ISC DHCPD lease parsing

lease_parser.rb

def cache_leases
  leases = {}
  
  File.open('/path/to/dhcpd.leases', 'r').read.gsub(/\n/, '').split(/}/).each do |lease| 
    l = lease.split(';')
    if l.index('  next binding state free')
      l[0].gsub!(/.*lease (.*?) {.*/, '\1')
      leases[l[0]] = l if l[0] =~ /[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}/
    end

  end
  
  return leases
end

def mac_from_ip(ip)
  found = false
  leases = cache_leases
  if leases[ip]
    found = true
    @mac = leases[ip].grep(/hardware ethernet/)[0].gsub(/.*hardware ethernet (.*)/, '\1')
  end
  
  return found ? @mac : "MAC address not found!"
end

def ip_from_mac(mac)
  found = false 
  leases = cache_leases
  leases.each do |id,d|
    if d.include?("  hardware ethernet #{mac}")
      found = true
      @ip = id
    end
  end
  return found ? @ip : "IP address not found"
end


def count_leases
  leases = cache_leases
  return leases.count.to_s
end

sinatra_dhcp_cgi.rb

#!/usr/bin/env ruby

require 'sinatra'
require '/path/to/lease_parser.rb'


get '/ip_from_mac/:mac_address' do 
  mac = params[:mac_address].gsub(/%3A/, ':')
  if mac =~ /[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}/
    ip_from_mac(mac)
  else
    "NO - #{mac} invalid"
  end
end

get '/mac_from_ip/:ip_address' do
  if params[:ip_address] =~ /[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}/
    mac_from_ip(params[:ip_address])
  else
    "NO - #{ip} invalid"
  end
end

get '/count_leases/' do
  count_leases
end