/*
   *	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>
   *

   *	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.
   *
   *	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>

  
  /*
     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;

  };

  /*
   * 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)

  {

  	unsigned int h0 = HASH(remote);
  	unsigned int h1 = HASH(local);

  	struct ip_tunnel *t;

  	struct sit_net *sitn = net_generic(net, sit_net_id);

  	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 || dev->ifindex == 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 || dev->ifindex == 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 || dev->ifindex == 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 *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) {

  		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 net *net = dev_net(dev);
  	struct sit_net *sitn = net_generic(net, sit_net_id);
  	int err;

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

  	if ((__force u16)t->parms.i_flags & SIT_ISATAP)

  		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);

  	dev_hold(dev);
  
  	ipip6_tunnel_link(sitn, t);
  	return 0;
  
  out:
  	return err;
  }

  static struct ip_tunnel *ipip6_tunnel_locate(struct net *net,

  		struct ip_tunnel_parm *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;

  		strlcpy(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->parms = *parms;

  	if (ipip6_tunnel_create(dev) < 0)

  		goto failed_free;

  	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 ip_tunnel *t,
  				struct ip_tunnel_prl __user *a)

  {

  	struct ip_tunnel_prl kprl, *kp;

  	struct ip_tunnel_prl_entry *prl;
  	unsigned int cmax, c = 0, ca, len;
  	int ret = 0;

  	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 | __GFP_NOWARN) :

  		NULL;

  	rcu_read_lock();

  
  	ca = t->prl_count < cmax ? 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);
  		if (!kp) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	}
  
  	c = 0;

  	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;
  	}
  out:

  	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);

  	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

  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);

  	dev_put(dev);

  }

  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 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;

  	t = ipip6_tunnel_lookup(dev_net(skb->dev),
  				skb->dev,
  				iph->daddr,
  				iph->saddr);

  	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, 0, iph->protocol, 0);

  		err = 0;
  		goto out;
  	}

  	if (type == ICMP_REDIRECT) {

  		ipv4_redirect(skb, dev_net(skb->dev), t->parms.link, 0,

  			      iph->protocol, 0);

  		err = 0;
  		goto out;
  	}

  	err = 0;

  	if (!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
  ",
  				     &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
  ",
  			     &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 err;

  	tunnel = ipip6_tunnel_lookup(dev_net(skb->dev), skb->dev,
  				     iph->saddr, iph->daddr);

  	if (tunnel) {

  		struct pcpu_sw_netstats *tstats;

  		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)) {
  			tunnel->dev->stats.rx_errors++;
  			goto out;

  		}

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

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

  		}

  		tstats = this_cpu_ptr(tunnel->dev->tstats);

  		u64_stats_update_begin(&tstats->syncp);

  		tstats->rx_packets++;
  		tstats->rx_bytes += skb->len;

  		u64_stats_update_end(&tstats->syncp);

  		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;

  	iph = ip_hdr(skb);

  	tunnel = ipip6_tunnel_lookup(dev_net(skb->dev), skb->dev,
  				     iph->saddr, iph->daddr);

  	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;

  		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 = (ntohl(v6dst->s6_addr32[pbw0]) << pbi0) >>

  		    tunnel->ip6rd.relay_prefixlen;
  
  		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
  ");

  			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
  ");

  			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,
  			   RT_TOS(tos), RT_SCOPE_UNIVERSE, IPPROTO_IPV6,
  			   0, dst, tiph->saddr, 0, 0,
  			   sock_net_uid(tunnel->net, NULL));
  	rt = ip_route_output_flow(tunnel->net, &fl4, NULL);

  	if (IS_ERR(rt)) {
  		dev->stats.tx_carrier_errors++;
  		goto tx_error_icmp;

  	}
  	if (rt->rt_type != RTN_UNICAST) {
  		ip_rt_put(rt);

  		dev->stats.tx_carrier_errors++;

  		goto tx_error_icmp;
  	}

  	tdev = rt->dst.dev;

  
  	if (tdev == dev) {
  		ip_rt_put(rt);

  		dev->stats.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 < 68) {

  			dev->stats.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(skb, mtu);

  		if (skb->len > mtu && !skb_is_gso(skb)) {

  			icmpv6_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.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, &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.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.tx_errors++;
  	return NETDEV_TX_OK;

  }
  
  static netdev_tx_t sit_tunnel_xmit(struct sk_buff *skb,
  				   struct net_device *dev)
  {
  	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.tx_errors++;

  	kfree_skb(skb);

  	return NETDEV_TX_OK;
  
