xref: /linux/net/ipv6/sit.c (revision 1a9239bb4253f9076b5b4b2a1a4e8d7defd77a95)

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	IPv6 over IPv4 tunnel device - Simple Internet Transition (SIT)
 *	Linux INET6 implementation
 *
 *	Authors:
 *	Pedro Roque		<roque@di.fc.ul.pt>
 *	Alexey Kuznetsov	<kuznet@ms2.inr.ac.ru>
 *
 *	Changes:
 * Roger Venning <r.venning@telstra.com>:	6to4 support
 * Nate Thompson <nate@thebog.net>:		6to4 support
 * Fred Templin <fred.l.templin@boeing.com>:	isatap support
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/init.h>
#include <linux/netfilter_ipv4.h>
#include <linux/if_ether.h>

#include <net/sock.h>
#include <net/snmp.h>

#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#include <net/ndisc.h>
#include <net/addrconf.h>
#include <net/ip.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/ip_tunnels.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/dsfield.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/netdev_lock.h>
#include <net/inet_dscp.h>

/*
   This version of net/ipv6/sit.c is cloned of net/ipv4/ip_gre.c

   For comments look at net/ipv4/ip_gre.c --ANK
 */

#define IP6_SIT_HASH_SIZE  16
#define HASH(addr) (((__force u32)addr^((__force u32)addr>>4))&0xF)

static bool log_ecn_error = true;
module_param(log_ecn_error, bool, 0644);
MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN");

static int ipip6_tunnel_init(struct net_device *dev);
static void ipip6_tunnel_setup(struct net_device *dev);
static void ipip6_dev_free(struct net_device *dev);
static bool check_6rd(struct ip_tunnel *tunnel, const struct in6_addr *v6dst,
		      __be32 *v4dst);
static struct rtnl_link_ops sit_link_ops __read_mostly;

static unsigned int sit_net_id __read_mostly;
struct sit_net {
	struct ip_tunnel __rcu *tunnels_r_l[IP6_SIT_HASH_SIZE];
	struct ip_tunnel __rcu *tunnels_r[IP6_SIT_HASH_SIZE];
	struct ip_tunnel __rcu *tunnels_l[IP6_SIT_HASH_SIZE];
	struct ip_tunnel __rcu *tunnels_wc[1];
	struct ip_tunnel __rcu **tunnels[4];

	struct net_device *fb_tunnel_dev;
};

static inline struct sit_net *dev_to_sit_net(struct net_device *dev)
{
	struct ip_tunnel *t = netdev_priv(dev);

	return net_generic(t->net, sit_net_id);
}

/*
 * Must be invoked with rcu_read_lock
 */
static struct ip_tunnel *ipip6_tunnel_lookup(struct net *net,
					     struct net_device *dev,
					     __be32 remote, __be32 local,
					     int sifindex)
{
	unsigned int h0 = HASH(remote);
	unsigned int h1 = HASH(local);
	struct ip_tunnel *t;
	struct sit_net *sitn = net_generic(net, sit_net_id);
	int ifindex = dev ? dev->ifindex : 0;

	for_each_ip_tunnel_rcu(t, sitn->tunnels_r_l[h0 ^ h1]) {
		if (local == t->parms.iph.saddr &&
		    remote == t->parms.iph.daddr &&
		    (!dev || !t->parms.link || ifindex == t->parms.link ||
		     sifindex == t->parms.link) &&
		    (t->dev->flags & IFF_UP))
			return t;
	}
	for_each_ip_tunnel_rcu(t, sitn->tunnels_r[h0]) {
		if (remote == t->parms.iph.daddr &&
		    (!dev || !t->parms.link || ifindex == t->parms.link ||
		     sifindex == t->parms.link) &&
		    (t->dev->flags & IFF_UP))
			return t;
	}
	for_each_ip_tunnel_rcu(t, sitn->tunnels_l[h1]) {
		if (local == t->parms.iph.saddr &&
		    (!dev || !t->parms.link || ifindex == t->parms.link ||
		     sifindex == t->parms.link) &&
		    (t->dev->flags & IFF_UP))
			return t;
	}
	t = rcu_dereference(sitn->tunnels_wc[0]);
	if (t && (t->dev->flags & IFF_UP))
		return t;
	return NULL;
}

static struct ip_tunnel __rcu **
__ipip6_bucket(struct sit_net *sitn, struct ip_tunnel_parm_kern *parms)
{
	__be32 remote = parms->iph.daddr;
	__be32 local = parms->iph.saddr;
	unsigned int h = 0;
	int prio = 0;

	if (remote) {
		prio |= 2;
		h ^= HASH(remote);
	}
	if (local) {
		prio |= 1;
		h ^= HASH(local);
	}
	return &sitn->tunnels[prio][h];
}

static inline struct ip_tunnel __rcu **ipip6_bucket(struct sit_net *sitn,
		struct ip_tunnel *t)
{
	return __ipip6_bucket(sitn, &t->parms);
}

static void ipip6_tunnel_unlink(struct sit_net *sitn, struct ip_tunnel *t)
{
	struct ip_tunnel __rcu **tp;
	struct ip_tunnel *iter;

	for (tp = ipip6_bucket(sitn, t);
	     (iter = rtnl_dereference(*tp)) != NULL;
	     tp = &iter->next) {
		if (t == iter) {
			rcu_assign_pointer(*tp, t->next);
			break;
		}
	}
}

static void ipip6_tunnel_link(struct sit_net *sitn, struct ip_tunnel *t)
{
	struct ip_tunnel __rcu **tp = ipip6_bucket(sitn, t);

	rcu_assign_pointer(t->next, rtnl_dereference(*tp));
	rcu_assign_pointer(*tp, t);
}

static void ipip6_tunnel_clone_6rd(struct net_device *dev, struct sit_net *sitn)
{
#ifdef CONFIG_IPV6_SIT_6RD
	struct ip_tunnel *t = netdev_priv(dev);

	if (dev == sitn->fb_tunnel_dev || !sitn->fb_tunnel_dev) {
		ipv6_addr_set(&t->ip6rd.prefix, htonl(0x20020000), 0, 0, 0);
		t->ip6rd.relay_prefix = 0;
		t->ip6rd.prefixlen = 16;
		t->ip6rd.relay_prefixlen = 0;
	} else {
		struct ip_tunnel *t0 = netdev_priv(sitn->fb_tunnel_dev);
		memcpy(&t->ip6rd, &t0->ip6rd, sizeof(t->ip6rd));
	}
#endif
}

static int ipip6_tunnel_create(struct net_device *dev)
{
	struct ip_tunnel *t = netdev_priv(dev);
	struct sit_net *sitn = net_generic(t->net, sit_net_id);
	int err;

	__dev_addr_set(dev, &t->parms.iph.saddr, 4);
	memcpy(dev->broadcast, &t->parms.iph.daddr, 4);

	if (test_bit(IP_TUNNEL_SIT_ISATAP_BIT, t->parms.i_flags))
		dev->priv_flags |= IFF_ISATAP;

	dev->rtnl_link_ops = &sit_link_ops;

	err = register_netdevice(dev);
	if (err < 0)
		goto out;

	ipip6_tunnel_clone_6rd(dev, sitn);

	ipip6_tunnel_link(sitn, t);
	return 0;

out:
	return err;
}

static struct ip_tunnel *ipip6_tunnel_locate(struct net *net,
					     struct ip_tunnel_parm_kern *parms,
					     int create)
{
	__be32 remote = parms->iph.daddr;
	__be32 local = parms->iph.saddr;
	struct ip_tunnel *t, *nt;
	struct ip_tunnel __rcu **tp;
	struct net_device *dev;
	char name[IFNAMSIZ];
	struct sit_net *sitn = net_generic(net, sit_net_id);

	for (tp = __ipip6_bucket(sitn, parms);
	    (t = rtnl_dereference(*tp)) != NULL;
	     tp = &t->next) {
		if (local == t->parms.iph.saddr &&
		    remote == t->parms.iph.daddr &&
		    parms->link == t->parms.link) {
			if (create)
				return NULL;
			else
				return t;
		}
	}
	if (!create)
		goto failed;

