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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 argparse
import jinja2
import netifaces
import vyos.util
import vyos.hostsd_client
from vyos.config import Config
from vyos import ConfigError
parser = argparse.ArgumentParser()
parser.add_argument("--dhclient", action="store_true",
help="Started from dhclient-script")
config_file = r'/etc/powerdns/recursor.conf'
# XXX: pdns recursor doesn't like whitespace near entry separators,
# especially in the semicolon-separated lists of name servers.
# Please be careful if you edit the template.
config_tmpl = """
### Autogenerated by dns_forwarding.py ###
# Non-configurable defaults
daemon=yes
threads=1
allow-from={{ allow_from | join(',') }}
log-common-errors=yes
non-local-bind=yes
query-local-address=0.0.0.0
query-local-address6=::
# cache-size
max-cache-entries={{ cache_size }}
# negative TTL for NXDOMAIN
max-negative-ttl={{ negative_ttl }}
# ignore-hosts-file
export-etc-hosts={{ export_hosts_file }}
# listen-on
local-address={{ listen_on | join(',') }}
# dnssec
dnssec={{ dnssec }}
# forward-zones / recursion
#
# statement is only inserted if either one forwarding domain or nameserver is configured
# if nothing is given at all, powerdns will act as a real recursor and resolve all requests by its own
#
{% if name_servers or domains %}forward-zones-recurse=
{%- for d in domains %}
{{ d.name }}={{ d.servers | join(";") }}
{{- ", " if not loop.last -}}
{%- endfor -%}
{%- if name_servers -%}
{%- if domains -%}, {% endif -%}.={{ name_servers | join(';') }}
{% endif %}
{% endif %}
"""
default_config_data = {
'allow_from': [],
'cache_size': 10000,
'export_hosts_file': 'yes',
'listen_on': [],
'name_servers': [],
'negative_ttl': 3600,
'domains': [],
'dnssec': 'process-no-validate'
}
def get_config(arguments):
dns = default_config_data
conf = Config()
if arguments.dhclient:
conf.exists = conf.exists_effective
conf.return_value = conf.return_effective_value
conf.return_values = conf.return_effective_values
if not conf.exists('service dns forwarding'):
return None
conf.set_level('service dns forwarding')
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 node in conf.list_nodes('domain'):
servers = conf.return_values("domain {0} server".format(node))
domain = {
"name": node,
"servers": bracketize_ipv6_addrs(servers)
}
dns['domains'].append(domain)
if conf.exists('ignore-hosts-file'):
dns['export_hosts_file'] = "no"
if conf.exists('name-server'):
name_servers = conf.return_values('name-server')
dns['name_servers'] = dns['name_servers'] + name_servers
if conf.exists('system'):
conf.set_level('system')
system_name_servers = []
system_name_servers = conf.return_values('name-server')
if not system_name_servers:
print(
"DNS forwarding warning: No name-servers set under 'system name-server'\n")
else:
dns['name_servers'] = dns['name_servers'] + system_name_servers
conf.set_level('service dns forwarding')
dns['name_servers'] = bracketize_ipv6_addrs(dns['name_servers'])
if conf.exists('listen-address'):
dns['listen_on'] = conf.return_values('listen-address')
if conf.exists('dnssec'):
dns['dnssec'] = conf.return_value('dnssec')
# Add name servers received from DHCP
if conf.exists('dhcp'):
interfaces = []
interfaces = conf.return_values('dhcp')
hc = vyos.hostsd_client.Client()
for interface in interfaces:
dhcp_resolvers = hc.get_name_servers("dhcp-{0}".format(interface))
dhcpv6_resolvers = hc.get_name_servers("dhcpv6-{0}".format(interface))
if dhcp_resolvers:
dns['name_servers'] = dns['name_servers'] + dhcp_resolvers
if dhcpv6_resolvers:
dns['name_servers'] = dns['name_servers'] + dhcpv6_resolvers
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(dns):
# bail out early - looks like removal from running config
if dns is None:
return None
if not dns['listen_on']:
raise ConfigError(
"Error: DNS forwarding requires either a listen-address (preferred) or a listen-on option")
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 domain['servers']:
raise ConfigError(
'Error: No server configured for domain {0}'.format(domain['name']))
return None
def generate(dns):
# bail out early - looks like removal from running config
if dns is None:
return None
tmpl = jinja2.Template(config_tmpl, trim_blocks=True)
config_text = tmpl.render(dns)
with open(config_file, 'w') as f:
f.write(config_text)
return None
def apply(dns):
if dns is None:
# DNS forwarding is removed in the commit
os.system("systemctl stop pdns-recursor")
if os.path.isfile(config_file):
os.unlink(config_file)
else:
os.system("systemctl restart pdns-recursor")
if __name__ == '__main__':
args = parser.parse_args()
if args.dhclient:
# There's a big chance it was triggered by a commit still in progress
# so we need to wait until the new values are in the running config
vyos.util.wait_for_commit_lock()
try:
c = get_config(args)
verify(c)
generate(c)
apply(c)
except ConfigError as e:
print(e)
sys.exit(1)
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