Questions about MDNS

[OlivierGre]

Hi,
I have questions about MDNS:

In the syslog of my raspberry, I sometimes see (at the very beginning) a warning saying "DNSServiceProcessResult failed: Service Not Running (serviceRef = 0xea4580)". Is it a problem? After that there are MDNS messages saying that it has registered a new service so it seems to work.

When looking at the syslog, I'm wondering why the service is removed and registered again several times.

When looking at "sudo service mdns status", I see some "Unexpected conflicts".

Can you please help me to see which of those points should be fixed?

Thank you
Regards

pi@raspberrypi:~ $ cat /var/log/syslog | grep otbr-agent | grep -i MDNS
Sep 13 15:56:45 raspberrypi otbr-agent[838]: [WARN]-MDNS----: DNSServiceProcessResult failed: Service Not Running (serviceRef = 0xea4580)
Sep 13 15:56:45 raspberrypi otbr-agent[838]: [WARN]-MDNS----: Need to reconnect to mdnsd
Sep 13 15:57:03 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Registering new service OpenThread BorderRouter #95E5._meshcop._udp.local, serviceRef = (nil)
Sep 13 15:57:03 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Removing existing service OpenThread BorderRouter #95E5._meshcop._udp: outdated
Sep 13 15:57:03 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Removing service OpenThread BorderRouter #95E5._meshcop._udp
Sep 13 15:57:03 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Registering new service OpenThread BorderRouter #95E5._meshcop._udp.local, serviceRef = (nil)
Sep 13 15:57:05 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Received reply for service OpenThread BorderRouter #95E5._meshcop._udp., serviceRef = 0xd6b250
Sep 13 15:57:05 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Successfully registered service OpenThread BorderRouter #95E5._meshcop._udp.
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Removing existing service OpenThread BorderRouter #95E5._meshcop._udp: outdated
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Removing service OpenThread BorderRouter #95E5._meshcop._udp
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Registering new service OpenThread BorderRouter #95E5._meshcop._udp.local, serviceRef = (nil)
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Received reply for service OpenThread BorderRouter #95E5._meshcop._udp., serviceRef = 0xd6b250
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Successfully registered service OpenThread BorderRouter #95E5._meshcop._udp.
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Removing existing service OpenThread BorderRouter #95E5._meshcop._udp: outdated
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Removing service OpenThread BorderRouter #95E5._meshcop._udp
Sep 13 15:57:26 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Registering new service OpenThread BorderRouter #95E5._meshcop._udp.local, serviceRef = (nil)
Sep 13 15:57:27 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Received reply for service OpenThread BorderRouter #95E5._meshcop._udp., serviceRef = 0xd6b250
Sep 13 15:57:27 raspberrypi otbr-agent[830]: [INFO]-MDNS----: Successfully registered service OpenThread BorderRouter #95E5._meshcop._udp.


pi@raspberrypi:~ $ sudo service mdns status
● mdns.service
     Loaded: loaded (/etc/init.d/mdns; generated)
     Active: active (running) since Tue 2022-09-13 15:57:02 CEST; 7min ago
       Docs: man:systemd-sysv-generator(8)
    Process: 827 ExecStart=/etc/init.d/mdns start (code=exited, status=0/SUCCESS)
      Tasks: 1 (limit: 4915)
        CPU: 140ms
     CGroup: /system.slice/mdns.service
             └─829 /usr/sbin/mdnsd

Sep 13 16:02:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Received from 192.168.202.3:5353   22 3.202.168>
Sep 13 16:02:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Unexpected conflict discarding   21 3.202.168.1>
Sep 13 16:03:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Received from 2a02:8440:5240:26a6:e65f:1ff:fe54>
Sep 13 16:03:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Unexpected conflict discarding   21 4.F.7.7.4.5>
Sep 13 16:03:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Received from 192.168.202.3:5353   22 3.202.168>
Sep 13 16:03:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Unexpected conflict discarding   21 3.202.168.1>
Sep 13 16:04:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Received from 192.168.202.3:5353   22 3.202.168>
Sep 13 16:04:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Unexpected conflict discarding   21 3.202.168.1>
Sep 13 16:04:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Received from 192.168.202.3:5353   22 4.f.7.7.4>
Sep 13 16:04:34 raspberrypi mDNSResponder[829]: Default: mDNSCoreReceiveResponse: Unexpected conflict discarding   21 4.F.7.7.4.5>
lines 1-20/20 (END)

[superwhd]

Hi @OlivierGre,

When OTBR starts, the Thread state will change several times (disabled -> detached -> attached) so it needs to update the MeshCoP mDNS service accordingly to reflect the state. It's working well as long as the mDNS service can be discovered. Regarding the logs of mdns daemon, I think I saw it on my side sometimes, but I don't have an impression that it breaks the behavior.

[OlivierGre]

@superwhd Ok thanks for this information.