Class: Net::DNS::Question

Inherits:
Object
  • Object
show all
Includes:
Names
Defined in:
lib/net/dns/question.rb

Overview

Name

Net::DNS::Question - DNS packet question class

Synopsis

require 'net/dns/question'

Description

This class represent the Question portion of a DNS packet. The number of question entries is stored in the qdCount variable of an Header object.

A new object can be created passing the name of the query and the type of answer desired, plus an optional argument containing the class:

question = Net::DNS::Question.new("google.com.", Net::DNS::A)
   #=> "google.com.                   A       IN"

Alternatevly, a new object is created when processing a binary packet, as when an answer is received. To obtain the binary data from a question object you can use the method Question#data:

question.data
   #=> "\006google\003com\000\000\001\000\001"

A lot of methods were written to keep a compatibility layer with the Perl version of the library, as long as methods name which are more or less the same.

Error classes

Some error classes has been defined for the Net::DNS::Header class, which are listed here to keep a light and browsable main documentation. We have:

  • QuestionArgumentError: generic argument error

  • QuestionNameError: an error in the name part of a Question entry

Copyright

Copyright © 2006 Marco Ceresa

All rights reserved. This program is free software; you may redistribute it and/or modify it under the same terms as Ruby itself.

Constant Summary

Constants included from Names

Names::INT16SZ

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Names

#dn_comp, #dn_expand, #names_array, #pack_name, #valid?

Constructor Details

#initialize(name, type = Net::DNS::A, cls = Net::DNS::IN) ⇒ Question

If not specified, type and cls arguments defaults to Net::DNS::A and Net::DNS::IN respectively.



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# File 'lib/net/dns/question.rb', line 85

def initialize(name,type=Net::DNS::A,cls=Net::DNS::IN)
  @qName = check_name name
  @qType = Net::DNS::RR::Types.new type
  @qClass = Net::DNS::RR::Classes.new cls
end

Instance Attribute Details

#qClass ⇒ Object (readonly)

class part of a Question entry



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# File 'lib/net/dns/question.rb', line 71

def qClass
  @qClass
end

#qName ⇒ Object (readonly)

name part of a Question entry



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# File 'lib/net/dns/question.rb', line 67

def qName
  @qName
end

#qType ⇒ Object (readonly)

type part of a Question entry



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# File 'lib/net/dns/question.rb', line 69

def qType
  @qType
end

Class Method Details

.parse(arg) ⇒ Object

Return a new Net::DNS::Question object created by parsing binary data, such as an answer from the nameserver.

question = Net::DNS::Question.parse(data)
puts "Queried for #{question.qName} type #{question.qType.to_s}"
  #=> Queried for example.com type A



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# File 'lib/net/dns/question.rb', line 99

def self.parse(arg)
  if arg.kind_of? String
    o = allocate
    o.send(:new_from_binary,arg)
    o
  else
    raise QuestionArgumentError, "Wrong argument format, must be a String"
  end
end

Instance Method Details

#comp_data ⇒ Object

Return the binary data of the objects, plus an offset and an Hash with references to compressed names. For use in Net::DNS::Packet compressed packet creation.



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# File 'lib/net/dns/question.rb', line 132

def comp_data
  arr = @qName.split(".")
  str = pack_name(@qName)
  string = ""
  names = {}
  offset = Net::DNS::HFIXEDSZ
  arr.size.times do |i|
    x = i+1
    elem = arr[-x]
    len = elem.size
    string = ((string.reverse)+([len,elem].pack("Ca*")).reverse).reverse
    names[string] = offset
    offset += len
  end
  offset += 2 * Net::DNS::INT16SZ
  str += "\000"
  [[str,@qType.to_i,@qClass.to_i].pack("a*nn"),offset,names]
end

#data ⇒ Object

Outputs binary data from a Question object

question.data
   #=> "\006google\003com\000\000\001\000\001"



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# File 'lib/net/dns/question.rb', line 124

def data
  [pack_name(@qName),@qType.to_i,@qClass.to_i].pack("a*nn")
end

#inspect ⇒ Object

Known inspect method with nice formatting



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# File 'lib/net/dns/question.rb', line 110

def inspect
  if @qName.size > 29 then 
    len = @qName.size + 1 
  else
    len = 29
  end
  [@qName,@qClass.to_s,@qType.to_s].pack("A#{len} A8 A8")
end