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#!/usr/bin/env python3
#
# Copyright (C) 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 os
from json import loads
from sys import exit
from vyos.config import Config
from vyos.template import render
from vyos.util import cmd
from vyos.util import dict_search_args
from vyos.util import run
from vyos import ConfigError
from vyos import airbag
airbag.enable()
mark_offset = 0x7FFFFFFF
nftables_conf = '/run/nftables_policy.conf'
def get_config(config=None):
if config:
conf = config
else:
conf = Config()
base = ['policy']
if not conf.exists(base + ['route']) and not conf.exists(base + ['ipv6-route']):
return None
policy = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True,
no_tag_node_value_mangle=True)
return policy
def verify(policy):
# bail out early - looks like removal from running config
if not policy:
return None
for route in ['route', 'ipv6_route']:
if route in policy:
for name, pol_conf in policy[route].items():
if 'rule' in pol_conf:
for rule_id, rule_conf in pol_conf.items():
icmp = 'icmp' if route == 'route' else 'icmpv6'
if icmp in rule_conf:
icmp_defined = False
if 'type_name' in rule_conf[icmp]:
icmp_defined = True
if 'code' in rule_conf[icmp] or 'type' in rule_conf[icmp]:
raise ConfigError(f'{name} rule {rule_id}: Cannot use ICMP type/code with ICMP type-name')
if 'code' in rule_conf[icmp]:
icmp_defined = True
if 'type' not in rule_conf[icmp]:
raise ConfigError(f'{name} rule {rule_id}: ICMP code can only be defined if ICMP type is defined')
if 'type' in rule_conf[icmp]:
icmp_defined = True
if icmp_defined and 'protocol' not in rule_conf or rule_conf['protocol'] != icmp:
raise ConfigError(f'{name} rule {rule_id}: ICMP type/code or type-name can only be defined if protocol is ICMP')
if 'set' in rule_conf:
if 'tcp_mss' in rule_conf['set']:
tcp_flags = dict_search_args(rule_conf, 'tcp', 'flags')
if not tcp_flags or 'SYN' not in tcp_flags.split(","):
raise ConfigError(f'{name} rule {rule_id}: TCP SYN flag must be set to modify TCP-MSS')
if 'tcp' in rule_conf:
if 'flags' in rule_conf['tcp']:
if 'protocol' not in rule_conf or rule_conf['protocol'] != 'tcp':
raise ConfigError(f'{name} rule {rule_id}: TCP flags can only be set if protocol is set to TCP')
return None
def generate(policy):
if not policy:
if os.path.exists(nftables_conf):
os.unlink(nftables_conf)
return None
if not os.path.exists(nftables_conf):
policy['first_install'] = True
render(nftables_conf, 'firewall/nftables-policy.tmpl', policy)
return None
def apply_table_marks(policy):
for route in ['route', 'ipv6_route']:
if route in policy:
for name, pol_conf in policy[route].items():
if 'rule' in pol_conf:
for rule_id, rule_conf in pol_conf['rule'].items():
set_table = dict_search_args(rule_conf, 'set', 'table')
if set_table:
if set_table == 'main':
set_table = '254'
table_mark = mark_offset - int(set_table)
cmd(f'ip rule add fwmark {table_mark} table {set_table}')
def cleanup_table_marks():
json_rules = cmd('ip -j -N rule list')
rules = loads(json_rules)
for rule in rules:
if 'fwmark' not in rule or 'table' not in rule:
continue
fwmark = rule['fwmark']
table = int(rule['table'])
if fwmark[:2] == '0x':
fwmark = int(fwmark, 16)
if (int(fwmark) == (mark_offset - table)):
cmd(f'ip rule del fwmark {fwmark} table {table}')
def apply(policy):
if not policy or 'first_install' not in policy:
run(f'nft flush table ip mangle')
run(f'nft flush table ip6 mangle')
if not policy:
cleanup_table_marks()
return None
install_result = run(f'nft -f {nftables_conf}')
if install_result == 1:
raise ConfigError('Failed to apply policy based routing')
if 'first_install' not in policy:
cleanup_table_marks()
apply_table_marks(policy)
return None
if __name__ == '__main__':
try:
c = get_config()
verify(c)
generate(c)
apply(c)
except ConfigError as e:
print(e)
exit(1)
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