--- a/sys/netgraph7/ng_source.c
+++ b/sys/netgraph7/ng_source.c
@@ ng_source_intr @@ (after obtaining packets from the driver queue,
 re-resolve instead of caching an unreferenced ifnet pointer)
-	if (sc->output_ifp != NULL) {
-		struct ifaltq_subqueue *ifsq =
-		    ifq_get_subq_default(&sc->output_ifp->if_snd);
+	ng_source_store_output_ifp(sc, sc->ifname);  /* re-resolve under
+	 * ifnet_lock; fails cleanly when the interface is gone */