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firewall_options.py
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firewall_options.py
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#!/usr/bin/env python3
#
# Copyright (C) 2018 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 os
import copy
from vyos.config import Config
from vyos import ConfigError
default_config_data = {
'intf_opts': [],
'new_chain4': False,
'new_chain6': False
}
def get_config():
opts = copy.deepcopy(default_config_data)
conf = Config()
if not conf.exists('firewall options'):
# bail out early
return opts
else:
conf.set_level('firewall options')
# Parse configuration of each individual instance
if conf.exists('interface'):
for intf in conf.list_nodes('interface'):
conf.set_level('firewall options interface {0}'.format(intf))
config = {
'intf': intf,
'disabled': False,
'mss4': '',
'mss6': ''
}
# Check if individual option is disabled
if conf.exists('disable'):
config['disabled'] = True
#
# Get MSS value IPv4
#
if conf.exists('adjust-mss'):
config['mss4'] = conf.return_value('adjust-mss')
# We need a marker that a new iptables chain needs to be generated
if not opts['new_chain4']:
opts['new_chain4'] = True
#
# Get MSS value IPv6
#
if conf.exists('adjust-mss6'):
config['mss6'] = conf.return_value('adjust-mss6')
# We need a marker that a new ip6tables chain needs to be generated
if not opts['new_chain6']:
opts['new_chain6'] = True
# Append interface options to global list
opts['intf_opts'].append(config)
return opts
def verify(tcp):
# syntax verification is done via cli
return None
def apply(tcp):
target = 'VYOS_FW_OPTIONS'
# always cleanup iptables
os.system('iptables --table mangle --delete FORWARD --jump {} >&/dev/null'.format(target))
os.system('iptables --table mangle --flush {} >&/dev/null'.format(target))
os.system('iptables --table mangle --delete-chain {} >&/dev/null'.format(target))
# always cleanup ip6tables
os.system('ip6tables --table mangle --delete FORWARD --jump {} >&/dev/null'.format(target))
os.system('ip6tables --table mangle --flush {} >&/dev/null'.format(target))
os.system('ip6tables --table mangle --delete-chain {} >&/dev/null'.format(target))
# Setup new iptables rules
if tcp['new_chain4']:
os.system('iptables --table mangle --new-chain {} >&/dev/null'.format(target))
os.system('iptables --table mangle --append FORWARD --jump {} >&/dev/null'.format(target))
for opts in tcp['intf_opts']:
intf = opts['intf']
mss = opts['mss4']
# Check if this rule iis disabled
if opts['disabled']:
continue
# adjust TCP MSS per interface
if mss:
os.system('iptables --table mangle --append {} --out-interface {} --protocol tcp ' \
'--tcp-flags SYN,RST SYN --jump TCPMSS --set-mss {} >&/dev/null'.format(target, intf, mss))
# Setup new ip6tables rules
if tcp['new_chain6']:
os.system('ip6tables --table mangle --new-chain {} >&/dev/null'.format(target))
os.system('ip6tables --table mangle --append FORWARD --jump {} >&/dev/null'.format(target))
for opts in tcp['intf_opts']:
intf = opts['intf']
mss = opts['mss6']
# Check if this rule iis disabled
if opts['disabled']:
continue
# adjust TCP MSS per interface
if mss:
os.system('ip6tables --table mangle --append {} --out-interface {} --protocol tcp ' \
'--tcp-flags SYN,RST SYN --jump TCPMSS --set-mss {} >&/dev/null'.format(target, intf, mss))
return None
if __name__ == '__main__':
try:
c = get_config()
verify(c)
apply(c)
except ConfigError as e:
print(e)
sys.exit(1)

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