[systemd-devel] systemd-resolved service ignores UseDNS=false

[Mikhail Morfikov]

I think I get it now. I have two interfaces that have different DNS
servers set -- bond0 and br_lxc. All of the LXC containers use my
router's DNS and everything else uses 127.0.2.1 . The config file for
the br_lxc interface looks like this:

[Match]
Name=br_lxc

[Network]
Description=LXC bridge configuration
DHCP=no
LinkLocalAddressing=no
Address=192.168.10.100/24
DNS=192.168.1.1
IPForward=true

Now the DNS option is empty, and the 192.168.1.1 resolver disappeared
from the /etc/resolv.conf file, and this is what I actually wanted, and
I've accidentally found the bug. :) 

I also changed the bond0 interface config file to the following one:

[Match]
Name=bond0

[Network]
Description=Bonded network
DHCP=ipv4
LinkLocalAddressing=no
DNS=
IPForward=true

[DHCP]
UseDNS=false
UseMTU=false
SendHostname=true
UseHostname=false
UseDomains=true
UseRoutes=true
CriticalConnection=true
RequestBroadcast=true

And in the /etc/systemd/resolved.conf file I set DNS=127.0.2.1 only,
and the two interfaces looks like this:
# networkctl status -a
...
● 6: br_lxc
   Link File: n/a
Network File: /etc/systemd/network/30-br_lxc-static.network
        Type: ether
       State: no-carrier (configured)
      Driver: bridge
  HW Address: 6e:7d:a5:7f:d6:06
         MTU: 1500
     Address: 192.168.10.100
              fe80::6c7d:a5ff:fe7f:d606

● 7: bond0
   Link File: n/a
Network File: /etc/systemd/network/50-bond0-dhcp.network
        Type: ether
       State: routable (configured)
      Driver: bonding
  HW Address: 3c:4a:92:00:4c:5b (Hewlett-Packard Company)
         MTU: 1500
     Address: 192.168.1.150
              fe80::3e4a:92ff:fe00:4c5b
     Gateway: 192.168.1.1 (TP-LINK TECHNOLOGIES CO.,LTD)
      Domain: mhouse.lh
      
I'm not sure, but shouldn't there be a DNS field pointing to the local
127.0.2.1 address that was set in /etc/systemd/resolved.conf file? It
looks like the DNS line in the above log shows only if the DNS= option
is set in a corresponding interface config file.
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