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
@@identifier = 
-1

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 396

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 354

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 370

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 392

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 394

def arcount
  @arcount
end

#cd ⇒ Object

The checking disabled flag



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# File 'lib/Dnsruby/message.rb', line 363

def cd
  @cd
end

#dnssec_ok ⇒ Object

The DO (dnssec OK) flag



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# File 'lib/Dnsruby/message.rb', line 373

def dnssec_ok
  @dnssec_ok
end

#id ⇒ Object

The header ID



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# File 'lib/Dnsruby/message.rb', line 348

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 390

def nscount
  @nscount
end

#opcode ⇒ Object

The header opcode



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# File 'lib/Dnsruby/message.rb', line 385

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 388

def qdcount
  @qdcount
end

#qr ⇒ Object

The query response flag



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# File 'lib/Dnsruby/message.rb', line 351

def qr
  @qr
end

#ra ⇒ Object

Recursion available flag



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# File 'lib/Dnsruby/message.rb', line 379

def ra
  @ra
end

#rcode ⇒ Object

Query response code



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# File 'lib/Dnsruby/message.rb', line 382

def rcode
  @rcode
end

#rd ⇒ Object

Recursion Desired flag



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# File 'lib/Dnsruby/message.rb', line 360

def rd
  @rd
end

#tc ⇒ Object

Truncated flag



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# File 'lib/Dnsruby/message.rb', line 357

def tc
  @tc
end

Class Method Details

.new_from_data(data) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 425

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 456

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 432

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 501

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 438

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

#getException ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 523

def getException
  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 468

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