ip_gre.c

			ptr--;
		}
		/* Skip GRE checksum if skb is getting offloaded. */
		if (!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE) &&
		    (tunnel->parms.o_flags&GRE_CSUM)) {
			int offset = skb_transport_offset(skb);

			if (skb_has_shared_frag(skb)) {
				err = __skb_linearize(skb);
				if (err)
					goto tx_error;
			}

			*ptr = 0;
			*(__sum16 *)ptr = csum_fold(skb_checksum(skb, offset,
								 skb->len - offset,
								 0));
		}
	}

	nf_reset(skb);

	pkt_len = skb->len - skb_transport_offset(skb);
	err = ip_local_out(skb);
	if (likely(net_xmit_eval(err) == 0)) {
		u64_stats_update_begin(&tstats->syncp);
		tstats->tx_bytes += pkt_len;
		tstats->tx_packets++;
		u64_stats_update_end(&tstats->syncp);
	} else {
		dev->stats.tx_errors++;
		dev->stats.tx_aborted_errors++;
	}
	return NETDEV_TX_OK;

#if IS_ENABLED(CONFIG_IPV6)
tx_error_icmp:
	dst_link_failure(skb);
#endif
tx_error:
	dev->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;
	const 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 flowi4 fl4;
		struct rtable *rt;

		rt = ip_route_output_gre(dev_net(dev), &fl4,
					 iph->daddr, iph->saddr,
					 tunnel->parms.o_key,
					 RT_TOS(iph->tos),
					 tunnel->parms.link);
		if (!IS_ERR(rt)) {
			tdev = rt->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) {
		hlen = tdev->hard_header_len + tdev->needed_headroom;
		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;
	}
	dev->needed_headroom = addend + hlen;
	mtu -= dev->hard_header_len + addend;

	if (mtu < 68)
		mtu = 68;

	tunnel->hlen = addend;
	/* TCP offload with GRE SEQ is not supported. */
	if (!(tunnel->parms.o_flags & GRE_SEQ)) {
		/* device supports enc gso offload*/
		if (tdev->hw_enc_features & NETIF_F_GRE_GSO) {
			dev->features		|= NETIF_F_TSO;
			dev->hw_features	|= NETIF_F_TSO;
		} else {
			dev->features		|= NETIF_F_GSO_SOFTWARE;
			dev->hw_features	|= NETIF_F_GSO_SOFTWARE;
		}
	}

	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);

	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, 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:
		err = -EPERM;
		if (!ns_capable(net->user_ns, 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;
		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, cmd == SIOCADDTUNNEL);

		if (dev != ign->fb_tunnel_dev && cmd == SIOCCHGTUNNEL) {
			if (t != NULL) {
				if (t->dev != dev) {
					err = -EEXIST;
					break;
				}
			} else {
				unsigned int 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);
				synchronize_net();
				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 (cmd == SIOCCHGTUNNEL) {
				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 = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
		break;

	case SIOCDELTUNNEL:
		err = -EPERM;
		if (!ns_capable(net->user_ns, 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, 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;
}

static int ipgre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	if (new_mtu < 68 ||
	    new_mtu > 0xFFF8 - dev->hard_header_len - tunnel->hlen)
		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
   ...

 */

static int ipgre_header(struct sk_buff *skb, struct net_device *dev,
			unsigned short type,
			const void *daddr, const void *saddr, unsigned int len)
{
	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);
	if (iph->daddr)
		return t->hlen;

	return -t->hlen;
}

static int ipgre_header_parse(const struct sk_buff *skb, unsigned char *haddr)
{
	const struct iphdr *iph = (const struct iphdr *) skb_mac_header(skb);
	memcpy(haddr, &iph->saddr, 4);
	return 4;
}

static const struct header_ops ipgre_header_ops = {
	.create	= ipgre_header,
	.parse	= ipgre_header_parse,
};

#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 flowi4 fl4;
		struct rtable *rt;

		rt = ip_route_output_gre(dev_net(dev), &fl4,
					 t->parms.iph.daddr,
					 t->parms.iph.saddr,
					 t->parms.o_key,
					 RT_TOS(t->parms.iph.tos),
					 t->parms.link);
		if (IS_ERR(rt))
			return -EADDRNOTAVAIL;
		dev = rt->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);
	}
	return 0;
}

#endif

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,
	.ndo_get_stats64	= ipgre_get_stats64,
};

static void ipgre_dev_free(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);

	gro_cells_destroy(&tunnel->gro_cells);
	free_percpu(dev->tstats);
	free_netdev(dev);
}

#define GRE_FEATURES (NETIF_F_SG |		\
		      NETIF_F_FRAGLIST |	\
		      NETIF_F_HIGHDMA |		\
		      NETIF_F_HW_CSUM)

static void ipgre_tunnel_setup(struct net_device *dev)
{
	dev->netdev_ops		= &ipgre_netdev_ops;
	dev->destructor 	= ipgre_dev_free;

	dev->type		= ARPHRD_IPGRE;
	dev->needed_headroom 	= LL_MAX_HEADER + sizeof(struct iphdr) + 4;
	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;

	dev->features		|= GRE_FEATURES;
	dev->hw_features	|= GRE_FEATURES;
}

static int ipgre_tunnel_init(struct net_device *dev)
{
	struct ip_tunnel *tunnel;
	struct iphdr *iph;
	int err;

