/**
* 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.hadoop.net;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Enumeration;
import java.util.Vector;
import javax.naming.NamingException;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
/**
*
* A class that provides direct and reverse lookup functionalities, allowing
* the querying of specific network interfaces or nameservers.
*
*
*/
public class DNS {
/**
* Returns the hostname associated with the specified IP address by the
* provided nameserver.
*
* @param hostIp
* The address to reverse lookup
* @param ns
* The host name of a reachable DNS server
* @return The host name associated with the provided IP
* @throws NamingException
* If a NamingException is encountered
*/
public static String reverseDns(InetAddress hostIp, String ns)
throws NamingException {
//
// Builds the reverse IP lookup form
// This is formed by reversing the IP numbers and appending in-addr.arpa
//
String[] parts = hostIp.getHostAddress().split("\\.");
String reverseIP = parts[3] + "." + parts[2] + "." + parts[1] + "."
+ parts[0] + ".in-addr.arpa";
DirContext ictx = new InitialDirContext();
Attributes attribute =
ictx.getAttributes("dns://" // Use "dns:///" if the default
+ ((ns == null) ? "" : ns) +
// nameserver is to be used
"/" + reverseIP, new String[] { "PTR" });
ictx.close();
return attribute.get("PTR").get().toString();
}
/**
* Returns all the IPs associated with the provided interface, if any, in
* textual form.
*
* @param strInterface
* The name of the network interface to query (e.g. eth0)
* @return A string vector of all the IPs associated with the provided
* interface
* @throws UnknownHostException
* If an UnknownHostException is encountered in querying the
* default interface
*
*/
public static String[] getIPs(String strInterface)
throws UnknownHostException {
try {
NetworkInterface netIF = NetworkInterface.getByName(strInterface);
if (netIF == null)
return new String[] { InetAddress.getLocalHost()
.getHostAddress() };
else {
Vector<String> ips = new Vector<String>();
Enumeration e = netIF.getInetAddresses();
while (e.hasMoreElements())
ips.add(((InetAddress) e.nextElement()).getHostAddress());
return ips.toArray(new String[] {});
}
} catch (SocketException e) {
return new String[] { InetAddress.getLocalHost().getHostAddress() };
}
}
/**
* Returns the first available IP address associated with the provided
* network interface
*
* @param strInterface
* The name of the network interface to query (e.g. eth0)
* @return The IP address in text form
* @throws UnknownHostException
* If one is encountered in querying the default interface
*/
public static String getDefaultIP(String strInterface)
throws UnknownHostException {
String[] ips = getIPs(strInterface);
return ips[0];
}
/**
* Returns all the host names associated by the provided nameserver with the
* address bound to the specified network interface
*
* @param strInterface
* The name of the network interface to query (e.g. eth0)
* @param nameserver
* The DNS host name
* @return A string vector of all host names associated with the IPs tied to
* the specified interface
* @throws UnknownHostException
*/
public static String[] getHosts(String strInterface, String nameserver)
throws UnknownHostException {
String[] ips = getIPs(strInterface);
Vector<String> hosts = new Vector<String>();
for (int ctr = 0; ctr < ips.length; ctr++)
try {
hosts.add(reverseDns(InetAddress.getByName(ips[ctr]),
nameserver));
} catch (Exception e) {
}
if (hosts.size() == 0)
return new String[] { InetAddress.getLocalHost().getCanonicalHostName() };
else
return hosts.toArray(new String[] {});
}
/**
* Returns all the host names associated by the default nameserver with the
* address bound to the specified network interface
*
* @param strInterface
* The name of the network interface to query (e.g. eth0)
* @return The list of host names associated with IPs bound to the network
* interface
* @throws UnknownHostException
* If one is encountered while querying the deault interface
*
*/
public static String[] getHosts(String strInterface)
throws UnknownHostException {
return getHosts(strInterface, null);
}
/**
* Returns the default (first) host name associated by the provided
* nameserver with the address bound to the specified network interface
*
* @param strInterface
* The name of the network interface to query (e.g. eth0)
* @param nameserver
* The DNS host name
* @return The default host names associated with IPs bound to the network
* interface
* @throws UnknownHostException
* If one is encountered while querying the deault interface
*/
public static String getDefaultHost(String strInterface, String nameserver)
throws UnknownHostException {
if (strInterface.equals("default"))
return InetAddress.getLocalHost().getCanonicalHostName();
if (nameserver != null && nameserver.equals("default"))
return getDefaultHost(strInterface);
String[] hosts = getHosts(strInterface, nameserver);
return hosts[0];
}
/**
* Returns the default (first) host name associated by the default
* nameserver with the address bound to the specified network interface
*
* @param strInterface
* The name of the network interface to query (e.g. eth0)
* @return The default host name associated with IPs bound to the network
* interface
* @throws UnknownHostException
* If one is encountered while querying the deault interface
*/
public static String getDefaultHost(String strInterface)
throws UnknownHostException {
return getDefaultHost(strInterface, null);
}
}