From: Heesob Park <phasis@...>
Date: 2008-08-06T16:08:24+09:00
Subject: Re: Reverse DNS lookup?

Hi,

2008/8/6 ga rg <khurrum1@gmail.com>:
> I'm in an environment with a lot of computers that haven't been
> properly inventoried. Basically, no one knows which IP goes with which
> mac address and which hostname. So I wrote the following:
>
> # This script goes down the entire IP range and attempts to
> # retrieve the Hostname and mac address and outputs them
> # into a file. Yay!
>
> require "socket"
>
> TwoOctets = "10.26"
>
> def computer_exists?(computerip)
>  system("ping -c 1 -W 1 #{computerip}")
> end
>
> def append_to_file(line)
>  file   = File.open("output.txt", "a")
>  file.puts(line)
>  file.close
> end
>
>
> def getInfo(current_ip)
>  begin
>   if computer_exists?(current_ip)
>     arp_output = `arp -v #{current_ip}`
>     mac_addr = arp_output.to_s.match(/..:..:..:..:..:../)
>     host_name = Socket.gethostbyname(current_ip)
>     append_to_file("#{host_name[0]} - #{current_ip} - #{mac_addr}\n")
>   end
>  rescue SocketError => mySocketError
>   append_to_file("unknown - #{current_ip} - #{mac_addr}")
>  end
> end
>
>
> (6..8).each do |i|
>  case i
>   when 6
>     for j in (1..190)
>       current_ip = "#{TwoOctets}.#{i}.#{j}"
>       getInfo(current_ip)
>     end
>   when 7
>     for j in (1..255)
>       current_ip = "#{TwoOctets}.#{i}.#{j}"
>       getInfo(current_ip)
>     end
>   when 8
>     for j in (1..52)
>       current_ip = "#{TwoOctets}.#{i}.#{j}"
>       getInfo(current_ip)
>     end
>  end
> end
>
>
> Everything works except it does not find a Reverse DNS.
>
> Sample output that I'm getting is this:
>
> 10.26.6.12 - 10.26.6.12 - 00:11:11:9B:13:9F
> 10.26.6.17 - 10.26.6.17 - 08:00:69:9A:97:C3
> 10.26.6.18 - 10.26.6.18 - 08:00:69:93:2C:E2
>
> If I do `nslookup 10.26.6.12` then I get the correct reverse DNS so
> that shows that my machine is seeing the dns server.
>
> I have tried Socket.gethostbyname, gethostbyaddr, but it doesn't work :
> (
>
> Any guidance will be much appreciated. Thanks!
>
Try getaddrinfo like this:

s = Socket.getaddrinfo('10.26.6.12',nil)
hostname = s[0][2]


Regards,

Park Heesob