gre: Add kernel GRE support.

This implements the kernel portion of GRE on Linux.  It consists
of a backported module that provides the GRE capabilities of 2.6.32
plus bug fixes to kernels 2.6.18+.

9 files changed, 2010 insertions, 0 deletions

diff --git a/acinclude.m4 b/acinclude.m4
index e37a316df..e4fa5e621 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -111,6 +111,16 @@ AC_DEFUN([OVS_CHECK_VETH], [
   fi
 ])
 
+AC_DEFUN([OVS_CHECK_GRE], [
+  AC_MSG_CHECKING([whether to build gre module])
+  if test "$sublevel" -ge 18; then
+    AC_MSG_RESULT([yes])
+    AC_SUBST([BUILD_GRE], 1)
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
 AC_DEFUN([OVS_CHECK_LOG2_H], [
   AC_MSG_CHECKING([for $KSRC26/include/linux/log2.h])
   if test -e $KSRC26/include/linux/log2.h; then
@@ -153,6 +163,7 @@ AC_DEFUN([OVS_CHECK_LINUX26_COMPAT], [
                   [OVS_DEFINE([HAVE_PROTO_DATA_VALID])])
   OVS_CHECK_LOG2_H
   OVS_CHECK_VETH
+  OVS_CHECK_GRE
   if cmp -s datapath/linux-2.6/kcompat.h.new \
             datapath/linux-2.6/kcompat.h >/dev/null 2>&1; then
     rm datapath/linux-2.6/kcompat.h.new
diff --git a/datapath/linux-2.6/Makefile.main.in b/datapath/linux-2.6/Makefile.main.in
index 967e2f7bc..fd231e696 100644
--- a/datapath/linux-2.6/Makefile.main.in
+++ b/datapath/linux-2.6/Makefile.main.in
@@ -5,6 +5,7 @@ export top_srcdir = @abs_top_srcdir@
 export KSRC = @KBUILD26@
 export VERSION = @VERSION@
 export BUILD_VETH = @BUILD_VETH@
+export BUILD_GRE = @BUILD_GRE@
 
 include $(srcdir)/../Modules.mk
 include $(srcdir)/Modules.mk
diff --git a/datapath/linux-2.6/Modules.mk b/datapath/linux-2.6/Modules.mk
index 7892583c2..8d2f96966 100644
--- a/datapath/linux-2.6/Modules.mk
+++ b/datapath/linux-2.6/Modules.mk
@@ -47,3 +47,26 @@ dist_modules += veth
 build_modules += $(if $(BUILD_VETH),veth)
 veth_sources = linux-2.6/compat-2.6/veth.c
 veth_headers = 
+
+dist_modules += ip_gre
+build_modules += $(if $(BUILD_GRE),ip_gre)
+ip_gre_sources = \
+	linux-2.6/compat-2.6/ip_gre.c \
+	linux-2.6/compat-2.6/net_namespace-ip_gre.c
+ip_gre_headers = \
+	linux-2.6/compat-2.6/compat26.h \
+	linux-2.6/compat-2.6/include/linux/if.h \
+	linux-2.6/compat-2.6/include/linux/in.h \
+	linux-2.6/compat-2.6/include/linux/inetdevice.h \
+	linux-2.6/compat-2.6/include/linux/if_ether.h \
+	linux-2.6/compat-2.6/include/linux/ip.h \
+	linux-2.6/compat-2.6/include/linux/ipv6.h \
+	linux-2.6/compat-2.6/include/linux/netdevice.h \
+	linux-2.6/compat-2.6/include/linux/skbuff.h \
+	linux-2.6/compat-2.6/include/linux/tcp.h \
+	linux-2.6/compat-2.6/include/linux/types.h \
+	linux-2.6/compat-2.6/include/net/dst.h \
+	linux-2.6/compat-2.6/include/net/ipip.h \
+	linux-2.6/compat-2.6/include/net/netns/generic.h \
+	linux-2.6/compat-2.6/include/net/net_namespace.h \
+	linux-2.6/compat-2.6/include/net/route.h
diff --git a/datapath/linux-2.6/compat-2.6/ip_gre.c b/datapath/linux-2.6/compat-2.6/ip_gre.c
new file mode 100644
index 000000000..246e864e0
--- /dev/null
+++ b/datapath/linux-2.6/compat-2.6/ip_gre.c
@@ -0,0 +1,1877 @@
+/* ip_gre driver port to Linux 2.6.18 and greater */
+
+#include <linux/version.h>
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
+#define HAVE_NETDEV_STATS
+#endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24)
+#define HAVE_NETDEV_HEADER_OPS
+#endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,26)
+#define HAVE_NETDEV_NEEDED_HEADROOM
+#endif
+
+/*
+ *	Linux NET3:	GRE over IP protocol decoder.
+ *
+ *	Authors: Alexey Kuznetsov (kuznet@ms2.inr.ac.ru)
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ */
+
+#include <linux/capability.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <asm/uaccess.h>
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/in.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/if_arp.h>
+#include <linux/mroute.h>
+#include <linux/init.h>
+#include <linux/in6.h>
+#include <linux/inetdevice.h>
+#include <linux/igmp.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/etherdevice.h>
+#include <linux/if_ether.h>
+
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/protocol.h>
+#include <net/ipip.h>
+#include <net/arp.h>
+#include <net/checksum.h>
+#include <net/dsfield.h>
+#include <net/inet_ecn.h>
+#include <net/xfrm.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#ifdef CONFIG_IPV6
+#include <net/ipv6.h>
+#include <net/ip6_fib.h>
+#include <net/ip6_route.h>
+#endif
+
+#include "compat.h"
+#include "openvswitch/gre.h"
+
+#ifndef GRE_IOCTL_ONLY
+#include <net/rtnetlink.h>
+#endif
+
+/*
+   Problems & solutions
+   --------------------
+
+   1. The most important issue is detecting local dead loops.
+   They would cause complete host lockup in transmit, which
+   would be "resolved" by stack overflow or, if queueing is enabled,
+   with infinite looping in net_bh.
+
+   We cannot track such dead loops during route installation,
+   it is infeasible task. The most general solutions would be
+   to keep skb->encapsulation counter (sort of local ttl),
+   and silently drop packet when it expires. It is the best
+   solution, but it supposes maintaing new variable in ALL
+   skb, even if no tunneling is used.
+
+   Current solution: HARD_TX_LOCK lock breaks dead loops.
+
+
+
+   2. Networking dead loops would not kill routers, but would really
+   kill network. IP hop limit plays role of "t->recursion" in this case,
+   if we copy it from packet being encapsulated to upper header.
+   It is very good solution, but it introduces two problems:
+
+   - Routing protocols, using packets with ttl=1 (OSPF, RIP2),
+     do not work over tunnels.
+   - traceroute does not work. I planned to relay ICMP from tunnel,
+     so that this problem would be solved and traceroute output
+     would even more informative. This idea appeared to be wrong:
+     only Linux complies to rfc1812 now (yes, guys, Linux is the only
+     true router now :-)), all routers (at least, in neighbourhood of mine)
+     return only 8 bytes of payload. It is the end.
+
+   Hence, if we want that OSPF worked or traceroute said something reasonable,
+   we should search for another solution.
+
+   One of them is to parse packet trying to detect inner encapsulation
+   made by our node. It is difficult or even impossible, especially,
+   taking into account fragmentation. TO be short, tt is not solution at all.
+
+   Current solution: The solution was UNEXPECTEDLY SIMPLE.
+   We force DF flag on tunnels with preconfigured hop limit,
+   that is ALL. :-) Well, it does not remove the problem completely,
+   but exponential growth of network traffic is changed to linear
+   (branches, that exceed pmtu are pruned) and tunnel mtu
+   fastly degrades to value <68, where looping stops.
+   Yes, it is not good if there exists a router in the loop,
+   which does not force DF, even when encapsulating packets have DF set.
+   But it is not our problem! Nobody could accuse us, we made
+   all that we could make. Even if it is your gated who injected
+   fatal route to network, even if it were you who configured
+   fatal static route: you are innocent. :-)
+
+
+
+   3. Really, ipv4/ipip.c, ipv4/ip_gre.c and ipv6/sit.c contain
+   practically identical code. It would be good to glue them
+   together, but it is not very evident, how to make them modular.
+   sit is integral part of IPv6, ipip and gre are naturally modular.
+   We could extract common parts (hash table, ioctl etc)
+   to a separate module (ip_tunnel.c).
+
+   Alexey Kuznetsov.
+ */
+
+#ifndef GRE_IOCTL_ONLY
+static struct rtnl_link_ops ipgre_link_ops __read_mostly;
+static struct rtnl_link_ops ipgre_tap_ops __read_mostly;
+#endif
+static int ipgre_tunnel_init(struct net_device *dev);
+static void ipgre_tunnel_setup(struct net_device *dev);
+static void ipgre_tap_setup(struct net_device *dev);
+static int ipgre_tunnel_bind_dev(struct net_device *dev);
+
+#define HASH_SIZE  16
+
+static int ipgre_net_id;
+struct ipgre_net {
+	struct ip_tunnel *tunnels[4][HASH_SIZE];
+
+	struct net_device *fb_tunnel_dev;
+};
+
+/* Tunnel hash table */
+
+/*
+   4 hash tables:
+
+   3: (remote,local)
+   2: (remote,*)
+   1: (*,local)
+   0: (*,*)
+
+   We require exact key match i.e. if a key is present in packet
+   it will match only tunnel with the same key; if it is not present,
+   it will match only keyless tunnel.
