/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.whirr.util;
import java.io.IOException;
import java.net.InetSocketAddress;
import org.xbill.DNS.DClass;
import org.xbill.DNS.ExtendedResolver;
import org.xbill.DNS.Message;
import org.xbill.DNS.Name;
import org.xbill.DNS.Record;
import org.xbill.DNS.Resolver;
import org.xbill.DNS.ReverseMap;
import org.xbill.DNS.Section;
import org.xbill.DNS.Type;
/**
* Utility functions for DNS.
*/
public class DnsUtil {
/**
* resolve the reverse dns name for the given IP address
*
* @param hostIp
* @return The resolved DNS name.
* @throws IOException
*/
public static String resolveAddress(String hostIp) throws IOException {
Resolver res = new ExtendedResolver();
res.setTimeout(5); // seconds
Name name = ReverseMap.fromAddress(hostIp);
int type = Type.PTR;
int dclass = DClass.IN;
Record rec = Record.newRecord(name, type, dclass);
Message query = Message.newQuery(rec);
Message response = res.send(query);
Record[] answers = response.getSectionArray(Section.ANSWER);
if (answers.length == 0) {
// Fall back to standard Java: in contrast to dnsjava, this also reads /etc/hosts
return new InetSocketAddress(hostIp, 0).getAddress().getCanonicalHostName();
} else {
String revaddr = answers[0].rdataToString();
return revaddr.endsWith(".") ? revaddr.substring(0, revaddr.length() - 1) : revaddr;
}
}
}