#!/usr/bin/env python
#
# Nagios check if interlink is still found via SNMP
#
# Orginal by Richard van Mansom
# Modified to be more readable and debugable by Rick van der Zwet
#

from collections import defaultdict
from pysnmp.entity.rfc3413.oneliner import cmdgen
from pysnmp.proto.rfc1902 import OctetString
from gettext import gettext as _

import argparse
import logging
import operator
import socket
import sys

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger()

class ERRNO():
  OK = 0
  WARNING = 1
  CRITICAL = 2
  UNKNOWN = 3
  


def snmpwalk(host, oid):
  errorIndication, errorStatus, errorIndex, varBinds = cmdgen.CommandGenerator().bulkCmd(
    cmdgen.CommunityData('my-agent', 'public', 1),
    cmdgen.UdpTransportTarget((host, 161)),
    15, 0, # nonRepeaters, maxRepetitions
    oid
  )
  return varBinds



def get_all_macs(host):
  all_macs = defaultdict(list)
  lines = snmpwalk(host, (1,3,6,1,2,1,3,1,1,2))

  for line in lines:
    try:
      if line[0][0][9] == 2:
        data = line[0][1]
        data = ":".join("%02x" % ord(v) for v in data)
	iface_oid = line[0][0][10]
        if len(data) == 17:
          all_macs[iface_oid].append(data)
    except IndexError:
      continue

  logger.debug("SNMP MAC per Interface OID: %s", all_macs)
  return all_macs



def get_local_interfaces(host):
  local_ifaces = {}
  lines = snmpwalk(host , (1,3,6,1,2,1,2,2,1,2))

  for line in lines:
    data = str(line[0][1])
    if len(data) > 1 :
      index = line[0][0][-1]
      local_ifaces[data] = index

  logger.debug("SNMP Interface Walk: %s", local_ifaces)
  return local_ifaces



def get_local_mac_list(host):
  local_macs = []
  lines = snmpwalk ( host , (1,3,6,1,2,1,2,2,1,6))

  for line in lines:
    data = line[0][1]
    if len(str(data)) > 1:
      data = ":".join("%02x" % ord(v) for v in data) 
      local_macs.append(data)

  logger.debug("SNMP Local Interfaces: %s", local_macs)
  return local_macs



def oui_filter(mac):
  mac = mac.upper()
  blocked_oui = ('00:15:6D', 'Dummy')
  return not any([mac.startswith(x) for x in blocked_oui])



def main(host, checked_ifaces):
  try:
    local_macs = sorted(get_local_mac_list(host))
    local_ifaces = get_local_interfaces(host)
    all_macs = get_all_macs(host)
  except socket.gaierror as e:
    return ("Failed: SNMP for host cannot be queried - %s" % e, ERRNO.CRITICAL)
  except Exception as e:
    return ("Failed: Script Exception - [%s] %s" % (type(e),e), ERRNO.CRITICAL)

  if not local_ifaces or not local_macs or not all_macs:
    return ("Failed: No results", ERRNO.UNKNOWN)
  missing_ifaces = list(set(checked_ifaces) - set(local_ifaces.keys()))

  if missing_ifaces:
    return ("Failed: No results for %s (suggestions: %s)" % (missing_ifaces, local_ifaces.keys()), ERRNO.UNKNOWN)
  logger.debug("Interfaces available for checking: %s", checked_ifaces)

  # Process all interfaces and find out if their are still MACs found on the other side
  failed_ifaces = []
  for iface in checked_ifaces:
    filtered_macs = filter(oui_filter, sorted(all_macs[local_ifaces[iface]]))
    logger.debug("Availble MACs after filtering: %s", filtered_macs)

    # Remove Local MACs
    remote_macs = list(set(filtered_macs) - set(local_macs))

    if not remote_macs:
      failed_ifaces.append(iface)
       
  if failed_ifaces:
    return ("Failed: No remote MACs found for: %s" % failed_ifaces, ERRNO.CRITICAL)
   
  # Everything is happy
  if len(checked_ifaces) == 1:
    return ("OK: Interlink on %s is active" % checked_ifaces[0], ERRNO.OK)
  else:
    return ("OK: Interlinks on %s are active" % ','.join(checked_ifaces), ERRNO.OK)



if __name__ == '__main__':
  class NagiosArgumentParser(argparse.ArgumentParser):
    ''' Like exit code 128 on errors'''
    def error(self, message):
      self.print_usage(sys.stderr)
      self.exit(128, _('%s: error: %s\n') % (self.prog, message))

  parser = NagiosArgumentParser(
    description='Nagios Check InterLinks via SNMP.',
    formatter_class=argparse.ArgumentDefaultsHelpFormatter)

  parser.add_argument('-g', dest='debug', action='store_true', default=False, help="Set logging to debug")
  parser.add_argument('host', action='store', type=str, help="Hostname to use")
  parser.add_argument('ifaces', action='store', type=str, help="Interfaces", nargs='+')
  args = parser.parse_args()

  # Make the interfaces a valid list by combining the comma arguments into a list
  args.ifaces = sorted(reduce(operator.add, [x.split(',') for x in args.ifaces]))

  if args.debug:
    logger.setLevel(logging.DEBUG)

  (msg, errno) = main(args.host, args.ifaces)
  sys.stdout.write(msg + "\n")
  sys.exit(errno)