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#1 2024-03-27 14:01:54

vitorqb
Member
Registered: 2018-06-22
Posts: 11

DNS failing with systemd-resolved: "Using degraded feature set"

I have recently started to experience an issue with DNS resolution on my laptop. At random times DNS resolution will stop working (can't resolve any name, therefore most apps relying on network stop working).

Here are the relevant logs from journalctl. They are repeated hundreads of time:

Mar 27 13:44:40 vitorquintanilha systemd-resolved[439]: Using degraded feature set UDP instead of TCP for DNS server 192.168.0.1.
Mar 27 13:44:40 vitorquintanilha systemd-resolved[439]: Using degraded feature set UDP instead of TCP for DNS server 8.8.8.8#dns.google.

Full journalctl for 30min around the issue is here: https://pastebin.pl/view/53e7ede1

I'm using iwd + systemd-resolved

$ sudo systemctl status iwd systemd-resolved
● iwd.service - Wireless service
     Loaded: loaded (/usr/lib/systemd/system/iwd.service; enabled; preset: disabled)
     Active: active (running) since Wed 2024-03-27 14:38:05 CET; 14min ago
       Docs: man:iwd(8)
             man:iwd.config(5)
             man:iwd.network(5)
             man:iwd.ap(5)
   Main PID: 482 (iwd)
      Tasks: 1 (limit: 38155)
     Memory: 3.2M (peak: 3.6M)
        CPU: 31ms
     CGroup: /system.slice/iwd.service
             └─482 /usr/lib/iwd/iwd

● systemd-resolved.service - Network Name Resolution
     Loaded: loaded (/usr/lib/systemd/system/systemd-resolved.service; enabled; preset: enabled)
     Active: active (running) since Wed 2024-03-27 14:38:05 CET; 14min ago
       Docs: man:systemd-resolved.service(8)
             man:org.freedesktop.resolve1(5)
             https://www.freedesktop.org/wiki/Software/systemd/writing-network-configuration-managers
             https://www.freedesktop.org/wiki/Software/systemd/writing-resolver-clients
   Main PID: 440 (systemd-resolve)
     Status: "Processing requests..."
      Tasks: 1 (limit: 38155)
     Memory: 8.9M (peak: 10.2M)
        CPU: 240ms
     CGroup: /system.slice/systemd-resolved.service
             └─440 /usr/lib/systemd/systemd-resolved

systemd-resolved related config::

$ ls -lhs /etc/resolv.conf
0 lrwxrwxrwx 1 root root 39 May  4  2022 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf

$ systemd-analyze cat-config systemd/resolved.conf | sed '/^#/d'

[Resolve]
DNS=8.8.8.8#dns.google 8.8.4.4#dns.google 2001:4860:4860::8888#dns.google 2001:4860:4860::8844#dns.google
FallbackDNS=1.1.1.1#cloudflare-dns.com 9.9.9.9#dns.quad9.net 8.8.8.8#dns.google 2606:4700:4700::1111#cloudflare-dns.com 2620:fe::9#dns.quad9.net 2001:4860:4860::8888#dns.google
DNSSEC=no

iwd config

$ cat /etc/iwd/main.conf
[General]
EnableNetworkConfiguration=true

Some relevant info:

1. "sudo systemd restart iwd systemd-resolved" does NOT fix the issue
2. Full system restart DOES fix the issue
3. Doesn't happen all the time, but often (e.g. 1 every 2 hours)
4. Does not happen to all networks (only some of them)
5. When it happens, if I try to open the router admin page (http://192.168.0.1 in my case), I can't (it says page not found or something similar

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#2 2024-03-27 15:07:08

seth
Member
Registered: 2012-09-03
Posts: 53,130

Re: DNS failing with systemd-resolved: "Using degraded feature set"

DNS is UDP, that's not "degraded"

5. When it happens, if I try to open the router admin page (http://192.168.0.1 in my case), I can't (it says page not found or something similar
Mar 27 13:44:40 vitorquintanilha systemd-resolved[439]: Using degraded feature set UDP instead of TCP for DNS server 192.168.0.1.
Mar 27 13:35:23 vitorquintanilha kernel: wlan0: deauthenticated from ea:d0:f0:19:1e:a8 (Reason: 3=DEAUTH_LEAVING)
…
Mar 27 13:35:24 vitorquintanilha iwd[60675]: event: connect-info, ssid: LowiF716_5G, bss: 60:ce:86:d7:f7:1b, signal: -68, load: 7/255
Mar 27 13:35:24 vitorquintanilha iwd[60675]: event: state, old: autoconnect_quick, new: connecting (auto)
Mar 27 13:35:24 vitorquintanilha kernel: wlan0: authenticate with 60:ce:86:d7:f7:1b
Mar 27 13:35:24 vitorquintanilha kernel: wlan0: send auth to 60:ce:86:d7:f7:1b (try 1/3)
Mar 27 13:35:24 vitorquintanilha kernel: wlan0: authenticated
Mar 27 13:35:24 vitorquintanilha kernel: wlan0: associate with 60:ce:86:d7:f7:1b (try 1/3)

You're romaing from ea:d0:f0:19:1e:a8 to  60:ce:86:d7:f7:1b (LowiF716_5G) and the latter is apparently not your router.
https://wiki.archlinux.org/title/Iwd#iwd_keeps_roaming

What are the outputs of

resolvectl status
ip a
ip r
/etc/resolv.conf
dig google.conf

when things work as expected and when they break?
What is "LowiF716_5G"?

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#3 2024-03-27 15:49:35

vitorqb
Member
Registered: 2018-06-22
Posts: 11

Re: DNS failing with systemd-resolved: "Using degraded feature set"

Thanks for the help!

You're romaing from ea:d0:f0:19:1e:a8 to  60:ce:86:d7:f7:1b (LowiF716_5G) and the latter is apparently not your router.
...
What is "LowiF716_5G"?

My router exposes 2 networks, "LowiF716" and "LowiF716_5G". I guess a possibility is that iwd keeps jumping between them. I'll remove one of them to see if it helps. On a side-note, I have no issues on other laptop (MacOS) and on my mobile phone for both networks.

What are the outputs of ....

These is the output of all commands you asked when internet **is working as expected**: https://pastebin.pl/view/ba09efcc

If/when the error happens again I'll post the output of the commands here.

when things work as expected and when they break?

I can't figure a pattern. It always works after a system restart. It usually breaks after some time of usage (say 1 to 2h). I can't consistently reproduce it. At some point I thought it could be related with running `docker` commands, but I was not able to reproduce it.

I'll post updates here when/if it breaks again.

Last edited by vitorqb (2024-03-27 15:50:20)

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#4 2024-03-27 16:02:17

seth
Member
Registered: 2012-09-03
Posts: 53,130

Re: DNS failing with systemd-resolved: "Using degraded feature set"

The question mark was still inquiring the outputs wink

Right off the bat: https://wiki.archlinux.org/title/Docker#Configuring_DNS
If this happens frequently enough and you can live w/o docker for a while, disable docker.{service,socket} …

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#5 2024-03-27 21:23:13

Brocellous
Member
Registered: 2017-11-27
Posts: 146

Re: DNS failing with systemd-resolved: "Using degraded feature set"

vitorqb wrote:

When it happens, if I try to open the router admin page (http://192.168.0.1 in my case), I can't

That doesn't seem like a DNS issue though? Do you have any network connectivity during the event? Does `ping -n 192.168.0.1` succeed? Does `dig @192.168.0.1 -x 192.168.0.1`? sd-resolved is just trying to contact the dns server and getting no responses.

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