762 lines
23 KiB
Ruby
762 lines
23 KiB
Ruby
#---
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# $Id: Header.rb,v 1.5 2006/07/30 16:54:28 bluemonk Exp $
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#+++
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require 'net/dns/dns'
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module Net # :nodoc:
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module DNS
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#
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# =Name
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#
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# Net::DNS::Header - DNS packet header class
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#
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# =Synopsis
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#
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# require 'net/dns/header'
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#
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# =Description
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#
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# The Net::DNS::Header class represents the header portion of a
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# DNS packet. An Header object is created whenever a new packet
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# is parsed or as user request.
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#
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# header = Net::DNS::Header.new
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# # ;; id = 18123
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# # ;; qr = 0 opCode: 0 aa = 0 tc = 0 rd = 1
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# # ;; ra = 0 ad = 0 cd = 0 rcode = 0
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# # ;; qdCount = 1 anCount = 0 nsCount = 0 arCount = 0
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#
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# header.format
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 18123 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # |0| 0 |0|0|1|0|0| 0 | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 1 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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#
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# # packet is an instance of Net::DNS::Packet
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# header = packet.header
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# puts "Answer is #{header.auth? ? '' : 'non'} authoritative"
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#
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# A lot of methods were written to keep a compatibility layer with
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# the Perl version of the library, as long as methods name which are
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# more or less the same.
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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::Header 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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# * HeaderArgumentError: canonical argument error
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# * HeaderWrongCount: a wrong +count+ parameter has been passed
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# * HeaderWrongRecursive: a wrong +recursive+ parameter has been passed
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# * HeaderWrongOpcode: a not valid +opCode+ has been specified
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# * HeaderDuplicateID: the requested ID is already in use
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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 Header
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#
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# =Name
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#
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# Net::DNS::Header::RCode - DNS Header RCode handling class
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#
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# =Synopsis
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#
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# It should be used internally by Net::DNS::Header class. However, it's still
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# possible to instantiate it directly.
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#
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# require 'net/dns/header'
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# rcode = Net::DNS::Header::RCode.new 0
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#
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# =Description
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#
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# The RCode class represents the RCode field in the Header portion of a
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# DNS packet. This field (called Response Code) is used to get informations
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# about the status of a DNS operation, such as a query or an update. These
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# are the values in the original Mockapetris's standard (RFC1035):
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#
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# * 0 No error condition
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# * 1 Format error - The name server was unable to interpret
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# the query.
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# * 2 Server failure - The name server was
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# unable to process this query due to a
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# problem with the name server.
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# * 3 Name Error - Meaningful only for
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# responses from an authoritative name
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# server, this code signifies that the
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# domain name referenced in the query does
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# not exist.
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# * 4 Not Implemented - The name server does
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# not support the requested kind of query.
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# * 5 Refused - The name server refuses to
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# perform the specified operation for
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# policy reasons. For example, a name
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# server may not wish to provide the
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# information to the particular requester,
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# or a name server may not wish to perform
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# a particular operation (e.g., zone
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# transfer) for particular data.
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# * 6-15 Reserved for future use.
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#
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# In the next DNS RFCs, codes 6-15 has been assigned to the following
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# errors:
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#
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# * 6 YXDomain
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# * 7 YXRRSet
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# * 8 NXRRSet
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# * 9 NotAuth
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# * 10 NotZone
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#
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# More RCodes has to come for TSIGs and other operations.
