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policy-route.py
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policy-route.py
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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
import re
from json import loads
from sys import exit
from vyos.base import Warning
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 dict_search_recursive
from vyos.util import run
from vyos import ConfigError
from vyos import airbag
airbag.enable()
mark_offset = 0x7FFFFFFF
nftables_conf = '/run/nftables_policy.conf'
ROUTE_PREFIX = 'VYOS_PBR_'
ROUTE6_PREFIX = 'VYOS_PBR6_'
preserve_chains = [
'VYOS_PBR_PREROUTING',
'VYOS_PBR_POSTROUTING',
'VYOS_PBR6_PREROUTING',
'VYOS_PBR6_POSTROUTING'
]
valid_groups = [
'address_group',
'network_group',
'port_group'
]
group_set_prefix = {
'A_': 'address_group',
'A6_': 'ipv6_address_group',
# 'D_': 'domain_group',
'M_': 'mac_group',
'N_': 'network_group',
'N6_': 'ipv6_network_group',
'P_': 'port_group'
}
def get_policy_interfaces(conf):
out = {}
interfaces = conf.get_config_dict(['interfaces'], key_mangling=('-', '_'), get_first_key=True,
no_tag_node_value_mangle=True)
def find_interfaces(iftype_conf, output={}, prefix=''):
for ifname, if_conf in iftype_conf.items():
if 'policy' in if_conf:
output[prefix + ifname] = if_conf['policy']
for vif in ['vif', 'vif_s', 'vif_c']:
if vif in if_conf:
output.update(find_interfaces(if_conf[vif], output, f'{prefix}{ifname}.'))
return output
for iftype, iftype_conf in interfaces.items():
out.update(find_interfaces(iftype_conf))
return out
def get_config(config=None):
if config:
conf = config
else:
conf = Config()
base = ['policy']
policy = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True,
no_tag_node_value_mangle=True)
policy['firewall_group'] = conf.get_config_dict(['firewall', 'group'], key_mangling=('-', '_'), get_first_key=True,
no_tag_node_value_mangle=True)
policy['interfaces'] = get_policy_interfaces(conf)
return policy
def verify_rule(policy, name, rule_conf, ipv6, rule_id):
icmp = 'icmp' if not ipv6 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:
raise ConfigError(f'{name} rule {rule_id}: TCP SYN flag must be set to modify TCP-MSS')
tcp_flags = dict_search_args(rule_conf, 'tcp', 'flags')
if tcp_flags:
if dict_search_args(rule_conf, 'protocol') != 'tcp':
raise ConfigError('Protocol must be tcp when specifying tcp flags')
not_flags = dict_search_args(rule_conf, 'tcp', 'flags', 'not')
if not_flags:
duplicates = [flag for flag in tcp_flags if flag in not_flags]
if duplicates:
raise ConfigError(f'Cannot match a tcp flag as set and not set')
for side in ['destination', 'source']:
if side in rule_conf:
side_conf = rule_conf[side]
if 'group' in side_conf:
if {'address_group', 'network_group'} <= set(side_conf['group']):
raise ConfigError('Only one address-group or network-group can be specified')
for group in valid_groups:
if group in side_conf['group']:
group_name = side_conf['group'][group]
if group_name.startswith('!'):
group_name = group_name[1:]
fw_group = f'ipv6_{group}' if ipv6 and group in ['address_group', 'network_group'] else group
error_group = fw_group.replace("_", "-")
group_obj = dict_search_args(policy['firewall_group'], fw_group, group_name)
if group_obj is None:
raise ConfigError(f'Invalid {error_group} "{group_name}" on policy route rule')
if not group_obj:
Warning(f'{error_group} "{group_name}" has no members')
if 'port' in side_conf or dict_search_args(side_conf, 'group', 'port_group'):
if 'protocol' not in rule_conf:
raise ConfigError('Protocol must be defined if specifying a port or port-group')
if rule_conf['protocol'] not in ['tcp', 'udp', 'tcp_udp']:
raise ConfigError('Protocol must be tcp, udp, or tcp_udp when specifying a port or port-group')
def verify(policy):
for route in ['route', 'route6']:
ipv6 = route == 'route6'
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():
verify_rule(policy, name, rule_conf, ipv6, rule_id)
for ifname, if_policy in policy['interfaces'].items():
name = dict_search_args(if_policy, 'route')
ipv6_name = dict_search_args(if_policy, 'route6')
if name and not dict_search_args(policy, 'route', name):
raise ConfigError(f'Policy route "{name}" is still referenced on interface {ifname}')
if ipv6_name and not dict_search_args(policy, 'route6', ipv6_name):
raise ConfigError(f'Policy route6 "{ipv6_name}" is still referenced on interface {ifname}')
return None
def cleanup_commands(policy):
commands = []
commands_chains = []
commands_sets = []
for table in ['ip mangle', 'ip6 mangle']:
route_node = 'route' if table == 'ip mangle' else 'route6'
chain_prefix = ROUTE_PREFIX if table == 'ip mangle' else ROUTE6_PREFIX
json_str = cmd(f'nft -t -j list table {table}')
obj = loads(json_str)
if 'nftables' not in obj:
continue
for item in obj['nftables']:
if 'chain' in item:
chain = item['chain']['name']
if chain in preserve_chains or not chain.startswith("VYOS_PBR"):
continue
if dict_search_args(policy, route_node, chain.replace(chain_prefix, "", 1)) != None:
commands.append(f'flush chain {table} {chain}')
else:
commands_chains.append(f'delete chain {table} {chain}')
if 'rule' in item:
rule = item['rule']
chain = rule['chain']
handle = rule['handle']
if chain not in preserve_chains:
continue
target, _ = next(dict_search_recursive(rule['expr'], 'target'))
if target.startswith(chain_prefix):
if dict_search_args(policy, route_node, target.replace(chain_prefix, "", 1)) == None:
commands.append(f'delete rule {table} {chain} handle {handle}')
if 'set' in item:
set_name = item['set']['name']
for prefix, group_type in group_set_prefix.items():
if set_name.startswith(prefix):
group_name = set_name.replace(prefix, "", 1)
if dict_search_args(policy, 'firewall_group', group_type, group_name) != None:
commands_sets.append(f'flush set {table} {set_name}')
else:
commands_sets.append(f'delete set {table} {set_name}')
return commands + commands_chains + commands_sets
def generate(policy):
if not os.path.exists(nftables_conf):
policy['first_install'] = True
else:
policy['cleanup_commands'] = cleanup_commands(policy)
render(nftables_conf, 'firewall/nftables-policy.j2', policy)
return None
def apply_table_marks(policy):
for route in ['route', 'route6']:
if route in policy:
cmd_str = 'ip' if route == 'route' else 'ip -6'
tables = []
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'
if set_table in tables:
continue
tables.append(set_table)
table_mark = mark_offset - int(set_table)
cmd(f'{cmd_str} rule add pref {set_table} fwmark {table_mark} table {set_table}')
def cleanup_table_marks():
for cmd_str in ['ip', 'ip -6']:
json_rules = cmd(f'{cmd_str} -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'{cmd_str} rule del fwmark {fwmark} table {table}')
def apply(policy):
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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