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# -*- coding: binary -*-
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require 'logger'
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require 'net/dns/names/names'
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require 'net/dns/dns'
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require 'net/dns/header'
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require 'net/dns/question'
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require 'net/dns/rr'
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module Net # :nodoc:
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  module DNS 
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    # =Name
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    #
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    # Net::DNS::Packet - DNS packet object class
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    #
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    # =Synopsis
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    # 
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    #   require 'net/dns/packet'
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    #
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    # =Description
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    # 
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    # The Net::DNS::Packet class represents an entire DNS packet,
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    # divided in his main section: 
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    # 
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    # * Header (instance of Net::DNS::Header)
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    # * Question (array of Net::DNS::Question objects)
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    # * Answer, Authority, Additional (each formed by an array of Net::DNS::RR 
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    #   objects)
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    #
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    # You can use this class whenever you need to create a DNS packet, whether
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    # in an user application, in a resolver instance (have a look, for instance,
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    # at the Net::DNS::Resolver#send method) or for a nameserver.
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    #
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    # Some example:
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    #
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    #   # Create a packet
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    #   packet = Net::DNS::Packet.new("www.example.com")
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    #   mx = Net::DNS::Packet.new("example.com", Net::DNS::MX)
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    #
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    #   # Getting packet binary data, suitable for network transmission
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    #   data = packet.data
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    #
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    # A packet object can be created from binary data too, like an 
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    # answer packet just received from a network stream:
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    #
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    #   packet = Net::DNS::Packet::parse(data)
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    #
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    # Each part of a packet can be gotten by the right accessors:
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    #
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    #   header = packet.header     # Instance of Net::DNS::Header class
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    #   question = packet.question # Instance of Net::DNS::Question class
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    #   
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    #   # Iterate over additional RRs
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    #   packet.additional.each do |rr|
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    #     puts "Got an #{rr.type} record"
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    #   end
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    #
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    # Some iterators have been written to easy the access of those RRs, 
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    # which are often the most important. So instead of doing:
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    #
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    #   packet.answer.each do |rr|
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    #     if rr.type == Net::DNS::RR::Types::A
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    #       # do something with +rr.address+
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    #     end
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    #   end
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    #
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    # we can do:
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    #
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    #   packet.each_address do |ip|
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    #     # do something with +ip+
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    #   end
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    #
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    # Be sure you don't miss all the iterators in the class documentation.
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    #
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    # =Logging facility
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    # 
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    # As Net::DNS::Resolver class, Net::DNS::Packet class has its own logging
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    # facility too. It work in the same way the other one do, so you can 
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    # maybe want to override it or change the file descriptor.
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    #
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    #   packet = Net::DNS::Packet.new("www.example.com")
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    #   packet.logger = $stderr
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    #
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    #   # or even
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    #   packet.logger = Logger.new("/tmp/packet.log")
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    #
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    # If the Net::DNS::Packet class is directly instantiated by the Net::DNS::Resolver
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    # class, like the great majority of the time, it will use the same logger facility.
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    #
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    # Logger level will be set to Logger::Debug if $DEBUG variable is set.
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    #
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    # =Error classes
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    #
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    # Some error classes has been defined for the Net::DNS::Packet class,
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    # which are listed here to keep a light and browsable main documentation.
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    # We have:
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    #
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    # * PacketArgumentError: Generic argument error for class Net::DNS::Packet
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    # * PacketError: Generic Packet error
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    #
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    # =Copyright
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    # 
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    # Copyright (c) 2006 Marco Ceresa
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    #
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    # All rights reserved. This program is free software; you may redistribute 
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    # it and/or modify it under the same terms as Ruby itself.
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    #
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    class Packet
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      include Names
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      attr_reader :header, :question, :answer, :authority, :additional
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      attr_reader :answerfrom, :answersize
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      # Create a new instance of Net::DNS::Packet class. Arguments are the
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      # canonical name of the resource, an optional type field and an optional
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      # class field. The record type and class can be omitted; they default 
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      # to +A+ and +IN+.
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      #
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      #   packet = Net::DNS::Packet.new("www.example.com")
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      #   packet = Net::DNS::Packet.new("example.com", Net::DNS::MX)
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      #   packet = Net::DNS::Packet.new("example.com",Net::DNS::TXT,Net::DNS::CH)
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      #
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      # This class no longer instantiate object from binary data coming from
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      # network streams. Please use Net::DNS::Packet.new_from_data instead.
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      # 
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      def initialize(name,type=Net::DNS::A,cls=Net::DNS::IN)
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        @header = Net::DNS::Header.new(:qdCount => 1)
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        @question = [Net::DNS::Question.new(name,type,cls)]
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        @answer = []
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        @authority = []
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        @additional = []
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        @logger = Logger.new $stdout
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        @logger.level = $DEBUG ? Logger::DEBUG : Logger::WARN
