This page hosts a formal specification of IPv4 network packet using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing 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-structParse a local file and get structure in memory:
data = Ipv4Packet.from_file("path/to/local/file.bin")
Or parse structure from a string of bytes:
bytes = "\x00\x01\x02..."
data = Ipv4Packet.new(Kaitai::Struct::Stream.new(bytes))
After that, one can get various attributes from the structure by invoking getter methods like:
data.b1 # => get b1
# 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 Ipv4Packet < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@b1 = @_io.read_u1
@b2 = @_io.read_u1
@total_length = @_io.read_u2be
@identification = @_io.read_u2be
@b67 = @_io.read_u2be
@ttl = @_io.read_u1
@protocol = @_io.read_u1
@header_checksum = @_io.read_u2be
@src_ip_addr = @_io.read_bytes(4)
@dst_ip_addr = @_io.read_bytes(4)
@_raw_options = @_io.read_bytes((ihl_bytes - 20))
_io__raw_options = Kaitai::Struct::Stream.new(@_raw_options)
@options = Ipv4Options.new(_io__raw_options, self, @_root)
@_raw_body = @_io.read_bytes((total_length - ihl_bytes))
_io__raw_body = Kaitai::Struct::Stream.new(@_raw_body)
@body = ProtocolBody.new(_io__raw_body, protocol)
self
end
class Ipv4Options < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@entries = []
i = 0
while not @_io.eof?
@entries << Ipv4Option.new(@_io, self, @_root)
i += 1
end
self
end
attr_reader :entries
end
class Ipv4Option < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@b1 = @_io.read_u1
@len = @_io.read_u1
@body = @_io.read_bytes((len > 2 ? (len - 2) : 0))
self
end
def copy
return @copy unless @copy.nil?
@copy = ((b1 & 128) >> 7)
@copy
end
def opt_class
return @opt_class unless @opt_class.nil?
@opt_class = ((b1 & 96) >> 5)
@opt_class
end
def number
return @number unless @number.nil?
@number = (b1 & 31)
@number
end
attr_reader :b1
attr_reader :len
attr_reader :body
end
def version
return @version unless @version.nil?
@version = ((b1 & 240) >> 4)
@version
end
def ihl
return @ihl unless @ihl.nil?
@ihl = (b1 & 15)
@ihl
end
def ihl_bytes
return @ihl_bytes unless @ihl_bytes.nil?
@ihl_bytes = (ihl * 4)
@ihl_bytes
end
attr_reader :b1
attr_reader :b2
attr_reader :total_length
attr_reader :identification
attr_reader :b67
attr_reader :ttl
attr_reader :protocol
attr_reader :header_checksum
attr_reader :src_ip_addr
attr_reader :dst_ip_addr
attr_reader :options
attr_reader :body
attr_reader :_raw_options
attr_reader :_raw_body
end