kern/56287: pmf_class_network_suspend in kern_pmf.c needs a KASSERT

[blymn2netbsd.org%internode.on.net@localhost]

>Number:         56287
>Category:       kern
>Synopsis:       pmf_class_network_suspend in kern_pmf.c needs an assert
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 30 22:10:00 +0000 2021
>Originator:     blymn%netbsd.org@localhost
>Release:        NetBSD 9.99.85
>Organization:
dis
>Environment:
System: NetBSD rover 9.99.85 NetBSD 9.99.85 (ROVER) #3: Wed Jun 30 16:50:40 ACST 2021 toor@rover:/usr/obj/sys/arch/amd64/compile.amd64/ROVER amd64
Architecture: x86_64
Machine: amd64
>Description:
	I have just committed a fix to kern_pmf.c to protect the
function pmf_class_network_suspend from calling a NULL if_stop which
would result in a kernel panic.  There are a bunch of usb wifi drivers
that do not set this function pointer.  Once the drivers are fixed the
printf in the function should be converted to a KASSERT to report
buggy drivers.
>How-To-Repeat:
	Try to sleep a machine with a urtwn wifi device attached, observe
the printf firing.
>Fix:
	Once the wifi drivers have been reworked, convert the printf to
a KASSERT.