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.



718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
 
# File 'lib/Dnsruby/message.rb', line 718

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



670
671
672
 
# File 'lib/Dnsruby/message.rb', line 670

def aa
  @aa
end

#ad ⇒ Object

The Authenticated Data flag 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.)



686
687
688
 
# File 'lib/Dnsruby/message.rb', line 686

def ad
  @ad
end

#ancount ⇒ Object Also known as: prcount

The number of records in the answer section of the message



714
715
716
 
# File 'lib/Dnsruby/message.rb', line 714

def ancount
  @ancount
end

#arcount ⇒ Object Also known as: adcount

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



716
717
718
 
# File 'lib/Dnsruby/message.rb', line 716

def arcount
  @arcount
end

#cd ⇒ Object

The Checking Disabled flag



679
680
681
 
# File 'lib/Dnsruby/message.rb', line 679

def cd
  @cd
end

#id ⇒ Object

The header ID



664
665
666
 
# File 'lib/Dnsruby/message.rb', line 664

def id
  @id
end

#nscount ⇒ Object Also known as: upcount

The number of records in the authoriy section of the message



712
713
714
 
# File 'lib/Dnsruby/message.rb', line 712

def nscount
  @nscount
end

#opcode ⇒ Object

The header opcode



707
708
709
 
# File 'lib/Dnsruby/message.rb', line 707

def opcode
  @opcode
end

#qdcount ⇒ Object Also known as: zocount

The number of records in the question section of the message



710
711
712
 
# File 'lib/Dnsruby/message.rb', line 710

def qdcount
  @qdcount
end

#qr ⇒ Object

The query response flag



667
668
669
 
# File 'lib/Dnsruby/message.rb', line 667

def qr
  @qr
end

#ra ⇒ Object

Recursion available flag



692
693
694
 
# File 'lib/Dnsruby/message.rb', line 692

def ra
  @ra
end

#rd ⇒ Object

Recursion Desired flag



676
677
678
 
# File 'lib/Dnsruby/message.rb', line 676

def rd
  @rd
end

#tc ⇒ Object

Truncated flag



673
674
675
 
# File 'lib/Dnsruby/message.rb', line 673

def tc
  @tc
end

Class Method Details

.decrement_arcount_encoded(bytes) ⇒ Object 



778
779
780
781
782
783
784
785
786
787
788
789
 
# File 'lib/Dnsruby/message.rb', line 778

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 



747
748
749
750
751
752
 
# File 'lib/Dnsruby/message.rb', line 747

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

Instance Method Details

#==(other) ⇒ Object 



791
792
793
794
795
796
797
798
799
800
801
 
# File 'lib/Dnsruby/message.rb', line 791

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.get_header_rcode
end

#data ⇒ Object 



754
755
756
757
758
 
# File 'lib/Dnsruby/message.rb', line 754

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

#decode(msg) ⇒ Object 



840
841
842
843
844
845
846
847
848
849
850
851
852
 
# File 'lib/Dnsruby/message.rb', line 840

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 



760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
 
# File 'lib/Dnsruby/message.rb', line 760

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_header_rcode ⇒ Object

This new get_header_rcode method is intended for use only by the Message class. This is because the Message OPT section may contain an extended rcode (see RFC 2671 section 4.6). Using the header rcode only ignores this extension, and is not recommended.



702
703
704
 
# File 'lib/Dnsruby/message.rb', line 702

def get_header_rcode
  @rcode
end

#rcode=(rcode) ⇒ Object 



743
744
745
 
# File 'lib/Dnsruby/message.rb', line 743

def rcode=(rcode)
  @rcode = RCode.new(rcode)
end

#to_s ⇒ Object 



803
804
805
 
# File 'lib/Dnsruby/message.rb', line 803

def to_s
  to_s_with_rcode(@rcode)
end

#to_s_with_rcode(rcode) ⇒ Object 



807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
 
# File 'lib/Dnsruby/message.rb', line 807

def to_s_with_rcode(rcode)
  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