/*
 * x_tables core - Backend for {ip,ip6,arp}_tables
 *
 * Copyright (C) 2006-2006 Harald Welte <laforge@netfilter.org>
 *
 * Based on existing ip_tables code which is
 *   Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 *   Copyright (C) 2000-2005 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/kernel.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <linux/mutex.h>
#include <linux/mm.h>
#include <net/net_namespace.h>

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


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");

#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))

struct compat_delta {
        struct compat_delta *next;
        unsigned int offset;
        short delta;
};

struct xt_af {
        struct mutex mutex;
        struct list_head match;
        struct list_head target;
#ifdef CONFIG_COMPAT
        struct mutex compat_mutex;
        struct compat_delta *compat_offsets;
#endif
};

static struct xt_af *xt;

#ifdef DEBUG_IP_FIREWALL_USER
#define duprintf(format, args...) printk(format , ## args)
#else
#define duprintf(format, args...)
#endif

static const char *const xt_prefix[NFPROTO_NUMPROTO] = {
        [NFPROTO_UNSPEC] = "x",
        [NFPROTO_IPV4]   = "ip",
        [NFPROTO_ARP]    = "arp",
        [NFPROTO_BRIDGE] = "eb",
        [NFPROTO_IPV6]   = "ip6",
};

/* Registration hooks for targets. */
int
xt_register_target(struct xt_target *target)
{
        u_int8_t af = target->family;
        int ret;

        ret = mutex_lock_interruptible(&xt[af].mutex);
        if (ret != 0)
                return ret;
        list_add(&target->list, &xt[af].target);
        mutex_unlock(&xt[af].mutex);
        return ret;
}
EXPORT_SYMBOL(xt_register_target);

void
xt_unregister_target(struct xt_target *target)
{
        u_int8_t af = target->family;

        mutex_lock(&xt[af].mutex);
        list_del(&target->list);
        mutex_unlock(&xt[af].mutex);
}
EXPORT_SYMBOL(xt_unregister_target);

int
xt_register_targets(struct xt_target *target, unsigned int n)
{
        unsigned int i;
        int err = 0;

        for (i = 0; i < n; i++) {
                err = xt_register_target(&target[i]);
                if (err)
                        goto err;
        }
        return err;

err:
        if (i > 0)
                xt_unregister_targets(target, i);
        return err;
}
EXPORT_SYMBOL(xt_register_targets);

void
xt_unregister_targets(struct xt_target *target, unsigned int n)
{
        unsigned int i;

        for (i = 0; i < n; i++)
                xt_unregister_target(&target[i]);
}
EXPORT_SYMBOL(xt_unregister_targets);

int
xt_register_match(struct xt_match *match)
{
        u_int8_t af = match->family;
        int ret;

        ret = mutex_lock_interruptible(&xt[af].mutex);
        if (ret != 0)
                return ret;

        list_add(&match->list, &xt[af].match);
        mutex_unlock(&xt[af].mutex);

        return ret;
}
EXPORT_SYMBOL(xt_register_match);

void
xt_unregister_match(struct xt_match *match)
{
        u_int8_t af = match->family;

        mutex_lock(&xt[af].mutex);
        list_del(&match->list);
        mutex_unlock(&xt[af].mutex);
}
EXPORT_SYMBOL(xt_unregister_match);

int
xt_register_matches(struct xt_match *match, unsigned int n)
{
        unsigned int i;
        int err = 0;

        for (i = 0; i < n; i++) {
                err = xt_register_match(&match[i]);
                if (err)
                        goto err;
        }
        return err;

err:
        if (i > 0)
                xt_unregister_matches(match, i);
        return err;
}
EXPORT_SYMBOL(xt_register_matches);

void
xt_unregister_matches(struct xt_match *match, unsigned int n)
{
        unsigned int i;

        for (i = 0; i < n; i++)
                xt_unregister_match(&match[i]);
}
EXPORT_SYMBOL(xt_unregister_matches);


/*
 * These are weird, but module loading must not be done with mutex
 * held (since they will register), and we have to have a single
 * function to use try_then_request_module().
 */

/* Find match, grabs ref.  Returns ERR_PTR() on error. */
struct xt_match *xt_find_match(u8 af, const char *name, u8 revision)
{
        struct xt_match *m;
        int err = 0;

        if (mutex_lock_interruptible(&xt[af].mutex) != 0)
                return ERR_PTR(-EINTR);

        list_for_each_entry(m, &xt[af].match, list) {
                if (strcmp(m->name, name) == 0) {
                        if (m->revision == revision) {
                                if (try_module_get(m->me)) {
                                        mutex_unlock(&xt[af].mutex);
                                        return m;
                                }
                        } else
                                err = -EPROTOTYPE; /* Found something. */
                }
        }
        mutex_unlock(&xt[af].mutex);

        if (af != NFPROTO_UNSPEC)
                /* Try searching again in the family-independent list */
                return xt_find_match(NFPROTO_UNSPEC, name, revision);

        return ERR_PTR(err);
}
EXPORT_SYMBOL(xt_find_match);

