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dhcp_server.py
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dhcp_server.py
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#!/usr/bin/env python3
#
# Copyright (C) 2018-2020 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
from ipaddress import ip_address
from ipaddress import ip_network
from sys import exit
from vyos.config import Config
from vyos.configdict import dict_merge
from vyos.template import render
from vyos.util import call
from vyos.util import dict_search
from vyos.validate import is_subnet_connected
from vyos.xml import defaults
from vyos import ConfigError
from vyos import airbag
airbag.enable()
config_file = '/run/dhcp-server/dhcpd.conf'
def dhcp_slice_range(exclude_list, range_list):
"""
This function is intended to slice a DHCP range. What does it mean?
Lets assume we have a DHCP range from '192.0.2.1' to '192.0.2.100'
but want to exclude address '192.0.2.74' and '192.0.2.75'. We will
pass an input 'range_list' in the format:
[{'start' : '192.0.2.1', 'stop' : '192.0.2.100' }]
and we will receive an output list of:
[{'start' : '192.0.2.1' , 'stop' : '192.0.2.73' },
{'start' : '192.0.2.76', 'stop' : '192.0.2.100' }]
The resulting list can then be used in turn to build the proper dhcpd
configuration file.
"""
output = []
# exclude list must be sorted for this to work
exclude_list = sorted(exclude_list)
for ra in range_list:
range_start = ra['start']
range_stop = ra['stop']
range_last_exclude = ''
for e in exclude_list:
if (ip_address(e) >= ip_address(range_start)) and \
(ip_address(e) <= ip_address(range_stop)):
range_last_exclude = e
for e in exclude_list:
if (ip_address(e) >= ip_address(range_start)) and \
(ip_address(e) <= ip_address(range_stop)):
# Build new IP address range ending one IP address before exclude address
r = {
'start' : range_start,
'stop' : str(ip_address(e) -1)
}
# On the next run our IP address range will start one address after the exclude address
range_start = str(ip_address(e) + 1)
# on subsequent exclude addresses we can not
# append them to our output
if not (ip_address(r['start']) > ip_address(r['stop'])):
# Everything is fine, add range to result
output.append(r)
# Take care of last IP address range spanning from the last exclude
# address (+1) to the end of the initial configured range
if ip_address(e) == ip_address(range_last_exclude):
r = {
'start': str(ip_address(e) + 1),
'stop': str(range_stop)
}
if not (ip_address(r['start']) > ip_address(r['stop'])):
output.append(r)
else:
# if we have no exclude in the whole range - we just take the range
# as it is
if not range_last_exclude:
if ra not in output:
output.append(ra)
return output
def get_config(config=None):
if config:
conf = config
else:
conf = Config()
base = ['service', 'dhcp-server']
if not conf.exists(base):
return None
dhcp = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)
# T2665: defaults include lease time per TAG node which need to be added to
# individual subnet definitions
default_values = defaults(base + ['shared-network-name', 'subnet'])
for network, network_config in (dict_search('shared_network_name', dhcp).items() or {}):
print(network)
for subnet, subnet_config in (dict_search('subnet', network_config).items() or {}):
if 'lease' not in subnet_config:
dhcp['shared_network_name'][network]['subnet'][subnet] = dict_merge(
default_values, dhcp['shared_network_name'][network]['subnet'][subnet])
return dhcp
def verify(dhcp):
# bail out early - looks like removal from running config
if not dhcp or 'disable' in dhcp:
return None
# If DHCP is enabled we need one share-network
if 'shared_network_name' not in dhcp:
raise ConfigError('No DHCP shared networks configured.\n' \
'At least one DHCP shared network must be configured.')
# Inspect shared-network/subnet
failover_names = []
listen_ok = False
subnets = []
# A shared-network requires a subnet definition
for network, network_config in dhcp['shared_network_name'].items():
if 'subnet' not in network_config:
raise ConfigError(f'No subnets defined for {network}. At least one\n' \
'lease subnet must be configured.')
for subnet, subnet_config in network_config['subnet'].items():
if 'static_route' in subnet_config and len(subnet_config['static_route']) != 2:
raise ConfigError('Missing DHCP static-route parameter(s):\n' \
'destination-subnet | router must be defined!')
# Check if DHCP address range is inside configured subnet declaration
if 'range' in subnet_config:
range_start = []
range_stop = []
for range, range_config in subnet_config['range'].items():
if not {'start', 'stop'} <= set(range_config):
raise ConfigError(f'DHCP range "{range}" start and stop address must be defined!')
