https://syzkaller.appspot.com/bug?extid=d19060a65721eb432a72
shows that after a panic if_downall() tries to send routing
messages.  That panics again in knote locking.

Noone needs routing messages during panic reboot.

OK bluhm@

On Mon, Feb 05, 2024 at 09:09:36PM +0300, Vitaliy Makkoveev wrote:
> Index: sys/net/if.c
> ===================================================================
> RCS file: /cvs/src/sys/net/if.c,v
> retrieving revision 1.716
> diff -u -p -r1.716 if.c
> --- sys/net/if.c	6 Jan 2024 11:42:11 -0000	1.716
> +++ sys/net/if.c	5 Feb 2024 18:07:34 -0000
> @@ -1788,8 +1788,10 @@ if_linkstate(struct ifnet *ifp)
>  {
>  	NET_ASSERT_LOCKED();
>  
> -	rtm_ifchg(ifp);
> -	rt_if_track(ifp);
> +	if (panicstr != NULL) {
> +		rtm_ifchg(ifp);
> +		rt_if_track(ifp);
> +	}
>  
>  	if_hooks_run(&ifp->if_linkstatehooks);
>  }