1859608 - Maybe change user's default DoH region when the user is roaming

Status: RESOLVED FIXED

(Core :: Networking: DNS, task, P2)

Description

[Kershaw Chang [:kershaw]]

We should consider switching the user's local DoH provider when we detect that the user is in a roaming state.

Comment 1

[Valentin Gosu [:valentin]]

For context, we have this code in DoHConfig:

https://searchfox.org/mozilla-central/rev/ac497ae160e664617e2f4286cdce3b03ef912d90/browser/components/doh/DoHConfig.sys.mjs#167-174

async loadRegion() {
  await new Promise(resolve => {
    let homeRegion = lazy.Preferences.get(`${kGlobalPrefBranch}.home-region`);
    if (homeRegion) {
      kRegionPrefBranch = `${kGlobalPrefBranch}.${homeRegion.toLowerCase()}`;
      resolve();
      return;
    }

So what we do is if we don't have the pref set, we compute the region store it as a pref, and use that from then forward.
Problem is if a user from Canada travels to Australia, they will still use the canadian DoH providers with additional latency.

A better approach would probably be to use the region stored as a pref, but also do one region check per session and store that in the pref, so at the next run you'll use the correct region and DoH providers.
Or maybe we can think of an even better design.

Comment 2

[Valentin Gosu [:valentin]]

Attachment: Bug 1859608 - Change the user's DoH region when that changes r=#necko

The DoHConfig now listens for region change notification and
saves the new region in a pref. On the next initialization of
the DoH config we will use the saved pref to update the doh
region even if the pref was already set.

This should also work for testing (manually setting the value of the
pref) as long as no region changes happen.

Comment 3

[Petr Špaček]

Could we get loud and clear notification when the config is automatically modified, please?

Comment 4

[Valentin Gosu [:valentin]]

(In reply to Petr Špaček from comment #3)

Could we get loud and clear notification when the config is automatically modified, please?

What do you mean?

Comment 5

[Petr Špaček]

Let me rephrase. If Firefox is switching to a different DoH provider automatically, I as an user want to know that it has happened.

Comment 6

[Valentin Gosu [:valentin]]

This only happens for users under the Default Protection (network.trr.mode = 0) setting in about:preferences#privacy
In that mode Firefox configures the DoH server automatically based on your region.
What this fix does is that if your original region was detected as US, upon travelling to Germany or Canada, Firefox would not keep using the default DoH settings for US.
This change does not affect users who selected Increased protection or Max protection, or Off. It would also not change anything if you manually set a custom DoH URL.

Comment 7

[Petr Špaček]

Aha! Thank you for clarification. That was not clear from the title "Maybe change user's local DoH provider when the user is roaming". Maybe stuff a word "default" somewhere to the title?

Thank you for your time.

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ce50950ce10b
Change the user's DoH region when that changes r=necko-reviewers,sunil,kershaw

Comment 9

[Norisz Fay [:noriszfay]]

Backed out for causing bc failures on browser_doorhangerUserReject.js

Backout link

Push with failures

Failure log / Failure log for TV

Comment 10

[BugBot [:suhaib / :marco]]

There is an r+ patch which didn't land and no activity in this bug for 2 weeks.
:valentin, could you have a look please?
If you still have some work to do, you can add an action "Plan Changes" in Phabricator.
For more information, please visit BugBot documentation.

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/fea9dbbad1ab
Change the user's DoH region when that changes r=necko-reviewers,sunil,kershaw

Comment 12

[Iulian Moraru]

https://hg.mozilla.org/mozilla-central/rev/fea9dbbad1ab