Process incoming gre(4) keepalives early to avoid bpf seeing them.

The packet processing done after the protocol detection effectively
gets thrown away by the keepalive handling, so this saves some time,
and avoids confusing tcpdump on the interface. Keepalives the driver
transmits aren't made available for bpf, so taking it away from the
receive side is consistent.

discussed with and tested by markus@

1 files changed, 4 insertions, 6 deletions

diff --git a/sys/net/if_gre.c b/sys/net/if_gre.c
index 143db4e39c3..c43344368fb 100644
--- a/sys/net/if_gre.c
+++ b/sys/net/if_gre.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_gre.c,v 1.125 2018/10/16 03:00:27 dlg Exp $ */
+/*	$OpenBSD: if_gre.c,v 1.126 2018/10/18 01:36:26 dlg Exp $ */
 /*	$NetBSD: if_gre.c,v 1.9 1999/10/25 19:18:11 drochner Exp $ */
 
 /*
@@ -1103,11 +1103,9 @@ gre_input_key(struct mbuf **mp, int *offp, int type, int af,
 			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;