+
+   All keysless packets, if not matched configured keyless tunnels
+   will match fallback tunnel.
+ */
+
+#define HASH(addr) (((__force u32)addr^((__force u32)addr>>4))&0xF)
+
+#define tunnels_r_l	tunnels[3]
+#define tunnels_r	tunnels[2]
+#define tunnels_l	tunnels[1]
+#define tunnels_wc	tunnels[0]
+
+static DEFINE_RWLOCK(ipgre_lock);
+
+/* Given src, dst and key, find appropriate for input tunnel. */
+
+static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
+					      __be32 remote, __be32 local,
+					      __be32 key, __be16 gre_proto)
+{
+	struct net *net = dev_net(dev);
+	int link = dev->ifindex;
+	unsigned h0 = HASH(remote);
+	unsigned h1 = HASH(key);
+	struct ip_tunnel *t, *cand = NULL;
+	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
+	int dev_type = (gre_proto == htons(ETH_P_TEB)) ?
+		       ARPHRD_ETHER : ARPHRD_IPGRE;
+	int score, cand_score = 4;
+
+	for (t = ign->tunnels_r_l[h0^h1]; t; t = t->next) {
+		if (local != t->parms.iph.saddr ||
+		    remote != t->parms.iph.daddr ||
+		    key != t->parms.i_key ||
+		    !(t->dev->flags & IFF_UP))
+			continue;
+
+		if (t->dev->type != ARPHRD_IPGRE &&
+		    t->dev->type != dev_type)
+			continue;
+
+		score = 0;
+		if (t->parms.link != link)
+			score |= 1;
+		if (t->dev->type != dev_type)
+			score |= 2;
+		if (score == 0)
+			return t;
+
+		if (score < cand_score) {
+			cand = t;
+			cand_score = score;
+		}
+	}
+
+	for (t = ign->tunnels_r[h0^h1]; t; t = t->next) {
+		if (remote != t->parms.iph.daddr ||
+		    key != t->parms.i_key ||
+		    !(t->dev->flags & IFF_UP))
+			continue;
+
+		if (t->dev->type != ARPHRD_IPGRE &&
+		    t->dev->type != dev_type)
+			continue;
+
+		score = 0;
+		if (t->parms.link != link)
+			score |= 1;
+		if (t->dev->type != dev_type)
+			score |= 2;
+		if (score == 0)
+			return t;
+
+		if (score < cand_score) {
+			cand = t;
+			cand_score = score;
+		}
+	}
+
+	for (t = ign->tunnels_l[h1]; t; t = t->next) {
+		if ((local != t->parms.iph.saddr &&
+		     (local != t->parms.iph.daddr ||
+		      !ipv4_is_multicast(local))) ||
+		    key != t->parms.i_key ||
+		    !(t->dev->flags & IFF_UP))
+			continue;
+
+		if (t->dev->type != ARPHRD_IPGRE &&
+		    t->dev->type != dev_type)
+			continue;
+
+		score = 0;
+		if (t->parms.link != link)
+			score |= 1;
+		if (t->dev->type != dev_type)
+			score |= 2;
+		if (score == 0)
+			return t;
+
+		if (score < cand_score) {
+			cand = t;
+			cand_score = score;
+		}
+	}
+
+	for (t = ign->tunnels_wc[h1]; t; t = t->next) {
+		if (t->parms.i_key != key ||
+		    !(t->dev->flags & IFF_UP))
+			continue;
+
+		if (t->dev->type != ARPHRD_IPGRE &&
+		    t->dev->type != dev_type)
+			continue;
+
+		score = 0;
+		if (t->parms.link != link)
+			score |= 1;
+		if (t->dev->type != dev_type)
+			score |= 2;
+		if (score == 0)
+			return t;
+
+		if (score < cand_score) {
+			cand = t;
+			cand_score = score;
+		}
+	}
+
+	if (cand != NULL)
+		return cand;
+
+	if (ign->fb_tunnel_dev->flags & IFF_UP)
+		return netdev_priv(ign->fb_tunnel_dev);
+
+	return NULL;
+}
+
+static struct ip_tunnel **__ipgre_bucket(struct ipgre_net *ign,
+		struct ip_tunnel_parm *parms)
+{
+	__be32 remote = parms->iph.daddr;
+	__be32 local = parms->iph.saddr;
+	__be32 key = parms->i_key;
+	unsigned h = HASH(key);
+	int prio = 0;
+
+	if (local)
+		prio |= 1;
+	if (remote && !ipv4_is_multicast(remote)) {
+		prio |= 2;
+		h ^= HASH(remote);
+	}
+
+	return &ign->tunnels[prio][h];
+}
+
+static inline struct ip_tunnel **ipgre_bucket(struct ipgre_net *ign,
+		struct ip_tunnel *t)
+{
+	return __ipgre_bucket(ign, &t->parms);
+}
+
+static void ipgre_tunnel_link(struct ipgre_net *ign, struct ip_tunnel *t)
+{
+	struct ip_tunnel **tp = ipgre_bucket(ign, t);
+
+	t->next = *tp;
+	write_lock_bh(&ipgre_lock);
+	*tp = t;
+	write_unlock_bh(&ipgre_lock);
+}
+
+static void ipgre_tunnel_unlink(struct ipgre_net *ign, struct ip_tunnel *t)
+{
+	struct ip_tunnel **tp;
+
+	for (tp = ipgre_bucket(ign, t); *tp; tp = &(*tp)->next) {
+		if (t == *tp) {
+			write_lock_bh(&ipgre_lock);
+			*tp = t->next;
+			write_unlock_bh(&ipgre_lock);
+			break;
+		}
+	}
+}
+
+static struct ip_tunnel *ipgre_tunnel_find(struct net *net,
+					   struct ip_tunnel_parm *parms,
+					   int type)
+{
+	__be32 remote = parms->iph.daddr;
+	__be32 local = parms->iph.saddr;
+	__be32 key = parms->i_key;
+	int link = parms->link;
+	struct ip_tunnel *t, **tp;
+	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
+
+	for (tp = __ipgre_bucket(ign, parms); (t = *tp) != NULL; tp = &t->next)
+		if (local == t->parms.iph.saddr &&
+		    remote == t->parms.iph.daddr &&
+		    key == t->parms.i_key &&
+		    link == t->parms.link &&
+		    type == t->dev->type)
+			break;
+
+	return t;
+}
+
+static struct ip_tunnel * ipgre_tunnel_locate(struct net *net,
+		struct ip_tunnel_parm *parms, int gretap, int create)
+{
+	struct ip_tunnel *t, *nt;
+	struct net_device *dev;
+	char name[IFNAMSIZ];
+	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
+
+	t = ipgre_tunnel_find(net, parms, gretap ? ARPHRD_ETHER : ARPHRD_IPGRE);
+	if (t || !create)
+		return t;
+
+	if (parms->name[0])
+		strlcpy(name, parms->name, IFNAMSIZ);
+	else
+		sprintf(name, "gre%%d");
+
+	dev = alloc_netdev(sizeof(*t), name, gretap ? ipgre_tap_setup
+						    : ipgre_tunnel_setup);
+	if (!dev)
+	  return NULL;
+
+	dev_net_set(dev, net);
+
+	if (strchr(name, '%')) {
+		if (dev_alloc_name(dev, name) < 0)
+			goto failed_free;
+	}
+
+	if (gretap)
+		random_ether_addr(dev->dev_addr);
+
+#ifndef GRE_IOCTL_ONLY
+	dev->rtnl_link_ops = gretap ? &ipgre_tap_ops : &ipgre_link_ops;
+#endif
+	nt = netdev_priv(dev);
+	nt->parms = *parms;
+
+	dev->mtu = ipgre_tunnel_bind_dev(dev);
+
+	if (register_netdevice(dev) < 0)
+		goto failed_free;
+
+	dev_hold(dev);
+	ipgre_tunnel_link(ign, nt);
+	return nt;
+
+failed_free:
+	free_netdev(dev);
+	return NULL;
+}
+
+static void ipgre_tunnel_uninit(struct net_device *dev)
+{
+	struct net *net = dev_net(dev);
+	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
+
+	ipgre_tunnel_unlink(ign, netdev_priv(dev));
+	dev_put(dev);
+}
+
+
+static void ipgre_err(struct sk_buff *skb, u32 info)
+{
+
+/* All the routers (except for Linux) return only
+   8 bytes of packet payload. It means, that precise relaying of
+   ICMP in the real Internet is absolutely infeasible.
+
+   Moreover, Cisco "wise men" put GRE key to the third word
+   in GRE header. It makes impossible maintaining even soft state for keyed
+   GRE tunnels with enabled checksum. Tell them "thank you".
+
+   Well, I wonder, rfc1812 was written by Cisco employee,
+   what the hell these idiots break standrads established
+   by themself???
