org.opennms.netmgt.provision.support.dns

Class DNSAddressRequest

java.lang.Object

org.opennms.netmgt.provision.support.dns.DNSAddressRequest

public class DNSAddressRequest
extends Object

 The DNSAddressRequest holds a DNS request to lookup the IP address of a host -
 provides for transmitting and receiving the response for this lookup.

 NOTES: A DNS request and response has the following fileds header questions
 answers authorities additional information

 The header has the following format: id - unique id sent by the client and
 returned by the server in its response 16 bits of flags -
 Query(0)/response(1) flag opcode - that has type of query AA - set if the
 response is an authoritative answer TC - set if response is truncated RD -
 set if recursion is desired RA - set if recursion is available Z - reserved
 bits RCODE - response code

 This class checks only for the received response to have the answer(which
 will hold the IP address) - ignores the authorities and additional info

 

Author:

Sowmya

Field Summary

Fields

Modifier and Type	Field and Description
static int	CLASS_IN Defines the class internet in the domain name system.
List<DNSAddressRR>	m_answers The list of answers.
boolean	m_authoritative True if the answer is authoratitve.
boolean	m_recursive True if the message is recursive.
String	m_reqHost The host to request information from.
int	m_reqID The id used to seralize the request.
boolean	m_truncated True if the message is truncated.
static int	OPCODE_QUERY The op code for a query in the header.
static int	SHIFT_AUTHORITATIVE The offset of the authoritative bit in the header.
static int	SHIFT_OPCODE The offset of the opcode bits in the header.
static int	SHIFT_QUERY The offset of the query bit in the header.
static int	SHIFT_RECURSE_AVAILABLE The offset of the requrse avail bit in the header.
static int	SHIFT_RECURSE_PLEASE The offset of the recurse req bit in the header.
static int	SHIFT_RESERVED The offset of the reserved bits in the header.
static int	SHIFT_RESPONSE_CODE The offset of the response code bits in the header.
static int	SHIFT_TRUNCATED The offset of the truncated bit in the header.
static int	TYPE_ADDR Defines the address type.

Constructor Summary

Constructors

Constructor and Description
DNSAddressRequest(String host) Constructs a DNSAddressRequest for ths hostname passed.

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	buildRequest() Builds the address request.
static String	codeName(int code) Returns the code string for the error code recieved.
List<DNSAddressRR>	getAnswers() Return an enumeration of the recieved answers.
String	getHost() The hostname that will be request from the DNS box.
int	getRequestID() The request id for this particular instance.
boolean	isAuthoritative() Returns true if the answer is authoritative.
boolean	isRecursive() Returns true if the answer is recursive.
boolean	isTruncated() Returns true if the answer is truncated.
void	receiveResponse(byte[] data, int length) Extracts the response from the bytearray.
void	verifyResponse(byte[] data, int length) This method only goes so far as to decode the flags in the response byte array to verify that a DNS server sent the response.

Methods inherited from class java.lang.Object

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

Field Detail

CLASS_IN

public static final int CLASS_IN

Defines the class internet in the domain name system.

See Also:

Constant Field Values

TYPE_ADDR

public static final int TYPE_ADDR

Defines the address type.

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Constant Field Values

SHIFT_QUERY

public static final int SHIFT_QUERY

The offset of the query bit in the header.

See Also:

Constant Field Values

SHIFT_OPCODE

public static final int SHIFT_OPCODE

The offset of the opcode bits in the header.

See Also:

Constant Field Values

SHIFT_AUTHORITATIVE

public static final int SHIFT_AUTHORITATIVE

The offset of the authoritative bit in the header.

See Also:

Constant Field Values

SHIFT_TRUNCATED

public static final int SHIFT_TRUNCATED

The offset of the truncated bit in the header.

See Also:

Constant Field Values

SHIFT_RECURSE_PLEASE

public static final int SHIFT_RECURSE_PLEASE

The offset of the recurse req bit in the header.

See Also:

Constant Field Values

SHIFT_RECURSE_AVAILABLE

public static final int SHIFT_RECURSE_AVAILABLE

The offset of the requrse avail bit in the header.

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Constant Field Values

SHIFT_RESERVED

public static final int SHIFT_RESERVED

The offset of the reserved bits in the header.

See Also:

Constant Field Values

SHIFT_RESPONSE_CODE

public static final int SHIFT_RESPONSE_CODE

The offset of the response code bits in the header.

See Also:

Constant Field Values

OPCODE_QUERY

public static final int OPCODE_QUERY

The op code for a query in the header.

See Also:

Constant Field Values

m_reqHost

public String m_reqHost

The host to request information from. This would be the nameserver if it supports DNS.

m_reqID

public int m_reqID

The id used to seralize the request. This allows the client (us) and the server (host) to match exchanges.

m_authoritative

public boolean m_authoritative

True if the answer is authoratitve.

m_truncated

public boolean m_truncated

True if the message is truncated.

m_recursive

public boolean m_recursive

True if the message is recursive.

m_answers

public List<DNSAddressRR> m_answers

The list of answers.

Constructor Detail

DNSAddressRequest

public DNSAddressRequest(String host)

Constructs a DNSAddressRequest for ths hostname passed. The host string that is passed to the address string should be a hostname in "x.y.z" where x, y, and z are strings. This is not suppose to be a dotted decimal address.

Parameters:

host - hostname for which address is to be constructed

Method Detail

buildRequest

public byte[] buildRequest()
                    throws IOException

Builds the address request.

Returns:

A byte array containing the request.

Throws:

IOException - if any.

receiveResponse

public void receiveResponse(byte[] data,
                   int length)
                     throws IOException

Extracts the response from the bytearray.

Parameters:

data - The byte array containing the response.

length - The length of the byte array.

Throws:

IOException - Thrown if there is an error while reading the recieved packet

IOException - if any.

verifyResponse

public void verifyResponse(byte[] data,
                  int length)
                    throws IOException

This method only goes so far as to decode the flags in the response byte array to verify that a DNS server sent the response.

NOTE: This is really a hack to get around the fact that the receiveResponse() method is not robust enough to handle all possible DNS server responses.

Parameters:

data - The byte array containing the response.

length - The length of the byte array.

Throws:

IOException - Thrown if there is an error while reading the recieved packet

IOException - if any.

getAnswers

public List<DNSAddressRR> getAnswers()

Return an enumeration of the recieved answers.

Returns:

The list of received answers.

getRequestID

public int getRequestID()

The request id for this particular instance.

Returns:

a int.

getHost

public String getHost()

The hostname that will be request from the DNS box.

Returns:

a String object.

isTruncated

public boolean isTruncated()

Returns true if the answer is truncated.

Returns:

a boolean.

isRecursive

public boolean isRecursive()

Returns true if the answer is recursive.

Returns:

a boolean.

isAuthoritative

public boolean isAuthoritative()

Returns true if the answer is authoritative.

Returns:

a boolean.

codeName

public static String codeName(int code)

Returns the code string for the error code recieved.

Parameters:

code - The error code.

Returns:

The error string corresponding to the error code