Resolved uses wrong dns

[alex-eri]

systemd version the issue has been seen with

255.4-1ubuntu8

Used distribution

Ubuntu 24.04

Linux kernel version used

6.8.0-31-generic

CPU architectures issue was seen on

x86_64

Component

systemd-resolved

Expected behaviour you didn't see

Expected resolved use dns of connection with best metric. Or try these first with fallback to other DNS on not existed domains.

Unexpected behaviour you saw

Resolved uses random DNS. Even under "# Too many DNS servers configured, the following entries may be ignored." line

Steps to reproduce the problem

I have 3-4 connections active, but one have internet. enx* has no internet and hotspot redirecting DNS. It returns 172.31.... addresses.

Global
           Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
    resolv.conf mode: stub
  Current DNS Server: 10.10.1.64
         DNS Servers: 10.10.1.64 10.10.1.34
Fallback DNS Servers: 77.88.8.8
          DNS Domain: ivjh.ru

Link 7 (bridge0)
    Current Scopes: DNS
         Protocols: -DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 10.10.1.64
       DNS Servers: 10.10.1.64 10.10.1.34
        DNS Domain: example.com

Link 9 (enp3s0.6)
    Current Scopes: DNS
         Protocols: +DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 10.10.1.64
       DNS Servers: 10.10.1.64 10.10.1.34
        DNS Domain: example.com

Link 13 (docker0)
    Current Scopes: none
         Protocols: -DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported

Link 127 (enxbae9a5b3eeab)
    Current Scopes: DNS
         Protocols: +DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 192.168.9.1
       DNS Servers: 192.168.9.1

Link 128 (enx86ee24099007)
    Current Scopes: DNS
         Protocols: +DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 192.168.8.1
       DNS Servers: 192.168.8.1

default via 10.10.6.1 dev enp3s0.6 proto dhcp src 10.10.6.136 metric 400 
default via 192.168.8.1 dev enx86ee24099007 proto dhcp src 192.168.8.102 metric 20100 
default via 192.168.9.1 dev enxbae9a5b3eeab proto dhcp src 192.168.9.100 metric 20101 
10.10.6.0/24 dev enp3s0.6 proto kernel scope link src 10.10.6.136 metric 400 
10.99.99.0/24 dev bridge0 proto kernel scope link src 10.99.99.182 metric 425 
192.168.8.0/24 dev enx86ee24099007 proto kernel scope link src 192.168.8.102 metric 100 
192.168.9.0/24 dev enxbae9a5b3eeab proto kernel scope link src 192.168.9.100 metric 101 
192.168.117.0/24 dev bridge0 proto static scope link metric 425 

Additional program output to the terminal or log subsystem illustrating the issue

No response

[poettering]

You have not specified any routing domains, hence resolved will send to all configured interfaces simultaneously, and use the first positive or last negative reply.

See "PROTOCOLS AND ROUTING" section in systemd-resolved man page.