[PLUG] DNS weirdness on Pop OS
Russell Senior
russell at personaltelco.net
Thu Jan 2 00:50:29 UTC 2025
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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