[SK_BUFF]: Introduce ip_hdr(), remove skb->nh.iph

[GitHub/LineageOS/android_kernel_motorola_exynos9610.git] / net / ipv6 / ip6_tunnel.c

/*
 *      IPv6 tunneling device
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Ville Nuorvala          <vnuorval@tcs.hut.fi>
 *      Yasuyuki Kozakai        <kozakai@linux-ipv6.org>
 *
 *      $Id$
 *
 *      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.
 *
 */

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

#include <net/icmp.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 tunneling device");
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 IPV6_TCLASS_SHIFT 20

#define HASH_SIZE  32

#define HASH(addr) ((__force u32)((addr)->s6_addr32[0] ^ (addr)->s6_addr32[1] ^ \
                     (addr)->s6_addr32[2] ^ (addr)->s6_addr32[3]) & \
                    (HASH_SIZE - 1))

static int ip6_fb_tnl_dev_init(struct net_device *dev);
static int ip6_tnl_dev_init(struct net_device *dev);
static void ip6_tnl_dev_setup(struct net_device *dev);

/* the IPv6 tunnel fallback device */
static struct net_device *ip6_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(ip6_tnl_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;
}

/**
 * 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
 **/

static struct ip6_tnl *
ip6_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;
}

/**
 * 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 **
ip6_tnl_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];
}

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

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

        t->next = *tp;
        write_lock_bh(&ip6_tnl_lock);
        *tp = t;
        write_unlock_bh(&ip6_tnl_lock);
}

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

static void
ip6_tnl_unlink(struct ip6_tnl *t)
{
        struct ip6_tnl **tp;

        for (tp = ip6_tnl_bucket(&t->parms); *tp; tp = &(*tp)->next) {
                if (t == *tp) {
                        write_lock_bh(&ip6_tnl_lock);
                        *tp = t->next;
                        write_unlock_bh(&ip6_tnl_lock);
                        break;
                }
        }
}

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

        t = netdev_priv(dev);
        dev->init = ip6_tnl_dev_init;
        t->parms = *p;

        if ((err = register_netdevice(dev)) < 0) {
                free_netdev(dev);
                goto failed;
        }
        dev_hold(dev);
        ip6_tnl_link(t);
        return t;
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 ip6_tnl_parm *p, int create)
{
        struct in6_addr *remote = &p->raddr;
        struct in6_addr *local = &p->laddr;
        struct ip6_tnl *t;

        for (t = *ip6_tnl_bucket(p); t; t = 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(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);

        if (dev == ip6_fb_tnl_dev) {
                write_lock_bh(&ip6_tnl_lock);
                tnls_wc[0] = NULL;
                write_unlock_bh(&ip6_tnl_lock);
        } else {
                ip6_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;
}

/**
 * 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,
            int *type, int *code, int *msg, __be32 *info, int offset)
{
        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(&ip6_tnl_lock);
        if ((t = ip6_tnl_lookup(&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:
                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:
                teli = 0;
                if ((*code) == ICMPV6_HDR_FIELD)
                        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;
                        }
                } else if (net_ratelimit()) {
                        printk(KERN_WARNING
                               "%s: Recipient unable to parse tunneled "
                               "packet!\n ", t->parms.name);
                }
                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;
        }

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

out:
        read_unlock(&ip6_tnl_lock);
        return err;
}

static int
ip4ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
           int type, int code, int offset, __u32 info)
{
        int rel_msg = 0;
        int rel_type = type;
        int rel_code = code;
        __u32 rel_info = info;
        int err;
        struct sk_buff *skb2;
        struct iphdr *eiph;
        struct flowi fl;
        struct rtable *rt;

        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;
        default:
                return 0;
        }

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

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

        dst_release(skb2->dst);
        skb2->dst = NULL;
        skb_pull(skb2, offset);
        skb_reset_network_header(skb2);
        eiph = ip_hdr(skb2);

        /* Try to guess incoming interface */
        memset(&fl, 0, sizeof(fl));
        fl.fl4_dst = eiph->saddr;
        fl.fl4_tos = RT_TOS(eiph->tos);
        fl.proto = IPPROTO_IPIP;
        if (ip_route_output_key(&rt, &fl))
                goto out;

