DNS Not working in Vivaldi; works in Firefox

abudden

I have an internal DNS server on my network. I use this partly to get round a limitation of my ADSL modem - if I access the public IP address of my modem from inside the network, it rejects the connection. To get round this, I have a local DNS server, which publishes the internal IP addresses of the internal server when you access the external DNS name.

That's all worked perfectly for ages, but something has changed recently that's stopped it working in Vivaldi (and Chrome). There was an IP address change (subnet mask changing from 192.168.0.* to 192.168.3.*), but that's been updated in the DNS server and Firefox picks up the new address with no problems, so I don't know why that would have broken Vivaldi.

Vivaldi (and Chrome) just sit there waiting for a response and then tell me it's not working ("This site can't be reached"). I can't check what IP address Vivaldi is using as the developer tools only tell you the IP address after a response is received (which obviously it isn't). All I can do is try Chrome (which does the same as Vivaldi) and Firefox, which works perfectly.

nslookup gives the right address.

I've checked through the options in Vivaldi and the only DNS one I could find was the option to use Google's DNS service - that option is disabled. I've tried flushing the DNS cache by going to to vivaldi://net-internals/#dns and clicking Clear host cache (which seemingly does nothing - no confirmation or anything). I've also flushed socket pools in case that helped. I've rebooted the PC a couple of times too.

This is on Windows 10,

Can anyone suggest what I might be able to do to get this working short of ditching Vivaldi and using Firefox instead?

Pathduck

@abudden Hello, welcome to the Vivaldi Community

What I suspect is that DNS over HTTPS (DoH) was enabled by default in the underlying Chromium engine with the latest version. This causes the browser to use one of the secure DNS server providers, effectively overriding your local DNS server.

Have a look at the Chromium settings: chrome://settings/security and check if "Use Secure DNS" is set.

You can also see this by examining network traffic (WireShark for instance), or using a tool like DNS Query Sniffer or others.
https://www.nirsoft.net/utils/dns_query_sniffer.html
https://www.nirsoft.net/utils/smsniff.html
https://www.nirsoft.net/utils/network_traffic_view.html

You should be able to see requests to for instance 8.8.8.8 (Google) or 1.1.1.1 (Cloudflare). Personally I think it's a horrible idea to give responsibility for DNS resolution to huge foreign corporations so I've turned it off.

However, Chromium will look at your current network configuration to see if your current provider supports DoH and then use that, so in your case it's not 100% certain this is what's happening, as you'd need to already have a supported provider configured.

abudden

@Pathduck Thank you! That was it. It's working again now.

Pathduck

@abudden Good to hear

I'm interested in how Vivaldi (actually, Chromium) would know what provider to use. AFAIK if it doesn't find one it will fall back to using regular DNS.

Did you have something like Google or Cloudflare DNS set up in your system? I presume your primary DNS is set to your local DNS server, but what is your secondary? You don't have to answer if you don't want to, I'm just curious how the browser knows how to change to one of the DoH providers.

I believe these are the current supported providers:

If it finds you're not using one of these it should fallback.

abudden

@Pathduck

In the TP-Link Deco (wifi mesh thingies) set-up I've got 8.8.8.8 (google) as the secondary DNS, so that's probably what's happening. In an ideal world I wouldn't need it, but I wanted to make sure the general network would keep working if the server went down for any reason.

In practice it's been useful again and again and again as the TP-Link Deco wifi things have a really annoying bug where every time they reboot (or, interestingly, the ADSL modem reboots), they pick a different subnet (192.168.0.* then 192.168.3.*, then 192.168.68.* etc). I've got a load of devices set to always have the same IP address, but that only seems to fix the last part of the IP address. Every time the Deco wifi things reboot, I have to completely reconfigure the DNS server and change the DNS server address in the Deco set-up.

As a result of this, there are often periods while I'm getting everything set up again that it's nice to have a fallback DNS server so that other stuff can keep working.

I've reported this to TP-Link but to say that they were unhelpful would be an understatement.

Pathduck

@abudden OK thanks for that, confirms my suspicion on how it detects what provider to use

That bug sounds really annoying, surely the company should fix it and release a firmware update?

BTW maybe you can use the Hosts file to add your external IP instead of using a dedicated DNS server, unless you have a lot of hosts to manage?

abudden

@Pathduck I'd like to think they'd release a firmware update, but I haven't managed to get them to acknowledge the problem - "it works fine if you factory reset and don't change any of the default settings". Okay, but that doesn't help as I don't then have custom DNS or any static IPs!

Using a hosts file doesn't help unfortunately as I need the address to be available to several PCs and also my Android phone (one of the services on the server is nextcloud which I use to automatically backup the phone - it's not much use if it only works when I'm away from home!)