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nat66.py
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nat66.py
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#!/usr/bin/env python3
#
# Copyright (C) 2020-2021 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.config import Config
from vyos.configdict import dict_merge
from vyos.template import render
from vyos.util import cmd
from vyos.util import check_kmod
from vyos.util import dict_search
from vyos.template import is_ipv6
from vyos.xml import defaults
from vyos import ConfigError
from vyos import airbag
airbag.enable()
k_mod = ['nft_nat', 'nft_chain_nat']
iptables_nat_config = '/tmp/vyos-nat66-rules.nft'
ndppd_config = '/run/ndppd/ndppd.conf'
def get_handler(json, chain, target):
""" Get nftable rule handler number of given chain/target combination.
Handler is required when adding NAT66/Conntrack helper targets """
for x in json:
if x['chain'] != chain:
continue
if x['target'] != target:
continue
return x['handle']
return None
def get_config(config=None):
if config:
conf = config
else:
conf = Config()
base = ['nat66']
nat = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)
# T2665: we must add the tagNode defaults individually until this is
# moved to the base class
for direction in ['source', 'destination']:
if direction in nat:
default_values = defaults(base + [direction, 'rule'])
if 'rule' in nat[direction]:
for rule in nat[direction]['rule']:
nat[direction]['rule'][rule] = dict_merge(default_values,
nat[direction]['rule'][rule])
# read in current nftable (once) for further processing
tmp = cmd('nft -j list table ip6 raw')
nftable_json = json.loads(tmp)
# condense the full JSON table into a list with only relevand informations
pattern = 'nftables[?rule].rule[?expr[].jump].{chain: chain, handle: handle, target: expr[].jump.target | [0]}'
condensed_json = jmespath.search(pattern, nftable_json)
if not conf.exists(base):
nat['helper_functions'] = 'remove'
nat['pre_ct_ignore'] = get_handler(condensed_json, 'PREROUTING', 'VYATTA_CT_HELPER')
nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'NAT_CONNTRACK')
nat['out_ct_ignore'] = get_handler(condensed_json, 'OUTPUT', 'VYATTA_CT_HELPER')
nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT', 'NAT_CONNTRACK')
nat['deleted'] = ''
return nat
# check if NAT66 connection tracking helpers need to be set up - this has to
# be done only once
if not get_handler(condensed_json, 'PREROUTING', 'NAT_CONNTRACK'):
nat['helper_functions'] = 'add'
# Retrieve current table handler positions
nat['pre_ct_ignore'] = get_handler(condensed_json, 'PREROUTING', 'VYATTA_CT_IGNORE')
nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'VYATTA_CT_PREROUTING_HOOK')
nat['out_ct_ignore'] = get_handler(condensed_json, 'OUTPUT', 'VYATTA_CT_IGNORE')
nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT', 'VYATTA_CT_OUTPUT_HOOK')
else:
nat['helper_functions'] = 'has'
return nat
def verify(nat):
if not nat or 'deleted' in nat:
# no need to verify the CLI as NAT66 is going to be deactivated
return None
if 'helper_functions' in nat and nat['helper_functions'] != 'has':
if not (nat['pre_ct_conntrack'] or nat['out_ct_conntrack']):
raise Exception('could not determine nftable ruleset handlers')
if dict_search('source.rule', nat):
for rule, config in dict_search('source.rule', nat).items():
err_msg = f'Source NAT66 configuration error in rule {rule}:'
if 'outbound_interface' not in config:
raise ConfigError(f'{err_msg}\n' \
'outbound-interface not specified')
else:
if config['outbound_interface'] not in interfaces():
print(f'WARNING: rule "{rule}" interface "{config["outbound_interface"]}" does not exist on this system')
addr = dict_search('translation.address', config)
if addr != None:
if addr != 'masquerade' and not is_ipv6(addr):
raise ConfigError(f'Warning: IPv6 address {addr} is not a valid address')
else:
raise ConfigError(f'{err_msg} translation address not specified')
prefix = dict_search('source.prefix', config)
if prefix != None:
if not is_ipv6(prefix):
raise ConfigError(f'{err_msg} source-prefix not specified')
if dict_search('destination.rule', nat):
for rule, config in dict_search('destination.rule', nat).items():
err_msg = f'Destination NAT66 configuration error in rule {rule}:'
if 'inbound_interface' not in config:
raise ConfigError(f'{err_msg}\n' \
'inbound-interface not specified')
else:
if config['inbound_interface'] not in 'any' and config['inbound_interface'] not in interfaces():
print(f'WARNING: rule "{rule}" interface "{config["inbound_interface"]}" does not exist on this system')
return None
def generate(nat):
render(iptables_nat_config, 'firewall/nftables-nat66.tmpl', nat, permission=0o755)
render(ndppd_config, 'ndppd/ndppd.conf.tmpl', nat, permission=0o755)
return None
def apply(nat):
if not nat:
return None
cmd(f'{iptables_nat_config}')
if 'deleted' in nat or not dict_search('source.rule', nat):
cmd('systemctl stop ndppd')
if os.path.isfile(ndppd_config):
os.unlink(ndppd_config)
else:
cmd('systemctl restart ndppd')
if os.path.isfile(iptables_nat_config):
os.unlink(iptables_nat_config)
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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