/*
 *      IP multicast routing support for mrouted 3.6/3.8
 *
 *              (c) 1995 Alan Cox, <alan@lxorguk.ukuu.org.uk>
 *        Linux Consultancy and Custom Driver Development
 *
 *      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.
 *
 *      Fixes:
 *      Michael Chastain        :       Incorrect size of copying.
 *      Alan Cox                :       Added the cache manager code
 *      Alan Cox                :       Fixed the clone/copy bug and device race.
 *      Mike McLagan            :       Routing by source
 *      Malcolm Beattie         :       Buffer handling fixes.
 *      Alexey Kuznetsov        :       Double buffer free and other fixes.
 *      SVR Anand               :       Fixed several multicast bugs and problems.
 *      Alexey Kuznetsov        :       Status, optimisations and more.
 *      Brad Parker             :       Better behaviour on mrouted upcall
 *                                      overflow.
 *      Carlos Picoto           :       PIMv1 Support
 *      Pavlin Ivanov Radoslavov:       PIMv2 Registers must checksum only PIM header
 *                                      Relax this requirement to work with older peers.
 *
 */

#include <asm/uaccess.h>
#include <linux/types.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/igmp.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/mroute.h>
#include <linux/init.h>
#include <linux/if_ether.h>
#include <linux/slab.h>
#include <net/net_namespace.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <net/route.h>
#include <net/sock.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/raw.h>
#include <linux/notifier.h>
#include <linux/if_arp.h>
#include <linux/netfilter_ipv4.h>
#include <linux/compat.h>
#include <linux/export.h>
#include <net/ipip.h>
#include <net/checksum.h>
#include <net/netlink.h>
#include <net/fib_rules.h>

#if defined(CONFIG_IP_PIMSM_V1) || defined(CONFIG_IP_PIMSM_V2)
#define CONFIG_IP_PIMSM 1
#endif

struct mr_table {
        struct list_head        list;
#ifdef CONFIG_NET_NS
        struct net              *net;
#endif
        u32                     id;
        struct sock __rcu       *mroute_sk;
        struct timer_list       ipmr_expire_timer;
        struct list_head        mfc_unres_queue;
        struct list_head        mfc_cache_array[MFC_LINES];
        struct vif_device       vif_table[MAXVIFS];
        int                     maxvif;
        atomic_t                cache_resolve_queue_len;
        int                     mroute_do_assert;
        int                     mroute_do_pim;
#if defined(CONFIG_IP_PIMSM_V1) || defined(CONFIG_IP_PIMSM_V2)
        int                     mroute_reg_vif_num;
#endif
};

struct ipmr_rule {
        struct fib_rule         common;
};

struct ipmr_result {
        struct mr_table         *mrt;
};

/* Big lock, protecting vif table, mrt cache and mroute socket state.
 * Note that the changes are semaphored via rtnl_lock.
 */

static DEFINE_RWLOCK(mrt_lock);

/*
 *      Multicast router control variables
 */

#define VIF_EXISTS(_mrt, _idx) ((_mrt)->vif_table[_idx].dev != NULL)

/* Special spinlock for queue of unresolved entries */
static DEFINE_SPINLOCK(mfc_unres_lock);

/* We return to original Alan's scheme. Hash table of resolved
 * entries is changed only in process context and protected
 * with weak lock mrt_lock. Queue of unresolved entries is protected
 * with strong spinlock mfc_unres_lock.
 *
 * In this case data path is free of exclusive locks at all.
 */

static struct kmem_cache *mrt_cachep __read_mostly;

static struct mr_table *ipmr_new_table(struct net *net, u32 id);
static int ip_mr_forward(struct net *net, struct mr_table *mrt,
                         struct sk_buff *skb, struct mfc_cache *cache,
                         int local);
static int ipmr_cache_report(struct mr_table *mrt,
                             struct sk_buff *pkt, vifi_t vifi, int assert);
static int __ipmr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
                              struct mfc_cache *c, struct rtmsg *rtm);
static void ipmr_expire_process(unsigned long arg);

#ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
#define ipmr_for_each_table(mrt, net) \
        list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list)

static struct mr_table *ipmr_get_table(struct net *net, u32 id)
{
        struct mr_table *mrt;

        ipmr_for_each_table(mrt, net) {
                if (mrt->id == id)
                        return mrt;
        }
        return NULL;
}

static int ipmr_fib_lookup(struct net *net, struct flowi4 *flp4,
                           struct mr_table **mrt)
{
        struct ipmr_result res;
        struct fib_lookup_arg arg = { .result = &res, };
        int err;

        err = fib_rules_lookup(net->ipv4.mr_rules_ops,
                               flowi4_to_flowi(flp4), 0, &arg);
        if (err < 0)
                return err;
        *mrt = res.mrt;
        return 0;
}

static int ipmr_rule_action(struct fib_rule *rule, struct flowi *flp,
                            int flags, struct fib_lookup_arg *arg)
{
        struct ipmr_result *res = arg->result;
        struct mr_table *mrt;

        switch (rule->action) {
        case FR_ACT_TO_TBL:
                break;
        case FR_ACT_UNREACHABLE:
                return -ENETUNREACH;
        case FR_ACT_PROHIBIT:
                return -EACCES;
        case FR_ACT_BLACKHOLE:
        default:
                return -EINVAL;
        }

        mrt = ipmr_get_table(rule->fr_net, rule->table);
        if (mrt == NULL)
                return -EAGAIN;
        res->mrt = mrt;
        return 0;
}

static int ipmr_rule_match(struct fib_rule *rule, struct flowi *fl, int flags)
{
        return 1;
}

static const struct nla_policy ipmr_rule_policy[FRA_MAX + 1] = {
        FRA_GENERIC_POLICY,
};

static int ipmr_rule_configure(struct fib_rule *rule, struct sk_buff *skb,
                               struct fib_rule_hdr *frh, struct nlattr **tb)
{
        return 0;
}

static int ipmr_rule_compare(struct fib_rule *rule, struct fib_rule_hdr *frh,
                             struct nlattr **tb)
{
        return 1;
}

static int ipmr_rule_fill(struct fib_rule *rule, struct sk_buff *skb,
                          struct fib_rule_hdr *frh)
{
        frh->dst_len = 0;
        frh->src_len = 0;
        frh->tos     = 0;
        return 0;
}

static const struct fib_rules_ops __net_initdata ipmr_rules_ops_template = {
        .family         = RTNL_FAMILY_IPMR,
        .rule_size      = sizeof(struct ipmr_rule),
        .addr_size      = sizeof(u32),
        .action         = ipmr_rule_action,
        .match          = ipmr_rule_match,
        .configure      = ipmr_rule_configure,
        .compare        = ipmr_rule_compare,
        .default_pref   = fib_default_rule_pref,
        .fill           = ipmr_rule_fill,
        .nlgroup        = RTNLGRP_IPV4_RULE,
        .policy         = ipmr_rule_policy,
        .owner          = THIS_MODULE,
};

static int __net_init ipmr_rules_init(struct net *net)
{
        struct fib_rules_ops *ops;
        struct mr_table *mrt;
        int err;

        ops = fib_rules_register(&ipmr_rules_ops_template, net);
        if (IS_ERR(ops))
                return PTR_ERR(ops);

        INIT_LIST_HEAD(&net->ipv4.mr_tables);

        mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);
        if (mrt == NULL) {
                err = -ENOMEM;
                goto err1;
        }

        err = fib_default_rule_add(ops, 0x7fff, RT_TABLE_DEFAULT, 0);
        if (err < 0)
                goto err2;

        net->ipv4.mr_rules_ops = ops;
        return 0;

err2:
        kfree(mrt);
err1:
        fib_rules_unregister(ops);
        return err;
}

static void __net_exit ipmr_rules_exit(struct net *net)
{
        struct mr_table *mrt, *next;

        list_for_each_entry_safe(mrt, next, &net->ipv4.mr_tables, list) {
                list_del(&mrt->list);
                kfree(mrt);
        }
        fib_rules_unregister(net->ipv4.mr_rules_ops);
}
#else
#define ipmr_for_each_table(mrt, net) \
        for (mrt = net->ipv4.mrt; mrt; mrt = NULL)

static struct mr_table *ipmr_get_table(struct net *net, u32 id)
{
        return net->ipv4.mrt;
}

static int ipmr_fib_lookup(struct net *net, struct flowi4 *flp4,
                           struct mr_table **mrt)
{
        *mrt = net->ipv4.mrt;
        return 0;
}

static int __net_init ipmr_rules_init(struct net *net)
{
        net->ipv4.mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);
        return net->ipv4.mrt ? 0 : -ENOMEM;
}

static void __net_exit ipmr_rules_exit(struct net *net)
{
        kfree(net->ipv4.mrt);
}
#endif

static struct mr_table *ipmr_new_table(struct net *net, u32 id)
{
        struct mr_table *mrt;
        unsigned int i;

        mrt = ipmr_get_table(net, id);
        if (mrt != NULL)
                return mrt;

        mrt = kzalloc(sizeof(*mrt), GFP_KERNEL);
        if (mrt == NULL)
                return NULL;
        write_pnet(&mrt->net, net);
        mrt->id = id;

        /* Forwarding cache */
        for (i = 0; i < MFC_LINES; i++)
                INIT_LIST_HEAD(&mrt->mfc_cache_array[i]);

        INIT_LIST_HEAD(&mrt->mfc_unres_queue);

        setup_timer(&mrt->ipmr_expire_timer, ipmr_expire_process,
                    (unsigned long)mrt);

#ifdef CONFIG_IP_PIMSM
        mrt->mroute_reg_vif_num = -1;
#endif
#ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
        list_add_tail_rcu(&mrt->list, &net->ipv4.mr_tables);
#endif
        return mrt;
}

