That is, until software on any of these devices start running their DNS queries through DoH directly, circumventing any DNS filtering at the perimeter.
This is what browsers, like Firefox, are likely to do as it stands today.
This is what browsers, like Firefox, are likely to do as it stands today.
Not to mention that where DNS was centrally managed before, now you have to change settings in each and every application that uses DoH to resolve names on the Internet.
(And then Google decides to do cert pinning on DoH, and suddenly you can only ever use 8.8.8.8 and 1.1.1.1, and if you want to change it, you need to buy Enterprise version of Chrome.)
Once OS vendors include support, your pihole can run a DoH server locally and all apps in your network use that DoH server.
Once there is a decent set of public/commercial DoH servers available, devs can simply follow the browsers' example: Directly embed a DoH client into the application and supply a hardwired list of URLs and certificates. To my knowledge, you cannot block that with pihole.
At least, if I were an app developer with financial interest in users not blocking my ads and trackers, this would seem like an obvious thing to do.
After all, glibc already did the hard work, why do it again?
(Oh and Applications with Ads were already able to do this, no need for firefox to do anything at all, it's just too complicated to be worth it)
> it's just too complicated to be worth it
That's the point. It's complicated and costly today if you have to design your own protocol, run your own DNS proxy and be the target of outrage if someone finds out.
It won't be if DoH normalizes application-specific DNS servers and provides an ecosystem with infrastructure and tooling for it.