// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
 * Copyright © CC Computer Consultants GmbH, 2007 - 2008
 *
 * This is a replacement of the old ipt_recent module, which carried the
 * following copyright notice:
 *
 * Author: Stephen Frost <sfrost@snowman.net>
 * Copyright 2002-2003, Stephen Frost, 2.5.x port by laforge@netfilter.org
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/bitops.h>
#include <linux/skbuff.h>
#include <linux/inet.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_recent.h>

MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("Xtables: \"recently-seen\" host matching");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_recent");
MODULE_ALIAS("ip6t_recent");

static unsigned int ip_list_tot __read_mostly = 100;
static unsigned int ip_list_hash_size __read_mostly;
static unsigned int ip_list_perms __read_mostly = 0644;
static unsigned int ip_list_uid __read_mostly;
static unsigned int ip_list_gid __read_mostly;
module_param(ip_list_tot, uint, 0400);
module_param(ip_list_hash_size, uint, 0400);
module_param(ip_list_perms, uint, 0400);
module_param(ip_list_uid, uint, 0644);
module_param(ip_list_gid, uint, 0644);
MODULE_PARM_DESC(ip_list_tot, "number of IPs to remember per list");
MODULE_PARM_DESC(ip_list_hash_size, "size of hash table used to look up IPs");
MODULE_PARM_DESC(ip_list_perms, "permissions on /proc/net/xt_recent/* files");
MODULE_PARM_DESC(ip_list_uid, "default owner of /proc/net/xt_recent/* files");
MODULE_PARM_DESC(ip_list_gid, "default owning group of /proc/net/xt_recent/* files");

/* retained for backwards compatibility */
static unsigned int ip_pkt_list_tot __read_mostly;
module_param(ip_pkt_list_tot, uint, 0400);
MODULE_PARM_DESC(ip_pkt_list_tot, "number of packets per IP address to remember (max. 65535)");

#define XT_RECENT_MAX_NSTAMPS   65536

struct recent_entry {
        struct list_head        list;
        struct list_head        lru_list;
        union nf_inet_addr      addr;
        u_int16_t               family;
        u_int8_t                ttl;
        u_int16_t               index;
        u_int16_t               nstamps;
        unsigned long           stamps[];
};

struct recent_table {
        struct list_head        list;
        char                    name[XT_RECENT_NAME_LEN];
        union nf_inet_addr      mask;
        unsigned int            refcnt;
        unsigned int            entries;
        u_int16_t               nstamps_max_mask;
        struct list_head        lru_list;
        struct list_head        iphash[];
};

struct recent_net {
        struct list_head        tables;
#ifdef CONFIG_PROC_FS
        struct proc_dir_entry   *xt_recent;
#endif
};

static unsigned int recent_net_id __read_mostly;

static inline struct recent_net *recent_pernet(struct net *net)
{
        return net_generic(net, recent_net_id);
}

static DEFINE_SPINLOCK(recent_lock);
static DEFINE_MUTEX(recent_mutex);

#ifdef CONFIG_PROC_FS
static const struct proc_ops recent_mt_proc_ops;
#endif

static u_int32_t hash_rnd __read_mostly;

static inline unsigned int recent_entry_hash4(const union nf_inet_addr *addr)
{
        return jhash_1word((__force u32)addr->ip, hash_rnd) &
               (ip_list_hash_size - 1);
}

static inline unsigned int recent_entry_hash6(const union nf_inet_addr *addr)
{
        return jhash2((u32 *)addr->ip6, ARRAY_SIZE(addr->ip6), hash_rnd) &
               (ip_list_hash_size - 1);
}

static struct recent_entry *
recent_entry_lookup(const struct recent_table *table,
                    const union nf_inet_addr *addrp, u_int16_t family,
                    u_int8_t ttl)
{
        struct recent_entry *e;
        unsigned int h;

        if (family == NFPROTO_IPV4)
                h = recent_entry_hash4(addrp);
        else
                h = recent_entry_hash6(addrp);

        list_for_each_entry(e, &table->iphash[h], list)
                if (e->family == family &&
                    memcmp(&e->addr, addrp, sizeof(e->addr)) == 0 &&
                    (ttl == e->ttl || ttl == 0 || e->ttl == 0))
                        return e;
        return NULL;
}

static void recent_entry_remove(struct recent_table *t, struct recent_entry *e)
{
        list_del(&e->list);
        list_del(&e->lru_list);
        kfree(e);
        t->entries--;
}

