bcast_relay.py
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	#!/usr/bin/env python3
	#
	# Copyright (C) 2017 VyOS maintainers and contributors
	#
	# This program is free software; you can redistribute it and/or modify
	# it under the terms of the GNU General Public License version 2 or later as
	# published by the Free Software Foundation.
	#
	# This program is distributed in the hope that it will be useful,
	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	# GNU General Public License for more details.
	#
	# You should have received a copy of the GNU General Public License
	# along with this program. If not, see <http://www.gnu.org/licenses/>.
	#
	#

	import sys
	import os
	import fnmatch
	import jinja2

	from vyos.config import Config
	from vyos import ConfigError

	config_file = r'/etc/default/udp-broadcast-relay'

	config_tmpl = """
	### Autogenerated by bcast_relay.py ###

	# UDP broadcast relay configuration for instance {{ id }}
	{%- if description %}
	# Comment: {{ description }}
	{% endif %}
	DAEMON_ARGS="{% if address %}-s {{ address }} {% endif %}{{ id }} {{ port }} {{ interfaces \| join(' ') }}"

	"""

	default_config_data = {
	'disabled': False,
	'instances': []
	}

	def get_config():
	relay = default_config_data
	conf = Config()
	if not conf.exists('service broadcast-relay'):
	return None
	else:
	conf.set_level('service broadcast-relay')

	# Service can be disabled by user
	if conf.exists('disable'):
	relay['disabled'] = True
	return relay

	# Parse configuration of each individual instance
	if conf.exists('id'):
	for id in conf.list_nodes('id'):
	conf.set_level('service broadcast-relay id {0}'.format(id))
	config = {
	'id': id,
	'disabled': False,
	'address': '',
	'description': '',
	'interfaces': [],
	'port': ''
	}

	# Check if individual broadcast relay service is disabled
	if conf.exists('disable'):
	config['disabled'] = True

	# Source IP of forwarded packets, if empty original senders address is used
	if conf.exists('address'):
	config['address'] = conf.return_value('address')

	# A description for each individual broadcast relay service
	if conf.exists('description'):
	config['description'] = conf.return_value('description')

	# UDP port to listen on for broadcast frames
	if conf.exists('port'):
	config['port'] = conf.return_value('port')

	# Network interfaces to listen on for broadcast frames to be relayed
	if conf.exists('interface'):
	config['interfaces'] = conf.return_values('interface')

	relay['instances'].append(config)

	return relay

	def verify(relay):
	if relay is None:
	return None

	if relay['disabled']:
	return None

	for r in relay['instances']:
	# we don't have to check this instance when it's disabled
	if r['disabled']:
	continue

	# we certainly require a UDP port to listen to
	if not r['port']:
	raise ConfigError('UDP broadcast relay "{0}" requires a port number'.format(r['id']))

	# Relaying data without two interface is kinda senseless ...
	if len(r['interfaces']) < 2:
	raise ConfigError('UDP broadcast relay "id {0}" requires at least 2 interfaces'.format(r['id']))

	return None


	def generate(relay):
	if relay is None:
	return None

	config_dir = os.path.dirname(config_file)
	config_filename = os.path.basename(config_file)
	active_configs = []

	for config in fnmatch.filter(os.listdir(config_dir), config_filename + '*'):
	# determine prefix length to identify service instance
	prefix_len = len(config_filename)
	active_configs.append(config[prefix_len:])

	# sort our list
	active_configs.sort()

	# delete old configuration files
	for id in active_configs[:]:
	if os.path.exists(config_file + id):
	os.unlink(config_file + id)

	# If the service is disabled, we can bail out here
	if relay['disabled']:
	print('Warning: UDP broadcast relay service will be deactivated because it is disabled')
	return None

	for r in relay['instances']:
	# Skip writing instance config when it's disabled
	if r['disabled']:
	continue

	# configuration filename contains instance id
	file = config_file + str(r['id'])
	tmpl = jinja2.Template(config_tmpl)
	config_text = tmpl.render(r)
	with open(file, 'w') as f:
	f.write(config_text)

	return None

	def apply(relay):
	# first stop all running services
	os.system('sudo systemctl stop udp-broadcast-relay@{1..99}')

	if (relay is None) or relay['disabled']:
	return None

	# start only required service instances
	for r in relay['instances']:
	# Don't start individual instance when it's disabled
	if r['disabled']:
	continue
	os.system('sudo systemctl start udp-broadcast-relay@{0}'.format(r['id']))

	return None

	if __name__ == '__main__':
	try:
	c = get_config()
	verify(c)
	generate(c)
	apply(c)
	except ConfigError as e:
	print(e)
	sys.exit(1)

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