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policy.py
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policy.py
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#!/usr/bin/env python3
#
# Copyright (C) 2021-2022 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/>.
from sys import exit
from vyos.config import Config
from vyos.configdict import dict_merge
from vyos.template import render_to_string
from vyos.util import dict_search
from vyos import ConfigError
from vyos import frr
from vyos import airbag
airbag.enable()
def community_action_compatibility(actions: dict) -> bool:
"""
Check compatibility of values in community and large community sections
:param actions: dictionary with community
:type actions: dict
:return: true if compatible, false if not
:rtype: bool
"""
if ('none' in actions) and ('replace' in actions or 'add' in actions):
return False
if 'replace' in actions and 'add' in actions:
return False
if ('delete' in actions) and ('none' in actions or 'replace' in actions):
return False
return True
def extcommunity_action_compatibility(actions: dict) -> bool:
"""
Check compatibility of values in extended community sections
:param actions: dictionary with community
:type actions: dict
:return: true if compatible, false if not
:rtype: bool
"""
if ('none' in actions) and (
'rt' in actions or 'soo' in actions or 'bandwidth' in actions or 'bandwidth_non_transitive' in actions):
return False
if ('bandwidth_non_transitive' in actions) and ('bandwidth' not in actions):
return False
return True
def routing_policy_find(key, dictionary):
# Recursively traverse a dictionary and extract the value assigned to
# a given key as generator object. This is made for routing policies,
# thus also import/export is checked
for k, v in dictionary.items():
if k == key:
if isinstance(v, dict):
for a, b in v.items():
if a in ['import', 'export']:
yield b
else:
yield v
elif isinstance(v, dict):
for result in routing_policy_find(key, v):
yield result
elif isinstance(v, list):
for d in v:
if isinstance(d, dict):
for result in routing_policy_find(key, d):
yield result
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)
# We also need some additional information from the config, prefix-lists
# and route-maps for instance. They will be used in verify().
#
# XXX: one MUST always call this without the key_mangling() option! See
# vyos.configverify.verify_common_route_maps() for more information.
tmp = conf.get_config_dict(['protocols'], key_mangling=('-', '_'),
no_tag_node_value_mangle=True)
# Merge policy dict into "regular" config dict
policy = dict_merge(tmp, policy)
return policy
def verify(policy):
if not policy:
return None
for policy_type in ['access_list', 'access_list6', 'as_path_list',
'community_list', 'extcommunity_list',
'large_community_list',
'prefix_list', 'prefix_list6', 'route_map']:
# Bail out early and continue with next policy type
if policy_type not in policy:
continue
# instance can be an ACL name/number, prefix-list name or route-map name
for instance, instance_config in policy[policy_type].items():
# If no rule was found within the instance ... sad, but we can leave
# early as nothing needs to be verified
if 'rule' not in instance_config:
continue
# human readable instance name (hypen instead of underscore)
policy_hr = policy_type.replace('_', '-')
entries = []
for rule, rule_config in instance_config['rule'].items():
mandatory_error = f'must be specified for "{policy_hr} {instance} rule {rule}"!'
if 'action' not in rule_config:
raise ConfigError(f'Action {mandatory_error}')
if policy_type == 'access_list':
if 'source' not in rule_config:
raise ConfigError(f'A source {mandatory_error}')
if int(instance) in range(100, 200) or int(
instance) in range(2000, 2700):
if 'destination' not in rule_config:
raise ConfigError(
f'A destination {mandatory_error}')
if policy_type == 'access_list6':
if 'source' not in rule_config:
raise ConfigError(f'A source {mandatory_error}')
if policy_type in ['as_path_list', 'community_list',
'extcommunity_list',
'large_community_list']:
if 'regex' not in rule_config:
raise ConfigError(f'A regex {mandatory_error}')
if policy_type in ['prefix_list', 'prefix_list6']:
if 'prefix' not in rule_config:
raise ConfigError(f'A prefix {mandatory_error}')
if rule_config in entries:
raise ConfigError(
f'Rule "{rule}" contains a duplicate prefix definition!')
entries.append(rule_config)
# route-maps tend to be a bit more complex so they get their own verify() section
if 'route_map' in policy:
for route_map, route_map_config in policy['route_map'].items():
if 'rule' not in route_map_config:
continue
for rule, rule_config in route_map_config['rule'].items():
# Action 'deny' cannot be used with "continue"
# FRR does not validate it T4827
if rule_config['action'] == 'deny' and 'continue' in rule_config:
raise ConfigError(f'rule {rule} "continue" cannot be used with action deny!')
# Specified community-list must exist
tmp = dict_search('match.community.community_list',
rule_config)
if tmp and tmp not in policy.get('community_list', []):
raise ConfigError(f'community-list {tmp} does not exist!')
# Specified extended community-list must exist
tmp = dict_search('match.extcommunity', rule_config)
if tmp and tmp not in policy.get('extcommunity_list', []):
raise ConfigError(
f'extcommunity-list {tmp} does not exist!')