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      end
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      # Create a new instance of Net::DNS::Packet class from binary data, taken
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      # out by a network stream. For example:
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      #
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      #   # udp_socket is an UDPSocket waiting for a response
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      #   ans = udp_socket.recvfrom(1500)
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      #   packet = Net::DNS::Packet::parse(ans)
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      #
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      # An optional +from+ argument can be used to specify the information
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      # of the sender. If data is passed as is from a Socket#recvfrom call,
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      # the method will accept it.
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      #
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      # Be sure that your network data is clean from any UDP/TCP header, 
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      # especially when using RAW sockets.
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      # 
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      def Packet.parse(*args)
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        o = allocate
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        o.send(:new_from_data, *args)
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        o
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      end
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      # Checks if the packet is a QUERY packet
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      def query?
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        @header.opCode == Net::DNS::Header::QUERY
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      end
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      # Return the packet object in binary data, suitable
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      # for sending across a network stream.
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      #
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      #   packet_data = packet.data
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      #   puts "Packet is #{packet_data.size} bytes long"
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      #
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      def data
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        qdcount=ancount=nscount=arcount=0
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        data = @header.data
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        headerlength = data.length
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        @question.each do |question|
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          data += question.data
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          qdcount += 1
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        end
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        @answer.each do |rr|
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          data += rr.data#(data.length)
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          ancount += 1
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        end
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        @authority.each do |rr|
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          data += rr.data#(data.length)
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          nscount += 1
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        end
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        @additional.each do |rr|
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          next if rr.nil?
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          data += rr.data#(data.length)
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          arcount += 1
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        end
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        @header.qdCount = qdcount
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        @header.anCount = ancount
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        @header.nsCount = nscount
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        @header.arCount = arcount
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        @header.data + data[Net::DNS::HFIXEDSZ..data.size]
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      end
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      # Same as Net::DNS::Packet#data, but implements name compression
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      # (see RFC1025) for a considerable save of bytes.
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      #
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      #   packet = Net::DNS::Packet.new("www.example.com")
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      #   puts "Size normal is #{packet.data.size} bytes"
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      #   puts "Size compressed is #{packet.data_comp.size} bytes"
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      #   
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      def data_comp
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        offset = 0
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        compnames = {}
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        qdcount=ancount=nscount=arcount=0
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        data = @header.data
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        headerlength = data.length
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        @question.each do |question|
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          str,offset,names = question.data
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          data += str
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          compnames.update(names)
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          qdcount += 1
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        end
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        @answer.each do |rr|
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          str,offset,names = rr.data(offset,compnames)
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          data += str
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          compnames.update(names)
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          ancount += 1
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        end
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        @authority.each do |rr|
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          str,offset,names = rr.data(offset,compnames)
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          data += str
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          compnames.update(names)
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          nscount += 1
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        end
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        @additional.each do |rr|
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          str,offset,names = rr.data(offset,compnames)
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          data += str
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          compnames.update(names)
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          arcount += 1
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        end
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        @header.qdCount = qdcount
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        @header.anCount = ancount
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        @header.nsCount = nscount
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        @header.arCount = arcount
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        @header.data + data[Net::DNS::HFIXEDSZ..data.size]
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      end
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      # Inspect method
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      def inspect
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        retval = ""
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        if @answerfrom != "0.0.0.0:0" and @answerfrom
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          retval << ";; Answer received from #@answerfrom (#{@answersize} bytes)\n;;\n"
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        end
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        retval << ";; HEADER SECTION\n"
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        retval << @header.inspect
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        retval << "\n"
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        section = (@header.opCode == "UPDATE") ? "ZONE" : "QUESTION"
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        retval << ";; #{section} SECTION (#{@header.qdCount} record#{@header.qdCount == 1 ? '' : 's'}):\n"
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        @question.each do |qr|
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          retval << ";; " + qr.inspect + "\n"
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        end
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        unless @answer.size == 0
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          retval << "\n"
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          section = (@header.opCode == "UPDATE") ? "PREREQUISITE" : "ANSWER"
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          retval << ";; #{section} SECTION (#{@header.anCount} record#{@header.anCount == 1 ? '' : 's'}):\n"
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          @answer.each do |rr|
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            retval << rr.inspect + "\n"
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          end
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        end
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        unless @authority.size == 0
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          retval << "\n"
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          section = (@header.opCode == "UPDATE") ? "UPDATE" : "AUTHORITY"
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          retval << ";; #{section} SECTION (#{@header.nsCount} record#{@header.nsCount == 1 ? '' : 's'}):\n"
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          @authority.each do |rr|
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            retval << rr.inspect + "\n"
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          end
