protect pmf from network drivers that don't provide if_stop

[Brett Lymn <blymn%internode.on.net@localhost>]

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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