protect pmf from network drivers that don't provide if_stop

[Brett Lymn]

Folks,

I turned up a fix I had put into my source tree a while back, I think at
the time the wireless driver (urtwn IIRC) did not set an entry for
if_stop.  This resulted in a kernel panic if you tried to sleep the
machine pmf_class_network_suspend would try to call a null if_stop.

I crafted the following to preserve my sanity, ok to commit?


Index: kern_pmf.c
===================================================================
RCS file: /cvsroot/src/sys/kern/kern_pmf.c,v
retrieving revision 1.45
diff -u -r1.45 kern_pmf.c
--- kern_pmf.c  11 Jun 2020 02:30:21 -0000      1.45
+++ kern_pmf.c  29 Jun 2021 01:27:01 -0000
@@ -892,11 +892,18 @@
        struct ifnet *ifp = device_pmf_class_private(dev);
        int s;
 
-       s = splnet();
-       IFNET_LOCK(ifp);
-       (*ifp->if_stop)(ifp, 0);
-       IFNET_UNLOCK(ifp);
-       splx(s);
+       if (ifp == NULL)
+               return true;
+
+       if ((*ifp->if_stop) == NULL)
+               printf("device %s has no if_stop\n", ifp->if_xname);
+       else {
+               s = splnet();
+               IFNET_LOCK(ifp);
+               (*ifp->if_stop)(ifp, 0);
+               IFNET_UNLOCK(ifp);
+               splx(s);
+       }
 
        return true;
 }

-- 
Brett Lymn
--
Sent from my NetBSD device.

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