#!/usr/bin/env python3
+"""A caching layer around the kernel's network mapping between IPs and MACs"""
+
import datetime
import logging
import os
from typing import Any, Optional
+import warnings
+
+from overrides import overrides
import argparse_utils
from collect.bidict import BiDict
import config
import exec_utils
+import file_utils
import persistent
import string_utils
+import site_config
logger = logging.getLogger(__name__)
help='Where to cache the kernel ARP table',
)
cfg.add_argument(
- '--arp_cache_max_staleness',
+ '--arper_cache_max_staleness',
type=argparse_utils.valid_duration,
- default=datetime.timedelta(seconds=60 * 5),
+ default=datetime.timedelta(seconds=60 * 15),
metavar='DURATION',
- help='Max acceptable age of the kernel arp table cache'
+ help='Max acceptable age of the kernel arp table cache',
+)
+cfg.add_argument(
+ '--arper_min_entries_to_be_valid',
+ type=int,
+ default=site_config.get_config().arper_minimum_device_count,
+ help='Min number of arp entries to bother persisting.',
)
@persistent.persistent_autoloaded_singleton()
class Arper(persistent.Persistent):
- def __init__(self, cached_state: Optional[BiDict[str, str]] = None) -> None:
+ def __init__(self, cached_state: Optional[BiDict] = None) -> None:
self.state = BiDict()
if cached_state is not None:
logger.debug('Loading Arper map from cached state.')
self.state = cached_state
else:
logger.debug('No usable cached state; calling /usr/sbin/arp')
+ self.update_from_arp_scan()
+ self.update_from_arp()
+ if len(self.state) < config.config['arper_min_entries_to_be_valid']:
+ raise Exception(
+ f'Arper didn\'t find enough entries; only got {len(self.state)}.'
+ )
+
+ def update_from_arp_scan(self):
+ network_spec = site_config.get_config().network
+ try:
output = exec_utils.cmd(
- '/usr/sbin/arp -a',
- timeout_seconds=5.0
+ f'/usr/local/bin/arp-scan --retry=6 --timeout 350 --backoff=1.4 --random --numeric --plain --ignoredups {network_spec}',
+ timeout_seconds=10.0,
)
- for line in output.split('\n'):
- line = str(line, 'ascii')
- ip = string_utils.extract_ip_v4(line)
- mac = string_utils.extract_mac_address(line)
+ except Exception as e:
+ logger.exception(e)
+ return
+ for line in output.split('\n'):
+ ip = string_utils.extract_ip_v4(line)
+ mac = string_utils.extract_mac_address(line)
+ if (
+ ip is not None
+ and mac is not None
+ and mac != 'UNKNOWN'
+ and ip != 'UNKNOWN'
+ ):
+ mac = mac.lower()
+ logger.debug(f'ARPER: {mac} => {ip}')
+ self.state[mac] = ip
+
+ def update_from_arp(self):
+ try:
+ output = exec_utils.cmd('/usr/sbin/arp -a', timeout_seconds=10.0)
+ except Exception as e:
+ logger.exception(e)
+ return
+ for line in output.split('\n'):
+ ip = string_utils.extract_ip_v4(line)
+ mac = string_utils.extract_mac_address(line)
+ if (
+ ip is not None
+ and mac is not None
+ and mac != 'UNKNOWN'
+ and ip != 'UNKNOWN'
+ ):
mac = mac.lower()
- logger.debug(f' {mac} => {ip}')
+ logger.debug(f'ARPER: {mac} => {ip}')
self.state[mac] = ip
def get_ip_by_mac(self, mac: str) -> Optional[str]:
def get_mac_by_ip(self, ip: str) -> Optional[str]:
return self.state.inverse.get(ip, None)
- def save(self) -> bool:
- logger.debug(f'Persisting state to {config.config["arp_cache_location"]}')
- with open(config.config['arp_cache_location'], 'w') as wf:
- for (mac, ip) in self.state.items():
- mac = mac.lower()
- print(f'{mac}, {ip}', file=wf)
-
@classmethod
+ @overrides
def load(cls) -> Any:
+ cache_file = config.config['arper_cache_location']
if persistent.was_file_written_within_n_seconds(
- config.config['arp_cache_location'],
- config.config['arp_cache_max_staleness'].total_seconds(),
+ cache_file,
+ config.config['arper_cache_max_staleness'].total_seconds(),
):
- logger.debug(f'Loading state from {config.config["arp_cache_location"]}')
+ logger.debug(f'Loading state from {cache_file}')
cached_state = BiDict()
- with open(config.config['arp_cache_location'], 'r') as rf:
- for line in rd.readline():
+ with open(cache_file, 'r') as rf:
+ contents = rf.readlines()
+ for line in contents:
+ line = line[:-1]
+ logger.debug(f'ARPER:{cache_file}> {line}')
(mac, ip) = line.split(',')
mac = mac.strip()
mac = mac.lower()
ip = ip.strip()
cached_state[mac] = ip
- return Arper(cached_state)
+ if (
+ len(cached_state)
+ > config.config['arper_min_entries_to_be_valid']
+ ):
+ return cls(cached_state)
+ else:
+ msg = f'{cache_file} is invalid: only {len(cached_state)} entries. Deleting it.'
+ logger.warning(msg)
+ warnings.warn(msg, stacklevel=2)
+ os.remove(cache_file)
logger.debug('No usable saved state found')
return None
+
+ @overrides
+ def save(self) -> bool:
+ if len(self.state) > config.config['arper_min_entries_to_be_valid']:
+ logger.debug(
+ f'Persisting state to {config.config["arper_cache_location"]}'
+ )
+ with file_utils.FileWriter(
+ config.config['arper_cache_location']
+ ) as wf:
+ for (mac, ip) in self.state.items():
+ mac = mac.lower()
+ print(f'{mac}, {ip}', file=wf)
+ return True
+ else:
+ logger.warning(
+ f'Only saw {len(self.state)} entries; needed at least {config.config["arper_min_entries_to_be_valid"]} to bother persisting.'
+ )
+ return False
projects / python_utils.git / blobdiff