Merge git://git.kernel.org/pub/scm/linux/kernel/git/sam/kbuild

[mirror_ubuntu-bionic-kernel.git] / net / ipv6 / ip6_tunnel.c

/*
 *      IPv6 over IPv6 tunnel device
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Ville Nuorvala          <vnuorval@tcs.hut.fi>   
 *
 *      $Id$
 *
 *      Based on:
 *      linux/net/ipv6/sit.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.
 *
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/sockios.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 <asm/uaccess.h>
#include <asm/atomic.h>

#include <net/ip.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>

MODULE_AUTHOR("Ville Nuorvala");
MODULE_DESCRIPTION("IPv6-in-IPv6 tunnel");
MODULE_LICENSE("GPL");

#define IPV6_TLV_TEL_DST_SIZE 8

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

#define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)

#define HASH_SIZE  32

#define HASH(addr) (((addr)->s6_addr32[0] ^ (addr)->s6_addr32[1] ^ \
                     (addr)->s6_addr32[2] ^ (addr)->s6_addr32[3]) & \
                    (HASH_SIZE - 1))

static int ip6ip6_fb_tnl_dev_init(struct net_device *dev);
static int ip6ip6_tnl_dev_init(struct net_device *dev);
static void ip6ip6_tnl_dev_setup(struct net_device *dev);

/* the IPv6 tunnel fallback device */
static struct net_device *ip6ip6_fb_tnl_dev;


/* lists for storing tunnels in use */
static struct ip6_tnl *tnls_r_l[HASH_SIZE];
static struct ip6_tnl *tnls_wc[1];
static struct ip6_tnl **tnls[2] = { tnls_wc, tnls_r_l };

/* lock for the tunnel lists */
static DEFINE_RWLOCK(ip6ip6_lock);

static inline 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;
}

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

static inline 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;
}

/**
 * ip6ip6_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
 **/

static struct ip6_tnl *
ip6ip6_tnl_lookup(struct in6_addr *remote, struct in6_addr *local)
{
        unsigned h0 = HASH(remote);
        unsigned h1 = HASH(local);
        struct ip6_tnl *t;

        for (t = tnls_r_l[h0 ^ h1]; t; t = t->next) {
                if (ipv6_addr_equal(local, &t->parms.laddr) &&
                    ipv6_addr_equal(remote, &t->parms.raddr) &&
                    (t->dev->flags & IFF_UP))
                        return t;
        }
        if ((t = tnls_wc[0]) != NULL && (t->dev->flags & IFF_UP))
                return t;

        return NULL;
}

/**
 * ip6ip6_bucket - get head of list matching given tunnel parameters
 *   @p: parameters containing tunnel end-points 
 *
 * Description:
 *   ip6ip6_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 **
ip6ip6_bucket(struct ip6_tnl_parm *p)
{
        struct in6_addr *remote = &p->raddr;
        struct in6_addr *local = &p->laddr;
        unsigned h = 0;
        int prio = 0;

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

/**
 * ip6ip6_tnl_link - add tunnel to hash table
 *   @t: tunnel to be added
 **/

static void
ip6ip6_tnl_link(struct ip6_tnl *t)
{
        struct ip6_tnl **tp = ip6ip6_bucket(&t->parms);

        t->next = *tp;
        write_lock_bh(&ip6ip6_lock);
        *tp = t;
        write_unlock_bh(&ip6ip6_lock);
}

/**
 * ip6ip6_tnl_unlink - remove tunnel from hash table
 *   @t: tunnel to be removed
 **/

static void
ip6ip6_tnl_unlink(struct ip6_tnl *t)
{
        struct ip6_tnl **tp;

        for (tp = ip6ip6_bucket(&t->parms); *tp; tp = &(*tp)->next) {
                if (t == *tp) {
                        write_lock_bh(&ip6ip6_lock);
                        *tp = t->next;
                        write_unlock_bh(&ip6ip6_lock);
                        break;
                }
        }
}