	if (parms->name[0]) {
		if (!dev_valid_name(parms->name))
			goto failed;
		strscpy(name, parms->name, IFNAMSIZ);
	} else {
		strcpy(name, "sit%d");
	}
	dev = alloc_netdev(sizeof(*t), name, NET_NAME_UNKNOWN,
			   ipip6_tunnel_setup);
	if (!dev)
		return NULL;

	dev_net_set(dev, net);

	nt = netdev_priv(dev);

	nt->net = net;
	nt->parms = *parms;
	if (ipip6_tunnel_create(dev) < 0)
		goto failed_free;

	if (!parms->name[0])
		strcpy(parms->name, dev->name);

	return nt;

failed_free:
	free_netdev(dev);
failed:
	return NULL;
}

#define for_each_prl_rcu(start)			\
	for (prl = rcu_dereference(start);	\
	     prl;				\
	     prl = rcu_dereference(prl->next))

static struct ip_tunnel_prl_entry *
__ipip6_tunnel_locate_prl(struct ip_tunnel *t, __be32 addr)
{
	struct ip_tunnel_prl_entry *prl;

	for_each_prl_rcu(t->prl)
		if (prl->addr == addr)
			break;
	return prl;

}

static int ipip6_tunnel_get_prl(struct net_device *dev, struct ip_tunnel_prl __user *a)
{
	struct ip_tunnel *t = netdev_priv(dev);
	struct ip_tunnel_prl kprl, *kp;
	struct ip_tunnel_prl_entry *prl;
	unsigned int cmax, c = 0, ca, len;
	int ret = 0;

	if (dev == dev_to_sit_net(dev)->fb_tunnel_dev)
		return -EINVAL;

	if (copy_from_user(&kprl, a, sizeof(kprl)))
		return -EFAULT;
	cmax = kprl.datalen / sizeof(kprl);
	if (cmax > 1 && kprl.addr != htonl(INADDR_ANY))
		cmax = 1;

	/* For simple GET or for root users,
	 * we try harder to allocate.
	 */
	kp = (cmax <= 1 || capable(CAP_NET_ADMIN)) ?
		kcalloc(cmax, sizeof(*kp), GFP_KERNEL_ACCOUNT | __GFP_NOWARN) :
		NULL;

	ca = min(t->prl_count, cmax);

	if (!kp) {
		/* We don't try hard to allocate much memory for
		 * non-root users.
		 * For root users, retry allocating enough memory for
		 * the answer.
		 */
		kp = kcalloc(ca, sizeof(*kp), GFP_ATOMIC | __GFP_ACCOUNT |
					      __GFP_NOWARN);
		if (!kp) {
			ret = -ENOMEM;
			goto out;
		}
	}

	rcu_read_lock();
	for_each_prl_rcu(t->prl) {
		if (c >= cmax)
			break;
		if (kprl.addr != htonl(INADDR_ANY) && prl->addr != kprl.addr)
			continue;
		kp[c].addr = prl->addr;
		kp[c].flags = prl->flags;
		c++;
		if (kprl.addr != htonl(INADDR_ANY))
			break;
	}

	rcu_read_unlock();

	len = sizeof(*kp) * c;
	ret = 0;
	if ((len && copy_to_user(a + 1, kp, len)) || put_user(len, &a->datalen))
		ret = -EFAULT;

	kfree(kp);
out:
	return ret;
}

static int
ipip6_tunnel_add_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a, int chg)
{
	struct ip_tunnel_prl_entry *p;
	int err = 0;

	if (a->addr == htonl(INADDR_ANY))
		return -EINVAL;

	ASSERT_RTNL();

	for (p = rtnl_dereference(t->prl); p; p = rtnl_dereference(p->next)) {
		if (p->addr == a->addr) {
			if (chg) {
				p->flags = a->flags;
				goto out;
			}
			err = -EEXIST;
			goto out;
		}
	}

	if (chg) {
		err = -ENXIO;
		goto out;
	}

	p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_KERNEL);
	if (!p) {
		err = -ENOBUFS;
		goto out;
	}

	p->next = t->prl;
	p->addr = a->addr;
	p->flags = a->flags;
	t->prl_count++;
	rcu_assign_pointer(t->prl, p);
out:
	return err;
}

static void prl_list_destroy_rcu(struct rcu_head *head)
{
	struct ip_tunnel_prl_entry *p, *n;

	p = container_of(head, struct ip_tunnel_prl_entry, rcu_head);
	do {
		n = rcu_dereference_protected(p->next, 1);
		kfree(p);
		p = n;
	} while (p);
}

static int
ipip6_tunnel_del_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a)
{
	struct ip_tunnel_prl_entry *x;
	struct ip_tunnel_prl_entry __rcu **p;
	int err = 0;

	ASSERT_RTNL();

	if (a && a->addr != htonl(INADDR_ANY)) {
		for (p = &t->prl;
		     (x = rtnl_dereference(*p)) != NULL;
		     p = &x->next) {
			if (x->addr == a->addr) {
				*p = x->next;
				kfree_rcu(x, rcu_head);
				t->prl_count--;
				goto out;
			}
		}
		err = -ENXIO;
	} else {
		x = rtnl_dereference(t->prl);
		if (x) {
			t->prl_count = 0;
			call_rcu(&x->rcu_head, prl_list_destroy_rcu);
			t->prl = NULL;
		}
	}
out:
	return err;
}

static int ipip6_tunnel_prl_ctl(struct net_device *dev,
				struct ip_tunnel_prl __user *data, int cmd)
{
	struct ip_tunnel *t = netdev_priv(dev);
	struct ip_tunnel_prl prl;
	int err;

	if (!ns_capable(t->net->user_ns, CAP_NET_ADMIN))
		return -EPERM;
	if (dev == dev_to_sit_net(dev)->fb_tunnel_dev)
		return -EINVAL;

	if (copy_from_user(&prl, data, sizeof(prl)))
		return -EFAULT;

	switch (cmd) {
	case SIOCDELPRL:
		err = ipip6_tunnel_del_prl(t, &prl);
		break;
	case SIOCADDPRL:
	case SIOCCHGPRL:
		err = ipip6_tunnel_add_prl(t, &prl, cmd == SIOCCHGPRL);
		break;
	}
	dst_cache_reset(&t->dst_cache);
	netdev_state_change(dev);
	return err;
}

static int
isatap_chksrc(struct sk_buff *skb, const struct iphdr *iph, struct ip_tunnel *t)
{
	struct ip_tunnel_prl_entry *p;
	int ok = 1;

	rcu_read_lock();
	p = __ipip6_tunnel_locate_prl(t, iph->saddr);
	if (p) {
		if (p->flags & PRL_DEFAULT)
			skb->ndisc_nodetype = NDISC_NODETYPE_DEFAULT;
		else
			skb->ndisc_nodetype = NDISC_NODETYPE_NODEFAULT;
	} else {
		const struct in6_addr *addr6 = &ipv6_hdr(skb)->saddr;

		if (ipv6_addr_is_isatap(addr6) &&
		    (addr6->s6_addr32[3] == iph->saddr) &&
		    ipv6_chk_prefix(addr6, t->dev))
			skb->ndisc_nodetype = NDISC_NODETYPE_HOST;
		else
			ok = 0;
	}
	rcu_read_unlock();
	return ok;
}

static void ipip6_tunnel_uninit(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct sit_net *sitn = net_generic(tunnel->net, sit_net_id);

	if (dev == sitn->fb_tunnel_dev) {
		RCU_INIT_POINTER(sitn->tunnels_wc[0], NULL);
	} else {
		ipip6_tunnel_unlink(sitn, tunnel);
		ipip6_tunnel_del_prl(tunnel, NULL);
	}
	dst_cache_reset(&tunnel->dst_cache);
	netdev_put(dev, &tunnel->dev_tracker);
}

static int ipip6_err(struct sk_buff *skb, u32 info)
{
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	const int type = icmp_hdr(skb)->type;
	const int code = icmp_hdr(skb)->code;
	unsigned int data_len = 0;
	struct ip_tunnel *t;
	int sifindex;
	int err;

	switch (type) {
	default:
	case ICMP_PARAMETERPROB:
		return 0;

	case ICMP_DEST_UNREACH:
		switch (code) {
		case ICMP_SR_FAILED:
			/* Impossible event. */
			return 0;
		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 0;
		data_len = icmp_hdr(skb)->un.reserved[1] * 4; /* RFC 4884 4.1 */
		break;
	case ICMP_REDIRECT:
		break;
	}

	err = -ENOENT;

	sifindex = netif_is_l3_master(skb->dev) ? IPCB(skb)->iif : 0;
	t = ipip6_tunnel_lookup(dev_net(skb->dev), skb->dev,
				iph->daddr, iph->saddr, sifindex);
	if (!t)
		goto out;

