = (MXRecord)answers[i];
        }

        Arrays.sort(mxAnswers, mxComparator);

        for (int i = 0; i < mxAnswers.length; i++) {
            servers.add(mxAnswers[i].getTarget ().toString ());
            getLogger().debug(new StringBuffer("Found MX record ").append(mxAnswers[i].getTarget ().toString ()).toString());
        }
        return servers;
    }
    
    /**
     * <p>Return a prioritized unmodifiable list of host handling mail
     * for the domain.</p>
     * 
     * <p>First lookup MX hosts, then MX hosts of the CNAME adress, and
     * if no server is found return the IP of the hostname</p>
     *
     * @param hostname domain name to look up
     *
     * @return a unmodifiable list of handling servers corresponding to
     *         this mail domain name
     */
    public Collection findMXRecords(String hostname) {
        List servers = new ArrayList();
        try {
            servers = findMXRecordsRaw(hostname);
            return Collections.unmodifiableCollection(servers);
        } finally {
            //If we found no results, we'll add the original domain name if
            //it's a valid DNS entry
            if (servers.size () == 0) {
                StringBuffer logBuffer =
                    new StringBuffer(128)
                            .append("Couldn't resolve MX records for domain ")
                            .append(hostname)
                            .append(".");
                getLogger().info(logBuffer.toString());
                Record cnames[] = lookup(hostname, Type.CNAME);
                Collection cnameMXrecords = null;
                if (cnames!=null && cnames.length > 0) {
                    cnameMXrecords = findMXRecordsRaw(((CNAMERecord) cnames[0]).getTarget().toString());
                } else {
                    logBuffer = new StringBuffer(128)
                            .append("Couldn't find CNAME records for domain ")
                            .append(hostname)
                            .append(".");
                    getLogger().info(logBuffer.toString());
                }
                if (cnameMXrecords==null) {
                    try {
                        getByName(hostname);
                        servers.add(hostname);
                    } catch (UnknownHostException uhe) {
                        // The original domain name is not a valid host,
                        // so we can't add it to the server list.  In this
                        // case we return an empty list of servers
                        logBuffer = new StringBuffer(128)
                                  .append("Couldn't resolve IP address for host ")
                                  .append(hostname)