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

        /* route "incoming" packet */
        if (rt->rt_flags & RTCF_LOCAL) {
                ip_rt_put(rt);
                rt = NULL;
                fl.fl4_dst = eiph->daddr;
                fl.fl4_src = eiph->saddr;
                fl.fl4_tos = eiph->tos;
                if (ip_route_output_key(&rt, &fl) ||
                    rt->u.dst.dev->type != ARPHRD_TUNNEL) {
                        ip_rt_put(rt);
                        goto out;
                }
        } else {
                ip_rt_put(rt);
                if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos,
                                   skb2->dev) ||
                    skb2->dst->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(skb2->dst))
                        goto out;

                skb2->dst->ops->update_pmtu(skb2->dst, rel_info);
                rel_info = htonl(rel_info);
        }

        icmp_send(skb2, rel_type, rel_code, rel_info);

out:
        kfree_skb(skb2);
        return 0;
}

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

                dst_release(skb2->dst);
                skb2->dst = NULL;
                skb_pull(skb2, offset);
                skb_reset_network_header(skb2);

                /* 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);
        }

        return 0;
}

static void ip4ip6_dscp_ecn_decapsulate(struct ip6_tnl *t,
                                        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);

        if (INET_ECN_is_ce(dsfield))
                IP_ECN_set_ce(ip_hdr(skb));
}

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

        if (INET_ECN_is_ce(ipv6_get_dsfield(ipv6h)))
                IP6_ECN_set_ce(skb->nh.ipv6h);
}

static inline int ip6_tnl_rcv_ctl(struct ip6_tnl *t)
{
        struct ip6_tnl_parm *p = &t->parms;
        int ret = 0;

        if (p->flags & IP6_TNL_F_CAP_RCV) {
                struct net_device *ldev = NULL;

                if (p->link)
                        ldev = dev_get_by_index(p->link);

                if ((ipv6_addr_is_multicast(&p->laddr) ||
                     likely(ipv6_chk_addr(&p->laddr, ldev, 0))) &&
                    likely(!ipv6_chk_addr(&p->raddr, NULL, 0)))
                        ret = 1;

                if (ldev)
                        dev_put(ldev);
        }
        return ret;
}

/**
 * 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,
                       void (*dscp_ecn_decapsulate)(struct ip6_tnl *t,
                                                    struct ipv6hdr *ipv6h,
                                                    struct sk_buff *skb))
{
        struct ipv6hdr *ipv6h;
        struct ip6_tnl *t;

        ipv6h = skb->nh.ipv6h;

        read_lock(&ip6_tnl_lock);

        if ((t = ip6_tnl_lookup(&ipv6h->saddr, &ipv6h->daddr)) != NULL) {
                if (t->parms.proto != ipproto && t->parms.proto != 0) {
                        read_unlock(&ip6_tnl_lock);
                        goto discard;
                }

                if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
                        read_unlock(&ip6_tnl_lock);
                        goto discard;
                }

                if (!ip6_tnl_rcv_ctl(t)) {
                        t->stat.rx_dropped++;
                        read_unlock(&ip6_tnl_lock);
                        goto discard;
                }
                secpath_reset(skb);
                skb->mac.raw = skb->nh.raw;
                skb_reset_network_header(skb);
                skb->protocol = htons(protocol);
                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;
                nf_reset(skb);

                dscp_ecn_decapsulate(t, ipv6h, skb);

                t->stat.rx_packets++;
                t->stat.rx_bytes += skb->len;
                netif_rx(skb);
                read_unlock(&ip6_tnl_lock);
                return 0;
        }
        read_unlock(&ip6_tnl_lock);
        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 int
ip6_tnl_addr_conflict(struct ip6_tnl *t, struct ipv6hdr *hdr)
{
        return ipv6_addr_equal(&t->parms.raddr, &hdr->saddr);
}

static inline int ip6_tnl_xmit_ctl(struct ip6_tnl *t)
{
        struct ip6_tnl_parm *p = &t->parms;
        int ret = 0;

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

                if (p->link)
                        ldev = dev_get_by_index(p->link);

                if (unlikely(!ipv6_chk_addr(&p->laddr, ldev, 0)))
                        printk(KERN_WARNING
                               "%s xmit: Local address not yet configured!\n",
                               p->name);
                else if (!ipv6_addr_is_multicast(&p->raddr) &&
                         unlikely(ipv6_chk_addr(&p->raddr, NULL, 0)))
                        printk(KERN_WARNING
                               "%s xmit: Routing loop! "
                               "Remote address found on this node!\n",
                               p->name);
                else
                        ret = 1;
                if (ldev)
                        dev_put(ldev);
        }
        return ret;
}
/**
 * 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 flowi *fl,
                         int encap_limit,
                         __u32 *pmtu)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct net_device_stats *stats = &t->stat;
        struct ipv6hdr *ipv6h = skb->nh.ipv6h;
        struct ipv6_tel_txoption opt;
        struct dst_entry *dst;
        struct net_device *tdev;
        int mtu;
        int max_headroom = sizeof(struct ipv6hdr);
        u8 proto;
        int err = -1;
        int pkt_len;