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        end
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        unless @additional.size == 0
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          retval << "\n"
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          retval << ";; ADDITIONAL SECTION (#{@header.arCount} record#{@header.arCount == 1 ? '' : 's'}):\n"
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          @additional.each do |rr|
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            retval << rr.inspect + "\n"
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          end
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        end
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        retval
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      end
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      # Wrapper to Header#truncated?
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      #
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      def truncated?
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        @header.truncated?
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      end
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      # Assign a Net::DNS::Header object to a Net::DNS::Packet 
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      # instance.
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      #
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      def header=(object)
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        if object.kind_of? Net::DNS::Header
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          @header = object
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        else
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          raise PacketArgumentError, "Argument must be a Net::DNS::Header object"
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        end
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      end
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      # Assign a Net::DNS::Question object, or an array of 
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      # Questions objects, to a Net::DNS::Packet instance.
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      #
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      def question=(object)
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        case object
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        when Array
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          if object.all? {|x| x.kind_of? Net::DNS::Question}
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            @question = object
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          else
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            raise PacketArgumentError, "Some of the elements is not an Net::DNS::Question object"
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          end
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        when Net::DNS::Question
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          @question = [object]
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        else
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          raise PacketArgumentError, "Invalid argument, not a Question object nor an array of objects"
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        end
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      end
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      # Assign a Net::DNS::RR object, or an array of 
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      # RR objects, to a Net::DNS::Packet instance answer 
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      # section.
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      #
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      def answer=(object)
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        case object
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        when Array
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          if object.all? {|x| x.kind_of? Net::DNS::RR}
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            @answer = object
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          else
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            raise PacketArgumentError, "Some of the elements is not an Net::DNS::RR object"
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          end
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        when Net::DNS::RR
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          @answer = [object]
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        else
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          raise PacketArgumentError, "Invalid argument, not a RR object nor an array of objects"
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        end
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      end
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      # Assign a Net::DNS::RR object, or an array of 
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      # RR objects, to a Net::DNS::Packet instance additional 
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      # section.
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      #
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      def additional=(object)
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        case object
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        when Array
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          if object.all? {|x| x.kind_of? Net::DNS::RR}
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            @additional = object
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          else
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            raise PacketArgumentError, "Some of the elements is not an Net::DNS::RR object"
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          end
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        when Net::DNS::RR
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          @additional = [object]
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        else
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          raise PacketArgumentError, "Invalid argument, not a RR object nor an array of objects"
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        end
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      end
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      # Assign a Net::DNS::RR object, or an array of 
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      # RR objects, to a Net::DNS::Packet instance authority 
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      # section.
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      #
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      def authority=(object)
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        case object
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        when Array
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          if object.all? {|x| x.kind_of? Net::DNS::RR}
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            @authority = object
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          else
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            raise PacketArgumentError, "Some of the elements is not an Net::DNS::RR object"
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          end
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        when Net::DNS::RR
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          @authority = [object]
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        else
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          raise PacketArgumentError, "Invalid argument, not a RR object nor an array of objects"
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        end
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      end
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      # Iterate for every address in the +answer+ section of a 
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      # Net::DNS::Packet object.
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      #
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      #   packet.each_address do |ip|
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      #     ping ip.to_s
394
      #   end
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      #
396
      # As you can see in the documentation for Net::DNS::RR::A class,
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      # the address returned is an instance of IPAddr class. 
398
      #
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      def each_address
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        @answer.each do |elem|
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          next unless elem.class == Net::DNS::RR::A
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          yield elem.address
403
        end
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      end
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406
      # Iterate for every nameserver in the +answer+ section of a 
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      # Net::DNS::Packet object.
408
      #
409
      #   packet.each_nameserver do |ns|
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      #     puts "Nameserver found: #{ns}"
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      #   end
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      #
413
      def each_nameserver
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        @answer.each do |elem|
415
          next unless elem.class == Net::DNS::RR::NS
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          yield elem.nsdname
417
        end
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      end
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      # Iterate for every exchange record in the +answer+ section 
421
      # of a Net::DNS::Packet object.
422
      #
423
      #   packet.each_mx do |pref,name|
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      #     puts "Mail exchange #{name} has preference #{pref}"
425
      #   end
426
      #
427
      def each_mx
428
        @answer.each do |elem|
429
          next unless elem.class == Net::DNS::RR::MX
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          yield elem.preference,elem.exchange
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        end
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      end
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434
      # Iterate for every canonical name in the +answer+ section 
435
      # of a Net::DNS::Packet object.
436
      #
437
      #   packet.each_cname do |cname|
438
      #     puts "Canonical name: #{cname}"
439
      #   end
440
      #
441
      def each_cname
442
        @answer.each do |elem|
443
          next unless elem.class == Net::DNS::RR::CNAME
444
          yield elem.cname
445
        end
446
      end
447
      
