text: /*
   *	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 <asm/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 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 int sit_net_id __read_mostly;
  struct sit_net {
  	struct ip_tunnel __rcu *tunnels_r_l[HASH_SIZE];
  	struct ip_tunnel __rcu *tunnels_r[HASH_SIZE];
  	struct ip_tunnel __rcu *tunnels_l[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 (t->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])
  		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:
  	ipip6_dev_free(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) :
  		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);
  }
  
  /* Generate icmpv6 with type/code ICMPV6_DEST_UNREACH/ICMPV6_ADDR_UNREACH
   * if sufficient data bytes are available
   */
  static int ipip6_err_gen_icmpv6_unreach(struct sk_buff *skb)
  {
  	int ihl = ((const struct iphdr *)skb->data)->ihl*4;
  	struct rt6_info *rt;
  	struct sk_buff *skb2;
  
  	if (!pskb_may_pull(skb, ihl + sizeof(struct ipv6hdr) + 8))
  		return 1;
  
  	skb2 = skb_clone(skb, GFP_ATOMIC);
  
  	if (!skb2)
  		return 1;
  
  	skb_dst_drop(skb2);
  	skb_pull(skb2, ihl);
  	skb_reset_network_header(skb2);
  
  	rt = rt6_lookup(dev_net(skb->dev), &ipv6_hdr(skb2)->saddr, NULL, 0, 0);
  
  	if (rt && rt->dst.dev)
  		skb2->dev = rt->dst.dev;
  
  	icmpv6_send(skb2, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH, 0);
  
  	if (rt)
  		ip6_rt_put(rt);
  
  	kfree_skb(skb2);
  
  	return 0;
  }
  
  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;
  	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;
  		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;
  	}
  
  	if (t->parms.iph.daddr == 0)
  		goto out;
  
  	err = 0;
  	if (!ipip6_err_gen_icmpv6_unreach(skb))
  		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 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\n",
  						     &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 tpi = {
  	/* no tunnel info required for ipip. */
  	.proto = htons(ETH_P_IP),
  };
  
  static int ipip_rcv(struct sk_buff *skb)
  {
  	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) {
  		if (tunnel->parms.iph.protocol != IPPROTO_IPIP &&
  		    tunnel->parms.iph.protocol != 0)
  			goto drop;
  
  		if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
  			goto drop;
  		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;
  }
  
  /*
   * 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 (skb->protocol != htons(ETH_P_IPV6))
  		goto tx_error;
  
  	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;
  	}
  
  	rt = ip_route_output_ports(tunnel->net, &fl4, NULL,
  				   dst, tiph->saddr,
  				   0, 0,
  				   IPPROTO_IPV6, RT_TOS(tos),
  				   tunnel->parms.link);
  	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(skb))
  			skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, 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 ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
  {
  	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_IPIP);
  
  	ip_tunnel_xmit(skb, dev, tiph, IPPROTO_IPIP);
  	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):
  		ipip_tunnel_xmit(skb, dev);
  		break;
  	case htons(ETH_P_IPV6):
  		ipip6_tunnel_xmit(skb, dev);
  		break;
  	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)
  {
  	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;
  	if (t->parms.link != p->link) {
  		t->parms.link = p->link;
  		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 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 (p.iph.protocol != IPPROTO_IPV6 &&
  		    p.iph.protocol != IPPROTO_IPIP &&
  		    p.iph.protocol != 0)
  			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);
  		}
  
  		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 int ipip6_tunnel_change_mtu(struct net_device *dev, int new_mtu)
  {
  	struct ip_tunnel *tunnel = netdev_priv(dev);
  	int t_hlen = tunnel->hlen + sizeof(struct iphdr);
  
  	if (new_mtu < IPV6_MIN_MTU || new_mtu > 0xFFF8 - t_hlen)
  		return -EINVAL;
  	dev->mtu = new_mtu;
  	return 0;
  }
  
