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dns_forwarding.py
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dns_forwarding.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 sys import exit
from copy import deepcopy
from vyos.config import Config
from vyos.hostsd_client import Client as hostsd_client
from vyos import ConfigError
from vyos.util import call
from vyos.template import render
from vyos import airbag
airbag.enable()
pdns_rec_run_dir = '/run/powerdns'
pdns_rec_lua_conf_file = f'{pdns_rec_run_dir}/recursor.conf.lua'
pdns_rec_hostsd_lua_conf_file = f'{pdns_rec_run_dir}/recursor.vyos-hostsd.conf.lua'
pdns_rec_hostsd_zones_file = f'{pdns_rec_run_dir}/recursor.forward-zones.conf'
pdns_rec_config_file = f'{pdns_rec_run_dir}/recursor.conf'
default_config_data = {
'allow_from': [],
'cache_size': 10000,
'export_hosts_file': 'yes',
'listen_address': [],
'name_servers': [],
'negative_ttl': 3600,
'system': False,
'domains': {},
'dnssec': 'process-no-validate',
'dhcp_interfaces': []
}
def get_config(conf):
dns = deepcopy(default_config_data)
base = ['service', 'dns', 'forwarding']
if not conf.exists(base):
return None
conf.set_level(base)
if conf.exists(['allow-from']):
dns['allow_from'] = conf.return_values(['allow-from'])
if conf.exists(['cache-size']):
cache_size = conf.return_value(['cache-size'])
dns['cache_size'] = cache_size
if conf.exists('negative-ttl'):
negative_ttl = conf.return_value(['negative-ttl'])
dns['negative_ttl'] = negative_ttl
if conf.exists(['domain']):
for domain in conf.list_nodes(['domain']):
conf.set_level(base + ['domain', domain])
entry = {
'nslist': bracketize_ipv6_addrs(conf.return_values(['server'])),
'addNTA': conf.exists(['addnta']),
'recursion-desired': conf.exists(['recursion-desired'])
}
dns['domains'][domain] = entry
conf.set_level(base)
if conf.exists(['ignore-hosts-file']):
dns['export_hosts_file'] = "no"
if conf.exists(['name-server']):
dns['name_servers'] = bracketize_ipv6_addrs(
conf.return_values(['name-server']))
if conf.exists(['system']):
dns['system'] = True
if conf.exists(['listen-address']):
dns['listen_address'] = conf.return_values(['listen-address'])
if conf.exists(['dnssec']):
dns['dnssec'] = conf.return_value(['dnssec'])
if conf.exists(['dhcp']):
dns['dhcp_interfaces'] = conf.return_values(['dhcp'])
return dns
def bracketize_ipv6_addrs(addrs):
"""Wraps each IPv6 addr in addrs in [], leaving IPv4 addrs untouched."""
return ['[{0}]'.format(a) if a.count(':') > 1 else a for a in addrs]
def verify(conf, dns):
# bail out early - looks like removal from running config
if dns is None:
return None
if not dns['listen_address']:
raise ConfigError(
"Error: DNS forwarding requires a listen-address")
if not dns['allow_from']:
raise ConfigError(
"Error: DNS forwarding requires an allow-from network")
if dns['domains']:
for domain in dns['domains']:
if not dns['domains'][domain]['nslist']:
raise ConfigError((
f'Error: No server configured for domain {domain}'))
no_system_nameservers = False
if dns['system'] and not (
conf.exists(['system', 'name-server']) or
conf.exists(['system', 'name-servers-dhcp']) ):
no_system_nameservers = True
print(("DNS forwarding warning: No 'system name-server' or "
"'system name-servers-dhcp' set\n"))
if (no_system_nameservers or not dns['system']) and not (
dns['name_servers'] or dns['dhcp_interfaces']):
print(("DNS forwarding warning: No 'dhcp', 'name-server' or 'system' "
"nameservers set. Forwarding will operate as a recursor.\n"))
return None
def generate(dns):
# bail out early - looks like removal from running config
if dns is None:
return None
render(config_file, 'dns-forwarding/recursor.conf.tmpl', dns, trim_blocks=True, user='pdns', group='pdns')
return None
def apply(dns):
if dns is None:
# DNS forwarding is removed in the commit
call("systemctl stop pdns-recursor.service")
if os.path.isfile(pdns_rec_config_file):
os.unlink(pdns_rec_config_file)
else:
call("systemctl restart pdns-recursor.service")
if __name__ == '__main__':
try:
conf = Config()
c = get_config(conf)
verify(conf, c)
generate(c)
apply(c)
except ConfigError as e:
print(e)
exit(1)

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