        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 (encap_limit >= 0) {
                max_headroom += 8;
                mtu -= 8;
        }
        if (mtu < IPV6_MIN_MTU)
                mtu = IPV6_MIN_MTU;
        if (skb->dst)
                skb->dst->ops->update_pmtu(skb->dst, 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_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;

        proto = fl->proto;
        if (encap_limit >= 0) {
                init_tel_txopt(&opt, encap_limit);
                ipv6_push_nfrag_opts(skb, &opt.ops, &proto, NULL);
        }
        skb_push(skb, sizeof(struct ipv6hdr));
        skb_reset_network_header(skb);
        ipv6h = skb->nh.ipv6h;
        *(__be32*)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 (net_xmit_eval(err) == 0) {
                stats->tx_bytes += pkt_len;
                stats->tx_packets++;
        } else {
                stats->tx_errors++;
                stats->tx_aborted_errors++;
        }
        ip6_tnl_dst_store(t, dst);
        return 0;
tx_err_link_failure:
        stats->tx_carrier_errors++;
        dst_link_failure(skb);
tx_err_dst_release:
        dst_release(dst);
        return err;
}

static inline int
ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct iphdr  *iph = ip_hdr(skb);
        int encap_limit = -1;
        struct flowi fl;
        __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(&fl, &t->fl, sizeof (fl));
        fl.proto = IPPROTO_IPIP;

        dsfield = ipv4_get_dsfield(iph);

        if ((t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS))
                fl.fl6_flowlabel |= ntohl(((__u32)iph->tos << IPV6_TCLASS_SHIFT)
                                          & IPV6_TCLASS_MASK);

        err = ip6_tnl_xmit2(skb, dev, dsfield, &fl, 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 = skb->nh.ipv6h;
        int encap_limit = -1;
        __u16 offset;
        struct flowi fl;
        __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 = parse_tlv_tnl_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, skb->dev);
                        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(&fl, &t->fl, sizeof (fl));
        fl.proto = IPPROTO_IPV6;

        dsfield = ipv6_get_dsfield(ipv6h);
        if ((t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS))
                fl.fl6_flowlabel |= (*(__be32 *) ipv6h & IPV6_TCLASS_MASK);
        if ((t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL))
                fl.fl6_flowlabel |= (*(__be32 *) ipv6h & IPV6_FLOWLABEL_MASK);

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

        return 0;
}

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

        if (t->recursion++) {
                t->stat.collisions++;
                goto tx_err;
        }

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

        if (ret < 0)
                goto tx_err;

        t->recursion--;
        return 0;

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;
        int ltype = ipv6_addr_type(&p->laddr);
        int rtype = ipv6_addr_type(&p->raddr);

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

        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)
                        p->flags |= IP6_TNL_F_CAP_XMIT;
                if (rtype&IPV6_ADDR_UNICAST)
                        p->flags |= IP6_TNL_F_CAP_RCV;
        }
}

static void ip6_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) {
                int strict = (ipv6_addr_type(&p->raddr) &
                              (IPV6_ADDR_MULTICAST|IPV6_ADDR_LINKLOCAL));

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

                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);
        }
}

/**
 * ip6_tnl_change - update the tunnel parameters
 *   @t: tunnel to be changed
 *   @p: tunnel configuration parameters
 *   @active: != 0 if tunnel is ready for use
 *
 * Description:
 *   ip6_tnl_change() updates the tunnel parameters
 **/

static int
ip6_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;
        t->parms.proto = p->proto;
        ip6_tnl_dst_reset(t);
        ip6_tnl_link_config(t);
        return 0;
}

