dns updater daemon

dnsupdsrv.py

#!/usr/bin/env python3

import datetime
import getpass
import ipaddress
import logging
import shutil
import subprocess
import sys
import socket
from P4 import P4, P4Exception

# v1.10 (2018.01.26) : initial version
# ./dnsupd_srv [-c configfile] [-l loglevel] [-?] [-v]


# showHelp() : shows the allowed switches server-side
def showHelp():
  print("dnsupdsrv.py [-c conf_file]")
  print("-c conf_file : read the config file 'conf_file'")
  print("-v: version")
  print("-?: this help")
  sys.exit(0)


# showVersion() : displays CHANGELOG & version info
def showVersion():
  print("dnsupdsrv.py")
  print("============")
  print("1.10 : 2018.01.26 -> added logging facility")
  print("1.00 : 2018.01.14 -> initial version")
  sys.exit(0)


# incrementSerial() : increment the DNS serial #
def incrementSerial(ligne):
  serialnum = int(ligne[-2:])
  cdate = datetime.date.today().strftime('%Y%m%d')
  if cdate != ligne[:8]:
    return cdate+'01'
  else:
    ++serialnum
    if serialnum<10:
      return ligne[:8]+'0'+str(serialnum)
    else:
      return ligne[:8]+str(serialnum)


# changeIPaddressInZone() modifies the serial # and the IP address in zonefile
def changeIPaddressInZone(logger, p4client, p4port, dnsfile, clientroot, newip):
	if p4client != '':
		p4 = P4()
		p4.client = p4client
		p4.port = p4port
		p4.connect()
		p4.run('sync', '-f', dnsfile)
		p4.run('edit', dnsfile)
	newzonefile = dnsfile.replace('//puppet/', clientroot + '/puppet/')
	try:
		with open(newzonefile, 'r') as infile:
			with open('/tmp/newfile', 'w') as outfile:
				for line in infile:
					if line.endswith('; serial'):
						line = incrementSerial(line) + '\t; serial'
					if line.startswith('oslo'):
						line = 'oslo\t\t\tIN\tA\t'+newip+'\n'
					outfile.write(line)
		shutil.move('/tmp/newfile', newzonefile)
	except OSError as x:
		logger.error('Exception: ' + int(x[0]) + ' => ' + x[1])

	if p4client !='':
		try:
			p4chg = p4.fetch_change()
			p4chg._description = 'DNSUPDATER: ' + str(datetime.datetime.now().strftime('%Y/%m/%d %H.%M.%S')) + ": " + newip
			p4chg._files = dnsfile
			p4.run_submit(p4chg)
		except P4Exception as p4x:
			logger.error('Perforce error: ' + p4.error)


# readConfigFile() : reads the various params to be used by the daemon
def readConfigFile(logger, configfile = '/opt/dnsupdater/server.conf'):
	logger.debug('Entering readConfigFile()')
	try:
		with open(configfile) as cfgf:
			for line in cfgf.readlines():
				if not line.startswith('#') and not line.startswith(' ') and not line.startswith('\n'):
					if line.startswith('bindport: '):
						bindport = int(line.rsplit(' ', 1)[1].strip('\n'))
						logger.debug('bindport: ' + str(bindport))
					if line.startswith('p4user: '):
						p4user = line.rsplit(' ', 1)[1].strip('\n')
						logger.debug('Perforce user: ' + p4user)
					if line.startswith('p4client: '):
						p4client = line.rsplit(' ', 1)[1].strip('\n')
						logger.debug('Perforce workspace (p4client): '+ p4client)
					if line.startswith('p4port: '):
						p4port = line.rsplit(' ', 1)[1].strip('\n')
						logger.debug('Perforce server: ' + p4port)
					if line.startswith('dnsfile: '):
						dnsfile = line.rsplit(' ', 1)[1].strip('\n')
						logger.debug('P4 path to zone file (dnsfile): ' + dnsfile)
					if line.startswith('clientroot: '):
						clientroot = line.rsplit(' ', 1)[1].strip('\n')
						logger.debug('P4 client workspace depot root: ' + clientroot)
					if line.startswith('loglevel: '):
						loglevel = int(line.rsplit(' ', 1)[1].strip('\n'))
						logger.debug('log level: ' + str(loglevel))
						if loglevel < 1 or loglevel > 5:
							loglevel = 3
						logger.setLevel(loglevel * 10)
		logger.info('Successfully read ' + configfile)
	except OSError as msg:
		logger.error('Error with file' + configfile + '. Error code = ' + str(msg[0]) + ':' + msg[1])