/* Service routines creating virtual interfaces: DVMRP tunnels and PIMREG */

static void ipmr_del_tunnel(struct net_device *dev, struct vifctl *v)
{
        struct net *net = dev_net(dev);

        dev_close(dev);

        dev = __dev_get_by_name(net, "tunl0");
        if (dev) {
                const struct net_device_ops *ops = dev->netdev_ops;
                struct ifreq ifr;
                struct ip_tunnel_parm p;

                memset(&p, 0, sizeof(p));
                p.iph.daddr = v->vifc_rmt_addr.s_addr;
                p.iph.saddr = v->vifc_lcl_addr.s_addr;
                p.iph.version = 4;
                p.iph.ihl = 5;
                p.iph.protocol = IPPROTO_IPIP;
                sprintf(p.name, "dvmrp%d", v->vifc_vifi);
                ifr.ifr_ifru.ifru_data = (__force void __user *)&p;

                if (ops->ndo_do_ioctl) {
                        mm_segment_t oldfs = get_fs();

                        set_fs(KERNEL_DS);
                        ops->ndo_do_ioctl(dev, &ifr, SIOCDELTUNNEL);
                        set_fs(oldfs);
                }
        }
}

static
struct net_device *ipmr_new_tunnel(struct net *net, struct vifctl *v)
{
        struct net_device  *dev;

        dev = __dev_get_by_name(net, "tunl0");

        if (dev) {
                const struct net_device_ops *ops = dev->netdev_ops;
                int err;
                struct ifreq ifr;
                struct ip_tunnel_parm p;
                struct in_device  *in_dev;

                memset(&p, 0, sizeof(p));
                p.iph.daddr = v->vifc_rmt_addr.s_addr;
                p.iph.saddr = v->vifc_lcl_addr.s_addr;
                p.iph.version = 4;
                p.iph.ihl = 5;
                p.iph.protocol = IPPROTO_IPIP;
                sprintf(p.name, "dvmrp%d", v->vifc_vifi);
                ifr.ifr_ifru.ifru_data = (__force void __user *)&p;

                if (ops->ndo_do_ioctl) {
                        mm_segment_t oldfs = get_fs();

                        set_fs(KERNEL_DS);
                        err = ops->ndo_do_ioctl(dev, &ifr, SIOCADDTUNNEL);
                        set_fs(oldfs);
                } else {
                        err = -EOPNOTSUPP;
                }
                dev = NULL;

                if (err == 0 &&
                    (dev = __dev_get_by_name(net, p.name)) != NULL) {
                        dev->flags |= IFF_MULTICAST;

                        in_dev = __in_dev_get_rtnl(dev);
                        if (in_dev == NULL)
                                goto failure;

                        ipv4_devconf_setall(in_dev);
                        IPV4_DEVCONF(in_dev->cnf, RP_FILTER) = 0;

                        if (dev_open(dev))
                                goto failure;
                        dev_hold(dev);
                }
        }
        return dev;

failure:
        /* allow the register to be completed before unregistering. */
        rtnl_unlock();
        rtnl_lock();

        unregister_netdevice(dev);
        return NULL;
}

#ifdef CONFIG_IP_PIMSM

static netdev_tx_t reg_vif_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct net *net = dev_net(dev);
        struct mr_table *mrt;
        struct flowi4 fl4 = {
                .flowi4_oif     = dev->ifindex,
                .flowi4_iif     = skb->skb_iif,
                .flowi4_mark    = skb->mark,
        };
        int err;

        err = ipmr_fib_lookup(net, &fl4, &mrt);
        if (err < 0) {
                kfree_skb(skb);
                return err;
        }

        read_lock(&mrt_lock);
        dev->stats.tx_bytes += skb->len;
        dev->stats.tx_packets++;
        ipmr_cache_report(mrt, skb, mrt->mroute_reg_vif_num, IGMPMSG_WHOLEPKT);
        read_unlock(&mrt_lock);
        kfree_skb(skb);
        return NETDEV_TX_OK;
}

static const struct net_device_ops reg_vif_netdev_ops = {
        .ndo_start_xmit = reg_vif_xmit,
};

static void reg_vif_setup(struct net_device *dev)
{
        dev->type               = ARPHRD_PIMREG;
        dev->mtu                = ETH_DATA_LEN - sizeof(struct iphdr) - 8;
        dev->flags              = IFF_NOARP;
        dev->netdev_ops         = &reg_vif_netdev_ops,
        dev->destructor         = free_netdev;
        dev->features           |= NETIF_F_NETNS_LOCAL;
}

static struct net_device *ipmr_reg_vif(struct net *net, struct mr_table *mrt)
{
        struct net_device *dev;
        struct in_device *in_dev;
        char name[IFNAMSIZ];

        if (mrt->id == RT_TABLE_DEFAULT)
                sprintf(name, "pimreg");
        else
                sprintf(name, "pimreg%u", mrt->id);

        dev = alloc_netdev(0, name, reg_vif_setup);

        if (dev == NULL)
                return NULL;

        dev_net_set(dev, net);

        if (register_netdevice(dev)) {
                free_netdev(dev);
                return NULL;
        }
        dev->iflink = 0;

        rcu_read_lock();
        in_dev = __in_dev_get_rcu(dev);
        if (!in_dev) {
                rcu_read_unlock();
                goto failure;
        }

        ipv4_devconf_setall(in_dev);
        IPV4_DEVCONF(in_dev->cnf, RP_FILTER) = 0;
        rcu_read_unlock();

        if (dev_open(dev))
                goto failure;

        dev_hold(dev);

        return dev;

failure:
        /* allow the register to be completed before unregistering. */
        rtnl_unlock();
        rtnl_lock();

        unregister_netdevice(dev);
        return NULL;
}
#endif

/*
 *      Delete a VIF entry
 *      @notify: Set to 1, if the caller is a notifier_call
 */

static int vif_delete(struct mr_table *mrt, int vifi, int notify,
                      struct list_head *head)
{
        struct vif_device *v;
        struct net_device *dev;
        struct in_device *in_dev;

        if (vifi < 0 || vifi >= mrt->maxvif)
                return -EADDRNOTAVAIL;

        v = &mrt->vif_table[vifi];

        write_lock_bh(&mrt_lock);
        dev = v->dev;
        v->dev = NULL;

        if (!dev) {
                write_unlock_bh(&mrt_lock);
                return -EADDRNOTAVAIL;
        }

#ifdef CONFIG_IP_PIMSM
        if (vifi == mrt->mroute_reg_vif_num)
                mrt->mroute_reg_vif_num = -1;
#endif

        if (vifi + 1 == mrt->maxvif) {
                int tmp;

                for (tmp = vifi - 1; tmp >= 0; tmp--) {
                        if (VIF_EXISTS(mrt, tmp))
                                break;
                }
                mrt->maxvif = tmp+1;
        }

        write_unlock_bh(&mrt_lock);

        dev_set_allmulti(dev, -1);

        in_dev = __in_dev_get_rtnl(dev);
        if (in_dev) {
                IPV4_DEVCONF(in_dev->cnf, MC_FORWARDING)--;
                ip_rt_multicast_event(in_dev);
        }

        if (v->flags & (VIFF_TUNNEL | VIFF_REGISTER) && !notify)
                unregister_netdevice_queue(dev, head);

        dev_put(dev);
        return 0;
}

static void ipmr_cache_free_rcu(struct rcu_head *head)
{
        struct mfc_cache *c = container_of(head, struct mfc_cache, rcu);

        kmem_cache_free(mrt_cachep, c);
}

static inline void ipmr_cache_free(struct mfc_cache *c)
{
        call_rcu(&c->rcu, ipmr_cache_free_rcu);
}

/* Destroy an unresolved cache entry, killing queued skbs
 * and reporting error to netlink readers.
 */

static void ipmr_destroy_unres(struct mr_table *mrt, struct mfc_cache *c)
{
        struct net *net = read_pnet(&mrt->net);
        struct sk_buff *skb;
        struct nlmsgerr *e;

        atomic_dec(&mrt->cache_resolve_queue_len);

        while ((skb = skb_dequeue(&c->mfc_un.unres.unresolved))) {
                if (ip_hdr(skb)->version == 0) {
                        struct nlmsghdr *nlh = (struct nlmsghdr *)skb_pull(skb, sizeof(struct iphdr));
                        nlh->nlmsg_type = NLMSG_ERROR;
                        nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nlmsgerr));
                        skb_trim(skb, nlh->nlmsg_len);
                        e = NLMSG_DATA(nlh);
                        e->error = -ETIMEDOUT;
                        memset(&e->msg, 0, sizeof(e->msg));

                        rtnl_unicast(skb, net, NETLINK_CB(skb).pid);
                } else {
                        kfree_skb(skb);
                }
        }

        ipmr_cache_free(c);
}


/* Timer process for the unresolved queue. */

static void ipmr_expire_process(unsigned long arg)
{
        struct mr_table *mrt = (struct mr_table *)arg;
        unsigned long now;
        unsigned long expires;
        struct mfc_cache *c, *next;

        if (!spin_trylock(&mfc_unres_lock)) {
                mod_timer(&mrt->ipmr_expire_timer, jiffies+HZ/10);
                return;
        }

        if (list_empty(&mrt->mfc_unres_queue))
                goto out;

        now = jiffies;
        expires = 10*HZ;

        list_for_each_entry_safe(c, next, &mrt->mfc_unres_queue, list) {
                if (time_after(c->mfc_un.unres.expires, now)) {
                        unsigned long interval = c->mfc_un.unres.expires - now;
                        if (interval < expires)
                                expires = interval;
                        continue;
                }

                list_del(&c->list);
                ipmr_destroy_unres(mrt, c);
        }

        if (!list_empty(&mrt->mfc_unres_queue))
                mod_timer(&mrt->ipmr_expire_timer, jiffies + expires);

out:
        spin_unlock(&mfc_unres_lock);
}

/* Fill oifs list. It is called under write locked mrt_lock. */

static void ipmr_update_thresholds(struct mr_table *mrt, struct mfc_cache *cache,
                                   unsigned char *ttls)
{
        int vifi;

        cache->mfc_un.res.minvif = MAXVIFS;
        cache->mfc_un.res.maxvif = 0;
        memset(cache->mfc_un.res.ttls, 255, MAXVIFS);

        for (vifi = 0; vifi < mrt->maxvif; vifi++) {
                if (VIF_EXISTS(mrt, vifi) &&
                    ttls[vifi] && ttls[vifi] < 255) {
                        cache->mfc_un.res.ttls[vifi] = ttls[vifi];
                        if (cache->mfc_un.res.minvif > vifi)
                                cache->mfc_un.res.minvif = vifi;
                        if (cache->mfc_un.res.maxvif <= vifi)
                                cache->mfc_un.res.maxvif = vifi + 1;
                }
        }
}

static int vif_add(struct net *net, struct mr_table *mrt,
                   struct vifctl *vifc, int mrtsock)
{
        int vifi = vifc->vifc_vifi;
        struct vif_device *v = &mrt->vif_table[vifi];
        struct net_device *dev;
        struct in_device *in_dev;
        int err;