/**
 * ip6_tnl_create() - create a new tunnel
 *   @p: tunnel parameters
 *   @pt: pointer to new tunnel
 *
 * Description:
 *   Create tunnel matching given parameters.
 * 
 * Return: 
 *   0 on success
 **/

static int
ip6_tnl_create(struct ip6_tnl_parm *p, struct ip6_tnl **pt)
{
        struct net_device *dev;
        struct ip6_tnl *t;
        char name[IFNAMSIZ];
        int err;

        if (p->name[0]) {
                strlcpy(name, p->name, IFNAMSIZ);
        } else {
                int i;
                for (i = 1; i < IP6_TNL_MAX; i++) {
                        sprintf(name, "ip6tnl%d", i);
                        if (__dev_get_by_name(name) == NULL)
                                break;
                }
                if (i == IP6_TNL_MAX) 
                        return -ENOBUFS;
        }
        dev = alloc_netdev(sizeof (*t), name, ip6ip6_tnl_dev_setup);
        if (dev == NULL)
                return -ENOMEM;

        t = netdev_priv(dev);
        dev->init = ip6ip6_tnl_dev_init;
        t->parms = *p;

        if ((err = register_netdevice(dev)) < 0) {
                free_netdev(dev);
                return err;
        }
        dev_hold(dev);

        ip6ip6_tnl_link(t);
        *pt = t;
        return 0;
}

/**
 * ip6ip6_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:
 *   ip6ip6_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:
 *   0 if tunnel located or created,
 *   -EINVAL if parameters incorrect,
 *   -ENODEV if no matching tunnel available
 **/

static int
ip6ip6_tnl_locate(struct ip6_tnl_parm *p, struct ip6_tnl **pt, int create)
{
        struct in6_addr *remote = &p->raddr;
        struct in6_addr *local = &p->laddr;
        struct ip6_tnl *t;

        if (p->proto != IPPROTO_IPV6)
                return -EINVAL;

        for (t = *ip6ip6_bucket(p); t; t = t->next) {
                if (ipv6_addr_equal(local, &t->parms.laddr) &&
                    ipv6_addr_equal(remote, &t->parms.raddr)) {
                        *pt = t;
                        return (create ? -EEXIST : 0);
                }
        }
        if (!create)
                return -ENODEV;
        
        return ip6_tnl_create(p, pt);
}

/**
 * ip6ip6_tnl_dev_uninit - tunnel device uninitializer
 *   @dev: the device to be destroyed
 *   
 * Description:
 *   ip6ip6_tnl_dev_uninit() removes tunnel from its list
 **/

static void
ip6ip6_tnl_dev_uninit(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);

        if (dev == ip6ip6_fb_tnl_dev) {
                write_lock_bh(&ip6ip6_lock);
                tnls_wc[0] = NULL;
                write_unlock_bh(&ip6ip6_lock);
        } else {
                ip6ip6_tnl_unlink(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
 **/

static __u16
parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw)
{
        struct ipv6hdr *ipv6h = (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;
}

/**
 * ip6ip6_err - tunnel error handler
 *
 * Description:
 *   ip6ip6_err() should handle errors in the tunnel according
 *   to the specifications in RFC 2473.
 **/

static int
ip6ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
           int type, int code, int offset, __u32 info)
{
        struct ipv6hdr *ipv6h = (struct ipv6hdr *) skb->data;
        struct ip6_tnl *t;
        int rel_msg = 0;
        int rel_type = ICMPV6_DEST_UNREACH;
        int 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. */

        read_lock(&ip6ip6_lock);
        if ((t = ip6ip6_tnl_lookup(&ipv6h->daddr, &ipv6h->saddr)) == NULL)
                goto out;

        err = 0;

        switch (type) {
                __u32 teli;
                struct ipv6_tlv_tnl_enc_lim *tel;
                __u32 mtu;
        case ICMPV6_DEST_UNREACH:
                if (net_ratelimit())
                        printk(KERN_WARNING
                               "%s: Path to destination invalid "
                               "or inactive!\n", t->parms.name);
                rel_msg = 1;
                break;
        case ICMPV6_TIME_EXCEED:
                if (code == ICMPV6_EXC_HOPLIMIT) {
                        if (net_ratelimit())
                                printk(KERN_WARNING
                                       "%s: Too small hop limit or "
                                       "routing loop in tunnel!\n", 
                                       t->parms.name);
                        rel_msg = 1;
                }
                break;
        case ICMPV6_PARAMPROB:
                /* ignore if parameter problem not caused by a tunnel
                   encapsulation limit sub-option */
                if (code != ICMPV6_HDR_FIELD) {
                        break;
                }
                teli = parse_tlv_tnl_enc_lim(skb, skb->data);

