10.4/remove-if_gre-and-if_me-mtu-fix-up.diff

Don't automatically fix up MTU set by SIOCSIFMTU in if_gre(4) and if_me(4).
Backported from FreeBSD base r316699.

diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/net/if_gre.c freebsd-10.4/sys/net/if_gre.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/net/if_gre.c	2017-09-29 08:20:07.000000000 +0800
+++ freebsd-10.4/sys/net/if_gre.c	2020-04-06 13:18:07.012575000 +0800
@@ -86,9 +86,9 @@
 #include <net/if_gre.h>
 
 #include <machine/in_cksum.h>
-
 #include <security/mac/mac_framework.h>
-#define	GREMTU			1500
+
+#define	GREMTU			1476
 static const char grename[] = "gre";
 static MALLOC_DEFINE(M_GRE, grename, "Generic Routing Encapsulation");
 static VNET_DEFINE(struct mtx, gre_mtx);
@@ -173,7 +173,7 @@
 	GRE2IFP(sc)->if_softc = sc;
 	if_initname(GRE2IFP(sc), grename, unit);
 
-	GRE2IFP(sc)->if_mtu = sc->gre_mtu = GREMTU;
+	GRE2IFP(sc)->if_mtu = GREMTU;
 	GRE2IFP(sc)->if_flags = IFF_POINTOPOINT|IFF_MULTICAST;
 	GRE2IFP(sc)->if_output = gre_output;
 	GRE2IFP(sc)->if_ioctl = gre_ioctl;
@@ -231,7 +231,8 @@
 		 /* XXX: */
 		if (ifr->ifr_mtu < 576)
 			return (EINVAL);
-		break;
+		ifp->if_mtu = ifr->ifr_mtu;
+		return (0);
 	case SIOCSIFADDR:
 		ifp->if_flags |= IFF_UP;
 	case SIOCSIFFLAGS:
@@ -255,12 +256,6 @@
 	}
 	error = 0;
 	switch (cmd) {
-	case SIOCSIFMTU:
-		GRE_WLOCK(sc);
-		sc->gre_mtu = ifr->ifr_mtu;
-		gre_updatehdr(sc);
-		GRE_WUNLOCK(sc);
-		goto end;
 	case SIOCSIFPHYADDR:
 #ifdef INET6
 	case SIOCSIFPHYADDR_IN6:
@@ -549,7 +544,6 @@
 	} else
 		sc->gre_oseq = 0;
 	gh->gre_flags = htons(flags);
-	GRE2IFP(sc)->if_mtu = sc->gre_mtu - sc->gre_hlen;
 }
 
 static void
diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/net/if_gre.h freebsd-10.4/sys/net/if_gre.h
--- /var/archive3/public/freebsd-releng-10.4-src/sys/net/if_gre.h	2017-09-29 08:20:07.000000000 +0800
+++ freebsd-10.4/sys/net/if_gre.h	2020-04-06 13:17:16.811416000 +0800
@@ -69,7 +69,6 @@
 	uint32_t		gre_oseq;
 	uint32_t		gre_key;
 	uint32_t		gre_options;
-	uint32_t		gre_mtu;
 	u_int			gre_fibnum;
 	u_int			gre_hlen;	/* header size */
 	union {
diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/net/if_me.c freebsd-10.4/sys/net/if_me.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/net/if_me.c	2017-09-29 08:20:07.000000000 +0800
+++ freebsd-10.4/sys/net/if_me.c	2020-04-06 13:17:16.812215000 +0800
@@ -66,7 +66,7 @@
 #include <machine/in_cksum.h>
 #include <security/mac/mac_framework.h>
 
-#define	MEMTU			1500
+#define	MEMTU			(1500 - sizeof(struct mobhdr))
 static const char mename[] = "me";
 static MALLOC_DEFINE(M_IFME, mename, "Minimal Encapsulation for IP");
 static VNET_DEFINE(struct mtx, me_mtx);
@@ -187,7 +187,7 @@
 	ME2IFP(sc)->if_softc = sc;
 	if_initname(ME2IFP(sc), mename, unit);
 
-	ME2IFP(sc)->if_mtu = MEMTU - sizeof(struct mobhdr);
+	ME2IFP(sc)->if_mtu = MEMTU;;
 	ME2IFP(sc)->if_flags = IFF_POINTOPOINT|IFF_MULTICAST;
 	ME2IFP(sc)->if_output = me_output;
 	ME2IFP(sc)->if_ioctl = me_ioctl;
@@ -237,7 +237,7 @@
 	case SIOCSIFMTU:
 		if (ifr->ifr_mtu < 576)
 			return (EINVAL);
-		ifp->if_mtu = ifr->ifr_mtu - sizeof(struct mobhdr);
+		ifp->if_mtu = ifr->ifr_mtu;
 		return (0);
 	case SIOCSIFADDR:
 		ifp->if_flags |= IFF_UP;