Index: if_gre.c
===================================================================
RCS file: /cvs/src/sys/net/if_gre.c,v
retrieving revision 1.125
diff -u -p -r1.125 if_gre.c
--- if_gre.c	16 Oct 2018 03:00:27 -0000	1.125
+++ if_gre.c	16 Oct 2018 03:03:56 -0000
@@ -1103,11 +1103,9 @@ gre_input_key(struct mbuf **mp, int *off
 			goto decline;
 		}
 
-#if NBPFILTER > 0
-		bpf_af = AF_UNSPEC;
-#endif
-		input = gre_keepalive_recv;
-		break;
+		m_adj(m, hlen);
+		gre_keepalive_recv(ifp, m);
+		return (IPPROTO_DONE);
 
 	default:
 		goto decline;