	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
		ipv4_update_pmtu(skb, dev_net(skb->dev), info,
				 t->parms.link, iph->protocol);
		err = 0;
		goto out;
	}
	if (type == ICMP_REDIRECT) {
		ipv4_redirect(skb, dev_net(skb->dev), t->parms.link,
			      iph->protocol);
		err = 0;
		goto out;
	}

	err = 0;
	if (__in6_dev_get(skb->dev) &&
	    !ip6_err_gen_icmpv6_unreach(skb, iph->ihl * 4, type, data_len))
		goto out;

	if (t->parms.iph.daddr == 0)
		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:
	return err;
}

static inline bool is_spoofed_6rd(struct ip_tunnel *tunnel, const __be32 v4addr,
				  const struct in6_addr *v6addr)
{
	__be32 v4embed = 0;
	if (check_6rd(tunnel, v6addr, &v4embed) && v4addr != v4embed)
		return true;
	return false;
}

/* Checks if an address matches an address on the tunnel interface.
 * Used to detect the NAT of proto 41 packets and let them pass spoofing test.
 * Long story:
 * This function is called after we considered the packet as spoofed
 * in is_spoofed_6rd.
 * We may have a router that is doing NAT for proto 41 packets
 * for an internal station. Destination a.a.a.a/PREFIX:bbbb:bbbb
 * will be translated to n.n.n.n/PREFIX:bbbb:bbbb. And is_spoofed_6rd
 * function will return true, dropping the packet.
 * But, we can still check if is spoofed against the IP
 * addresses associated with the interface.
 */
static bool only_dnatted(const struct ip_tunnel *tunnel,
	const struct in6_addr *v6dst)
{
	int prefix_len;

#ifdef CONFIG_IPV6_SIT_6RD
	prefix_len = tunnel->ip6rd.prefixlen + 32
		- tunnel->ip6rd.relay_prefixlen;
#else
	prefix_len = 48;
#endif
	return ipv6_chk_custom_prefix(v6dst, prefix_len, tunnel->dev);
}

/* Returns true if a packet is spoofed */
static bool packet_is_spoofed(struct sk_buff *skb,
			      const struct iphdr *iph,
			      struct ip_tunnel *tunnel)
{
	const struct ipv6hdr *ipv6h;

	if (tunnel->dev->priv_flags & IFF_ISATAP) {
		if (!isatap_chksrc(skb, iph, tunnel))
			return true;

		return false;
	}

	if (tunnel->dev->flags & IFF_POINTOPOINT)
		return false;

	ipv6h = ipv6_hdr(skb);

	if (unlikely(is_spoofed_6rd(tunnel, iph->saddr, &ipv6h->saddr))) {
		net_warn_ratelimited("Src spoofed %pI4/%pI6c -> %pI4/%pI6c\n",
				     &iph->saddr, &ipv6h->saddr,
				     &iph->daddr, &ipv6h->daddr);
		return true;
	}

	if (likely(!is_spoofed_6rd(tunnel, iph->daddr, &ipv6h->daddr)))
		return false;

	if (only_dnatted(tunnel, &ipv6h->daddr))
		return false;

	net_warn_ratelimited("Dst spoofed %pI4/%pI6c -> %pI4/%pI6c\n",
			     &iph->saddr, &ipv6h->saddr,
			     &iph->daddr, &ipv6h->daddr);
	return true;
}

static int ipip6_rcv(struct sk_buff *skb)
{
	const struct iphdr *iph = ip_hdr(skb);
	struct ip_tunnel *tunnel;
	int sifindex;
	int err;

	sifindex = netif_is_l3_master(skb->dev) ? IPCB(skb)->iif : 0;
	tunnel = ipip6_tunnel_lookup(dev_net(skb->dev), skb->dev,
				     iph->saddr, iph->daddr, sifindex);
	if (tunnel) {
		if (tunnel->parms.iph.protocol != IPPROTO_IPV6 &&
		    tunnel->parms.iph.protocol != 0)
			goto out;

		skb->mac_header = skb->network_header;
		skb_reset_network_header(skb);
		IPCB(skb)->flags = 0;
		skb->dev = tunnel->dev;

		if (packet_is_spoofed(skb, iph, tunnel)) {
			DEV_STATS_INC(tunnel->dev, rx_errors);
			goto out;
		}

		if (iptunnel_pull_header(skb, 0, htons(ETH_P_IPV6),
		    !net_eq(tunnel->net, dev_net(tunnel->dev))))
			goto out;

		/* skb can be uncloned in iptunnel_pull_header, so
		 * old iph is no longer valid
		 */
		iph = (const struct iphdr *)skb_mac_header(skb);
		skb_reset_mac_header(skb);

		err = IP_ECN_decapsulate(iph, skb);
		if (unlikely(err)) {
			if (log_ecn_error)
				net_info_ratelimited("non-ECT from %pI4 with TOS=%#x\n",
						     &iph->saddr, iph->tos);
			if (err > 1) {
				DEV_STATS_INC(tunnel->dev, rx_frame_errors);
				DEV_STATS_INC(tunnel->dev, rx_errors);
				goto out;
			}
		}

		dev_sw_netstats_rx_add(tunnel->dev, skb->len);

		netif_rx(skb);

		return 0;
	}

	/* no tunnel matched,  let upstream know, ipsec may handle it */
	return 1;
out:
	kfree_skb(skb);
	return 0;
}

static const struct tnl_ptk_info ipip_tpi = {
	/* no tunnel info required for ipip. */
	.proto = htons(ETH_P_IP),
};

#if IS_ENABLED(CONFIG_MPLS)
static const struct tnl_ptk_info mplsip_tpi = {
	/* no tunnel info required for mplsip. */
	.proto = htons(ETH_P_MPLS_UC),
};
#endif

static int sit_tunnel_rcv(struct sk_buff *skb, u8 ipproto)
{
	const struct iphdr *iph;
	struct ip_tunnel *tunnel;
	int sifindex;

	sifindex = netif_is_l3_master(skb->dev) ? IPCB(skb)->iif : 0;

	iph = ip_hdr(skb);
	tunnel = ipip6_tunnel_lookup(dev_net(skb->dev), skb->dev,
				     iph->saddr, iph->daddr, sifindex);
	if (tunnel) {
		const struct tnl_ptk_info *tpi;

		if (tunnel->parms.iph.protocol != ipproto &&
		    tunnel->parms.iph.protocol != 0)
			goto drop;

		if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
			goto drop;
#if IS_ENABLED(CONFIG_MPLS)
		if (ipproto == IPPROTO_MPLS)
			tpi = &mplsip_tpi;
		else
#endif
			tpi = &ipip_tpi;
		if (iptunnel_pull_header(skb, 0, tpi->proto, false))
			goto drop;
		skb_reset_mac_header(skb);

		return ip_tunnel_rcv(tunnel, skb, tpi, NULL, log_ecn_error);
	}

	return 1;

drop:
	kfree_skb(skb);
	return 0;
}

static int ipip_rcv(struct sk_buff *skb)
{
	return sit_tunnel_rcv(skb, IPPROTO_IPIP);
}