                if (teli && teli == ntohl(info) - 2) {
                        tel = (struct ipv6_tlv_tnl_enc_lim *) &skb->data[teli];
                        if (tel->encap_limit == 0) {
                                if (net_ratelimit())
                                        printk(KERN_WARNING
                                               "%s: Too small encapsulation "
                                               "limit or routing loop in "
                                               "tunnel!\n", t->parms.name);
                                rel_msg = 1;
                        }
                }
                break;
        case ICMPV6_PKT_TOOBIG:
                mtu = ntohl(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;
        }
        if (rel_msg &&  pskb_may_pull(skb, offset + sizeof (*ipv6h))) {
                struct rt6_info *rt;
                struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
                if (!skb2)
                        goto out;

                dst_release(skb2->dst);
                skb2->dst = NULL;
                skb_pull(skb2, offset);
                skb2->nh.raw = skb2->data;

                /* Try to guess incoming interface */
                rt = rt6_lookup(&skb2->nh.ipv6h->saddr, NULL, 0, 0);

                if (rt && rt->rt6i_dev)
                        skb2->dev = rt->rt6i_dev;

                icmpv6_send(skb2, rel_type, rel_code, rel_info, skb2->dev);

                if (rt)
                        dst_release(&rt->u.dst);

                kfree_skb(skb2);
        }
out:
        read_unlock(&ip6ip6_lock);
        return err;
}

static inline void ip6ip6_ecn_decapsulate(struct ipv6hdr *outer_iph,
                                          struct sk_buff *skb)
{
        struct ipv6hdr *inner_iph = skb->nh.ipv6h;

        if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
                IP6_ECN_set_ce(inner_iph);
}

/**
 * ip6ip6_rcv - decapsulate IPv6 packet and retransmit it locally
 *   @skb: received socket buffer
 *
 * Return: 0
 **/

static int 
ip6ip6_rcv(struct sk_buff *skb)
{
        struct ipv6hdr *ipv6h;
        struct ip6_tnl *t;

        ipv6h = skb->nh.ipv6h;

        read_lock(&ip6ip6_lock);

        if ((t = ip6ip6_tnl_lookup(&ipv6h->saddr, &ipv6h->daddr)) != NULL) {
                if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
                        read_unlock(&ip6ip6_lock);
                        goto discard;
                }

                if (!(t->parms.flags & IP6_TNL_F_CAP_RCV)) {
                        t->stat.rx_dropped++;
                        read_unlock(&ip6ip6_lock);
                        goto discard;
                }
                secpath_reset(skb);
                skb->mac.raw = skb->nh.raw;
                skb->nh.raw = skb->data;
                skb->protocol = htons(ETH_P_IPV6);
                skb->pkt_type = PACKET_HOST;
                memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
                skb->dev = t->dev;
                dst_release(skb->dst);
                skb->dst = NULL;
                if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)
                        ipv6_copy_dscp(ipv6h, skb->nh.ipv6h);
                ip6ip6_ecn_decapsulate(ipv6h, skb);
                t->stat.rx_packets++;
                t->stat.rx_bytes += skb->len;
                netif_rx(skb);
                read_unlock(&ip6ip6_lock);
                return 0;
        }
        read_unlock(&ip6ip6_lock);
        return 1;

discard:
        kfree_skb(skb);
        return 0;
}

static inline struct ipv6_txoptions *create_tel(__u8 encap_limit)
{
        struct ipv6_tlv_tnl_enc_lim *tel;
        struct ipv6_txoptions *opt;
        __u8 *raw;

        int opt_len = sizeof(*opt) + 8;

        if (!(opt = kmalloc(opt_len, GFP_ATOMIC))) {
                return NULL;
        }
        memset(opt, 0, opt_len);
        opt->tot_len = opt_len;
        opt->dst0opt = (struct ipv6_opt_hdr *) (opt + 1);
        opt->opt_nflen = 8;