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#
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class RCode
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# Constant for +rcode+ Response Code No Error
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NOERROR = 0
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# Constant for +rcode+ Response Code Format Error
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FORMAT = 1
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# Constant for +rcode+ Response Code Server Format Error
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SERVER = 2
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# Constant for +rcode+ Response Code Name Error
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NAME = 3
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# Constant for +rcode+ Response Code Not Implemented Error
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NOTIMPLEMENTED = 4
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# Constant for +rcode+ Response Code Refused Error
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REFUSED = 5
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RCodeType = %w[NoError FormErr ServFail NXDomain NotImp
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Refused YXDomain YXRRSet NXRRSet NotAuth NotZone]
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RCodeErrorString = ["No errors",
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"The name server was unable to interpret the query",
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"The name server was unable to process this query due to problem with the name server",
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"Domain name referenced in the query does not exists",
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"The name server does not support the requested kind of query",
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"The name server refuses to perform the specified operation for policy reasons",
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"",
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"",
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"",
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"",
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""]
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attr_reader :code, :type, :explanation
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def initialize(code)
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if (0..10).include? code
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@code = code
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@type = RCodeType[code]
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@explanation = RCodeErrorString[code]
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else
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raise HeaderArgumentError, "RCode #{code} out of range"
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end
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end
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def to_s
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@code.to_s
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end
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end
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# Constant for +opCode+ query
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QUERY = 0
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# Constant for +opCode+ iquery
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IQUERY = 1
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# Constant for +opCode+ status
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STATUS = 2
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# Array with given strings
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OPARR = %w[QUERY IQUERY STATUS]
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@@id_arr = []
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# Reader for +id+ attribute
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attr_reader :id
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# Reader for the operational code
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attr_reader :opCode
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# Reader for the rCode instance
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attr_reader :rCode
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# Reader for question section entries number
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attr_reader :qdCount
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# Reader for answer section entries number
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attr_reader :anCount
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# Reader for authority section entries number
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attr_reader :nsCount
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# Reader for addictional section entries number
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attr_reader :arCount
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# Creates a new Net::DNS::Header object with the desired values,
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# which can be specified as an Hash argument. When called without
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# arguments, defaults are used. If a data string is passed, values
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# are taken from parsing the string.
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#
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# Examples:
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#
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# # Create a new Net::DNS::Header object
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# header = Net::DNS::Header.new
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#
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# # Create a new Net::DNS::Header object passing values
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# header = Net::DNS::Header.new(:opCode => 1, :rd => 0)
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#
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# # Create a new Net::DNS::Header object with binary data
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# header = Net::DNS::Header.new(data)
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#
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# Default values are:
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#
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# :id => auto generated
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# :qr => 0 # Query response flag
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# :aa => 0 # Authoritative answer flag
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# :tc => 0 # Truncated packet flag
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# :ra => 0 # Recursiond available flag
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# :rCode => 0 # Response code (status of the query)
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# :opCode => 0 # Operational code (purpose of the query)
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# :cd => 0 # Checking disable flag
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# :ad => 0 # Only relevant in DNSSEC context
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# :rd => 1 # Recursion desired flag
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# :qdCount => 1 # Number of questions in the dns packet
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# :anCount => 0 # Number of answer RRs in the dns packet
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# :nsCount => 0 # Number of authoritative RRs in the dns packet
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# :arCount => 0 # Number of additional RRs in the dns packet
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#
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# See also each option for a detailed explanation of usage.
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#
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def initialize(arg = {})
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if arg.kind_of? Hash
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new_from_hash(arg)
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else
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raise HeaderArgumentError, "Wrong argument class: #{arg.class}"
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end
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end
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# Creates a new Net::DNS::Header object from binary data, which is
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# passed as a string object as argument.
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# The configurations parameters are taken from parsing the string.
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#
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# Example:
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#
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# # Create a new Net::DNS::Header object with binary data
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# header = Net::DNS::Header.new(data)
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#
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# header.auth?
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# #=> "true" if it comes from authoritative name server
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#
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def self.parse(arg)
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if arg.kind_of? String
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o = allocate
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o.send(:new_from_binary, arg)
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o
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else
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raise HeaderArgumentError, "Wrong argument class: #{arg.class}"
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end
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end
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# Inspect method, prints out all the options and relative values.
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#
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# p Net::DNS::Header.new
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# # ;; id = 18123
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# # ;; qr = 0 opCode: 0 aa = 0 tc = 0 rd = 1
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# # ;; ra = 0 ad = 0 cd = 0 rcode = 0
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# # ;; qdCount = 1 anCount = 0 nsCount = 0 arCount = 0
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#
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# This method will maybe be changed in the future to a more pretty
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# way of display output.
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#
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def inspect
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";; id = #@id\n" +
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if false # @opCode == "UPDATE"
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#do stuff
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else
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";; qr = #@qr\t" +
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"opCode: #{opCode_str}\t" +
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"aa = #@aa\t" +
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"tc = #@tc\t" +
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"rd = #@rd\n" +
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";; ra = #@ra\t" +
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"ad = #@ad\t" +
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"cd = #@cd\t" +
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"rcode = #{@rCode.type}\n" +
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";; qdCount = #@qdCount\t"+
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"anCount = #@anCount\t"+
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"nsCount = #@nsCount\t"+
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"arCount = #@arCount\n"
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end
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end
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# The Net::DNS::Header#format method prints out the header
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# in a special ascii representation of data, in a way
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# similar to those often found on RFCs.