        /* Is vif busy ? */
        if (VIF_EXISTS(mrt, vifi))
                return -EADDRINUSE;

        switch (vifc->vifc_flags) {
#ifdef CONFIG_IP_PIMSM
        case VIFF_REGISTER:
                /*
                 * Special Purpose VIF in PIM
                 * All the packets will be sent to the daemon
                 */
                if (mrt->mroute_reg_vif_num >= 0)
                        return -EADDRINUSE;
                dev = ipmr_reg_vif(net, mrt);
                if (!dev)
                        return -ENOBUFS;
                err = dev_set_allmulti(dev, 1);
                if (err) {
                        unregister_netdevice(dev);
                        dev_put(dev);
                        return err;
                }
                break;
#endif
        case VIFF_TUNNEL:
                dev = ipmr_new_tunnel(net, vifc);
                if (!dev)
                        return -ENOBUFS;
                err = dev_set_allmulti(dev, 1);
                if (err) {
                        ipmr_del_tunnel(dev, vifc);
                        dev_put(dev);
                        return err;
                }
                break;

        case VIFF_USE_IFINDEX:
        case 0:
                if (vifc->vifc_flags == VIFF_USE_IFINDEX) {
                        dev = dev_get_by_index(net, vifc->vifc_lcl_ifindex);
                        if (dev && __in_dev_get_rtnl(dev) == NULL) {
                                dev_put(dev);
                                return -EADDRNOTAVAIL;
                        }
                } else {
                        dev = ip_dev_find(net, vifc->vifc_lcl_addr.s_addr);
                }
                if (!dev)
                        return -EADDRNOTAVAIL;
                err = dev_set_allmulti(dev, 1);
                if (err) {
                        dev_put(dev);
                        return err;
                }
                break;
        default:
                return -EINVAL;
        }

        in_dev = __in_dev_get_rtnl(dev);
        if (!in_dev) {
                dev_put(dev);
                return -EADDRNOTAVAIL;
        }
        IPV4_DEVCONF(in_dev->cnf, MC_FORWARDING)++;
        ip_rt_multicast_event(in_dev);

        /* Fill in the VIF structures */

        v->rate_limit = vifc->vifc_rate_limit;
        v->local = vifc->vifc_lcl_addr.s_addr;
        v->remote = vifc->vifc_rmt_addr.s_addr;
        v->flags = vifc->vifc_flags;
        if (!mrtsock)
                v->flags |= VIFF_STATIC;
        v->threshold = vifc->vifc_threshold;
        v->bytes_in = 0;
        v->bytes_out = 0;
        v->pkt_in = 0;
        v->pkt_out = 0;
        v->link = dev->ifindex;
        if (v->flags & (VIFF_TUNNEL | VIFF_REGISTER))
                v->link = dev->iflink;

        /* And finish update writing critical data */
        write_lock_bh(&mrt_lock);
        v->dev = dev;
#ifdef CONFIG_IP_PIMSM
        if (v->flags & VIFF_REGISTER)
                mrt->mroute_reg_vif_num = vifi;
#endif
        if (vifi+1 > mrt->maxvif)
                mrt->maxvif = vifi+1;
        write_unlock_bh(&mrt_lock);
        return 0;
}

/* called with rcu_read_lock() */
static struct mfc_cache *ipmr_cache_find(struct mr_table *mrt,
                                         __be32 origin,
                                         __be32 mcastgrp)
{
        int line = MFC_HASH(mcastgrp, origin);
        struct mfc_cache *c;

        list_for_each_entry_rcu(c, &mrt->mfc_cache_array[line], list) {
                if (c->mfc_origin == origin && c->mfc_mcastgrp == mcastgrp)
                        return c;
        }
        return NULL;
}

/*
 *      Allocate a multicast cache entry
 */
static struct mfc_cache *ipmr_cache_alloc(void)
{
        struct mfc_cache *c = kmem_cache_zalloc(mrt_cachep, GFP_KERNEL);

        if (c)
                c->mfc_un.res.minvif = MAXVIFS;
        return c;
}

static struct mfc_cache *ipmr_cache_alloc_unres(void)
{
        struct mfc_cache *c = kmem_cache_zalloc(mrt_cachep, GFP_ATOMIC);

        if (c) {
                skb_queue_head_init(&c->mfc_un.unres.unresolved);
                c->mfc_un.unres.expires = jiffies + 10*HZ;
        }
        return c;
}

/*
 *      A cache entry has gone into a resolved state from queued
 */

static void ipmr_cache_resolve(struct net *net, struct mr_table *mrt,
                               struct mfc_cache *uc, struct mfc_cache *c)
{
        struct sk_buff *skb;
        struct nlmsgerr *e;

        /* Play the pending entries through our router */

        while ((skb = __skb_dequeue(&uc->mfc_un.unres.unresolved))) {
                if (ip_hdr(skb)->version == 0) {
                        struct nlmsghdr *nlh = (struct nlmsghdr *)skb_pull(skb, sizeof(struct iphdr));

                        if (__ipmr_fill_mroute(mrt, skb, c, NLMSG_DATA(nlh)) > 0) {
                                nlh->nlmsg_len = skb_tail_pointer(skb) -
                                                 (u8 *)nlh;
                        } else {
                                nlh->nlmsg_type = NLMSG_ERROR;
                                nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nlmsgerr));
                                skb_trim(skb, nlh->nlmsg_len);
                                e = NLMSG_DATA(nlh);
                                e->error = -EMSGSIZE;
                                memset(&e->msg, 0, sizeof(e->msg));
                        }

                        rtnl_unicast(skb, net, NETLINK_CB(skb).pid);
                } else {
                        ip_mr_forward(net, mrt, skb, c, 0);
                }
        }
}

/*
 *      Bounce a cache query up to mrouted. We could use netlink for this but mrouted
 *      expects the following bizarre scheme.
 *
 *      Called under mrt_lock.
 */

static int ipmr_cache_report(struct mr_table *mrt,
                             struct sk_buff *pkt, vifi_t vifi, int assert)
{
        struct sk_buff *skb;
        const int ihl = ip_hdrlen(pkt);
        struct igmphdr *igmp;
        struct igmpmsg *msg;
        struct sock *mroute_sk;
        int ret;

#ifdef CONFIG_IP_PIMSM
        if (assert == IGMPMSG_WHOLEPKT)
                skb = skb_realloc_headroom(pkt, sizeof(struct iphdr));
        else
#endif
                skb = alloc_skb(128, GFP_ATOMIC);

        if (!skb)
                return -ENOBUFS;

#ifdef CONFIG_IP_PIMSM
        if (assert == IGMPMSG_WHOLEPKT) {
                /* Ugly, but we have no choice with this interface.
                 * Duplicate old header, fix ihl, length etc.
                 * And all this only to mangle msg->im_msgtype and
                 * to set msg->im_mbz to "mbz" :-)
                 */
                skb_push(skb, sizeof(struct iphdr));
                skb_reset_network_header(skb);
                skb_reset_transport_header(skb);
                msg = (struct igmpmsg *)skb_network_header(skb);
                memcpy(msg, skb_network_header(pkt), sizeof(struct iphdr));
                msg->im_msgtype = IGMPMSG_WHOLEPKT;
                msg->im_mbz = 0;
                msg->im_vif = mrt->mroute_reg_vif_num;
                ip_hdr(skb)->ihl = sizeof(struct iphdr) >> 2;
                ip_hdr(skb)->tot_len = htons(ntohs(ip_hdr(pkt)->tot_len) +
                                             sizeof(struct iphdr));
        } else
#endif
        {

        /* Copy the IP header */

        skb->network_header = skb->tail;
        skb_put(skb, ihl);
        skb_copy_to_linear_data(skb, pkt->data, ihl);
        ip_hdr(skb)->protocol = 0;      /* Flag to the kernel this is a route add */
        msg = (struct igmpmsg *)skb_network_header(skb);
        msg->im_vif = vifi;
        skb_dst_set(skb, dst_clone(skb_dst(pkt)));

        /* Add our header */

        igmp = (struct igmphdr *)skb_put(skb, sizeof(struct igmphdr));
        igmp->type      =
        msg->im_msgtype = assert;
        igmp->code      = 0;
        ip_hdr(skb)->tot_len = htons(skb->len);         /* Fix the length */
        skb->transport_header = skb->network_header;
        }

        rcu_read_lock();
        mroute_sk = rcu_dereference(mrt->mroute_sk);
        if (mroute_sk == NULL) {
                rcu_read_unlock();
                kfree_skb(skb);
                return -EINVAL;
        }

        /* Deliver to mrouted */

        ret = sock_queue_rcv_skb(mroute_sk, skb);
        rcu_read_unlock();
        if (ret < 0) {
                net_warn_ratelimited("mroute: pending queue full, dropping entries\n");
                kfree_skb(skb);
        }

        return ret;
}

/*
 *      Queue a packet for resolution. It gets locked cache entry!
 */

static int
ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi, struct sk_buff *skb)
{
        bool found = false;
        int err;
        struct mfc_cache *c;
        const struct iphdr *iph = ip_hdr(skb);

        spin_lock_bh(&mfc_unres_lock);
        list_for_each_entry(c, &mrt->mfc_unres_queue, list) {
                if (c->mfc_mcastgrp == iph->daddr &&
                    c->mfc_origin == iph->saddr) {
                        found = true;
                        break;
                }
        }

        if (!found) {
                /* Create a new entry if allowable */

                if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||
                    (c = ipmr_cache_alloc_unres()) == NULL) {
                        spin_unlock_bh(&mfc_unres_lock);

                        kfree_skb(skb);
                        return -ENOBUFS;
                }

                /* Fill in the new cache entry */

                c->mfc_parent   = -1;
                c->mfc_origin   = iph->saddr;
                c->mfc_mcastgrp = iph->daddr;

                /* Reflect first query at mrouted. */

                err = ipmr_cache_report(mrt, skb, vifi, IGMPMSG_NOCACHE);
                if (err < 0) {

                        /* If the report failed throw the cache entry
                           out - Brad Parker
                         */
                        spin_unlock_bh(&mfc_unres_lock);

                        ipmr_cache_free(c);
                        kfree_skb(skb);
                        return err;
                }

                atomic_inc(&mrt->cache_resolve_queue_len);
                list_add(&c->list, &mrt->mfc_unres_queue);

                if (atomic_read(&mrt->cache_resolve_queue_len) == 1)
                        mod_timer(&mrt->ipmr_expire_timer, c->mfc_un.unres.expires);
        }

        /* See if we can append the packet */

        if (c->mfc_un.unres.unresolved.qlen > 3) {
                kfree_skb(skb);
                err = -ENOBUFS;
        } else {
                skb_queue_tail(&c->mfc_un.unres.unresolved, skb);
                err = 0;
        }

        spin_unlock_bh(&mfc_unres_lock);
        return err;
}

/*
 *      MFC cache manipulation by user space mroute daemon
 */

static int ipmr_mfc_delete(struct mr_table *mrt, struct mfcctl *mfc)
{
        int line;
        struct mfc_cache *c, *next;

        line = MFC_HASH(mfc->mfcc_mcastgrp.s_addr, mfc->mfcc_origin.s_addr);

        list_for_each_entry_safe(c, next, &mrt->mfc_cache_array[line], list) {
                if (c->mfc_origin == mfc->mfcc_origin.s_addr &&
                    c->mfc_mcastgrp == mfc->mfcc_mcastgrp.s_addr) {
                        list_del_rcu(&c->list);

                        ipmr_cache_free(c);
                        return 0;
                }
        }
        return -ENOENT;
}

static int ipmr_mfc_add(struct net *net, struct mr_table *mrt,
                        struct mfcctl *mfc, int mrtsock)
{
        bool found = false;
        int line;
        struct mfc_cache *uc, *c;

        if (mfc->mfcc_parent >= MAXVIFS)
                return -ENFILE;

        line = MFC_HASH(mfc->mfcc_mcastgrp.s_addr, mfc->mfcc_origin.s_addr);

        list_for_each_entry(c, &mrt->mfc_cache_array[line], list) {
                if (c->mfc_origin == mfc->mfcc_origin.s_addr &&
                    c->mfc_mcastgrp == mfc->mfcc_mcastgrp.s_addr) {
                        found = true;
                        break;
                }
        }

        if (found) {
                write_lock_bh(&mrt_lock);
                c->mfc_parent = mfc->mfcc_parent;
                ipmr_update_thresholds(mrt, c, mfc->mfcc_ttls);
                if (!mrtsock)
                        c->mfc_flags |= MFC_STATIC;
                write_unlock_bh(&mrt_lock);
                return 0;
        }

        if (!ipv4_is_multicast(mfc->mfcc_mcastgrp.s_addr))
                return -EINVAL;

        c = ipmr_cache_alloc();
        if (c == NULL)
                return -ENOMEM;

        c->mfc_origin = mfc->mfcc_origin.s_addr;
        c->mfc_mcastgrp = mfc->mfcc_mcastgrp.s_addr;
        c->mfc_parent = mfc->mfcc_parent;
        ipmr_update_thresholds(mrt, c, mfc->mfcc_ttls);
        if (!mrtsock)
                c->mfc_flags |= MFC_STATIC;

        list_add_rcu(&c->list, &mrt->mfc_cache_array[line]);

        /*
         *      Check to see if we resolved a queued list. If so we
         *      need to send on the frames and tidy up.
         */
        found = false;
        spin_lock_bh(&mfc_unres_lock);
        list_for_each_entry(uc, &mrt->mfc_unres_queue, list) {
                if (uc->mfc_origin == c->mfc_origin &&
                    uc->mfc_mcastgrp == c->mfc_mcastgrp) {
                        list_del(&uc->list);
                        atomic_dec(&mrt->cache_resolve_queue_len);
                        found = true;
                        break;
                }
        }
        if (list_empty(&mrt->mfc_unres_queue))
                del_timer(&mrt->ipmr_expire_timer);
        spin_unlock_bh(&mfc_unres_lock);

        if (found) {
                ipmr_cache_resolve(net, mrt, uc, c);
                ipmr_cache_free(uc);
        }
        return 0;
}

/*
 *      Close the multicast socket, and clear the vif tables etc
 */

static void mroute_clean_tables(struct mr_table *mrt)
{
        int i;
        LIST_HEAD(list);
        struct mfc_cache *c, *next;

        /* Shut down all active vif entries */

        for (i = 0; i < mrt->maxvif; i++) {
                if (!(mrt->vif_table[i].flags & VIFF_STATIC))
                        vif_delete(mrt, i, 0, &list);
        }
        unregister_netdevice_many(&list);

        /* Wipe the cache */

        for (i = 0; i < MFC_LINES; i++) {
                list_for_each_entry_safe(c, next, &mrt->mfc_cache_array[i], list) {
                        if (c->mfc_flags & MFC_STATIC)
                                continue;
                        list_del_rcu(&c->list);
                        ipmr_cache_free(c);
                }
        }

        if (atomic_read(&mrt->cache_resolve_queue_len) != 0) {
                spin_lock_bh(&mfc_unres_lock);
                list_for_each_entry_safe(c, next, &mrt->mfc_unres_queue, list) {
                        list_del(&c->list);
                        ipmr_destroy_unres(mrt, c);
                }
                spin_unlock_bh(&mfc_unres_lock);
        }
}

/* called from ip_ra_control(), before an RCU grace period,
 * we dont need to call synchronize_rcu() here
 */
static void mrtsock_destruct(struct sock *sk)
{
        struct net *net = sock_net(sk);
        struct mr_table *mrt;

        rtnl_lock();
        ipmr_for_each_table(mrt, net) {
                if (sk == rtnl_dereference(mrt->mroute_sk)) {
                        IPV4_DEVCONF_ALL(net, MC_FORWARDING)--;
                        RCU_INIT_POINTER(mrt->mroute_sk, NULL);
                        mroute_clean_tables(mrt);
                }
        }
        rtnl_unlock();
}

/*
 *      Socket options and virtual interface manipulation. The whole
 *      virtual interface system is a complete heap, but unfortunately
 *      that's how BSD mrouted happens to think. Maybe one day with a proper
 *      MOSPF/PIM router set up we can clean this up.
 */

int ip_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, unsigned int optlen)
{
        int ret;
        struct vifctl vif;
        struct mfcctl mfc;
        struct net *net = sock_net(sk);
        struct mr_table *mrt;

        mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);
        if (mrt == NULL)
                return -ENOENT;

        if (optname != MRT_INIT) {
                if (sk != rcu_access_pointer(mrt->mroute_sk) &&
                    !capable(CAP_NET_ADMIN))
                        return -EACCES;
        }

        switch (optname) {
        case MRT_INIT:
                if (sk->sk_type != SOCK_RAW ||
                    inet_sk(sk)->inet_num != IPPROTO_IGMP)
                        return -EOPNOTSUPP;
                if (optlen != sizeof(int))
                        return -ENOPROTOOPT;

                rtnl_lock();
                if (rtnl_dereference(mrt->mroute_sk)) {
                        rtnl_unlock();
                        return -EADDRINUSE;
                }

                ret = ip_ra_control(sk, 1, mrtsock_destruct);
                if (ret == 0) {
                        rcu_assign_pointer(mrt->mroute_sk, sk);
                        IPV4_DEVCONF_ALL(net, MC_FORWARDING)++;
                }
                rtnl_unlock();
                return ret;
        case MRT_DONE:
                if (sk != rcu_access_pointer(mrt->mroute_sk))
                        return -EACCES;
                return ip_ra_control(sk, 0, NULL);
        case MRT_ADD_VIF:
        case MRT_DEL_VIF:
                if (optlen != sizeof(vif))
                        return -EINVAL;
                if (copy_from_user(&vif, optval, sizeof(vif)))
                        return -EFAULT;
                if (vif.vifc_vifi >= MAXVIFS)
                        return -ENFILE;
                rtnl_lock();
                if (optname == MRT_ADD_VIF) {
                        ret = vif_add(net, mrt, &vif,
                                      sk == rtnl_dereference(mrt->mroute_sk));
                } else {
                        ret = vif_delete(mrt, vif.vifc_vifi, 0, NULL);
                }
                rtnl_unlock();
                return ret;

