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bcast_relay.py
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bcast_relay.py
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#!/usr/bin/env python3
#
# Copyright (C) 2017-2020 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 os
import fnmatch
from sys import exit
from copy import deepcopy
from vyos.config import Config
from vyos import ConfigError
from vyos.util import call
from vyos.template import render
from vyos import airbag
airbag.enable()
config_file = r'/etc/default/udp-broadcast-relay'
default_config_data = {
'disabled': False,
'instances': []
}
def get_config():
relay = deepcopy(default_config_data)
conf = Config()
base = ['service', 'broadcast-relay']
if not conf.exists(base):
return None
else:
conf.set_level(base)
# 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(base + ['id', 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'])
render(file, 'bcast-relay/udp-broadcast-relay.tmpl', r)
return None
def apply(relay):
# first stop all running services
call('systemctl stop udp-broadcast-relay@{1..99}.service')
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
call('systemctl start udp-broadcast-relay@{0}.service'.format(r['id']))
return None
if __name__ == '__main__':
try:
c = get_config()
verify(c)
generate(c)
apply(c)
except ConfigError as e:
print(e)
exit(1)

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