[PLUG] DNS weirdness on Pop OS

David Fleck dcfleck at protonmail.ch
Thu Jan 2 01:54:27 UTC 2025


Thanks a lot for the ideas.

The box is definitely wifi-only. ping and traceroute output seems similar between the PopOS and SUSE machines, though slower on the PopOS generally. Some of the traceroute hops are not identical, but they end up at the same place. 

I'll try your other suggestions tomorrow, if I get the time.

Thanks again-

--
- David Fleck


On Wednesday, January 1st, 2025 at 6:50 PM, Russell Senior <russell at personaltelco.net> wrote:

> These are just random ideas:
> 
> * how is your laptop connected? could it be that it's on ethernet AND wifi?
> 
> * does ping or tcptraceroute to the same domain names behave normally?
> 
> * could it be an ipv6 vs ipv4 issue? do your local interfaces have
> ipv4 and ipv6 addresses assigned? (try "ip a" and/or "ip -6 r")
> 
> * try live-booting some other distribution on the laptop and see if
> the same problems persist.
> 
> * rebooting the gateway router (and/or whatever access point you are
> connected to) can't hurt.
> 
> * some browsers do their own DNS resolution nowadays, using things
> like DNS over TLS or DNS over HTTPS, and don't use the normal
> system-level DNS.
> 
> * running tcpdump on your laptop as you experience the problem and
> then staring at the capture with wireshark might be illuminating, i.e.
> where is the delay happening? For weird personal reasons, I usually do
> this in two steps:
> 
> sudo tcpdump -s0 -w /tmp/capture.pcap -i <yourinterfacename>
> 
> (ctrl-C to exit)
> wireshark /tmp/capture.pcap
> 
> others might do the whole thing with wireshark, and that's fine too.
> 
> --
> Russell Senior
> russell at personaltelco.net
> 
> On Wed, Jan 1, 2025 at 2:37 PM David Fleck dcfleck at protonmail.ch wrote:
> 
> > I've got a System 76 laptop with Pop OS 22.04 LTS (essentially Ubuntu, as far as I can tell) installed. I've had it for almost exactly 2 years, and networking Just Worked until this past Sunday. That morning, I noticed that browsing to some web sites (but not others) became glacially slow, or timed out completely. No other machines in the house (OpenSUSE, Windows) were affected. I stepped away for a few hours, and things were back to normal, and stayed that way, until yesterday afternoon, when the same connection slowdown/failure happened again. Not all sites are affected. Some don't seem to be affected at all (e.g., Wikipedia); others resolve, but very slowly (speedtest.net); others simply time out (protonmail). Some will connect, but if they require authentication, the authentication step times out.
> > 
> > I've tried clearing browser caches, and uninstalling/reinstalling browsers (Brave & Chromium), to no avail.
> > 
> > I've tried shutting down systemd-resolved, because some internet reading makes me think that it is frequently blamed for this kind of behavior, but I don't see any difference with it shut off and an /etc/resolv.conf manually hacked into place, assuming I did it correctly:
> > sudo service systemd-resolved stop
> > sudo systemctl disable systemd-resolved
> > sudo systemctl mask systemd-resolved
> > sudo cp resolv.conf /etc/resolv.conf # various values tried for nameserver: 8.8.8.8, 192.168.1.1 (local router address, which is what all the other machines are using for this)
> > 
> > The problem is definitely confined to this one machine, so I am assuming that there's nothing wrong with my router or other parts of my home network.
> > 
> > Wondering if anyone has any ideas on debugging/ what to try next. It would be a pain to nuke the laptop and install OpenSUSE, but I have no particular love for Ubuntu if it doesn't Just Work, and currently I'm about 60% of the way to replacing it at the moment.
> > 
> > --
> > - David Fleck


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