check_ip_address.r2py

def is_valid_ip_address(ipaddr):
  """
  <Purpose>
    Determines if ipaddr is a valid IP address.
    0.X and 224-255.X addresses are not allowed.
    Additionally, 192.168.0.0 is not allowed.

  <Arguments>
    ipaddr: String to check for validity. (It will check that this is a string).

  <Returns>
    True if a valid IP, False otherwise.
  """
  # Argument must be of the string type
  if not type(ipaddr) == str:
    log("IP address is not string type")
    return False

  if ipaddr == '192.168.0.0':
    log("IP address 192.168.0.0 is not allowed!!")
    return False

  # A valid IP should have 4 segments, explode on the period
  octets = ipaddr.split(".")

  # Check that we have 4 parts
  if len(octets) != 4:
    return False

  # Check that each segment is a number between 0 and 255 inclusively.
  for octet in octets:
    # Attempt to convert to an integer
    try:
      ipnumber = int(octet)
    except ValueError:
      # There was an error converting to an integer, not an IP
      log("IP address should have integer value!")
      return False

    # IP addresses octets must be between 0 and 255
    if not (ipnumber >= 0 and ipnumber <= 255):
      log("IP address should be in range of 0-255")
      return False

  # should not have a ValueError (I already checked)
  firstipnumber = int(octets[0])

  # IP addresses with the first octet 0 refer to all local IPs.   These are
  # not allowed
  if firstipnumber == 0:
    log("First Octet of IP address cannot be zero!")
    return False

  # IP addresses with the first octet >=224 are either Multicast or reserved.
  # These are not allowed
  if firstipnumber >= 224:
    log("Multicast address are not allowed to be used!")
    return False

  # At this point, assume the IP is valid
  log("The IP address mentioned is valid!")
  return True