Complete DNS failure after frequent switching between WiFi and Mobile networks

This is still an issue for me on blokada 5.11.1

Anytime I switch between wifi and cell service, my data stops working (when blokada is on) until I deactivate blokada (it also works if I then just re-enable quickly). But this makes it unusable at this point!

Please let me know where I can send my logs to help fix the problem. Thanks!

We’ve had our phones stuck on version 4 after I’d submitted 2 sets of logs. I’m guessing it’s hard to fix as it seemed something that was being investigated early on.

Could a developer please let us know if you’re unable to diagnose or reproduce the problem? I can also get more logs if helpful.

Thank you in advance.

(As an aside I recently tried blokada on a iPad only to find it doesn’t even work with local DNS :frowning: and I can’t use version 4 there)

You mentioned the problem is happening in version 5.11.1. I first saw it on 5.10.1 and didn’t have any problems before that version, after the “network DNS” feature was added.

Given that local DNS is the main reason people aren’t using version 5, I imagine there’s been some change in this area. Is anyone familiar with the code able to look at diffs between 5.10.1 and before please?

For me exactly the same problem. I have a Pixel 3a (one with google, latest software (android 11) and one wihtout google, CalyxOS, also latest version). Because of this problem i removed version 5 months ago, in version 4 the problem exists only when using blokada+ with the VPN. This renders the VPN unusable, because it’s very annoying when you look at the phone and you think “umm … so calm for hours” and then deactivate blokada and hundres of messages arrive …

@PrintableCharacter do to know if there’s been any chance to address this issue yet? Should we be trying version 5 again please?

Unluckily all of this is hardly reproducible to us. You may want to give the newest v5 beta a try but I cannot guarantee you anything as of right now :confused:
If it still doesn’t work, please commence providing us with logs. Maybe we can narrow all that down in the future

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@PrintableCharacter Thanks I’ll retest it.

A few of us had asked if you needed more logs some time ago but you must have missed it, so I’ll be sure to mention your name next time.

Hello@blokada.org is always open for issue descriptions including logs :slight_smile:
We’ll have a look at all of them. It might take some time, you may not hear back from us due to the massive amount of information we receive but we surely try to figure things out. We’ll tell you as soon as we find something you could do to help us further :slight_smile:

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@PrintableCharacter thanks, but please remember at least two of us had sent logs and you hadn’t responded to say you needed more.
In fact you had suggested we go back to version 4. So we were waiting to see a release note stating this bug was fixed.

@PrintableCharacter I’ve just installed version 5 (after going down a research rabbit-hole when reading the warning for version 5 on F-Droid. Transparency is good, so is critical feedback if it helps improve the product overall!) and the problem still happens. Nothing has changed. I sent a log.

When trying to reproduce the problem I suggest you block all access to external DNS (including for DoH for your chosen DNS provider - mine was CloudFlare) with your router. This means you will quickly know when “network DNS” isn’t working.

After doing this and setting up Blokada 5 to prefer network DNS with DNS encryption off you should disable wifi on you smartphone. Load a new website, then re-enable wifi and test again.

Back to version 4 for me.

Can any of the other affected users please re-test version 5 and submit a log to hello@blokada.org ?

@Karol thank you for responding to my log submission. I’m now having more trouble reproducing the problem. I will try again at work where WiFi coverage and 4G coverage are both poor in places and my phone switches back and forth between them.

I’ll leave Blokada 5 on until it happens regularly again, then immediately send a fresh log.

I thought my last log was after it had happened so I’m sorry if there was too much “noise” in the log.

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@Karol Thank you again for responding to my log submission.

I’m happy to say that Blokada 5 seems is better than it was, although I do still have a DNS problem after switching between WiFi and mobile networks every few days.

In a perfect world I would have;

  • All WiFi networks not encrypt DNS
  • All WiFi networks “use DNS: Cloudflare (default)”
  • All WiFi networks “prefer network DNS”
    while the mobile network (or the “All networks” default) would stay as:
  • Encrypt DNS (default)
  • Use DNS: Cloudflare (default)

I suspect that the problem I see happens more often when Blokada is switching between a WiFi network without DNS encryption to a Mobile network with DNS encryption.

So as a compromise I have disabled DNS encryption for “All networks” and DNS is blocked rarely now.

Thank you for the tip about clicking on the blue number of Blocked ads and trackers on the front page of the Blokada 5 app. It has shown me that even with the compromised setings above (encrypted DNS disabled everywhere, “prefer network DNS” on WiFI) I sometimes am on a Mobile Network with “Use network DNS” still active.

So I believe there is still a problem here, but it happens less often if Encrypted DNS isn’t being switched on and off. I will try to capture a log straight after I see the problem happen and I have confirmed that I am on a Mobile Network with “Network DNS” in use.

Thanks again

Immediately after posting that, I switched off WiFi and was on a Mobile Network with “Network DNS” active still.
I disabled Blokada and re-enabled it, then it correctly switched to “Cloudflare”.

Is this a related issue to the problem I have reported with DNS being blocked totally when switching between WiFi and Mobile networks?

See the attached screen shot and note the 4G symbol is active in the top right, not the WiFi fan symbol.

Here are screenshots of my settings when that happened:



Yes that’s the problem!

As I had manually stopped and started Blokada it correctly switched over to using Cloudflare DNS while on a Mobile network.

Now when I switch back to WiFi it’s still on Cloudflare DNS, which is blocked on my LAN as only “network DNS” should be used. So DNS is no longer working and I have repeated the original problem.

EDIT: See screenshot below with WiFi fan active:

Summary

When “Network DNS” is set up for one class of network with a public DNS provider set up for the other, Blokada 5 (from F-Droid) incorrectly does not change DNS server reliably.

This can result in “Network DNS” being used where a public DNS provider is should be configured. (The opposite can happen too)

When the problem occurs Blokada must be deactivated and re-activated.

In my situation, Blokada 5 has only appeared more reliable because it was stuck on “Network DNS” even when I roamed on to a Mobile Network. The problem is exactly as I reported at the beginning and it seems likely that nothing has changed.

I’ve sent in another log and should be able to reproduce this regularly now.

Thank you again!

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For anyone affected by this, I’ve been having an email conversation with Karol and sent a number of logs. We’re working through the problem.

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Just want to say this appears to be happening to me as well, Galaxy Note 9… I’m on an island with sketchy cellular service and the house I’m in has crap wifi, my phone is jumping from crappy wifi to crappy cellular as I move around the house, after a few flip flops, DNS fails… Finally narrowed it down to Blokada after forgetting to re-enable it after rebooting, all the sudden the issue disappeared… I guess I’ll have to suffer through the rest of my vacation without Blokada :joy:

Very good! Thanks a lot and, please keep us informed whether there is going to be a solution.

Meanwhile, I have switched all family phones (all with the same problems) back to blokada version 4:
pixel 3a, pixel 4a, samsung note 9, samsung note 10

Blokada Version 4 just runs rock stable without any trouble!

I would only change back to version 5, when it’s finally matured and not causing these frequent internet connection interuptions and requirement of manual restarts…