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import threading
import traceback
import os
import logging
from time import sleep, time, mktime
from datetime import datetime
logger = logging.getLogger(__name__)
def strfts(ts, format='%d/%m/%Y %H:%M'):
return datetime.fromtimestamp(ts).strftime(format)
class Updater(threading.Thread):
def __init__(self, timeout, lease_offset=0, logger=logger, *a, **kw):
self.timeout = timeout
self.lock = threading.Lock()
self.lease_offset = lease_offset
self.logger = logger
self.active = {}
threading.Thread.__init__(self, *a, **kw)
self.daemon = True
def purge_stale(self):
now = time()
for addr, (atime, ip, name) in list(self.active.items()):
if now - atime > self.timeout:
del self.active[addr]
def get_active_devices(self):
with self.lock:
self.purge_stale()
r = dict(self.active)
return r
def get_device(self, ip):
active_devices = iter(self.get_active_devices().items())
for hwaddr, (atime, dip, name) in active_devices:
if ip == dip:
return hwaddr, name
return None, None
def update(self, hwaddr, atime=None, ip=None, name=None):
if atime:
atime -= self.lease_offset
else:
atime = time()
with self.lock:
if hwaddr not in self.active or self.active[hwaddr][0] < atime:
self.active[hwaddr] = (atime, ip, name)
self.logger.info('updated %s with atime %s and ip %s',
hwaddr, strfts(atime), ip)
class CapUpdater(Updater):
def __init__(self, cap_file, *a, **kw):
self.cap_file = cap_file
Updater.__init__(self, *a, **kw)
def run(self):
while True:
try:
with open(self.cap_file, 'r', buffering=0) as f:
self.logger.info('Updater ready on cap file %s',
self.cap_file)
lines = [l.strip() for l in f.read().split('\n')]
for hwaddr in lines:
if hwaddr:
self.update(hwaddr)
self.logger.warning('Cap file %s closed, reopening',
self.cap_file)
except Exception as e:
self.logger.error('Updater got an exception:\n' +
traceback.format_exc(e))
sleep(10.0)
class MtimeUpdater(Updater):
def __init__(self, lease_file, *a, **kw):
self.lease_file = lease_file
self.position = 0
self.last_modified = 0
Updater.__init__(self, *a, **kw)
def file_changed(self, f):
"""Callback on changed lease file
Args:
f: Lease file. File offset can be used to skip already parsed lines.
Returns: New byte offset pointing after last parsed byte.
"""
return f.tell()
def _trigger_update(self):
self.logger.info('Lease file changed, updating')
with open(self.lease_file, 'r') as f:
f.seek(self.position)
self.position = self.file_changed(f)
def run(self):
"""Periodicaly check if file has changed
From ISC DHCPD manual:
New leases are appended to the end of the dhcpd.leases file. In
order to prevent the file from becoming arbitrarily large, from
time to time dhcpd creates a new dhcpd.leases file from its in-core
lease database. Once this file has been written to disk, the old
file is renamed dhcpd.leases~, and the new file is renamed
dhcpd.leases.
"""
while True:
try:
stat = os.stat(self.lease_file)
mtime = stat.st_mtime
size = stat.st_size
if size < self.position:
self.logger.info('leases file changed - reseting pointer')
self.position = 0
try:
# checking if DHCPD performed cleanup
# cleanup during operation seems to be currently broken
# on customs so this could never execute
purge_time = os.stat(self.lease_file + '~').st_mtime
if purge_time > self.last_modified:
self.logger.info('leases file purged - reseting pointer')
self.position = 0
except FileNotFoundError:
pass
if mtime > self.last_modified:
self._trigger_update()
self.last_modified = mtime
sleep(5.0)
except Exception as e:
self.logger.exception('Exception in updater')
sleep(10.0)
class DnsmasqUpdater(MtimeUpdater):
def file_changed(self, f):
raise NotImplementedError(
"This was not tested after adding differential update")
for line in f:
ts, hwaddr, ip, name, client_id = line.split(' ')
self.update(hwaddr, int(ts), ip, name)
return f.tell()
class DhcpdUpdater(MtimeUpdater):
def file_changed(self, f):
lease = False
# for use by next-line logic
ip = None
hwaddr = None
atime = None
offset = f.tell()
while True:
# using readline because iter(file) blocks file.tell usage
line = f.readline()
if not line:
return offset
line = line.split('#')[0]
cmd = line.strip().split()
if not cmd:
continue
if lease:
field = cmd[0]
if(field == 'starts'):
dt = datetime.strptime(' '.join(cmd[2:]),
'%Y/%m/%d %H:%M:%S;')
atime = mktime(dt.utctimetuple())
if(field == 'client-hostname'):
name = cmd[1][1:-2]
if(field == 'hardware'):
hwaddr = cmd[2][:-1]
if(field.startswith('}')):
offset = f.tell()
lease = False
if hwaddr is not None and atime is not None:
self.update(hwaddr, atime, ip, name)
hwaddr, atime = None, None
elif cmd[0] == 'lease':
ip = cmd[1]
name, hwaddr, atime = [None] * 3
lease = True
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