        tel = (struct ipv6_tlv_tnl_enc_lim *) (opt->dst0opt + 1);
        tel->type = IPV6_TLV_TNL_ENCAP_LIMIT;
        tel->length = 1;
        tel->encap_limit = encap_limit;

        raw = (__u8 *) opt->dst0opt;
        raw[5] = IPV6_TLV_PADN;
        raw[6] = 1;

        return opt;
}

/**
 * ip6ip6_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 int
ip6ip6_tnl_addr_conflict(struct ip6_tnl *t, struct ipv6hdr *hdr)
{
        return ipv6_addr_equal(&t->parms.raddr, &hdr->saddr);
}

/**
 * ip6ip6_tnl_xmit - encapsulate packet and send 
 *   @skb: the outgoing socket buffer
 *   @dev: the outgoing tunnel device 
 *
 * Description:
 *   Build new header and do some sanity checks on the packet before sending
 *   it.
 *
 * Return: 
 *   0
 **/

static int 
ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct net_device_stats *stats = &t->stat;
        struct ipv6hdr *ipv6h = skb->nh.ipv6h;
        struct ipv6_txoptions *opt = NULL;
        int encap_limit = -1;
        __u16 offset;
        struct flowi fl;
        struct dst_entry *dst;
        struct net_device *tdev;
        int mtu;
        int max_headroom = sizeof(struct ipv6hdr);
        u8 proto;
        int err;
        int pkt_len;
        int dsfield;

        if (t->recursion++) {
                stats->collisions++;
                goto tx_err;
        }
        if (skb->protocol != htons(ETH_P_IPV6) ||
            !(t->parms.flags & IP6_TNL_F_CAP_XMIT) ||
            ip6ip6_tnl_addr_conflict(t, ipv6h)) {
                goto tx_err;
        }
        if ((offset = parse_tlv_tnl_enc_lim(skb, skb->nh.raw)) > 0) {
                struct ipv6_tlv_tnl_enc_lim *tel;
                tel = (struct ipv6_tlv_tnl_enc_lim *) &skb->nh.raw[offset];
                if (tel->encap_limit == 0) {
                        icmpv6_send(skb, ICMPV6_PARAMPROB,
                                    ICMPV6_HDR_FIELD, offset + 2, skb->dev);
                        goto tx_err;
                }
                encap_limit = tel->encap_limit - 1;
        } else if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT)) {
                encap_limit = t->parms.encap_limit;
        }
        memcpy(&fl, &t->fl, sizeof (fl));
        proto = fl.proto;

        dsfield = ipv6_get_dsfield(ipv6h);
        if ((t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS))
                fl.fl6_flowlabel |= (*(__u32 *) ipv6h & IPV6_TCLASS_MASK);
        if ((t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL))
                fl.fl6_flowlabel |= (*(__u32 *) ipv6h & IPV6_FLOWLABEL_MASK);

        if (encap_limit >= 0 && (opt = create_tel(encap_limit)) == NULL)
                goto tx_err;

        if ((dst = ip6_tnl_dst_check(t)) != NULL)
                dst_hold(dst);
        else {
                dst = ip6_route_output(NULL, &fl);

                if (dst->error || xfrm_lookup(&dst, &fl, NULL, 0) < 0)
                        goto tx_err_link_failure;
        }

        tdev = dst->dev;

        if (tdev == dev) {
                stats->collisions++;
                if (net_ratelimit())
                        printk(KERN_WARNING 
                               "%s: Local routing loop detected!\n",
                               t->parms.name);
                goto tx_err_dst_release;
        }
        mtu = dst_mtu(dst) - sizeof (*ipv6h);
        if (opt) {
                max_headroom += 8;
                mtu -= 8;
        }
        if (mtu < IPV6_MIN_MTU)
                mtu = IPV6_MIN_MTU;
        if (skb->dst && mtu < dst_mtu(skb->dst)) {
                struct rt6_info *rt = (struct rt6_info *) skb->dst;
                rt->rt6i_flags |= RTF_MODIFIED;
                rt->u.dst.metrics[RTAX_MTU-1] = mtu;
        }
        if (skb->len > mtu) {
                icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev);
                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_cloned(skb) || skb_shared(skb)) {
                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);
                kfree_skb(skb);
                skb = new_skb;
        }
        dst_release(skb->dst);
        skb->dst = dst_clone(dst);