                /*
                 *      Manipulate the forwarding caches. These live
                 *      in a sort of kernel/user symbiosis.
                 */
        case MRT_ADD_MFC:
        case MRT_DEL_MFC:
                if (optlen != sizeof(mfc))
                        return -EINVAL;
                if (copy_from_user(&mfc, optval, sizeof(mfc)))
                        return -EFAULT;
                rtnl_lock();
                if (optname == MRT_DEL_MFC)
                        ret = ipmr_mfc_delete(mrt, &mfc);
                else
                        ret = ipmr_mfc_add(net, mrt, &mfc,
                                           sk == rtnl_dereference(mrt->mroute_sk));
                rtnl_unlock();
                return ret;
                /*
                 *      Control PIM assert.
                 */
        case MRT_ASSERT:
        {
                int v;
                if (get_user(v, (int __user *)optval))
                        return -EFAULT;
                mrt->mroute_do_assert = (v) ? 1 : 0;
                return 0;
        }
#ifdef CONFIG_IP_PIMSM
        case MRT_PIM:
        {
                int v;

                if (get_user(v, (int __user *)optval))
                        return -EFAULT;
                v = (v) ? 1 : 0;

                rtnl_lock();
                ret = 0;
                if (v != mrt->mroute_do_pim) {
                        mrt->mroute_do_pim = v;
                        mrt->mroute_do_assert = v;
                }
                rtnl_unlock();
                return ret;
        }
#endif
#ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
        case MRT_TABLE:
        {
                u32 v;

                if (optlen != sizeof(u32))
                        return -EINVAL;
                if (get_user(v, (u32 __user *)optval))
                        return -EFAULT;

                rtnl_lock();
                ret = 0;
                if (sk == rtnl_dereference(mrt->mroute_sk)) {
                        ret = -EBUSY;
                } else {
                        if (!ipmr_new_table(net, v))
                                ret = -ENOMEM;
                        raw_sk(sk)->ipmr_table = v;
                }
                rtnl_unlock();
                return ret;
        }
#endif
        /*
         *      Spurious command, or MRT_VERSION which you cannot
         *      set.
         */
        default:
                return -ENOPROTOOPT;
        }
}

/*
 *      Getsock opt support for the multicast routing system.
 */

int ip_mroute_getsockopt(struct sock *sk, int optname, char __user *optval, int __user *optlen)
{
        int olr;
        int val;
        struct net *net = sock_net(sk);
        struct mr_table *mrt;

        mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);
        if (mrt == NULL)
                return -ENOENT;

        if (optname != MRT_VERSION &&
#ifdef CONFIG_IP_PIMSM
           optname != MRT_PIM &&
#endif
           optname != MRT_ASSERT)
                return -ENOPROTOOPT;

        if (get_user(olr, optlen))
                return -EFAULT;

        olr = min_t(unsigned int, olr, sizeof(int));
        if (olr < 0)
                return -EINVAL;

        if (put_user(olr, optlen))
                return -EFAULT;
        if (optname == MRT_VERSION)
                val = 0x0305;
#ifdef CONFIG_IP_PIMSM
        else if (optname == MRT_PIM)
                val = mrt->mroute_do_pim;
#endif
        else
                val = mrt->mroute_do_assert;
        if (copy_to_user(optval, &val, olr))
                return -EFAULT;
        return 0;
}

/*
 *      The IP multicast ioctl support routines.
 */

int ipmr_ioctl(struct sock *sk, int cmd, void __user *arg)
{
        struct sioc_sg_req sr;
        struct sioc_vif_req vr;
        struct vif_device *vif;
        struct mfc_cache *c;
        struct net *net = sock_net(sk);
        struct mr_table *mrt;

        mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);
        if (mrt == NULL)
                return -ENOENT;

        switch (cmd) {
        case SIOCGETVIFCNT:
                if (copy_from_user(&vr, arg, sizeof(vr)))
                        return -EFAULT;
                if (vr.vifi >= mrt->maxvif)
                        return -EINVAL;
                read_lock(&mrt_lock);
                vif = &mrt->vif_table[vr.vifi];
                if (VIF_EXISTS(mrt, vr.vifi)) {
                        vr.icount = vif->pkt_in;
                        vr.ocount = vif->pkt_out;
                        vr.ibytes = vif->bytes_in;
                        vr.obytes = vif->bytes_out;
                        read_unlock(&mrt_lock);

                        if (copy_to_user(arg, &vr, sizeof(vr)))
                                return -EFAULT;
                        return 0;
                }
                read_unlock(&mrt_lock);
                return -EADDRNOTAVAIL;
        case SIOCGETSGCNT:
                if (copy_from_user(&sr, arg, sizeof(sr)))
                        return -EFAULT;

                rcu_read_lock();
                c = ipmr_cache_find(mrt, sr.src.s_addr, sr.grp.s_addr);
                if (c) {
                        sr.pktcnt = c->mfc_un.res.pkt;
                        sr.bytecnt = c->mfc_un.res.bytes;
                        sr.wrong_if = c->mfc_un.res.wrong_if;
                        rcu_read_unlock();

                        if (copy_to_user(arg, &sr, sizeof(sr)))
                                return -EFAULT;
                        return 0;
                }
                rcu_read_unlock();
                return -EADDRNOTAVAIL;
        default:
                return -ENOIOCTLCMD;
        }
}

#ifdef CONFIG_COMPAT
struct compat_sioc_sg_req {
        struct in_addr src;
        struct in_addr grp;
        compat_ulong_t pktcnt;
        compat_ulong_t bytecnt;
        compat_ulong_t wrong_if;
};

struct compat_sioc_vif_req {
        vifi_t  vifi;           /* Which iface */
        compat_ulong_t icount;
        compat_ulong_t ocount;
        compat_ulong_t ibytes;
        compat_ulong_t obytes;
};

int ipmr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *arg)
{
        struct compat_sioc_sg_req sr;
        struct compat_sioc_vif_req vr;
        struct vif_device *vif;
        struct mfc_cache *c;
        struct net *net = sock_net(sk);
        struct mr_table *mrt;

        mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);
        if (mrt == NULL)
                return -ENOENT;

        switch (cmd) {
        case SIOCGETVIFCNT:
                if (copy_from_user(&vr, arg, sizeof(vr)))
                        return -EFAULT;
                if (vr.vifi >= mrt->maxvif)
                        return -EINVAL;
                read_lock(&mrt_lock);
                vif = &mrt->vif_table[vr.vifi];
                if (VIF_EXISTS(mrt, vr.vifi)) {
                        vr.icount = vif->pkt_in;
                        vr.ocount = vif->pkt_out;
                        vr.ibytes = vif->bytes_in;
                        vr.obytes = vif->bytes_out;
                        read_unlock(&mrt_lock);

                        if (copy_to_user(arg, &vr, sizeof(vr)))
                                return -EFAULT;
                        return 0;
                }
                read_unlock(&mrt_lock);
                return -EADDRNOTAVAIL;
        case SIOCGETSGCNT:
                if (copy_from_user(&sr, arg, sizeof(sr)))
                        return -EFAULT;

                rcu_read_lock();
                c = ipmr_cache_find(mrt, sr.src.s_addr, sr.grp.s_addr);
                if (c) {
                        sr.pktcnt = c->mfc_un.res.pkt;
                        sr.bytecnt = c->mfc_un.res.bytes;
                        sr.wrong_if = c->mfc_un.res.wrong_if;
                        rcu_read_unlock();

                        if (copy_to_user(arg, &sr, sizeof(sr)))
                                return -EFAULT;
                        return 0;
                }
                rcu_read_unlock();
                return -EADDRNOTAVAIL;
        default:
                return -ENOIOCTLCMD;
        }
}
#endif


static int ipmr_device_event(struct notifier_block *this, unsigned long event, void *ptr)
{
        struct net_device *dev = ptr;
        struct net *net = dev_net(dev);
        struct mr_table *mrt;
        struct vif_device *v;
        int ct;

        if (event != NETDEV_UNREGISTER)
                return NOTIFY_DONE;

        ipmr_for_each_table(mrt, net) {
                v = &mrt->vif_table[0];
                for (ct = 0; ct < mrt->maxvif; ct++, v++) {
                        if (v->dev == dev)
                                vif_delete(mrt, ct, 1, NULL);
                }
        }
        return NOTIFY_DONE;
}


static struct notifier_block ip_mr_notifier = {
        .notifier_call = ipmr_device_event,
};

/*
 *      Encapsulate a packet by attaching a valid IPIP header to it.
 *      This avoids tunnel drivers and other mess and gives us the speed so
 *      important for multicast video.
 */

static void ip_encap(struct sk_buff *skb, __be32 saddr, __be32 daddr)
{
        struct iphdr *iph;
        const struct iphdr *old_iph = ip_hdr(skb);

        skb_push(skb, sizeof(struct iphdr));
        skb->transport_header = skb->network_header;
        skb_reset_network_header(skb);
        iph = ip_hdr(skb);

        iph->version    =       4;
        iph->tos        =       old_iph->tos;
        iph->ttl        =       old_iph->ttl;
        iph->frag_off   =       0;
        iph->daddr      =       daddr;
        iph->saddr      =       saddr;
        iph->protocol   =       IPPROTO_IPIP;
        iph->ihl        =       5;
        iph->tot_len    =       htons(skb->len);
        ip_select_ident(iph, skb_dst(skb), NULL);
        ip_send_check(iph);

        memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
        nf_reset(skb);
}

static inline int ipmr_forward_finish(struct sk_buff *skb)
{
        struct ip_options *opt = &(IPCB(skb)->opt);

        IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
        IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);

        if (unlikely(opt->optlen))
                ip_forward_options(skb);

        return dst_output(skb);
}

/*
 *      Processing handlers for ipmr_forward
 */

static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,
                            struct sk_buff *skb, struct mfc_cache *c, int vifi)
{
        const struct iphdr *iph = ip_hdr(skb);
        struct vif_device *vif = &mrt->vif_table[vifi];
        struct net_device *dev;
        struct rtable *rt;
        struct flowi4 fl4;
        int    encap = 0;

        if (vif->dev == NULL)
                goto out_free;

