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#!/usr/bin/env python3
#
# Copyright (C) 2018 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 jinja2
from vyos.config import Config
from vyos import ConfigError
config_file = r'/etc/default/isc-dhcp-relay'
# Please be careful if you edit the template.
config_tmpl = """
### Autogenerated by dhcp_relay.py ###
# Defaults for isc-dhcp-relay initscript
# sourced by /etc/init.d/isc-dhcp-relay
#
# This is a POSIX shell fragment
#
# What servers should the DHCP relay forward requests to?
SERVERS="{{ server | join(' ') }}"
# On what interfaces should the DHCP relay (dhrelay) serve DHCP requests?
INTERFACES="{{ interface | join(' ') }}"
# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-4 -p {{ port }} {{ options | join(' ') }}"
"""
default_config_data = {
'interface': [],
'server': [],
'options': [],
'port': '67',
'hop_count': '10',
'relay_agent_packets': 'forward'
}
def get_config():
relay = default_config_data
conf = Config()
if not conf.exists('service dhcp-relay'):
return None
else:
conf.set_level('service dhcp-relay')
# Network interfaces to listen on
if conf.exists('interface'):
relay['interface'] = conf.return_values('interface')
# Servers equal to the address of the DHCP server(s)
if conf.exists('server'):
relay['server'] = conf.return_values('server')
conf.set_level('service dhcp-relay relay-options')
if conf.exists('hop-count'):
count = '-c ' + conf.return_value('hop-count')
relay['options'].append(count)
# Specify the maximum packet size to send to a DHCPv4/BOOTP server.
# This might be done to allow sufficient space for addition of relay agent
# options while still fitting into the Ethernet MTU size.
#
# Available in DHCPv4 mode only:
if conf.exists('max-size'):
size = '-A ' + conf.return_value('max-size')
relay['options'].append(size)
# Listen and transmit on port <xy>. This is mostly useful for debugging
# purposes. Default is port 67 for DHCPv4/BOOTP, or port 547 for DHCPv6.
if conf.exists('port'):
relay['port'] = conf.return_value('port')
# Control the handling of incoming DHCPv4 packets which already contain
# relay agent options. If such a packet does not have giaddr set in its
# header, the DHCP standard requires that the packet be discarded. However,
# if giaddr is set, the relay agent may handle the situation in four ways:
# It may append its own set of relay options to the packet, leaving the
# supplied option field intact; it may replace the existing agent option
# field; it may forward the packet unchanged; or, it may discard it.
#
# Available in DHCPv4 mode only:
if conf.exists('relay-agents-packets'):
pkt = '-m ' + conf.return_value('relay-agents-packets')
relay['options'].append(pkt)
return relay
def verify(relay):
# bail out early - looks like removal from running config
if relay is None:
return None
if len(relay['interface']) < 2:
# We can only issue a warning otherwise old configurations might break
print('WARNING: At least two interfaces are required for DHCP relay\n' \
'to work\n')
if 'lo' in relay['interface']:
raise ConfigError('DHCP relay does not support the loopback interface.')
if len(relay['server']) == 0:
raise ConfigError('No DHCP relay server(s) configured.\n' \
'At least one DHCP relay server required.')
return None
def generate(relay):
# bail out early - looks like removal from running config
if relay is None:
return None
tmpl = jinja2.Template(config_tmpl)
config_text = tmpl.render(relay)
with open(config_file, 'w') as f:
f.write(config_text)
return None
def apply(relay):
if relay is not None:
os.system('sudo systemctl restart isc-dhcp-relay.service')
else:
# DHCP relay support is removed in the commit
os.system('sudo systemctl stop isc-dhcp-relay.service')
os.unlink(config_file)
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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