448
      # Iterate for every pointer in the +answer+ section of a 
449
      # Net::DNS::Packet object.
450
      #
451
      #   packet.each_ptr do |ptr|
452
      #     puts "Pointer for resource: #{ptr}"
453
      #   end
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      #
455
      def each_ptr
456
        @answer.each do |elem|
457
          next unless elem.class == Net::DNS::RR::PTR
458
          yield elem.ptrdname
459
        end
460
      end
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462
      # Chacks whether a query has returned a NXDOMAIN error,
463
      # meaning the domain name queried doesn't exists.
464
      #
465
      #   %w[a.com google.com ibm.com d.com].each do |domain|
466
      #     response = Net::DNS::Resolver.new.send(domain)
467
      #     puts "#{domain} doesn't exist" if response.nxdomain?
468
      #   end
469
      #     #=> a.com doesn't exist
470
      #     #=> d.com doesn't exist
471
      #
472
      def nxdomain?
473
        header.rCode == Net::DNS::Header::NAME
474
      end
475
      
476
      private
477

478
      # New packet from binary data
479
      def new_from_data(data, from = nil)
480
        unless from
481
          if data.kind_of? Array
482
            data,from = data
483
          else
484
            from = [0,0,"0.0.0.0","unknown"]
485
          end
486
        end
487
          