/*
 * Drop entries with timestamps older then 'time'.
 */
static void recent_entry_reap(struct recent_table *t, unsigned long time,
                              struct recent_entry *working, bool update)
{
        struct recent_entry *e;

        /*
         * The head of the LRU list is always the oldest entry.
         */
        e = list_entry(t->lru_list.next, struct recent_entry, lru_list);

        /*
         * Do not reap the entry which are going to be updated.
         */
        if (e == working && update)
                return;

        /*
         * The last time stamp is the most recent.
         */
        if (time_after(time, e->stamps[e->index-1]))
                recent_entry_remove(t, e);
}

static struct recent_entry *
recent_entry_init(struct recent_table *t, const union nf_inet_addr *addr,
                  u_int16_t family, u_int8_t ttl)
{
        struct recent_entry *e;
        unsigned int nstamps_max = t->nstamps_max_mask;

        if (t->entries >= ip_list_tot) {
                e = list_entry(t->lru_list.next, struct recent_entry, lru_list);
                recent_entry_remove(t, e);
        }

        nstamps_max += 1;
        e = kmalloc_flex(*e, stamps, nstamps_max, GFP_ATOMIC);
        if (e == NULL)
                return NULL;
        memcpy(&e->addr, addr, sizeof(e->addr));
        e->ttl       = ttl;
        e->stamps[0] = jiffies;
        e->nstamps   = 1;
        e->index     = 1;
        e->family    = family;
        if (family == NFPROTO_IPV4)
                list_add_tail(&e->list, &t->iphash[recent_entry_hash4(addr)]);
        else
                list_add_tail(&e->list, &t->iphash[recent_entry_hash6(addr)]);
        list_add_tail(&e->lru_list, &t->lru_list);
        t->entries++;
        return e;
}

static void recent_entry_update(struct recent_table *t, struct recent_entry *e)
{
        e->index &= t->nstamps_max_mask;
        e->stamps[e->index++] = jiffies;
        if (e->index > e->nstamps)
                e->nstamps = e->index;
        list_move_tail(&e->lru_list, &t->lru_list);
}

static struct recent_table *recent_table_lookup(struct recent_net *recent_net,
                                                const char *name)
{
        struct recent_table *t;

        list_for_each_entry(t, &recent_net->tables, list)
                if (!strcmp(t->name, name))
                        return t;
        return NULL;
}

static void recent_table_flush(struct recent_table *t)
{
        struct recent_entry *e, *next;
        unsigned int i;

        for (i = 0; i < ip_list_hash_size; i++)
                list_for_each_entry_safe(e, next, &t->iphash[i], list)
                        recent_entry_remove(t, e);
}

static bool
recent_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
        struct net *net = xt_net(par);
        struct recent_net *recent_net = recent_pernet(net);
        const struct xt_recent_mtinfo_v1 *info = par->matchinfo;
        struct recent_table *t;
        struct recent_entry *e;
        union nf_inet_addr addr = {}, addr_mask;
        u_int8_t ttl;
        bool ret = info->invert;

        if (xt_family(par) == NFPROTO_IPV4) {
                const struct iphdr *iph = ip_hdr(skb);

                if (info->side == XT_RECENT_DEST)
                        addr.ip = iph->daddr;
                else
                        addr.ip = iph->saddr;

                ttl = iph->ttl;
        } else {
                const struct ipv6hdr *iph = ipv6_hdr(skb);

                if (info->side == XT_RECENT_DEST)
                        memcpy(&addr.in6, &iph->daddr, sizeof(addr.in6));
                else
                        memcpy(&addr.in6, &iph->saddr, sizeof(addr.in6));