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#
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# p Net::DNS::Header.new.format
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 18123 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # |0| 0 |0|0|1|0|0| 0 | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 1 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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# # | 0 |
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# # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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#
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# This can be very usefull for didactical purpouses :)
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#
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def format
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del = ("+-" * 16) + "+\n"
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len = del.length
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str = del + "|" + @id.to_s.center(len-3) + "|\n"
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str << del + "|" + @qr.to_s
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str << "|" + @opCode.to_s.center(7)
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str << "|" + @aa.to_s
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str << "|" + @tc.to_s
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str << "|" + @rd.to_s
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str << "|" + @ra.to_s
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str << "|" + @ad.to_s
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str << "|" + @cd.to_s.center(3)
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str << "|" + @rCode.to_s.center(7) + "|\n"
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str << del + "|" + @qdCount.to_s.center(len-3) + "|\n"
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str << del + "|" + @anCount.to_s.center(len-3) + "|\n"
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str << del + "|" + @nsCount.to_s.center(len-3) + "|\n"
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str << del + "|" + @arCount.to_s.center(len-3) + "|\n" + del
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str
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end
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# Returns the header data in binary format, appropriate
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# for use in a DNS query packet.
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#
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# hdata = header.data
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# puts "Header is #{hdata.size} bytes"
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#
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def data
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arr = []
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arr.push(@id)
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arr.push((@qr<<7)|(@opCode<<3)|(@aa<<2)|(@tc<<1)|@rd)
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arr.push((@ra<<7)|(@ad<<5)|(@cd<<4)|@rCode.code)
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arr.push(@qdCount)
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arr.push(@anCount)
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arr.push(@nsCount)
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arr.push(@arCount)
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arr.pack("n C2 n4")
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end
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# Set the ID for the current header. Useful when
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# performing security tests.
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#
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def id=(val)
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if @@id_arr.include? val
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raise HeaderDuplicateID, "ID #{val} already used"
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end
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if (1..65535).include? val
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@id = val
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@@id_arr.push val
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else
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raise HeaderArgumentError, "ID #{val} out of range"
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end
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end
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# Checks whether the header is a query (+qr+ bit set to 0)
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#
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def query?
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@qr == 0
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end
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# Set the +qr+ query response flag to be either +true+ or
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# +false+. You can also use the values 0 and 1. This flag
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# indicates if the DNS packet contains a query or an answer,
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# so it should be set to +true+ in DNS answer packets.
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# If +qr+ is +true+, the packet is a response.
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#
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def qr=(val)
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case val
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when true
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@qr = 1
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when false
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@qr = 0
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when 0,1
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@qr = val
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else
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raise HeaderArgumentError, ":qr must be true(or 1) or false(or 0)"
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end
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end
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# Checks whether the header is a response
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# (+qr+ bit set to 1)
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#
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def response?
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@qr == 1
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end
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# Returns a string representation of the +opCode+
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#
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# puts "Packet is a #{header.opCode_str}"
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# #=> Packet is a QUERY
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#
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def opCode_str
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OPARR[@opCode]
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end
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# Set the +opCode+ variable to a new value. This fields indicates
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# the type of the question present in the DNS packet; +val+ can be
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# one of the values QUERY, IQUERY or STATUS.
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#
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# * QUERY is the standard DNS query
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# * IQUERY is the inverse query
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# * STATUS is used to query the nameserver for its status
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#
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# Example:
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#
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# include Net::DNS
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# header = Header.new
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# header.opCode = Header::STATUS
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#
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def opCode=(val)
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if (0..2).include? val
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@opCode = val
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else
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raise HeaderWrongOpcode, "Wrong opCode value (#{val}), must be QUERY, IQUERY or STATUS"
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end
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end
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# Checks whether the response is authoritative
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#
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# if header.auth?
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# puts "Response is authoritative"
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# else
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# puts "Answer is NOT authoritative"
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# end
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#
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def auth?
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@aa == 1
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end
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# Set the +aa+ flag (authoritative answer) to either +true+
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# or +false+. You can also use 0 or 1.
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#
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# This flag indicates whether a DNS answer packet contains
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# authoritative data, meaning that is was generated by a
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# nameserver authoritative for the domain of the question.
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#
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# Must only be set to +true+ in DNS answer packets.
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#
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def aa=(val)
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case val
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when true
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@aa = 1
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when false
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@aa = 0
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when 0,1
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@aa = val
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else
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raise HeaderArgumentError, ":aa must be true(or 1) or false(or 0)"
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end
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end
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# Checks whether the packet was truncated
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#
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# # Sending packet using UDP
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# if header.truncated?
