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 708

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 657

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 669

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 704

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 706

def arcount
  @arcount
end

#cd ⇒ Object

The Checking Disabled flag



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

def cd
  @cd
end

#id ⇒ Object

The header ID



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# File 'lib/Dnsruby/message.rb', line 651

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 702

def nscount
  @nscount
end

#opcode ⇒ Object

The header opcode



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# File 'lib/Dnsruby/message.rb', line 697

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 700

def qdcount
  @qdcount
end

#qr ⇒ Object

The query response flag



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# File 'lib/Dnsruby/message.rb', line 654

def qr
  @qr
end

#ra ⇒ Object

Recursion available flag



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# File 'lib/Dnsruby/message.rb', line 682

def ra
  @ra
end

#rd ⇒ Object

Recursion Desired flag



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# File 'lib/Dnsruby/message.rb', line 663

def rd
  @rd
end

#tc ⇒ Object

Truncated flag



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# File 'lib/Dnsruby/message.rb', line 660

def tc
  @tc
end

Class Method Details

.decrement_arcount_encoded(bytes) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 768

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 737

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 781

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 



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

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 830

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 750

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.



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

def get_header_rcode
  @rcode
end

#rcode=(rcode) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 733

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

#to_s ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 793

def to_s
  to_s_with_rcode(@rcode)
end

#to_s_with_rcode(rcode) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 797

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