Index: head/sys/netinet6/ip6_gre.c
===================================================================
--- head/sys/netinet6/ip6_gre.c	(revision 334702)
+++ head/sys/netinet6/ip6_gre.c	(revision 334703)
@@ -1,138 +1,132 @@
 /*-
  * Copyright (c) 2014 Andrey V. Elsukov <ae@FreeBSD.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
 #include "opt_inet.h"
 #include "opt_inet6.h"
 
 #include <sys/param.h>
 #include <sys/lock.h>
 #include <sys/rmlock.h>
 #include <sys/systm.h>
 #include <sys/socket.h>
 #include <sys/sockio.h>
 #include <sys/mbuf.h>
 #include <sys/errno.h>
 #include <sys/kernel.h>
 #include <sys/queue.h>
 #include <sys/syslog.h>
 #include <sys/sysctl.h>
 #include <sys/malloc.h>
 
 #include <net/if.h>
 #include <net/if_var.h>
 #include <net/vnet.h>
 
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
 #ifdef INET
 #include <net/ethernet.h>
 #include <netinet/ip.h>
 #endif
 #include <netinet/ip_encap.h>
 #include <netinet/ip6.h>
 #include <netinet6/ip6_var.h>
 #include <netinet6/in6_var.h>
 #include <net/if_gre.h>
 
 VNET_DEFINE(int, ip6_gre_hlim) = IPV6_DEFHLIM;
 #define	V_ip6_gre_hlim		VNET(ip6_gre_hlim)
 
 SYSCTL_DECL(_net_inet6_ip6);
 SYSCTL_INT(_net_inet6_ip6, OID_AUTO, grehlim, CTLFLAG_VNET | CTLFLAG_RW,
     &VNET_NAME(ip6_gre_hlim), 0, "Default hop limit for encapsulated packets");
 
 static int
 in6_gre_encapcheck(const struct mbuf *m, int off, int proto, void *arg)
 {
 	GRE_RLOCK_TRACKER;
 	struct gre_softc *sc;
 	struct ip6_hdr *ip6;
 
 	sc = (struct gre_softc *)arg;
 	if ((GRE2IFP(sc)->if_flags & IFF_UP) == 0)
 		return (0);
 
 	M_ASSERTPKTHDR(m);
-	/*
-	 * We expect that payload contains at least IPv4
-	 * or IPv6 packet.
-	 */
-	if (m->m_pkthdr.len < sizeof(struct greip6) +
-#ifdef INET
-	    sizeof(struct ip))
-#else
-	    sizeof(struct ip6_hdr))
-#endif
-		return (0);
 
 	GRE_RLOCK(sc);
 	if (sc->gre_family == 0)
 		goto bad;
 
 	KASSERT(sc->gre_family == AF_INET6,
 	    ("wrong gre_family: %d", sc->gre_family));
 
 	ip6 = mtod(m, struct ip6_hdr *);
 	if (!IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_src, &ip6->ip6_dst) ||
 	    !IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_dst, &ip6->ip6_src))
 		goto bad;
 
 	GRE_RUNLOCK(sc);
 	return (128 * 2 + 32);
 bad:
 	GRE_RUNLOCK(sc);
 	return (0);
 }
 
 int
 in6_gre_output(struct mbuf *m, int af, int hlen)
 {
 	struct greip6 *gi6;
 
 	gi6 = mtod(m, struct greip6 *);
 	gi6->gi6_ip6.ip6_hlim = V_ip6_gre_hlim;
 	return (ip6_output(m, NULL, NULL, IPV6_MINMTU, NULL, NULL, NULL));
 }
 
 static const struct encap_config ipv6_encap_cfg = {
 	.proto = IPPROTO_GRE,
-	.min_length = sizeof(struct greip6) + sizeof(struct ip),
+	.min_length = sizeof(struct greip6) +
+#ifdef INET
+	    sizeof(struct ip),
+#else
+	    sizeof(struct ip6_hdr),
+#endif
 	.exact_match = (sizeof(struct in6_addr) << 4) + 32,
 	.check = in6_gre_encapcheck,
 	.input = gre_input
 };
 
 int
 in6_gre_attach(struct gre_softc *sc)
 {
 
 	KASSERT(sc->gre_ecookie == NULL, ("gre_ecookie isn't NULL"));
 	sc->gre_ecookie = ip6_encap_attach(&ipv6_encap_cfg, sc, M_WAITOK);
 	return (0);
 }