How to query a nameserver running on a non-standard port number?

[johnnyutahh]

Does dnspython support something like the 4th line in the code snippet below? (To be clear: I doubt a nameservers_port member/field exists in Resolver()... and I did a tiny bit of searching in the docs, gave up quickly/lazily, and am posting my follow-on question here.)

import dns.resolver
my_resolver = dns.resolver.Resolver()
my_resolver.nameservers = ['127.0.0.1'] # localhost
my_resolver.nameservers_port = ['5454'] # arbitrary, non-port-53 port number

[rthalley]

You can use the "port" attribute of the resolver to set the port for all nameservers, or the nameserver_ports dictionary to specify a port for a particular nameserver. See https://dnspython.readthedocs.io/en/latest/resolver-class.html for more

[johnnyutahh]

Excellent, this resolve my issue, thanks @rthalley !

A code example, for my reference:

import dns.resolver

# Create a resolver object and specify the alternative port (in this example, port 5353)
resolver = dns.resolver.Resolver()
resolver.port = 5353

# Use the resolver object to perform a DNS query
answers = resolver.query('example.com', 'A')

[johnnyutahh]

A non-default resolver.port is not yet working for me. A slight variant of the following script/session works when querying a non-authoritative DNS server on port 53, but once I query the dnsmasq -a 127.0.0.1 -p 553 server (which is started in the following script), dnspython appears to not respect the resolver.port = 553... or is something else wrong?

What if anything am I doing wrong here? (Script + session at gist below.) Am I possibly running dnsmasq incorrectly or configuring my dnspython client incorrectly... or both?

https://gist.githubusercontent.com/johnnyutahh/b9b651bce677a3769fe1583efccefa11/raw

[rthalley]

This seems to be a dnsmasq thing. Dnspython is doing the right thing. I tried to do what you are doing, both with dnspython and dig, and it did not work with dnsmasq when run as you run it. However, if I ran dnsmasq in debugging mode ("-d") or I told it to switch to user root instead of nobody with "-u root" then it worked. My config file was in /root. My guess is that in daemon mode dnsmasq is chrooting to the specified user's home directory, and thus unable to find the hosts file when run as you were running it.

[johnnyutahh]

Big thanks (again) @rthalley -- your note enabled me to focus on dnsmasq debugging and provided helpful tips on how to do so. I have my script working now, and it was indeed a dnsmasq-configuration correction that solved it. dnspython worked perfectly.

For reference: the things (I think) I discovered needed changing/adding to make dnsmasq work beyond the config I shared in the gist above:

1. add --no-resolv (to avoid dns-upstream-lookup name collisions)
2. add a full path to the host records -H
3. run as -some- user. my username or root both worked; dnsmasq process is owned by 'nobody' user if -u is not supplied, and for this "local, autonomous" server config, even if a full path is provided for the host records file with -H, for some reason dnsmasq process "owned by nobody" breaks the lookup (I guess...?) at least in my test environment which I share below.

Thanks again for your super-timely and helpful support!

[johnnyutahh]

fyi. Here's an updated script + session showing all the fixes, details, etc:

https://gist.githubusercontent.com/johnnyutahh/4d64d2d5927a6f0569c64a345a3f3e78/raw/