sit.c

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/*
 *  IPv6 over IPv4 tunnel device - Simple Internet Transition (SIT)
 *  Linux INET6 implementation
 *
 *  Authors:
 *  Pedro Roque     <[email protected]>
 *  Alexey Kuznetsov    <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 *  Changes:
 * Roger Venning <[email protected]>:   6to4 support
 * Nate Thompson <[email protected]>:     6to4 support
 * Fred Templin <[email protected]>:    isatap support
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <linux/init.h>
#include <linux/netfilter_ipv4.h>
#include <linux/if_ether.h>

#include <net/sock.h>
#include <net/snmp.h>

#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#include <net/ndisc.h>
#include <net/addrconf.h>
#include <net/ip.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/ipip.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/dsfield.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

/*
   This version of net/ipv6/sit.c is cloned of net/ipv4/ip_gre.c

   For comments look at net/ipv4/ip_gre.c --ANK
 */

#define HASH_SIZE  16
#define HASH(addr) (((__force u32)addr^((__force u32)addr>>4))&0xF)

static int ipip6_tunnel_init(struct net_device *dev);
static void ipip6_tunnel_setup(struct net_device *dev);
static void ipip6_dev_free(struct net_device *dev);

static int sit_net_id __read_mostly;
struct sit_net {
    struct ip_tunnel __rcu *tunnels_r_l[HASH_SIZE];
    struct ip_tunnel __rcu *tunnels_r[HASH_SIZE];
    struct ip_tunnel __rcu *tunnels_l[HASH_SIZE];
    struct ip_tunnel __rcu *tunnels_wc[1];
    struct ip_tunnel __rcu **tunnels[4];

    struct net_device *fb_tunnel_dev;
};

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

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

/* often modified stats are per cpu, other are shared (netdev->stats) */
struct pcpu_tstats {
    u64 rx_packets;
    u64 rx_bytes;
    u64 tx_packets;
    u64 tx_bytes;
    struct u64_stats_sync   syncp;
};

static struct rtnl_link_stats64 *ipip6_get_stats64(struct net_device *dev,
                           struct rtnl_link_stats64 *tot)
{
    int i;

    for_each_possible_cpu(i) {
        const struct pcpu_tstats *tstats = per_cpu_ptr(dev->tstats, i);
        u64 rx_packets, rx_bytes, tx_packets, tx_bytes;
        unsigned int start;

        do {
            start = u64_stats_fetch_begin_bh(&tstats->syncp);
            rx_packets = tstats->rx_packets;
            tx_packets = tstats->tx_packets;
            rx_bytes = tstats->rx_bytes;
            tx_bytes = tstats->tx_bytes;
        } while (u64_stats_fetch_retry_bh(&tstats->syncp, start));

        tot->rx_packets += rx_packets;
        tot->tx_packets += tx_packets;
        tot->rx_bytes   += rx_bytes;
        tot->tx_bytes   += tx_bytes;
    }

    tot->rx_errors = dev->stats.rx_errors;
    tot->tx_fifo_errors = dev->stats.tx_fifo_errors;
    tot->tx_carrier_errors = dev->stats.tx_carrier_errors;
    tot->tx_dropped = dev->stats.tx_dropped;
    tot->tx_aborted_errors = dev->stats.tx_aborted_errors;
    tot->tx_errors = dev->stats.tx_errors;

    return tot;
}

/*
 * Must be invoked with rcu_read_lock
 */
static struct ip_tunnel *ipip6_tunnel_lookup(struct net *net,
        struct net_device *dev, __be32 remote, __be32 local)
{
    unsigned int h0 = HASH(remote);
    unsigned int h1 = HASH(local);
    struct ip_tunnel *t;
    struct sit_net *sitn = net_generic(net, sit_net_id);

    for_each_ip_tunnel_rcu(sitn->tunnels_r_l[h0 ^ h1]) {
        if (local == t->parms.iph.saddr &&
            remote == t->parms.iph.daddr &&
            (!dev || !t->parms.link || dev->iflink == t->parms.link) &&
            (t->dev->flags & IFF_UP))
            return t;
    }
    for_each_ip_tunnel_rcu(sitn->tunnels_r[h0]) {
        if (remote == t->parms.iph.daddr &&
            (!dev || !t->parms.link || dev->iflink == t->parms.link) &&
            (t->dev->flags & IFF_UP))
            return t;
    }
    for_each_ip_tunnel_rcu(sitn->tunnels_l[h1]) {
        if (local == t->parms.iph.saddr &&
            (!dev || !t->parms.link || dev->iflink == t->parms.link) &&
            (t->dev->flags & IFF_UP))
            return t;
    }
    t = rcu_dereference(sitn->tunnels_wc[0]);
    if ((t != NULL) && (t->dev->flags & IFF_UP))
        return t;
    return NULL;
}

static struct ip_tunnel __rcu **__ipip6_bucket(struct sit_net *sitn,
        struct ip_tunnel_parm *parms)
{
    __be32 remote = parms->iph.daddr;
    __be32 local = parms->iph.saddr;
    unsigned int h = 0;
    int prio = 0;

