text: #! /usr/bin/env python
  # vim: set fenc=utf8 ts=4 sw=4 et :
  #
  # Layer 2 network neighbourhood discovery tool
  # written by Benedikt Waldvogel (mail at bwaldvogel.de)
  
  '''
  MODIFICATIONS FROM ORIGINAL SOURCE:
      *renamed main() to neighborhood()
      *removed if __name__ == "__main__" block
      *removed usage()
      *streamlined neighborhood() to return IP's in LAN
      *added Benedikt Waldvogel's MIT license (this is substantially his work)
  
  -Christopher Naimo
  '''
  
  
  '''
  Copyright (c) 2013 Benedikt Waldvogel
  
  Permission is hereby granted, free of charge, to any person obtaining a copy of
  this software and associated documentation files (the "Software"), to deal in
  the Software without restriction, including without limitation the rights to
  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  the Software, and to permit persons to whom the Software is furnished to do so,
  subject to the following conditions:
  
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  '''
  
  #from __future__ import absolute_import, division, print_function
  import logging
  import scapy.config
  import scapy.layers.l2
  import scapy.route
  import socket
  import math
  import errno
  import os
  import getopt
  import sys
  
  logging.basicConfig(format='%(asctime)s %(levelname)-5s %(message)s', datefmt='%Y-%m-%d %H:%M:%S', level=logging.DEBUG)
  logger = logging.getLogger(__name__)
  
  
  def long2net(arg):
      if (arg <= 0 or arg >= 0xFFFFFFFF):
          raise ValueError("illegal netmask value", hex(arg))
      return 32 - int(round(math.log(0xFFFFFFFF - arg, 2)))
  
  
  def to_CIDR_notation(bytes_network, bytes_netmask):
      network = scapy.utils.ltoa(bytes_network)
      netmask = long2net(bytes_netmask)
      net = "%s/%s" % (network, netmask)
      if netmask < 16:
          logger.warning("%s is too big. skipping" % net)
          return None
      return net
  
  
  def scan_and_print_neighbors(net, interface, timeout=5):
      logger.info("arping %s on %s" % (net, interface))
      ips = []
      try:
          ans, unans = scapy.layers.l2.arping(net, iface=interface, timeout=timeout, verbose=True)
          for s, r in ans.res:
              ips.append(r.sprintf("%ARP.psrc%"))
      except socket.error as e:
          if e.errno == errno.EPERM:     # Operation not permitted
              logger.error("%s. Did you run as root?", e.strerror)
          else:
              raise
      return ips
  
  
  def neighborhood(interface_to_scan=None):
      if os.geteuid() != 0:
          print('You need to be root to run this script', file=sys.stderr)
          sys.exit(1)
      ips = []
      for network, netmask, _, interface, address, _ in scapy.config.conf.route.routes:
          if interface_to_scan and interface_to_scan != interface:
              continue
          # skip loopback network and default gw
          if network == 0 or interface == 'lo' or address == '127.0.0.1' or address == '0.0.0.0':
              continue
          if netmask <= 0 or netmask == 0xFFFFFFFF:
              continue
          # skip docker interface
          if interface != interface_to_scan and interface.startswith('docker') or interface.startswith('br-'):
              logger.warning("Skipping interface '%s'" % interface)
              continue
          net = to_CIDR_notation(network, netmask)
          if net:
              ips.extend(scan_and_print_neighbors(net, interface))
          print("EARLY BREAK ######################")
          print("EARLY BREAK ######################")
          break
      return ips
  