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|
module Net
module DNS
#
# =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.
#
class Question
include Names
# Base error class.
class Error < StandardError
end
# An error in the +name+ part of a Question entry
class NameInvalid < Error
end
# +name+ part of a Question entry
attr_reader :qName
# +type+ part of a Question entry
attr_reader :qType
# +class+ part of a Question entry
attr_reader :qClass
# Creates a new Net::DNS::Question object:
#
# question = Net::DNS::Question.new("example.com")
# #=> "example.com A IN"
# question = Net::DNS::Question.new("example.com", Net::DNS::MX)
# #=> "example.com MX IN"
# question = Net::DNS::Question.new("example.com", Net::DNS::TXT, Net::DNS::HS)
# #=> "example.com TXT HS"
# If not specified, +type+ and +cls+ arguments defaults
# to Net::DNS::A and Net::DNS::IN respectively.
#
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
# 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
#
def self.parse(arg)
o = allocate
o.send(:new_from_binary, arg.to_s)
o
end
# Outputs binary data from a Question object
#
# question.data
# #=> "\006google\003com\000\000\001\000\001"
#
def data
[pack_name(@qName), @qType.to_i, @qClass.to_i].pack("a*nn")
end
# 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.
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
#
# call-seq:
# question.inspect -> string
#
# Returns a printable version of question with nice formatting.
#
# q = Net::DNS::Question.new("google.com.", Net::DNS::A)
# q.inspect # => "google.com. IN A "
#
def inspect
len = if @qName.size > 29
@qName.size + 1
else
29
end
[@qName, @qClass.to_s, @qType.to_s].pack("A#{len} A8 A8")
end
#
# call-seq:
# question.to_s -> string
#
# Returns a string representation of question.
# It is the same as <tt>inspect</tt>.
#
# q = Net::DNS::Question.new("google.com.", Net::DNS::A)
# q.inspect # => "google.com. IN A "
#
def to_s
inspect.to_s
end
private
def build_qName(str)
result = ""
offset = 0
loop do
len = str.unpack("@#{offset} C")[0]
break if len == 0
offset += 1
result += str[offset..offset + len - 1]
result += "."
offset += len
end
result
end
def check_name(input)
name = input.to_s.strip
if name =~ /[^\w\.\-_]/
raise NameInvalid, "Invalid Question Name `#{name}'"
end
name
end
def new_from_binary(data)
str, type, cls = data.unpack("a#{data.size - 4}nn")
@qName = build_qName(str)
@qType = Net::DNS::RR::Types.new type
@qClass = Net::DNS::RR::Classes.new cls
rescue StandardError => e
raise ArgumentError, "Invalid data: #{data.inspect}"
end
end
end
end
|
