Class: Dnsruby::Header

Inherits:
Object
  • Object
show all
Defined in:
lib/dnsruby/message/header.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/header.rb', line 64

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/header.rb', line 16

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.)



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# File 'lib/dnsruby/message/header.rb', line 32

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/header.rb', line 60

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/header.rb', line 62

def arcount
  @arcount
end

#cd ⇒ Object

The Checking Disabled flag



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# File 'lib/dnsruby/message/header.rb', line 25

def cd
  @cd
end

#id ⇒ Object

The header ID



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# File 'lib/dnsruby/message/header.rb', line 10

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/header.rb', line 58

def nscount
  @nscount
end

#opcode ⇒ Object

The header opcode



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# File 'lib/dnsruby/message/header.rb', line 53

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/header.rb', line 56

def qdcount
  @qdcount
end

#qr ⇒ Object

The query response flag



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# File 'lib/dnsruby/message/header.rb', line 13

def qr
  @qr
end

#ra ⇒ Object

Recursion available flag



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# File 'lib/dnsruby/message/header.rb', line 38

def ra
  @ra
end

#rd ⇒ Object

Recursion Desired flag



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# File 'lib/dnsruby/message/header.rb', line 22

def rd
  @rd
end

#tc ⇒ Object

Truncated flag



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# File 'lib/dnsruby/message/header.rb', line 19

def tc
  @tc
end

Class Method Details

.decrement_arcount_encoded(bytes) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 121

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

.new_from_data(data) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 93

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

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 133

def ==(other)
  @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/header.rb', line 99

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

#decode(msg) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 222

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

#encode(msg) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 103

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/header.rb', line 48

def get_header_rcode
  @rcode
end

#old_to_s ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 149

def old_to_s
  old_to_s_with_rcode(@rcode)
end

#old_to_s_with_rcode(rcode) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 189

def old_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

  retval
end

#rcode=(rcode) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 89

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

#to_s ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 145

def to_s
  to_s_with_rcode(@rcode)
end

#to_s_with_rcode(rcode) ⇒ Object 



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# File 'lib/dnsruby/message/header.rb', line 153

def to_s_with_rcode(rcode)

  if @opcode == OpCode::Update
    s = ";; id = #{@id}\n"
    s << ";; qr = #{@qr}    opcode = #{@opcode.string}    rcode = #{@rcode.string}\n"
    s << ";; zocount = #{@qdcount}  "
    s <<  "prcount = #{@ancount}  "
    s <<  "upcount = #{@nscount}  "
    s <<  "adcount = #{@arcount}\n"
    s
  else

    flags_str = begin
      flags = []
      flags << 'qr' if @qr
      flags << 'aa' if @aa
      flags << 'tc' if @tc
      flags << 'rd' if @rd
      flags << 'ra' if @ra
      flags << 'ad' if @ad
      flags << 'cd' if @cd

      ";; flags: #{flags.join(' ')}; "
    end

    head_line_str =
        ";; ->>HEADER<<- opcode: #{opcode.string.upcase}, status: #{@rcode.string}, id: #{@id}\n"

    section_counts_str =
        "QUERY: #{@qdcount}, ANSWER: #{@ancount}, AUTHORITY: #{@nscount}, ADDITIONAL: #{@arcount}\n"

    head_line_str + flags_str + section_counts_str
  end
end