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+--- Forum: Ruby (https://0day.red/Forum-Ruby)
+--- Thread: Reverse DNS in Ruby? (/Thread-Reverse-DNS-in-Ruby)
Reverse DNS in Ruby? - disremember639167 - 07-19-2023
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.
RE: Reverse DNS in Ruby? - coralineet - 07-19-2023
This also works:
host_name = Socket.getaddrinfo(current_ip,nil)
append_to_file("#{host_name[0][2]} - #{current_ip} - #{mac_addr}\n")
I'm not sure why `gethostbyaddr` didn't also work.
RE: Reverse DNS in Ruby? - Mrxanthuria926 - 07-19-2023
I would check out `getaddrinfo`. If you replace the line:
host_name = Socket.gethostbyname(current_ip)
with:
host_name = Socket.getaddrinfo(current_ip, 0, Socket::AF_UNSPEC, Socket::SOCK_STREAM, nil, Socket::AI_CANONNAME)[0][1]
The `getaddrinfo` function returns an array of arrays. You can read more about it at:
[Ruby Socket Docs](
[To see links please register here]
)RE: Reverse DNS in Ruby? - tovatovar295 - 07-19-2023
Today I also needed reverse DNS lookup and I've found very simple standard solution:
require 'resolv'
host_name = Resolv.getname(ip_address_here)
It seems it uses timeout which helps in rough cases.