    if (remote) {
        prio |= 2;
        h ^= HASH(remote);
    }
    if (local) {
        prio |= 1;
        h ^= HASH(local);
    }
    return &sitn->tunnels[prio][h];
}

static inline struct ip_tunnel __rcu **ipip6_bucket(struct sit_net *sitn,
        struct ip_tunnel *t)
{
    return __ipip6_bucket(sitn, &t->parms);
}

static void ipip6_tunnel_unlink(struct sit_net *sitn, struct ip_tunnel *t)
{
    struct ip_tunnel __rcu **tp;
    struct ip_tunnel *iter;

    for (tp = ipip6_bucket(sitn, t);
         (iter = rtnl_dereference(*tp)) != NULL;
         tp = &iter->next) {
        if (t == iter) {
            rcu_assign_pointer(*tp, t->next);
            break;
        }
    }
}

static void ipip6_tunnel_link(struct sit_net *sitn, struct ip_tunnel *t)
{
    struct ip_tunnel __rcu **tp = ipip6_bucket(sitn, t);

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

static void ipip6_tunnel_clone_6rd(struct net_device *dev, struct sit_net *sitn)
{
#ifdef CONFIG_IPV6_SIT_6RD
    struct ip_tunnel *t = netdev_priv(dev);

    if (t->dev == sitn->fb_tunnel_dev) {
        ipv6_addr_set(&t->ip6rd.prefix, htonl(0x20020000), 0, 0, 0);
        t->ip6rd.relay_prefix = 0;
        t->ip6rd.prefixlen = 16;
        t->ip6rd.relay_prefixlen = 0;
    } else {
        struct ip_tunnel *t0 = netdev_priv(sitn->fb_tunnel_dev);
        memcpy(&t->ip6rd, &t0->ip6rd, sizeof(t->ip6rd));
    }
#endif
}

static struct ip_tunnel *ipip6_tunnel_locate(struct net *net,
        struct ip_tunnel_parm *parms, int create)
{
    __be32 remote = parms->iph.daddr;
    __be32 local = parms->iph.saddr;
    struct ip_tunnel *t, *nt;
    struct ip_tunnel __rcu **tp;
    struct net_device *dev;
    char name[IFNAMSIZ];
    struct sit_net *sitn = net_generic(net, sit_net_id);

    for (tp = __ipip6_bucket(sitn, parms);
        (t = rtnl_dereference(*tp)) != NULL;
         tp = &t->next) {
        if (local == t->parms.iph.saddr &&
            remote == t->parms.iph.daddr &&
            parms->link == t->parms.link) {
            if (create)
                return NULL;
            else
                return t;
        }
    }
    if (!create)
        goto failed;

    if (parms->name[0])
        strlcpy(name, parms->name, IFNAMSIZ);
    else
        strcpy(name, "sit%d");

    dev = alloc_netdev(sizeof(*t), name, ipip6_tunnel_setup);
    if (dev == NULL)
        return NULL;

    dev_net_set(dev, net);

    nt = netdev_priv(dev);

    nt->parms = *parms;
    if (ipip6_tunnel_init(dev) < 0)
        goto failed_free;
    ipip6_tunnel_clone_6rd(dev, sitn);

    if (parms->i_flags & SIT_ISATAP)
        dev->priv_flags |= IFF_ISATAP;

    if (register_netdevice(dev) < 0)
        goto failed_free;

    strcpy(nt->parms.name, dev->name);

    dev_hold(dev);

    ipip6_tunnel_link(sitn, nt);
    return nt;

failed_free:
    ipip6_dev_free(dev);
failed:
    return NULL;
}

#define for_each_prl_rcu(start)         \
    for (prl = rcu_dereference(start);  \
         prl;               \
         prl = rcu_dereference(prl->next))

static struct ip_tunnel_prl_entry *
__ipip6_tunnel_locate_prl(struct ip_tunnel *t, __be32 addr)
{
    struct ip_tunnel_prl_entry *prl;

    for_each_prl_rcu(t->prl)
        if (prl->addr == addr)
            break;
    return prl;

}

static int ipip6_tunnel_get_prl(struct ip_tunnel *t,
                struct ip_tunnel_prl __user *a)
{
    struct ip_tunnel_prl kprl, *kp;
    struct ip_tunnel_prl_entry *prl;
    unsigned int cmax, c = 0, ca, len;
    int ret = 0;

    if (copy_from_user(&kprl, a, sizeof(kprl)))
        return -EFAULT;
    cmax = kprl.datalen / sizeof(kprl);
    if (cmax > 1 && kprl.addr != htonl(INADDR_ANY))
        cmax = 1;

