kern/53398: iwn0 off after X logout

[prlw1%cam.ac.uk@localhost]

>Number:         53398
>Category:       kern
>Synopsis:       iwn0 off after X logout
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 26 12:10:00 +0000 2018
>Originator:     Patrick Welche
>Release:        NetBSD-8.99.20/amd64
>Organization:
>Environment:
>Description:
I can't believe it, but it is reproducible:

login via xdm
fire up xterm
su
wpa_supplicant -B -i iwn0 -c...
dhcpcd -L4 iwn0

then logout (shutdown) from xdm

note the lack of network. (Originally I had ssh'd in, and the connection froze.)

open a terminal (ctl-alt-f1), login as root, and observe that iwn0 is down.

ifconfig iwn0 up

and all is well - the connection becomes active and a lease is acquired with no further intervention.
>How-To-Repeat:

>Fix: