/*
 *      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 <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;
        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 = dev_net(dev);
        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 = dev_net(t->dev);

        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;
                }
                secpath_reset(skb);
                skb->mac_header = skb->network_header;
                skb_reset_network_header(skb);
                skb->protocol = htons(protocol);
                skb->pkt_type = PACKET_HOST;
                memset(skb->cb, 0, sizeof(struct inet6_skb_parm));

                __skb_tunnel_rx(skb, t->dev);

                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 = dev_net(t->dev);

        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 net *net = dev_net(dev);
        struct ip6_tnl *t = netdev_priv(dev);
        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;
        }

        /*
         * Okay, now see if we can stuff it in the buffer as-is.

         */
        max_headroom += LL_RESERVED_SPACE(tdev);

        if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
            (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {
                struct sk_buff *new_skb;

                if (!(new_skb = skb_realloc_headroom(skb, max_headroom)))
                        goto tx_err_dst_release;

                if (skb->sk)
                        skb_set_owner_w(new_skb, skb->sk);
                consume_skb(skb);
                skb = new_skb;
        }
        skb_dst_drop(skb);
        if (fl6->flowi6_mark) {
                skb_dst_set(skb, dst);
                ndst = NULL;
        } else {
                skb_dst_set_noref(skb, dst);
        }
        skb->transport_header = skb->network_header;

        proto = fl6->flowi6_proto;
        if (encap_limit >= 0) {
                init_tel_txopt(&opt, encap_limit);
                ipv6_push_nfrag_opts(skb, &opt.ops, &proto, NULL);
        }

        if (likely(!skb->encapsulation)) {
                skb_reset_inner_headers(skb);
                skb->encapsulation = 1;
        }

        skb_push(skb, sizeof(struct ipv6hdr));
        skb_reset_network_header(skb);
        ipv6h = ipv6_hdr(skb);
        ip6_flow_hdr(ipv6h, INET_ECN_encapsulate(0, dsfield), fl6->flowlabel);
        ipv6h->hop_limit = t->parms.hop_limit;
        ipv6h->nexthdr = proto;
        ipv6h->saddr = fl6->saddr;
        ipv6h->daddr = fl6->daddr;
        ip6tunnel_xmit(skb, dev);
        if (ndst)
                ip6_tnl_dst_store(t, ndst);
        return 0;
tx_err_link_failure:
        stats->tx_carrier_errors++;
        dst_link_failure(skb);
tx_err_dst_release:
        dst_release(ndst);
        return err;
}

static inline int
ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        const struct iphdr  *iph = ip_hdr(skb);
        int encap_limit = -1;
        struct flowi6 fl6;
        __u8 dsfield;
        __u32 mtu;
        int err;

        if ((t->parms.proto != IPPROTO_IPIP && t->parms.proto != 0) ||
            !ip6_tnl_xmit_ctl(t))
                return -1;

        if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
                encap_limit = t->parms.encap_limit;

        memcpy(&fl6, &t->fl.u.ip6, sizeof (fl6));
        fl6.flowi6_proto = IPPROTO_IPIP;

        dsfield = ipv4_get_dsfield(iph);

        if (t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS)
                fl6.flowlabel |= htonl((__u32)iph->tos << IPV6_TCLASS_SHIFT)
                                          & IPV6_TCLASS_MASK;
        if (t->parms.flags & IP6_TNL_F_USE_ORIG_FWMARK)
                fl6.flowi6_mark = skb->mark;

        err = ip6_tnl_xmit2(skb, dev, dsfield, &fl6, encap_limit, &mtu);
        if (err != 0) {
                /* XXX: send ICMP error even if DF is not set. */
                if (err == -EMSGSIZE)
                        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
                                  htonl(mtu));
                return -1;
        }

        return 0;
}

static inline int
ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct ipv6hdr *ipv6h = ipv6_hdr(skb);
        int encap_limit = -1;
        __u16 offset;
        struct flowi6 fl6;
        __u8 dsfield;
        __u32 mtu;
        int err;

        if ((t->parms.proto != IPPROTO_IPV6 && t->parms.proto != 0) ||
            !ip6_tnl_xmit_ctl(t) || ip6_tnl_addr_conflict(t, ipv6h))
                return -1;

        offset = ip6_tnl_parse_tlv_enc_lim(skb, skb_network_header(skb));
        if (offset > 0) {
                struct ipv6_tlv_tnl_enc_lim *tel;
                tel = (struct ipv6_tlv_tnl_enc_lim *)&skb_network_header(skb)[offset];
                if (tel->encap_limit == 0) {
                        icmpv6_send(skb, ICMPV6_PARAMPROB,
                                    ICMPV6_HDR_FIELD, offset + 2);
                        return -1;
                }
                encap_limit = tel->encap_limit - 1;
        } else if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
                encap_limit = t->parms.encap_limit;

        memcpy(&fl6, &t->fl.u.ip6, sizeof (fl6));
        fl6.flowi6_proto = IPPROTO_IPV6;

        dsfield = ipv6_get_dsfield(ipv6h);
        if (t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS)
                fl6.flowlabel |= (*(__be32 *) ipv6h & IPV6_TCLASS_MASK);
        if (t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL)
                fl6.flowlabel |= (*(__be32 *) ipv6h & IPV6_FLOWLABEL_MASK);
        if (t->parms.flags & IP6_TNL_F_USE_ORIG_FWMARK)
                fl6.flowi6_mark = skb->mark;

        err = ip6_tnl_xmit2(skb, dev, dsfield, &fl6, encap_limit, &mtu);
        if (err != 0) {
                if (err == -EMSGSIZE)
                        icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                return -1;
        }

        return 0;
}

static netdev_tx_t
ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct net_device_stats *stats = &t->dev->stats;
        int ret;

        switch (skb->protocol) {
        case htons(ETH_P_IP):
                ret = ip4ip6_tnl_xmit(skb, dev);
                break;
        case htons(ETH_P_IPV6):
                ret = ip6ip6_tnl_xmit(skb, dev);
                break;
        default:
                goto tx_err;
        }

        if (ret < 0)
                goto tx_err;

        return NETDEV_TX_OK;

tx_err:
        stats->tx_errors++;
        stats->tx_dropped++;
        kfree_skb(skb);
        return NETDEV_TX_OK;
}

static void ip6_tnl_link_config(struct ip6_tnl *t)
{
        struct net_device *dev = t->dev;
        struct __ip6_tnl_parm *p = &t->parms;
        struct flowi6 *fl6 = &t->fl.u.ip6;

        memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
        memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr));

        /* Set up flowi template */
        fl6->saddr = p->laddr;
        fl6->daddr = p->raddr;
        fl6->flowi6_oif = p->link;
        fl6->flowlabel = 0;

        if (!(p->flags&IP6_TNL_F_USE_ORIG_TCLASS))
                fl6->flowlabel |= IPV6_TCLASS_MASK & p->flowinfo;
        if (!(p->flags&IP6_TNL_F_USE_ORIG_FLOWLABEL))
                fl6->flowlabel |= IPV6_FLOWLABEL_MASK & p->flowinfo;

        p->flags &= ~(IP6_TNL_F_CAP_XMIT|IP6_TNL_F_CAP_RCV|IP6_TNL_F_CAP_PER_PACKET);
        p->flags |= ip6_tnl_get_cap(t, &p->laddr, &p->raddr);

        if (p->flags&IP6_TNL_F_CAP_XMIT && p->flags&IP6_TNL_F_CAP_RCV)
                dev->flags |= IFF_POINTOPOINT;
        else
                dev->flags &= ~IFF_POINTOPOINT;

        dev->iflink = p->link;

        if (p->flags & IP6_TNL_F_CAP_XMIT) {
                int strict = (ipv6_addr_type(&p->raddr) &
                              (IPV6_ADDR_MULTICAST|IPV6_ADDR_LINKLOCAL));

                struct rt6_info *rt = rt6_lookup(dev_net(dev),
                                                 &p->raddr, &p->laddr,
                                                 p->link, strict);

                if (rt == NULL)
                        return;

                if (rt->dst.dev) {
                        dev->hard_header_len = rt->dst.dev->hard_header_len +
                                sizeof (struct ipv6hdr);