                ttl = iph->hop_limit;
        }

        /* use TTL as seen before forwarding */
        if (xt_out(par) != NULL &&
            (!skb->sk || !net_eq(net, sock_net(skb->sk))))
                ttl++;

        spin_lock_bh(&recent_lock);
        t = recent_table_lookup(recent_net, info->name);

        nf_inet_addr_mask(&addr, &addr_mask, &t->mask);

        e = recent_entry_lookup(t, &addr_mask, xt_family(par),
                                (info->check_set & XT_RECENT_TTL) ? ttl : 0);
        if (e == NULL) {
                if (!(info->check_set & XT_RECENT_SET))
                        goto out;
                e = recent_entry_init(t, &addr_mask, xt_family(par), ttl);
                if (e == NULL)
                        par->hotdrop = true;
                ret = !ret;
                goto out;
        }

        if (info->check_set & XT_RECENT_SET)
                ret = !ret;
        else if (info->check_set & XT_RECENT_REMOVE) {
                recent_entry_remove(t, e);
                ret = !ret;
        } else if (info->check_set & (XT_RECENT_CHECK | XT_RECENT_UPDATE)) {
                unsigned long time = jiffies - info->seconds * HZ;
                unsigned int i, hits = 0;

                for (i = 0; i < e->nstamps; i++) {
                        if (info->seconds && time_after(time, e->stamps[i]))
                                continue;
                        if (!info->hit_count || ++hits >= info->hit_count) {
                                ret = !ret;
                                break;
                        }
                }

                /* info->seconds must be non-zero */
                if (info->check_set & XT_RECENT_REAP)
                        recent_entry_reap(t, time, e,
                                info->check_set & XT_RECENT_UPDATE && ret);
        }

        if (info->check_set & XT_RECENT_SET ||
            (info->check_set & XT_RECENT_UPDATE && ret)) {
                recent_entry_update(t, e);
                e->ttl = ttl;
        }
out:
        spin_unlock_bh(&recent_lock);
        return ret;
}

static void recent_table_free(void *addr)
{
        kvfree(addr);
}

static int recent_mt_check(const struct xt_mtchk_param *par,
                           const struct xt_recent_mtinfo_v1 *info)
{
        struct recent_net *recent_net = recent_pernet(par->net);
        struct recent_table *t;
#ifdef CONFIG_PROC_FS
        struct proc_dir_entry *pde;
        kuid_t uid;
        kgid_t gid;
#endif
        unsigned int nstamp_mask;
        unsigned int i;
        int ret = -EINVAL;

        net_get_random_once(&hash_rnd, sizeof(hash_rnd));

        if (info->check_set & ~XT_RECENT_VALID_FLAGS) {
                pr_info_ratelimited("Unsupported userspace flags (%08x)\n",
                                    info->check_set);
                return -EINVAL;
        }
        if (hweight8(info->check_set &
                     (XT_RECENT_SET | XT_RECENT_REMOVE |
                      XT_RECENT_CHECK | XT_RECENT_UPDATE)) != 1)
                return -EINVAL;
        if ((info->check_set & (XT_RECENT_SET | XT_RECENT_REMOVE)) &&
            (info->seconds || info->hit_count ||
            (info->check_set & XT_RECENT_MODIFIERS)))
                return -EINVAL;
        if ((info->check_set & XT_RECENT_REAP) && !info->seconds)
                return -EINVAL;
        if (info->hit_count >= XT_RECENT_MAX_NSTAMPS) {
                pr_info_ratelimited("hitcount (%u) is larger than allowed maximum (%u)\n",
                                    info->hit_count, XT_RECENT_MAX_NSTAMPS - 1);
                return -EINVAL;
        }
        ret = xt_check_proc_name(info->name, sizeof(info->name));
        if (ret)
                return ret;

        if (ip_pkt_list_tot && info->hit_count < ip_pkt_list_tot)
                nstamp_mask = roundup_pow_of_two(ip_pkt_list_tot) - 1;
        else if (info->hit_count)
                nstamp_mask = roundup_pow_of_two(info->hit_count) - 1;
        else
                nstamp_mask = 32 - 1;