	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;
			dev->header_ops = &ipgre_header_ops;
		}
#endif
	} else
		dev->header_ops = &ipgre_header_ops;

	dev->tstats = alloc_percpu(struct pcpu_tstats);
	if (!dev->tstats)
		return -ENOMEM;

	err = gro_cells_init(&tunnel->gro_cells, dev);
	if (err) {
		free_percpu(dev->tstats);
		return err;
	}

	return 0;
}

static void ipgre_fb_tunnel_init(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct iphdr *iph = &tunnel->parms.iph;

	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);
}


static const struct gre_protocol ipgre_protocol = {
	.handler     = ipgre_rcv,
	.err_handler = ipgre_err,
};

static void ipgre_destroy_tunnels(struct ipgre_net *ign, struct list_head *head)
{
	int prio;

	for (prio = 0; prio < 4; prio++) {
		int h;
		for (h = 0; h < HASH_SIZE; h++) {
			struct ip_tunnel *t;

			t = rtnl_dereference(ign->tunnels[prio][h]);

			while (t != NULL) {
				unregister_netdevice_queue(t->dev, head);
				t = rtnl_dereference(t->next);
			}
		}
	}
}

static int __net_init ipgre_init_net(struct net *net)
{
	struct ipgre_net *ign = net_generic(net, ipgre_net_id);
	int err;

	ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "gre0",
					   ipgre_tunnel_setup);
	if (!ign->fb_tunnel_dev) {
		err = -ENOMEM;
		goto err_alloc_dev;
	}
	dev_net_set(ign->fb_tunnel_dev, net);

	ipgre_fb_tunnel_init(ign->fb_tunnel_dev);
	ign->fb_tunnel_dev->rtnl_link_ops = &ipgre_link_ops;

	if ((err = register_netdev(ign->fb_tunnel_dev)))
		goto err_reg_dev;

	rcu_assign_pointer(ign->tunnels_wc[0],
			   netdev_priv(ign->fb_tunnel_dev));
	return 0;

err_reg_dev:
	ipgre_dev_free(ign->fb_tunnel_dev);
err_alloc_dev:
	return err;
}

static void __net_exit ipgre_exit_net(struct net *net)
{
	struct ipgre_net *ign;
	LIST_HEAD(list);

	ign = net_generic(net, ipgre_net_id);
	rtnl_lock();
	ipgre_destroy_tunnels(ign, &list);
	unregister_netdevice_many(&list);
	rtnl_unlock();
}

static struct pernet_operations ipgre_net_ops = {
	.init = ipgre_init_net,
	.exit = ipgre_exit_net,
	.id   = &ipgre_net_id,
	.size = sizeof(struct ipgre_net),
};

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_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);

	dev->tstats = alloc_percpu(struct pcpu_tstats);
	if (!dev->tstats)
		return -ENOMEM;

	return 0;
}

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_change_mtu		= ipgre_tunnel_change_mtu,
	.ndo_get_stats64	= ipgre_get_stats64,
};

static void ipgre_tap_setup(struct net_device *dev)
{

	ether_setup(dev);

	dev->netdev_ops		= &ipgre_tap_netdev_ops;
	dev->destructor 	= ipgre_dev_free;

	dev->iflink		= 0;
	dev->features		|= NETIF_F_NETNS_LOCAL;

	dev->features		|= GRE_FEATURES;
	dev->hw_features	|= GRE_FEATURES;
}

static int ipgre_newlink(struct net *src_net, 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])
		eth_hw_addr_random(dev);

	mtu = ipgre_tunnel_bind_dev(dev);
	if (!tb[IFLA_MTU])
		dev->mtu = mtu;

	/* Can use a lockless transmit, unless we generate output sequences */
	if (!(nt->parms.o_flags & GRE_SEQ))
		dev->features |= NETIF_F_LLTX;

	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, 0);

	if (t) {
		if (t->dev != dev)
			return -EEXIST;
	} else {
		t = nt;

		if (dev->type != ARPHRD_ETHER) {
			unsigned int 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;

	if (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))))
		goto nla_put_failure;
	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,
};

/*
 *	And now the modules code and kernel interface.
 */

static int __init ipgre_init(void)
{
	int err;

	pr_info("GRE over IPv4 tunneling driver\n");

	err = register_pernet_device(&ipgre_net_ops);
	if (err < 0)
		return err;

	err = gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO);
	if (err < 0) {
		pr_info("%s: can't add protocol\n", __func__);
		goto add_proto_failed;
	}

	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;

out:
	return err;

tap_ops_failed:
	rtnl_link_unregister(&ipgre_link_ops);
rtnl_link_failed:
	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
add_proto_failed:
	unregister_pernet_device(&ipgre_net_ops);
	goto out;
}

static void __exit ipgre_fini(void)
{
	rtnl_link_unregister(&ipgre_tap_ops);
	rtnl_link_unregister(&ipgre_link_ops);
	if (gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0)
		pr_info("%s: can't remove protocol\n", __func__);
	unregister_pernet_device(&ipgre_net_ops);
}

module_init(ipgre_init);
module_exit(ipgre_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK("gre");
MODULE_ALIAS_RTNL_LINK("gretap");
MODULE_ALIAS_NETDEV("gre0");