    /* For simple GET or for root users,
     * we try harder to allocate.
     */
    kp = (cmax <= 1 || capable(CAP_NET_ADMIN)) ?
        kcalloc(cmax, sizeof(*kp), GFP_KERNEL) :
        NULL;

    rcu_read_lock();

    ca = t->prl_count < cmax ? t->prl_count : cmax;

    if (!kp) {
        /* We don't try hard to allocate much memory for
         * non-root users.
         * For root users, retry allocating enough memory for
         * the answer.
         */
        kp = kcalloc(ca, sizeof(*kp), GFP_ATOMIC);
        if (!kp) {
            ret = -ENOMEM;
            goto out;
        }
    }

    c = 0;
    for_each_prl_rcu(t->prl) {
        if (c >= cmax)
            break;
        if (kprl.addr != htonl(INADDR_ANY) && prl->addr != kprl.addr)
            continue;
        kp[c].addr = prl->addr;
        kp[c].flags = prl->flags;
        c++;
        if (kprl.addr != htonl(INADDR_ANY))
            break;
    }
out:
    rcu_read_unlock();

    len = sizeof(*kp) * c;
    ret = 0;
    if ((len && copy_to_user(a + 1, kp, len)) || put_user(len, &a->datalen))
        ret = -EFAULT;

    kfree(kp);

    return ret;
}

static int
ipip6_tunnel_add_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a, int chg)
{
    struct ip_tunnel_prl_entry *p;
    int err = 0;

    if (a->addr == htonl(INADDR_ANY))
        return -EINVAL;

    ASSERT_RTNL();

    for (p = rtnl_dereference(t->prl); p; p = rtnl_dereference(p->next)) {
        if (p->addr == a->addr) {
            if (chg) {
                p->flags = a->flags;
                goto out;
            }
            err = -EEXIST;
            goto out;
        }
    }

    if (chg) {
        err = -ENXIO;
        goto out;
    }

    p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_KERNEL);
    if (!p) {
        err = -ENOBUFS;
        goto out;
    }

    p->next = t->prl;
    p->addr = a->addr;
    p->flags = a->flags;
    t->prl_count++;
    rcu_assign_pointer(t->prl, p);
out:
    return err;
}

static void prl_list_destroy_rcu(struct rcu_head *head)
{
    struct ip_tunnel_prl_entry *p, *n;

    p = container_of(head, struct ip_tunnel_prl_entry, rcu_head);
    do {
        n = rcu_dereference_protected(p->next, 1);
        kfree(p);
        p = n;
    } while (p);
}

static int
ipip6_tunnel_del_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a)
{
    struct ip_tunnel_prl_entry *x;
    struct ip_tunnel_prl_entry __rcu **p;
    int err = 0;

    ASSERT_RTNL();

    if (a && a->addr != htonl(INADDR_ANY)) {
        for (p = &t->prl;
             (x = rtnl_dereference(*p)) != NULL;
             p = &x->next) {
            if (x->addr == a->addr) {
                *p = x->next;
                kfree_rcu(x, rcu_head);
                t->prl_count--;
                goto out;
            }
        }
        err = -ENXIO;
    } else {
        x = rtnl_dereference(t->prl);
        if (x) {
            t->prl_count = 0;
            call_rcu(&x->rcu_head, prl_list_destroy_rcu);
            t->prl = NULL;
        }
    }
out:
    return err;
}

static int
isatap_chksrc(struct sk_buff *skb, const struct iphdr *iph, struct ip_tunnel *t)
{
    struct ip_tunnel_prl_entry *p;
    int ok = 1;

    rcu_read_lock();
    p = __ipip6_tunnel_locate_prl(t, iph->saddr);
    if (p) {
        if (p->flags & PRL_DEFAULT)
            skb->ndisc_nodetype = NDISC_NODETYPE_DEFAULT;
        else
            skb->ndisc_nodetype = NDISC_NODETYPE_NODEFAULT;
    } else {
        const struct in6_addr *addr6 = &ipv6_hdr(skb)->saddr;

        if (ipv6_addr_is_isatap(addr6) &&
            (addr6->s6_addr32[3] == iph->saddr) &&
            ipv6_chk_prefix(addr6, t->dev))
            skb->ndisc_nodetype = NDISC_NODETYPE_HOST;
        else
            ok = 0;
    }
    rcu_read_unlock();
    return ok;
}

static void ipip6_tunnel_uninit(struct net_device *dev)
{
    struct net *net = dev_net(dev);
    struct sit_net *sitn = net_generic(net, sit_net_id);

    if (dev == sitn->fb_tunnel_dev) {
        RCU_INIT_POINTER(sitn->tunnels_wc[0], NULL);
    } else {
        ipip6_tunnel_unlink(sitn, netdev_priv(dev));
        ipip6_tunnel_del_prl(netdev_priv(dev), NULL);
    }
    dev_put(dev);
}


static int ipip6_err(struct sk_buff *skb, u32 info)
{

/* All the routers (except for Linux) return only
   8 bytes of packet payload. It means, that precise relaying of
   ICMP in the real Internet is absolutely infeasible.
 */
    const struct iphdr *iph = (const struct iphdr *)skb->data;
    const int type = icmp_hdr(skb)->type;
    const int code = icmp_hdr(skb)->code;
    struct ip_tunnel *t;
    int err;

    switch (type) {
    default:
    case ICMP_PARAMETERPROB:
        return 0;

