protocols_bfd.py
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protocols_bfd.py
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	#!/usr/bin/env python3
	#
	# Copyright (C) 2019 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 sys
	import jinja2
	import copy
	import os
	import vyos.validate

	from vyos import ConfigError
	from vyos.config import Config

	config_file = r'/tmp/bfd.frr'

	# Please be careful if you edit the template.
	config_tmpl = """
	!
	bfd
	{% for peer in old_peers -%}
	no peer {{ peer.remote }}{% if peer.multihop %} multihop{% endif %}{% if peer.src_addr %} local-address {{ peer.src_addr }}{% endif %}{% if peer.src_if %} interface {{ peer.src_if }}{% endif %}
	{% endfor -%}
	!
	{% for peer in new_peers -%}
	peer {{ peer.remote }}{% if peer.multihop %} multihop{% endif %}{% if peer.src_addr %} local-address {{ peer.src_addr }}{% endif %}{% if peer.src_if %} interface {{ peer.src_if }}{% endif %}
	detect-multiplier {{ peer.multiplier }}
	receive-interval {{ peer.rx_interval }}
	transmit-interval {{ peer.tx_interval }}
	{% if peer.echo_mode %}echo-mode{% endif %}
	{% if peer.echo_interval != '' %}echo-interval {{ peer.echo_interval }}{% endif %}
	{% if not peer.shutdown %}no {% endif %}shutdown
	{% endfor -%}
	!
	"""

	default_config_data = {
	'new_peers': [],
	'old_peers' : []
	}

	# get configuration for BFD peer from proposed or effective configuration
	def get_bfd_peer_config(peer, conf_mode="proposed"):
	conf = Config()
	conf.set_level('protocols bfd peer {0}'.format(peer))

	bfd_peer = {
	'remote': peer,
	'shutdown': False,
	'src_if': '',
	'src_addr': '',
	'multiplier': '3',
	'rx_interval': '300',
	'tx_interval': '300',
	'multihop': False,
	'echo_interval': '',
	'echo_mode': False,
	}

	# Check if individual peer is disabled
	if conf_mode == "effective" and conf.exists_effective('shutdown'):
	bfd_peer['shutdown'] = True
	if conf_mode == "proposed" and conf.exists('shutdown'):
	bfd_peer['shutdown'] = True

	# Check if peer has a local source interface configured
	if conf_mode == "effective" and conf.exists_effective('source interface'):
	bfd_peer['src_if'] = conf.return_effective_value('source interface')
	if conf_mode == "proposed" and conf.exists('source interface'):
	bfd_peer['src_if'] = conf.return_value('source interface')

	# Check if peer has a local source address configured - this is mandatory for IPv6
	if conf_mode == "effective" and conf.exists_effective('source address'):
	bfd_peer['src_addr'] = conf.return_effective_value('source address')
	if conf_mode == "proposed" and conf.exists('source address'):
	bfd_peer['src_addr'] = conf.return_value('source address')

	# Tell BFD daemon that we should expect packets with TTL less than 254
	# (because it will take more than one hop) and to listen on the multihop
	# port (4784)
	if conf_mode == "effective" and conf.exists_effective('multihop'):
	bfd_peer['multihop'] = True
	if conf_mode == "proposed" and conf.exists('multihop'):
	bfd_peer['multihop'] = True

	# Configures the minimum interval that this system is capable of receiving
	# control packets. The default value is 300 milliseconds.
	if conf_mode == "effective" and conf.exists_effective('interval receive'):
	bfd_peer['rx_interval'] = conf.return_effective_value('interval receive')
	if conf_mode == "proposed" and conf.exists('interval receive'):
	bfd_peer['rx_interval'] = conf.return_value('interval receive')

	# The minimum transmission interval (less jitter) that this system wants
	# to use to send BFD control packets.
	if conf_mode == "effective" and conf.exists_effective('interval transmit'):
	bfd_peer['tx_interval'] = conf.return_effective_value('interval transmit')
	if conf_mode == "proposed" and conf.exists('interval transmit'):
	bfd_peer['tx_interval'] = conf.return_value('interval transmit')

	# Configures the detection multiplier to determine packet loss. The remote
	# transmission interval will be multiplied by this value to determine the
	# connection loss detection timer. The default value is 3.
	if conf_mode == "effective" and conf.exists_effective('interval multiplier'):
	bfd_peer['multiplier'] = conf.return_effective_value('interval multiplier')
	if conf_mode == "proposed" and conf.exists('interval multiplier'):
	bfd_peer['multiplier'] = conf.return_value('interval multiplier')

