use a macro for the default if_hdrlen, not a magic number

suggested by mpi@

diff --git a/sys/net/if_gre.c b/sys/net/if_gre.c
index 0f38d12..c61570c 100644 (file)
--- a/sys/net/if_gre.c
+++ b/sys/net/if_gre.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: if_gre.c,v 1.116 2018/02/27 06:16:23 dlg Exp $ */
+/*     $OpenBSD: if_gre.c,v 1.117 2018/02/27 06:46:00 dlg Exp $ */
 /*     $NetBSD: if_gre.c,v 1.9 1999/10/25 19:18:11 drochner Exp $ */
 
 /*
@@ -141,6 +141,8 @@ struct gre_h_wccp {
 
 #define GRE_WCCP 0x883e
 
+#define GRE_HDRLEN (sizeof(struct ip) + sizeof(struct gre_header))
+
 /*
  * GRE tunnel metadata
  */
@@ -492,7 +494,7 @@ gre_clone_create(struct if_clone *ifc, int unit)
        ifp = &sc->sc_if;
        ifp->if_softc = sc;
        ifp->if_type = IFT_TUNNEL;
-       ifp->if_hdrlen = 24; /* IP + GRE */
+       ifp->if_hdrlen = GRE_HDRLEN;
        ifp->if_mtu = GREMTU;
        ifp->if_flags = IFF_POINTOPOINT|IFF_MULTICAST;
        ifp->if_xflags = IFXF_CLONED;
@@ -555,7 +557,7 @@ mgre_clone_create(struct if_clone *ifc, int unit)
 
        ifp->if_softc = sc;
        ifp->if_type = IFT_L3IPVLAN;
-       ifp->if_hdrlen = 24; /* IP + GRE */
+       ifp->if_hdrlen = GRE_HDRLEN;
        ifp->if_mtu = GREMTU;
        ifp->if_flags = 0; /* it's not p2p, and can't mcast or bcast */
        ifp->if_xflags = IFXF_CLONED;
@@ -2735,7 +2737,7 @@ mgre_down(struct mgre_softc *sc)
        NET_ASSERT_LOCKED();
 
        CLR(sc->sc_if.if_flags, IFF_RUNNING);
-       sc->sc_if.if_hdrlen = 24; /* symmetry */
+       sc->sc_if.if_hdrlen = GRE_HDRLEN; /* symmetry */
 
        RBT_REMOVE(mgre_tree, &mgre_tree, sc);