    case ICMP_DEST_UNREACH:
        switch (code) {
        case ICMP_SR_FAILED:
        case ICMP_PORT_UNREACH:
            /* Impossible event. */
            return 0;
        default:
            /* All others are translated to HOST_UNREACH.
               rfc2003 contains "deep thoughts" about NET_UNREACH,
               I believe they are just ether pollution. --ANK
             */
            break;
        }
        break;
    case ICMP_TIME_EXCEEDED:
        if (code != ICMP_EXC_TTL)
            return 0;
        break;
    case ICMP_REDIRECT:
        break;
    }

    err = -ENOENT;

    t = ipip6_tunnel_lookup(dev_net(skb->dev),
                skb->dev,
                iph->daddr,
                iph->saddr);
    if (t == NULL)
        goto out;

    if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
        ipv4_update_pmtu(skb, dev_net(skb->dev), info,
                 t->dev->ifindex, 0, IPPROTO_IPV6, 0);
        err = 0;
        goto out;
    }
    if (type == ICMP_REDIRECT) {
        ipv4_redirect(skb, dev_net(skb->dev), t->dev->ifindex, 0,
                  IPPROTO_IPV6, 0);
        err = 0;
        goto out;
    }

    if (t->parms.iph.daddr == 0)
        goto out;

    err = 0;
    if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
        goto out;

    if (time_before(jiffies, t->err_time + IPTUNNEL_ERR_TIMEO))
        t->err_count++;
    else
        t->err_count = 1;
    t->err_time = jiffies;
out:
    return err;
}

static inline void ipip6_ecn_decapsulate(const struct iphdr *iph, struct sk_buff *skb)
{
    if (INET_ECN_is_ce(iph->tos))
        IP6_ECN_set_ce(ipv6_hdr(skb));
}

static int ipip6_rcv(struct sk_buff *skb)
{
    const struct iphdr *iph;
    struct ip_tunnel *tunnel;

    if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
        goto out;

    iph = ip_hdr(skb);

    tunnel = ipip6_tunnel_lookup(dev_net(skb->dev), skb->dev,
                     iph->saddr, iph->daddr);
    if (tunnel != NULL) {
        struct pcpu_tstats *tstats;

        secpath_reset(skb);
        skb->mac_header = skb->network_header;
        skb_reset_network_header(skb);
        IPCB(skb)->flags = 0;
        skb->protocol = htons(ETH_P_IPV6);
        skb->pkt_type = PACKET_HOST;

        if ((tunnel->dev->priv_flags & IFF_ISATAP) &&
            !isatap_chksrc(skb, iph, tunnel)) {
            tunnel->dev->stats.rx_errors++;
            kfree_skb(skb);
            return 0;
        }

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

        __skb_tunnel_rx(skb, tunnel->dev);

        ipip6_ecn_decapsulate(iph, skb);

        netif_rx(skb);

        return 0;
    }

    /* no tunnel matched,  let upstream know, ipsec may handle it */
    return 1;
out:
    kfree_skb(skb);
    return 0;
}

/*
 * Returns the embedded IPv4 address if the IPv6 address
 * comes from 6rd / 6to4 (RFC 3056) addr space.
 */
static inline
__be32 try_6rd(const struct in6_addr *v6dst, struct ip_tunnel *tunnel)
{
    __be32 dst = 0;

#ifdef CONFIG_IPV6_SIT_6RD
    if (ipv6_prefix_equal(v6dst, &tunnel->ip6rd.prefix,
                  tunnel->ip6rd.prefixlen)) {
        unsigned int pbw0, pbi0;
        int pbi1;
        u32 d;

        pbw0 = tunnel->ip6rd.prefixlen >> 5;
        pbi0 = tunnel->ip6rd.prefixlen & 0x1f;

        d = (ntohl(v6dst->s6_addr32[pbw0]) << pbi0) >>
            tunnel->ip6rd.relay_prefixlen;

        pbi1 = pbi0 - tunnel->ip6rd.relay_prefixlen;
        if (pbi1 > 0)
            d |= ntohl(v6dst->s6_addr32[pbw0 + 1]) >>
                 (32 - pbi1);

        dst = tunnel->ip6rd.relay_prefix | htonl(d);
    }
#else
    if (v6dst->s6_addr16[0] == htons(0x2002)) {
        /* 6to4 v6 addr has 16 bits prefix, 32 v4addr, 16 SLA, ... */
        memcpy(&dst, &v6dst->s6_addr16[1], 4);
    }
#endif
    return dst;
}

