policy.py
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policy.py
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	#!/usr/bin/env python3
	#
	# Copyright VyOS maintainers and contributors <maintainers@vyos.io>
	#
	# 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 re
	from sys import exit

	from vyos.config import Config
	from vyos.configverify import has_frr_protocol_in_dict
	from vyos.frrender import FRRender
	from vyos.frrender import frr_protocols
	from vyos.frrender import get_frrender_dict
	from vyos.utils.dict import dict_search
	from vyos.utils.process import is_systemd_service_running
	from vyos import ConfigError
	from vyos.base import Warning
	from vyos import airbag
	airbag.enable()

	# Sanity checks for large-community-list regex:
	# * Require complete 3-tuples, no blank members. Catch missed & doubled colons.
	# * Permit appropriate community separators (whitespace, underscore)
	# * Permit common regex between tuples while requiring at least one separator
	# (eg, "1:1:1_.*_4:4:4", matching "1:1:1 4:4:4" and "1:1:1 2:2:2 4:4:4",
	# but not "1:1:13 24:4:4")
	# Best practice: stick with basic patterns, mind your wildcards and whitespace.
	# Regex that doesn't match this pattern will be allowed with a warning.
	large_community_regex_pattern = r'([^: _]+):([^: _]+):([^: _]+)([ _]([^:]+):([^: _]+):([^: _]+))*'

	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()

	return get_frrender_dict(conf)


	def verify(config_dict):
	if not has_frr_protocol_in_dict(config_dict, 'policy'):
	return None

	policy_types = ['access_list', 'access_list6', 'as_path_list',
	'community_list', 'extcommunity_list',
	'large_community_list', 'prefix_list',
	'prefix_list6', 'route_map']

	policy = config_dict['policy']
	for protocol in frr_protocols:
	if protocol not in config_dict:
	continue
	if 'protocol' not in policy:
	policy.update({'protocol': {}})
	policy['protocol'].update({protocol : config_dict[protocol]})

	for policy_type in policy_types:
	# 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 == 'large_community_list':
	if not re.fullmatch(large_community_regex_pattern, rule_config['regex']):
	Warning(f'"policy large-community-list {instance} rule {rule} regex" does not follow expected form and may not match as expected.')

	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" or "on-match"
	# FRR does not validate it T4827, T6676
	if rule_config['action'] == 'deny' and ('continue' in rule_config or 'on_match' in rule_config):
	raise ConfigError(f'rule {rule} "continue" or "on-match" 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
	# Check if any routing protocol is activated
	if 'protocol' in policy:
	for policy_type in policy_types:
	for policy_name in list(set(routing_policy_find(policy_type, policy['protocol']))):
	found = False
	if policy_type in policy and 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(config_dict):
	if config_dict and not is_systemd_service_running('vyos-configd.service'):
	FRRender().generate(config_dict)
	return None

	def apply(config_dict):
	if config_dict and not is_systemd_service_running('vyos-configd.service'):
	FRRender().apply()
	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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