[syncthing] Local Discovery only not working

[MuellerNicolas]

Which addon?
syncthing

Describe the bug
My Windows Machine (Syncthing Trayzor installed, connected via Wifi) was not able to find my Home Assistant Syncthing Device (Connect via LAN), when I turned off all "Connection" Options, except "Local Discovery" on both machines:

Connection options on both devices were set to default (Addresses: dynamic):

From my understanding the Home Assistant Syncthing was able to find the windows machine, but was unable to connect. Logs (XXXXXX-XXXXX-... is the device id of the windows instance):

2023-01-27 18:45:35 Resolved device XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX addresses: [quic://192.168.178.80:22000 quic://192.168.56.1:22000 tcp://192.168.178.80:22000 tcp://192.168.56.1:22000]
2023-01-27 18:45:35 Resolved device YYYYYYY-YYYYYYY-YYYYYYY-YYYYYYY-YYYYYYY-YYYYYYY-YYYYYYY-YYYYYYY addresses: []
2023-01-27 18:45:35 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX tcp://192.168.56.1:22000 prio 10
2023-01-27 18:45:35 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX tcp://192.168.178.80:22000 prio 10
2023-01-27 18:45:35 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX tcp://192.168.56.1:22000 error: dial tcp 192.168.56.1:22000: connect: network is unreachable
2023-01-27 18:45:45 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX tcp://192.168.178.80:22000 error: dial tcp 192.168.178.80:22000: i/o timeout
2023-01-27 18:45:45 failed to connect to XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX 10
2023-01-27 18:45:45 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX quic://192.168.178.80:22000 prio 100
2023-01-27 18:45:45 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX quic://192.168.56.1:22000 prio 100
2023-01-27 18:45:50 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX quic://192.168.56.1:22000 error: dial: timeout: no recent network activity
2023-01-27 18:45:50 dialing XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX quic://192.168.178.80:22000 error: dial: timeout: no recent network activity
2023-01-27 18:45:50 failed to connect to XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX 100

Windows didn't even found the address, log (ZZZZZZZ-ZZZZZZ-... is the device id of the Home Assistant instance):

2023-01-27 18:35:28 Resolved device ZZZZZZZ-ZZZZZZZ-ZZZZZZZ-ZZZZZZZ-ZZZZZZZ-ZZZZZZZ-ZZZZZZZ addresses: []
2023-01-27 18:35:28 Next connection loop in 1m0s
2023-01-27 18:36:28 Connection loop

Workaround:
When setting the address to the static ip-address of home assistant on the windows machine, both devices are able to find each other with local option: (the windows device on the HA GUI still using dynamic)

To Reproduce

1. Go to Actions -> Connections
2. Disable all checkboxes except "Local Discovery"
3. Save & Restart
4. Now formerly connected devices aren't able to connect to each other, using dynamic addresses.

Expected behavior
I would expect local discovery to work.
Maybe this has to do something with this issue:
https://superuser.com/questions/1364353/issue-with-local-discovery-of-devices-on-dockerized-syncthing
(setting --network=host on the docker run, but i'm not familiar with docker setup of syncthing in hassio...)

Screenshots

System

• Supervisor version: 2023.01.1
• Host system version: 9.4