/*
 *  This function assumes it is being called from dev_queue_xmit()
 *  and that skb is filled properly by that function.
 */

static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
                     struct net_device *dev)
{
    struct ip_tunnel *tunnel = netdev_priv(dev);
    struct pcpu_tstats *tstats;
    const struct iphdr  *tiph = &tunnel->parms.iph;
    const struct ipv6hdr *iph6 = ipv6_hdr(skb);
    u8     tos = tunnel->parms.iph.tos;
    __be16 df = tiph->frag_off;
    struct rtable *rt;              /* Route to the other host */
    struct net_device *tdev;        /* Device to other host */
    struct iphdr  *iph;         /* Our new IP header */
    unsigned int max_headroom;      /* The extra header space needed */
    __be32 dst = tiph->daddr;
    struct flowi4 fl4;
    int    mtu;
    const struct in6_addr *addr6;
    int addr_type;

    if (skb->protocol != htons(ETH_P_IPV6))
        goto tx_error;

    if (tos == 1)
        tos = ipv6_get_dsfield(iph6);

    /* ISATAP (RFC4214) - must come before 6to4 */
    if (dev->priv_flags & IFF_ISATAP) {
        struct neighbour *neigh = NULL;
        bool do_tx_error = false;

        if (skb_dst(skb))
            neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);

        if (neigh == NULL) {
            net_dbg_ratelimited("sit: nexthop == NULL\n");
            goto tx_error;
        }

        addr6 = (const struct in6_addr *)&neigh->primary_key;
        addr_type = ipv6_addr_type(addr6);

        if ((addr_type & IPV6_ADDR_UNICAST) &&
             ipv6_addr_is_isatap(addr6))
            dst = addr6->s6_addr32[3];
        else
            do_tx_error = true;

        neigh_release(neigh);
        if (do_tx_error)
            goto tx_error;
    }

    if (!dst)
        dst = try_6rd(&iph6->daddr, tunnel);

    if (!dst) {
        struct neighbour *neigh = NULL;
        bool do_tx_error = false;

        if (skb_dst(skb))
            neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);

        if (neigh == NULL) {
            net_dbg_ratelimited("sit: nexthop == NULL\n");
            goto tx_error;
        }

        addr6 = (const struct in6_addr *)&neigh->primary_key;
        addr_type = ipv6_addr_type(addr6);

        if (addr_type == IPV6_ADDR_ANY) {
            addr6 = &ipv6_hdr(skb)->daddr;
            addr_type = ipv6_addr_type(addr6);
        }

        if ((addr_type & IPV6_ADDR_COMPATv4) != 0)
            dst = addr6->s6_addr32[3];
        else
            do_tx_error = true;

        neigh_release(neigh);
        if (do_tx_error)
            goto tx_error;
    }

    rt = ip_route_output_ports(dev_net(dev), &fl4, NULL,
                   dst, tiph->saddr,
                   0, 0,
                   IPPROTO_IPV6, RT_TOS(tos),
                   tunnel->parms.link);
    if (IS_ERR(rt)) {
        dev->stats.tx_carrier_errors++;
        goto tx_error_icmp;
    }
    if (rt->rt_type != RTN_UNICAST) {
        ip_rt_put(rt);
        dev->stats.tx_carrier_errors++;
        goto tx_error_icmp;
    }
    tdev = rt->dst.dev;

    if (tdev == dev) {
        ip_rt_put(rt);
        dev->stats.collisions++;
        goto tx_error;
    }

    if (df) {
        mtu = dst_mtu(&rt->dst) - sizeof(struct iphdr);

        if (mtu < 68) {
            dev->stats.collisions++;
            ip_rt_put(rt);
            goto tx_error;
        }

        if (mtu < IPV6_MIN_MTU) {
            mtu = IPV6_MIN_MTU;
            df = 0;
        }

        if (tunnel->parms.iph.daddr && skb_dst(skb))
            skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);

        if (skb->len > mtu) {
            icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
            ip_rt_put(rt);
            goto tx_error;
        }
    }

    if (tunnel->err_count > 0) {
        if (time_before(jiffies,
                tunnel->err_time + IPTUNNEL_ERR_TIMEO)) {
            tunnel->err_count--;
            dst_link_failure(skb);
        } else
            tunnel->err_count = 0;
    }

    /*
     * Okay, now see if we can stuff it in the buffer as-is.
     */
    max_headroom = LL_RESERVED_SPACE(tdev)+sizeof(struct iphdr);

    if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
        (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {
        struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
        if (!new_skb) {
            ip_rt_put(rt);
            dev->stats.tx_dropped++;
            dev_kfree_skb(skb);
            return NETDEV_TX_OK;
        }
        if (skb->sk)
            skb_set_owner_w(new_skb, skb->sk);
        dev_kfree_skb(skb);
        skb = new_skb;
        iph6 = ipv6_hdr(skb);
    }

    skb->transport_header = skb->network_header;
    skb_push(skb, sizeof(struct iphdr));
    skb_reset_network_header(skb);
    memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
    IPCB(skb)->flags = 0;
    skb_dst_drop(skb);
    skb_dst_set(skb, &rt->dst);