+ */
+
+	struct iphdr *iph = (struct iphdr *)skb->data;
+	__be16	     *p = (__be16*)(skb->data+(iph->ihl<<2));
+	int grehlen = (iph->ihl<<2) + 4;
+	const int type = icmp_hdr(skb)->type;
+	const int code = icmp_hdr(skb)->code;
+	struct ip_tunnel *t;
+	__be16 flags;
+
+	flags = p[0];
+	if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
+		if (flags&(GRE_VERSION|GRE_ROUTING))
+			return;
+		if (flags&GRE_KEY) {
+			grehlen += 4;
+			if (flags&GRE_CSUM)
+				grehlen += 4;
+		}
+	}
+
+	/* If only 8 bytes returned, keyed message will be dropped here */
+	if (skb_headlen(skb) < grehlen)
+		return;
+
+	switch (type) {
+	default:
+	case ICMP_PARAMETERPROB:
+		return;
+
+	case ICMP_DEST_UNREACH:
+		switch (code) {
+		case ICMP_SR_FAILED:
+		case ICMP_PORT_UNREACH:
+			/* Impossible event. */
+			return;
+		case ICMP_FRAG_NEEDED:
+			/* Soft state for pmtu is maintained by IP core. */
+			return;
+		default:
+			/* All others are translated to HOST_UNREACH.
+			   rfc2003 contains "deep thoughts" about NET_UNREACH,
+			   I believe they are just ether pollution. --ANK
+			 */
+			break;
+		}
+		break;
+	case ICMP_TIME_EXCEEDED:
+		if (code != ICMP_EXC_TTL)
+			return;
+		break;
+	}
+
+	read_lock(&ipgre_lock);
+	t = ipgre_tunnel_lookup(skb->dev, iph->daddr, iph->saddr,
+				flags & GRE_KEY ?
+				*(((__be32 *)p) + (grehlen / 4) - 1) : 0,
+				p[1]);
+	if (t == NULL || t->parms.iph.daddr == 0 ||
+	    ipv4_is_multicast(t->parms.iph.daddr))
+		goto out;
+
+	if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
+		goto out;
+
+	if (time_before(jiffies, t->err_time + IPTUNNEL_ERR_TIMEO))
+		t->err_count++;
+	else
+		t->err_count = 1;
+	t->err_time = jiffies;
+out:
+	read_unlock(&ipgre_lock);
+	return;
+}
+
+static inline void ipgre_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)
+{
+	if (INET_ECN_is_ce(iph->tos)) {
+		if (skb->protocol == htons(ETH_P_IP)) {
+			IP_ECN_set_ce(ip_hdr(skb));
+		} else if (skb->protocol == htons(ETH_P_IPV6)) {
+			IP6_ECN_set_ce(ipv6_hdr(skb));
+		}
+	}
+}
+
+static inline u8
+ipgre_ecn_encapsulate(u8 tos, struct iphdr *old_iph, struct sk_buff *skb)
+{
+	u8 inner = 0;
+	if (skb->protocol == htons(ETH_P_IP))
+		inner = old_iph->tos;
+	else if (skb->protocol == htons(ETH_P_IPV6))
+		inner = ipv6_get_dsfield((struct ipv6hdr *)old_iph);
+	return INET_ECN_encapsulate(tos, inner);
+}
+
+static int ipgre_rcv(struct sk_buff *skb)
+{
+	struct iphdr *iph;
+	u8     *h;
+	__be16    flags;
+	__sum16   csum = 0;
+	__be32 key = 0;
+	u32    seqno = 0;
+	struct ip_tunnel *tunnel;
+	int    offset = 4;
+	__be16 gre_proto;
+	unsigned int len;
+
+	if (!pskb_may_pull(skb, 16))
+		goto drop_nolock;
+
+	iph = ip_hdr(skb);
+	h = skb->data;
+	flags = *(__be16*)h;
+
+	if (flags&(GRE_CSUM|GRE_KEY|GRE_ROUTING|GRE_SEQ|GRE_VERSION)) {
+		/* - Version must be 0.
+		   - We do not support routing headers.
+		 */
+		if (flags&(GRE_VERSION|GRE_ROUTING))
+			goto drop_nolock;
+
+		if (flags&GRE_CSUM) {
+			switch (skb->ip_summed) {
+			case CHECKSUM_COMPLETE:
+				csum = csum_fold(skb->csum);
+				if (!csum)
+					break;
+				/* fall through */
+			case CHECKSUM_NONE:
+				skb->csum = 0;
+				csum = __skb_checksum_complete(skb);
+				skb->ip_summed = CHECKSUM_COMPLETE;
+			}
+			offset += 4;
+		}
+		if (flags&GRE_KEY) {
+			key = *(__be32*)(h + offset);
+			offset += 4;
+		}
+		if (flags&GRE_SEQ) {
+			seqno = ntohl(*(__be32*)(h + offset));
+			offset += 4;
+		}
+	}
+
+	gre_proto = *(__be16 *)(h + 2);
+
+	read_lock(&ipgre_lock);
+	if ((tunnel = ipgre_tunnel_lookup(skb->dev,
+					  iph->saddr, iph->daddr, key,
+					  gre_proto))) {
+		struct net_device_stats *stats;
+#ifdef HAVE_NETDEV_STATS
+		stats = &tunnel->dev->stats;
+#else
+		stats = &tunnel->stat;
+#endif
+
+		secpath_reset(skb);
+
+		skb->protocol = gre_proto;
+		/* WCCP version 1 and 2 protocol decoding.
+		 * - Change protocol to IP
+		 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
+		 */
+		if (flags == 0 && gre_proto == htons(ETH_P_WCCP)) {
+			skb->protocol = htons(ETH_P_IP);
+			if ((*(h + offset) & 0xF0) != 0x40)
+				offset += 4;
+		}
+
+		skb->mac_header = skb->network_header;
+		__pskb_pull(skb, offset);
+		skb_postpull_rcsum(skb, skb_transport_header(skb), offset);
+		skb->pkt_type = PACKET_HOST;
+#ifdef CONFIG_NET_IPGRE_BROADCAST
+		if (ipv4_is_multicast(iph->daddr)) {
+			/* Looped back packet, drop it! */
+			if (skb_rtable(skb)->fl.iif == 0)
+				goto drop;
+			stats->multicast++;
+			skb->pkt_type = PACKET_BROADCAST;
+		}
+#endif
+
+		if (((flags&GRE_CSUM) && csum) ||
+		    (!(flags&GRE_CSUM) && tunnel->parms.i_flags&GRE_CSUM)) {
+			stats->rx_crc_errors++;
+			stats->rx_errors++;
+			goto drop;
+		}
+		if (tunnel->parms.i_flags&GRE_SEQ) {
+			if (!(flags&GRE_SEQ) ||
+			    (tunnel->i_seqno && (s32)(seqno - tunnel->i_seqno) < 0)) {
+				stats->rx_fifo_errors++;
+				stats->rx_errors++;
+				goto drop;
+			}
+			tunnel->i_seqno = seqno + 1;
+		}
+
+		len = skb->len;
+
+		/* Warning: All skb pointers will be invalidated! */
+		if (tunnel->dev->type == ARPHRD_ETHER) {
+			if (!pskb_may_pull(skb, ETH_HLEN)) {
+				stats->rx_length_errors++;
+				stats->rx_errors++;
+				goto drop;
+			}
+
+			iph = ip_hdr(skb);
+			skb->protocol = eth_type_trans(skb, tunnel->dev);
+			skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
+		}
+
+		stats->rx_packets++;
+		stats->rx_bytes += len;
+		skb->dev = tunnel->dev;
+		skb_dst_drop(skb);
+		nf_reset(skb);
+
+		skb_reset_network_header(skb);
+		ipgre_ecn_decapsulate(iph, skb);
+
+#ifdef CHECKSUM_HW
+		/* XXX: Temporary workaround to avoid a panic when doing
+		 * bridging due to multiple meanings of CHECKSUM_HW. */
+		if (skb->ip_summed == CHECKSUM_HW)
+			skb->ip_summed = CHECKSUM_NONE;
+#endif
+
+		netif_rx(skb);
+		read_unlock(&ipgre_lock);
+		return(0);
+	}
+	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
+
+drop:
+	read_unlock(&ipgre_lock);
+drop_nolock:
+	kfree_skb(skb);
+	return(0);
+}
+
+static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ip_tunnel *tunnel = netdev_priv(dev);
+	struct net_device_stats *stats;
+	struct iphdr  *old_iph = ip_hdr(skb);
+	struct iphdr  *tiph;
+	u8     tos;
+	__be16 df;
+	struct rtable *rt;     			/* Route to the other host */
+	struct net_device *tdev;		/* Device to other host */
+	struct iphdr  *iph;			/* Our new IP header */
+	unsigned int max_headroom;		/* The extra header space needed */