        mutex_lock(&recent_mutex);
        t = recent_table_lookup(recent_net, info->name);
        if (t != NULL) {
                if (nstamp_mask > t->nstamps_max_mask) {
                        spin_lock_bh(&recent_lock);
                        recent_table_flush(t);
                        t->nstamps_max_mask = nstamp_mask;
                        spin_unlock_bh(&recent_lock);
                }

                t->refcnt++;
                ret = 0;
                goto out;
        }

        t = kvzalloc_flex(*t, iphash, ip_list_hash_size);
        if (t == NULL) {
                ret = -ENOMEM;
                goto out;
        }
        t->refcnt = 1;
        t->nstamps_max_mask = nstamp_mask;

        memcpy(&t->mask, &info->mask, sizeof(t->mask));
        strcpy(t->name, info->name);
        INIT_LIST_HEAD(&t->lru_list);
        for (i = 0; i < ip_list_hash_size; i++)
                INIT_LIST_HEAD(&t->iphash[i]);
#ifdef CONFIG_PROC_FS
        uid = make_kuid(&init_user_ns, ip_list_uid);
        gid = make_kgid(&init_user_ns, ip_list_gid);
        if (!uid_valid(uid) || !gid_valid(gid)) {
                recent_table_free(t);
                ret = -EINVAL;
                goto out;
        }
        pde = proc_create_data(t->name, ip_list_perms, recent_net->xt_recent,
                               &recent_mt_proc_ops, t);
        if (pde == NULL) {
                recent_table_free(t);
                ret = -ENOMEM;
                goto out;
        }
        proc_set_user(pde, uid, gid);
#endif
        spin_lock_bh(&recent_lock);
        list_add_tail(&t->list, &recent_net->tables);
        spin_unlock_bh(&recent_lock);
        ret = 0;
out:
        mutex_unlock(&recent_mutex);
        return ret;
}

static int recent_mt_check_v0(const struct xt_mtchk_param *par)
{
        const struct xt_recent_mtinfo_v0 *info_v0 = par->matchinfo;
        struct xt_recent_mtinfo_v1 info_v1;

        /* Copy revision 0 structure to revision 1 */
        memcpy(&info_v1, info_v0, sizeof(struct xt_recent_mtinfo));
        /* Set default mask to ensure backward compatible behaviour */
        memset(info_v1.mask.all, 0xFF, sizeof(info_v1.mask.all));

        return recent_mt_check(par, &info_v1);
}

static int recent_mt_check_v1(const struct xt_mtchk_param *par)
{
        return recent_mt_check(par, par->matchinfo);
}

static void recent_mt_destroy(const struct xt_mtdtor_param *par)
{
        struct recent_net *recent_net = recent_pernet(par->net);
        const struct xt_recent_mtinfo_v1 *info = par->matchinfo;
        struct recent_table *t;

        mutex_lock(&recent_mutex);
        t = recent_table_lookup(recent_net, info->name);
        if (--t->refcnt == 0) {
                spin_lock_bh(&recent_lock);
                list_del(&t->list);
                spin_unlock_bh(&recent_lock);
#ifdef CONFIG_PROC_FS
                if (recent_net->xt_recent != NULL)
                        remove_proc_entry(t->name, recent_net->xt_recent);
#endif
                recent_table_flush(t);
                recent_table_free(t);
        }
        mutex_unlock(&recent_mutex);
}

#ifdef CONFIG_PROC_FS
struct recent_iter_state {
        const struct recent_table *table;
        unsigned int            bucket;
};

static void *recent_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(recent_lock)
{
        struct recent_iter_state *st = seq->private;
        const struct recent_table *t = st->table;
        struct recent_entry *e;
        loff_t p = *pos;

        spin_lock_bh(&recent_lock);

        for (st->bucket = 0; st->bucket < ip_list_hash_size; st->bucket++)
                list_for_each_entry(e, &t->iphash[st->bucket], list)
                        if (p-- == 0)
                                return e;
        return NULL;
}

static void *recent_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct recent_iter_state *st = seq->private;
        const struct recent_table *t = st->table;
        const struct recent_entry *e = v;
        const struct list_head *head = e->list.next;

