On 10/09/17 23:25, Jason A. Donenfeld wrote:
> I just wrote the attached script, which will tell you all the
> processes that have an open netlink socket...
>
> There's a bit too much fluff in there on a desktop system, but I
> imagine the pi might help boil it down to a few candidates. Probably
> we'll determine it's an ifplugd/ifupdown.action thing, but we'll see.

Many thanks again for such great work. Here's the output of the 
netlistenerwho.sh program. It's awash with potential culprits!

   PID TTY      STAT   TIME COMMAND
     1 ?        Ss     2:35 /sbin/init
   128 ?        Ss     0:01 /lib/systemd/systemd-udevd
   770 ?        Ss     2:24 /sbin/dhcpcd -q -b
   783 ?        Ss     0:15 avahi-daemon: running [janus.local]
   840 ?        Ss     0:32 /lib/systemd/systemd-logind
   896 ?        Ss    10:19 /usr/sbin/ntpd -p /var/run/ntpd.pid -g -u 
107:112
   906 ?        S      0:02 /usr/sbin/dnsmasq -x 
/run/dnsmasq/dnsmasq.pid -u dnsmasq -r /run/dnsmasq/resolv.conf -7 
/etc/dnsmasq.
  1204 ?        Ss     0:00 /lib/systemd/systemd --user
18942 ?        Ss     0:00 /lib/systemd/systemd --user

I also made a great mistake earlier: the problematic system is the 
version of Raspbian based on begin *8* and /not/ *9*. Debian 9 works fine!

I've tweaked the /etc/network/interfaces file to have the line “iface 
wg0 inet manual” in it so we /shouldn't/ get DHCP running or anything…

I tried the nlmon trick but I got the response “RTNETLINK answers: 
Operation not supported” which isn't too helpful.

After some more playing I've found that running the wg-quick script's 
commands by hand works. But then, I'm /manually/ entering them and that 
affects timing.

I note you perform the ”ip link set wg0 up” /after/ the “ip address add 
192.168.2.3/32 dev wg0” and “ip link set mtu 1420 dev wg0”. /However, 
/the act of creating the interface with the “ip link add wg0 type 
wireguard” seems to trigger the ip up automatically. The log files give:

Sep 10 23:57:51 janus kernel: wireguard: WireGuard 0.0.20170907 loaded. 
See www.wireguard.com for information.
Sep 10 23:57:51 janus kernel: wireguard: Copyright (C) 2015-2017 Jason 
A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
Sep 10 23:57:51 janus ifplugd(wg0)[14109]: ifplugd 0.28 initializing.
Sep 10 23:57:51 janus ifplugd(wg0)[14109]: Using interface 
wg0/00:00:00:00:00:00
Sep 10 23:57:51 janus ifplugd(wg0)[14109]: Using detection mode: IFF_RUNNING
Sep 10 23:57:51 janus ifplugd(wg0)[14109]: Initialization complete, link 
beat detected.
Sep 10 23:57:52 janus ifplugd(wg0)[14109]: Executing 
'/etc/ifplugd/ifplugd.action wg0 up'.
Sep 10 23:57:52 janus ifplugd(wg0)[14109]: client: /sbin/ifup: interface 
wg0 already configured
Sep 10 23:57:52 janus ifplugd(wg0)[14109]: Program executed successfully.

Which could well be interesting. I manually ran ifdown then ifup on wg0 
and it /didn't/ lose its IP address.

Most perplexing!

Jim.