Class: PacketFu::ICMPHeader

Inherits:
Struct
  • Object
show all
Includes:
StructFu
Defined in:
lib/packetfu/protos/icmp/header.rb

Overview

ICMPHeader is a complete ICMP struct, used in ICMPPacket. ICMP is typically used for network administration and connectivity testing.

For more on ICMP packets, see www.networksorcery.com/enp/protocol/icmp.htm

Header Definition

Int8    :icmp_type                        # Type
Int8    :icmp_code                        # Code
Int16   :icmp_sum    Default: calculated  # Checksum
String  :body

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from StructFu

#clone, #set_endianness, #sz, #typecast

Methods inherited from Struct

#force_binary

Constructor Details

#initialize(args = {}) ⇒ ICMPHeader

Returns a new instance of ICMPHeader


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# File 'lib/packetfu/protos/icmp/header.rb', line 19

def initialize(args={})
  super(
    Int8.new(args[:icmp_type]),
    Int8.new(args[:icmp_code]),
    Int16.new(args[:icmp_sum] || icmp_calc_sum),
    StructFu::String.new.read(args[:body])
  )
end

Instance Attribute Details

#bodyObject

Returns the value of attribute body

Returns:

  • (Object)

    the current value of body


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# File 'lib/packetfu/protos/icmp/header.rb', line 15

def body
  @body
end

#icmp_codeObject

Getter for the code.


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# File 'lib/packetfu/protos/icmp/header.rb', line 15

def icmp_code
  @icmp_code
end

#icmp_sumObject

Getter for the checksum.


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# File 'lib/packetfu/protos/icmp/header.rb', line 15

def icmp_sum
  @icmp_sum
end

#icmp_typeObject

Getter for the type.


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# File 'lib/packetfu/protos/icmp/header.rb', line 15

def icmp_type
  @icmp_type
end

Instance Method Details

#icmp_calc_sumObject

Calculates and sets the checksum for the object.


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# File 'lib/packetfu/protos/icmp/header.rb', line 59

def icmp_calc_sum
  checksum = (icmp_type.to_i << 8)	+ icmp_code.to_i
  chk_body = (body.to_s.size % 2 == 0 ? body.to_s : body.to_s + "\x00")
  if 1.respond_to? :ord
    chk_body.split("").each_slice(2).map { |x| (x[0].ord << 8) + x[1].ord }.each { |y| checksum += y }
  else
    chk_body.split("").each_slice(2).map { |x| (x[0] << 8) + x[1] }.each { |y| checksum += y }
  end
  checksum = checksum % 0xffff
  checksum = 0xffff - checksum
  checksum == 0 ? 0xffff : checksum
end

#icmp_recalc(arg = :all) ⇒ Object

Recalculates the calculatable fields for ICMP.


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# File 'lib/packetfu/protos/icmp/header.rb', line 73

def icmp_recalc(arg=:all)
  # How silly is this, you can't intern a symbol in ruby 1.8.7pl72?
  # I'm this close to monkey patching Symbol so you can force it...
  arg = arg.intern if arg.respond_to? :intern
  case arg
  when :icmp_sum
    self.icmp_sum=icmp_calc_sum
  when :all
    self.icmp_sum=icmp_calc_sum
  else
    raise ArgumentError, "No such field `#{arg}'"
  end
end

#icmp_sum_readableObject

Readability aliases


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# File 'lib/packetfu/protos/icmp/header.rb', line 89

def icmp_sum_readable
  "0x%04x" % icmp_sum
end

#read(str) ⇒ Object

Reads a string to populate the object.


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# File 'lib/packetfu/protos/icmp/header.rb', line 34

def read(str)
  force_binary(str)
  return self if str.nil?
  self[:icmp_type].read(str[0,1])
  self[:icmp_code].read(str[1,1])
  self[:icmp_sum].read(str[2,2])
  self[:body].read(str[4,str.size])
  self
end

#to_sObject

Returns the object in string form.


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# File 'lib/packetfu/protos/icmp/header.rb', line 29

def to_s
  self.to_a.map {|x| x.to_s}.join
end