                        dev->mtu = rt->dst.dev->mtu - sizeof (struct ipv6hdr);
                        if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
                                dev->mtu-=8;

                        if (dev->mtu < IPV6_MIN_MTU)
                                dev->mtu = IPV6_MIN_MTU;
                }
                ip6_rt_put(rt);
        }
}

/**
 * ip6_tnl_change - update the tunnel parameters
 *   @t: tunnel to be changed
 *   @p: tunnel configuration parameters
 *
 * Description:
 *   ip6_tnl_change() updates the tunnel parameters
 **/

static int
ip6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p)
{
        t->parms.laddr = p->laddr;
        t->parms.raddr = p->raddr;
        t->parms.flags = p->flags;
        t->parms.hop_limit = p->hop_limit;
        t->parms.encap_limit = p->encap_limit;
        t->parms.flowinfo = p->flowinfo;
        t->parms.link = p->link;
        t->parms.proto = p->proto;
        ip6_tnl_dst_reset(t);
        ip6_tnl_link_config(t);
        return 0;
}

static int ip6_tnl_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p)
{
        struct net *net = dev_net(t->dev);
        struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
        int err;

        ip6_tnl_unlink(ip6n, t);
        synchronize_net();
        err = ip6_tnl_change(t, p);
        ip6_tnl_link(ip6n, t);
        netdev_state_change(t->dev);
        return err;
}

static void
ip6_tnl_parm_from_user(struct __ip6_tnl_parm *p, const struct ip6_tnl_parm *u)
{
        p->laddr = u->laddr;
        p->raddr = u->raddr;
        p->flags = u->flags;
        p->hop_limit = u->hop_limit;
        p->encap_limit = u->encap_limit;
        p->flowinfo = u->flowinfo;
        p->link = u->link;
        p->proto = u->proto;
        memcpy(p->name, u->name, sizeof(u->name));
}

static void
ip6_tnl_parm_to_user(struct ip6_tnl_parm *u, const struct __ip6_tnl_parm *p)
{
        u->laddr = p->laddr;
        u->raddr = p->raddr;
        u->flags = p->flags;
        u->hop_limit = p->hop_limit;
        u->encap_limit = p->encap_limit;
        u->flowinfo = p->flowinfo;
        u->link = p->link;
        u->proto = p->proto;
        memcpy(u->name, p->name, sizeof(u->name));
}

/**
 * ip6_tnl_ioctl - configure ipv6 tunnels from userspace
 *   @dev: virtual device associated with tunnel
 *   @ifr: parameters passed from userspace
 *   @cmd: command to be performed
 *
 * Description:
 *   ip6_tnl_ioctl() is used for managing IPv6 tunnels
 *   from userspace.
 *
 *   The possible commands are the following:
 *     %SIOCGETTUNNEL: get tunnel parameters for device
 *     %SIOCADDTUNNEL: add tunnel matching given tunnel parameters
 *     %SIOCCHGTUNNEL: change tunnel parameters to those given
 *     %SIOCDELTUNNEL: delete tunnel
 *
 *   The fallback device "ip6tnl0", created during module
 *   initialization, can be used for creating other tunnel devices.
 *
 * Return:
 *   0 on success,
 *   %-EFAULT if unable to copy data to or from userspace,
 *   %-EPERM if current process hasn't %CAP_NET_ADMIN set
 *   %-EINVAL if passed tunnel parameters are invalid,
 *   %-EEXIST if changing a tunnel's parameters would cause a conflict
 *   %-ENODEV if attempting to change or delete a nonexisting device
 **/