#if IS_ENABLED(CONFIG_MPLS)
static int mplsip_rcv(struct sk_buff *skb)
{
	return sit_tunnel_rcv(skb, IPPROTO_MPLS);
}
#endif

/*
 * If the IPv6 address comes from 6rd / 6to4 (RFC 3056) addr space this function
 * stores the embedded IPv4 address in v4dst and returns true.
 */
static bool check_6rd(struct ip_tunnel *tunnel, const struct in6_addr *v6dst,
		      __be32 *v4dst)
{
#ifdef CONFIG_IPV6_SIT_6RD
	if (ipv6_prefix_equal(v6dst, &tunnel->ip6rd.prefix,
			      tunnel->ip6rd.prefixlen)) {
		unsigned int pbw0, pbi0;
		int pbi1;
		u32 d;

		pbw0 = tunnel->ip6rd.prefixlen >> 5;
		pbi0 = tunnel->ip6rd.prefixlen & 0x1f;

		d = tunnel->ip6rd.relay_prefixlen < 32 ?
			(ntohl(v6dst->s6_addr32[pbw0]) << pbi0) >>
		    tunnel->ip6rd.relay_prefixlen : 0;

		pbi1 = pbi0 - tunnel->ip6rd.relay_prefixlen;
		if (pbi1 > 0)
			d |= ntohl(v6dst->s6_addr32[pbw0 + 1]) >>
			     (32 - pbi1);

		*v4dst = tunnel->ip6rd.relay_prefix | htonl(d);
		return true;
	}
#else
	if (v6dst->s6_addr16[0] == htons(0x2002)) {
		/* 6to4 v6 addr has 16 bits prefix, 32 v4addr, 16 SLA, ... */
		memcpy(v4dst, &v6dst->s6_addr16[1], 4);
		return true;
	}
#endif
	return false;
}

static inline __be32 try_6rd(struct ip_tunnel *tunnel,
			     const struct in6_addr *v6dst)
{
	__be32 dst = 0;
	check_6rd(tunnel, v6dst, &dst);
	return dst;
}

/*
 *	This function assumes it is being called from dev_queue_xmit()
 *	and that skb is filled properly by that function.
 */

static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
				     struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	const struct iphdr  *tiph = &tunnel->parms.iph;
	const struct ipv6hdr *iph6 = ipv6_hdr(skb);
	u8     tos = tunnel->parms.iph.tos;
	__be16 df = tiph->frag_off;
	struct rtable *rt;		/* Route to the other host */
	struct net_device *tdev;	/* Device to other host */
	unsigned int max_headroom;	/* The extra header space needed */
	__be32 dst = tiph->daddr;
	struct flowi4 fl4;
	int    mtu;
	const struct in6_addr *addr6;
	int addr_type;
	u8 ttl;
	u8 protocol = IPPROTO_IPV6;
	int t_hlen = tunnel->hlen + sizeof(struct iphdr);

	if (tos == 1)
		tos = ipv6_get_dsfield(iph6);

	/* ISATAP (RFC4214) - must come before 6to4 */
	if (dev->priv_flags & IFF_ISATAP) {
		struct neighbour *neigh = NULL;
		bool do_tx_error = false;

		if (skb_dst(skb))
			neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);

		if (!neigh) {
			net_dbg_ratelimited("nexthop == NULL\n");
			goto tx_error;
		}

		addr6 = (const struct in6_addr *)&neigh->primary_key;
		addr_type = ipv6_addr_type(addr6);

		if ((addr_type & IPV6_ADDR_UNICAST) &&
		     ipv6_addr_is_isatap(addr6))
			dst = addr6->s6_addr32[3];
		else
			do_tx_error = true;

		neigh_release(neigh);
		if (do_tx_error)
			goto tx_error;
	}

	if (!dst)
		dst = try_6rd(tunnel, &iph6->daddr);

	if (!dst) {
		struct neighbour *neigh = NULL;
		bool do_tx_error = false;

		if (skb_dst(skb))
			neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);

		if (!neigh) {
			net_dbg_ratelimited("nexthop == NULL\n");
			goto tx_error;
		}

		addr6 = (const 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)
			dst = addr6->s6_addr32[3];
		else
			do_tx_error = true;

		neigh_release(neigh);
		if (do_tx_error)
			goto tx_error;
	}

	flowi4_init_output(&fl4, tunnel->parms.link, tunnel->fwmark,
			   tos & INET_DSCP_MASK, RT_SCOPE_UNIVERSE,
			   IPPROTO_IPV6, 0, dst, tiph->saddr, 0, 0,
			   sock_net_uid(tunnel->net, NULL));

	rt = dst_cache_get_ip4(&tunnel->dst_cache, &fl4.saddr);
	if (!rt) {
		rt = ip_route_output_flow(tunnel->net, &fl4, NULL);
		if (IS_ERR(rt)) {
			DEV_STATS_INC(dev, tx_carrier_errors);
			goto tx_error_icmp;
		}
		dst_cache_set_ip4(&tunnel->dst_cache, &rt->dst, fl4.saddr);
	}

	if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
		ip_rt_put(rt);
		DEV_STATS_INC(dev, tx_carrier_errors);
		goto tx_error_icmp;
	}
	tdev = rt->dst.dev;

	if (tdev == dev) {
		ip_rt_put(rt);
		DEV_STATS_INC(dev, collisions);
		goto tx_error;
	}

	if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP4)) {
		ip_rt_put(rt);
		goto tx_error;
	}

	if (df) {
		mtu = dst_mtu(&rt->dst) - t_hlen;

		if (mtu < IPV4_MIN_MTU) {
			DEV_STATS_INC(dev, collisions);
			ip_rt_put(rt);
			goto tx_error;
		}

		if (mtu < IPV6_MIN_MTU) {
			mtu = IPV6_MIN_MTU;
			df = 0;
		}

		if (tunnel->parms.iph.daddr)
			skb_dst_update_pmtu_no_confirm(skb, mtu);

		if (skb->len > mtu && !skb_is_gso(skb)) {
			icmpv6_ndo_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
			ip_rt_put(rt);
			goto tx_error;
		}
	}

	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;
	}

	/*
	 * Okay, now see if we can stuff it in the buffer as-is.
	 */
	max_headroom = LL_RESERVED_SPACE(tdev) + t_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);
			DEV_STATS_INC(dev, tx_dropped);
			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;
		iph6 = ipv6_hdr(skb);
	}
	ttl = tiph->ttl;
	if (ttl == 0)
		ttl = iph6->hop_limit;
	tos = INET_ECN_encapsulate(tos, ipv6_get_dsfield(iph6));

	if (ip_tunnel_encap(skb, &tunnel->encap, &protocol, &fl4) < 0) {
		ip_rt_put(rt);
		goto tx_error;
	}

	skb_set_inner_ipproto(skb, IPPROTO_IPV6);

	iptunnel_xmit(NULL, rt, skb, fl4.saddr, fl4.daddr, protocol, tos, ttl,
		      df, !net_eq(tunnel->net, dev_net(dev)));
	return NETDEV_TX_OK;

tx_error_icmp:
	dst_link_failure(skb);
tx_error:
	kfree_skb(skb);
	DEV_STATS_INC(dev, tx_errors);
	return NETDEV_TX_OK;
}

static netdev_tx_t sit_tunnel_xmit__(struct sk_buff *skb,
				     struct net_device *dev, u8 ipproto)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	const struct iphdr  *tiph = &tunnel->parms.iph;

	if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP4))
		goto tx_error;

	skb_set_inner_ipproto(skb, ipproto);

	ip_tunnel_xmit(skb, dev, tiph, ipproto);
	return NETDEV_TX_OK;
tx_error:
	kfree_skb(skb);
	DEV_STATS_INC(dev, tx_errors);
	return NETDEV_TX_OK;
}

static netdev_tx_t sit_tunnel_xmit(struct sk_buff *skb,
				   struct net_device *dev)
{
	if (!pskb_inet_may_pull(skb))
		goto tx_err;

	switch (skb->protocol) {
	case htons(ETH_P_IP):
		sit_tunnel_xmit__(skb, dev, IPPROTO_IPIP);
		break;
	case htons(ETH_P_IPV6):
		ipip6_tunnel_xmit(skb, dev);
		break;
#if IS_ENABLED(CONFIG_MPLS)
	case htons(ETH_P_MPLS_UC):
		sit_tunnel_xmit__(skb, dev, IPPROTO_MPLS);
		break;
#endif
	default:
		goto tx_err;
	}

	return NETDEV_TX_OK;

tx_err:
	DEV_STATS_INC(dev, tx_errors);
	kfree_skb(skb);
	return NETDEV_TX_OK;

