Class: PacketGen::Header::IP

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

Overview

A IP header consists of:

Create a IP header

# standalone
ip = PacketGen::Header::IP.new
# in a packet
pkt = PacketGen.gen('IP')
# access to IP header
pkt.ip   # => PacketGen::Header::IP

IP attributes

ip.u8 = 0x45
# the same as
ip.version = 4
ip.ihl = 5

ip.length = 0x43
ip.id = 0x1234

ip.frag = 0x2031
# the same as:
ip.flag_mf = true
ip.fragment_offset = 0x31

ip.flag_rsv?  # => Boolean
ip.flag_df?   # => Boolean
ip.flag_mf?   # => Boolean

ip.ttl = 0x40
ip.protocol = 6
ip.checksum = 0xffff
ip.src = '127.0.0.1'
ip.src                # => "127.0.0.1"
ip[:src]              # => PacketGen::Header::IP::Addr
ip.dst = '127.0.0.2'
ip.body.read 'this is a body'

Defined Under Namespace

Classes: Addr

Constant Summary collapse

ETHERTYPE =

IP Ether type

0x0800

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, #protocol_name

Methods inherited from Types::Fields

#[], #[]=, define_bit_fields_on, define_field, define_field_after, define_field_before, #fields, #force_binary, inherited, #initialize, #read, #sz, #to_h, #to_s

Constructor Details

This class inherits a constructor from PacketGen::Types::Fields

Instance Attribute Details

#body ⇒ Types::String, Header::Base

Returns:



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# File 'lib/packetgen/header/ip.rb', line 146

define_field :body, Types::String

#checksum ⇒ Integer

Returns 16-bit IP header checksum.

Returns:

  • (Integer) —

    16-bit IP header checksum



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# File 'lib/packetgen/header/ip.rb', line 137

define_field :checksum, Types::Int16, default: 0

#dst ⇒ Addr

Returns destination IP address.

Returns:

  • (Addr) —

    destination IP address



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# File 'lib/packetgen/header/ip.rb', line 143

define_field :dst, Addr, default: '127.0.0.1'

#flag_df ⇒ Boolean

Returns Don’t Fragment flag.

Returns:

  • (Boolean) —

    Don’t Fragment flag



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# File 'lib/packetgen/header/ip.rb', line 162

define_bit_fields_on :frag, :flag_rsv, :flag_df, :flag_mf, :fragment_offset, 13

#flag_mf ⇒ Boolean

Returns More Fragment flags.

Returns:

  • (Boolean) —

    More Fragment flags



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# File 'lib/packetgen/header/ip.rb', line 162

define_bit_fields_on :frag, :flag_rsv, :flag_df, :flag_mf, :fragment_offset, 13

#flag_rsv ⇒ Boolean

Returns reserved bit from flags.

Returns:

  • (Boolean) —

    reserved bit from flags



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# File 'lib/packetgen/header/ip.rb', line 162

define_bit_fields_on :frag, :flag_rsv, :flag_df, :flag_mf, :fragment_offset, 13

#frag ⇒ Integer

Returns 16-bit frag word.

Returns:

  • (Integer) —

    16-bit frag word



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# File 'lib/packetgen/header/ip.rb', line 128

define_field :frag, Types::Int16, default: 0

#fragment_offset ⇒ Integer

Returns 13-bit fragment offset.

Returns:

  • (Integer) —

    13-bit fragment offset



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# File 'lib/packetgen/header/ip.rb', line 162

define_bit_fields_on :frag, :flag_rsv, :flag_df, :flag_mf, :fragment_offset, 13

#id ⇒ Integer

Returns 16-bit ID.

Returns:

  • (Integer) —

    16-bit ID



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# File 'lib/packetgen/header/ip.rb', line 125

define_field :id, Types::Int16, default: -> { rand(65535) }

#ihl ⇒ Integer

Returns 4-bit IP header length attribute.

Returns:

  • (Integer) —

    4-bit IP header length attribute



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# File 'lib/packetgen/header/ip.rb', line 152

define_bit_fields_on :u8, :version, 4, :ihl, 4

#length ⇒ Integer

Returns 16-bit IP total length.

Returns:

  • (Integer) —

    16-bit IP total length



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# File 'lib/packetgen/header/ip.rb', line 122

define_field :length, Types::Int16, default: 20

#protocol ⇒ Integer

Returns 8-bit upper protocol value.

Returns:

  • (Integer) —

    8-bit upper protocol value



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# File 'lib/packetgen/header/ip.rb', line 134

define_field :protocol, Types::Int8

#src ⇒ Addr

Returns source IP address.