static int
ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
        int err = 0;
        struct ip6_tnl_parm p;
        struct __ip6_tnl_parm p1;
        struct ip6_tnl *t = NULL;
        struct net *net = dev_net(dev);
        struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

        switch (cmd) {
        case SIOCGETTUNNEL:
                if (dev == ip6n->fb_tnl_dev) {
                        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p))) {
                                err = -EFAULT;
                                break;
                        }
                        ip6_tnl_parm_from_user(&p1, &p);
                        t = ip6_tnl_locate(net, &p1, 0);
                } else {
                        memset(&p, 0, sizeof(p));
                }
                if (t == NULL)
                        t = netdev_priv(dev);
                ip6_tnl_parm_to_user(&p, &t->parms);
                if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof (p))) {
                        err = -EFAULT;
                }
                break;
        case SIOCADDTUNNEL:
        case SIOCCHGTUNNEL:
                err = -EPERM;
                if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
                        break;
                err = -EFAULT;
                if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p)))
                        break;
                err = -EINVAL;
                if (p.proto != IPPROTO_IPV6 && p.proto != IPPROTO_IPIP &&
                    p.proto != 0)
                        break;
                ip6_tnl_parm_from_user(&p1, &p);
                t = ip6_tnl_locate(net, &p1, cmd == SIOCADDTUNNEL);
                if (dev != ip6n->fb_tnl_dev && cmd == SIOCCHGTUNNEL) {
                        if (t != NULL) {
                                if (t->dev != dev) {
                                        err = -EEXIST;
                                        break;
                                }
                        } else
                                t = netdev_priv(dev);

                        err = ip6_tnl_update(t, &p1);
                }
                if (t) {
                        err = 0;
                        ip6_tnl_parm_to_user(&p, &t->parms);
                        if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
                                err = -EFAULT;

                } else
                        err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
                break;
        case SIOCDELTUNNEL:
                err = -EPERM;
                if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
                        break;

                if (dev == ip6n->fb_tnl_dev) {
                        err = -EFAULT;
                        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p)))
                                break;
                        err = -ENOENT;
                        ip6_tnl_parm_from_user(&p1, &p);
                        t = ip6_tnl_locate(net, &p1, 0);
                        if (t == NULL)
                                break;
                        err = -EPERM;
                        if (t->dev == ip6n->fb_tnl_dev)
                                break;
                        dev = t->dev;
                }
                err = 0;
                unregister_netdevice(dev);
                break;
        default:
                err = -EINVAL;
        }
        return err;
}

/**
 * ip6_tnl_change_mtu - change mtu manually for tunnel device
 *   @dev: virtual device associated with tunnel
 *   @new_mtu: the new mtu
 *
 * Return:
 *   0 on success,
 *   %-EINVAL if mtu too small
 **/

static int
ip6_tnl_change_mtu(struct net_device *dev, int new_mtu)
{
        if (new_mtu < IPV6_MIN_MTU) {
                return -EINVAL;
        }
        dev->mtu = new_mtu;
        return 0;
}


static const struct net_device_ops ip6_tnl_netdev_ops = {
        .ndo_uninit     = ip6_tnl_dev_uninit,
        .ndo_start_xmit = ip6_tnl_xmit,
        .ndo_do_ioctl   = ip6_tnl_ioctl,
        .ndo_change_mtu = ip6_tnl_change_mtu,
        .ndo_get_stats  = ip6_get_stats,
};