}

static void ipip6_tunnel_bind_dev(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	int t_hlen = tunnel->hlen + sizeof(struct iphdr);
	struct net_device *tdev = NULL;
	int hlen = LL_MAX_HEADER;
	const struct iphdr *iph;
	struct flowi4 fl4;

	iph = &tunnel->parms.iph;

	if (iph->daddr) {
		struct rtable *rt = ip_route_output_ports(tunnel->net, &fl4,
							  NULL,
							  iph->daddr, iph->saddr,
							  0, 0,
							  IPPROTO_IPV6,
							  iph->tos & INET_DSCP_MASK,
							  tunnel->parms.link);

		if (!IS_ERR(rt)) {
			tdev = rt->dst.dev;
			ip_rt_put(rt);
		}
		dev->flags |= IFF_POINTOPOINT;
	}

	if (!tdev && tunnel->parms.link)
		tdev = __dev_get_by_index(tunnel->net, tunnel->parms.link);

	if (tdev && !netif_is_l3_master(tdev)) {
		int mtu;

		mtu = tdev->mtu - t_hlen;
		if (mtu < IPV6_MIN_MTU)
			mtu = IPV6_MIN_MTU;
		WRITE_ONCE(dev->mtu, mtu);
		hlen = tdev->hard_header_len + tdev->needed_headroom;
	}
	dev->needed_headroom = t_hlen + hlen;
}

static void ipip6_tunnel_update(struct ip_tunnel *t,
				struct ip_tunnel_parm_kern *p,
				__u32 fwmark)
{
	struct net *net = t->net;
	struct sit_net *sitn = net_generic(net, sit_net_id);

	ipip6_tunnel_unlink(sitn, t);
	synchronize_net();
	t->parms.iph.saddr = p->iph.saddr;
	t->parms.iph.daddr = p->iph.daddr;
	__dev_addr_set(t->dev, &p->iph.saddr, 4);
	memcpy(t->dev->broadcast, &p->iph.daddr, 4);
	ipip6_tunnel_link(sitn, t);
	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->fwmark != fwmark) {
		t->parms.link = p->link;
		t->fwmark = fwmark;
		ipip6_tunnel_bind_dev(t->dev);
	}
	dst_cache_reset(&t->dst_cache);
	netdev_state_change(t->dev);
}

#ifdef CONFIG_IPV6_SIT_6RD
static int ipip6_tunnel_update_6rd(struct ip_tunnel *t,
				   struct ip_tunnel_6rd *ip6rd)
{
	struct in6_addr prefix;
	__be32 relay_prefix;

	if (ip6rd->relay_prefixlen > 32 ||
	    ip6rd->prefixlen + (32 - ip6rd->relay_prefixlen) > 64)
		return -EINVAL;

	ipv6_addr_prefix(&prefix, &ip6rd->prefix, ip6rd->prefixlen);
	if (!ipv6_addr_equal(&prefix, &ip6rd->prefix))
		return -EINVAL;
	if (ip6rd->relay_prefixlen)
		relay_prefix = ip6rd->relay_prefix &
			       htonl(0xffffffffUL <<
				     (32 - ip6rd->relay_prefixlen));
	else
		relay_prefix = 0;
	if (relay_prefix != ip6rd->relay_prefix)
		return -EINVAL;

	t->ip6rd.prefix = prefix;
	t->ip6rd.relay_prefix = relay_prefix;
	t->ip6rd.prefixlen = ip6rd->prefixlen;
	t->ip6rd.relay_prefixlen = ip6rd->relay_prefixlen;
	dst_cache_reset(&t->dst_cache);
	netdev_state_change(t->dev);
	return 0;
}

static int
ipip6_tunnel_get6rd(struct net_device *dev, struct ip_tunnel_parm __user *data)
{
	struct ip_tunnel *t = netdev_priv(dev);
	struct ip_tunnel_parm_kern p;
	struct ip_tunnel_6rd ip6rd;

	if (dev == dev_to_sit_net(dev)->fb_tunnel_dev) {
		if (!ip_tunnel_parm_from_user(&p, data))
			return -EFAULT;
		t = ipip6_tunnel_locate(t->net, &p, 0);
	}
	if (!t)
		t = netdev_priv(dev);

	ip6rd.prefix = t->ip6rd.prefix;
	ip6rd.relay_prefix = t->ip6rd.relay_prefix;
	ip6rd.prefixlen = t->ip6rd.prefixlen;
	ip6rd.relay_prefixlen = t->ip6rd.relay_prefixlen;
	if (copy_to_user(data, &ip6rd, sizeof(ip6rd)))
		return -EFAULT;
	return 0;
}

static int
ipip6_tunnel_6rdctl(struct net_device *dev, struct ip_tunnel_6rd __user *data,
		    int cmd)
{
	struct ip_tunnel *t = netdev_priv(dev);
	struct ip_tunnel_6rd ip6rd;
	int err;

	if (!ns_capable(t->net->user_ns, CAP_NET_ADMIN))
		return -EPERM;
	if (copy_from_user(&ip6rd, data, sizeof(ip6rd)))
		return -EFAULT;

	if (cmd != SIOCDEL6RD) {
		err = ipip6_tunnel_update_6rd(t, &ip6rd);
		if (err < 0)
			return err;
	} else
		ipip6_tunnel_clone_6rd(dev, dev_to_sit_net(dev));
	return 0;
}

#endif /* CONFIG_IPV6_SIT_6RD */

static bool ipip6_valid_ip_proto(u8 ipproto)
{
	return ipproto == IPPROTO_IPV6 ||
		ipproto == IPPROTO_IPIP ||
#if IS_ENABLED(CONFIG_MPLS)
		ipproto == IPPROTO_MPLS ||
#endif
		ipproto == 0;
}

static int
__ipip6_tunnel_ioctl_validate(struct net *net, struct ip_tunnel_parm_kern *p)
{
	if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
		return -EPERM;

	if (!ipip6_valid_ip_proto(p->iph.protocol))
		return -EINVAL;
	if (p->iph.version != 4 ||
	    p->iph.ihl != 5 || (p->iph.frag_off & htons(~IP_DF)))
		return -EINVAL;

	if (p->iph.ttl)
		p->iph.frag_off |= htons(IP_DF);
	return 0;
}

static int
ipip6_tunnel_get(struct net_device *dev, struct ip_tunnel_parm_kern *p)
{
	struct ip_tunnel *t = netdev_priv(dev);

	if (dev == dev_to_sit_net(dev)->fb_tunnel_dev)
		t = ipip6_tunnel_locate(t->net, p, 0);
	if (!t)
		t = netdev_priv(dev);
	memcpy(p, &t->parms, sizeof(*p));
	return 0;
}

static int
ipip6_tunnel_add(struct net_device *dev, struct ip_tunnel_parm_kern *p)
{
	struct ip_tunnel *t = netdev_priv(dev);
	int err;

	err = __ipip6_tunnel_ioctl_validate(t->net, p);
	if (err)
		return err;

	t = ipip6_tunnel_locate(t->net, p, 1);
	if (!t)
		return -ENOBUFS;
	return 0;
}

static int
ipip6_tunnel_change(struct net_device *dev, struct ip_tunnel_parm_kern *p)
{
	struct ip_tunnel *t = netdev_priv(dev);
	int err;

