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vyos-config-dns-forwarding.py
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vyos-config-dns-forwarding.py
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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 time
from vyos.config import Config
from vyos.util import ConfigError
config_file = r'/etc/dnsmasq.d/vyos.conf'
# borrowed from: https://github.com/donjajo/py-world/blob/master/resolvconfReader.py, THX!
def get_resolvers(file):
resolvers = []
try:
with open(file, 'r') as resolvconf:
for line in resolvconf.readlines():
line = line.split('#',1)[0];
line = line.rstrip();
if 'nameserver' in line:
resolvers.append(line.split()[1])
return resolvers
except IOError as error:
return error.strerror
def get_config():
dns = {}
conf = Config()
conf.set_level('service dns forwarding')
if not conf.exists(''):
return dns
if conf.exists('cache-size'):
cache = conf.return_value('cache-size')
dns.setdefault('cache-size', cache)
if conf.exists('dhcp'):
dns.setdefault('dhcp', [])
interfaces = []
interfaces = conf.return_values('dhcp')
for interface in interfaces:
resolvers = get_resolvers("/etc/resolv.conf.dhclient-new-{0}".format(interface))
dhcp = {
"interface": interface,
"resolvers": resolvers
}
dns['dhcp'].append(dhcp)
if conf.exists('domain'):
dns.setdefault('domain', [])
for node in conf.list_nodes('domain'):
server = conf.return_value("domain {0} server".format(node))
domain = {
"name": node,
"server": server
}
dns['domain'].append(domain)
if conf.exists('ignore-hosts-file'):
dns.setdefault('ignore-hosts-file', True)
if conf.exists('listen-on'):
interfaces = []
interfaces = conf.return_values('listen-on')
dns.setdefault('listen-on', interfaces)
if conf.exists('name-server'):
nameservers = []
nameservers = conf.return_values('name-server')
dns.setdefault('name-server', nameservers)
if conf.exists('system'):
conf.set_level('system')
nameservers = []
nameservers = conf.return_values('name-server')
if len(nameservers) == 0:
print("DNS forwarding warning: No name-servers set under 'system name-server'\n")
dns.setdefault('system-name-server', True)
return dns
def verify(dns):
if 'listen-on' not in dns.keys():
raise ConfigError("Error: DNS forwarding requires a configured listen interface!")
return None
def generate(dns):
config_header = '### Autogenerated by vyos-config-dns-forwarding.py on {tm} ###\n'.format(tm=time.strftime("%a, %d %b %Y %H:%M:%S", time.localtime()))
# write new configuration file
f = open(config_file, 'w')
f.write(config_header)
f.write("log-facility=/var/log/dnsmasq.log\n")
f.write("no-poll\n")
f.write("edns-packet-max=4096\n")
f.write("bind-interfaces\n")
if 'listen-on' in dns.keys():
for interface in dns['listen-on']:
f.write("interface={0}\n".format(interface))
if 'dhcp' in dns.keys():
for dhcp in dns['dhcp']:
for resolver in dhcp['resolvers']:
f.write("server={0}\t# dhcp {1}\n".format(resolver, dhcp['interface']))
if 'domain' in dns.keys():
for domain in dns['domain']:
f.write("server=/{0}/{1}\t# domain-override\n".format(domain['name'], domain['server']))
if 'cache-size' in dns.keys():
f.write("cache-size={0}\n".format(dns['cache-size']))
if 'ignore-hosts-file' in dns.keys():
f.write("no-hosts\n")
if 'name-server' in dns.keys():
for nameserver in dns['name-server']:
f.write("server={0}\t# statically configured\n".format(nameserver))
if 'system-name-server' in dns.keys():
# Read the IP addresses of the upstream nameservers from /etc/resolv.conf
f.write("resolv-file=/etc/resolv.conf\n")
f.close()
return None
def apply(dns):
if len(dns) == 0:
cmd = "sudo systemctl stop dnsmasq"
else:
cmd = "sudo systemctl restart dnsmasq"
os.system(cmd)
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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