    /*
     *  Push down and install the IPIP header.
     */

    iph             =   ip_hdr(skb);
    iph->version        =   4;
    iph->ihl        =   sizeof(struct iphdr)>>2;
    iph->frag_off       =   df;
    iph->protocol       =   IPPROTO_IPV6;
    iph->tos        =   INET_ECN_encapsulate(tos, ipv6_get_dsfield(iph6));
    iph->daddr      =   fl4.daddr;
    iph->saddr      =   fl4.saddr;

    if ((iph->ttl = tiph->ttl) == 0)
        iph->ttl    =   iph6->hop_limit;

    nf_reset(skb);
    tstats = this_cpu_ptr(dev->tstats);
    __IPTUNNEL_XMIT(tstats, &dev->stats);
    return NETDEV_TX_OK;

tx_error_icmp:
    dst_link_failure(skb);
tx_error:
    dev->stats.tx_errors++;
    dev_kfree_skb(skb);
    return NETDEV_TX_OK;
}

static void ipip6_tunnel_bind_dev(struct net_device *dev)
{
    struct net_device *tdev = NULL;
    struct ip_tunnel *tunnel;
    const struct iphdr *iph;
    struct flowi4 fl4;

    tunnel = netdev_priv(dev);
    iph = &tunnel->parms.iph;

    if (iph->daddr) {
        struct rtable *rt = ip_route_output_ports(dev_net(dev), &fl4, NULL,
                              iph->daddr, iph->saddr,
                              0, 0,
                              IPPROTO_IPV6,
                              RT_TOS(iph->tos),
                              tunnel->parms.link);

        if (!IS_ERR(rt)) {
            tdev = rt->dst.dev;
            ip_rt_put(rt);
        }
        dev->flags |= IFF_POINTOPOINT;
    }

    if (!tdev && tunnel->parms.link)
        tdev = __dev_get_by_index(dev_net(dev), tunnel->parms.link);

    if (tdev) {
        dev->hard_header_len = tdev->hard_header_len + sizeof(struct iphdr);
        dev->mtu = tdev->mtu - sizeof(struct iphdr);
        if (dev->mtu < IPV6_MIN_MTU)
            dev->mtu = IPV6_MIN_MTU;
    }
    dev->iflink = tunnel->parms.link;
}

static int
ipip6_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
{
    int err = 0;
    struct ip_tunnel_parm p;
    struct ip_tunnel_prl prl;
    struct ip_tunnel *t;
    struct net *net = dev_net(dev);
    struct sit_net *sitn = net_generic(net, sit_net_id);
#ifdef CONFIG_IPV6_SIT_6RD
    struct ip_tunnel_6rd ip6rd;
#endif

    switch (cmd) {
    case SIOCGETTUNNEL:
#ifdef CONFIG_IPV6_SIT_6RD
    case SIOCGET6RD:
#endif
        t = NULL;
        if (dev == sitn->fb_tunnel_dev) {
            if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
                err = -EFAULT;
                break;
            }
            t = ipip6_tunnel_locate(net, &p, 0);
        }
        if (t == NULL)
            t = netdev_priv(dev);

        err = -EFAULT;
        if (cmd == SIOCGETTUNNEL) {
            memcpy(&p, &t->parms, sizeof(p));
            if (copy_to_user(ifr->ifr_ifru.ifru_data, &p,
                     sizeof(p)))
                goto done;
#ifdef CONFIG_IPV6_SIT_6RD
        } else {
            ip6rd.prefix = t->ip6rd.prefix;
            ip6rd.relay_prefix = t->ip6rd.relay_prefix;
            ip6rd.prefixlen = t->ip6rd.prefixlen;
            ip6rd.relay_prefixlen = t->ip6rd.relay_prefixlen;
            if (copy_to_user(ifr->ifr_ifru.ifru_data, &ip6rd,
                     sizeof(ip6rd)))
                goto done;
#endif
        }
        err = 0;
        break;

    case SIOCADDTUNNEL:
    case SIOCCHGTUNNEL:
        err = -EPERM;
        if (!capable(CAP_NET_ADMIN))
            goto done;

        err = -EFAULT;
        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
            goto done;

        err = -EINVAL;
        if (p.iph.version != 4 || p.iph.protocol != IPPROTO_IPV6 ||
            p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)))
            goto done;
        if (p.iph.ttl)
            p.iph.frag_off |= htons(IP_DF);

        t = ipip6_tunnel_locate(net, &p, cmd == SIOCADDTUNNEL);

        if (dev != sitn->fb_tunnel_dev && cmd == SIOCCHGTUNNEL) {
            if (t != NULL) {
                if (t->dev != dev) {
                    err = -EEXIST;
                    break;
                }
            } else {
                if (((dev->flags&IFF_POINTOPOINT) && !p.iph.daddr) ||
                    (!(dev->flags&IFF_POINTOPOINT) && p.iph.daddr)) {
                    err = -EINVAL;
                    break;
                }
                t = netdev_priv(dev);
                ipip6_tunnel_unlink(sitn, t);
                synchronize_net();
                t->parms.iph.saddr = p.iph.saddr;
                t->parms.iph.daddr = p.iph.daddr;
                memcpy(dev->dev_addr, &p.iph.saddr, 4);
                memcpy(dev->broadcast, &p.iph.daddr, 4);
                ipip6_tunnel_link(sitn, t);
                netdev_state_change(dev);
            }
        }

