Package org.apache.hadoop.net

Class DNS

java.lang.Object

org.apache.hadoop.net.DNS

@LimitedPrivate({"HDFS","MapReduce"})
@Unstable
public class DNS
extends java.lang.Object

A class that provides direct and reverse lookup functionalities, allowing the querying of specific network interfaces or nameservers.

Constructor Summary

Constructors

Constructor	Description
DNS()

Method Summary

Modifier and Type	Method	Description
static java.lang.String	getDefaultHost(java.lang.String strInterface)	Returns the default (first) host name associated by the default nameserver with the address bound to the specified network interface
static java.lang.String	getDefaultHost(java.lang.String strInterface, java.lang.String nameserver)
static java.lang.String	getDefaultHost(java.lang.String strInterface, java.lang.String nameserver, boolean tryfallbackResolution)	Returns the default (first) host name associated by the provided nameserver with the address bound to the specified network interface
static java.lang.String	getDefaultIP(java.lang.String strInterface)	Returns the first available IP address associated with the provided network interface or the local host IP if "default" is given.
static java.lang.String[]	getHosts(java.lang.String strInterface)	Returns all the host names associated by the default nameserver with the address bound to the specified network interface
static java.lang.String[]	getHosts(java.lang.String strInterface, java.lang.String nameserver, boolean tryfallbackResolution)	Returns all the host names associated by the provided nameserver with the address bound to the specified network interface
static java.lang.String[]	getIPs(java.lang.String strInterface)
static java.lang.String[]	getIPs(java.lang.String strInterface, boolean returnSubinterfaces)	Returns all the IPs associated with the provided interface, if any, in textual form.
static java.util.List<java.net.InetAddress>	getIPsAsInetAddressList(java.lang.String strInterface, boolean returnSubinterfaces)	Returns all the IPs associated with the provided interface, if any, as a list of InetAddress objects.
static java.lang.String	reverseDns(java.net.InetAddress hostIp, java.lang.String ns)	Returns the hostname associated with the specified IP address by the provided nameserver.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DNS

public DNS()

Method Detail

reverseDns

public static java.lang.String reverseDns(java.net.InetAddress hostIp,
                                          @Nullable
                                          java.lang.String ns)
                                   throws javax.naming.NamingException

Returns the hostname associated with the specified IP address by the provided nameserver. Loopback addresses

Parameters:

hostIp - The address to reverse lookup

ns - The host name of a reachable DNS server

Returns:

The host name associated with the provided IP

Throws:

javax.naming.NamingException - If a NamingException is encountered

getIPs

public static java.lang.String[] getIPs(java.lang.String strInterface)
                                 throws java.net.UnknownHostException

Parameters:

strInterface - input strInterface.

Returns:

Like getIPs(String, boolean), but returns all IPs associated with the given interface and its subinterfaces.

Throws:

java.net.UnknownHostException - If no IP address for the local host could be found.

getIPs

public static java.lang.String[] getIPs(java.lang.String strInterface,
                                        boolean returnSubinterfaces)
                                 throws java.net.UnknownHostException

Returns all the IPs associated with the provided interface, if any, in textual form.

Parameters:

strInterface - The name of the network interface or sub-interface to query (eg eth0 or eth0:0) or the string "default"

returnSubinterfaces - Whether to return IPs associated with subinterfaces of the given interface

Returns:

A string vector of all the IPs associated with the provided interface. The local host IP is returned if the interface name "default" is specified or there is an I/O error looking for the given interface.

Throws:

java.net.UnknownHostException - If the given interface is invalid

getDefaultIP

public static java.lang.String getDefaultIP(java.lang.String strInterface)
                                     throws java.net.UnknownHostException

Returns the first available IP address associated with the provided network interface or the local host IP if "default" is given.

Parameters:

strInterface - The name of the network interface or subinterface to query (e.g. eth0 or eth0:0) or the string "default"

Returns:

The IP address in text form, the local host IP is returned if the interface name "default" is specified

Throws:

java.net.UnknownHostException - If the given interface is invalid

getHosts

public static java.lang.String[] getHosts(java.lang.String strInterface,
                                          @Nullable
                                          java.lang.String nameserver,
                                          boolean tryfallbackResolution)
                                   throws java.net.UnknownHostException

Returns all the host names associated by the provided nameserver with the address bound to the specified network interface

Parameters:

strInterface - The name of the network interface or subinterface to query (e.g. eth0 or eth0:0)

nameserver - The DNS host name

tryfallbackResolution - if true and if reverse DNS resolution fails then attempt to resolve the hostname with InetAddress.getCanonicalHostName() which includes hosts file resolution.

Returns:

A string vector of all host names associated with the IPs tied to the specified interface

Throws:

java.net.UnknownHostException - if the given interface is invalid

getHosts

public static java.lang.String[] getHosts(java.lang.String strInterface)
                                   throws java.net.UnknownHostException

Returns all the host names associated by the default nameserver with the address bound to the specified network interface

Parameters:

strInterface - The name of the network interface to query (e.g. eth0)

Returns:

The list of host names associated with IPs bound to the network interface

Throws:

java.net.UnknownHostException - If one is encountered while querying the default interface

getDefaultHost

public static java.lang.String getDefaultHost(@Nullable
                                              java.lang.String strInterface,
                                              @Nullable
                                              java.lang.String nameserver,
                                              boolean tryfallbackResolution)
                                       throws java.net.UnknownHostException

Returns the default (first) host name associated by the provided nameserver with the address bound to the specified network interface

Parameters:

strInterface - The name of the network interface to query (e.g. eth0)

nameserver - The DNS host name

tryfallbackResolution - Input tryfallbackResolution.

Returns:

The default host names associated with IPs bound to the network interface

Throws:

java.net.UnknownHostException - If one is encountered while querying the default interface

getDefaultHost

public static java.lang.String getDefaultHost(@Nullable
                                              java.lang.String strInterface)
                                       throws java.net.UnknownHostException

Returns the default (first) host name associated by the default nameserver with the address bound to the specified network interface

Parameters:

strInterface - The name of the network interface to query (e.g. eth0). Must not be null.

Returns:

The default host name associated with IPs bound to the network interface

Throws:

java.net.UnknownHostException - If one is encountered while querying the default interface

getDefaultHost

public static java.lang.String getDefaultHost(@Nullable
                                              java.lang.String strInterface,
                                              @Nullable
                                              java.lang.String nameserver)
                                       throws java.net.UnknownHostException

Parameters:

strInterface - The name of the network interface to query (e.g. eth0)

nameserver - The DNS host name

Returns:

Returns the default (first) host name associated by the provided nameserver with the address bound to the specified network interface.

Throws:

java.net.UnknownHostException - If one is encountered while querying the default interface

getIPsAsInetAddressList

public static java.util.List<java.net.InetAddress> getIPsAsInetAddressList(java.lang.String strInterface,
                                                                           boolean returnSubinterfaces)
                                                                    throws java.net.UnknownHostException

Returns all the IPs associated with the provided interface, if any, as a list of InetAddress objects.

Parameters:

strInterface - The name of the network interface or sub-interface to query (eg eth0 or eth0:0) or the string "default"

returnSubinterfaces - Whether to return IPs associated with subinterfaces of the given interface

Returns:

A list of all the IPs associated with the provided interface. The local host IP is returned if the interface name "default" is specified or there is an I/O error looking for the given interface.

Throws:

java.net.UnknownHostException - If the given interface is invalid