	err = __ipip6_tunnel_ioctl_validate(t->net, p);
	if (err)
		return err;

	t = ipip6_tunnel_locate(t->net, p, 0);
	if (dev == dev_to_sit_net(dev)->fb_tunnel_dev) {
		if (!t)
			return -ENOENT;
	} else {
		if (t) {
			if (t->dev != dev)
				return -EEXIST;
		} else {
			if (((dev->flags & IFF_POINTOPOINT) && !p->iph.daddr) ||
			    (!(dev->flags & IFF_POINTOPOINT) && p->iph.daddr))
				return -EINVAL;
			t = netdev_priv(dev);
		}

		ipip6_tunnel_update(t, p, t->fwmark);
	}

	return 0;
}

static int
ipip6_tunnel_del(struct net_device *dev, struct ip_tunnel_parm_kern *p)
{
	struct ip_tunnel *t = netdev_priv(dev);

	if (!ns_capable(t->net->user_ns, CAP_NET_ADMIN))
		return -EPERM;

	if (dev == dev_to_sit_net(dev)->fb_tunnel_dev) {
		t = ipip6_tunnel_locate(t->net, p, 0);
		if (!t)
			return -ENOENT;
		if (t == netdev_priv(dev_to_sit_net(dev)->fb_tunnel_dev))
			return -EPERM;
		dev = t->dev;
	}
	unregister_netdevice(dev);
	return 0;
}

static int
ipip6_tunnel_ctl(struct net_device *dev, struct ip_tunnel_parm_kern *p,
		 int cmd)
{
	switch (cmd) {
	case SIOCGETTUNNEL:
		return ipip6_tunnel_get(dev, p);
	case SIOCADDTUNNEL:
		return ipip6_tunnel_add(dev, p);
	case SIOCCHGTUNNEL:
		return ipip6_tunnel_change(dev, p);
	case SIOCDELTUNNEL:
		return ipip6_tunnel_del(dev, p);
	default:
		return -EINVAL;
	}
}

static int
ipip6_tunnel_siocdevprivate(struct net_device *dev, struct ifreq *ifr,
			    void __user *data, int cmd)
{
	switch (cmd) {
	case SIOCGETTUNNEL:
	case SIOCADDTUNNEL:
	case SIOCCHGTUNNEL:
	case SIOCDELTUNNEL:
		return ip_tunnel_siocdevprivate(dev, ifr, data, cmd);
	case SIOCGETPRL:
		return ipip6_tunnel_get_prl(dev, data);
	case SIOCADDPRL:
	case SIOCDELPRL:
	case SIOCCHGPRL:
		return ipip6_tunnel_prl_ctl(dev, data, cmd);
#ifdef CONFIG_IPV6_SIT_6RD
	case SIOCGET6RD:
		return ipip6_tunnel_get6rd(dev, data);
	case SIOCADD6RD:
	case SIOCCHG6RD:
	case SIOCDEL6RD:
		return ipip6_tunnel_6rdctl(dev, data, cmd);
#endif
	default:
		return -EINVAL;
	}
}

static const struct net_device_ops ipip6_netdev_ops = {
	.ndo_init	= ipip6_tunnel_init,
	.ndo_uninit	= ipip6_tunnel_uninit,
	.ndo_start_xmit	= sit_tunnel_xmit,
	.ndo_siocdevprivate = ipip6_tunnel_siocdevprivate,
	.ndo_get_iflink = ip_tunnel_get_iflink,
	.ndo_tunnel_ctl = ipip6_tunnel_ctl,
};

static void ipip6_dev_free(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);

	dst_cache_destroy(&tunnel->dst_cache);
}

#define SIT_FEATURES (NETIF_F_SG	   | \
		      NETIF_F_FRAGLIST	   | \
		      NETIF_F_HIGHDMA	   | \
		      NETIF_F_GSO_SOFTWARE | \
		      NETIF_F_HW_CSUM)

static void ipip6_tunnel_setup(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	int t_hlen = tunnel->hlen + sizeof(struct iphdr);

	dev->netdev_ops		= &ipip6_netdev_ops;
	dev->header_ops		= &ip_tunnel_header_ops;
	dev->needs_free_netdev	= true;
	dev->priv_destructor	= ipip6_dev_free;

	dev->type		= ARPHRD_SIT;
	dev->mtu		= ETH_DATA_LEN - t_hlen;
	dev->min_mtu		= IPV6_MIN_MTU;
	dev->max_mtu		= IP6_MAX_MTU - t_hlen;
	dev->flags		= IFF_NOARP;
	netif_keep_dst(dev);
	dev->addr_len		= 4;
	dev->lltx		= true;
	dev->features		|= SIT_FEATURES;
	dev->hw_features	|= SIT_FEATURES;
	dev->pcpu_stat_type	= NETDEV_PCPU_STAT_TSTATS;

}

static int ipip6_tunnel_init(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	int err;

	tunnel->dev = dev;
	strcpy(tunnel->parms.name, dev->name);

	ipip6_tunnel_bind_dev(dev);

	err = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL);
	if (err)
		return err;

	netdev_hold(dev, &tunnel->dev_tracker, GFP_KERNEL);
	netdev_lockdep_set_classes(dev);
	return 0;
}

static void __net_init ipip6_fb_tunnel_init(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct iphdr *iph = &tunnel->parms.iph;
	struct net *net = dev_net(dev);
	struct sit_net *sitn = net_generic(net, sit_net_id);

	iph->version		= 4;
	iph->protocol		= IPPROTO_IPV6;
	iph->ihl		= 5;
	iph->ttl		= 64;

	rcu_assign_pointer(sitn->tunnels_wc[0], tunnel);
}

static int ipip6_validate(struct nlattr *tb[], struct nlattr *data[],
			  struct netlink_ext_ack *extack)
{
	u8 proto;

	if (!data || !data[IFLA_IPTUN_PROTO])
		return 0;

	proto = nla_get_u8(data[IFLA_IPTUN_PROTO]);
	if (!ipip6_valid_ip_proto(proto))
		return -EINVAL;

	return 0;
}

static void ipip6_netlink_parms(struct nlattr *data[],
				struct ip_tunnel_parm_kern *parms,
				__u32 *fwmark)
{
	memset(parms, 0, sizeof(*parms));

	parms->iph.version = 4;
	parms->iph.protocol = IPPROTO_IPV6;
	parms->iph.ihl = 5;
	parms->iph.ttl = 64;

	if (!data)
		return;

	ip_tunnel_netlink_parms(data, parms);

	if (data[IFLA_IPTUN_FWMARK])
		*fwmark = nla_get_u32(data[IFLA_IPTUN_FWMARK]);
}

#ifdef CONFIG_IPV6_SIT_6RD
/* This function returns true when 6RD attributes are present in the nl msg */
static bool ipip6_netlink_6rd_parms(struct nlattr *data[],
				    struct ip_tunnel_6rd *ip6rd)
{
	bool ret = false;
	memset(ip6rd, 0, sizeof(*ip6rd));

	if (!data)
		return ret;

	if (data[IFLA_IPTUN_6RD_PREFIX]) {
		ret = true;
		ip6rd->prefix = nla_get_in6_addr(data[IFLA_IPTUN_6RD_PREFIX]);
	}

	if (data[IFLA_IPTUN_6RD_RELAY_PREFIX]) {
		ret = true;
		ip6rd->relay_prefix =
			nla_get_be32(data[IFLA_IPTUN_6RD_RELAY_PREFIX]);
	}

	if (data[IFLA_IPTUN_6RD_PREFIXLEN]) {
		ret = true;
		ip6rd->prefixlen = nla_get_u16(data[IFLA_IPTUN_6RD_PREFIXLEN]);
	}

	if (data[IFLA_IPTUN_6RD_RELAY_PREFIXLEN]) {
		ret = true;
		ip6rd->relay_prefixlen =
			nla_get_u16(data[IFLA_IPTUN_6RD_RELAY_PREFIXLEN]);
	}

