ip6_tunnel.c

/*
 *	IPv6 tunneling device
 *	Linux INET6 implementation
 *
 *	Authors:
 *	Ville Nuorvala		<vnuorval@tcs.hut.fi>
 *	Yasuyuki Kozakai	<kozakai@linux-ipv6.org>
 *
 *      Based on:
 *      linux/net/ipv6/sit.c and linux/net/ipv4/ipip.c
 *
 *      RFC 2473
 *
 *	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.
 *
 */

#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/sockios.h>
#include <linux/icmp.h>
#include <linux/if.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/if_tunnel.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/icmpv6.h>
#include <linux/init.h>
#include <linux/route.h>
#include <linux/rtnetlink.h>
#include <linux/netfilter_ipv6.h>
#include <linux/slab.h>
#include <linux/hash.h>
#include <linux/etherdevice.h>

#include <asm/uaccess.h>
#include <linux/atomic.h>

#include <net/icmp.h>
#include <net/ip.h>
#include <net/ip_tunnels.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/ip6_tunnel.h>
#include <net/xfrm.h>
#include <net/dsfield.h>
#include <net/inet_ecn.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

MODULE_AUTHOR("Ville Nuorvala");
MODULE_DESCRIPTION("IPv6 tunneling device");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NETDEV("ip6tnl0");

#ifdef IP6_TNL_DEBUG
#define IP6_TNL_TRACE(x...) pr_debug("%s:" x "\n", __func__)
#else
#define IP6_TNL_TRACE(x...) do {;} while(0)
#endif

#define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
#define IPV6_TCLASS_SHIFT 20

#define HASH_SIZE_SHIFT  5
#define HASH_SIZE (1 << HASH_SIZE_SHIFT)

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 u32 HASH(const struct in6_addr *addr1, const struct in6_addr *addr2)
{
	u32 hash = ipv6_addr_hash(addr1) ^ ipv6_addr_hash(addr2);

	return hash_32(hash, HASH_SIZE_SHIFT);
}

static int ip6_tnl_dev_init(struct net_device *dev);
static void ip6_tnl_dev_setup(struct net_device *dev);
static struct rtnl_link_ops ip6_link_ops __read_mostly;

static int ip6_tnl_net_id __read_mostly;
struct ip6_tnl_net {
	/* the IPv6 tunnel fallback device */
	struct net_device *fb_tnl_dev;
	/* lists for storing tunnels in use */
	struct ip6_tnl __rcu *tnls_r_l[HASH_SIZE];
	struct ip6_tnl __rcu *tnls_wc[1];
	struct ip6_tnl __rcu **tnls[2];
};

static struct net_device_stats *ip6_get_stats(struct net_device *dev)
{
	struct pcpu_tstats sum = { 0 };
	int i;

	for_each_possible_cpu(i) {
		const struct pcpu_tstats *tstats = per_cpu_ptr(dev->tstats, i);

		sum.rx_packets += tstats->rx_packets;
		sum.rx_bytes   += tstats->rx_bytes;
		sum.tx_packets += tstats->tx_packets;
		sum.tx_bytes   += tstats->tx_bytes;
	}
	dev->stats.rx_packets = sum.rx_packets;
	dev->stats.rx_bytes   = sum.rx_bytes;
	dev->stats.tx_packets = sum.tx_packets;
	dev->stats.tx_bytes   = sum.tx_bytes;
	return &dev->stats;
}

