ping.rb

require 'socket'

include Socket::Constants

#
# check for root
#
abort("re-run with root priviledges") unless Process::Sys.geteuid.zero?

#
# create a raw socket
#
raw_socket = Socket.new(AF_INET, SOCK_RAW, IPPROTO_ICMP)

#
# bind to specific device
#
raw_socket.setsockopt(SOL_SOCKET, SO_BINDTODEVICE, "tun0")

#
# create ICMP echo request
#
icmp_ereq = [0x08, 0x00, 0x89, 0x98, 0x6e, 0x63, 0x00, 0x04, 0x00].pack('C*')

#
# create ICMP echo reply
#
#icmp_erep = [0x00, 0x00, 0x91, 0x98, 0x6e, 0x00, 0x04, 0x00].pack('C*')

#
# send message 
#
raw_socket.send(icmp_ereq, 0, Socket.sockaddr_in(0, '8.8.8.8'))

#
# read reply
#
reply, ai = raw_socket.recvfrom(1024)

if reply
  fqdn = ai.getnameinfo[0]
  $stdout.puts reply
  $stdout.puts "Received reply from: #{fqdn}"
end