Reverse DNS in Ruby?

Reverse DNS in Ruby?

"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."