/*
 * Locking : hash tables are protected by RCU and RTNL
 */

struct dst_entry *ip6_tnl_dst_check(struct ip6_tnl *t)
{
	struct dst_entry *dst = t->dst_cache;

	if (dst && dst->obsolete &&
	    dst->ops->check(dst, t->dst_cookie) == NULL) {
		t->dst_cache = NULL;
		dst_release(dst);
		return NULL;
	}

	return dst;
}
EXPORT_SYMBOL_GPL(ip6_tnl_dst_check);

void ip6_tnl_dst_reset(struct ip6_tnl *t)
{
	dst_release(t->dst_cache);
	t->dst_cache = NULL;
}
EXPORT_SYMBOL_GPL(ip6_tnl_dst_reset);

void ip6_tnl_dst_store(struct ip6_tnl *t, struct dst_entry *dst)
{
	struct rt6_info *rt = (struct rt6_info *) dst;
	t->dst_cookie = rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0;
	dst_release(t->dst_cache);
	t->dst_cache = dst;
}
EXPORT_SYMBOL_GPL(ip6_tnl_dst_store);

/**
 * ip6_tnl_lookup - fetch tunnel matching the end-point addresses
 *   @remote: the address of the tunnel exit-point
 *   @local: the address of the tunnel entry-point
 *
 * Return:
 *   tunnel matching given end-points if found,
 *   else fallback tunnel if its device is up,
 *   else %NULL
 **/

#define for_each_ip6_tunnel_rcu(start) \
	for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))

static struct ip6_tnl *
ip6_tnl_lookup(struct net *net, const struct in6_addr *remote, const struct in6_addr *local)
{
	unsigned int hash = HASH(remote, local);
	struct ip6_tnl *t;
	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

	for_each_ip6_tunnel_rcu(ip6n->tnls_r_l[hash]) {
		if (ipv6_addr_equal(local, &t->parms.laddr) &&
		    ipv6_addr_equal(remote, &t->parms.raddr) &&
		    (t->dev->flags & IFF_UP))
			return t;
	}
	t = rcu_dereference(ip6n->tnls_wc[0]);
	if (t && (t->dev->flags & IFF_UP))
		return t;

	return NULL;
}

/**
 * ip6_tnl_bucket - get head of list matching given tunnel parameters
 *   @p: parameters containing tunnel end-points
 *
 * Description:
 *   ip6_tnl_bucket() returns the head of the list matching the
 *   &struct in6_addr entries laddr and raddr in @p.
 *
 * Return: head of IPv6 tunnel list
 **/

static struct ip6_tnl __rcu **
ip6_tnl_bucket(struct ip6_tnl_net *ip6n, const struct __ip6_tnl_parm *p)
{
	const struct in6_addr *remote = &p->raddr;
	const struct in6_addr *local = &p->laddr;
	unsigned int h = 0;
	int prio = 0;

	if (!ipv6_addr_any(remote) || !ipv6_addr_any(local)) {
		prio = 1;
		h = HASH(remote, local);
	}
	return &ip6n->tnls[prio][h];
}

/**
 * ip6_tnl_link - add tunnel to hash table
 *   @t: tunnel to be added
 **/

static void
ip6_tnl_link(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
{
	struct ip6_tnl __rcu **tp = ip6_tnl_bucket(ip6n, &t->parms);

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

/**
 * ip6_tnl_unlink - remove tunnel from hash table
 *   @t: tunnel to be removed
 **/

static void
ip6_tnl_unlink(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
{
	struct ip6_tnl __rcu **tp;
	struct ip6_tnl *iter;

	for (tp = ip6_tnl_bucket(ip6n, &t->parms);
	     (iter = rtnl_dereference(*tp)) != NULL;
	     tp = &iter->next) {
		if (t == iter) {
			rcu_assign_pointer(*tp, t->next);
			break;
		}
	}
}

static void ip6_dev_free(struct net_device *dev)
{
	free_percpu(dev->tstats);
	free_netdev(dev);
}

static int ip6_tnl_create2(struct net_device *dev)
{
	struct ip6_tnl *t = netdev_priv(dev);
	struct net *net = dev_net(dev);
	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
	int err;

	t = netdev_priv(dev);
	err = ip6_tnl_dev_init(dev);
	if (err < 0)
		goto out;