+	int    gre_hlen;
+	__be32 dst;
+	int    mtu;
+
+#ifdef HAVE_NETDEV_STATS
+	stats = &tunnel->dev->stats;
+#else
+	stats = &tunnel->stat;
+#endif
+
+	if (dev->type == ARPHRD_ETHER)
+		IPCB(skb)->flags = 0;
+
+#ifdef HAVE_NETDEV_HEADER_OPS
+	if (dev->header_ops && dev->type == ARPHRD_IPGRE) {
+#else
+	if (dev->hard_header && dev->type == ARPHRD_IPGRE) {
+#endif
+		gre_hlen = 0;
+		tiph = (struct iphdr *)skb->data;
+	} else {
+		gre_hlen = tunnel->hlen;
+		tiph = &tunnel->parms.iph;
+	}
+
+	if ((dst = tiph->daddr) == 0) {
+		/* NBMA tunnel */
+
+		if (skb_dst(skb) == NULL) {
+			stats->tx_fifo_errors++;
+			goto tx_error;
+		}
+
+		if (skb->protocol == htons(ETH_P_IP)) {
+			rt = skb_rtable(skb);
+			if ((dst = rt->rt_gateway) == 0)
+				goto tx_error_icmp;
+		}
+#ifdef CONFIG_IPV6
+		else if (skb->protocol == htons(ETH_P_IPV6)) {
+			struct in6_addr *addr6;
+			int addr_type;
+			struct neighbour *neigh = skb_dst(skb)->neighbour;
+
+			if (neigh == NULL)
+				goto tx_error;
+
+			addr6 = (struct in6_addr *)&neigh->primary_key;
+			addr_type = ipv6_addr_type(addr6);
+
+			if (addr_type == IPV6_ADDR_ANY) {
+				addr6 = &ipv6_hdr(skb)->daddr;
+				addr_type = ipv6_addr_type(addr6);
+			}
+
+			if ((addr_type & IPV6_ADDR_COMPATv4) == 0)
+				goto tx_error_icmp;
+
+			dst = addr6->s6_addr32[3];
+		}
+#endif
+		else
+			goto tx_error;
+	}
+
+	tos = tiph->tos;
+	if (tos == 1) {
+		tos = 0;
+		if (skb->protocol == htons(ETH_P_IP))
+			tos = old_iph->tos;
+	}
+
+	{
+		struct flowi fl = { .oif = tunnel->parms.link,
+				    .nl_u = { .ip4_u =
+					      { .daddr = dst,
+						.saddr = tiph->saddr,
+						.tos = RT_TOS(tos) } },
+				    .proto = IPPROTO_GRE };
+		if (ip_route_output_key(dev_net(dev), &rt, &fl)) {
+			stats->tx_carrier_errors++;
+			goto tx_error;
+		}
+	}
+	tdev = rt->u.dst.dev;
+
+	if (tdev == dev) {
+		ip_rt_put(rt);
+		stats->collisions++;
+		goto tx_error;
+	}
+
+	df = tiph->frag_off;
+	if (df)
+#ifdef HAVE_NETDEV_NEEDED_HEADROOM
+		mtu = dst_mtu(&rt->u.dst) - dev->hard_header_len - tunnel->hlen;
+#else
+		mtu = dst_mtu(&rt->u.dst) - tunnel->hlen;
+#endif
+	else
+		mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;
+
+	if (skb_dst(skb))
+		skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu);
+
+	if (skb->protocol == htons(ETH_P_IP)) {
+		df |= (old_iph->frag_off&htons(IP_DF));
+
+		if ((old_iph->frag_off&htons(IP_DF)) &&
+		    mtu < ntohs(old_iph->tot_len)) {
+			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
+			ip_rt_put(rt);
+			goto tx_error;
+		}
+	}
+#ifdef CONFIG_IPV6
+	else if (skb->protocol == htons(ETH_P_IPV6)) {
+		struct rt6_info *rt6 = (struct rt6_info *)skb_dst(skb);
+
+		if (rt6 && mtu < dst_mtu(skb_dst(skb)) && mtu >= IPV6_MIN_MTU) {
+			if ((tunnel->parms.iph.daddr &&
+			     !ipv4_is_multicast(tunnel->parms.iph.daddr)) ||
+			    rt6->rt6i_dst.plen == 128) {
+				rt6->rt6i_flags |= RTF_MODIFIED;
+				skb_dst(skb)->metrics[RTAX_MTU-1] = mtu;
+			}
+		}
+
+		if (mtu >= IPV6_MIN_MTU && mtu < skb->len - tunnel->hlen + gre_hlen) {
+			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev);
+			ip_rt_put(rt);
+			goto tx_error;
+		}
+	}
+#endif
+
+	if (tunnel->err_count > 0) {
+		if (time_before(jiffies,
+				tunnel->err_time + IPTUNNEL_ERR_TIMEO)) {
+			tunnel->err_count--;
+
+			dst_link_failure(skb);
+		} else
+			tunnel->err_count = 0;
+	}
+
+	max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen;
+
+	if (skb_headroom(skb) < max_headroom || skb_shared(skb)||
+	    (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {
+		struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
+		if (!new_skb) {
+			ip_rt_put(rt);
+			stats->tx_dropped++;
+			dev_kfree_skb(skb);
+			return NETDEV_TX_OK;
+		}
+		if (skb->sk)
+			skb_set_owner_w(new_skb, skb->sk);
+		dev_kfree_skb(skb);
+		skb = new_skb;
+		old_iph = ip_hdr(skb);
+	}
+
+	skb_reset_transport_header(skb);
+	skb_push(skb, gre_hlen);
+	skb_reset_network_header(skb);
+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
+	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
+			      IPSKB_REROUTED);
+	skb_dst_drop(skb);
+	skb_dst_set(skb, &rt->u.dst);
+
+	/*
+	 *	Push down and install the IPIP header.
+	 */
+
+	iph 			=	ip_hdr(skb);
+	iph->version		=	4;
+	iph->ihl		=	sizeof(struct iphdr) >> 2;
+	iph->frag_off		=	df;
+	iph->protocol		=	IPPROTO_GRE;
+	iph->tos		=	ipgre_ecn_encapsulate(tos, old_iph, skb);
+	iph->daddr		=	rt->rt_dst;
+	iph->saddr		=	rt->rt_src;
+
+	if ((iph->ttl = tiph->ttl) == 0) {
+		if (skb->protocol == htons(ETH_P_IP))
+			iph->ttl = old_iph->ttl;
+#ifdef CONFIG_IPV6
+		else if (skb->protocol == htons(ETH_P_IPV6))
+			iph->ttl = ((struct ipv6hdr *)old_iph)->hop_limit;
+#endif
+		else
+			iph->ttl = dst_metric(&rt->u.dst, RTAX_HOPLIMIT);
+	}
+
+	((__be16 *)(iph + 1))[0] = tunnel->parms.o_flags;
+	((__be16 *)(iph + 1))[1] = (dev->type == ARPHRD_ETHER) ?
+				   htons(ETH_P_TEB) : skb->protocol;
+
+	if (tunnel->parms.o_flags&(GRE_KEY|GRE_CSUM|GRE_SEQ)) {
+		__be32 *ptr = (__be32*)(((u8*)iph) + tunnel->hlen - 4);
+
+		if (tunnel->parms.o_flags&GRE_SEQ) {
+			++tunnel->o_seqno;
+			*ptr = htonl(tunnel->o_seqno);
+			ptr--;
+		}
+		if (tunnel->parms.o_flags&GRE_KEY) {
+			*ptr = tunnel->parms.o_key;
+			ptr--;
+		}
+		if (tunnel->parms.o_flags&GRE_CSUM) {
+			*ptr = 0;
+			*(__sum16*)ptr = ip_compute_csum((void*)(iph+1), skb->len - sizeof(struct iphdr));
+		}
+	}
+
+	nf_reset(skb);
+
+	IPTUNNEL_XMIT();
+	return NETDEV_TX_OK;
+
+tx_error_icmp:
+	dst_link_failure(skb);
+
+tx_error:
+	stats->tx_errors++;
+	dev_kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+static int ipgre_tunnel_bind_dev(struct net_device *dev)
+{
+	struct net_device *tdev = NULL;
+	struct ip_tunnel *tunnel;
+	struct iphdr *iph;
+	int hlen = LL_MAX_HEADER;
+	int mtu = ETH_DATA_LEN;
+	int addend = sizeof(struct iphdr) + 4;
+
+	tunnel = netdev_priv(dev);
+	iph = &tunnel->parms.iph;
+
+	/* Guess output device to choose reasonable mtu and needed_headroom */
+
+	if (iph->daddr) {
+		struct flowi fl = { .oif = tunnel->parms.link,
+				    .nl_u = { .ip4_u =
+					      { .daddr = iph->daddr,
+						.saddr = iph->saddr,
+						.tos = RT_TOS(iph->tos) } },
+				    .proto = IPPROTO_GRE };
+		struct rtable *rt;
+		if (!ip_route_output_key(dev_net(dev), &rt, &fl)) {
+			tdev = rt->u.dst.dev;
+			ip_rt_put(rt);
+		}
+
+		if (dev->type != ARPHRD_ETHER)
