From: Daniel Berger <djberg96@...>
Date: 2006-12-01T04:47:05+09:00
Subject: Re: cidr.rb: port of Perl's Net::CIDR v0.11 available

Jos Backus wrote:

<snip>
>> r issue, and probably not worth the API breakage.
>>     
>
> It eases the transition from Perl, as in my case. If you mean something like
> the following then that would be great:
>
>     lizzy:/tmp% cat r
>     class Ping
>       def self.create(type, *args)
> 	case type
> 	when :foo
> 	  FooPing.new
> 	when :bar
> 	  BarPing.new
> 	end
>       end
>     end
>
>     class FooPing < Ping
>       def ping(host)
> 	puts "#{self.class}: pinging #{host}"
>       end
>     end
>
>     class BarPing < Ping
>       def ping(host)
> 	puts "#{self.class}: pinging #{host}"
>       end
>     end
>
>     pinger = Ping.create(:bar)
>     pinger.ping("myhost")
>     lizzy:/tmp% ruby r
>     BarPing: pinging myhost
>     lizzy:/tmp% 
>
> Let me know what I can do to help move this along.
>
>   
Well, you could start by porting the ping_icmp() function from Ping.pm 
to Ruby.  I started working on it but I got stuck and I need to work on 
other things.  Below is what I've got so far:

require 'net/ping'

module Net
   class Ping::ICMP < Ping   

      ICMP_ECHOREPLY = 0
      ICMP_ECHO      = 8
      ICMP_SUBCODE   = 0
      ICMP_FLAGS     = 0
      ICMP_PORT      = 0

      def initialize(*args)
         super(args)
         raise 'requires root privileges' if Process.euid > 0 # unsure
         @seq = 0
         @data_size = 0
         @data = ""
      end

      def checksum(msg)
         length    = msg.length
         num_short = length / 2
         check     = 0

         msg.unpack("n#{num_short}").each do |short|
            check += short
         end

         if length % 2 > 0
            check += msg[length-1, 1].unpack('C') << 8
         end

         check = (check >> 16) + (check & 0xffff)
         return (~((check >> 16) + check) & 0xffff)
      end

      def ping
         socket = Socket.new(
            Socket::PF_INET,
            Socket::SOCK_RAW,
            Socket::IPPROTO_ICMP
         )

         @seq = (@seq + 1) % 65536
         checksum = 0

         pstring = "C2 n3 A" << @data_size.to_s
         pid = Process.pid

         msg = [ICMP_ECHO, ICMP_SUBCODE, checksum, pid, @seq, 
@data].pack(pstring)
         # TODO: finish
      end
   end
end

Regards,

Dan