  }

  static void ipip6_tunnel_bind_dev(struct net_device *dev)
  {
  	struct net_device *tdev = NULL;
  	struct ip_tunnel *tunnel;

  	const struct iphdr *iph;

  	struct flowi4 fl4;

  
  	tunnel = netdev_priv(dev);
  	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,
  							  RT_TOS(iph->tos),
  							  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) {

  		int t_hlen = tunnel->hlen + sizeof(struct iphdr);

  		dev->hard_header_len = tdev->hard_header_len + sizeof(struct iphdr);

  		dev->mtu = tdev->mtu - t_hlen;

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

  }

  static void ipip6_tunnel_update(struct ip_tunnel *t, struct ip_tunnel_parm *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;
  	memcpy(t->dev->dev_addr, &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;
  }
  #endif

  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(struct net_device *dev, struct ifreq *ifr, int cmd)

  {
  	int err = 0;
  	struct ip_tunnel_parm p;

  	struct ip_tunnel_prl prl;

  	struct ip_tunnel *t = netdev_priv(dev);
  	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

  
  	switch (cmd) {
  	case SIOCGETTUNNEL:

  #ifdef CONFIG_IPV6_SIT_6RD
  	case SIOCGET6RD:
  #endif

  		if (dev == sitn->fb_tunnel_dev) {

  			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
  				err = -EFAULT;
  				break;
  			}

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

  			if (!t)

  				t = netdev_priv(dev);

  		}

  
  		err = -EFAULT;
  		if (cmd == SIOCGETTUNNEL) {
  			memcpy(&p, &t->parms, sizeof(p));
  			if (copy_to_user(ifr->ifr_ifru.ifru_data, &p,
  					 sizeof(p)))
  				goto done;
  #ifdef CONFIG_IPV6_SIT_6RD
  		} else {

  			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(ifr->ifr_ifru.ifru_data, &ip6rd,
  					 sizeof(ip6rd)))
  				goto done;
  #endif
  		}
  		err = 0;

  		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 (!ipip6_valid_ip_proto(p.iph.protocol))

  			goto done;
  		if (p.iph.version != 4 ||

  		    p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)))
  			goto done;
  		if (p.iph.ttl)
  			p.iph.frag_off |= htons(IP_DF);

  		t = ipip6_tunnel_locate(net, &p, cmd == SIOCADDTUNNEL);

  		if (dev != sitn->fb_tunnel_dev && cmd == SIOCCHGTUNNEL) {

  			if (t) {

  				if (t->dev != dev) {
  					err = -EEXIST;
  					break;
  				}
  			} else {
  				if (((dev->flags&IFF_POINTOPOINT) && !p.iph.daddr) ||
  				    (!(dev->flags&IFF_POINTOPOINT) && p.iph.daddr)) {
  					err = -EINVAL;
  					break;
  				}

  				t = netdev_priv(dev);

  			}

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

  		}
  
  		if (t) {
  			err = 0;

  			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 == sitn->fb_tunnel_dev) {

  			err = -EFAULT;
  			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
  				goto done;
  			err = -ENOENT;

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

  			if (!t)

  				goto done;
  			err = -EPERM;

  			if (t == netdev_priv(sitn->fb_tunnel_dev))

  				goto done;
  			dev = t->dev;
  		}

  		unregister_netdevice(dev);
  		err = 0;

  		break;

  	case SIOCGETPRL:

  		err = -EINVAL;
  		if (dev == sitn->fb_tunnel_dev)
  			goto done;

  		err = ipip6_tunnel_get_prl(t, ifr->ifr_ifru.ifru_data);
  		break;

  	case SIOCADDPRL:
  	case SIOCDELPRL:
  	case SIOCCHGPRL:
  		err = -EPERM;

  		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))

  			goto done;
  		err = -EINVAL;

  		if (dev == sitn->fb_tunnel_dev)

  			goto done;
  		err = -EFAULT;
  		if (copy_from_user(&prl, ifr->ifr_ifru.ifru_data, sizeof(prl)))
  			goto done;

  		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);

  		break;

  #ifdef CONFIG_IPV6_SIT_6RD
  	case SIOCADD6RD:
  	case SIOCCHG6RD:
  	case SIOCDEL6RD:
  		err = -EPERM;

  		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))

  			goto done;
  
  		err = -EFAULT;
  		if (copy_from_user(&ip6rd, ifr->ifr_ifru.ifru_data,
  				   sizeof(ip6rd)))
  			goto done;

  		if (cmd != SIOCDEL6RD) {

  			err = ipip6_tunnel_update_6rd(t, &ip6rd);
  			if (err < 0)

  				goto done;

