Class: PacketGen::Header::DNS::RR

Inherits:
Question show all
Defined in:
lib/packetgen/header/dns/rr.rb

Overview

DNS Ressource Record

Author:

  • Sylvain Daubert

Since:

  • 1.3.0

Direct Known Subclasses

OPT

Constant Summary

Constants inherited from Question

Question::CLASSES, Question::TYPES

Instance Attribute Summary collapse

Attributes inherited from Question

#name, #rrclass, #type

Attributes inherited from Base

#packet

Instance Method Summary collapse

Methods inherited from Question

#has_type?, #human_type, #type?

Methods inherited from Base

#added_to_packet, bind, bind_header, calculate_and_set_length, #header_id, inherited, #ip_header, known_headers, #ll_header, #method_name, #parse?, #protocol_name, protocol_name

Methods inherited from Types::Fields

#[], #[]=, #bits_on, #body=, define_bit_fields_on, define_field, define_field_after, define_field_before, delete_field, fields, #fields, #force_binary, inherited, #inspect, #is_optional?, #is_present?, #offset_of, #optional?, #optional_fields, #present?, #read, remove_bit_fields_on, remove_field, #sz, #to_h, #to_s, update_field

Constructor Details

#initialize(dns, options = {}) ⇒ RR

Returns a new instance of RR.

Parameters:

  • dns (DNS)
  • options (Hash) (defaults to: {})

Options Hash (options):

  • :name (String) —

    domain as a dotted string

  • :type (Integer, String) —

    see Question::TYPES. Default to ‘A’

  • :rrclass (Integer, String) —

    see Question::CLASSES. Default to ‘IN’

  • :ttl (Integer)
  • :rdlength (Integer) —

    if not provided, automatically set from :rdata length

  • :rdata (String)

Since:

  • 1.3.0



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# File 'lib/packetgen/header/dns/rr.rb', line 36

def initialize(dns, options={})
  super
  return unless options[:rdata] && options[:rdlength].nil?
  self.rdata = options[:rdata]
end

Instance Attribute Details

#rdata ⇒ Types::String

Returns:



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# File 'lib/packetgen/header/dns/rr.rb', line 24

define_field :rdata, Types::String,
builder: ->(rr, t) { t.new(length_from: rr[:rdlength]) }

#rdlength ⇒ Integer

16-bit #rdata length

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/dns/rr.rb', line 21

define_field :rdlength, Types::Int16

#ttl ⇒ Integer

32-bit time to live

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/dns/rr.rb', line 17

define_field :ttl, Types::Int32

Instance Method Details

#human_rdata ⇒ String

Get human readable rdata

Returns:

  • (String)

Since:

  • 1.3.0



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# File 'lib/packetgen/header/dns/rr.rb', line 52

def human_rdata
  str = self[:rdata].inspect

  # Need to mask: mDNS uses leftmost bit as a flag (CACHE FLUSH)
  if self.rrclass & 0x7fff == CLASSES['IN']
    case type
    when TYPES['A'], TYPES['AAAA']
      str = IPAddr.new_ntoh(self[:rdata]).to_s
    end
  end

  name = Name.new
  name.dns = self[:name].dns
  case type
  when TYPES['NS'], TYPES['PTR'], TYPES['CNAME']
    str = name.read(self[:rdata]).to_human
  when TYPES['SOA']
    mname = name.read(self[:rdata]).dup
    rname = name.read(self[:rdata][mname.sz..-1])
    serial = Types::Int32.new.read(self[:rdata][mname.sz + rname.sz, 4])
    refresh = Types::Int32.new.read(self[:rdata][mname.sz + rname.sz + 4, 4])
    retryi = Types::Int32.new.read(self[:rdata][mname.sz + rname.sz + 8, 4])
    expire = Types::Int32.new.read(self[:rdata][mname.sz + rname.sz + 12, 4])
    minimum = Types::Int32.new.read(self[:rdata][mname.sz + rname.sz + 16, 4])
    str = "#{mname.to_human} #{rname.to_human} #{serial.to_i} #{refresh.to_i} " \
          "#{retryi.to_i} #{expire.to_i} #{minimum.to_i}"
  when TYPES['MX']
    pref = Types::Int16.new.read(self[:rdata][0, 2])
    exchange = name.read(self[:rdata][2..-1]).to_human
    str = '%u %s' % [pref.to_i, exchange]
  when TYPES['SRV']
    priority = Types::Int16.new.read(self[:rdata][0, 2])
    weight = Types::Int16.new.read(self[:rdata][2, 2])
    port = Types::Int16.new.read(self[:rdata][4, 2])
    target = name.read(self[:rdata][6, self[:rdata].size]).to_human
    str = "#{priority.to_i} #{weight.to_i} #{port.to_i} #{target}"
  end

  str
end

#human_rrclass ⇒ String

Get human readable class

Returns:

  • (String)

Since:

  • 1.3.0



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# File 'lib/packetgen/header/dns/rr.rb', line 95

def human_rrclass
  if self[:name].dns.is_a? MDNS
    str = self.class::CLASSES.key(self.rrclass & 0x7fff) || '0x%04x' % (self.rrclass & 0x7fff)
    str += ' CACHE-FLUSH' if self.rrclass & 0x8000 > 0
    str
  else
    self.class::CLASSES.key(self.rrclass) || '0x%04x' % self.rrclass
  end
end

#to_human ⇒ String

Returns:

  • (String)

Since:

  • 1.3.0



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# File 'lib/packetgen/header/dns/rr.rb', line 106

def to_human
  "#{human_type} #{human_rrclass} #{name} TTL #{ttl} #{human_rdata}"
end