	logger.debug('Leaving readConfigFile()')


def main():
	# check who is running this script ? (only devops is allowed)
	##if getpass.getuser()!='devops':
	##	print("This must be run by user 'devops'")
	##	sys.exit(-1)

	# Overridden variables
	configfile = newip = p4client = ''
	clientroot='/repos'
	bindport = 2009
	loglevel = 3
	dnsfile = '//puppet/code/environments/production/modules/dns/files/famillegratton.net.zone'
	p4port='perforce.cloud.famillegratton.net:1818'
	shutdown = False

	# Set logging facilities (https://docs.python.org/2.3/lib/node304.html)
	# Logging levels : 0 = NOTSET, 10 = DEBUG, 20 = INFO, 30 = WARNING, 40 = ERROR, 50 = CRITICAL
	logger = logging.getLogger(__name__)
	lgf = logging.FileHandler('/var/log/dnsupdater/dnsupdater.log')
	lgfformat = logging.Formatter('%(asctime)s %(levelname)s %(message)s', datefmt='%Y.%m.%d %H:%M:%S')
	lgf.setFormatter(lgfformat)
	logger.addHandler(lgf)
	logger.setLevel(logging.INFO)
	logger.info('=====================')
	logger.info('MARK MARK MARK')
	logger.info('=====================')
	logger.info('===> Daemon startup')

	# Parse command line
	if '-c' in sys.argv and len(sys.argv) - sys.argv.index('-c') >= 2:
		configfile = sys.argv[sys.argv.index('-c') + 1]
	if '-?' in sys.argv or '-h' in sys.argv:
		showHelp()
	if '-v' in sys.argv:
		showVersion()
	if '-l' in sys.argv and len(sys.argv) - sys.argv.index('-l') >= 2:
		loglevel = int(sys.argv.index('-l')) + 1
		if loglevel < 1 or loglevel > 5:
			loglevel = 3

	# Set logging level past logfile header
	# (ie: we wanted a startup message in the logfile, now we log according to config)
	logger.setLevel(loglevel * 10)

	readConfigFile(logger, configfile)

	s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	try:
		logger.debug('binding on port ' + str(bindport))
		s.bind(('', bindport))
	except socket.error as msg:
		logger.error('Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1])
		sys.exit()

	# Start listening on socket
	logger.debug('listening.....')
	s.listen(1)

	# now keep talking with the client
	while 1:
		connection, client_address = s.accept()
		source = client_address[0] + ' tcp/' + str(client_address[1])
		logger.info('Connection from ' + source)
		try:
			while True:
				data = connection.recv(256)
				if not data:
					break

		finally:
			logger.info('Closing connection from ' + source)
			connection.close()

		recv = str(data)
		if recv.endswith('<-Q'):
			logger.warning('Received daemon shutdown request from' + source)
			recv=recv[:-3]
			shutdown = True

		try:
			newip = ipaddress.ip_address(recv)
		except ValueError:
			newip=''

		if newip != '':
			changeIPaddressInZone(logger, p4client, p4port, dnsfile, clientroot, newip)
			with open('/var/log/dnsupdater/ip.log', 'a') as logfile:
				try:
					logfile.write(datetime.datetime.now().strftime('%Y/%m/%d %H.%M.%S') + ': ' + newip)
				except OSError as msg:
					logger.warning('Unable to write /var/log/dnsupdater/ip.log : ' + msg[1])

			subprocess.call('systemctl reload named')

		if shutdown == True:
			logger.info('---> Daemon is shutting down')
			sys.exit(1)

if __name__ == '__main__':
	main()