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

	strcpy(t->parms.name, dev->name);
	dev->rtnl_link_ops = &ip6_link_ops;

	dev_hold(dev);
	ip6_tnl_link(ip6n, t);
	return 0;

out:
	return err;
}

/**
 * ip6_tnl_create - create a new tunnel
 *   @p: tunnel parameters
 *   @pt: pointer to new tunnel
 *
 * Description:
 *   Create tunnel matching given parameters.
 *
 * Return:
 *   created tunnel or NULL
 **/

static struct ip6_tnl *ip6_tnl_create(struct net *net, struct __ip6_tnl_parm *p)
{
	struct net_device *dev;
	struct ip6_tnl *t;
	char name[IFNAMSIZ];
	int err;

	if (p->name[0])
		strlcpy(name, p->name, IFNAMSIZ);
	else
		sprintf(name, "ip6tnl%%d");

	dev = alloc_netdev(sizeof (*t), name, ip6_tnl_dev_setup);
	if (dev == NULL)
		goto failed;

	dev_net_set(dev, net);

	t = netdev_priv(dev);
	t->parms = *p;
	t->net = dev_net(dev);
	err = ip6_tnl_create2(dev);
	if (err < 0)
		goto failed_free;

	return t;

failed_free:
	ip6_dev_free(dev);
failed:
	return NULL;
}

/**
 * ip6_tnl_locate - find or create tunnel matching given parameters
 *   @p: tunnel parameters
 *   @create: != 0 if allowed to create new tunnel if no match found
 *
 * Description:
 *   ip6_tnl_locate() first tries to locate an existing tunnel
 *   based on @parms. If this is unsuccessful, but @create is set a new
 *   tunnel device is created and registered for use.
 *
 * Return:
 *   matching tunnel or NULL
 **/

static struct ip6_tnl *ip6_tnl_locate(struct net *net,
		struct __ip6_tnl_parm *p, int create)
{
	const struct in6_addr *remote = &p->raddr;
	const struct in6_addr *local = &p->laddr;
	struct ip6_tnl __rcu **tp;
	struct ip6_tnl *t;
	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

	for (tp = ip6_tnl_bucket(ip6n, p);
	     (t = rtnl_dereference(*tp)) != NULL;
	     tp = &t->next) {
		if (ipv6_addr_equal(local, &t->parms.laddr) &&
		    ipv6_addr_equal(remote, &t->parms.raddr))
			return t;
	}
	if (!create)
		return NULL;
	return ip6_tnl_create(net, p);
}

/**
 * ip6_tnl_dev_uninit - tunnel device uninitializer
 *   @dev: the device to be destroyed
 *
 * Description:
 *   ip6_tnl_dev_uninit() removes tunnel from its list
 **/

static void
ip6_tnl_dev_uninit(struct net_device *dev)
{
	struct ip6_tnl *t = netdev_priv(dev);
	struct net *net = t->net;
	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

	if (dev == ip6n->fb_tnl_dev)
		RCU_INIT_POINTER(ip6n->tnls_wc[0], NULL);
	else
		ip6_tnl_unlink(ip6n, t);
	ip6_tnl_dst_reset(t);
	dev_put(dev);
}

/**
 * parse_tvl_tnl_enc_lim - handle encapsulation limit option
 *   @skb: received socket buffer
 *
 * Return:
 *   0 if none was found,
 *   else index to encapsulation limit
 **/

__u16 ip6_tnl_parse_tlv_enc_lim(struct sk_buff *skb, __u8 *raw)
{
	const struct ipv6hdr *ipv6h = (const struct ipv6hdr *) raw;
	__u8 nexthdr = ipv6h->nexthdr;
	__u16 off = sizeof (*ipv6h);

	while (ipv6_ext_hdr(nexthdr) && nexthdr != NEXTHDR_NONE) {
		__u16 optlen = 0;
		struct ipv6_opt_hdr *hdr;
		if (raw + off + sizeof (*hdr) > skb->data &&
		    !pskb_may_pull(skb, raw - skb->data + off + sizeof (*hdr)))
			break;

		hdr = (struct ipv6_opt_hdr *) (raw + off);
		if (nexthdr == NEXTHDR_FRAGMENT) {
			struct frag_hdr *frag_hdr = (struct frag_hdr *) hdr;
			if (frag_hdr->frag_off)
				break;
			optlen = 8;
		} else if (nexthdr == NEXTHDR_AUTH) {
			optlen = (hdr->hdrlen + 2) << 2;
		} else {
			optlen = ipv6_optlen(hdr);
		}
		if (nexthdr == NEXTHDR_DEST) {
			__u16 i = off + 2;
			while (1) {
				struct ipv6_tlv_tnl_enc_lim *tel;