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# puts "Warning, packet has been truncated!"
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# # Sending packet using TCP
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# end
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# # Do something with the answer
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#
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def truncated?
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@tc == 1
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end
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# Set the +tc+ flag (truncated packet) to either +true+
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# ot +false+. You can also use 0 or 1.
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#
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# The truncated flag is used in response packets to indicate
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# that the amount of data to be trasmitted exceedes the
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# maximum allowed by the protocol in use, tipically UDP, and
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# that the data present in the packet has been truncated.
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# A different protocol (such has TCP) need to be used to
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# retrieve full data.
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#
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# Must only be set in DNS answer packets.
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#
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def tc=(val)
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case val
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when true
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@tc = 1
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when false
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@tc = 0
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when 0,1
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@tc = val
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else
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raise HeaderArgumentError, ":tc must be true(or 1) or false(or 0)"
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end
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end
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# Checks whether the packet has a recursion bit
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# set, meaning that recursion is desired
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#
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def recursive?
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@rd == 1
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end
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# Sets the recursion desidered bit.
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# Remember that recursion query support is
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# optional.
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#
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# header.recursive = true
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# hdata = header.data # suitable for sending
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#
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# Consult RFC1034 and RFC1035 for a detailed explanation
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# of how recursion works.
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#
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def recursive=(val)
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case val
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when true
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@rd = 1
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when false
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@rd = 0
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when 1
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@rd = 1
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when 0
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@rd = 0
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else
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raise HeaderWrongRecursive, "Wrong value (#{val}), please specify true (1) or false (0)"
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end
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|
end
|
|
|
|
# Alias for Header#recursive= to keep compatibility
|
|
# with the Perl version.
|
|
#
|
|
def rd=(val)
|
|
self.recursive = val
|
|
end
|
|
|
|
# Checks whether recursion is available.
|
|
# This flag is usually set by nameservers to indicate
|
|
# that they support recursive-type queries.
|
|
#
|
|
def r_available?
|
|
@ra == 1
|
|
end
|
|
|
|
# Set the +ra+ flag (recursion available) to either +true+ or
|
|
# +false+. You can also use 0 and 1.
|
|
#
|
|
# This flag must only be set in DNS answer packets.
|
|
#
|
|
def ra=(val)
|
|
case val
|
|
when true
|
|
@ra = 1
|
|
when false
|
|
@ra = 0
|
|
when 0,1
|
|
@ra = val
|
|
else
|
|
raise HeaderArgumentError, ":ra must be true(or 1) or false(or 0)"
|
|
end
|
|
end
|
|
|
|
# Checks whether checking is enabled or disabled.
|
|
#
|
|
# Checking is enabled by default.
|
|
#
|
|
def checking?
|
|
@cd == 0
|
|
end
|
|
|
|
# Set the +cd+ flag (checking disabled) to either +true+
|
|
# ot +false+. You can also use 0 or 1.
|
|
#
|
|
def cd=(val)
|
|
case val
|
|
when true
|
|
@cd = 1
|
|
when false
|
|
@cd = 0
|
|
when 0,1
|
|
@cd = val
|
|
else
|
|
raise HeaderArgumentError, ":cd must be true(or 1) or false(or 0)"
|
|
end
|
|
end
|
|
|
|
# Checks whether +ad+ flag has been set.
|
|
#
|
|
# This flag is only relevant in DNSSEC context.
|
|
#
|
|
def verified?
|
|
@ad == 1
|
|
end
|
|
|
|
# Set the +ad+ flag to either +true+
|
|
# ot +false+. You can also use 0 or 1.
|
|
#
|
|
# The AD bit is only set on answers where signatures have
|
|
# been cryptographically verified or the server is
|
|
# authoritative for the data and is allowed to set the bit by policy.
|
|
#
|
|
def ad=(val)
|
|
case val
|
|
when true
|
|
@ad = 1
|
|
when false
|
|
@ad = 0
|
|
when 0,1
|
|
@ad = val
|
|
else
|
|
raise HeaderArgumentError, ":ad must be true(or 1) or false(or 0)"
|
|
end
|
|
end
|
|
|
|
# Returns an error array for the header response code, or
|
|
# +nil+ if no error is generated.
|
|
#
|
|
# error, cause = header.rCode_str
|
|
# puts "Error #{error} cause by: #{cause}" if error
|
|
# #=> Error ForErr caused by: The name server
|
|
# #=> was unable to interpret the query
|
|
#
|
|
def rCode_str
|
|
return rCode.type, rCode.explanation
|
|
end
|
|
|
|
# Checks for errors in the DNS packet
|
|
#
|
|
# unless header.error?
|
|
# puts "No errors in DNS answer packet"
|
|
# end
|
|
#
|
|
def error?