+			dev->flags |= IFF_POINTOPOINT;
+	}
+
+	if (!tdev && tunnel->parms.link)
+		tdev = __dev_get_by_index(dev_net(dev), tunnel->parms.link);
+
+	if (tdev) {
+#ifdef HAVE_NETDEV_NEEDED_HEADROOM
+		hlen = tdev->hard_header_len + tdev->needed_headroom;
+#else
+		hlen = tdev->hard_header_len;
+#endif
+		mtu = tdev->mtu;
+	}
+	dev->iflink = tunnel->parms.link;
+
+	/* Precalculate GRE options length */
+	if (tunnel->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) {
+		if (tunnel->parms.o_flags&GRE_CSUM)
+			addend += 4;
+		if (tunnel->parms.o_flags&GRE_KEY)
+			addend += 4;
+		if (tunnel->parms.o_flags&GRE_SEQ)
+			addend += 4;
+	}
+#ifdef HAVE_NETDEV_NEEDED_HEADROOM
+	dev->needed_headroom = hlen + addend;
+	mtu -= dev->hard_header_len + addend;
+#else
+	dev->hard_header_len = hlen + addend;
+	mtu -= addend;
+#endif
+	tunnel->hlen = addend;
+
+	if (mtu < 68)
+		mtu = 68;
+
+	return mtu;
+}
+
+static int
+ipgre_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
+{
+	int err = 0;
+	struct ip_tunnel_parm p;
+	struct ip_tunnel *t;
+	struct net *net = dev_net(dev);
+	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
+	int add_tunnel, gretap;
+
+	switch (cmd) {
+	case SIOCGETTUNNEL:
+		t = NULL;
+		if (dev == ign->fb_tunnel_dev) {
+			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
+				err = -EFAULT;
+				break;
+			}
+			t = ipgre_tunnel_locate(net, &p, false, 0);
+		}
+		if (t == NULL)
+			t = netdev_priv(dev);
+		memcpy(&p, &t->parms, sizeof(p));
+		if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
+			err = -EFAULT;
+		break;
+
+	case SIOCADDTUNNEL:
+	case SIOCCHGTUNNEL:
+	case SIOCADDGRETAP:
+	case SIOCCHGGRETAP:
+		err = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			goto done;
+
+		err = -EFAULT;
+		if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
+			goto done;
+
+		err = -EINVAL;
+		if (p.iph.version != 4 || p.iph.protocol != IPPROTO_GRE ||
+		    p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)) ||
+		    ((p.i_flags|p.o_flags)&(GRE_VERSION|GRE_ROUTING)))
+			goto done;
+
+		add_tunnel = (cmd == SIOCADDTUNNEL || cmd == SIOCADDGRETAP);
+		gretap = (cmd == SIOCADDGRETAP || cmd == SIOCCHGGRETAP);
+
+		if (p.iph.ttl)
+			p.iph.frag_off |= htons(IP_DF);
+
+		if (!(p.i_flags&GRE_KEY))
+			p.i_key = 0;
+		if (!(p.o_flags&GRE_KEY))
+			p.o_key = 0;
+
+		t = ipgre_tunnel_locate(net, &p, gretap, add_tunnel);
+
+		if (dev != ign->fb_tunnel_dev && !add_tunnel) {
+			if (t != NULL) {
+				if (t->dev != dev) {
+					err = -EEXIST;
+					break;
+				}
+			} else {
+				unsigned nflags = 0;
+
+				t = netdev_priv(dev);
+
+				if (ipv4_is_multicast(p.iph.daddr))
+					nflags = IFF_BROADCAST;
+				else if (p.iph.daddr)
+					nflags = IFF_POINTOPOINT;
+
+				if ((dev->flags^nflags)&(IFF_POINTOPOINT|IFF_BROADCAST)) {
+					err = -EINVAL;
+					break;
+				}
+				ipgre_tunnel_unlink(ign, t);
+				t->parms.iph.saddr = p.iph.saddr;
+				t->parms.iph.daddr = p.iph.daddr;
+				t->parms.i_key = p.i_key;
+				t->parms.o_key = p.o_key;
+				memcpy(dev->dev_addr, &p.iph.saddr, 4);
+				memcpy(dev->broadcast, &p.iph.daddr, 4);
+				ipgre_tunnel_link(ign, t);
+				netdev_state_change(dev);
+			}
+		}
+
+		if (t) {
+			err = 0;
+			if (!add_tunnel) {
+				t->parms.iph.ttl = p.iph.ttl;
+				t->parms.iph.tos = p.iph.tos;
+				t->parms.iph.frag_off = p.iph.frag_off;
+				if (t->parms.link != p.link) {
+					t->parms.link = p.link;
+					dev->mtu = ipgre_tunnel_bind_dev(dev);
+					netdev_state_change(dev);
+				}
+			}
+			if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof(p)))
+				err = -EFAULT;
+		} else
+			err = (add_tunnel ? -ENOBUFS : -ENOENT);
+		break;
+
+	case SIOCDELTUNNEL:
+		err = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			goto done;
+
+		if (dev == ign->fb_tunnel_dev) {
+			err = -EFAULT;
+			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
+				goto done;
+			err = -ENOENT;
+			if ((t = ipgre_tunnel_locate(net, &p, false, 0)) == NULL)
+				goto done;
+			err = -EPERM;
+			if (t == netdev_priv(ign->fb_tunnel_dev))
+				goto done;
+			dev = t->dev;
+		}
+		unregister_netdevice(dev);
+		err = 0;
+		break;
+
+	default:
+		err = -EINVAL;
+	}
+
+done:
+	return err;
+}
+
+#ifndef HAVE_NETDEV_STATS
+static struct net_device_stats *ipgre_tunnel_get_stats(struct net_device *dev)
+{
+	return &(((struct ip_tunnel*)netdev_priv(dev))->stat);
+}
+#endif
+
+static int ipgre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct ip_tunnel *tunnel = netdev_priv(dev);
+	if (new_mtu < 68 ||
+#ifdef HAVE_NETDEV_NEEDED_HEADROOM
+	new_mtu > 0xFFF8 - dev->hard_header_len - tunnel->hlen)
+#else
+	new_mtu > 0xFFF8 - tunnel->hlen)
+#endif
+		return -EINVAL;
+	dev->mtu = new_mtu;
+	return 0;
+}
+
+/* Nice toy. Unfortunately, useless in real life :-)
+   It allows to construct virtual multiprotocol broadcast "LAN"
+   over the Internet, provided multicast routing is tuned.
+
+
+   I have no idea was this bicycle invented before me,
+   so that I had to set ARPHRD_IPGRE to a random value.
+   I have an impression, that Cisco could make something similar,
+   but this feature is apparently missing in IOS<=11.2(8).
+
+   I set up 10.66.66/24 and fec0:6666:6666::0/96 as virtual networks
+   with broadcast 224.66.66.66. If you have access to mbone, play with me :-)
+
+   ping -t 255 224.66.66.66
+
+   If nobody answers, mbone does not work.
+
+   ip tunnel add Universe mode gre remote 224.66.66.66 local <Your_real_addr> ttl 255
+   ip addr add 10.66.66.<somewhat>/24 dev Universe
+   ifconfig Universe up
+   ifconfig Universe add fe80::<Your_real_addr>/10
+   ifconfig Universe add fec0:6666:6666::<Your_real_addr>/96
+   ftp 10.66.66.66
+   ...
+   ftp fec0:6666:6666::193.233.7.65
+   ...
+
+ */
+
+#ifdef HAVE_NETDEV_HEADER_OPS
+static int ipgre_header(struct sk_buff *skb, struct net_device *dev,
+                       unsigned short type,
+                       const void *daddr, const void *saddr, unsigned len)
+#else
+static int ipgre_header(struct sk_buff *skb, struct net_device *dev, unsigned short type,
+			void *daddr, void *saddr, unsigned len)
+#endif
+{
+	struct ip_tunnel *t = netdev_priv(dev);
+	struct iphdr *iph = (struct iphdr *)skb_push(skb, t->hlen);
+	__be16 *p = (__be16*)(iph+1);
+
+	memcpy(iph, &t->parms.iph, sizeof(struct iphdr));
+	p[0]		= t->parms.o_flags;
+	p[1]		= htons(type);
+
+	/*
+	 *	Set the source hardware address.
