User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36

Steps to reproduce:

My preferences, when set to utilize TRR mode (2 or 3), no longer work in Nightly.

Last known good build:
https://download-installer.cdn.mozilla.net/pub/firefox/nightly/2020/01/2020-01-08-09-41-58-mozilla-central/firefox-74.0a1.en-US.mac.dmg

First known bad build:
https://download-installer.cdn.mozilla.net/pub/firefox/nightly/2020/01/2020-01-08-21-56-06-mozilla-central/firefox-74.0a1.en-US.mac.dmg

Actual results:

When attempting to access sites, it appears as though Firefox is making NO outbound calls to get the DNS. I've attempted to use Little Snitch to capture the packets, but opening a new window and going to a site yields zero traffic.

The domains I have in the TRR bypass list work fine.

The error message is the "There's an issue with the DNS" message. In the network inspector, the only call that's visible is "The connection used to fetch this resource is not secure"

Expected results:

I should be able to browse normally.

Thank you for the report.
We do have another regression from the same change, but this seems slightly different.
Could you help us with some logs? https://developer.mozilla.org/en-US/docs/Mozilla/Debugging/HTTP_logging

Sure thing. Here ya go. I picked a site I've never been to before. I had to remove a few lines pertaining to personally identifiable URLs, but the bulk is there.

https://pastebin.com/SwNKzLyR

For what it's worth I went through and re-hardened my FF config last night and after I was finished, even with TRR mode set, it didn't exhibit this behavior.

Ok I found the config that's causing the issue. When I have network.trr.bootstrapAddress set to "1.1.1.1", this bug is exhibited. When it's blank, it is not (eg everything works normally).

This also in exhibited if network.trr.uri is set to https://1.1.1.1/dns-query

Thanks for the info. From the logs it looks like this is a dupe of bug 1610836.

(In reply to mozillabugzillajj from comment #5)

Ok I found the config that's causing the issue. When I have network.trr.bootstrapAddress set to "1.1.1.1", this bug is exhibited. When it's blank, it is not (eg everything works normally).

This also in exhibited if network.trr.uri is set to https://1.1.1.1/dns-query

Starting with Firefox 74 setting the bootstrapAddress isn't mandatory anymore. This helps since 1.1.1.1 only works with mozilla.cloudflare-dns.com by accident. The correct IP is 104.16.248.249.