|
|
@rCode.code > 0
|
|
end
|
|
|
|
# Set the rCode value. This should only be done in DNS
|
|
# answer packets.
|
|
#
|
|
def rCode=(val)
|
|
@rCode = RCode.new(val)
|
|
end
|
|
|
|
# Sets the number of entries in a question section
|
|
#
|
|
def qdCount=(val)
|
|
if (0..65535).include? val
|
|
@qdCount = val
|
|
else
|
|
raise HeaderWrongCount, "Wrong number of count (#{val}), must be 0-65535"
|
|
end
|
|
end
|
|
|
|
# Sets the number of RRs in an answer section
|
|
#
|
|
def anCount=(val)
|
|
if (0..65535).include? val
|
|
@anCount = val
|
|
else
|
|
raise HeaderWrongCount, "Wrong number of count (#{val}), must be 0-65535"
|
|
end
|
|
end
|
|
|
|
# Sets the number of RRs in an authority section
|
|
#
|
|
def nsCount=(val)
|
|
if (0..65535).include? val
|
|
@nsCount = val
|
|
else
|
|
raise HeaderWrongCount, "Wrong number of count (#{val}), must be 0-65535"
|
|
end
|
|
end
|
|
|
|
# Sets the number of RRs in an addictional section
|
|
#
|
|
def arCount=(val)
|
|
if (0..65535).include? val
|
|
@arCount = val
|
|
else
|
|
raise HeaderWrongCount, "Wrong number of count (#{val}), must be 0-65535"
|
|
end
|
|
end
|
|
|
|
private
|
|
|
|
def new_from_scratch
|
|
@id = genID # generate ad unique id
|
|
@qr = @aa = @tc = @ra = @ad = @cd = 0
|
|
@rCode = RCode.new(0) # no error
|
|
@anCount = @nsCount = @arCount = 0
|
|
@rd = @qdCount = 1
|
|
@opCode = QUERY # standard query, default message
|
|
end
|
|
|
|
def new_from_binary(str)
|
|
unless str.size == Net::DNS::HFIXEDSZ
|
|
raise HeaderArgumentError, "Header binary data has wrong size: #{str.size} bytes"
|
|
end
|
|
arr = str.unpack("n C2 n4")
|
|
@id = arr[0]
|
|
@qr = (arr[1] >> 7) & 0x01
|
|
@opCode = (arr[1] >> 3) & 0x0F
|
|
@aa = (arr[1] >> 2) & 0x01
|
|
@tc = (arr[1] >> 1) & 0x01
|
|
@rd = arr[1] & 0x1
|
|
@ra = (arr[2] >> 7) & 0x01
|
|
@ad = (arr[2] >> 5) & 0x01
|
|
@cd = (arr[2] >> 4) & 0x01
|
|
@rCode = RCode.new(arr[2] & 0xf)
|
|
@qdCount = arr[3]
|
|
@anCount = arr[4]
|
|
@nsCount = arr[5]
|
|
@arCount = arr[6]
|
|
end
|
|
|
|
def new_from_hash(hash)
|
|
new_from_scratch
|
|
hash.each do |key,val|
|
|
eval "self.#{key.to_s} = val"
|
|
end
|
|
end
|
|
|
|
def genID
|
|
while (@@id_arr.include?(q = rand(65535)))
|
|
end
|
|
@@id_arr.push(q)
|
|
q
|
|
end
|
|
|
|
end # class Header
|
|
|
|
end # class DNS
|
|
end # module Net
|
|
|
|
|
|
class HeaderArgumentError < ArgumentError # :nodoc: all
|
|
end
|
|
|
|
class HeaderWrongCount < ArgumentError # :nodoc: all
|
|
end
|
|
|
|
class HeaderWrongRecursive < ArgumentError # :nodoc: all
|
|
end
|
|
|
|
class HeaderWrongOpcode < ArgumentError # :nodoc: all
|
|
end
|
|
|
|
class HeaderDuplicateID < ArgumentError # :nodoc: all
|
|
end
|