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protocols_bfd.py
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protocols_bfd.py
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#!/usr/bin/env python3
#
# Copyright (C) 2019-2020 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 sys import exit
from copy import deepcopy
from vyos.config import Config
from vyos.validate import is_ipv6_link_local, is_ipv6
from vyos import ConfigError
from vyos.util import call
from vyos.template import render
from vyos import airbag
airbag.enable()
config_file = r'/tmp/bfd.frr'
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 = 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 link local peers require an explicit local address/interface
if is_ipv6_link_local(peer['remote']):
if not (peer['src_if'] and peer['src_addr']):
raise ConfigError('BFD IPv6 link-local peers require explicit local address and interface setting')
# IPv6 peers require an explicit local address
if is_ipv6(peer['remote']):
if not peer['src_addr']:
raise ConfigError('BFD IPv6 peers require explicit local address 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
render(config_file, 'frr/bfd.frr.tmpl', bfd)
return None
def apply(bfd):
if bfd is None:
return None
call("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)
exit(1)

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