				/* No more room for encapsulation limit */
				if (i + sizeof (*tel) > off + optlen)
					break;

				tel = (struct ipv6_tlv_tnl_enc_lim *) &raw[i];
				/* return index of option if found and valid */
				if (tel->type == IPV6_TLV_TNL_ENCAP_LIMIT &&
				    tel->length == 1)
					return i;
				/* else jump to next option */
				if (tel->type)
					i += tel->length + 2;
				else
					i++;
			}
		}
		nexthdr = hdr->nexthdr;
		off += optlen;
	}
	return 0;
}
EXPORT_SYMBOL(ip6_tnl_parse_tlv_enc_lim);

/**
 * ip6_tnl_err - tunnel error handler
 *
 * Description:
 *   ip6_tnl_err() should handle errors in the tunnel according
 *   to the specifications in RFC 2473.
 **/

static int
ip6_tnl_err(struct sk_buff *skb, __u8 ipproto, struct inet6_skb_parm *opt,
	    u8 *type, u8 *code, int *msg, __u32 *info, int offset)
{
	const struct ipv6hdr *ipv6h = (const struct ipv6hdr *) skb->data;
	struct ip6_tnl *t;
	int rel_msg = 0;
	u8 rel_type = ICMPV6_DEST_UNREACH;
	u8 rel_code = ICMPV6_ADDR_UNREACH;
	__u32 rel_info = 0;
	__u16 len;
	int err = -ENOENT;

	/* If the packet doesn't contain the original IPv6 header we are
	   in trouble since we might need the source address for further
	   processing of the error. */

	rcu_read_lock();
	if ((t = ip6_tnl_lookup(dev_net(skb->dev), &ipv6h->daddr,
					&ipv6h->saddr)) == NULL)
		goto out;

	if (t->parms.proto != ipproto && t->parms.proto != 0)
		goto out;

	err = 0;

	switch (*type) {
		__u32 teli;
		struct ipv6_tlv_tnl_enc_lim *tel;
		__u32 mtu;
	case ICMPV6_DEST_UNREACH:
		net_warn_ratelimited("%s: Path to destination invalid or inactive!\n",
				     t->parms.name);
		rel_msg = 1;
		break;
	case ICMPV6_TIME_EXCEED:
		if ((*code) == ICMPV6_EXC_HOPLIMIT) {
			net_warn_ratelimited("%s: Too small hop limit or routing loop in tunnel!\n",
					     t->parms.name);
			rel_msg = 1;
		}
		break;
	case ICMPV6_PARAMPROB:
		teli = 0;
		if ((*code) == ICMPV6_HDR_FIELD)
			teli = ip6_tnl_parse_tlv_enc_lim(skb, skb->data);

		if (teli && teli == *info - 2) {
			tel = (struct ipv6_tlv_tnl_enc_lim *) &skb->data[teli];
			if (tel->encap_limit == 0) {
				net_warn_ratelimited("%s: Too small encapsulation limit or routing loop in tunnel!\n",
						     t->parms.name);
				rel_msg = 1;
			}
		} else {
			net_warn_ratelimited("%s: Recipient unable to parse tunneled packet!\n",
					     t->parms.name);
		}
		break;
	case ICMPV6_PKT_TOOBIG:
		mtu = *info - offset;
		if (mtu < IPV6_MIN_MTU)
			mtu = IPV6_MIN_MTU;
		t->dev->mtu = mtu;

		if ((len = sizeof (*ipv6h) + ntohs(ipv6h->payload_len)) > mtu) {
			rel_type = ICMPV6_PKT_TOOBIG;
			rel_code = 0;
			rel_info = mtu;
			rel_msg = 1;
		}
		break;
	}