        skb->h.raw = skb->nh.raw;

        if (opt)
                ipv6_push_nfrag_opts(skb, opt, &proto, NULL);

        skb->nh.raw = skb_push(skb, sizeof(struct ipv6hdr));
        ipv6h = skb->nh.ipv6h;
        *(u32*)ipv6h = fl.fl6_flowlabel | htonl(0x60000000);
        dsfield = INET_ECN_encapsulate(0, dsfield);
        ipv6_change_dsfield(ipv6h, ~INET_ECN_MASK, dsfield);
        ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
        ipv6h->hop_limit = t->parms.hop_limit;
        ipv6h->nexthdr = proto;
        ipv6_addr_copy(&ipv6h->saddr, &fl.fl6_src);
        ipv6_addr_copy(&ipv6h->daddr, &fl.fl6_dst);
        nf_reset(skb);
        pkt_len = skb->len;
        err = NF_HOOK(PF_INET6, NF_IP6_LOCAL_OUT, skb, NULL, 
                      skb->dst->dev, dst_output);

        if (err == NET_XMIT_SUCCESS || err == NET_XMIT_CN) {
                stats->tx_bytes += pkt_len;
                stats->tx_packets++;
        } else {
                stats->tx_errors++;
                stats->tx_aborted_errors++;
        }
        ip6_tnl_dst_store(t, dst);

        kfree(opt);

        t->recursion--;
        return 0;
tx_err_link_failure:
        stats->tx_carrier_errors++;
        dst_link_failure(skb);
tx_err_dst_release:
        dst_release(dst);
        kfree(opt);
tx_err:
        stats->tx_errors++;
        stats->tx_dropped++;
        kfree_skb(skb);
        t->recursion--;
        return 0;
}

static void ip6_tnl_set_cap(struct ip6_tnl *t)
{
        struct ip6_tnl_parm *p = &t->parms;
        struct in6_addr *laddr = &p->laddr;
        struct in6_addr *raddr = &p->raddr;
        int ltype = ipv6_addr_type(laddr);
        int rtype = ipv6_addr_type(raddr);

        p->flags &= ~(IP6_TNL_F_CAP_XMIT|IP6_TNL_F_CAP_RCV);

        if (ltype != IPV6_ADDR_ANY && rtype != IPV6_ADDR_ANY &&
            ((ltype|rtype) &
             (IPV6_ADDR_UNICAST|
              IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL|
              IPV6_ADDR_MAPPED|IPV6_ADDR_RESERVED)) == IPV6_ADDR_UNICAST) {
                struct net_device *ldev = NULL;
                int l_ok = 1;
                int r_ok = 1;

                if (p->link)
                        ldev = dev_get_by_index(p->link);
                
                if (ltype&IPV6_ADDR_UNICAST && !ipv6_chk_addr(laddr, ldev, 0))
                        l_ok = 0;
                
                if (rtype&IPV6_ADDR_UNICAST && ipv6_chk_addr(raddr, NULL, 0))
                        r_ok = 0;
                
                if (l_ok && r_ok) {
                        if (ltype&IPV6_ADDR_UNICAST)
                                p->flags |= IP6_TNL_F_CAP_XMIT;
                        if (rtype&IPV6_ADDR_UNICAST)
                                p->flags |= IP6_TNL_F_CAP_RCV;
                }
                if (ldev)
                        dev_put(ldev);
        }
}

static void ip6ip6_tnl_link_config(struct ip6_tnl *t)
{
        struct net_device *dev = t->dev;
        struct ip6_tnl_parm *p = &t->parms;
        struct flowi *fl = &t->fl;

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

        /* Set up flowi template */
        ipv6_addr_copy(&fl->fl6_src, &p->laddr);
        ipv6_addr_copy(&fl->fl6_dst, &p->raddr);
        fl->oif = p->link;
        fl->fl6_flowlabel = 0;

        if (!(p->flags&IP6_TNL_F_USE_ORIG_TCLASS))
                fl->fl6_flowlabel |= IPV6_TCLASS_MASK & p->flowinfo;
        if (!(p->flags&IP6_TNL_F_USE_ORIG_FLOWLABEL))
                fl->fl6_flowlabel |= IPV6_FLOWLABEL_MASK & p->flowinfo;

        ip6_tnl_set_cap(t);

