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nat.py
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nat.py
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#!/usr/bin/env python3
#
# Copyright (C) 2020-2023 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 jmespath
import json
import os
from sys import exit
from netifaces import interfaces
from vyos.base import Warning
from vyos.config import Config
from vyos.configdep import set_dependents, call_dependents
from vyos.template import render
from vyos.template import is_ip_network
from vyos.utils.kernel import check_kmod
from vyos.utils.dict import dict_search
from vyos.utils.dict import dict_search_args
from vyos.utils.process import cmd
from vyos.utils.process import run
from vyos.utils.network import is_addr_assigned
from vyos import ConfigError
from vyos import airbag
airbag.enable()
k_mod = ['nft_nat', 'nft_chain_nat']
nftables_nat_config = '/run/nftables_nat.conf'
nftables_static_nat_conf = '/run/nftables_static-nat-rules.nft'
valid_groups = [
'address_group',
'domain_group',
'network_group',
'port_group'
]
def get_config(config=None):
if config:
conf = config
else:
conf = Config()
base = ['nat']
nat = conf.get_config_dict(base, key_mangling=('-', '_'),
get_first_key=True,
with_recursive_defaults=True)
set_dependents('conntrack', conf)
if not conf.exists(base):
nat['deleted'] = ''
return nat
nat['firewall_group'] = conf.get_config_dict(['firewall', 'group'], key_mangling=('-', '_'), get_first_key=True,
no_tag_node_value_mangle=True)
return nat
def verify_rule(config, err_msg, groups_dict):
""" Common verify steps used for both source and destination NAT """
if (dict_search('translation.port', config) != None or
dict_search('translation.redirect.port', config) != None or
dict_search('destination.port', config) != None or
dict_search('source.port', config)):
if config['protocol'] not in ['tcp', 'udp', 'tcp_udp']:
raise ConfigError(f'{err_msg} ports can only be specified when '\
'protocol is either tcp, udp or tcp_udp!')
for side in ['destination', 'source']:
if side in config:
side_conf = config[side]
if len({'address', 'fqdn'} & set(side_conf)) > 1:
raise ConfigError('Only one of address, fqdn or geoip can be specified')
if 'group' in side_conf:
if len({'address_group', 'network_group', 'domain_group'} & set(side_conf['group'])) > 1:
raise ConfigError('Only one address-group, network-group or domain-group can be specified')
for group in valid_groups:
if group in side_conf['group']:
group_name = side_conf['group'][group]
error_group = group.replace("_", "-")
if group in ['address_group', 'network_group', 'domain_group']:
types = [t for t in ['address', 'fqdn'] if t in side_conf]
if types:
raise ConfigError(f'{error_group} and {types[0]} cannot both be defined')
if group_name and group_name[0] == '!':
group_name = group_name[1:]
group_obj = dict_search_args(groups_dict, group, group_name)
if group_obj is None:
raise ConfigError(f'Invalid {error_group} "{group_name}" on nat rule')
if not group_obj:
Warning(f'{error_group} "{group_name}" has no members!')
if dict_search_args(side_conf, 'group', 'port_group'):
if 'protocol' not in config:
raise ConfigError('Protocol must be defined if specifying a port-group')
if config['protocol'] not in ['tcp', 'udp', 'tcp_udp']:
raise ConfigError('Protocol must be tcp, udp, or tcp_udp when specifying a port-group')
if 'load_balance' in config:
for item in ['source-port', 'destination-port']:
if item in config['load_balance']['hash'] and config['protocol'] not in ['tcp', 'udp']:
raise ConfigError('Protocol must be tcp or udp when specifying hash ports')
count = 0
if 'backend' in config['load_balance']:
for member in config['load_balance']['backend']:
weight = config['load_balance']['backend'][member]['weight']
count = count + int(weight)
if count != 100:
Warning(f'Sum of weight for nat load balance rule is not 100. You may get unexpected behaviour')
def verify(nat):
if not nat or 'deleted' in nat:
# no need to verify the CLI as NAT is going to be deactivated
return None
if dict_search('source.rule', nat):
for rule, config in dict_search('source.rule', nat).items():
err_msg = f'Source NAT configuration error in rule {rule}:'
if 'outbound_interface' in config:
if 'name' in config['outbound_interface'] and 'group' in config['outbound_interface']:
raise ConfigError(f'{err_msg} cannot specify both interface group and interface name for nat source rule "{rule}"')
elif 'name' in config['outbound_interface']:
if config['outbound_interface']['name'] not in 'any' and config['outbound_interface']['name'] not in interfaces():
Warning(f'NAT interface "{config["outbound_interface"]["name"]}" for source NAT rule "{rule}" does not exist!')
if not dict_search('translation.address', config) and not dict_search('translation.port', config):
if 'exclude' not in config and 'backend' not in config['load_balance']:
raise ConfigError(f'{err_msg} translation requires address and/or port')
addr = dict_search('translation.address', config)
if addr != None and addr != 'masquerade' and not is_ip_network(addr):
for ip in addr.split('-'):
if not is_addr_assigned(ip):
Warning(f'IP address {ip} does not exist on the system!')
# common rule verification
verify_rule(config, err_msg, nat['firewall_group'])
if dict_search('destination.rule', nat):
for rule, config in dict_search('destination.rule', nat).items():
err_msg = f'Destination NAT configuration error in rule {rule}:'
if 'inbound_interface' in config:
if 'name' in config['inbound_interface'] and 'group' in config['inbound_interface']:
raise ConfigError(f'{err_msg} cannot specify both interface group and interface name for destination nat rule "{rule}"')
elif 'name' in config['inbound_interface']:
if config['inbound_interface']['name'] not in 'any' and config['inbound_interface']['name'] not in interfaces():
Warning(f'NAT interface "{config["inbound_interface"]["name"]}" for destination NAT rule "{rule}" does not exist!')
if not dict_search('translation.address', config) and not dict_search('translation.port', config) and 'redirect' not in config['translation']:
if 'exclude' not in config and 'backend' not in config['load_balance']:
raise ConfigError(f'{err_msg} translation requires address and/or port')
# common rule verification
verify_rule(config, err_msg, nat['firewall_group'])
if dict_search('static.rule', nat):
for rule, config in dict_search('static.rule', nat).items():
err_msg = f'Static NAT configuration error in rule {rule}:'
if 'inbound_interface' not in config:
raise ConfigError(f'{err_msg} inbound-interface not specified')
# common rule verification
verify_rule(config, err_msg, nat['firewall_group'])
return None
def generate(nat):
if not os.path.exists(nftables_nat_config):
nat['first_install'] = True
render(nftables_nat_config, 'firewall/nftables-nat.j2', nat)
render(nftables_static_nat_conf, 'firewall/nftables-static-nat.j2', nat)
# dry-run newly generated configuration
tmp = run(f'nft -c -f {nftables_nat_config}')
if tmp > 0:
raise ConfigError('Configuration file errors encountered!')
tmp = run(f'nft -c -f {nftables_static_nat_conf}')
if tmp > 0:
raise ConfigError('Configuration file errors encountered!')
return None
def apply(nat):
cmd(f'nft -f {nftables_nat_config}')
cmd(f'nft -f {nftables_static_nat_conf}')
if not nat or 'deleted' in nat:
os.unlink(nftables_nat_config)
os.unlink(nftables_static_nat_conf)
call_dependents()
return None
if __name__ == '__main__':
try:
check_kmod(k_mod)
c = get_config()
verify(c)
generate(c)
apply(c)
except ConfigError as e:
print(e)
exit(1)

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