#ifdef CONFIG_IP_PIMSM
        if (vif->flags & VIFF_REGISTER) {
                vif->pkt_out++;
                vif->bytes_out += skb->len;
                vif->dev->stats.tx_bytes += skb->len;
                vif->dev->stats.tx_packets++;
                ipmr_cache_report(mrt, skb, vifi, IGMPMSG_WHOLEPKT);
                goto out_free;
        }
#endif

        if (vif->flags & VIFF_TUNNEL) {
                rt = ip_route_output_ports(net, &fl4, NULL,
                                           vif->remote, vif->local,
                                           0, 0,
                                           IPPROTO_IPIP,
                                           RT_TOS(iph->tos), vif->link);
                if (IS_ERR(rt))
                        goto out_free;
                encap = sizeof(struct iphdr);
        } else {
                rt = ip_route_output_ports(net, &fl4, NULL, iph->daddr, 0,
                                           0, 0,
                                           IPPROTO_IPIP,
                                           RT_TOS(iph->tos), vif->link);
                if (IS_ERR(rt))
                        goto out_free;
        }

        dev = rt->dst.dev;

        if (skb->len+encap > dst_mtu(&rt->dst) && (ntohs(iph->frag_off) & IP_DF)) {
                /* Do not fragment multicasts. Alas, IPv4 does not
                 * allow to send ICMP, so that packets will disappear
                 * to blackhole.
                 */

                IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
                ip_rt_put(rt);
                goto out_free;
        }

        encap += LL_RESERVED_SPACE(dev) + rt->dst.header_len;

        if (skb_cow(skb, encap)) {
                ip_rt_put(rt);
                goto out_free;
        }

        vif->pkt_out++;
        vif->bytes_out += skb->len;

        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);
        ip_decrease_ttl(ip_hdr(skb));

        /* FIXME: forward and output firewalls used to be called here.
         * What do we do with netfilter? -- RR
         */
        if (vif->flags & VIFF_TUNNEL) {
                ip_encap(skb, vif->local, vif->remote);
                /* FIXME: extra output firewall step used to be here. --RR */
                vif->dev->stats.tx_packets++;
                vif->dev->stats.tx_bytes += skb->len;
        }

        IPCB(skb)->flags |= IPSKB_FORWARDED;

        /*
         * RFC1584 teaches, that DVMRP/PIM router must deliver packets locally
         * not only before forwarding, but after forwarding on all output
         * interfaces. It is clear, if mrouter runs a multicasting
         * program, it should receive packets not depending to what interface
         * program is joined.
         * If we will not make it, the program will have to join on all
         * interfaces. On the other hand, multihoming host (or router, but
         * not mrouter) cannot join to more than one interface - it will
         * result in receiving multiple packets.
         */
        NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, skb, skb->dev, dev,
                ipmr_forward_finish);
        return;

out_free:
        kfree_skb(skb);
}

static int ipmr_find_vif(struct mr_table *mrt, struct net_device *dev)
{
        int ct;

        for (ct = mrt->maxvif-1; ct >= 0; ct--) {
                if (mrt->vif_table[ct].dev == dev)
                        break;
        }
        return ct;
}

/* "local" means that we should preserve one skb (for local delivery) */

static int ip_mr_forward(struct net *net, struct mr_table *mrt,
                         struct sk_buff *skb, struct mfc_cache *cache,
                         int local)
{
        int psend = -1;
        int vif, ct;

        vif = cache->mfc_parent;
        cache->mfc_un.res.pkt++;
        cache->mfc_un.res.bytes += skb->len;

        /*
         * Wrong interface: drop packet and (maybe) send PIM assert.
         */
        if (mrt->vif_table[vif].dev != skb->dev) {
                int true_vifi;

                if (rt_is_output_route(skb_rtable(skb))) {
                        /* It is our own packet, looped back.
                         * Very complicated situation...
                         *
                         * The best workaround until routing daemons will be
                         * fixed is not to redistribute packet, if it was
                         * send through wrong interface. It means, that
                         * multicast applications WILL NOT work for
                         * (S,G), which have default multicast route pointing
                         * to wrong oif. In any case, it is not a good
                         * idea to use multicasting applications on router.
                         */
                        goto dont_forward;
                }

                cache->mfc_un.res.wrong_if++;
                true_vifi = ipmr_find_vif(mrt, skb->dev);

                if (true_vifi >= 0 && mrt->mroute_do_assert &&
                    /* pimsm uses asserts, when switching from RPT to SPT,
                     * so that we cannot check that packet arrived on an oif.
                     * It is bad, but otherwise we would need to move pretty
                     * large chunk of pimd to kernel. Ough... --ANK
                     */
                    (mrt->mroute_do_pim ||
                     cache->mfc_un.res.ttls[true_vifi] < 255) &&
                    time_after(jiffies,
                               cache->mfc_un.res.last_assert + MFC_ASSERT_THRESH)) {
                        cache->mfc_un.res.last_assert = jiffies;
                        ipmr_cache_report(mrt, skb, true_vifi, IGMPMSG_WRONGVIF);
                }
                goto dont_forward;
        }

        mrt->vif_table[vif].pkt_in++;
        mrt->vif_table[vif].bytes_in += skb->len;

        /*
         *      Forward the frame
         */
        for (ct = cache->mfc_un.res.maxvif - 1;
             ct >= cache->mfc_un.res.minvif; ct--) {
                if (ip_hdr(skb)->ttl > cache->mfc_un.res.ttls[ct]) {
                        if (psend != -1) {
                                struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);

                                if (skb2)
                                        ipmr_queue_xmit(net, mrt, skb2, cache,
                                                        psend);
                        }
                        psend = ct;
                }
        }
        if (psend != -1) {
                if (local) {
                        struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);

                        if (skb2)
                                ipmr_queue_xmit(net, mrt, skb2, cache, psend);
                } else {
                        ipmr_queue_xmit(net, mrt, skb, cache, psend);
                        return 0;
                }
        }

dont_forward:
        if (!local)
                kfree_skb(skb);
        return 0;
}

static struct mr_table *ipmr_rt_fib_lookup(struct net *net, struct sk_buff *skb)
{
        struct rtable *rt = skb_rtable(skb);
        struct iphdr *iph = ip_hdr(skb);
        struct flowi4 fl4 = {
                .daddr = iph->daddr,
                .saddr = iph->saddr,
                .flowi4_tos = RT_TOS(iph->tos),
                .flowi4_oif = rt->rt_oif,
                .flowi4_iif = rt->rt_iif,
                .flowi4_mark = rt->rt_mark,
        };
        struct mr_table *mrt;
        int err;

        err = ipmr_fib_lookup(net, &fl4, &mrt);
        if (err)
                return ERR_PTR(err);
        return mrt;
}

/*
 *      Multicast packets for forwarding arrive here
 *      Called with rcu_read_lock();
 */

int ip_mr_input(struct sk_buff *skb)
{
        struct mfc_cache *cache;
        struct net *net = dev_net(skb->dev);
        int local = skb_rtable(skb)->rt_flags & RTCF_LOCAL;
        struct mr_table *mrt;

        /* Packet is looped back after forward, it should not be
         * forwarded second time, but still can be delivered locally.
         */
        if (IPCB(skb)->flags & IPSKB_FORWARDED)
                goto dont_forward;

        mrt = ipmr_rt_fib_lookup(net, skb);
        if (IS_ERR(mrt)) {
                kfree_skb(skb);
                return PTR_ERR(mrt);
        }
        if (!local) {
                if (IPCB(skb)->opt.router_alert) {
                        if (ip_call_ra_chain(skb))
                                return 0;
                } else if (ip_hdr(skb)->protocol == IPPROTO_IGMP) {
                        /* IGMPv1 (and broken IGMPv2 implementations sort of
                         * Cisco IOS <= 11.2(8)) do not put router alert
                         * option to IGMP packets destined to routable
                         * groups. It is very bad, because it means
                         * that we can forward NO IGMP messages.
                         */
                        struct sock *mroute_sk;

                        mroute_sk = rcu_dereference(mrt->mroute_sk);
                        if (mroute_sk) {
                                nf_reset(skb);
                                raw_rcv(mroute_sk, skb);
                                return 0;
                        }
                    }
        }

        /* already under rcu_read_lock() */
        cache = ipmr_cache_find(mrt, ip_hdr(skb)->saddr, ip_hdr(skb)->daddr);

        /*
         *      No usable cache entry
         */
        if (cache == NULL) {
                int vif;

                if (local) {
                        struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
                        ip_local_deliver(skb);
                        if (skb2 == NULL)
                                return -ENOBUFS;
                        skb = skb2;
                }

                read_lock(&mrt_lock);
                vif = ipmr_find_vif(mrt, skb->dev);
                if (vif >= 0) {
                        int err2 = ipmr_cache_unresolved(mrt, vif, skb);
                        read_unlock(&mrt_lock);

                        return err2;
                }
                read_unlock(&mrt_lock);
                kfree_skb(skb);
                return -ENODEV;
        }

        read_lock(&mrt_lock);
        ip_mr_forward(net, mrt, skb, cache, local);
        read_unlock(&mrt_lock);

        if (local)
                return ip_local_deliver(skb);

        return 0;

dont_forward:
        if (local)
                return ip_local_deliver(skb);
        kfree_skb(skb);
        return 0;
}

#ifdef CONFIG_IP_PIMSM
/* called with rcu_read_lock() */
static int __pim_rcv(struct mr_table *mrt, struct sk_buff *skb,
                     unsigned int pimlen)
{
        struct net_device *reg_dev = NULL;
        struct iphdr *encap;

        encap = (struct iphdr *)(skb_transport_header(skb) + pimlen);
        /*
         * Check that:
         * a. packet is really sent to a multicast group
         * b. packet is not a NULL-REGISTER
         * c. packet is not truncated
         */
        if (!ipv4_is_multicast(encap->daddr) ||
            encap->tot_len == 0 ||
            ntohs(encap->tot_len) + pimlen > skb->len)
                return 1;

        read_lock(&mrt_lock);
        if (mrt->mroute_reg_vif_num >= 0)
                reg_dev = mrt->vif_table[mrt->mroute_reg_vif_num].dev;
        read_unlock(&mrt_lock);

        if (reg_dev == NULL)
                return 1;

        skb->mac_header = skb->network_header;
        skb_pull(skb, (u8 *)encap - skb->data);
        skb_reset_network_header(skb);
        skb->protocol = htons(ETH_P_IP);
        skb->ip_summed = CHECKSUM_NONE;
        skb->pkt_type = PACKET_HOST;

        skb_tunnel_rx(skb, reg_dev);

        netif_rx(skb);

        return NET_RX_SUCCESS;
}
#endif

#ifdef CONFIG_IP_PIMSM_V1
/*
 * Handle IGMP messages of PIMv1
 */

int pim_rcv_v1(struct sk_buff *skb)
{
        struct igmphdr *pim;
        struct net *net = dev_net(skb->dev);
        struct mr_table *mrt;

        if (!pskb_may_pull(skb, sizeof(*pim) + sizeof(struct iphdr)))
                goto drop;

        pim = igmp_hdr(skb);

        mrt = ipmr_rt_fib_lookup(net, skb);
        if (IS_ERR(mrt))
                goto drop;
        if (!mrt->mroute_do_pim ||
            pim->group != PIM_V1_VERSION || pim->code != PIM_V1_REGISTER)
                goto drop;

        if (__pim_rcv(mrt, skb, sizeof(*pim))) {
drop:
                kfree_skb(skb);
        }
        return 0;
}
#endif