+	 */
+
+	if (saddr)
+		memcpy(&iph->saddr, saddr, 4);
+
+	if (daddr) {
+		memcpy(&iph->daddr, daddr, 4);
+		return t->hlen;
+	}
+	if (iph->daddr && !ipv4_is_multicast(iph->daddr))
+		return t->hlen;
+
+	return -t->hlen;
+}
+
+#ifdef HAVE_NETDEV_HEADER_OPS
+static int ipgre_header_parse(const struct sk_buff *skb, unsigned char *haddr)
+#else
+static int ipgre_header_parse(struct sk_buff *skb, unsigned char *haddr)
+#endif
+{
+	struct iphdr *iph = (struct iphdr *) skb_mac_header(skb);
+	memcpy(haddr, &iph->saddr, 4);
+	return 4;
+}
+
+#ifdef HAVE_NETDEV_HEADER_OPS
+static const struct header_ops ipgre_header_ops = {
+	.create = ipgre_header,
+	.parse  = ipgre_header_parse,
+};
+#endif
+
+#ifdef CONFIG_NET_IPGRE_BROADCAST
+static int ipgre_open(struct net_device *dev)
+{
+	struct ip_tunnel *t = netdev_priv(dev);
+
+	if (ipv4_is_multicast(t->parms.iph.daddr)) {
+		struct flowi fl = { .oif = t->parms.link,
+				    .nl_u = { .ip4_u =
+					      { .daddr = t->parms.iph.daddr,
+						.saddr = t->parms.iph.saddr,
+						.tos = RT_TOS(t->parms.iph.tos) } },
+				    .proto = IPPROTO_GRE };
+		struct rtable *rt;
+		if (ip_route_output_key(dev_net(dev), &rt, &fl))
+			return -EADDRNOTAVAIL;
+		dev = rt->u.dst.dev;
+		ip_rt_put(rt);
+		if (__in_dev_get_rtnl(dev) == NULL)
+			return -EADDRNOTAVAIL;
+		t->mlink = dev->ifindex;
+		ip_mc_inc_group(__in_dev_get_rtnl(dev), t->parms.iph.daddr);
+	}
+	return 0;
+}
+
+static int ipgre_close(struct net_device *dev)
+{
+	struct ip_tunnel *t = netdev_priv(dev);
+
+	if (ipv4_is_multicast(t->parms.iph.daddr) && t->mlink) {
+		struct in_device *in_dev;
+		in_dev = inetdev_by_index(dev_net(dev), t->mlink);
+		if (in_dev) {
+			ip_mc_dec_group(in_dev, t->parms.iph.daddr);
+			in_dev_put(in_dev);
+		}
+	}
+	return 0;
+}
+
+#endif
+
+#ifdef HAVE_NET_DEVICE_OPS
+static const struct net_device_ops ipgre_netdev_ops = {
+	.ndo_init		= ipgre_tunnel_init,
+	.ndo_uninit		= ipgre_tunnel_uninit,
+#ifdef CONFIG_NET_IPGRE_BROADCAST
+	.ndo_open		= ipgre_open,
+	.ndo_stop		= ipgre_close,
+#endif
+	.ndo_start_xmit		= ipgre_tunnel_xmit,
+	.ndo_do_ioctl		= ipgre_tunnel_ioctl,
+	.ndo_change_mtu		= ipgre_tunnel_change_mtu,
+};
+#endif
+
+static void ipgre_tunnel_setup(struct net_device *dev)
+{
+#ifdef HAVE_NET_DEVICE_OPS
+	dev->netdev_ops         = &ipgre_netdev_ops;
+#else
+	dev->init               = ipgre_tunnel_init;
+	dev->uninit		= ipgre_tunnel_uninit;
+	dev->hard_start_xmit	= ipgre_tunnel_xmit;
+#ifndef HAVE_NETDEV_STATS
+	dev->get_stats          = ipgre_tunnel_get_stats;
+#endif
+	dev->do_ioctl		= ipgre_tunnel_ioctl;
+	dev->change_mtu		= ipgre_tunnel_change_mtu;
+#endif /* HAVE_NET_DEVICE_OPS */
+	dev->destructor 	= free_netdev;
+
+	dev->type		= ARPHRD_IPGRE;
+#ifdef HAVE_NETDEV_NEEDED_HEADROOM
+	dev->needed_headroom    = LL_MAX_HEADER + sizeof(struct iphdr) + 4;
+#else
+	dev->hard_header_len 	= LL_MAX_HEADER + sizeof(struct iphdr) + 4;
+#endif
+	dev->mtu		= ETH_DATA_LEN - sizeof(struct iphdr) - 4;
+	dev->flags		= IFF_NOARP;
+	dev->iflink		= 0;
+	dev->addr_len		= 4;
+	dev->features		|= NETIF_F_NETNS_LOCAL;
+	dev->priv_flags         &= ~IFF_XMIT_DST_RELEASE;
+}
+
+static int ipgre_tunnel_init(struct net_device *dev)
+{
+	struct ip_tunnel *tunnel;
+	struct iphdr *iph;
+
+	tunnel = netdev_priv(dev);
+	iph = &tunnel->parms.iph;
+
+	tunnel->dev = dev;
+	strcpy(tunnel->parms.name, dev->name);
+
+	memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
+	memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);
+
+	if (iph->daddr) {
+#ifdef CONFIG_NET_IPGRE_BROADCAST
+		if (ipv4_is_multicast(iph->daddr)) {
+			if (!iph->saddr)
+				return -EINVAL;
+			dev->flags = IFF_BROADCAST;
+#ifdef HAVE_NETDEV_HEADER_OPS
+			dev->header_ops = &ipgre_header_ops;
+#else
+			dev->hard_header = ipgre_header;
+			dev->hard_header_parse = ipgre_header_parse;
+#endif
+#ifndef HAVE_NET_DEVICE_OPS
+			dev->open = ipgre_open;
+			dev->stop = ipgre_close;
+#endif
+		}
+#endif
+	} else {
+#ifdef HAVE_NETDEV_HEADER_OPS
+		dev->header_ops = &ipgre_header_ops;
+#else
+		dev->hard_header = ipgre_header;
+		dev->hard_header_parse = ipgre_header_parse;
+#endif
+	}
+
+	return 0;
+}
+
+#ifdef HAVE_NET_DEVICE_OPS
+static void ipgre_fb_tunnel_init(struct net_device *dev)
+#else
+static int ipgre_fb_tunnel_init(struct net_device *dev)
+#endif
+{
+	struct ip_tunnel *tunnel = netdev_priv(dev);
+	struct iphdr *iph = &tunnel->parms.iph;
+	struct ipgre_net *ign = net_generic(dev_net(dev), ipgre_net_id);
+
+	tunnel->dev = dev;
+	strcpy(tunnel->parms.name, dev->name);
+
+	iph->version		= 4;
+	iph->protocol		= IPPROTO_GRE;
+	iph->ihl		= 5;
+	tunnel->hlen		= sizeof(struct iphdr) + 4;
+
+	dev_hold(dev);
+	ign->tunnels_wc[0]	= tunnel;
+
+#ifndef HAVE_NET_DEVICE_OPS
+	return 0;
+#endif
+}
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,32)
+static struct net_protocol ipgre_protocol = {
+#else
+static const struct net_protocol ipgre_protocol = {
+#endif
+	.handler	=	ipgre_rcv,
+	.err_handler	=	ipgre_err,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,26)
+	.netns_ok	=	1,
+#endif
+};
+
+static void ipgre_destroy_tunnels(struct ipgre_net *ign)
+{
+	int prio;
+
+	for (prio = 0; prio < 4; prio++) {
+		int h;
+		for (h = 0; h < HASH_SIZE; h++) {
+			struct ip_tunnel *t;
+			while ((t = ign->tunnels[prio][h]) != NULL)
+				unregister_netdevice(t->dev);
+		}
+	}
+}
+
+static int ipgre_init_net(struct net *net)
+{
+	int err;
+	struct ipgre_net *ign;
+
+	err = -ENOMEM;
+	ign = kzalloc(sizeof(struct ipgre_net), GFP_KERNEL);
+	if (ign == NULL)
+		goto err_alloc;
+
+	err = net_assign_generic(net, ipgre_net_id, ign);
+	if (err < 0)
+		goto err_assign;
+
+	ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), GRE_IOCTL_DEVICE,
+					   ipgre_tunnel_setup);
+	if (!ign->fb_tunnel_dev) {
+		err = -ENOMEM;
+		goto err_alloc_dev;
+	}
+	dev_net_set(ign->fb_tunnel_dev, net);
+
+#ifdef HAVE_NET_DEVICE_OPS
+	ipgre_fb_tunnel_init(ign->fb_tunnel_dev);
+#else
+	ign->fb_tunnel_dev->init = ipgre_fb_tunnel_init;
+#endif
+#ifndef GRE_IOCTL_ONLY
+	ign->fb_tunnel_dev->rtnl_link_ops = &ipgre_link_ops;
+#endif
+
+	if ((err = register_netdev(ign->fb_tunnel_dev)))
+		goto err_reg_dev;
+
+	return 0;
+
+err_reg_dev:
+	free_netdev(ign->fb_tunnel_dev);
+err_alloc_dev:
+	/* nothing */
+err_assign:
+	kfree(ign);
+err_alloc:
+	return err;
+}
+
+static void ipgre_exit_net(struct net *net)
+{
+	struct ipgre_net *ign;
+
+	ign = net_generic(net, ipgre_net_id);
+	rtnl_lock();
+	ipgre_destroy_tunnels(ign);
+	rtnl_unlock();
+	kfree(ign);
+}
+
+static struct pernet_operations ipgre_net_ops = {
+	.init = ipgre_init_net,
+	.exit = ipgre_exit_net,
+};
+
+static int ipgre_tap_init(struct net_device *dev)
+{
+	struct ip_tunnel *tunnel;
+
+	tunnel = netdev_priv(dev);
+
+	tunnel->dev = dev;
+	strcpy(tunnel->parms.name, dev->name);
+
+	ipgre_tunnel_bind_dev(dev);
+
+	return 0;
+}
+
+#ifdef HAVE_NET_DEVICE_OPS
+static const struct net_device_ops ipgre_tap_netdev_ops = {
+	.ndo_init		= ipgre_tap_init,
+	.ndo_uninit		= ipgre_tunnel_uninit,
+	.ndo_start_xmit		= ipgre_tunnel_xmit,
+	.ndo_set_mac_address 	= eth_mac_addr,
+	.ndo_validate_addr	= eth_validate_addr,
+	.ndo_do_ioctl		= ipgre_tunnel_ioctl,
+	.ndo_change_mtu		= ipgre_tunnel_change_mtu,
+};
+#endif
+
+static void ipgre_tap_setup(struct net_device *dev)
+{