	*type = rel_type;
	*code = rel_code;
	*info = rel_info;
	*msg = rel_msg;

out:
	rcu_read_unlock();
	return err;
}

static int
ip4ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
	   u8 type, u8 code, int offset, __be32 info)
{
	int rel_msg = 0;
	u8 rel_type = type;
	u8 rel_code = code;
	__u32 rel_info = ntohl(info);
	int err;
	struct sk_buff *skb2;
	const struct iphdr *eiph;
	struct rtable *rt;
	struct flowi4 fl4;

	err = ip6_tnl_err(skb, IPPROTO_IPIP, opt, &rel_type, &rel_code,
			  &rel_msg, &rel_info, offset);
	if (err < 0)
		return err;

	if (rel_msg == 0)
		return 0;

	switch (rel_type) {
	case ICMPV6_DEST_UNREACH:
		if (rel_code != ICMPV6_ADDR_UNREACH)
			return 0;
		rel_type = ICMP_DEST_UNREACH;
		rel_code = ICMP_HOST_UNREACH;
		break;
	case ICMPV6_PKT_TOOBIG:
		if (rel_code != 0)
			return 0;
		rel_type = ICMP_DEST_UNREACH;
		rel_code = ICMP_FRAG_NEEDED;
		break;
	case NDISC_REDIRECT:
		rel_type = ICMP_REDIRECT;
		rel_code = ICMP_REDIR_HOST;
	default:
		return 0;
	}

	if (!pskb_may_pull(skb, offset + sizeof(struct iphdr)))
		return 0;

	skb2 = skb_clone(skb, GFP_ATOMIC);
	if (!skb2)
		return 0;

	skb_dst_drop(skb2);

	skb_pull(skb2, offset);
	skb_reset_network_header(skb2);
	eiph = ip_hdr(skb2);

	/* Try to guess incoming interface */
	rt = ip_route_output_ports(dev_net(skb->dev), &fl4, NULL,
				   eiph->saddr, 0,
				   0, 0,
				   IPPROTO_IPIP, RT_TOS(eiph->tos), 0);
	if (IS_ERR(rt))
		goto out;

	skb2->dev = rt->dst.dev;

	/* route "incoming" packet */
	if (rt->rt_flags & RTCF_LOCAL) {
		ip_rt_put(rt);
		rt = NULL;
		rt = ip_route_output_ports(dev_net(skb->dev), &fl4, NULL,
					   eiph->daddr, eiph->saddr,
					   0, 0,
					   IPPROTO_IPIP,
					   RT_TOS(eiph->tos), 0);
		if (IS_ERR(rt) ||
		    rt->dst.dev->type != ARPHRD_TUNNEL) {
			if (!IS_ERR(rt))
				ip_rt_put(rt);
			goto out;
		}
		skb_dst_set(skb2, &rt->dst);
	} else {
		ip_rt_put(rt);
		if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos,
				   skb2->dev) ||
		    skb_dst(skb2)->dev->type != ARPHRD_TUNNEL)
			goto out;
	}

	/* change mtu on this route */
	if (rel_type == ICMP_DEST_UNREACH && rel_code == ICMP_FRAG_NEEDED) {
		if (rel_info > dst_mtu(skb_dst(skb2)))
			goto out;

		skb_dst(skb2)->ops->update_pmtu(skb_dst(skb2), NULL, skb2, rel_info);
	}
	if (rel_type == ICMP_REDIRECT)
		skb_dst(skb2)->ops->redirect(skb_dst(skb2), NULL, skb2);

	icmp_send(skb2, rel_type, rel_code, htonl(rel_info));

