ICMP network packet: Ruby parsing library

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of ICMP network packet using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.

The Ruby runtime library can be installed from RubyGems:

gem install kaitai-struct

Code

Parse a local file and get structure in memory:

data = IcmpPacket.from_file("path/to/local/file.ICMP network packet")

Or parse structure from a string of bytes:

bytes = "\x00\x01\x02..."
data = IcmpPacket.new(Kaitai::Struct::Stream.new(bytes))

After that, one can get various attributes from the structure by invoking getter methods like:

data.icmp_type # => get icmp type

Ruby source code to parse ICMP network packet

icmp_packet.rb

# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

require 'kaitai/struct/struct'

unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
  raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end

class IcmpPacket < Kaitai::Struct::Struct

  ICMP_TYPE_ENUM = {
    0 => :icmp_type_enum_echo_reply,
    3 => :icmp_type_enum_destination_unreachable,
    4 => :icmp_type_enum_source_quench,
    5 => :icmp_type_enum_redirect,
    8 => :icmp_type_enum_echo,
    11 => :icmp_type_enum_time_exceeded,
  }
  I__ICMP_TYPE_ENUM = ICMP_TYPE_ENUM.invert
  def initialize(_io, _parent = nil, _root = self)
    super(_io, _parent, _root)
    _read
  end

  def _read
    @icmp_type = Kaitai::Struct::Stream::resolve_enum(ICMP_TYPE_ENUM, @_io.read_u1)
    if icmp_type == :icmp_type_enum_destination_unreachable
      @destination_unreachable = DestinationUnreachableMsg.new(@_io, self, @_root)
    end
    if icmp_type == :icmp_type_enum_time_exceeded
      @time_exceeded = TimeExceededMsg.new(@_io, self, @_root)
    end
    if  ((icmp_type == :icmp_type_enum_echo) || (icmp_type == :icmp_type_enum_echo_reply)) 
      @echo = EchoMsg.new(@_io, self, @_root)
    end
    self
  end
  class DestinationUnreachableMsg < Kaitai::Struct::Struct

    DESTINATION_UNREACHABLE_CODE = {
      0 => :destination_unreachable_code_net_unreachable,
      1 => :destination_unreachable_code_host_unreachable,
      2 => :destination_unreachable_code_protocol_unreachable,
      3 => :destination_unreachable_code_port_unreachable,
      4 => :destination_unreachable_code_fragmentation_needed_and_df_set,
      5 => :destination_unreachable_code_source_route_failed,
      6 => :destination_unreachable_code_dst_net_unkown,
      7 => :destination_unreachable_code_sdt_host_unkown,
      8 => :destination_unreachable_code_src_isolated,
      9 => :destination_unreachable_code_net_prohibited_by_admin,
      10 => :destination_unreachable_code_host_prohibited_by_admin,
      11 => :destination_unreachable_code_net_unreachable_for_tos,
      12 => :destination_unreachable_code_host_unreachable_for_tos,
      13 => :destination_unreachable_code_communication_prohibited_by_admin,
      14 => :destination_unreachable_code_host_precedence_violation,
      15 => :destination_unreachable_code_precedence_cuttoff_in_effect,
    }
    I__DESTINATION_UNREACHABLE_CODE = DESTINATION_UNREACHABLE_CODE.invert
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @code = Kaitai::Struct::Stream::resolve_enum(DESTINATION_UNREACHABLE_CODE, @_io.read_u1)
      @checksum = @_io.read_u2be
      self
    end
    attr_reader :code
    attr_reader :checksum
  end
  class TimeExceededMsg < Kaitai::Struct::Struct

    TIME_EXCEEDED_CODE = {
      0 => :time_exceeded_code_time_to_live_exceeded_in_transit,
      1 => :time_exceeded_code_fragment_reassembly_time_exceeded,
    }
    I__TIME_EXCEEDED_CODE = TIME_EXCEEDED_CODE.invert
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @code = Kaitai::Struct::Stream::resolve_enum(TIME_EXCEEDED_CODE, @_io.read_u1)
      @checksum = @_io.read_u2be
      self
    end
    attr_reader :code
    attr_reader :checksum
  end
  class EchoMsg < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @code = @_io.read_bytes(1)
      raise Kaitai::Struct::ValidationNotEqualError.new([0].pack('C*'), code, _io, "/types/echo_msg/seq/0") if not code == [0].pack('C*')
      @checksum = @_io.read_u2be
      @identifier = @_io.read_u2be
      @seq_num = @_io.read_u2be
      @data = @_io.read_bytes_full
      self
    end
    attr_reader :code
    attr_reader :checksum
    attr_reader :identifier
    attr_reader :seq_num
    attr_reader :data
  end
  attr_reader :icmp_type
  attr_reader :destination_unreachable
  attr_reader :time_exceeded
  attr_reader :echo
end