        (*pos)++;
        while (head == &t->iphash[st->bucket]) {
                if (++st->bucket >= ip_list_hash_size)
                        return NULL;
                head = t->iphash[st->bucket].next;
        }
        return list_entry(head, struct recent_entry, list);
}

static void recent_seq_stop(struct seq_file *s, void *v)
        __releases(recent_lock)
{
        spin_unlock_bh(&recent_lock);
}

static int recent_seq_show(struct seq_file *seq, void *v)
{
        const struct recent_entry *e = v;
        struct recent_iter_state *st = seq->private;
        const struct recent_table *t = st->table;
        unsigned int i;

        i = (e->index - 1) & t->nstamps_max_mask;

        if (e->family == NFPROTO_IPV4)
                seq_printf(seq, "src=%pI4 ttl: %u last_seen: %lu oldest_pkt: %u",
                           &e->addr.ip, e->ttl, e->stamps[i], e->index);
        else
                seq_printf(seq, "src=%pI6 ttl: %u last_seen: %lu oldest_pkt: %u",
                           &e->addr.in6, e->ttl, e->stamps[i], e->index);
        for (i = 0; i < e->nstamps; i++)
                seq_printf(seq, "%s %lu", i ? "," : "", e->stamps[i]);
        seq_putc(seq, '\n');
        return 0;
}

static const struct seq_operations recent_seq_ops = {
        .start          = recent_seq_start,
        .next           = recent_seq_next,
        .stop           = recent_seq_stop,
        .show           = recent_seq_show,
};

static int recent_seq_open(struct inode *inode, struct file *file)
{
        struct recent_iter_state *st;

        st = __seq_open_private(file, &recent_seq_ops, sizeof(*st));
        if (st == NULL)
                return -ENOMEM;

        st->table    = pde_data(inode);
        return 0;
}

static ssize_t
recent_mt_proc_write(struct file *file, const char __user *input,
                     size_t size, loff_t *loff)
{
        struct recent_table *t = pde_data(file_inode(file));
        struct recent_entry *e;
        char buf[sizeof("+b335:1d35:1e55:dead:c0de:1715:255.255.255.255")];
        const char *c = buf;
        union nf_inet_addr addr = {};
        u_int16_t family;
        bool add, succ;

        if (size == 0)
                return 0;
        if (size > sizeof(buf))
                size = sizeof(buf);
        if (copy_from_user(buf, input, size) != 0)
                return -EFAULT;

        /* Strict protocol! */
        if (*loff != 0)
                return -ESPIPE;
        switch (*c) {
        case '/': /* flush table */
                spin_lock_bh(&recent_lock);
                recent_table_flush(t);
                spin_unlock_bh(&recent_lock);
                return size;
        case '-': /* remove address */
                add = false;
                break;
        case '+': /* add address */
                add = true;
                break;
        default:
                pr_info_ratelimited("Need \"+ip\", \"-ip\" or \"/\"\n");
                return -EINVAL;
        }

        ++c;
        --size;
        if (strnchr(c, size, ':') != NULL) {
                family = NFPROTO_IPV6;
                succ   = in6_pton(c, size, (void *)&addr, '\n', NULL);
        } else {
                family = NFPROTO_IPV4;
                succ   = in4_pton(c, size, (void *)&addr, '\n', NULL);
        }

        if (!succ)
                return -EINVAL;

        spin_lock_bh(&recent_lock);
        e = recent_entry_lookup(t, &addr, family, 0);
        if (e == NULL) {
                if (add)
                        recent_entry_init(t, &addr, family, 0);
        } else {
                if (add)
                        recent_entry_update(t, e);
                else
                        recent_entry_remove(t, e);
        }
        spin_unlock_bh(&recent_lock);
        /* Note we removed one above */
        *loff += size + 1;
        return size + 1;
}

static const struct proc_ops recent_mt_proc_ops = {
        .proc_open      = recent_seq_open,
        .proc_read      = seq_read,
        .proc_write     = recent_mt_proc_write,
        .proc_release   = seq_release_private,
        .proc_lseek     = seq_lseek,
};

static int __net_init recent_proc_net_init(struct net *net)
{
        struct recent_net *recent_net = recent_pernet(net);

        recent_net->xt_recent = proc_mkdir("xt_recent", net->proc_net);
        if (!recent_net->xt_recent)
                return -ENOMEM;
        return 0;
}

static void __net_exit recent_proc_net_exit(struct net *net)
{
        struct recent_net *recent_net = recent_pernet(net);
        struct recent_table *t;