out:
	kfree_skb(skb2);
	return 0;
}

static int
ip6ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
	   u8 type, u8 code, int offset, __be32 info)
{
	int rel_msg = 0;
	u8 rel_type = type;
	u8 rel_code = code;
	__u32 rel_info = ntohl(info);
	int err;

	err = ip6_tnl_err(skb, IPPROTO_IPV6, opt, &rel_type, &rel_code,
			  &rel_msg, &rel_info, offset);
	if (err < 0)
		return err;

	if (rel_msg && pskb_may_pull(skb, offset + sizeof(struct ipv6hdr))) {
		struct rt6_info *rt;
		struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);

		if (!skb2)
			return 0;

		skb_dst_drop(skb2);
		skb_pull(skb2, offset);
		skb_reset_network_header(skb2);

		/* Try to guess incoming interface */
		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, rel_type, rel_code, rel_info);

		ip6_rt_put(rt);

		kfree_skb(skb2);
	}

	return 0;
}

static int ip4ip6_dscp_ecn_decapsulate(const struct ip6_tnl *t,
				       const struct ipv6hdr *ipv6h,
				       struct sk_buff *skb)
{
	__u8 dsfield = ipv6_get_dsfield(ipv6h) & ~INET_ECN_MASK;

	if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)
		ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, dsfield);

	return IP6_ECN_decapsulate(ipv6h, skb);
}

static int ip6ip6_dscp_ecn_decapsulate(const struct ip6_tnl *t,
				       const struct ipv6hdr *ipv6h,
				       struct sk_buff *skb)
{
	if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)
		ipv6_copy_dscp(ipv6_get_dsfield(ipv6h), ipv6_hdr(skb));

	return IP6_ECN_decapsulate(ipv6h, skb);
}

__u32 ip6_tnl_get_cap(struct ip6_tnl *t,
			     const struct in6_addr *laddr,
			     const struct in6_addr *raddr)
{
	struct __ip6_tnl_parm *p = &t->parms;
	int ltype = ipv6_addr_type(laddr);
	int rtype = ipv6_addr_type(raddr);
	__u32 flags = 0;

	if (ltype == IPV6_ADDR_ANY || rtype == IPV6_ADDR_ANY) {
		flags = IP6_TNL_F_CAP_PER_PACKET;
	} else if (ltype & (IPV6_ADDR_UNICAST|IPV6_ADDR_MULTICAST) &&
		   rtype & (IPV6_ADDR_UNICAST|IPV6_ADDR_MULTICAST) &&
		   !((ltype|rtype) & IPV6_ADDR_LOOPBACK) &&
		   (!((ltype|rtype) & IPV6_ADDR_LINKLOCAL) || p->link)) {
		if (ltype&IPV6_ADDR_UNICAST)
			flags |= IP6_TNL_F_CAP_XMIT;
		if (rtype&IPV6_ADDR_UNICAST)
			flags |= IP6_TNL_F_CAP_RCV;
	}
	return flags;
}
EXPORT_SYMBOL(ip6_tnl_get_cap);

/* called with rcu_read_lock() */
int ip6_tnl_rcv_ctl(struct ip6_tnl *t,
				  const struct in6_addr *laddr,
				  const struct in6_addr *raddr)
{
	struct __ip6_tnl_parm *p = &t->parms;
	int ret = 0;
	struct net *net = t->net;

	if ((p->flags & IP6_TNL_F_CAP_RCV) ||
	    ((p->flags & IP6_TNL_F_CAP_PER_PACKET) &&
	     (ip6_tnl_get_cap(t, laddr, raddr) & IP6_TNL_F_CAP_RCV))) {
		struct net_device *ldev = NULL;

		if (p->link)
			ldev = dev_get_by_index_rcu(net, p->link);

		if ((ipv6_addr_is_multicast(laddr) ||
		     likely(ipv6_chk_addr(net, laddr, ldev, 0))) &&
		    likely(!ipv6_chk_addr(net, raddr, NULL, 0)))
			ret = 1;
	}
	return ret;
}
EXPORT_SYMBOL_GPL(ip6_tnl_rcv_ctl);

