kolla/dev/vagrant/newest_dhcp_lease.py
Michal Rostecki 9895e98d17 Use MAC address for looking for DHCP leases for Vagrant
Change-Id: If87e83f7a50c0341f4b1238310eb1469eea0f767
Closes-Bug: 1570739
2016-06-21 04:58:27 +00:00

135 lines
4.1 KiB
Python

#!/usr/bin/env python
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Command-line utility to get the IP address from the newest DHCP lease.
It's written for using with vagrant-hostmanager and vagrant-libvirt plugins.
Vagrant-hostmanager by default fetches only IP addresses from eth0 interfaces
on VM-s. Therefore, the first purpose of this utility is to be able to fetch
the address also from the other interfaces.
Libvirt/virsh only lists all DHCP leases for the given network with timestamps.
DHCP leases have their expiration time, but are not cleaned up after destroying
VM. If someone destroys and sets up the VM with the same hostname, we have
many DHCP leases for the same hostname and we have to look up for timestamp.
That's the second purpose of this script.
"""
import argparse
import csv
import functools
import operator
import xml.etree.ElementTree as etree
import libvirt
class NoPrivateDHCPInterfaceException(Exception):
pass
class NoDHCPLeaseException(Exception):
pass
def libvirt_conn(f):
@functools.wraps(f)
def wrapper(*args, **kwargs):
conn = libvirt.openReadOnly('qemu:///system')
return f(conn, *args, **kwargs)
return wrapper
@libvirt_conn
def get_vir_network_dhcp_lease(conn, vm_name):
"""Libvirt since 1.2.6 version provides DHCPLeases method in virNetwork.
That's the current official way for getting DHCP leases and this
information isn't stored anywhere else anymore.
"""
domain_name = 'vagrant_' + vm_name
mac_address = get_mac_address(conn, domain_name)
network = conn.networkLookupByName('vagrant-private-dhcp')
dhcp_leases = libvirt.virNetwork.DHCPLeases(network)
vm_dhcp_leases = filter(lambda lease: lease['mac'] == mac_address,
dhcp_leases)
newest_vm_dhcp_lease = sorted(vm_dhcp_leases,
key=operator.itemgetter('expirytime'),
reverse=True)[0]['ipaddr']
return newest_vm_dhcp_lease
def get_mac_address(conn, domain_name):
"""Get MAC address from domain XML."""
domain = conn.lookupByName(domain_name)
domain_xml = domain.XMLDesc()
domain_tree = etree.fromstring(domain_xml)
devices = domain_tree.find('devices')
interfaces = devices.iterfind('interface')
for interface in interfaces:
source = interface.find('source')
if source is None or source.get('network') != 'vagrant-private-dhcp':
continue
mac_element = interface.find('mac')
mac_address = mac_element.get('address')
return mac_address
raise NoPrivateDHCPInterfaceException()
@libvirt_conn
def get_dnsmasq_dhcp_lease(conn, vm_name):
"""In libvirt under 1.2.6 DHCP leases are stored in file.
There is no API for DHCP leases yet.
"""
domain_name = 'vagrant_' + vm_name
mac_address = get_mac_address(conn, domain_name)
with open(
'/var/lib/libvirt/dnsmasq/vagrant-private-dhcp.leases'
) as leases_file:
reader = csv.reader(leases_file, delimiter=' ')
for row in reader:
lease_mac, lease_ip, lease_vm_name = row[1:4]
if not (lease_mac == mac_address and lease_vm_name == vm_name):
continue
return lease_ip
raise NoDHCPLeaseException()
def main():
parser = argparse.ArgumentParser()
parser.add_argument('vm_name', help='Name of the virtual machine')
args = parser.parse_args()
vm_name = args.vm_name
if libvirt.getVersion() >= 1002006:
newest_dhcp_lease = get_vir_network_dhcp_lease(vm_name)
else:
newest_dhcp_lease = get_dnsmasq_dhcp_lease(vm_name)
print(newest_dhcp_lease)
if __name__ == '__main__':
main()