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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* 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.
*
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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;
}
}