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	/*
	* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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 General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package com.sun.jndi.dns;


	import javax.naming.*;


	/**
	* The Resolver class performs DNS client operations in support of DnsContext.
	*
	* <p> Every DnsName instance passed to or returned from a method of
	* this class should be fully-qualified and contain a root label (an
	* empty component at position 0).
	*
	* @author Scott Seligman
	*/

	class Resolver {

	private DnsClient dnsClient;
	private int timeout; // initial timeout on UDP queries in ms
	private int retries; // number of UDP retries


	/*
	* Constructs a new Resolver given its servers and timeout parameters.
	* Each server is of the form "server[:port]".
	* IPv6 literal host names include delimiting brackets.
	* There must be at least one server.
	* "timeout" is the initial timeout interval (in ms) for UDP queries,
	* and "retries" gives the number of retries per server.
	*/
	Resolver(String[] servers, int timeout, int retries)
	throws NamingException {
	this.timeout = timeout;
	this.retries = retries;
	dnsClient = new DnsClient(servers, timeout, retries);
	}

	public void close() {
	dnsClient.close();
	dnsClient = null;
	}


	/*
	* Queries resource records of a particular class and type for a
	* given domain name.
	* Useful values of rrclass are ResourceRecord.[Q]CLASS_xxx.
	* Useful values of rrtype are ResourceRecord.[Q]TYPE_xxx.
	* If recursion is true, recursion is requested on the query.
	* If auth is true, only authoritative responses are accepted.
	*/
	ResourceRecords query(DnsName fqdn, int rrclass, int rrtype,
	boolean recursion, boolean auth)
	throws NamingException {
	return dnsClient.query(fqdn, rrclass, rrtype, recursion, auth);
	}

	/*
	* Queries all resource records of a zone given its domain name and class.
	* If recursion is true, recursion is requested on the query to find
	* the name server (and also on the zone transfer, but it won't matter).
	*/
	ResourceRecords queryZone(DnsName zone, int rrclass, boolean recursion)
	throws NamingException {

	DnsClient cl =
	new DnsClient(findNameServers(zone, recursion), timeout, retries);
	try {
	return cl.queryZone(zone, rrclass, recursion);
	} finally {
	cl.close();
	}
	}

	/*
	* Finds the zone of a given domain name. The method is to look
	* for the first SOA record on the path from the given domain to
	* the root. This search may be partially bypassed if the zone's
	* SOA record is received in the authority section of a response.
	* If recursion is true, recursion is requested on any queries.
	*/
	DnsName findZoneName(DnsName fqdn, int rrclass, boolean recursion)
	throws NamingException {

	fqdn = (DnsName) fqdn.clone();
	while (fqdn.size() > 1) { // while below root
	ResourceRecords rrs = null;
	try {
	rrs = query(fqdn, rrclass, ResourceRecord.TYPE_SOA,
	recursion, false);
	} catch (NameNotFoundException e) {
	throw e;
	} catch (NamingException e) {
	// Ignore error and keep searching up the tree.
	}
	if (rrs != null) {
	if (rrs.answer.size() > 0) { // found zone's SOA
	return fqdn;
	}
	// Look for an SOA record giving the zone's top node.
	for (int i = 0; i < rrs.authority.size(); i++) {
	ResourceRecord rr = rrs.authority.elementAt(i);
	if (rr.getType() == ResourceRecord.TYPE_SOA) {
	DnsName zone = rr.getName();
	if (fqdn.endsWith(zone)) {
	return zone;
	}
	}
	}
	}
	fqdn.remove(fqdn.size() - 1); // one step rootward
	}
	return fqdn; // no SOA found below root, so
	// return root
	}

	/*
	* Finds a zone's SOA record. Returns null if no SOA is found (in
	* which case "zone" is not actually a zone).
	* If recursion is true, recursion is requested on the query.
	*/
	ResourceRecord findSoa(DnsName zone, int rrclass, boolean recursion)
	throws NamingException {

	ResourceRecords rrs = query(zone, rrclass, ResourceRecord.TYPE_SOA,
	recursion, false);
	for (int i = 0; i < rrs.answer.size(); i++) {
	ResourceRecord rr = rrs.answer.elementAt(i);
	if (rr.getType() == ResourceRecord.TYPE_SOA) {
	return rr;
	}
	}
	return null;
	}

	/*
	* Finds the name servers of a zone. <tt>zone</tt> is a fully-qualified
	* domain name at the top of a zone.
	* If recursion is true, recursion is requested on the query.
	*/
	private String[] findNameServers(DnsName zone, boolean recursion)
	throws NamingException {

	// %%% As an optimization, could look in authority section of
	// findZoneName() response first.
	ResourceRecords rrs =
	query(zone, ResourceRecord.CLASS_INTERNET, ResourceRecord.TYPE_NS,
	recursion, false);
	String[] ns = new String[rrs.answer.size()];
	for (int i = 0; i < ns.length; i++) {
	ResourceRecord rr = rrs.answer.elementAt(i);
	if (rr.getType() != ResourceRecord.TYPE_NS) {
	throw new CommunicationException("Corrupted DNS message");
	}
	ns[i] = (String) rr.getRdata();

	// Server name will be passed to InetAddress.getByName(), which
	// may not be able to handle a trailing dot.
	// assert ns[i].endsWith(".");
	ns[i] = ns[i].substring(0, ns[i].length() - 1);
	}
	return ns;
	}
	}

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