/**
 * ip6_tnl_dev_setup - setup virtual tunnel device
 *   @dev: virtual device associated with tunnel
 *
 * Description:
 *   Initialize function pointers and device parameters
 **/

static void ip6_tnl_dev_setup(struct net_device *dev)
{
        struct ip6_tnl *t;

        dev->netdev_ops = &ip6_tnl_netdev_ops;
        dev->destructor = ip6_dev_free;

        dev->type = ARPHRD_TUNNEL6;
        dev->hard_header_len = LL_MAX_HEADER + sizeof (struct ipv6hdr);
        dev->mtu = ETH_DATA_LEN - sizeof (struct ipv6hdr);
        t = netdev_priv(dev);
        if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
                dev->mtu-=8;
        dev->flags |= IFF_NOARP;
        dev->addr_len = sizeof(struct in6_addr);
        dev->features |= NETIF_F_NETNS_LOCAL;
        dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
}


/**
 * ip6_tnl_dev_init_gen - general initializer for all tunnel devices
 *   @dev: virtual device associated with tunnel
 **/

static inline int
ip6_tnl_dev_init_gen(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);

        t->dev = dev;
        dev->tstats = alloc_percpu(struct pcpu_tstats);
        if (!dev->tstats)
                return -ENOMEM;
        return 0;
}

/**
 * ip6_tnl_dev_init - initializer for all non fallback tunnel devices
 *   @dev: virtual device associated with tunnel
 **/

static int ip6_tnl_dev_init(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        int err = ip6_tnl_dev_init_gen(dev);

        if (err)
                return err;
        ip6_tnl_link_config(t);
        return 0;
}

/**
 * ip6_fb_tnl_dev_init - initializer for fallback tunnel device
 *   @dev: fallback device
 *
 * Return: 0
 **/

static int __net_init ip6_fb_tnl_dev_init(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 = ip6_tnl_dev_init_gen(dev);

        if (err)
                return err;

        t->parms.proto = IPPROTO_IPV6;
        dev_hold(dev);

        ip6_tnl_link_config(t);

        rcu_assign_pointer(ip6n->tnls_wc[0], t);
        return 0;
}

static int ip6_tnl_validate(struct nlattr *tb[], struct nlattr *data[])
{
        u8 proto;

        if (!data)
                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 ip6_tnl_netlink_parms(struct nlattr *data[],
                                  struct __ip6_tnl_parm *parms)
{
        memset(parms, 0, sizeof(*parms));

        if (!data)
                return;

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

        if (data[IFLA_IPTUN_LOCAL])
                nla_memcpy(&parms->laddr, data[IFLA_IPTUN_LOCAL],
                           sizeof(struct in6_addr));

        if (data[IFLA_IPTUN_REMOTE])
                nla_memcpy(&parms->raddr, data[IFLA_IPTUN_REMOTE],
                           sizeof(struct in6_addr));

        if (data[IFLA_IPTUN_TTL])
                parms->hop_limit = nla_get_u8(data[IFLA_IPTUN_TTL]);

        if (data[IFLA_IPTUN_ENCAP_LIMIT])
                parms->encap_limit = nla_get_u8(data[IFLA_IPTUN_ENCAP_LIMIT]);

        if (data[IFLA_IPTUN_FLOWINFO])
                parms->flowinfo = nla_get_be32(data[IFLA_IPTUN_FLOWINFO]);

        if (data[IFLA_IPTUN_FLAGS])
                parms->flags = nla_get_u32(data[IFLA_IPTUN_FLAGS]);

        if (data[IFLA_IPTUN_PROTO])
                parms->proto = nla_get_u8(data[IFLA_IPTUN_PROTO]);
}

static int ip6_tnl_newlink(struct net *src_net, struct net_device *dev,
                           struct nlattr *tb[], struct nlattr *data[])
{
        struct net *net = dev_net(dev);
        struct ip6_tnl *nt;

        nt = netdev_priv(dev);
        ip6_tnl_netlink_parms(data, &nt->parms);

        if (ip6_tnl_locate(net, &nt->parms, 0))
                return -EEXIST;

        return ip6_tnl_create2(dev);
}

static int ip6_tnl_changelink(struct net_device *dev, struct nlattr *tb[],
                              struct nlattr *data[])
{
        struct ip6_tnl *t;
        struct __ip6_tnl_parm p;
        struct net *net = dev_net(dev);
        struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

        if (dev == ip6n->fb_tnl_dev)
                return -EINVAL;

        ip6_tnl_netlink_parms(data, &p);

        t = ip6_tnl_locate(net, &p, 0);