+	ether_setup(dev);
+
+#ifdef HAVE_NET_DEVICE_OPS
+	dev->netdev_ops         = &ipgre_tap_netdev_ops;
+#else
+	dev->init		= ipgre_tap_init;
+	dev->uninit		= ipgre_tunnel_uninit;
+	dev->hard_start_xmit	= ipgre_tunnel_xmit;
+#ifndef HAVE_NETDEV_STATS
+	dev->get_stats          = ipgre_tunnel_get_stats;
+#endif
+	dev->do_ioctl		= ipgre_tunnel_ioctl;
+	dev->change_mtu		= ipgre_tunnel_change_mtu;
+#endif /* HAVE_NET_DEVICE_OPS */
+	dev->destructor 	= free_netdev;
+
+	dev->iflink		= 0;
+	dev->features		|= NETIF_F_NETNS_LOCAL;
+}
+
+#ifndef GRE_IOCTL_ONLY
+static int ipgre_tunnel_validate(struct nlattr *tb[], struct nlattr *data[])
+{
+	__be16 flags;
+
+	if (!data)
+		return 0;
+
+	flags = 0;
+	if (data[IFLA_GRE_IFLAGS])
+		flags |= nla_get_be16(data[IFLA_GRE_IFLAGS]);
+	if (data[IFLA_GRE_OFLAGS])
+		flags |= nla_get_be16(data[IFLA_GRE_OFLAGS]);
+	if (flags & (GRE_VERSION|GRE_ROUTING))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int ipgre_tap_validate(struct nlattr *tb[], struct nlattr *data[])
+{
+	__be32 daddr;
+
+	if (tb[IFLA_ADDRESS]) {
+		if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
+			return -EINVAL;
+		if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
+			return -EADDRNOTAVAIL;
+	}
+
+	if (!data)
+		goto out;
+
+	if (data[IFLA_GRE_REMOTE]) {
+		memcpy(&daddr, nla_data(data[IFLA_GRE_REMOTE]), 4);
+		if (!daddr)
+			return -EINVAL;
+	}
+
+out:
+	return ipgre_tunnel_validate(tb, data);
+}
+
+static void ipgre_netlink_parms(struct nlattr *data[],
+				struct ip_tunnel_parm *parms)
+{
+	memset(parms, 0, sizeof(*parms));
+
+	parms->iph.protocol = IPPROTO_GRE;
+
+	if (!data)
+		return;
+
+	if (data[IFLA_GRE_LINK])
+		parms->link = nla_get_u32(data[IFLA_GRE_LINK]);
+
+	if (data[IFLA_GRE_IFLAGS])
+		parms->i_flags = nla_get_be16(data[IFLA_GRE_IFLAGS]);
+
+	if (data[IFLA_GRE_OFLAGS])
+		parms->o_flags = nla_get_be16(data[IFLA_GRE_OFLAGS]);
+
+	if (data[IFLA_GRE_IKEY])
+		parms->i_key = nla_get_be32(data[IFLA_GRE_IKEY]);
+
+	if (data[IFLA_GRE_OKEY])
+		parms->o_key = nla_get_be32(data[IFLA_GRE_OKEY]);
+
+	if (data[IFLA_GRE_LOCAL])
+		parms->iph.saddr = nla_get_be32(data[IFLA_GRE_LOCAL]);
+
+	if (data[IFLA_GRE_REMOTE])
+		parms->iph.daddr = nla_get_be32(data[IFLA_GRE_REMOTE]);
+
+	if (data[IFLA_GRE_TTL])
+		parms->iph.ttl = nla_get_u8(data[IFLA_GRE_TTL]);
+
+	if (data[IFLA_GRE_TOS])
+		parms->iph.tos = nla_get_u8(data[IFLA_GRE_TOS]);
+
+	if (!data[IFLA_GRE_PMTUDISC] || nla_get_u8(data[IFLA_GRE_PMTUDISC]))
+		parms->iph.frag_off = htons(IP_DF);
+}
+
+static int ipgre_newlink(struct net_device *dev, struct nlattr *tb[],
+			 struct nlattr *data[])
+{
+	struct ip_tunnel *nt;
+	struct net *net = dev_net(dev);
+	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
+	int mtu;
+	int err;
+
+	nt = netdev_priv(dev);
+	ipgre_netlink_parms(data, &nt->parms);
+
+	if (ipgre_tunnel_find(net, &nt->parms, dev->type))
+		return -EEXIST;
+
+	if (dev->type == ARPHRD_ETHER && !tb[IFLA_ADDRESS])
+		random_ether_addr(dev->dev_addr);
+
+	mtu = ipgre_tunnel_bind_dev(dev);
+	if (!tb[IFLA_MTU])
+		dev->mtu = mtu;
+
+	err = register_netdevice(dev);
+	if (err)
+		goto out;
+
+	dev_hold(dev);
+	ipgre_tunnel_link(ign, nt);
+
+out:
+	return err;
+}
+
+static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
+			    struct nlattr *data[])
+{
+	struct ip_tunnel *t, *nt;
+	struct net *net = dev_net(dev);
+	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
+	struct ip_tunnel_parm p;
+	int mtu;
+
+	if (dev == ign->fb_tunnel_dev)
+		return -EINVAL;
+
+	nt = netdev_priv(dev);
+	ipgre_netlink_parms(data, &p);
+
+	t = ipgre_tunnel_locate(net, &p, false, 0);
+
+	if (t) {
+		if (t->dev != dev)
+			return -EEXIST;
+	} else {
+		t = nt;
+
+		if (dev->type != ARPHRD_ETHER) {
+			unsigned nflags = 0;
+
+			if (ipv4_is_multicast(p.iph.daddr))
+				nflags = IFF_BROADCAST;
+			else if (p.iph.daddr)
+				nflags = IFF_POINTOPOINT;
+
+			if ((dev->flags ^ nflags) &
+			    (IFF_POINTOPOINT | IFF_BROADCAST))
+				return -EINVAL;
+		}
+
+		ipgre_tunnel_unlink(ign, t);
+		t->parms.iph.saddr = p.iph.saddr;
+		t->parms.iph.daddr = p.iph.daddr;
+		t->parms.i_key = p.i_key;
+		if (dev->type != ARPHRD_ETHER) {
+			memcpy(dev->dev_addr, &p.iph.saddr, 4);
+			memcpy(dev->broadcast, &p.iph.daddr, 4);
+		}
+		ipgre_tunnel_link(ign, t);
+		netdev_state_change(dev);
+	}
+
+	t->parms.o_key = p.o_key;
+	t->parms.iph.ttl = p.iph.ttl;
+	t->parms.iph.tos = p.iph.tos;
+	t->parms.iph.frag_off = p.iph.frag_off;
+
+	if (t->parms.link != p.link) {
+		t->parms.link = p.link;
+		mtu = ipgre_tunnel_bind_dev(dev);
+		if (!tb[IFLA_MTU])
+			dev->mtu = mtu;
+		netdev_state_change(dev);
+	}
+
+	return 0;
+}
+
+static size_t ipgre_get_size(const struct net_device *dev)
+{
+	return
+		/* IFLA_GRE_LINK */
+		nla_total_size(4) +
+		/* IFLA_GRE_IFLAGS */
+		nla_total_size(2) +
+		/* IFLA_GRE_OFLAGS */
+		nla_total_size(2) +
+		/* IFLA_GRE_IKEY */
+		nla_total_size(4) +
+		/* IFLA_GRE_OKEY */
+		nla_total_size(4) +
+		/* IFLA_GRE_LOCAL */
+		nla_total_size(4) +
+		/* IFLA_GRE_REMOTE */
+		nla_total_size(4) +
+		/* IFLA_GRE_TTL */
+		nla_total_size(1) +
+		/* IFLA_GRE_TOS */
+		nla_total_size(1) +
+		/* IFLA_GRE_PMTUDISC */
+		nla_total_size(1) +
+		0;
+}
+
+static int ipgre_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+	struct ip_tunnel *t = netdev_priv(dev);
+	struct ip_tunnel_parm *p = &t->parms;
+
+	NLA_PUT_U32(skb, IFLA_GRE_LINK, p->link);
+	NLA_PUT_BE16(skb, IFLA_GRE_IFLAGS, p->i_flags);
+	NLA_PUT_BE16(skb, IFLA_GRE_OFLAGS, p->o_flags);
+	NLA_PUT_BE32(skb, IFLA_GRE_IKEY, p->i_key);
+	NLA_PUT_BE32(skb, IFLA_GRE_OKEY, p->o_key);
+	NLA_PUT_BE32(skb, IFLA_GRE_LOCAL, p->iph.saddr);
+	NLA_PUT_BE32(skb, IFLA_GRE_REMOTE, p->iph.daddr);
+	NLA_PUT_U8(skb, IFLA_GRE_TTL, p->iph.ttl);
+	NLA_PUT_U8(skb, IFLA_GRE_TOS, p->iph.tos);
+	NLA_PUT_U8(skb, IFLA_GRE_PMTUDISC, !!(p->iph.frag_off & htons(IP_DF)));
+
+	return 0;
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
+static const struct nla_policy ipgre_policy[IFLA_GRE_MAX + 1] = {
+	[IFLA_GRE_LINK]		= { .type = NLA_U32 },
+	[IFLA_GRE_IFLAGS]	= { .type = NLA_U16 },
+	[IFLA_GRE_OFLAGS]	= { .type = NLA_U16 },
+	[IFLA_GRE_IKEY]		= { .type = NLA_U32 },
+	[IFLA_GRE_OKEY]		= { .type = NLA_U32 },
+	[IFLA_GRE_LOCAL]	= { .len = FIELD_SIZEOF(struct iphdr, saddr) },
+	[IFLA_GRE_REMOTE]	= { .len = FIELD_SIZEOF(struct iphdr, daddr) },
+	[IFLA_GRE_TTL]		= { .type = NLA_U8 },
+	[IFLA_GRE_TOS]		= { .type = NLA_U8 },
+	[IFLA_GRE_PMTUDISC]	= { .type = NLA_U8 },
+};
+
+static struct rtnl_link_ops ipgre_link_ops __read_mostly = {
+	.kind		= "gre",
+	.maxtype	= IFLA_GRE_MAX,
+	.policy		= ipgre_policy,
+	.priv_size	= sizeof(struct ip_tunnel),
+	.setup		= ipgre_tunnel_setup,
+	.validate	= ipgre_tunnel_validate,
+	.newlink	= ipgre_newlink,
+	.changelink	= ipgre_changelink,
+	.get_size	= ipgre_get_size,
+	.fill_info	= ipgre_fill_info,
+};
+
+static struct rtnl_link_ops ipgre_tap_ops __read_mostly = {
+	.kind		= "gretap",
+	.maxtype	= IFLA_GRE_MAX,
+	.policy		= ipgre_policy,
+	.priv_size	= sizeof(struct ip_tunnel),
+	.setup		= ipgre_tap_setup,
+	.validate	= ipgre_tap_validate,
+	.newlink	= ipgre_newlink,
+	.changelink	= ipgre_changelink,
+	.get_size	= ipgre_get_size,
+	.fill_info	= ipgre_fill_info,
+};
+#endif
+
+/*
+ *	And now the modules code and kernel interface.
