Hi Jason,

Thanks for the very quick response.

It happens with both the August and September snapshots. Kernel 4.9.35+, 
Raspbian based on Debian 9 and nothing odd in dmesg.

However, your comment about network management daemons running is most 
interesting. Here's an extract from journalctl's output:

    Sep 09 21:31:28 janus ifplugd(wg0)[6903]: ifplugd 0.28 initializing.
    Sep 09 21:31:28 janus ifplugd(wg0)[6903]: Using interface
    wg0/00:00:00:00:00:00
    Sep 09 21:31:28 janus ifplugd(wg0)[6903]: Using detection mode:
    IFF_RUNNING
    Sep 09 21:31:28 janus ifplugd(wg0)[6903]: Initialization complete,
    link beat detected.
    Sep 09 21:31:28 janus ifplugd(wg0)[6903]: Executing
    '/etc/ifplugd/ifplugd.action wg0 up'.
    Sep 09 21:31:28 janus ifplugd(wg0)[6903]: client: Ignoring unknown
    interface wg0=wg0.
    Sep 09 21:31:29 janus ifplugd(wg0)[6903]: Program executed successfully.

So, something is triggering ifplug. I'm unsure what it might be doing 
and it /seems/ to imply that it's ignoring it but maybe this is the 
cause of the problem. wg0 is /not/ mentioned in /etc/network/interfaces 
so maybe ifup is trying to be helpful? There may well be a race 
condition between ifup and wg-quick…

Regards,

Jim.



On 10/09/17 13:44, Jason A. Donenfeld wrote:
> Hey Jim,
>
> That's very odd indeed. Do you have any other network management
> daemons running on there that could be interfering?
>
> Also: what snapshot version, kernel version, distribution, etc are you
> using? Anything odd in dmesg after running wg-quick?
>
> Regards,
> Jason