	# Configures the minimal echo receive transmission interval that this system is capable of handling
	if conf_mode == "effective" and conf.exists_effective('interval echo-interval'):
	bfd_peer['echo_interval'] = conf.return_effective_value('interval echo-interval')
	if conf_mode == "proposed" and conf.exists('interval echo-interval'):
	bfd_peer['echo_interval'] = conf.return_value('interval echo-interval')

	# Enables or disables the echo transmission mode
	if conf_mode == "effective" and conf.exists_effective('echo-mode'):
	bfd_peer['echo_mode'] = True
	if conf_mode == "proposed" and conf.exists('echo-mode'):
	bfd_peer['echo_mode'] = True

	return bfd_peer

	def get_config():
	bfd = copy.deepcopy(default_config_data)
	conf = Config()
	if not (conf.exists('protocols bfd') or conf.exists_effective('protocols bfd')):
	return None
	else:
	conf.set_level('protocols bfd')

	# as we have to use vtysh to talk to FRR we also need to know
	# which peers are gone due to a config removal - thus we read in
	# all peers (active or to delete)
	for peer in conf.list_effective_nodes('peer'):
	bfd['old_peers'].append(get_bfd_peer_config(peer, "effective"))

	for peer in conf.list_nodes('peer'):
	bfd['new_peers'].append(get_bfd_peer_config(peer))

	# find deleted peers
	set_new_peers = set(conf.list_nodes('peer'))
	set_old_peers = set(conf.list_effective_nodes('peer'))
	bfd['deleted_peers'] = set_old_peers - set_new_peers

	return bfd

	def verify(bfd):
	if bfd is None:
	return None

	# some variables to use later
	conf = Config()

	for peer in bfd['new_peers']:
	# IPv6 peers require an explicit local address/interface combination
	if vyos.validate.is_ipv6(peer['remote']):
	if not (peer['src_if'] and peer['src_addr']):
	raise ConfigError('BFD IPv6 peers require explicit local address and interface setting')

	# multihop require source address
	if peer['multihop'] and not peer['src_addr']:
	raise ConfigError('Multihop require source address')

	# multihop and echo-mode cannot be used together
	if peer['multihop'] and peer['echo_mode']:
	raise ConfigError('Multihop and echo-mode cannot be used together')

	# multihop doesn't accept interface names
	if peer['multihop'] and peer['src_if']:
	raise ConfigError('Multihop and source interface cannot be used together')

	# echo interval can be configured only with enabled echo-mode
	if peer['echo_interval'] != '' and not peer['echo_mode']:
	raise ConfigError('echo-interval can be configured only with enabled echo-mode')

	# check if we deleted peers are not used in configuration
	if conf.exists('protocols bgp'):
	bgp_as = conf.list_nodes('protocols bgp')[0]

	# check BGP neighbors
	for peer in bfd['deleted_peers']:
	if conf.exists('protocols bgp {0} neighbor {1} bfd'.format(bgp_as, peer)):
	raise ConfigError('Cannot delete BFD peer {0}: it is used in BGP configuration'.format(peer))
	if conf.exists('protocols bgp {0} neighbor {1} peer-group'.format(bgp_as, peer)):
	peer_group = conf.return_value('protocols bgp {0} neighbor {1} peer-group'.format(bgp_as, peer))
	if conf.exists('protocols bgp {0} peer-group {1} bfd'.format(bgp_as, peer_group)):
	raise ConfigError('Cannot delete BFD peer {0}: it belongs to BGP peer-group {1} with enabled BFD'.format(peer, peer_group))

	return None

	def generate(bfd):
	if bfd is None:
	return None

	return None

	def apply(bfd):
	if bfd is None:
	return None

	tmpl = jinja2.Template(config_tmpl)
	config_text = tmpl.render(bfd)
	with open(config_file, 'w') as f:
	f.write(config_text)

	os.system("sudo vtysh -d bfdd -f " + config_file)
	if os.path.exists(config_file):
	os.remove(config_file)

	return None

	if __name__ == '__main__':
	try:
	c = get_config()
	verify(c)
	generate(c)
	apply(c)
	except ConfigError as e:
	print(e)
	sys.exit(1)

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