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clear_dhcp_lease.py
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clear_dhcp_lease.py
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#!/usr/bin/env python3
import argparse
import re
from isc_dhcp_leases import Lease
from isc_dhcp_leases import IscDhcpLeases
from vyos.configquery import ConfigTreeQuery
from vyos.util import ask_yes_no
from vyos.util import call
from vyos.util import commit_in_progress
config = ConfigTreeQuery()
base = ['service', 'dhcp-server']
lease_file = '/config/dhcpd.leases'
def del_lease_ip(address):
"""
Read lease_file and write data to this file
without specific section "lease ip"
Delete section "lease x.x.x.x { x;x;x; }"
"""
with open(lease_file, encoding='utf-8') as f:
data = f.read().rstrip()
lease_config_ip = '{(?P<config>[\s\S]+?)\n}'
pattern = rf"lease {address} {lease_config_ip}"
# Delete lease for ip block
data = re.sub(pattern, '', data)
# Write new data to original lease_file
with open(lease_file, 'w', encoding='utf-8') as f:
f.write(data)
def is_ip_in_leases(address):
"""
Return True if address found in the lease file
"""
leases = IscDhcpLeases(lease_file)
lease_ips = []
for lease in leases.get():
lease_ips.append(lease.ip)
if address not in lease_ips:
print(f'Address "{address}" not found in "{lease_file}"')
return False
return True
if not config.exists(base):
print('DHCP-server not configured!')
exit(0)
if config.exists(base + ['failover']):
print('Lease cannot be reset in failover mode!')
exit(0)
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument('--ip', help='IPv4 address', action='store', required=True)
args = parser.parse_args()
address = args.ip
if not is_ip_in_leases(address):
exit(1)
if commit_in_progress():
print('Cannot clear DHCP lease while a commit is in progress')
exit(1)
if not ask_yes_no(f'This will restart DHCP server.\nContinue?'):
exit(1)
else:
del_lease_ip(address)
call('systemctl restart isc-dhcp-server.service')

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