This is not really a functional problem - syncthing is working great for me. However, I noticed that the system log on my device A is being spammed (about 1 entry per minute from 4 different devices) with entries along the lines of
INFO: Failed to exchange Hello messages with [...] at [...]: read tcp [DEVICE A]->[...]: read: connection reset by peer
The device IDs mentioned in these entries do not match any of the syncthing devices registered on device A. They do not appear at all in syncthing’s config.xml on device A. I figured out that they match the IDs of a couple of devices I previously shared some folders with on device B, which in turn shares some completely different folders with my device A. Neither A nor B are configured as introducers, and these devices are no longer registered on B, either. I originally had them registered on B via an introducer device on B. After removing them and the introducer on B I received an add request from them on B which I refused, so that’s why those devices do appear on the ignore list in B’s config.xml.
While it’s not a big issue, this piqued my curiosity. Do you happen to have any explanation for this weird behavior? How could those devices ever get to know my device A and how can I stop this log spam from happening?