Package org.opennms.netmgt.poller.monitors.support

Class DNSAddressRequest

  • public class DNSAddressRequest
extends java.lang.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 , OpenNMS

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int CLASS_IN
      Defines the class internet in the domain name system.
      java.util.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.
      java.lang.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 Description
      DNSAddressRequest​(java.lang.String host)
      Constructs a DNSAddressRequest for the hostname passed.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      byte[] buildRequest()
      Builds the address request.
      static java.lang.String codeName​(int code)
      Returns the code string for the error code received.
      java.util.List<DNSAddressRR> getAnswers()
      Return an enumeration of the received answers.
      java.util.List<java.lang.Integer> getFatalResponseCodes()
      getFatalResponseCodes
      java.lang.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 setFatalResponseCodes​(java.util.List<java.lang.Integer> codes)
      setFatalResponseCodes
      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

      • 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.

        See Also:
        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 java.lang.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 java.util.List<DNSAddressRR> m_answers

        The list of answers.

    • Constructor Detail

      • DNSAddressRequest

        public DNSAddressRequest​(java.lang.String host)

        Constructs a DNSAddressRequest for the 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 java.io.IOException

        Builds the address request.

        Returns:
        A byte array containing the request.
        Throws:
        java.io.IOException - if any.

      • receiveResponse

        public void receiveResponse​(byte[] data,
                            int length)
                     throws java.io.IOException

        Extracts the response from the bytearray.

        Parameters:
        data - The byte array containing the response.
        length - The length of the byte array.
        Throws:
        java.io.IOException - Thrown if there is an error while reading the received packet
        java.io.IOException - if any.

      • verifyResponse

        public void verifyResponse​(byte[] data,
                           int length)
                    throws java.io.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:
        java.io.IOException - Thrown if there is an error while reading the received packet
        java.io.IOException - if any.

      • getAnswers

        public java.util.List<DNSAddressRR> getAnswers()

        Return an enumeration of the received answers.

        Returns:
        The list of received answers.

      • getRequestID

        public int getRequestID()

        The request id for this particular instance.

        Returns:
        a int.

      • getHost

        public java.lang.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 java.lang.String codeName​(int code)

        Returns the code string for the error code received.

        Parameters:
        code - The error code.
        Returns:
        The error string corresponding to the error code

      • getFatalResponseCodes

        public java.util.List<java.lang.Integer> getFatalResponseCodes()

        getFatalResponseCodes

        Returns:
        a List object.

      • setFatalResponseCodes

        public void setFatalResponseCodes​(java.util.List<java.lang.Integer> codes)

        setFatalResponseCodes

        Parameters:
        codes - a List object.