# Specified large-community-list must exist
tmp = dict_search('match.large_community.large_community_list',
rule_config)
if tmp and tmp not in policy.get('large_community_list', []):
raise ConfigError(
f'large-community-list {tmp} does not exist!')
# Specified prefix-list must exist
tmp = dict_search('match.ip.address.prefix_list', rule_config)
if tmp and tmp not in policy.get('prefix_list', []):
raise ConfigError(f'prefix-list {tmp} does not exist!')
# Specified prefix-list must exist
tmp = dict_search('match.ipv6.address.prefix_list',
rule_config)
if tmp and tmp not in policy.get('prefix_list6', []):
raise ConfigError(f'prefix-list6 {tmp} does not exist!')
# Specified access_list6 in nexthop must exist
tmp = dict_search('match.ipv6.nexthop.access_list',
rule_config)
if tmp and tmp not in policy.get('access_list6', []):
raise ConfigError(f'access_list6 {tmp} does not exist!')
# Specified prefix-list6 in nexthop must exist
tmp = dict_search('match.ipv6.nexthop.prefix_list',
rule_config)
if tmp and tmp not in policy.get('prefix_list6', []):
raise ConfigError(f'prefix-list6 {tmp} does not exist!')
tmp = dict_search('set.community.delete', rule_config)
if tmp and tmp not in policy.get('community_list', []):
raise ConfigError(f'community-list {tmp} does not exist!')
tmp = dict_search('set.large_community.delete',
rule_config)
if tmp and tmp not in policy.get('large_community_list', []):
raise ConfigError(
f'large-community-list {tmp} does not exist!')
if 'set' in rule_config:
rule_action = rule_config['set']
if 'community' in rule_action:
if not community_action_compatibility(
rule_action['community']):
raise ConfigError(
f'Unexpected combination between action replace, add, delete or none in community')
if 'large_community' in rule_action:
if not community_action_compatibility(
rule_action['large_community']):
raise ConfigError(
f'Unexpected combination between action replace, add, delete or none in large-community')
if 'extcommunity' in rule_action:
if not extcommunity_action_compatibility(
rule_action['extcommunity']):
raise ConfigError(
f'Unexpected combination between none, rt, soo, bandwidth, bandwidth-non-transitive in extended-community')
# When routing protocols are active some use prefix-lists, route-maps etc.
# to apply the systems routing policy to the learned or redistributed routes.
# When the "routing policy" changes and policies, route-maps etc. are deleted,
# it is our responsibility to verify that the policy can not be deleted if it
# is used by any routing protocol
if 'protocols' in policy:
for policy_type in ['access_list', 'access_list6', 'as_path_list',
'community_list',
'extcommunity_list', 'large_community_list',
'prefix_list', 'route_map']:
if policy_type in policy:
for policy_name in list(set(routing_policy_find(policy_type,
policy[
'protocols']))):
found = False
if policy_name in policy[policy_type]:
found = True
# BGP uses prefix-list for selecting both an IPv4 or IPv6 AFI related
# list - we need to go the extra mile here and check both prefix-lists
if policy_type == 'prefix_list' and 'prefix_list6' in policy and policy_name in \
policy['prefix_list6']:
found = True
if not found:
tmp = policy_type.replace('_', '-')
raise ConfigError(
f'Can not delete {tmp} "{policy_name}", still in use!')
return None
def generate(policy):
if not policy:
return None
policy['new_frr_config'] = render_to_string('frr/policy.frr.j2', policy)
return None
def apply(policy):
bgp_daemon = 'bgpd'
zebra_daemon = 'zebra'
# Save original configuration prior to starting any commit actions
frr_cfg = frr.FRRConfig()
# The route-map used for the FIB (zebra) is part of the zebra daemon
frr_cfg.load_configuration(bgp_daemon)
frr_cfg.modify_section(r'^bgp as-path access-list .*')
frr_cfg.modify_section(r'^bgp community-list .*')
frr_cfg.modify_section(r'^bgp extcommunity-list .*')
frr_cfg.modify_section(r'^bgp large-community-list .*')
frr_cfg.modify_section(r'^route-map .*', stop_pattern='^exit',
remove_stop_mark=True)
if 'new_frr_config' in policy:
frr_cfg.add_before(frr.default_add_before, policy['new_frr_config'])
frr_cfg.commit_configuration(bgp_daemon)
# The route-map used for the FIB (zebra) is part of the zebra daemon
frr_cfg.load_configuration(zebra_daemon)
frr_cfg.modify_section(r'^access-list .*')
frr_cfg.modify_section(r'^ipv6 access-list .*')
frr_cfg.modify_section(r'^ip prefix-list .*')
frr_cfg.modify_section(r'^ipv6 prefix-list .*')
frr_cfg.modify_section(r'^route-map .*', stop_pattern='^exit',
remove_stop_mark=True)
if 'new_frr_config' in policy:
frr_cfg.add_before(frr.default_add_before, policy['new_frr_config'])
frr_cfg.commit_configuration(zebra_daemon)
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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