Class: Dnsruby::Header

Inherits:
Object
  • Object
show all
Defined in:
lib/Dnsruby/message.rb

Overview

The header portion of a DNS packet

RFC 1035 Section 4.1.1

Constant Summary collapse

MAX_ID = 
65535

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*args) ⇒ Header

Returns a new instance of Header.



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# File 'lib/Dnsruby/message.rb', line 449

def initialize(*args)  
  if (args.length == 0)
    @id = rand(MAX_ID)
    @qr = false
    @opcode=OpCode.Query
    @aa = false
    @ad=false
    @tc = false
    @rd = false # recursion desired
    @ra = false # recursion available
    @cd=false
    @rcode=RCode.NoError
    @qdcount = 0
    @nscount = 0
    @ancount = 0
    @arcount = 0
  elsif (args.length == 1)
    decode(args[0])        
  end
end

Instance Attribute Details

#aa ⇒ Object

Authoritative answer flag



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# File 'lib/Dnsruby/message.rb', line 407

def aa
  @aa
end

#ad ⇒ Object

Relevant in DNSSEC context.

(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.)



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# File 'lib/Dnsruby/message.rb', line 423

def ad
  @ad
end

#ancount ⇒ Object Also known as: prcount

The number of records in the answer section of the message



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# File 'lib/Dnsruby/message.rb', line 445

def ancount
  @ancount
end

#arcount ⇒ Object Also known as: adcount

The number of records in the additional record section og the message



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# File 'lib/Dnsruby/message.rb', line 447

def arcount
  @arcount
end

#cd ⇒ Object

The checking disabled flag



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# File 'lib/Dnsruby/message.rb', line 416

def cd
  @cd
end

#dnssec_ok ⇒ Object

The DO (dnssec OK) flag



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# File 'lib/Dnsruby/message.rb', line 426

def dnssec_ok
  @dnssec_ok
end

#id ⇒ Object

The header ID



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# File 'lib/Dnsruby/message.rb', line 401

def id
  @id
end

#nscount ⇒ Object Also known as: upcount

The number of records in the authoriy section of the message



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# File 'lib/Dnsruby/message.rb', line 443

def nscount
  @nscount
end

#opcode ⇒ Object

The header opcode



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# File 'lib/Dnsruby/message.rb', line 438

def opcode
  @opcode
end

#qdcount ⇒ Object Also known as: zocount

The number of records in the question section of the message



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# File 'lib/Dnsruby/message.rb', line 441

def qdcount
  @qdcount
end

#qr ⇒ Object

The query response flag



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# File 'lib/Dnsruby/message.rb', line 404

def qr
  @qr
end

#ra ⇒ Object

Recursion available flag



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# File 'lib/Dnsruby/message.rb', line 432

def ra
  @ra
end

#rcode ⇒ Object

Query response code



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# File 'lib/Dnsruby/message.rb', line 435

def rcode
  @rcode
end

#rd ⇒ Object

Recursion Desired flag



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# File 'lib/Dnsruby/message.rb', line 413

def rd
  @rd
end

#tc ⇒ Object

Truncated flag



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# File 'lib/Dnsruby/message.rb', line 410

def tc
  @tc
end

Class Method Details

.decrement_arcount_encoded(bytes) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 509

def Header.decrement_arcount_encoded(bytes)
  header = Header.new
  header_end = 0
  MessageDecoder.new(bytes) {|msg|
    header.decode(msg)
    header_end = msg.index
  }
  header.arcount = header.arcount - 1
  bytes[0,header_end]=MessageEncoder.new {|msg|
    header.encode(msg)}.to_s
  return bytes
end

.new_from_data(data) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 478

def Header.new_from_data(data)
  header = Header.new
  MessageDecoder.new(data) {|msg|
    header.decode(msg)}
  return header
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 522

def ==(other)
  return @qr == other.qr &&
    @opcode == other.opcode &&
    @aa == other.aa &&
    @tc == other.tc &&
    @rd == other.rd &&
    @ra == other.ra &&
    @cd == other.cd &&
    @ad == other.ad &&
    @rcode == other.rcode
end

#data ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 485

def data
  return MessageEncoder.new {|msg|
    self.encode(msg)
  }.to_s
end

#decode(msg) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 567

def decode(msg)
  @id, flag, @qdcount, @ancount, @nscount, @arcount =
    msg.get_unpack('nnnnnn')
  @qr = (((flag >> 15)&1)==1)?true:false
  @opcode = OpCode.new((flag >> 11) & 15)
  @aa = (((flag >> 10)&1)==1)?true:false
  @tc = (((flag >> 9)&1)==1)?true:false
  @rd = (((flag >> 8)&1)==1)?true:false
  @ra = (((flag >> 7)&1)==1)?true:false
  @ad = (((flag >> 5)&1)==1)?true:false
  @cd = (((flag >> 4)&1)==1)?true:false
  @rcode = RCode.new(flag & 15)
end

#encode(msg) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 491

def encode(msg)
  msg.put_pack('nnnnnn',
    @id,
    (@qr?1:0) << 15 |
    (@opcode.code & 15) << 11 |
    (@aa?1:0) << 10 |
    (@tc?1:0) << 9 |
    (@rd?1:0) << 8 |
    (@ra?1:0) << 7 |
    (@ad?1:0) << 5 | 
    (@cd?1:0) << 4 |
    (@rcode.code & 15),
    @qdcount,
    @ancount,
    @nscount,
    @arcount)
end

#get_exception ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 581

def get_exception
  exception = nil
  if (@rcode==RCode.NXDOMAIN)
    exception = NXDomain.new
  elsif (@rcode==RCode.SERVFAIL)
    exception = ServFail.new
  elsif (@rcode==RCode.FORMERR)
    exception = FormErr.new
  elsif (@rcode==RCode.NOTIMP)
    exception = NotImp.new
  elsif (@rcode==RCode.REFUSED)
    exception = Refused.new
  end
  return exception
end

#to_s ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 534

def to_s
  retval = ";; id = #{@id}\n";
  
  if (@opcode == OpCode::Update)
    retval += ";; qr = #{@qr}    " +\
      "opcode = #{@opcode.string}    "+\
      "rcode = #{@rcode.string}\n";
    
    retval += ";; zocount = #{@qdcount}  "+\
      "prcount = #{@ancount}  " +\
      "upcount = #{@nscount}  "  +\
      "adcount = #{@arcount}\n";
  else
    retval += ";; qr = #{@qr}    "  +\
      "opcode = #{@opcode.string}    " +\
      "aa = #{@aa}    "  +\
      "tc = #{@tc}    " +\
      "rd = #{@rd}\n";
    
    retval += ";; ra = #{@ra}    " +\
      "ad = #{@ad}    "  +\
      "cd = #{@cd}    "  +\
      "rcode  = #{@rcode.string}\n";
    
    retval += ";; qdcount = #{@qdcount}  " +\
      "ancount = #{@ancount}  " +\
      "nscount = #{@nscount}  " +\
      "arcount = #{@arcount}\n";
  end
  
  return retval;
end