        if (t) {
            err = 0;
            if (cmd == SIOCCHGTUNNEL) {
                t->parms.iph.ttl = p.iph.ttl;
                t->parms.iph.tos = p.iph.tos;
                if (t->parms.link != p.link) {
                    t->parms.link = p.link;
                    ipip6_tunnel_bind_dev(dev);
                    netdev_state_change(dev);
                }
            }
            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))
            goto done;

        if (dev == sitn->fb_tunnel_dev) {
            err = -EFAULT;
            if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
                goto done;
            err = -ENOENT;
            if ((t = ipip6_tunnel_locate(net, &p, 0)) == NULL)
                goto done;
            err = -EPERM;
            if (t == netdev_priv(sitn->fb_tunnel_dev))
                goto done;
            dev = t->dev;
        }
        unregister_netdevice(dev);
        err = 0;
        break;

    case SIOCGETPRL:
        err = -EINVAL;
        if (dev == sitn->fb_tunnel_dev)
            goto done;
        err = -ENOENT;
        if (!(t = netdev_priv(dev)))
            goto done;
        err = ipip6_tunnel_get_prl(t, ifr->ifr_ifru.ifru_data);
        break;

    case SIOCADDPRL:
    case SIOCDELPRL:
    case SIOCCHGPRL:
        err = -EPERM;
        if (!capable(CAP_NET_ADMIN))
            goto done;
        err = -EINVAL;
        if (dev == sitn->fb_tunnel_dev)
            goto done;
        err = -EFAULT;
        if (copy_from_user(&prl, ifr->ifr_ifru.ifru_data, sizeof(prl)))
            goto done;
        err = -ENOENT;
        if (!(t = netdev_priv(dev)))
            goto done;

        switch (cmd) {
        case SIOCDELPRL:
            err = ipip6_tunnel_del_prl(t, &prl);
            break;
        case SIOCADDPRL:
        case SIOCCHGPRL:
            err = ipip6_tunnel_add_prl(t, &prl, cmd == SIOCCHGPRL);
            break;
        }
        netdev_state_change(dev);
        break;

#ifdef CONFIG_IPV6_SIT_6RD
    case SIOCADD6RD:
    case SIOCCHG6RD:
    case SIOCDEL6RD:
        err = -EPERM;
        if (!capable(CAP_NET_ADMIN))
            goto done;

        err = -EFAULT;
        if (copy_from_user(&ip6rd, ifr->ifr_ifru.ifru_data,
                   sizeof(ip6rd)))
            goto done;

        t = netdev_priv(dev);

        if (cmd != SIOCDEL6RD) {
            struct in6_addr prefix;
            __be32 relay_prefix;

            err = -EINVAL;
            if (ip6rd.relay_prefixlen > 32 ||
                ip6rd.prefixlen + (32 - ip6rd.relay_prefixlen) > 64)
                goto done;

            ipv6_addr_prefix(&prefix, &ip6rd.prefix,
                     ip6rd.prefixlen);
            if (!ipv6_addr_equal(&prefix, &ip6rd.prefix))
                goto done;
            if (ip6rd.relay_prefixlen)
                relay_prefix = ip6rd.relay_prefix &
                           htonl(0xffffffffUL <<
                             (32 - ip6rd.relay_prefixlen));
            else
                relay_prefix = 0;
            if (relay_prefix != ip6rd.relay_prefix)
                goto done;

            t->ip6rd.prefix = prefix;
            t->ip6rd.relay_prefix = relay_prefix;
            t->ip6rd.prefixlen = ip6rd.prefixlen;
            t->ip6rd.relay_prefixlen = ip6rd.relay_prefixlen;
        } else
            ipip6_tunnel_clone_6rd(dev, sitn);

        err = 0;
        break;
#endif

    default:
        err = -EINVAL;
    }

done:
    return err;
}

static int ipip6_tunnel_change_mtu(struct net_device *dev, int new_mtu)
{
    if (new_mtu < IPV6_MIN_MTU || new_mtu > 0xFFF8 - sizeof(struct iphdr))
        return -EINVAL;
    dev->mtu = new_mtu;
    return 0;
}

static const struct net_device_ops ipip6_netdev_ops = {
    .ndo_uninit = ipip6_tunnel_uninit,
    .ndo_start_xmit = ipip6_tunnel_xmit,
    .ndo_do_ioctl   = ipip6_tunnel_ioctl,
    .ndo_change_mtu = ipip6_tunnel_change_mtu,
    .ndo_get_stats64= ipip6_get_stats64,
};

static void ipip6_dev_free(struct net_device *dev)
{
    free_percpu(dev->tstats);
    free_netdev(dev);
}

static void ipip6_tunnel_setup(struct net_device *dev)
{
    dev->netdev_ops     = &ipip6_netdev_ops;
    dev->destructor     = ipip6_dev_free;

