Class: PacketGen::Header::GRE

Inherits:
Base show all
Defined in:
lib/packetgen/header/gre.rb

Overview

Generic Routing Encapsulation (RFC 2784 and 2890)

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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| |K|S| Reserved0       | Ver |         Protocol Type         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Checksum (optional)      |       Reserved1 (Optional)    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Key (optional)                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                 Sequence Number (Optional)                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Author:

  • Sylvain Daubert

Constant Summary collapse

IP_PROTOCOL =

IP protocol number for GRE

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Instance Attribute Summary collapse

Attributes inherited from Base

#packet

Instance Method Summary collapse

Methods inherited from Base

bind_header, #header_id, inherited, #ip_header, known_headers, #method_name, #parse?, protocol_name, #protocol_name

Methods inherited from Types::Fields

#[], #[]=, define_bit_fields_on, define_field, define_field_after, define_field_before, delete_field, #fields, #force_binary, inherited, #inspect, #is_optional?, #is_present?, #optional_fields, #read, #sz, #to_h, #to_s

Constructor Details

#initialize(options = {}) ⇒ GRE

Returns a new instance of GRE.



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# File 'lib/packetgen/header/gre.rb', line 63

def initialize(options={})
  opts = { r: false, reserved0: 0, version: 0 }.merge(options)
  super(opts)
end

Instance Attribute Details

#body ⇒ Types::String, Header::Base

Returns:



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# File 'lib/packetgen/header/gre.rb', line 58

define_field :body, Types::String

#c ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/packetgen/header/gre.rb', line 39

define_bit_fields_on :u16, :c, :r, :k, :s, :reserved0, 9, :ver, 3

#checksum ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/gre.rb', line 46

define_field :checksum, Types::Int16, default: 0, optional: ->(gre) { gre.c? }

#k ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/packetgen/header/gre.rb', line 39

define_bit_fields_on :u16, :c, :r, :k, :s, :reserved0, 9, :ver, 3

#key ⇒ Integer

Returns:

  • (Integer) 


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

define_field :key, Types::Int32, optional: ->(gre) { gre.k? }

#protocol_type ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/gre.rb', line 43

define_field :protocol_type, Types::Int16

#reserved0 ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/gre.rb', line 39

define_bit_fields_on :u16, :c, :r, :k, :s, :reserved0, 9, :ver, 3

#reserved1 ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/gre.rb', line 49

define_field :reserved1, Types::Int16, default: 0, optional: ->(gre) { gre.c? }

#s ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/packetgen/header/gre.rb', line 39

define_bit_fields_on :u16, :c, :r, :k, :s, :reserved0, 9, :ver, 3

#sequence_number ⇒ Integer Also known as: seqnum

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/gre.rb', line 55

define_field :sequence_number, Types::Int32, optional: ->(gre) { gre.s? }

#ver ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/gre.rb', line 39

define_bit_fields_on :u16, :c, :r, :k, :s, :reserved0, 9, :ver, 3

Instance Method Details

#calc_checksum ⇒ Integer

Compute checksum and set checksum field

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/gre.rb', line 70

def calc_checksum
  str = to_s
  str << "\x00" if str.length % 2 == 1
  sum = str.unpack('n*').reduce(:+)

  while sum > 0xffff do
    sum = (sum & 0xffff) + (sum >> 16)
  end
  sum = ~sum & 0xffff
  self[:checksum].value = (sum == 0) ? 0xffff : sum
end