flush_dns.py

#!/usr/bin/env python

# flush_dns.py

'''A handy script to flush dns cache for Linux/macOS/Windows.'''

import logging
from subprocess import Popen
from sys import platform
import psutil


def check_if_process_running(logger, process_name):
    '''Check for running processes matching process_name.'''

    # Iterate through running processes to find matching process_name.
    logger.debug('Checking for process: %s\n', process_name)
    for proc in psutil.process_iter():
        try:
            if process_name.lower() in proc.name().lower():
                return True
        except (psutil.NoSuchProcess, psutil.AccessDenied,
                psutil.ZombieProcess):
            pass
    return False


def setup_logger():
    '''Setup logging facility.'''
    logger = logging.getLogger()
    handler = logging.StreamHandler()
    logger.addHandler(handler)
    logger.setLevel(logging.DEBUG)

    return logger


def linux(logger):
    '''Linux specific.'''
    logger.debug('Running on Linux.\n')

    # Check for dnsmasq
    if check_if_process_running(logger, 'dnsmasq'):
        logger.debug('Flushing DNSMasq...')
        command = Popen(
            ['sudo', 'systemctl', 'restart', 'dnsmasq.service'])
        result = get_command_result(command)
        logger.debug('DNSMasq flush: %s\n', result)

    # Check for named
    if check_if_process_running(logger, 'named'):
        logger.debug('Flushing named...')
        command = Popen(
            ['sudo', 'systemctl', 'restart', 'named.service'])
        result = get_command_result(command)
        logger.debug('Bind flush: %s\n', result)

    # Check for nscd
    if check_if_process_running(logger, 'nscd'):
        logger.debug('Flushing nscd...')
        command = Popen(
            ['sudo', 'systemctl', 'restart', 'nscd.service'])
        result = get_command_result(command)
        logger.debug('NSCD flush: %s\n', result)

    # Check for systemd-resolved
    if check_if_process_running(logger, 'systemd-resolved'):
        logger.debug('Flushing systemd-resolved...')
        command = Popen(['sudo', 'systemd-resolve', '--flush-caches'])
        result = get_command_result(command)
        logger.debug('systemd-resolved flush: %s\n', result)


def macos(logger):
    '''macOS specific.'''
    logger.debug('Running on macOS.\n')

    # Check for mDNSResponder
    if check_if_process_running(logger, 'mDNSResponder'):
        logger.debug('Killing mDNSResponder')
        command = Popen(['sudo', 'killall', '-HUP', 'mDNSResponder'])
        result = get_command_result(command)
        logger.debug('Killing mDNSResponder: %s\n', result)

    # Check for mDNSResponderHelper
    if check_if_process_running(logger, 'mDNSResponderHelper'):
        logger.debug('Killing mDNSResponderHelper')
        command = Popen(['sudo', 'killall', 'mDNSResponderHelper'])
        result = get_command_result(command)
        logger.debug('Killing mDNSResponderHelper: %s\n', result)

    logger.debug('Running: dscacheutil -flushcache')
    command = Popen(['sudo', 'dscacheutil', '-flushcache'])
    result = get_command_result(command)
    logger.debug('Flushing dscacheutil: %s\n', result)


def windows(logger):
    '''Windows specific.'''
    command = Popen(['ipconfig', '/flushdns'])
    result = get_command_result(command)
    logger.debug('ipconfig /flushdns: %s\n', result)


def get_command_result(command):
    '''Wait for command to complete and return result.'''
    command.wait()
    if command.returncode != 0:
        result = 'Failed'
    else:
        result = 'Successful'

    return result


def dns_flush(logger):
    '''Flush DNS cache by platform.'''

    # Linux specific
    if platform in ['linux', 'linux2']:
        linux(logger)

    # macOS specific
    elif platform == 'darwin':
        macos(logger)

    # Windows specific
    elif platform == 'win32':
        windows(logger)


def main():
    '''Main execution.'''
    logger = setup_logger()
    dns_flush(logger)


if __name__ == '__main__':
    main()