#ifdef CONFIG_IP_PIMSM_V2
static int pim_rcv(struct sk_buff *skb)
{
        struct pimreghdr *pim;
        struct net *net = dev_net(skb->dev);
        struct mr_table *mrt;

        if (!pskb_may_pull(skb, sizeof(*pim) + sizeof(struct iphdr)))
                goto drop;

        pim = (struct pimreghdr *)skb_transport_header(skb);
        if (pim->type != ((PIM_VERSION << 4) | (PIM_REGISTER)) ||
            (pim->flags & PIM_NULL_REGISTER) ||
            (ip_compute_csum((void *)pim, sizeof(*pim)) != 0 &&
             csum_fold(skb_checksum(skb, 0, skb->len, 0))))
                goto drop;

        mrt = ipmr_rt_fib_lookup(net, skb);
        if (IS_ERR(mrt))
                goto drop;
        if (__pim_rcv(mrt, skb, sizeof(*pim))) {
drop:
                kfree_skb(skb);
        }
        return 0;

}
#endif

static int __ipmr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
                              struct mfc_cache *c, struct rtmsg *rtm)
{
        int ct;
        struct rtnexthop *nhp;
        u8 *b = skb_tail_pointer(skb);
        struct rtattr *mp_head;

        /* If cache is unresolved, don't try to parse IIF and OIF */
        if (c->mfc_parent >= MAXVIFS)
                return -ENOENT;

        if (VIF_EXISTS(mrt, c->mfc_parent))
                RTA_PUT(skb, RTA_IIF, 4, &mrt->vif_table[c->mfc_parent].dev->ifindex);

        mp_head = (struct rtattr *)skb_put(skb, RTA_LENGTH(0));

        for (ct = c->mfc_un.res.minvif; ct < c->mfc_un.res.maxvif; ct++) {
                if (VIF_EXISTS(mrt, ct) && c->mfc_un.res.ttls[ct] < 255) {
                        if (skb_tailroom(skb) < RTA_ALIGN(RTA_ALIGN(sizeof(*nhp)) + 4))
                                goto rtattr_failure;
                        nhp = (struct rtnexthop *)skb_put(skb, RTA_ALIGN(sizeof(*nhp)));
                        nhp->rtnh_flags = 0;
                        nhp->rtnh_hops = c->mfc_un.res.ttls[ct];
                        nhp->rtnh_ifindex = mrt->vif_table[ct].dev->ifindex;
                        nhp->rtnh_len = sizeof(*nhp);
                }
        }
        mp_head->rta_type = RTA_MULTIPATH;
        mp_head->rta_len = skb_tail_pointer(skb) - (u8 *)mp_head;
        rtm->rtm_type = RTN_MULTICAST;
        return 1;

rtattr_failure:
        nlmsg_trim(skb, b);
        return -EMSGSIZE;
}

int ipmr_get_route(struct net *net, struct sk_buff *skb,
                   __be32 saddr, __be32 daddr,
                   struct rtmsg *rtm, int nowait)
{
        struct mfc_cache *cache;
        struct mr_table *mrt;
        int err;

        mrt = ipmr_get_table(net, RT_TABLE_DEFAULT);
        if (mrt == NULL)
                return -ENOENT;

        rcu_read_lock();
        cache = ipmr_cache_find(mrt, saddr, daddr);

        if (cache == NULL) {
                struct sk_buff *skb2;
                struct iphdr *iph;
                struct net_device *dev;
                int vif = -1;

                if (nowait) {
                        rcu_read_unlock();
                        return -EAGAIN;
                }

                dev = skb->dev;
                read_lock(&mrt_lock);
                if (dev)
                        vif = ipmr_find_vif(mrt, dev);
                if (vif < 0) {
                        read_unlock(&mrt_lock);
                        rcu_read_unlock();
                        return -ENODEV;
                }
                skb2 = skb_clone(skb, GFP_ATOMIC);
                if (!skb2) {
                        read_unlock(&mrt_lock);
                        rcu_read_unlock();
                        return -ENOMEM;
                }

                skb_push(skb2, sizeof(struct iphdr));
                skb_reset_network_header(skb2);
                iph = ip_hdr(skb2);
                iph->ihl = sizeof(struct iphdr) >> 2;
                iph->saddr = saddr;
                iph->daddr = daddr;
                iph->version = 0;
                err = ipmr_cache_unresolved(mrt, vif, skb2);
                read_unlock(&mrt_lock);
                rcu_read_unlock();
                return err;
        }

        read_lock(&mrt_lock);
        if (!nowait && (rtm->rtm_flags & RTM_F_NOTIFY))
                cache->mfc_flags |= MFC_NOTIFY;
        err = __ipmr_fill_mroute(mrt, skb, cache, rtm);
        read_unlock(&mrt_lock);
        rcu_read_unlock();
        return err;
}

static int ipmr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
                            u32 pid, u32 seq, struct mfc_cache *c)
{
        struct nlmsghdr *nlh;
        struct rtmsg *rtm;

        nlh = nlmsg_put(skb, pid, seq, RTM_NEWROUTE, sizeof(*rtm), NLM_F_MULTI);
        if (nlh == NULL)
                return -EMSGSIZE;

        rtm = nlmsg_data(nlh);
        rtm->rtm_family   = RTNL_FAMILY_IPMR;
        rtm->rtm_dst_len  = 32;
        rtm->rtm_src_len  = 32;
        rtm->rtm_tos      = 0;
        rtm->rtm_table    = mrt->id;
        if (nla_put_u32(skb, RTA_TABLE, mrt->id))
                goto nla_put_failure;
        rtm->rtm_type     = RTN_MULTICAST;
        rtm->rtm_scope    = RT_SCOPE_UNIVERSE;
        rtm->rtm_protocol = RTPROT_UNSPEC;
        rtm->rtm_flags    = 0;

        if (nla_put_be32(skb, RTA_SRC, c->mfc_origin) ||
            nla_put_be32(skb, RTA_DST, c->mfc_mcastgrp))
                goto nla_put_failure;
        if (__ipmr_fill_mroute(mrt, skb, c, rtm) < 0)
                goto nla_put_failure;

        return nlmsg_end(skb, nlh);

nla_put_failure:
        nlmsg_cancel(skb, nlh);
        return -EMSGSIZE;
}

static int ipmr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct net *net = sock_net(skb->sk);
        struct mr_table *mrt;
        struct mfc_cache *mfc;
        unsigned int t = 0, s_t;
        unsigned int h = 0, s_h;
        unsigned int e = 0, s_e;

        s_t = cb->args[0];
        s_h = cb->args[1];
        s_e = cb->args[2];

        rcu_read_lock();
        ipmr_for_each_table(mrt, net) {
                if (t < s_t)
                        goto next_table;
                if (t > s_t)
                        s_h = 0;
                for (h = s_h; h < MFC_LINES; h++) {
                        list_for_each_entry_rcu(mfc, &mrt->mfc_cache_array[h], list) {
                                if (e < s_e)
                                        goto next_entry;
                                if (ipmr_fill_mroute(mrt, skb,
                                                     NETLINK_CB(cb->skb).pid,
                                                     cb->nlh->nlmsg_seq,
                                                     mfc) < 0)
                                        goto done;
next_entry:
                                e++;
                        }
                        e = s_e = 0;
                }
                s_h = 0;
next_table:
                t++;
        }
done:
        rcu_read_unlock();

        cb->args[2] = e;
        cb->args[1] = h;
        cb->args[0] = t;

        return skb->len;
}

#ifdef CONFIG_PROC_FS
/*
 *      The /proc interfaces to multicast routing :
 *      /proc/net/ip_mr_cache & /proc/net/ip_mr_vif
 */
struct ipmr_vif_iter {
        struct seq_net_private p;
        struct mr_table *mrt;
        int ct;
};

static struct vif_device *ipmr_vif_seq_idx(struct net *net,
                                           struct ipmr_vif_iter *iter,
                                           loff_t pos)
{
        struct mr_table *mrt = iter->mrt;

        for (iter->ct = 0; iter->ct < mrt->maxvif; ++iter->ct) {
                if (!VIF_EXISTS(mrt, iter->ct))
                        continue;
                if (pos-- == 0)
                        return &mrt->vif_table[iter->ct];
        }
        return NULL;
}

static void *ipmr_vif_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(mrt_lock)
{
        struct ipmr_vif_iter *iter = seq->private;
        struct net *net = seq_file_net(seq);
        struct mr_table *mrt;

        mrt = ipmr_get_table(net, RT_TABLE_DEFAULT);
        if (mrt == NULL)
                return ERR_PTR(-ENOENT);

        iter->mrt = mrt;

        read_lock(&mrt_lock);
        return *pos ? ipmr_vif_seq_idx(net, seq->private, *pos - 1)
                : SEQ_START_TOKEN;
}

static void *ipmr_vif_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct ipmr_vif_iter *iter = seq->private;
        struct net *net = seq_file_net(seq);
        struct mr_table *mrt = iter->mrt;