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

        return ip6_tnl_update(t, &p);
}

static size_t ip6_tnl_get_size(const struct net_device *dev)
{
        return
                /* IFLA_IPTUN_LINK */
                nla_total_size(4) +
                /* IFLA_IPTUN_LOCAL */
                nla_total_size(sizeof(struct in6_addr)) +
                /* IFLA_IPTUN_REMOTE */
                nla_total_size(sizeof(struct in6_addr)) +
                /* IFLA_IPTUN_TTL */
                nla_total_size(1) +
                /* IFLA_IPTUN_ENCAP_LIMIT */
                nla_total_size(1) +
                /* IFLA_IPTUN_FLOWINFO */
                nla_total_size(4) +
                /* IFLA_IPTUN_FLAGS */
                nla_total_size(4) +
                /* IFLA_IPTUN_PROTO */
                nla_total_size(1) +
                0;
}

static int ip6_tnl_fill_info(struct sk_buff *skb, const struct net_device *dev)
{
        struct ip6_tnl *tunnel = netdev_priv(dev);
        struct __ip6_tnl_parm *parm = &tunnel->parms;

        if (nla_put_u32(skb, IFLA_IPTUN_LINK, parm->link) ||
            nla_put(skb, IFLA_IPTUN_LOCAL, sizeof(struct in6_addr),
                    &parm->raddr) ||
            nla_put(skb, IFLA_IPTUN_REMOTE, sizeof(struct in6_addr),
                    &parm->laddr) ||
            nla_put_u8(skb, IFLA_IPTUN_TTL, parm->hop_limit) ||
            nla_put_u8(skb, IFLA_IPTUN_ENCAP_LIMIT, parm->encap_limit) ||
            nla_put_be32(skb, IFLA_IPTUN_FLOWINFO, parm->flowinfo) ||
            nla_put_u32(skb, IFLA_IPTUN_FLAGS, parm->flags) ||
            nla_put_u8(skb, IFLA_IPTUN_PROTO, parm->proto))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static const struct nla_policy ip6_tnl_policy[IFLA_IPTUN_MAX + 1] = {
        [IFLA_IPTUN_LINK]               = { .type = NLA_U32 },
        [IFLA_IPTUN_LOCAL]              = { .len = sizeof(struct in6_addr) },
        [IFLA_IPTUN_REMOTE]             = { .len = sizeof(struct in6_addr) },
        [IFLA_IPTUN_TTL]                = { .type = NLA_U8 },
        [IFLA_IPTUN_ENCAP_LIMIT]        = { .type = NLA_U8 },
        [IFLA_IPTUN_FLOWINFO]           = { .type = NLA_U32 },
        [IFLA_IPTUN_FLAGS]              = { .type = NLA_U32 },
        [IFLA_IPTUN_PROTO]              = { .type = NLA_U8 },
};

static struct rtnl_link_ops ip6_link_ops __read_mostly = {
        .kind           = "ip6tnl",
        .maxtype        = IFLA_IPTUN_MAX,
        .policy         = ip6_tnl_policy,
        .priv_size      = sizeof(struct ip6_tnl),
        .setup          = ip6_tnl_dev_setup,
        .validate       = ip6_tnl_validate,
        .newlink        = ip6_tnl_newlink,
        .changelink     = ip6_tnl_changelink,
        .get_size       = ip6_tnl_get_size,
        .fill_info      = ip6_tnl_fill_info,
};

static struct xfrm6_tunnel ip4ip6_handler __read_mostly = {
        .handler        = ip4ip6_rcv,
        .err_handler    = ip4ip6_err,
        .priority       =       1,
};