  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_change_mtu	= ipip6_tunnel_change_mtu,
  	.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);
  	free_netdev(dev);
  }
  
  #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->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->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);
  		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[])
  {
  	u8 proto;
  
  	if (!data || !data[IFLA_IPTUN_PROTO])
  		return 0;
  
  	proto = nla_get_u8(data[IFLA_IPTUN_PROTO]);
  	if (proto != IPPROTO_IPV6 &&
  	    proto != IPPROTO_IPIP &&
  	    proto != 0)
  		return -EINVAL;
  
  	return 0;
  }
  
  static void ipip6_netlink_parms(struct nlattr *data[],
  				struct ip_tunnel_parm *parms)
  {
  	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]);
  
  }
  
  /* 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 net *net = dev_net(dev);
  	struct ip_tunnel *nt;
  	struct ip_tunnel_encap ipencap;
  #ifdef CONFIG_IPV6_SIT_6RD
  	struct ip_tunnel_6rd ip6rd;
  #endif
  	int err;
  
  	nt = netdev_priv(dev);
  
  	if (ipip6_netlink_encap_parms(data, &ipencap)) {
  		err = ip_tunnel_encap_setup(nt, &ipencap);
  		if (err < 0)
  			return err;
  	}
  
  	ipip6_netlink_parms(data, &nt->parms);
  
  	if (ipip6_tunnel_locate(net, &nt->parms, 0))
  		return -EEXIST;
  
  	err = ipip6_tunnel_create(dev);
  	if (err < 0)
  		return err;
  
  #ifdef CONFIG_IPV6_SIT_6RD
  	if (ipip6_netlink_6rd_parms(data, &ip6rd))
  		err = ipip6_tunnel_update_6rd(nt, &ip6rd);
  #endif
  
  	return err;
  }
  
  static int ipip6_changelink(struct net_device *dev, struct nlattr *tb[],
  			  struct nlattr *data[])
  {
  	struct ip_tunnel *t = netdev_priv(dev);
  	struct ip_tunnel_parm p;
  	struct ip_tunnel_encap ipencap;
  	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
  	int err;
  
  	if (dev == sitn->fb_tunnel_dev)
  		return -EINVAL;
  
  	if (ipip6_netlink_encap_parms(data, &ipencap)) {
  		err = ip_tunnel_encap_setup(t, &ipencap);
  		if (err < 0)
  			return err;
  	}
  
  	ipip6_netlink_parms(data, &p);
  
  	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);
  
  #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) +
  		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 *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, parm->i_flags))
  		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 },
  };
  
  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,
  };
  
  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 = 1; prio < 4; prio++) {
  		int h;
  		for (h = 0; h < HASH_SIZE; 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;
  
  	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->features |= NETIF_F_NETNS_LOCAL;
  
  	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);
  
  	t = netdev_priv(sitn->fb_tunnel_dev);
  
  	strcpy(t->parms.name, sitn->fb_tunnel_dev->name);
  	return 0;
  
  err_reg_dev:
  	ipip6_dev_free(sitn->fb_tunnel_dev);
  err_alloc_dev:
  	return err;
  }
  
  static void __net_exit sit_exit_net(struct net *net)
  {
  	LIST_HEAD(list);
  
  	rtnl_lock();
  	sit_destroy_tunnels(net, &list);
  	unregister_netdevice_many(&list);
  	rtnl_unlock();
  }
  
  static struct pernet_operations sit_net_ops = {
  	.init = sit_init_net,
  	.exit = sit_exit_net,
  	.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);
  
  	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 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;
  	}
  	err = rtnl_link_register(&sit_link_ops);
  	if (err < 0)
  		goto rtnl_link_failed;
  
  out:
  	return err;
  
  rtnl_link_failed:
  	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_LICENSE("GPL");
  MODULE_ALIAS_RTNL_LINK("sit");
  MODULE_ALIAS_NETDEV("sit0");
  