	return ret;
}
#endif

static int ipip6_newlink(struct net_device *dev,
			 struct rtnl_newlink_params *params,
			 struct netlink_ext_ack *extack)
{
	struct nlattr **data = params->data;
	struct nlattr **tb = params->tb;
	struct ip_tunnel *nt;
	struct ip_tunnel_encap ipencap;
#ifdef CONFIG_IPV6_SIT_6RD
	struct ip_tunnel_6rd ip6rd;
#endif
	struct net *net;
	int err;

	net = params->link_net ? : dev_net(dev);
	nt = netdev_priv(dev);
	nt->net = net;

	if (ip_tunnel_netlink_encap_parms(data, &ipencap)) {
		err = ip_tunnel_encap_setup(nt, &ipencap);
		if (err < 0)
			return err;
	}

	ipip6_netlink_parms(data, &nt->parms, &nt->fwmark);

	if (ipip6_tunnel_locate(net, &nt->parms, 0))
		return -EEXIST;

	err = ipip6_tunnel_create(dev);
	if (err < 0)
		return err;

	if (tb[IFLA_MTU]) {
		u32 mtu = nla_get_u32(tb[IFLA_MTU]);

		if (mtu >= IPV6_MIN_MTU &&
		    mtu <= IP6_MAX_MTU - dev->hard_header_len)
			dev->mtu = mtu;
	}

#ifdef CONFIG_IPV6_SIT_6RD
	if (ipip6_netlink_6rd_parms(data, &ip6rd)) {
		err = ipip6_tunnel_update_6rd(nt, &ip6rd);
		if (err < 0)
			unregister_netdevice_queue(dev, NULL);
	}
#endif

	return err;
}

static int ipip6_changelink(struct net_device *dev, struct nlattr *tb[],
			    struct nlattr *data[],
			    struct netlink_ext_ack *extack)
{
	struct ip_tunnel *t = netdev_priv(dev);
	struct ip_tunnel_encap ipencap;
	struct ip_tunnel_parm_kern p;
	struct net *net = t->net;
	struct sit_net *sitn = net_generic(net, sit_net_id);
#ifdef CONFIG_IPV6_SIT_6RD
	struct ip_tunnel_6rd ip6rd;
#endif
	__u32 fwmark = t->fwmark;
	int err;

	if (dev == sitn->fb_tunnel_dev)
		return -EINVAL;

	if (ip_tunnel_netlink_encap_parms(data, &ipencap)) {
		err = ip_tunnel_encap_setup(t, &ipencap);
		if (err < 0)
			return err;
	}

	ipip6_netlink_parms(data, &p, &fwmark);

	if (((dev->flags & IFF_POINTOPOINT) && !p.iph.daddr) ||
	    (!(dev->flags & IFF_POINTOPOINT) && p.iph.daddr))
		return -EINVAL;

	t = ipip6_tunnel_locate(net, &p, 0);

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

	ipip6_tunnel_update(t, &p, fwmark);

#ifdef CONFIG_IPV6_SIT_6RD
	if (ipip6_netlink_6rd_parms(data, &ip6rd))
		return ipip6_tunnel_update_6rd(t, &ip6rd);
#endif

	return 0;
}

static size_t ipip6_get_size(const struct net_device *dev)
{
	return
		/* IFLA_IPTUN_LINK */
		nla_total_size(4) +
		/* IFLA_IPTUN_LOCAL */
		nla_total_size(4) +
		/* IFLA_IPTUN_REMOTE */
		nla_total_size(4) +
		/* IFLA_IPTUN_TTL */
		nla_total_size(1) +
		/* IFLA_IPTUN_TOS */
		nla_total_size(1) +
		/* IFLA_IPTUN_PMTUDISC */
		nla_total_size(1) +
		/* IFLA_IPTUN_FLAGS */
		nla_total_size(2) +
		/* IFLA_IPTUN_PROTO */
		nla_total_size(1) +
#ifdef CONFIG_IPV6_SIT_6RD
		/* IFLA_IPTUN_6RD_PREFIX */
		nla_total_size(sizeof(struct in6_addr)) +
		/* IFLA_IPTUN_6RD_RELAY_PREFIX */
		nla_total_size(4) +
		/* IFLA_IPTUN_6RD_PREFIXLEN */
		nla_total_size(2) +
		/* IFLA_IPTUN_6RD_RELAY_PREFIXLEN */
		nla_total_size(2) +
#endif
		/* IFLA_IPTUN_ENCAP_TYPE */
		nla_total_size(2) +
		/* IFLA_IPTUN_ENCAP_FLAGS */
		nla_total_size(2) +
		/* IFLA_IPTUN_ENCAP_SPORT */
		nla_total_size(2) +
		/* IFLA_IPTUN_ENCAP_DPORT */
		nla_total_size(2) +
		/* IFLA_IPTUN_FWMARK */
		nla_total_size(4) +
		0;
}

static int ipip6_fill_info(struct sk_buff *skb, const struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct ip_tunnel_parm_kern *parm = &tunnel->parms;

	if (nla_put_u32(skb, IFLA_IPTUN_LINK, parm->link) ||
	    nla_put_in_addr(skb, IFLA_IPTUN_LOCAL, parm->iph.saddr) ||
	    nla_put_in_addr(skb, IFLA_IPTUN_REMOTE, parm->iph.daddr) ||
	    nla_put_u8(skb, IFLA_IPTUN_TTL, parm->iph.ttl) ||
	    nla_put_u8(skb, IFLA_IPTUN_TOS, parm->iph.tos) ||
	    nla_put_u8(skb, IFLA_IPTUN_PMTUDISC,
		       !!(parm->iph.frag_off & htons(IP_DF))) ||
	    nla_put_u8(skb, IFLA_IPTUN_PROTO, parm->iph.protocol) ||
	    nla_put_be16(skb, IFLA_IPTUN_FLAGS,
			 ip_tunnel_flags_to_be16(parm->i_flags)) ||
	    nla_put_u32(skb, IFLA_IPTUN_FWMARK, tunnel->fwmark))
		goto nla_put_failure;

#ifdef CONFIG_IPV6_SIT_6RD
	if (nla_put_in6_addr(skb, IFLA_IPTUN_6RD_PREFIX,
			     &tunnel->ip6rd.prefix) ||
	    nla_put_in_addr(skb, IFLA_IPTUN_6RD_RELAY_PREFIX,
			    tunnel->ip6rd.relay_prefix) ||
	    nla_put_u16(skb, IFLA_IPTUN_6RD_PREFIXLEN,
			tunnel->ip6rd.prefixlen) ||
	    nla_put_u16(skb, IFLA_IPTUN_6RD_RELAY_PREFIXLEN,
			tunnel->ip6rd.relay_prefixlen))
		goto nla_put_failure;
#endif

	if (nla_put_u16(skb, IFLA_IPTUN_ENCAP_TYPE,
			tunnel->encap.type) ||
	    nla_put_be16(skb, IFLA_IPTUN_ENCAP_SPORT,
			tunnel->encap.sport) ||
	    nla_put_be16(skb, IFLA_IPTUN_ENCAP_DPORT,
			tunnel->encap.dport) ||
	    nla_put_u16(skb, IFLA_IPTUN_ENCAP_FLAGS,
			tunnel->encap.flags))
		goto nla_put_failure;

	return 0;