# Start/Stop address must be inside network
for key in ['start', 'stop']:
if ip_address(range_config[key]) not in ip_network(subnet):
raise ConfigError(f'DHCP range "{range}" {key} address not within shared-network "{network}, {subnet}"!')
# Stop address must be greater or equal to start address
if ip_address(range_config['stop']) < ip_address(range_config['start']):
raise ConfigError(f'DHCP range "{range}" stop address must be greater or equal\n' \
'to the ranges start address!')
# Range start address must be unique
if range_config['start'] in range_start:
raise ConfigError('Conflicting DHCP lease range: Pool start\n' \
'address "{start}" defined multipe times!'.format(range_config))
# Range stop address must be unique
if range_config['stop'] in range_start:
raise ConfigError('Conflicting DHCP lease range: Pool stop\n' \
'address "{stop}" defined multipe times!'.format(range_config))
range_start.append(range_config['start'])
range_stop.append(range_config['stop'])
if 'failover' in subnet_config:
for key in ['local_address', 'peer_address', 'name', 'status']:
if key not in subnet_config['failover']:
raise ConfigError(f'Missing DHCP failover parameter "{key}"!')
# Failover names must be uniquie
if subnet_config['failover']['name'] in failover_names:
name = subnet_config['failover']['name']
raise ConfigError(f'DHCP failover names must be unique:\n' \
f'{name} has already been configured!')
failover_names.append(subnet_config['failover']['name'])
# Failover requires start/stop ranges for pool
if 'range' not in subnet_config:
raise ConfigError(f'DHCP failover requires at least one start-stop range to be configured\n'\
f'within shared-network "{network}, {subnet}" for using failover!')
# Exclude addresses must be in bound
if 'exclude' in subnet_config:
for exclude in subnet_config['exclude']:
if ip_address(exclude) not in ip_network(subnet):
raise ConfigError(f'Excluded IP address "{exclude}" not within shared-network "{network}, {subnet}"!')
# At least one DHCP address range or static-mapping required
if 'range' not in subnet_config and 'static_mapping' not in subnet_config:
raise ConfigError(f'No DHCP address range or active static-mapping configured\n' \
f'within shared-network "{network}, {subnet}"!')
if 'static_mapping' in subnet_config:
# Static mappings require just a MAC address (will use an IP from the dynamic pool if IP is not set)
for mapping, mapping_config in subnet_config['static_mapping'].items():
if 'ip_address' in mapping_config:
if ip_address(mapping_config['ip_address']) not in ip_network(subnet):
raise ConfigError(f'Configured static lease address for mapping "{mapping}" is\n' \
f'not within shared-network "{network}, {subnet}"!')
if 'mac_address' not in mapping_config:
raise ConfigError(f'MAC address required for static mapping "{mapping}"\n' \
f'within shared-network "{network}, {subnet}"!')
# There must be one subnet connected to a listen interface.
# This only counts if the network itself is not disabled!
if 'disable' not in network_config:
if is_subnet_connected(subnet, primary=True):
listen_ok = True
# Subnets must be non overlapping
if subnet in subnets:
raise ConfigError(f'Configured subnets must be unique! Subnet "{subnet}"\n'
'defined multiple times!')
subnets.append(subnet)
# Check for overlapping subnets
net = ip_network(subnet)
for n in subnets:
net2 = ip_network(n)
if (net != net2):
if net.overlaps(net2):
raise ConfigError('Conflicting subnet ranges: "{net}" overlaps "{net2}"!')
if not listen_ok:
raise ConfigError('DHCP server configuration error! None of the configured\n' \
'subnets have an appropriate primary IP address on any\n'
'broadcast interface.')
return None
def generate(dhcp):
# bail out early - looks like removal from running config
if not dhcp or 'disable' in dhcp:
return None
# Please see: https://phabricator.vyos.net/T1129 for quoting of the raw parameters
# we can pass to ISC DHCPd
render(config_file, 'dhcp-server/dhcpd.conf.tmpl', dhcp,
formater=lambda _: _.replace("&quot;", '"'))
return None
def apply(dhcp):
# bail out early - looks like removal from running config
if not dhcp or 'disable' in dhcp:
call('systemctl stop isc-dhcp-server.service')
if os.path.exists(config_file):
os.unlink(config_file)
return None
call('systemctl restart isc-dhcp-server.service')
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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