488
        @answerfrom = from[2] + ":" + from[1].to_s
489
        @answersize = data.size
490
        @logger = Logger.new $stdout
491
        @logger.level = $DEBUG ? Logger::DEBUG : Logger::WARN
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493
        #------------------------------------------------------------
494
        # Header section
495
        #------------------------------------------------------------
496
        offset = Net::DNS::HFIXEDSZ 
497
        @header = Net::DNS::Header.parse(data[0..offset-1])
498

499
        @logger.debug ";; HEADER SECTION"
500
        @logger.debug @header.inspect
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502
        #------------------------------------------------------------
503
        # Question section
504
        #------------------------------------------------------------
505
        section = @header.opCode == "UPDATE" ? "ZONE" : "QUESTION"
506
        @logger.debug ";; #{section} SECTION (#{@header.qdCount} record#{@header.qdCount == 1 ? '': 's'})"
507

508
        @question = []
509
        @header.qdCount.times do
510
          qobj,offset = parse_question(data,offset)
511
          @question << qobj
512
          @logger.debug ";; #{qobj.inspect}"
513
        end
514

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        #------------------------------------------------------------
516
        # Answer/prerequisite section
517
        #------------------------------------------------------------
518
        section = @header.opCode == "UPDATE" ? "PREREQUISITE" : "ANSWER"
519
        @logger.debug ";; #{section} SECTION (#{@header.qdCount} record#{@header.qdCount == 1 ? '': 's'})"
520
        
521
        @answer = []
522
        @header.anCount.times do
523
          if (rrobj, new_offset = Net::DNS::RR.parse_packet(data, offset))
524
            @answer << rrobj
525
            @logger.debug rrobj.inspect
526
            offset = new_offset
527
          else
528
            @logger.warn "Failed to parse RR packet from offset: #{offset}"
529
            _, offset = dn_expand(data, offset)
530
            _, _, _, rdlength = data.unpack("@#{offset} n2 N n")
531
            offset += RRFIXEDSZ + rdlength
532
          end
533
        end
534

535
        #------------------------------------------------------------
536
        # Authority/update section
537
        #------------------------------------------------------------
538
        section = @header.opCode == "UPDATE" ? "UPDATE" : "AUTHORITY"
539
        @logger.debug ";; #{section} SECTION (#{@header.nsCount} record#{@header.nsCount == 1 ? '': 's'})"
540
        
541
        @authority = []
542
        @header.nsCount.times do
543
          rrobj,offset = Net::DNS::RR.parse_packet(data,offset)
544
          @authority << rrobj
545
          @logger.debug rrobj.inspect          
546
        end
547
        
548
        #------------------------------------------------------------
549
        # Additional section
550
        #------------------------------------------------------------
551
        @logger.debug ";; ADDITIONAL SECTION (#{@header.arCount} record#{@header.arCount == 1 ? '': 's'})"    
552
        
553
        @additional = []
554
        @header.arCount.times do
555
          rrobj,offset = Net::DNS::RR.parse_packet(data,offset)
556
          @additional << rrobj
557
          @logger.debug rrobj.inspect
558
        end
559
        
560
      end # new_from_data
561
      
562
      
563
      # Parse question section
564
      def parse_question(data,offset)
565
        size = (dn_expand(data,offset)[1]-offset) + 2*Net::DNS::INT16SZ
566
        return [Net::DNS::Question.parse(data[offset,size]), offset+size]
567
      rescue StandardError => err
568
        raise PacketError, "Caught exception, maybe packet malformed => #{err}"
569
      end
570

571
    end # class Packet
572
    
573
  end # module DNS
574
end # module Net
575

576
class PacketError < StandardError # :nodoc:
577
end
578
class PacketArgumentError < ArgumentError # :nodoc:
579
end
580

581