+ */
+
+static int __init ipgre_init(void)
+{
+	int err;
+
+	printk(KERN_INFO "GRE over IPv4 tunneling driver\n");
+
+	if (inet_add_protocol(&ipgre_protocol, IPPROTO_GRE) < 0) {
+		printk(KERN_INFO "ipgre init: can't add protocol\n");
+		return -EAGAIN;
+	}
+
+	err = register_pernet_gen_device(&ipgre_net_id, &ipgre_net_ops);
+	if (err < 0)
+		goto gen_device_failed;
+
+#ifndef GRE_IOCTL_ONLY
+	err = rtnl_link_register(&ipgre_link_ops);
+	if (err < 0)
+		goto rtnl_link_failed;
+
+	err = rtnl_link_register(&ipgre_tap_ops);
+	if (err < 0)
+		goto tap_ops_failed;
+#endif
+
+out:
+	return err;
+
+#ifndef GRE_IOCTL_ONLY
+tap_ops_failed:
+	rtnl_link_unregister(&ipgre_link_ops);
+rtnl_link_failed:
+	unregister_pernet_gen_device(ipgre_net_id, &ipgre_net_ops);
+#endif
+gen_device_failed:
+	inet_del_protocol(&ipgre_protocol, IPPROTO_GRE);
+	goto out;
+
+}
+
+static void __exit ipgre_fini(void)
+{
+#ifndef GRE_IOCTL_ONLY
+	rtnl_link_unregister(&ipgre_tap_ops);
+	rtnl_link_unregister(&ipgre_link_ops);
+#endif
+	unregister_pernet_gen_device(ipgre_net_id, &ipgre_net_ops);
+	if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0)
+		printk(KERN_INFO "ipgre close: can't remove protocol\n");
+}
+
+module_init(ipgre_init);
+module_exit(ipgre_fini);
+MODULE_DESCRIPTION("GRE over IPv4 tunneling driver");
+MODULE_LICENSE("GPL");
+#ifndef GRE_IOCTL_ONLY
+MODULE_ALIAS_RTNL_LINK("gre");
+MODULE_ALIAS_RTNL_LINK("gretap");
+#endif
+
diff --git a/debian/openvswitch-switch.init b/debian/openvswitch-switch.init
index da4ec692d..dd4bb0596 100755
--- a/debian/openvswitch-switch.init
+++ b/debian/openvswitch-switch.init
@@ -261,6 +261,18 @@ case "$1" in
             exit 1
         fi
 
+        echo -n "Loading ip_gre_mod: "
+        if grep -q '^ip_gre$' /proc/modules; then
+            modprobe -r ip_gre
+        fi
+        if grep -q '^ip_gre_mod$' /proc/modules; then
+            echo "already loaded, nothing to do."
+        elif modprobe ip_gre_mod; then
+            echo "success."
+        else
+            echo "could not find module."
+        fi
+
         for netdev in $NETDEVS; do
             check_op "Removing IP address from $netdev" ifconfig $netdev 0.0.0.0
         done
@@ -386,6 +398,10 @@ case "$1" in
 	echo "$NAME."
 
         check_op "Deleting datapath" ovs-dpctl del-dp of0
+        echo -n "Unloading ip_gre module: "
+        if modprobe -r ip_gre_mod; then
+            echo "success."
+        fi
         check_op "Unloading kernel module" modprobe -r openvswitch_mod
 	;;
     force-stop)
diff --git a/include/openvswitch/automake.mk b/include/openvswitch/automake.mk
index 889a21f56..92e071884 100644
--- a/include/openvswitch/automake.mk
+++ b/include/openvswitch/automake.mk
@@ -1,4 +1,5 @@
 noinst_HEADERS += \
+	include/openvswitch/gre.h \
 	include/openvswitch/brcompat-netlink.h \
 	include/openvswitch/datapath-protocol.h
 
diff --git a/include/openvswitch/gre.h b/include/openvswitch/gre.h
new file mode 100644
index 000000000..2b24cf6ef
--- /dev/null
+++ b/include/openvswitch/gre.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2008, 2009 Nicira Networks.
+ *
+ * This file is offered under your choice of two licenses: Apache 2.0 or GNU
+ * GPL 2.0 or later.  The permission statements for each of these licenses is
+ * given below.  You may license your modifications to this file under either
+ * of these licenses or both.  If you wish to license your modifications under
+ * only one of these licenses, delete the permission text for the other
+ * license.
+ *
+ * ----------------------------------------------------------------------
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ----------------------------------------------------------------------
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * ----------------------------------------------------------------------
+ */
+
+#ifndef OPENVSWITCH_GRE_H
+#define OPENVSWITCH_GRE_H 1
+
+#include <linux/if_tunnel.h>
+#include <linux/version.h>
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,23)
+#define GRE_IOCTL_ONLY
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,28)
+enum
+{
+	IFLA_GRE_UNSPEC,
+	IFLA_GRE_LINK,
+	IFLA_GRE_IFLAGS,
+	IFLA_GRE_OFLAGS,
+	IFLA_GRE_IKEY,
+	IFLA_GRE_OKEY,
+	IFLA_GRE_LOCAL,
+	IFLA_GRE_REMOTE,
+	IFLA_GRE_TTL,
+	IFLA_GRE_TOS,
+	IFLA_GRE_PMTUDISC,
+	__IFLA_GRE_MAX,
+};
+
+#define IFLA_GRE_MAX	(__IFLA_GRE_MAX - 1)
+#endif
+
+#define GRE_IOCTL_DEVICE "gre0"
+
+#define SIOCGETGRETAP	SIOCGETTUNNEL
+#define SIOCADDGRETAP	(SIOCDEVPRIVATE + 10)
+#define SIOCDELGRETAP	SIOCDELTUNNEL
+#define SIOCCHGGRETAP	(SIOCDEVPRIVATE + 11)
+
+#endif /* openvswitch/gre.h */
diff --git a/xenserver/etc_init.d_vswitch b/xenserver/etc_init.d_vswitch
index bd621c106..7299430b8 100755
--- a/xenserver/etc_init.d_vswitch
+++ b/xenserver/etc_init.d_vswitch
@@ -92,6 +92,9 @@ function insert_modules_if_required {
     if [ -n "$BRCOMPATD_PIDFILE" ] && ! lsmod | grep -q "brcompat_mod"; then
         action "Inserting brcompat module" modprobe brcompat_mod
     fi
+    if [ -f "/lib/modules/`uname -r`/kernel/net/vswitch/ip_gre_mod.ko" ] && ! lsmod | grep -q "ip_gre_mod"; then
+        action "Inserting ip_gre module" modprobe ip_gre_mod
+    fi
 }
 
 function remove_modules {
diff --git a/xenserver/vswitch-xen.spec b/xenserver/vswitch-xen.spec
index 1b984b19f..a0899edd1 100644
--- a/xenserver/vswitch-xen.spec
+++ b/xenserver/vswitch-xen.spec
@@ -305,6 +305,9 @@ fi
 /etc/profile.d/vswitch.sh
 /lib/modules/%{xen_version}/kernel/net/vswitch/openvswitch_mod.ko
 /lib/modules/%{xen_version}/kernel/net/vswitch/brcompat_mod.ko
+%if %(echo '%{xen_version}'|awk -F"." '{if ($3>=18) print 1; else print 0;}')
+/lib/modules/%{xen_version}/kernel/net/vswitch/ip_gre_mod.ko
+%endif
 /usr/share/vswitch/scripts/dump-vif-details
 /usr/share/vswitch/scripts/refresh-xs-network-uuids
 /usr/share/vswitch/scripts/interface-reconfigure