Reverse DNS lookup?

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!

···

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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

Thank you very much. That works perfectly :). Any reason why
getnamebyaddr didn't work because rubydocs seems to suggest that it
should.

Heesob Park wrote:

···

Hi,

2008/8/6 ga rg <khurrum1@gmail.com>:

TwoOctets = "10.26"

  append_to_file("unknown - #{current_ip} - #{mac_addr}")
    end
end

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

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