        /* recent_net_exit() is called before recent_mt_destroy(). Make sure
         * that the parent xt_recent proc entry is empty before trying to
         * remove it.
         */
        spin_lock_bh(&recent_lock);
        list_for_each_entry(t, &recent_net->tables, list)
                remove_proc_entry(t->name, recent_net->xt_recent);

        recent_net->xt_recent = NULL;
        spin_unlock_bh(&recent_lock);

        remove_proc_entry("xt_recent", net->proc_net);
}
#else
static inline int recent_proc_net_init(struct net *net)
{
        return 0;
}

static inline void recent_proc_net_exit(struct net *net)
{
}
#endif /* CONFIG_PROC_FS */

static int __net_init recent_net_init(struct net *net)
{
        struct recent_net *recent_net = recent_pernet(net);

        INIT_LIST_HEAD(&recent_net->tables);
        return recent_proc_net_init(net);
}

static void __net_exit recent_net_exit(struct net *net)
{
        recent_proc_net_exit(net);
}

static struct pernet_operations recent_net_ops = {
        .init   = recent_net_init,
        .exit   = recent_net_exit,
        .id     = &recent_net_id,
        .size   = sizeof(struct recent_net),
};

static struct xt_match recent_mt_reg[] __read_mostly = {
        {
                .name       = "recent",
                .revision   = 0,
                .family     = NFPROTO_IPV4,
                .match      = recent_mt,
                .matchsize  = sizeof(struct xt_recent_mtinfo),
                .checkentry = recent_mt_check_v0,
                .destroy    = recent_mt_destroy,
                .me         = THIS_MODULE,
        },
        {
                .name       = "recent",
                .revision   = 0,
                .family     = NFPROTO_IPV6,
                .match      = recent_mt,
                .matchsize  = sizeof(struct xt_recent_mtinfo),
                .checkentry = recent_mt_check_v0,
                .destroy    = recent_mt_destroy,
                .me         = THIS_MODULE,
        },
        {
                .name       = "recent",
                .revision   = 1,
                .family     = NFPROTO_IPV4,
                .match      = recent_mt,
                .matchsize  = sizeof(struct xt_recent_mtinfo_v1),
                .checkentry = recent_mt_check_v1,
                .destroy    = recent_mt_destroy,
                .me         = THIS_MODULE,
        },
        {
                .name       = "recent",
                .revision   = 1,
                .family     = NFPROTO_IPV6,
                .match      = recent_mt,
                .matchsize  = sizeof(struct xt_recent_mtinfo_v1),
                .checkentry = recent_mt_check_v1,
                .destroy    = recent_mt_destroy,
                .me         = THIS_MODULE,
        }
};

static int __init recent_mt_init(void)
{
        int err;

        BUILD_BUG_ON_NOT_POWER_OF_2(XT_RECENT_MAX_NSTAMPS);

        if (!ip_list_tot || ip_pkt_list_tot >= XT_RECENT_MAX_NSTAMPS)
                return -EINVAL;
        ip_list_hash_size = 1 << fls(ip_list_tot);

        err = register_pernet_subsys(&recent_net_ops);
        if (err)
                return err;
        err = xt_register_matches(recent_mt_reg, ARRAY_SIZE(recent_mt_reg));
        if (err)
                unregister_pernet_subsys(&recent_net_ops);
        return err;
}

static void __exit recent_mt_exit(void)
{
        xt_unregister_matches(recent_mt_reg, ARRAY_SIZE(recent_mt_reg));
        unregister_pernet_subsys(&recent_net_ops);
}

module_init(recent_mt_init);
module_exit(recent_mt_exit);