From: Daniel Berger <djberg96@...>
Date: 2006-12-02T04:54:49+09:00
Subject: Re: cidr.rb: port of Perl's Net::CIDR v0.11 available

Jos Backus wrote:
> On Fri, Dec 01, 2006 at 04:47:05AM +0900, Daniel Berger wrote:
>> 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:
> 
> I've made some progress; see attached. Let me know what you think.
> 
> 
> 
> ------------------------------------------------------------------------
> 
> #!/usr/bin/env ruby
> 
> require 'rubygems'
> require 'net/ping'
> 
> module Net
>   class Ping::ICMP < Ping   
> 
>     ICMP_ECHOREPLY = 0
>     ICMP_ECHO      = 8
>     ICMP_STRUCT    = 'C2 n3 A'
>     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 = ''
>       @pid = Process.pid & 0xffff
>     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(ip, timeout)
>       ret = nil
>       socket = Socket.new(
>         Socket::PF_INET,
>         Socket::SOCK_RAW,
>         Socket::IPPROTO_ICMP
>       )
> 
>       @seq = (@seq + 1) % 65536
>       pstring = 'C2 n3 A' << @data_size.to_s
> 
>       checksum = 0
>       msg = [ICMP_ECHO, ICMP_SUBCODE, checksum, @pid, @seq, @data].pack(pstring)
>       checksum = checksum(msg)
>       msg = [ICMP_ECHO, ICMP_SUBCODE, checksum, @pid, @seq, @data].pack(pstring)
> 
>       begin
>       saddr = Socket.pack_sockaddr_in(ICMP_PORT, ip)
>       rescue => exc
> 	return nil
>       end
> 
>       @from_ip = @from_type = @from_subcode = nil
>       socket.send(msg, ICMP_FLAGS, saddr) # Send the message
> 
>       done = false
>       finish_time = Time.now + timeout
>       while !done and timeout > 0
>         nfound = select([socket], nil, nil, timeout)
> 	timeout = finish_time - Time.now
>         if nfound.nil? # timed out
>           ret = nil
>           done = true
>         elsif !nfound[0].empty?
>           recv_msg = ''
>           from_pid = -1
>           from_seq = -1
>           recv_msg, from_saddr = socket.recvfrom(1500, ICMP_FLAGS)
>           from_port, from_ip = Socket.unpack_sockaddr_in(from_saddr)
>           from_type, from_subcode = recv_msg[20, 2].unpack('C2')
>           case from_type
>           when ICMP_ECHOREPLY
>             if recv_msg.length >= 28
>               from_pid, from_seq = recv_msg[24, 4].unpack('n3')
>             end
>           else
>             if recv_msg.length >= 56
>               from_pid, from_seq = recv_msg[52, 4].unpack('n3')
>             end
>           end
>           @from_ip = from_ip
>           @from_type = from_type
>           @from_subcode = from_subcode
>           if from_pid == @pid and from_seq == @seq
>             if from_type == ICMP_ECHOREPLY
>               ret = 1
>             end
>             done = true
>           end
>         else
> 	  # Shouldn't happen
>           done = true
>         end
>       end
>       return ret
>     end
> 
>   end
> 
> end
> 
> p = Net::Ping::ICMP.new
> p p.ping(ARGV.shift, 5)

Seems to work.  Mind if I include with the next release of net-ping 
(with acknowledgements, of course).

The only tweak I would make are to have it return true or false, instead 
of 1 or nil.

Regards,

Dan