[dnsdist] addDOHLocal has 'urls' parameter, but addDOH3Local has not?

[Marco Davids (SIDN)]

Hi Remi,

On Thu, 2 Oct 2025 10:40:38 +0200 Remi Gacogne via dnsdist wrote:

> It seemed to us that the URLs parameter, which can be used to configure 
> the HTTP paths dnsdist will accept DNS queries on, was causing a lot of 
> confusion, so we decided to just accept DNS queries on all paths for DoH3.

Got it and that makes sense. Maybe worth updating the docs to mention 
this important detail?

I never used that parameter to configure alternative paths for DNS 
queries though,
but merely for the redirect, because I thought it was needed, based on 
reading this:

https://mailman.powerdns.com/pipermail/dnsdist/2019-September/000685.html

> I don't think this is related to the urls parameter, wouldn't you rather 
> happen to have a response map [1][2] for DoH handling the redirect? 

Yes.

But isn't the urls parameter needed to make that work?

In my configuration I have this:

{ '/.well-known/security.txt', '/dns-query' }

When I leave out the '/.well-known/security.txt' part, the response map 
I defined stops working.

I guess that’s where the confusion on my part arose, but in the case of 
addDOH3Local,
where there is no longer a urls parameter things may be different.

So yes, Indeed the core of my question was the need for a response map 
feature.

> Response map support hasn't been implemented for DoH3 yet, and seems 
> there was no feature request for it in our tracker I just created it [3].

Oh, that's nice - many thanks!

I may have a suggestion for that as well:

Since newDOHResponseMapEntry accepts a regex I was wondering...

Wouldn't it be cool if we could reference the match from a regex (e.g. 
$1) in the content string, if at all possible to do?

That way, we could use the dynamic part of the URL (e.g. the token in an 
ACME challenge request)
in a response.

Like this for example:

`^/\.well-known/acme-challenge/([-_a-zA-Z0-9]+)$`

content string:

https://example.nl/.well-known/acme-challenge/$1

Perhaps there are other possible use cases as well.

Hope that makes sense.

-- 
Marco