static struct xfrm6_tunnel ip6ip6_handler __read_mostly = {
        .handler        = ip6ip6_rcv,
        .err_handler    = ip6ip6_err,
        .priority       =       1,
};

static void __net_exit ip6_tnl_destroy_tunnels(struct ip6_tnl_net *ip6n)
{
        int h;
        struct ip6_tnl *t;
        LIST_HEAD(list);

        for (h = 0; h < HASH_SIZE; h++) {
                t = rtnl_dereference(ip6n->tnls_r_l[h]);
                while (t != NULL) {
                        unregister_netdevice_queue(t->dev, &list);
                        t = rtnl_dereference(t->next);
                }
        }

        t = rtnl_dereference(ip6n->tnls_wc[0]);
        unregister_netdevice_queue(t->dev, &list);
        unregister_netdevice_many(&list);
}

static int __net_init ip6_tnl_init_net(struct net *net)
{
        struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
        struct ip6_tnl *t = NULL;
        int err;

        ip6n->tnls[0] = ip6n->tnls_wc;
        ip6n->tnls[1] = ip6n->tnls_r_l;

        err = -ENOMEM;
        ip6n->fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6tnl0",
                                      ip6_tnl_dev_setup);

        if (!ip6n->fb_tnl_dev)
                goto err_alloc_dev;
        dev_net_set(ip6n->fb_tnl_dev, net);

        err = ip6_fb_tnl_dev_init(ip6n->fb_tnl_dev);
        if (err < 0)
                goto err_register;

        err = register_netdev(ip6n->fb_tnl_dev);
        if (err < 0)
                goto err_register;

        t = netdev_priv(ip6n->fb_tnl_dev);

        strcpy(t->parms.name, ip6n->fb_tnl_dev->name);
        return 0;

err_register:
        ip6_dev_free(ip6n->fb_tnl_dev);
err_alloc_dev:
        return err;
}

static void __net_exit ip6_tnl_exit_net(struct net *net)
{
        struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

        rtnl_lock();
        ip6_tnl_destroy_tunnels(ip6n);
        rtnl_unlock();
}

static struct pernet_operations ip6_tnl_net_ops = {
        .init = ip6_tnl_init_net,
        .exit = ip6_tnl_exit_net,
        .id   = &ip6_tnl_net_id,
        .size = sizeof(struct ip6_tnl_net),
};

/**
 * ip6_tunnel_init - register protocol and reserve needed resources
 *
 * Return: 0 on success
 **/

static int __init ip6_tunnel_init(void)
{
        int  err;

        err = register_pernet_device(&ip6_tnl_net_ops);
        if (err < 0)
                goto out_pernet;

        err = xfrm6_tunnel_register(&ip4ip6_handler, AF_INET);
        if (err < 0) {
                pr_err("%s: can't register ip4ip6\n", __func__);
                goto out_ip4ip6;
        }

        err = xfrm6_tunnel_register(&ip6ip6_handler, AF_INET6);
        if (err < 0) {
                pr_err("%s: can't register ip6ip6\n", __func__);
                goto out_ip6ip6;
        }
        err = rtnl_link_register(&ip6_link_ops);
        if (err < 0)
                goto rtnl_link_failed;

        return 0;

rtnl_link_failed:
        xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6);
out_ip6ip6:
        xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET);
out_ip4ip6:
        unregister_pernet_device(&ip6_tnl_net_ops);
out_pernet:
        return err;
}

/**
 * ip6_tunnel_cleanup - free resources and unregister protocol
 **/

static void __exit ip6_tunnel_cleanup(void)
{
        rtnl_link_unregister(&ip6_link_ops);
        if (xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET))
                pr_info("%s: can't deregister ip4ip6\n", __func__);

        if (xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6))
                pr_info("%s: can't deregister ip6ip6\n", __func__);

        unregister_pernet_device(&ip6_tnl_net_ops);
}

module_init(ip6_tunnel_init);
module_exit(ip6_tunnel_cleanup);