Returns:

  • (Addr) —

    source IP address



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# File 'lib/packetgen/header/ip.rb', line 140

define_field :src, Addr, default: '127.0.0.1'

#tos ⇒ Integer

Returns 8-bit Type of Service value.

Returns:

  • (Integer) —

    8-bit Type of Service value



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# File 'lib/packetgen/header/ip.rb', line 119

define_field :tos, Types::Int8, default: 0

#ttl ⇒ Integer

Returns 8-bit Time To Live value.

Returns:

  • (Integer) —

    8-bit Time To Live value



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# File 'lib/packetgen/header/ip.rb', line 131

define_field :ttl, Types::Int8, default: 64

#u8 ⇒ Integer

First byte of IP header. May be accessed through #version and #ihl.

Returns:

  • (Integer) —

    first byte of IP header.



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# File 'lib/packetgen/header/ip.rb', line 116

define_field :u8, Types::Int8, default: 0x45

#version ⇒ Integer

Returns 4-bit version attribute.

Returns:

  • (Integer) —

    4-bit version attribute



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# File 'lib/packetgen/header/ip.rb', line 152

define_bit_fields_on :u8, :version, 4, :ihl, 4

Instance Method Details

#calc_checksum ⇒ Integer

Compute checksum and set checksum field

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/ip.rb', line 166

def calc_checksum
  checksum = (self[:u8].to_i << 8) | self.tos
  checksum += self.length
  checksum += self.id
  checksum += self.frag
  checksum += (self.ttl << 8) | self.protocol
  checksum += (self[:src].to_i >> 16)
  checksum += (self[:src].to_i & 0xffff)
  checksum += self[:dst].to_i >> 16
  checksum += self[:dst].to_i & 0xffff
  checksum = (checksum & 0xffff) + (checksum >> 16)
  checksum = ~(checksum % 0xffff ) & 0xffff
  self[:checksum].value = (checksum == 0) ? 0xffff : checksum
end

#calc_length ⇒ Integer

Compute length and set length field

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/ip.rb', line 183

def calc_length
  self[:length].value = self.sz
end

#inspect ⇒ String

Returns:

  • (String) 


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# File 'lib/packetgen/header/ip.rb', line 207

def inspect
  str = Inspect.dashed_line(self.class, 2)
  shift = Inspect.shift_level(2)
  to_h.each do |attr, value|
    next if attr == :body
    str << Inspect.inspect_attribute(attr, value, 2)
    if attr == :u8
      str << shift + Inspect::INSPECT_FMT_ATTR % ['', 'version', version]
      str << shift + Inspect::INSPECT_FMT_ATTR % ['', 'ihl', ihl]
    elsif attr == :frag
      flags = flag_rsv? ? %w(RSV) : []
      flags << 'DF' if flag_df?
      flags << 'MF' if flag_mf?
      flags_str = flags.empty? ? 'none' : flags.join(',')
      str << shift + Inspect::INSPECT_FMT_ATTR % ['', 'flags', flags_str]
      foff = Inspect.int_dec_hex(fragment_offset, 4)
      str << shift + Inspect::INSPECT_FMT_ATTR % ['', 'frag_offset', foff]
    end
  end
  str
end

#parse? ⇒ Boolean

Check version field

Returns:

  • (Boolean)

See Also:

  • PacketGen::Header::IP.[Base[Base#parse?]


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# File 'lib/packetgen/header/ip.rb', line 231

def parse?
  version == 4
end

#pseudo_header_checksum ⇒ Integer

Get IP part of pseudo header checksum.

Returns:

  • (Integer) 


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# File 'lib/packetgen/header/ip.rb', line 189

def pseudo_header_checksum
  checksum = self[:src].to_i + self[:dst].to_i
  (checksum >> 16) + (checksum & 0xffff)
end

#to_w(iface = nil) ⇒ void

This method returns an undefined value.

Send IP packet on wire.

When sending packet at IP level, checksum and length fields are set by kernel, so bad IP packets cannot be sent this way. To do so, use Eth#to_w.

Parameters:

  • iface (String, nil) (defaults to: nil) —

    interface name. Not used



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# File 'lib/packetgen/header/ip.rb', line 200

def to_w(iface=nil)
  sock = Socket.new(Socket::AF_INET, Socket::SOCK_RAW, Socket::IPPROTO_RAW)
  sockaddrin = Socket.sockaddr_in(0, dst)
  sock.send to_s, 0, sockaddrin
end