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vyos-failover.py
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vyos-failover.py
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#!/usr/bin/env python3
#
# Copyright (C) 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/>.
import argparse
import json
import subprocess
import socket
import time
from vyos.util import rc_cmd
from pathlib import Path
from systemd import journal
my_name = Path(__file__).stem
def get_best_route_options(route, debug=False):
"""
Return current best route ('gateway, interface, metric)
% get_best_route_options('203.0.113.1')
('192.168.0.1', 'eth1', 1)
% get_best_route_options('203.0.113.254')
(None, None, None)
"""
rc, data = rc_cmd(f'ip --detail --json route show protocol failover {route}')
if rc == 0:
data = json.loads(data)
if len(data) == 0:
print(f'\nRoute {route} for protocol failover was not found')
return None, None, None
# Fake metric 999 by default
# Search route with the lowest metric
best_metric = 999
for entry in data:
if debug: print('\n', entry)
metric = entry.get('metric')
gateway = entry.get('gateway')
iface = entry.get('dev')
if metric < best_metric:
best_metric = metric
best_gateway = gateway
best_interface = iface
if debug:
print(f'### Best_route exists: {route}, best_gateway: {best_gateway}, '
f'best_metric: {best_metric}, best_iface: {best_interface}')
return best_gateway, best_interface, best_metric
def is_port_open(ip, port):
"""
Check connection to remote host and port
Return True if host alive
% is_port_open('example.com', 8080)
True
"""
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, socket.IPPROTO_TCP)
s.settimeout(2)
try:
s.connect((ip, int(port)))
s.shutdown(socket.SHUT_RDWR)
return True
except:
return False
finally:
s.close()
def is_target_alive(target=None, iface='', proto='icmp', port=None, debug=False):
"""
Host availability check by ICMP, ARP, TCP
Return True if target checks is successful
% is_target_alive('192.0.2.1', 'eth1', proto='arp')
True
"""
if iface != '':
iface = f'-I {iface}'
if proto == 'icmp':
command = f'/usr/bin/ping -q {target} {iface} -n -c 2 -W 1'
rc, response = rc_cmd(command)
if debug: print(f' [ CHECK-TARGET ]: [{command}] -- return-code [RC: {rc}]')
if rc == 0:
return True
elif proto == 'arp':
command = f'/usr/bin/arping -b -c 2 -f -w 1 -i 1 {iface} {target}'
rc, response = rc_cmd(command)
if debug: print(f' [ CHECK-TARGET ]: [{command}] -- return-code [RC: {rc}]')
if rc == 0:
return True
elif proto == 'tcp' and port is not None:
return True if is_port_open(target, port) else False
else:
return False
if __name__ == '__main__':
# Parse command arguments and get config
parser = argparse.ArgumentParser()
parser.add_argument('-c',
'--config',
action='store',
help='Path to protocols failover configuration',
required=True,
type=Path)
args = parser.parse_args()
try:
config_path = Path(args.config)
config = json.loads(config_path.read_text())
except Exception as err:
print(
f'Configuration file "{config_path}" does not exist or malformed: {err}'
)
exit(1)
# Useful debug info to console, use debug = True
# sudo systemctl stop vyos-failover.service
# sudo /usr/libexec/vyos/vyos-failover.py --config /run/vyos-failover.conf
debug = False
while(True):
for route, route_config in config.get('route').items():
exists_route = exists_gateway, exists_iface, exists_metric = get_best_route_options(route, debug=debug)
for next_hop, nexthop_config in route_config.get('next_hop').items():
conf_iface = nexthop_config.get('interface')
conf_metric = int(nexthop_config.get('metric'))
port = nexthop_config.get('check').get('port')
port_opt = f'port {port}' if port else ''
proto = nexthop_config.get('check').get('type')
target = nexthop_config.get('check').get('target')
timeout = nexthop_config.get('check').get('timeout')
# Best route not fonund in the current routing table
if exists_route == (None, None, None):
if debug: print(f" [NEW_ROUTE_DETECTED] route: [{route}]")
# Add route if check-target alive
if is_target_alive(target, conf_iface, proto, port, debug=debug):
if debug: print(f' [ ADD ] -- ip route add {route} via {next_hop} dev {conf_iface} '
f'metric {conf_metric} proto failover\n###')
rc, command = rc_cmd(f'ip route add {route} via {next_hop} dev {conf_iface} '
f'metric {conf_metric} proto failover')
# If something is wrong and gateway not added
# Example: Error: Next-hop has invalid gateway.
if rc !=0:
if debug: print(f'{command} -- return-code [RC: {rc}] {next_hop} dev {conf_iface}')
else:
journal.send(f'ip route add {route} via {next_hop} dev {conf_iface} '
f'metric {conf_metric} proto failover', SYSLOG_IDENTIFIER=my_name)
else:
if debug: print(f' [ TARGET_FAIL ] target checks fails for [{target}], do nothing')
journal.send(f'Check fail for route {route} target {target} proto {proto} '
f'{port_opt}', SYSLOG_IDENTIFIER=my_name)
# Route was added, check if the target is alive
# We should delete route if check fails only if route exists in the routing table
if not is_target_alive(target, conf_iface, proto, port, debug=debug) and \
exists_route != (None, None, None):
if debug:
print(f'Nexh_hop {next_hop} fail, target not response')
print(f' [ DEL ] -- ip route del {route} via {next_hop} dev {conf_iface} '
f'metric {conf_metric} proto failover [DELETE]')
rc_cmd(f'ip route del {route} via {next_hop} dev {conf_iface} metric {conf_metric} proto failover')
journal.send(f'ip route del {route} via {next_hop} dev {conf_iface} '
f'metric {conf_metric} proto failover', SYSLOG_IDENTIFIER=my_name)
time.sleep(int(timeout))

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