nla_put_failure:
	return -EMSGSIZE;
}

static const struct nla_policy ipip6_policy[IFLA_IPTUN_MAX + 1] = {
	[IFLA_IPTUN_LINK]		= { .type = NLA_U32 },
	[IFLA_IPTUN_LOCAL]		= { .type = NLA_U32 },
	[IFLA_IPTUN_REMOTE]		= { .type = NLA_U32 },
	[IFLA_IPTUN_TTL]		= { .type = NLA_U8 },
	[IFLA_IPTUN_TOS]		= { .type = NLA_U8 },
	[IFLA_IPTUN_PMTUDISC]		= { .type = NLA_U8 },
	[IFLA_IPTUN_FLAGS]		= { .type = NLA_U16 },
	[IFLA_IPTUN_PROTO]		= { .type = NLA_U8 },
#ifdef CONFIG_IPV6_SIT_6RD
	[IFLA_IPTUN_6RD_PREFIX]		= { .len = sizeof(struct in6_addr) },
	[IFLA_IPTUN_6RD_RELAY_PREFIX]	= { .type = NLA_U32 },
	[IFLA_IPTUN_6RD_PREFIXLEN]	= { .type = NLA_U16 },
	[IFLA_IPTUN_6RD_RELAY_PREFIXLEN] = { .type = NLA_U16 },
#endif
	[IFLA_IPTUN_ENCAP_TYPE]		= { .type = NLA_U16 },
	[IFLA_IPTUN_ENCAP_FLAGS]	= { .type = NLA_U16 },
	[IFLA_IPTUN_ENCAP_SPORT]	= { .type = NLA_U16 },
	[IFLA_IPTUN_ENCAP_DPORT]	= { .type = NLA_U16 },
	[IFLA_IPTUN_FWMARK]		= { .type = NLA_U32 },
};

static void ipip6_dellink(struct net_device *dev, struct list_head *head)
{
	struct net *net = dev_net(dev);
	struct sit_net *sitn = net_generic(net, sit_net_id);

	if (dev != sitn->fb_tunnel_dev)
		unregister_netdevice_queue(dev, head);
}

static struct rtnl_link_ops sit_link_ops __read_mostly = {
	.kind		= "sit",
	.maxtype	= IFLA_IPTUN_MAX,
	.policy		= ipip6_policy,
	.priv_size	= sizeof(struct ip_tunnel),
	.setup		= ipip6_tunnel_setup,
	.validate	= ipip6_validate,
	.newlink	= ipip6_newlink,
	.changelink	= ipip6_changelink,
	.get_size	= ipip6_get_size,
	.fill_info	= ipip6_fill_info,
	.dellink	= ipip6_dellink,
	.get_link_net	= ip_tunnel_get_link_net,
};

static struct xfrm_tunnel sit_handler __read_mostly = {
	.handler	=	ipip6_rcv,
	.err_handler	=	ipip6_err,
	.priority	=	1,
};

static struct xfrm_tunnel ipip_handler __read_mostly = {
	.handler	=	ipip_rcv,
	.err_handler	=	ipip6_err,
	.priority	=	2,
};

#if IS_ENABLED(CONFIG_MPLS)
static struct xfrm_tunnel mplsip_handler __read_mostly = {
	.handler	=	mplsip_rcv,
	.err_handler	=	ipip6_err,
	.priority	=	2,
};
#endif

static void __net_exit sit_destroy_tunnels(struct net *net,
					   struct list_head *head)
{
	struct sit_net *sitn = net_generic(net, sit_net_id);
	struct net_device *dev, *aux;
	int prio;

	for_each_netdev_safe(net, dev, aux)
		if (dev->rtnl_link_ops == &sit_link_ops)
			unregister_netdevice_queue(dev, head);

	for (prio = 0; prio < 4; prio++) {
		int h;
		for (h = 0; h < (prio ? IP6_SIT_HASH_SIZE : 1); h++) {
			struct ip_tunnel *t;

			t = rtnl_dereference(sitn->tunnels[prio][h]);
			while (t) {
				/* If dev is in the same netns, it has already
				 * been added to the list by the previous loop.
				 */
				if (!net_eq(dev_net(t->dev), net))
					unregister_netdevice_queue(t->dev,
								   head);
				t = rtnl_dereference(t->next);
			}
		}
	}
}

static int __net_init sit_init_net(struct net *net)
{
	struct sit_net *sitn = net_generic(net, sit_net_id);
	struct ip_tunnel *t;
	int err;

	sitn->tunnels[0] = sitn->tunnels_wc;
	sitn->tunnels[1] = sitn->tunnels_l;
	sitn->tunnels[2] = sitn->tunnels_r;
	sitn->tunnels[3] = sitn->tunnels_r_l;

	if (!net_has_fallback_tunnels(net))
		return 0;

	sitn->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "sit0",
					   NET_NAME_UNKNOWN,
					   ipip6_tunnel_setup);
	if (!sitn->fb_tunnel_dev) {
		err = -ENOMEM;
		goto err_alloc_dev;
	}
	dev_net_set(sitn->fb_tunnel_dev, net);
	sitn->fb_tunnel_dev->rtnl_link_ops = &sit_link_ops;
	/* FB netdevice is special: we have one, and only one per netns.
	 * Allowing to move it to another netns is clearly unsafe.
	 */
	sitn->fb_tunnel_dev->netns_immutable = true;

	t = netdev_priv(sitn->fb_tunnel_dev);
	t->net = net;

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

	ipip6_tunnel_clone_6rd(sitn->fb_tunnel_dev, sitn);
	ipip6_fb_tunnel_init(sitn->fb_tunnel_dev);

	strcpy(t->parms.name, sitn->fb_tunnel_dev->name);
	return 0;

err_reg_dev:
	free_netdev(sitn->fb_tunnel_dev);
err_alloc_dev:
	return err;
}

static void __net_exit sit_exit_batch_rtnl(struct list_head *net_list,
					   struct list_head *dev_to_kill)
{
	struct net *net;

	ASSERT_RTNL();
	list_for_each_entry(net, net_list, exit_list)
		sit_destroy_tunnels(net, dev_to_kill);
}

static struct pernet_operations sit_net_ops = {
	.init = sit_init_net,
	.exit_batch_rtnl = sit_exit_batch_rtnl,
	.id   = &sit_net_id,
	.size = sizeof(struct sit_net),
};

static void __exit sit_cleanup(void)
{
	rtnl_link_unregister(&sit_link_ops);
	xfrm4_tunnel_deregister(&sit_handler, AF_INET6);
	xfrm4_tunnel_deregister(&ipip_handler, AF_INET);
#if IS_ENABLED(CONFIG_MPLS)
	xfrm4_tunnel_deregister(&mplsip_handler, AF_MPLS);
#endif

	unregister_pernet_device(&sit_net_ops);
	rcu_barrier(); /* Wait for completion of call_rcu()'s */
}

static int __init sit_init(void)
{
	int err;

	pr_info("IPv6, IPv4 and MPLS over IPv4 tunneling driver\n");

	err = register_pernet_device(&sit_net_ops);
	if (err < 0)
		return err;
	err = xfrm4_tunnel_register(&sit_handler, AF_INET6);
	if (err < 0) {
		pr_info("%s: can't register ip6ip4\n", __func__);
		goto xfrm_tunnel_failed;
	}
	err = xfrm4_tunnel_register(&ipip_handler, AF_INET);
	if (err < 0) {
		pr_info("%s: can't register ip4ip4\n", __func__);
		goto xfrm_tunnel4_failed;
	}
#if IS_ENABLED(CONFIG_MPLS)
	err = xfrm4_tunnel_register(&mplsip_handler, AF_MPLS);
	if (err < 0) {
		pr_info("%s: can't register mplsip\n", __func__);
		goto xfrm_tunnel_mpls_failed;
	}
#endif
	err = rtnl_link_register(&sit_link_ops);
	if (err < 0)
		goto rtnl_link_failed;

out:
	return err;

rtnl_link_failed:
#if IS_ENABLED(CONFIG_MPLS)
	xfrm4_tunnel_deregister(&mplsip_handler, AF_MPLS);
xfrm_tunnel_mpls_failed:
#endif
	xfrm4_tunnel_deregister(&ipip_handler, AF_INET);
xfrm_tunnel4_failed:
	xfrm4_tunnel_deregister(&sit_handler, AF_INET6);
xfrm_tunnel_failed:
	unregister_pernet_device(&sit_net_ops);
	goto out;
}

module_init(sit_init);
module_exit(sit_cleanup);
MODULE_DESCRIPTION("IPv6-in-IPv4 tunnel SIT driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK("sit");
MODULE_ALIAS_NETDEV("sit0");