        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) {
                struct rt6_info *rt = rt6_lookup(&p->raddr, &p->laddr,
                                                 p->link, 0);

                if (rt == NULL)
                        return;

                if (rt->rt6i_dev) {
                        dev->hard_header_len = rt->rt6i_dev->hard_header_len +
                                sizeof (struct ipv6hdr);

                        dev->mtu = rt->rt6i_dev->mtu - sizeof (struct ipv6hdr);

                        if (dev->mtu < IPV6_MIN_MTU)
                                dev->mtu = IPV6_MIN_MTU;
                }
                dst_release(&rt->u.dst);
        }
}

/**
 * ip6ip6_tnl_change - update the tunnel parameters
 *   @t: tunnel to be changed
 *   @p: tunnel configuration parameters
 *   @active: != 0 if tunnel is ready for use
 *
 * Description:
 *   ip6ip6_tnl_change() updates the tunnel parameters
 **/

static int
ip6ip6_tnl_change(struct ip6_tnl *t, struct ip6_tnl_parm *p)
{
        ipv6_addr_copy(&t->parms.laddr, &p->laddr);
        ipv6_addr_copy(&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;
        ip6_tnl_dst_reset(t);
        ip6ip6_tnl_link_config(t);
        return 0;
}

/**
 * ip6ip6_tnl_ioctl - configure ipv6 tunnels from userspace 
 *   @dev: virtual device associated with tunnel
 *   @ifr: parameters passed from userspace
 *   @cmd: command to be performed
 *
 * Description:
 *   ip6ip6_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
ip6ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
        int err = 0;
        int create;
        struct ip6_tnl_parm p;
        struct ip6_tnl *t = NULL;

        switch (cmd) {
        case SIOCGETTUNNEL:
                if (dev == ip6ip6_fb_tnl_dev) {
                        if (copy_from_user(&p,
                                           ifr->ifr_ifru.ifru_data,
                                           sizeof (p))) {
                                err = -EFAULT;
                                break;
                        }
                        if ((err = ip6ip6_tnl_locate(&p, &t, 0)) == -ENODEV)
                                t = netdev_priv(dev);
                        else if (err)
                                break;
                } else
                        t = netdev_priv(dev);

                memcpy(&p, &t->parms, sizeof (p));
                if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof (p))) {
                        err = -EFAULT;
                }
                break;
        case SIOCADDTUNNEL:
        case SIOCCHGTUNNEL:
                err = -EPERM;
                create = (cmd == SIOCADDTUNNEL);
                if (!capable(CAP_NET_ADMIN))
                        break;
                if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p))) {
                        err = -EFAULT;
                        break;
                }
                if (!create && dev != ip6ip6_fb_tnl_dev) {
                        t = netdev_priv(dev);
                }
                if (!t && (err = ip6ip6_tnl_locate(&p, &t, create))) {
                        break;
                }
                if (cmd == SIOCCHGTUNNEL) {
                        if (t->dev != dev) {
                                err = -EEXIST;
                                break;
                        }
                        ip6ip6_tnl_unlink(t);
                        err = ip6ip6_tnl_change(t, &p);
                        ip6ip6_tnl_link(t);
                        netdev_state_change(dev);
                }
                if (copy_to_user(ifr->ifr_ifru.ifru_data,
                                 &t->parms, sizeof (p))) {
                        err = -EFAULT;
                } else {
                        err = 0;
                }
                break;
        case SIOCDELTUNNEL:
                err = -EPERM;
                if (!capable(CAP_NET_ADMIN))
                        break;

                if (dev == ip6ip6_fb_tnl_dev) {
                        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data,
                                           sizeof (p))) {
                                err = -EFAULT;
                                break;
                        }
                        err = ip6ip6_tnl_locate(&p, &t, 0);
                        if (err)
                                break;
                        if (t == netdev_priv(ip6ip6_fb_tnl_dev)) {
                                err = -EPERM;
                                break;
                        }
                } else {
                        t = netdev_priv(dev);
                }
                err = unregister_netdevice(t->dev);
                break;
        default:
                err = -EINVAL;
        }
        return err;
}