/**
 * 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 *t = NULL;

        switch (cmd) {
        case SIOCGETTUNNEL:
                if (dev == ip6_fb_tnl_dev) {
                        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p))) {
                                err = -EFAULT;
                                break;
                        }
                        t = ip6_tnl_locate(&p, 0);
                }
                if (t == NULL)
                        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;
                if (!capable(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;
                t = ip6_tnl_locate(&p, cmd == SIOCADDTUNNEL);
                if (dev != ip6_fb_tnl_dev && cmd == SIOCCHGTUNNEL) {
                        if (t != NULL) {
                                if (t->dev != dev) {
                                        err = -EEXIST;
                                        break;
                                }
                        } else
                                t = netdev_priv(dev);

                        ip6_tnl_unlink(t);
                        err = ip6_tnl_change(t, &p);
                        ip6_tnl_link(t);
                        netdev_state_change(dev);
                }
                if (t) {
                        err = 0;
                        if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof (p)))
                                err = -EFAULT;

                } else
                        err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
                break;
        case SIOCDELTUNNEL:
                err = -EPERM;
                if (!capable(CAP_NET_ADMIN))
                        break;

                if (dev == ip6_fb_tnl_dev) {
                        err = -EFAULT;
                        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p)))
                                break;
                        err = -ENOENT;
                        if ((t = ip6_tnl_locate(&p, 0)) == NULL)
                                break;
                        err = -EPERM;
                        if (t->dev == ip6_fb_tnl_dev)
                                break;
                        dev = t->dev;
                }
                err = 0;
                unregister_netdevice(dev);
                break;
        default:
                err = -EINVAL;
        }
        return err;
}

/**
 * ip6_tnl_get_stats - return the stats for tunnel device
 *   @dev: virtual device associated with tunnel
 *
 * Return: stats for device
 **/

static struct net_device_stats *
ip6_tnl_get_stats(struct net_device *dev)
{
        return &(((struct ip6_tnl *)netdev_priv(dev))->stat);
}

/**
 * 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;
}

/**
 * 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)
{
        SET_MODULE_OWNER(dev);
        dev->uninit = ip6_tnl_dev_uninit;
        dev->destructor = free_netdev;
        dev->hard_start_xmit = ip6_tnl_xmit;
        dev->get_stats = ip6_tnl_get_stats;
        dev->do_ioctl = ip6_tnl_ioctl;
        dev->change_mtu = ip6_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);
}


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

static inline void
ip6_tnl_dev_init_gen(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        t->dev = dev;
        strcpy(t->parms.name, dev->name);
}

/**
 * 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);
        ip6_tnl_dev_init_gen(dev);
        ip6_tnl_link_config(t);
        return 0;
}

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

static int
ip6_fb_tnl_dev_init(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        ip6_tnl_dev_init_gen(dev);
        t->parms.proto = IPPROTO_IPV6;
        dev_hold(dev);
        tnls_wc[0] = t;
        return 0;
}

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

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(&ip4ip6_handler, AF_INET)) {
                printk(KERN_ERR "ip6_tunnel init: can't register ip4ip6\n");
                err = -EAGAIN;
                goto out;
        }

        if (xfrm6_tunnel_register(&ip6ip6_handler, AF_INET6)) {
                printk(KERN_ERR "ip6_tunnel init: can't register ip6ip6\n");
                err = -EAGAIN;
                goto unreg_ip4ip6;
        }
        ip6_fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6tnl0",
                                      ip6_tnl_dev_setup);

        if (!ip6_fb_tnl_dev) {
                err = -ENOMEM;
                goto fail;
        }
        ip6_fb_tnl_dev->init = ip6_fb_tnl_dev_init;

        if ((err = register_netdev(ip6_fb_tnl_dev))) {
                free_netdev(ip6_fb_tnl_dev);
                goto fail;
        }
        return 0;
fail:
        xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6);
unreg_ip4ip6:
        xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET);
out:
        return err;
}

static void __exit ip6_tnl_destroy_tunnels(void)
{
        int h;
        struct ip6_tnl *t;

        for (h = 0; h < HASH_SIZE; h++) {
                while ((t = tnls_r_l[h]) != NULL)
                        unregister_netdevice(t->dev);
        }

        t = tnls_wc[0];
        unregister_netdevice(t->dev);
}

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

static void __exit ip6_tunnel_cleanup(void)
{
        if (xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET))
                printk(KERN_INFO "ip6_tunnel close: can't deregister ip4ip6\n");

        if (xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6))
                printk(KERN_INFO "ip6_tunnel close: can't deregister ip6ip6\n");

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

module_init(ip6_tunnel_init);
module_exit(ip6_tunnel_cleanup);