    dev->type       = ARPHRD_SIT;
    dev->hard_header_len    = LL_MAX_HEADER + sizeof(struct iphdr);
    dev->mtu        = ETH_DATA_LEN - sizeof(struct iphdr);
    dev->flags      = IFF_NOARP;
    dev->priv_flags        &= ~IFF_XMIT_DST_RELEASE;
    dev->iflink     = 0;
    dev->addr_len       = 4;
    dev->features       |= NETIF_F_NETNS_LOCAL;
    dev->features       |= NETIF_F_LLTX;
}

static int ipip6_tunnel_init(struct net_device *dev)
{
    struct ip_tunnel *tunnel = netdev_priv(dev);

    tunnel->dev = dev;

    memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
    memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);

    ipip6_tunnel_bind_dev(dev);
    dev->tstats = alloc_percpu(struct pcpu_tstats);
    if (!dev->tstats)
        return -ENOMEM;

    return 0;
}

static int __net_init ipip6_fb_tunnel_init(struct net_device *dev)
{
    struct ip_tunnel *tunnel = netdev_priv(dev);
    struct iphdr *iph = &tunnel->parms.iph;
    struct net *net = dev_net(dev);
    struct sit_net *sitn = net_generic(net, sit_net_id);

    tunnel->dev = dev;
    strcpy(tunnel->parms.name, dev->name);

    iph->version        = 4;
    iph->protocol       = IPPROTO_IPV6;
    iph->ihl        = 5;
    iph->ttl        = 64;

    dev->tstats = alloc_percpu(struct pcpu_tstats);
    if (!dev->tstats)
        return -ENOMEM;
    dev_hold(dev);
    rcu_assign_pointer(sitn->tunnels_wc[0], tunnel);
    return 0;
}

static struct xfrm_tunnel sit_handler __read_mostly = {
    .handler    =   ipip6_rcv,
    .err_handler    =   ipip6_err,
    .priority   =   1,
};

static void __net_exit sit_destroy_tunnels(struct sit_net *sitn, struct list_head *head)
{
    int prio;

    for (prio = 1; prio < 4; prio++) {
        int h;
        for (h = 0; h < HASH_SIZE; h++) {
            struct ip_tunnel *t;

            t = rtnl_dereference(sitn->tunnels[prio][h]);
            while (t != NULL) {
                unregister_netdevice_queue(t->dev, head);
                t = rtnl_dereference(t->next);
            }
        }
    }
}

static int __net_init sit_init_net(struct net *net)
{
    struct sit_net *sitn = net_generic(net, sit_net_id);
    struct ip_tunnel *t;
    int err;

    sitn->tunnels[0] = sitn->tunnels_wc;
    sitn->tunnels[1] = sitn->tunnels_l;
    sitn->tunnels[2] = sitn->tunnels_r;
    sitn->tunnels[3] = sitn->tunnels_r_l;

    sitn->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "sit0",
                       ipip6_tunnel_setup);
    if (!sitn->fb_tunnel_dev) {
        err = -ENOMEM;
        goto err_alloc_dev;
    }
    dev_net_set(sitn->fb_tunnel_dev, net);

    err = ipip6_fb_tunnel_init(sitn->fb_tunnel_dev);
    if (err)
        goto err_dev_free;

    ipip6_tunnel_clone_6rd(sitn->fb_tunnel_dev, sitn);

    if ((err = register_netdev(sitn->fb_tunnel_dev)))
        goto err_reg_dev;

    t = netdev_priv(sitn->fb_tunnel_dev);

    strcpy(t->parms.name, sitn->fb_tunnel_dev->name);
    return 0;

err_reg_dev:
    dev_put(sitn->fb_tunnel_dev);
err_dev_free:
    ipip6_dev_free(sitn->fb_tunnel_dev);
err_alloc_dev:
    return err;
}

static void __net_exit sit_exit_net(struct net *net)
{
    struct sit_net *sitn = net_generic(net, sit_net_id);
    LIST_HEAD(list);

    rtnl_lock();
    sit_destroy_tunnels(sitn, &list);
    unregister_netdevice_queue(sitn->fb_tunnel_dev, &list);
    unregister_netdevice_many(&list);
    rtnl_unlock();
}

static struct pernet_operations sit_net_ops = {
    .init = sit_init_net,
    .exit = sit_exit_net,
    .id   = &sit_net_id,
    .size = sizeof(struct sit_net),
};

static void __exit sit_cleanup(void)
{
    xfrm4_tunnel_deregister(&sit_handler, AF_INET6);

    unregister_pernet_device(&sit_net_ops);
    rcu_barrier(); /* Wait for completion of call_rcu()'s */
}

static int __init sit_init(void)
{
    int err;

    pr_info("IPv6 over IPv4 tunneling driver\n");

    err = register_pernet_device(&sit_net_ops);
    if (err < 0)
        return err;
    err = xfrm4_tunnel_register(&sit_handler, AF_INET6);
    if (err < 0) {
        unregister_pernet_device(&sit_net_ops);
        pr_info("%s: can't add protocol\n", __func__);
    }
    return err;
}

module_init(sit_init);
module_exit(sit_cleanup);
MODULE_LICENSE("GPL");
MODULE_ALIAS_NETDEV("sit0");