/**
 * ip6ip6_tnl_get_stats - return the stats for tunnel device 
 *   @dev: virtual device associated with tunnel
 *
 * Return: stats for device
 **/

static struct net_device_stats *
ip6ip6_tnl_get_stats(struct net_device *dev)
{
        return &(((struct ip6_tnl *)netdev_priv(dev))->stat);
}

/**
 * ip6ip6_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
ip6ip6_tnl_change_mtu(struct net_device *dev, int new_mtu)
{
        if (new_mtu < IPV6_MIN_MTU) {
                return -EINVAL;
        }
        dev->mtu = new_mtu;
        return 0;
}

/**
 * ip6ip6_tnl_dev_setup - setup virtual tunnel device
 *   @dev: virtual device associated with tunnel
 *
 * Description:
 *   Initialize function pointers and device parameters
 **/

static void ip6ip6_tnl_dev_setup(struct net_device *dev)
{
        SET_MODULE_OWNER(dev);
        dev->uninit = ip6ip6_tnl_dev_uninit;
        dev->destructor = free_netdev;
        dev->hard_start_xmit = ip6ip6_tnl_xmit;
        dev->get_stats = ip6ip6_tnl_get_stats;
        dev->do_ioctl = ip6ip6_tnl_ioctl;
        dev->change_mtu = ip6ip6_tnl_change_mtu;

        dev->type = ARPHRD_TUNNEL6;
        dev->hard_header_len = LL_MAX_HEADER + sizeof (struct ipv6hdr);
        dev->mtu = ETH_DATA_LEN - sizeof (struct ipv6hdr);
        dev->flags |= IFF_NOARP;
        dev->addr_len = sizeof(struct in6_addr);
}


/**
 * ip6ip6_tnl_dev_init_gen - general initializer for all tunnel devices
 *   @dev: virtual device associated with tunnel
 **/

static inline void
ip6ip6_tnl_dev_init_gen(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        t->fl.proto = IPPROTO_IPV6;
        t->dev = dev;
        strcpy(t->parms.name, dev->name);
}

/**
 * ip6ip6_tnl_dev_init - initializer for all non fallback tunnel devices
 *   @dev: virtual device associated with tunnel
 **/

static int
ip6ip6_tnl_dev_init(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        ip6ip6_tnl_dev_init_gen(dev);
        ip6ip6_tnl_link_config(t);
        return 0;
}

/**
 * ip6ip6_fb_tnl_dev_init - initializer for fallback tunnel device
 *   @dev: fallback device
 *
 * Return: 0
 **/

static int 
ip6ip6_fb_tnl_dev_init(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        ip6ip6_tnl_dev_init_gen(dev);
        dev_hold(dev);
        tnls_wc[0] = t;
        return 0;
}

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

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

static int __init ip6_tunnel_init(void)
{
        int  err;

        if (xfrm6_tunnel_register(&ip6ip6_handler)) {
                printk(KERN_ERR "ip6ip6 init: can't register tunnel\n");
                return -EAGAIN;
        }
        ip6ip6_fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6tnl0",
                                         ip6ip6_tnl_dev_setup);

        if (!ip6ip6_fb_tnl_dev) {
                err = -ENOMEM;
                goto fail;
        }
        ip6ip6_fb_tnl_dev->init = ip6ip6_fb_tnl_dev_init;

        if ((err = register_netdev(ip6ip6_fb_tnl_dev))) {
                free_netdev(ip6ip6_fb_tnl_dev);
                goto fail;
        }
        return 0;
fail:
        xfrm6_tunnel_deregister(&ip6ip6_handler);
        return err;
}

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

static void __exit ip6_tunnel_cleanup(void)
{
        if (xfrm6_tunnel_deregister(&ip6ip6_handler))
                printk(KERN_INFO "ip6ip6 close: can't deregister tunnel\n");

        unregister_netdev(ip6ip6_fb_tnl_dev);
}

module_init(ip6_tunnel_init);
module_exit(ip6_tunnel_cleanup);