        ++*pos;
        if (v == SEQ_START_TOKEN)
                return ipmr_vif_seq_idx(net, iter, 0);

        while (++iter->ct < mrt->maxvif) {
                if (!VIF_EXISTS(mrt, iter->ct))
                        continue;
                return &mrt->vif_table[iter->ct];
        }
        return NULL;
}

static void ipmr_vif_seq_stop(struct seq_file *seq, void *v)
        __releases(mrt_lock)
{
        read_unlock(&mrt_lock);
}

static int ipmr_vif_seq_show(struct seq_file *seq, void *v)
{
        struct ipmr_vif_iter *iter = seq->private;
        struct mr_table *mrt = iter->mrt;

        if (v == SEQ_START_TOKEN) {
                seq_puts(seq,
                         "Interface      BytesIn  PktsIn  BytesOut PktsOut Flags Local    Remote\n");
        } else {
                const struct vif_device *vif = v;
                const char *name =  vif->dev ? vif->dev->name : "none";

                seq_printf(seq,
                           "%2Zd %-10s %8ld %7ld  %8ld %7ld %05X %08X %08X\n",
                           vif - mrt->vif_table,
                           name, vif->bytes_in, vif->pkt_in,
                           vif->bytes_out, vif->pkt_out,
                           vif->flags, vif->local, vif->remote);
        }
        return 0;
}

static const struct seq_operations ipmr_vif_seq_ops = {
        .start = ipmr_vif_seq_start,
        .next  = ipmr_vif_seq_next,
        .stop  = ipmr_vif_seq_stop,
        .show  = ipmr_vif_seq_show,
};

static int ipmr_vif_open(struct inode *inode, struct file *file)
{
        return seq_open_net(inode, file, &ipmr_vif_seq_ops,
                            sizeof(struct ipmr_vif_iter));
}

static const struct file_operations ipmr_vif_fops = {
        .owner   = THIS_MODULE,
        .open    = ipmr_vif_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release_net,
};

struct ipmr_mfc_iter {
        struct seq_net_private p;
        struct mr_table *mrt;
        struct list_head *cache;
        int ct;
};


static struct mfc_cache *ipmr_mfc_seq_idx(struct net *net,
                                          struct ipmr_mfc_iter *it, loff_t pos)
{
        struct mr_table *mrt = it->mrt;
        struct mfc_cache *mfc;

        rcu_read_lock();
        for (it->ct = 0; it->ct < MFC_LINES; it->ct++) {
                it->cache = &mrt->mfc_cache_array[it->ct];
                list_for_each_entry_rcu(mfc, it->cache, list)
                        if (pos-- == 0)
                                return mfc;
        }
        rcu_read_unlock();

        spin_lock_bh(&mfc_unres_lock);
        it->cache = &mrt->mfc_unres_queue;
        list_for_each_entry(mfc, it->cache, list)
                if (pos-- == 0)
                        return mfc;
        spin_unlock_bh(&mfc_unres_lock);

        it->cache = NULL;
        return NULL;
}


static void *ipmr_mfc_seq_start(struct seq_file *seq, loff_t *pos)
{
        struct ipmr_mfc_iter *it = seq->private;
        struct net *net = seq_file_net(seq);
        struct mr_table *mrt;

        mrt = ipmr_get_table(net, RT_TABLE_DEFAULT);
        if (mrt == NULL)
                return ERR_PTR(-ENOENT);

        it->mrt = mrt;
        it->cache = NULL;
        it->ct = 0;
        return *pos ? ipmr_mfc_seq_idx(net, seq->private, *pos - 1)
                : SEQ_START_TOKEN;
}

static void *ipmr_mfc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct mfc_cache *mfc = v;
        struct ipmr_mfc_iter *it = seq->private;
        struct net *net = seq_file_net(seq);
        struct mr_table *mrt = it->mrt;

        ++*pos;

        if (v == SEQ_START_TOKEN)
                return ipmr_mfc_seq_idx(net, seq->private, 0);

        if (mfc->list.next != it->cache)
                return list_entry(mfc->list.next, struct mfc_cache, list);

        if (it->cache == &mrt->mfc_unres_queue)
                goto end_of_list;

        BUG_ON(it->cache != &mrt->mfc_cache_array[it->ct]);

        while (++it->ct < MFC_LINES) {
                it->cache = &mrt->mfc_cache_array[it->ct];
                if (list_empty(it->cache))
                        continue;
                return list_first_entry(it->cache, struct mfc_cache, list);
        }

        /* exhausted cache_array, show unresolved */
        rcu_read_unlock();
        it->cache = &mrt->mfc_unres_queue;
        it->ct = 0;

        spin_lock_bh(&mfc_unres_lock);
        if (!list_empty(it->cache))
                return list_first_entry(it->cache, struct mfc_cache, list);

end_of_list:
        spin_unlock_bh(&mfc_unres_lock);
        it->cache = NULL;

        return NULL;
}

static void ipmr_mfc_seq_stop(struct seq_file *seq, void *v)
{
        struct ipmr_mfc_iter *it = seq->private;
        struct mr_table *mrt = it->mrt;

        if (it->cache == &mrt->mfc_unres_queue)
                spin_unlock_bh(&mfc_unres_lock);
        else if (it->cache == &mrt->mfc_cache_array[it->ct])
                rcu_read_unlock();
}

static int ipmr_mfc_seq_show(struct seq_file *seq, void *v)
{
        int n;

        if (v == SEQ_START_TOKEN) {
                seq_puts(seq,
                 "Group    Origin   Iif     Pkts    Bytes    Wrong Oifs\n");
        } else {
                const struct mfc_cache *mfc = v;
                const struct ipmr_mfc_iter *it = seq->private;
                const struct mr_table *mrt = it->mrt;

                seq_printf(seq, "%08X %08X %-3hd",
                           (__force u32) mfc->mfc_mcastgrp,
                           (__force u32) mfc->mfc_origin,
                           mfc->mfc_parent);

                if (it->cache != &mrt->mfc_unres_queue) {
                        seq_printf(seq, " %8lu %8lu %8lu",
                                   mfc->mfc_un.res.pkt,
                                   mfc->mfc_un.res.bytes,
                                   mfc->mfc_un.res.wrong_if);
                        for (n = mfc->mfc_un.res.minvif;
                             n < mfc->mfc_un.res.maxvif; n++) {
                                if (VIF_EXISTS(mrt, n) &&
                                    mfc->mfc_un.res.ttls[n] < 255)
                                        seq_printf(seq,
                                           " %2d:%-3d",
                                           n, mfc->mfc_un.res.ttls[n]);
                        }
                } else {
                        /* unresolved mfc_caches don't contain
                         * pkt, bytes and wrong_if values
                         */
                        seq_printf(seq, " %8lu %8lu %8lu", 0ul, 0ul, 0ul);
                }
                seq_putc(seq, '\n');
        }
        return 0;
}

static const struct seq_operations ipmr_mfc_seq_ops = {
        .start = ipmr_mfc_seq_start,
        .next  = ipmr_mfc_seq_next,
        .stop  = ipmr_mfc_seq_stop,
        .show  = ipmr_mfc_seq_show,
};

static int ipmr_mfc_open(struct inode *inode, struct file *file)
{
        return seq_open_net(inode, file, &ipmr_mfc_seq_ops,
                            sizeof(struct ipmr_mfc_iter));
}

static const struct file_operations ipmr_mfc_fops = {
        .owner   = THIS_MODULE,
        .open    = ipmr_mfc_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release_net,
};
#endif

#ifdef CONFIG_IP_PIMSM_V2
static const struct net_protocol pim_protocol = {
        .handler        =       pim_rcv,
        .netns_ok       =       1,
};
#endif


/*
 *      Setup for IP multicast routing
 */
static int __net_init ipmr_net_init(struct net *net)
{
        int err;

        err = ipmr_rules_init(net);
        if (err < 0)
                goto fail;

#ifdef CONFIG_PROC_FS
        err = -ENOMEM;
        if (!proc_net_fops_create(net, "ip_mr_vif", 0, &ipmr_vif_fops))
                goto proc_vif_fail;
        if (!proc_net_fops_create(net, "ip_mr_cache", 0, &ipmr_mfc_fops))
                goto proc_cache_fail;
#endif
        return 0;

#ifdef CONFIG_PROC_FS
proc_cache_fail:
        proc_net_remove(net, "ip_mr_vif");
proc_vif_fail:
        ipmr_rules_exit(net);
#endif
fail:
        return err;
}

static void __net_exit ipmr_net_exit(struct net *net)
{
#ifdef CONFIG_PROC_FS
        proc_net_remove(net, "ip_mr_cache");
        proc_net_remove(net, "ip_mr_vif");
#endif
        ipmr_rules_exit(net);
}

static struct pernet_operations ipmr_net_ops = {
        .init = ipmr_net_init,
        .exit = ipmr_net_exit,
};

int __init ip_mr_init(void)
{
        int err;

        mrt_cachep = kmem_cache_create("ip_mrt_cache",
                                       sizeof(struct mfc_cache),
                                       0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
                                       NULL);
        if (!mrt_cachep)
                return -ENOMEM;

        err = register_pernet_subsys(&ipmr_net_ops);
        if (err)
                goto reg_pernet_fail;

        err = register_netdevice_notifier(&ip_mr_notifier);
        if (err)
                goto reg_notif_fail;
#ifdef CONFIG_IP_PIMSM_V2
        if (inet_add_protocol(&pim_protocol, IPPROTO_PIM) < 0) {
                pr_err("%s: can't add PIM protocol\n", __func__);
                err = -EAGAIN;
                goto add_proto_fail;
        }
#endif
        rtnl_register(RTNL_FAMILY_IPMR, RTM_GETROUTE,
                      NULL, ipmr_rtm_dumproute, NULL);
        return 0;

#ifdef CONFIG_IP_PIMSM_V2
add_proto_fail:
        unregister_netdevice_notifier(&ip_mr_notifier);
#endif
reg_notif_fail:
        unregister_pernet_subsys(&ipmr_net_ops);
reg_pernet_fail:
        kmem_cache_destroy(mrt_cachep);
        return err;
}