/**
 * ip6_tnl_rcv - decapsulate IPv6 packet and retransmit it locally
 *   @skb: received socket buffer
 *   @protocol: ethernet protocol ID
 *   @dscp_ecn_decapsulate: the function to decapsulate DSCP code and ECN
 *
 * Return: 0
 **/

static int ip6_tnl_rcv(struct sk_buff *skb, __u16 protocol,
		       __u8 ipproto,
		       int (*dscp_ecn_decapsulate)(const struct ip6_tnl *t,
						   const struct ipv6hdr *ipv6h,
						   struct sk_buff *skb))
{
	struct ip6_tnl *t;
	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
	int err;

	rcu_read_lock();

	if ((t = ip6_tnl_lookup(dev_net(skb->dev), &ipv6h->saddr,
					&ipv6h->daddr)) != NULL) {
		struct pcpu_tstats *tstats;

		if (t->parms.proto != ipproto && t->parms.proto != 0) {
			rcu_read_unlock();
			goto discard;
		}

		if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
			rcu_read_unlock();
			goto discard;
		}

		if (!ip6_tnl_rcv_ctl(t, &ipv6h->daddr, &ipv6h->saddr)) {
			t->dev->stats.rx_dropped++;
			rcu_read_unlock();
			goto discard;
		}
		skb->mac_header = skb->network_header;
		skb_reset_network_header(skb);
		skb->protocol = htons(protocol);
		memset(skb->cb, 0, sizeof(struct inet6_skb_parm));

		__skb_tunnel_rx(skb, t->dev, t->net);

		err = dscp_ecn_decapsulate(t, ipv6h, skb);
		if (unlikely(err)) {
			if (log_ecn_error)
				net_info_ratelimited("non-ECT from %pI6 with dsfield=%#x\n",
						     &ipv6h->saddr,
						     ipv6_get_dsfield(ipv6h));
			if (err > 1) {
				++t->dev->stats.rx_frame_errors;
				++t->dev->stats.rx_errors;
				rcu_read_unlock();
				goto discard;
			}
		}

		tstats = this_cpu_ptr(t->dev->tstats);
		tstats->rx_packets++;
		tstats->rx_bytes += skb->len;

		netif_rx(skb);

		rcu_read_unlock();
		return 0;
	}
	rcu_read_unlock();
	return 1;

discard:
	kfree_skb(skb);
	return 0;
}

static int ip4ip6_rcv(struct sk_buff *skb)
{
	return ip6_tnl_rcv(skb, ETH_P_IP, IPPROTO_IPIP,
			   ip4ip6_dscp_ecn_decapsulate);
}

static int ip6ip6_rcv(struct sk_buff *skb)
{
	return ip6_tnl_rcv(skb, ETH_P_IPV6, IPPROTO_IPV6,
			   ip6ip6_dscp_ecn_decapsulate);
}

struct ipv6_tel_txoption {
	struct ipv6_txoptions ops;
	__u8 dst_opt[8];
};

static void init_tel_txopt(struct ipv6_tel_txoption *opt, __u8 encap_limit)
{
	memset(opt, 0, sizeof(struct ipv6_tel_txoption));

	opt->dst_opt[2] = IPV6_TLV_TNL_ENCAP_LIMIT;
	opt->dst_opt[3] = 1;
	opt->dst_opt[4] = encap_limit;
	opt->dst_opt[5] = IPV6_TLV_PADN;
	opt->dst_opt[6] = 1;

	opt->ops.dst0opt = (struct ipv6_opt_hdr *) opt->dst_opt;
	opt->ops.opt_nflen = 8;
}