  		} else

  			ipip6_tunnel_clone_6rd(dev, sitn);

  
  		err = 0;
  		break;
  #endif

  	default:
  		err = -EINVAL;
  	}
  
  done:
  	return err;
  }

  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_do_ioctl	= ipip6_tunnel_ioctl,

  	.ndo_get_stats64 = ip_tunnel_get_stats64,

  	.ndo_get_iflink = ip_tunnel_get_iflink,

  };

  static void ipip6_dev_free(struct net_device *dev)
  {

  	struct ip_tunnel *tunnel = netdev_priv(dev);

  	dst_cache_destroy(&tunnel->dst_cache);

  	free_percpu(dev->tstats);

  }

  #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->needs_free_netdev	= true;
  	dev->priv_destructor	= ipip6_dev_free;

  
  	dev->type		= ARPHRD_SIT;

  	dev->hard_header_len	= LL_MAX_HEADER + t_hlen;
  	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->features		|= NETIF_F_LLTX;

  	dev->features		|= SIT_FEATURES;
  	dev->hw_features	|= SIT_FEATURES;

  }

  static int ipip6_tunnel_init(struct net_device *dev)

  {

  	struct ip_tunnel *tunnel = netdev_priv(dev);

  	int err;

  
  	tunnel->dev = dev;

  	tunnel->net = dev_net(dev);

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

  	ipip6_tunnel_bind_dev(dev);

  	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);

  	if (!dev->tstats)
  		return -ENOMEM;

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

  		free_percpu(dev->tstats);

  		dev->tstats = NULL;

  		return err;

  	}

  	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;
  
  	dev_hold(dev);

  	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 *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;
  
  	if (data[IFLA_IPTUN_LINK])
  		parms->link = nla_get_u32(data[IFLA_IPTUN_LINK]);
  
  	if (data[IFLA_IPTUN_LOCAL])

  		parms->iph.saddr = nla_get_be32(data[IFLA_IPTUN_LOCAL]);

  
  	if (data[IFLA_IPTUN_REMOTE])

  		parms->iph.daddr = nla_get_be32(data[IFLA_IPTUN_REMOTE]);

  
  	if (data[IFLA_IPTUN_TTL]) {
  		parms->iph.ttl = nla_get_u8(data[IFLA_IPTUN_TTL]);
  		if (parms->iph.ttl)
  			parms->iph.frag_off = htons(IP_DF);
  	}
  
  	if (data[IFLA_IPTUN_TOS])
  		parms->iph.tos = nla_get_u8(data[IFLA_IPTUN_TOS]);
  
  	if (!data[IFLA_IPTUN_PMTUDISC] || nla_get_u8(data[IFLA_IPTUN_PMTUDISC]))
  		parms->iph.frag_off = htons(IP_DF);
  
  	if (data[IFLA_IPTUN_FLAGS])

  		parms->i_flags = nla_get_be16(data[IFLA_IPTUN_FLAGS]);

  
  	if (data[IFLA_IPTUN_PROTO])
  		parms->iph.protocol = nla_get_u8(data[IFLA_IPTUN_PROTO]);

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

  }

  /* This function returns true when ENCAP attributes are present in the nl msg */
  static bool ipip6_netlink_encap_parms(struct nlattr *data[],
  				      struct ip_tunnel_encap *ipencap)
  {
  	bool ret = false;
  
  	memset(ipencap, 0, sizeof(*ipencap));
  
  	if (!data)
  		return ret;
  
  	if (data[IFLA_IPTUN_ENCAP_TYPE]) {
  		ret = true;
  		ipencap->type = nla_get_u16(data[IFLA_IPTUN_ENCAP_TYPE]);
  	}
  
  	if (data[IFLA_IPTUN_ENCAP_FLAGS]) {
  		ret = true;
  		ipencap->flags = nla_get_u16(data[IFLA_IPTUN_ENCAP_FLAGS]);
  	}
  
  	if (data[IFLA_IPTUN_ENCAP_SPORT]) {
  		ret = true;

  		ipencap->sport = nla_get_be16(data[IFLA_IPTUN_ENCAP_SPORT]);

  	}
  
  	if (data[IFLA_IPTUN_ENCAP_DPORT]) {
  		ret = true;

  		ipencap->dport = nla_get_be16(data[IFLA_IPTUN_ENCAP_DPORT]);

  	}
  
  	return ret;
  }

  #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 *src_net, struct net_device *dev,

  			 struct nlattr *tb[], struct nlattr *data[],
  			 struct netlink_ext_ack *extack)

  {
  	struct net *net = dev_net(dev);
  	struct ip_tunnel *nt;