Index: sys/netgraph/ng_iface.c
===================================================================
--- sys/netgraph/ng_iface.c	(revision 316739)
+++ sys/netgraph/ng_iface.c	(working copy)
@@ -707,6 +707,12 @@ ng_iface_rcvdata(hook_p hook, item_p item)
 	}
 	random_harvest_queue(m, sizeof(*m), 2, RANDOM_NET_NG);
 	M_SETFIB(m, ifp->if_fib);
+
+	/* Clear any h/w csum flags as they are no longer valid. */
+	if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID)
+		m->m_pkthdr.csum_flags &= ~(CSUM_DATA_VALID |
+		    CSUM_PSEUDO_HDR);
+
 	netisr_dispatch(isr, m);
 	return (0);
 }