Contents

require 'pio/payload'

module Pio
  # UDP Header Format.
  module UdpHeader
    include Payload

    # Pseudo UDP header
    class PseudoUdpHeader < BinData::Record
      endian :big
      ip_address :ip_source_address
      ip_address :ip_destination_address
      uint8 :padding
      uint8 :ip_protocol, value: IPv4Header::ProtocolNumber::UDP
      uint16 :udp_length
    end

    def self.included(klass)
      def klass.udp_header
        uint16 :udp_source_port
        uint16 :udp_destination_port
        uint16 :udp_length, initial_value: :calculate_udp_length
        uint16 :udp_checksum, initial_value: :calculate_udp_checksum
      end
    end

    private

    def calculate_udp_length
      8 + udp_payload_binary.length
    end

    def calculate_udp_checksum
      sum = [*pseudo_udp_header.unpack('n*'),
             udp_source_port,
             udp_destination_port,
             udp_length,
             *udp_payload_multiple_of_2octets.unpack('n*')].inject(:+)
      ~((sum & 0xffff) + (sum >> 16)) & 0xffff
    end

    def udp_payload_binary
      binary_after :udp_checksum
    end

    def pseudo_udp_header
      PseudoUdpHeader.new(ip_source_address: ip_source_address,
                          ip_destination_address: ip_destination_address,
                          udp_length: udp_length).to_binary_s
    end

    def udp_payload_multiple_of_2octets
      udp_payload_binary + '\x00' * (udp_payload_binary.length.even? ? 0 : 1)
    end
  end
end

Version data entries

20 entries across 20 versions & 1 rubygems

Version	Path
pio-0.27.2	lib/pio/udp_header.rb
pio-0.27.1	lib/pio/udp_header.rb
pio-0.27.0	lib/pio/udp_header.rb
pio-0.26.0	lib/pio/udp_header.rb
pio-0.25.0	lib/pio/udp_header.rb
pio-0.24.2	lib/pio/udp_header.rb
pio-0.24.1	lib/pio/udp_header.rb
pio-0.24.0	lib/pio/udp_header.rb
pio-0.23.1	lib/pio/udp_header.rb
pio-0.23.0	lib/pio/udp_header.rb
pio-0.22.0	lib/pio/udp_header.rb
pio-0.21.1	lib/pio/udp_header.rb
pio-0.21.0	lib/pio/udp_header.rb
pio-0.20.1	lib/pio/udp_header.rb
pio-0.20.0	lib/pio/udp_header.rb
pio-0.19.0	lib/pio/udp_header.rb
pio-0.18.2	lib/pio/udp_header.rb
pio-0.18.1	lib/pio/udp_header.rb
pio-0.18.0	lib/pio/udp_header.rb
pio-0.17.0	lib/pio/udp_header.rb