/**
 * ip6_tnl_addr_conflict - compare packet addresses to tunnel's own
 *   @t: the outgoing tunnel device
 *   @hdr: IPv6 header from the incoming packet
 *
 * Description:
 *   Avoid trivial tunneling loop by checking that tunnel exit-point
 *   doesn't match source of incoming packet.
 *
 * Return:
 *   1 if conflict,
 *   0 else
 **/

static inline bool
ip6_tnl_addr_conflict(const struct ip6_tnl *t, const struct ipv6hdr *hdr)
{
	return ipv6_addr_equal(&t->parms.raddr, &hdr->saddr);
}

int ip6_tnl_xmit_ctl(struct ip6_tnl *t)
{
	struct __ip6_tnl_parm *p = &t->parms;
	int ret = 0;
	struct net *net = t->net;

	if (p->flags & IP6_TNL_F_CAP_XMIT) {
		struct net_device *ldev = NULL;

		rcu_read_lock();
		if (p->link)
			ldev = dev_get_by_index_rcu(net, p->link);

		if (unlikely(!ipv6_chk_addr(net, &p->laddr, ldev, 0)))
			pr_warn("%s xmit: Local address not yet configured!\n",
				p->name);
		else if (!ipv6_addr_is_multicast(&p->raddr) &&
			 unlikely(ipv6_chk_addr(net, &p->raddr, NULL, 0)))
			pr_warn("%s xmit: Routing loop! Remote address found on this node!\n",
				p->name);
		else
			ret = 1;
		rcu_read_unlock();
	}
	return ret;
}
EXPORT_SYMBOL_GPL(ip6_tnl_xmit_ctl);

/**
 * ip6_tnl_xmit2 - encapsulate packet and send
 *   @skb: the outgoing socket buffer
 *   @dev: the outgoing tunnel device
 *   @dsfield: dscp code for outer header
 *   @fl: flow of tunneled packet
 *   @encap_limit: encapsulation limit
 *   @pmtu: Path MTU is stored if packet is too big
 *
 * Description:
 *   Build new header and do some sanity checks on the packet before sending
 *   it.
 *
 * Return:
 *   0 on success
 *   -1 fail
 *   %-EMSGSIZE message too big. return mtu in this case.
 **/

static int ip6_tnl_xmit2(struct sk_buff *skb,
			 struct net_device *dev,
			 __u8 dsfield,
			 struct flowi6 *fl6,
			 int encap_limit,
			 __u32 *pmtu)
{
	struct ip6_tnl *t = netdev_priv(dev);
	struct net *net = t->net;
	struct net_device_stats *stats = &t->dev->stats;
	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
	struct ipv6_tel_txoption opt;
	struct dst_entry *dst = NULL, *ndst = NULL;
	struct net_device *tdev;
	int mtu;
	unsigned int max_headroom = sizeof(struct ipv6hdr);
	u8 proto;
	int err = -1;

	if (!fl6->flowi6_mark)
		dst = ip6_tnl_dst_check(t);
	if (!dst) {
		ndst = ip6_route_output(net, NULL, fl6);

		if (ndst->error)
			goto tx_err_link_failure;
		ndst = xfrm_lookup(net, ndst, flowi6_to_flowi(fl6), NULL, 0);
		if (IS_ERR(ndst)) {
			err = PTR_ERR(ndst);
			ndst = NULL;
			goto tx_err_link_failure;
		}
		dst = ndst;
	}

	tdev = dst->dev;

	if (tdev == dev) {
		stats->collisions++;
		net_warn_ratelimited("%s: Local routing loop detected!\n",
				     t->parms.name);
		goto tx_err_dst_release;
	}
	mtu = dst_mtu(dst) - sizeof (*ipv6h);
	if (encap_limit >= 0) {
		max_headroom += 8;
		mtu -= 8;
	}
	if (mtu < IPV6_MIN_MTU)
		mtu = IPV6_MIN_MTU;
	if (skb_dst(skb))
		skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
	if (skb->len > mtu) {
		*pmtu = mtu;
		err = -EMSGSIZE;
		goto tx_err_dst_release;
	}

	skb_scrub_packet(skb, !net_eq(t->net, dev_net(dev)));