Mar 03 22:20:29 ~/gitrs/.../dns/client$ sudo ./test_autonomous_dnsmasq.py
running: dnsmasq -C /dev/null -a 127.0.0.1 -p 553 -H dnsmasq_records
dns query timed out
killing: dnsmasq -C /dev/null -a 127.0.0.1 -p 553 -H dnsmasq_records
Mar 03 22:20:46 ~/gitrs/.../dns/client$ cat dnsmasq_records
1.2.3.4  myhost5.tld
Mar 03 22:21:21 ~/gitrs/.../dns/client$ cat test_autonomous_dnsmasq.py
#!/usr/bin/env python3

##
## Temporarily start a local dns server to resolve dns names
## provided by a records file, then kill the server.
##
## ~Johnny, 2023-03-03
##

import psutil, dns.resolver, subprocess, sys

# specify constants/config

dns_name_to_resolve = 'myhost5.tld'
dns_record_type     = 'A'

dns_nameserver_cmd  = 'dnsmasq'
local_only_ipaddr   = '127.0.0.1'
local_only_port     = 553 # arbitrary number, hoping for no port-# collision
timeout_in_secs     = 2.0
records_file_path   = 'dnsmasq_records'
dnsmasq_cmd_list    = [dns_nameserver_cmd, '-C', '/dev/null', '-a', local_only_ipaddr, '-p', str(local_only_port), '-H', records_file_path]
dnsmasq_cmd_string  = ' '.join(dnsmasq_cmd_list)

def kill_local_dns_nameserver(error_if_does_not_exist = False):
    # psutil:
    # https://stackoverflow.com/a/4230226/605356
    for proc in psutil.process_iter():
        if (proc.name() == dns_nameserver_cmd):
            if (proc.cmdline() == dnsmasq_cmd_list):
                print ('killing: ' + dnsmasq_cmd_string)
                try:
                    proc.kill()
                except psutil.NoSuchProcess:
                    if error_if_does_not_exist:
                        print(dns_nameserver_cmd + ' kill: process not found')
                except psutil.AccessDenied:
                    print(dns_nameserver_cmd + ' kill: permission denied')
                except psutil.TimeoutExpired:
                    print(dns_nameserver_cmd + ' kill: timed out while waiting for process to terminate')
                except:
                    print(dns_nameserver_cmd + ' kill: general failure')

# start local-only dnsmasq

kill_local_dns_nameserver() # first make sure it's not running
print('running: ' + dnsmasq_cmd_string)
try:
    dnsmasq = subprocess.Popen(dnsmasq_cmd_list)
except:
    print('could not start: ' + dns_nameserver_cmd)
    sys.exit()
dnsmasq.wait()

# setup dns-client resolver

resolver             = dns.resolver.Resolver()
resolver.port        = local_only_port
resolver.nameservers = [local_only_ipaddr]
resolver.timeout     = timeout_in_secs
resolver.lifetime    = timeout_in_secs

# run dns_nameserver, print lookup/resolve, then kill dns_nameserver

if not dnsmasq.returncode:

    # manage timeout/lifetime:
    # https://stackoverflow.com/a/8989817/605356
    try:
        # resolve() replaces query():
        # https://stackoverflow.com/a/64754367/605356
       #response = resolver.query  (qname=dns_name_to_resolve, rdtype=dns_record_type)
        response = resolver.resolve(qname=dns_name_to_resolve, rdtype=dns_record_type)
        for rdata in response:
            print(dns_name_to_resolve + ': ' + str(rdata))
    except dns.resolver.Timeout:
        print('dns query timed out')

    # stop local-only dnsmasq
    kill_local_dns_nameserver(error_if_does_not_exist = True)
Mar 03 22:21:56 ~/gitrs/.../dns/client$
Mar 03 22:22:02 ~/gitrs/.../dns/client$ sw_vers
ProductName:	macOS
ProductVersion:	12.6.3
BuildVersion:	21G419
Mar 03 22:22:07 ~/gitrs/.../dns/client$ python3 --version
Python 3.11.2
Mar 03 22:22:12 ~/gitrs/.../dns/client$
Mar 03 22:22:14 ~/gitrs/.../dns/client$ pip3 install dnspython
Requirement already satisfied: dnspython in /opt/homebrew/lib/python3.11/site-packages (2.3.0)
Mar 03 22:22:21 ~/gitrs/.../dns/client$