/* Find target, grabs ref.  Returns ERR_PTR() on error. */
struct xt_target *xt_find_target(u8 af, const char *name, u8 revision)
{
        struct xt_target *t;
        int err = 0;

        if (mutex_lock_interruptible(&xt[af].mutex) != 0)
                return ERR_PTR(-EINTR);

        list_for_each_entry(t, &xt[af].target, list) {
                if (strcmp(t->name, name) == 0) {
                        if (t->revision == revision) {
                                if (try_module_get(t->me)) {
                                        mutex_unlock(&xt[af].mutex);
                                        return t;
                                }
                        } else
                                err = -EPROTOTYPE; /* Found something. */
                }
        }
        mutex_unlock(&xt[af].mutex);

        if (af != NFPROTO_UNSPEC)
                /* Try searching again in the family-independent list */
                return xt_find_target(NFPROTO_UNSPEC, name, revision);

        return ERR_PTR(err);
}
EXPORT_SYMBOL(xt_find_target);

struct xt_target *xt_request_find_target(u8 af, const char *name, u8 revision)
{
        struct xt_target *target;

        target = try_then_request_module(xt_find_target(af, name, revision),
                                         "%st_%s", xt_prefix[af], name);
        if (IS_ERR(target) || !target)
                return NULL;
        return target;
}
EXPORT_SYMBOL_GPL(xt_request_find_target);

static int match_revfn(u8 af, const char *name, u8 revision, int *bestp)
{
        const struct xt_match *m;
        int have_rev = 0;

        list_for_each_entry(m, &xt[af].match, list) {
                if (strcmp(m->name, name) == 0) {
                        if (m->revision > *bestp)
                                *bestp = m->revision;
                        if (m->revision == revision)
                                have_rev = 1;
                }
        }

        if (af != NFPROTO_UNSPEC && !have_rev)
                return match_revfn(NFPROTO_UNSPEC, name, revision, bestp);

        return have_rev;
}

static int target_revfn(u8 af, const char *name, u8 revision, int *bestp)
{
        const struct xt_target *t;
        int have_rev = 0;

        list_for_each_entry(t, &xt[af].target, list) {
                if (strcmp(t->name, name) == 0) {
                        if (t->revision > *bestp)
                                *bestp = t->revision;
                        if (t->revision == revision)
                                have_rev = 1;
                }
        }

        if (af != NFPROTO_UNSPEC && !have_rev)
                return target_revfn(NFPROTO_UNSPEC, name, revision, bestp);

        return have_rev;
}

/* Returns true or false (if no such extension at all) */
int xt_find_revision(u8 af, const char *name, u8 revision, int target,
                     int *err)
{
        int have_rev, best = -1;

        if (mutex_lock_interruptible(&xt[af].mutex) != 0) {
                *err = -EINTR;
                return 1;
        }
        if (target == 1)
                have_rev = target_revfn(af, name, revision, &best);
        else
                have_rev = match_revfn(af, name, revision, &best);
        mutex_unlock(&xt[af].mutex);

        /* Nothing at all?  Return 0 to try loading module. */
        if (best == -1) {
                *err = -ENOENT;
                return 0;
        }

        *err = best;
        if (!have_rev)
                *err = -EPROTONOSUPPORT;
        return 1;
}
EXPORT_SYMBOL_GPL(xt_find_revision);

static char *textify_hooks(char *buf, size_t size, unsigned int mask)
{
        static const char *const names[] = {
                "PREROUTING", "INPUT", "FORWARD",
                "OUTPUT", "POSTROUTING", "BROUTING",
        };
        unsigned int i;
        char *p = buf;
        bool np = false;
        int res;

        *p = '\0';
        for (i = 0; i < ARRAY_SIZE(names); ++i) {
                if (!(mask & (1 << i)))
                        continue;
                res = snprintf(p, size, "%s%s", np ? "/" : "", names[i]);
                if (res > 0) {
                        size -= res;
                        p += res;
                }
                np = true;
        }

        return buf;
}

int xt_check_match(struct xt_mtchk_param *par,
                   unsigned int size, u_int8_t proto, bool inv_proto)
{
        if (XT_ALIGN(par->match->matchsize) != size &&
            par->match->matchsize != -1) {
                /*
                 * ebt_among is exempt from centralized matchsize checking
                 * because it uses a dynamic-size data set.
                 */
                pr_err("%s_tables: %s match: invalid size %Zu != %u\n",
                       xt_prefix[par->family], par->match->name,
                       XT_ALIGN(par->match->matchsize), size);
                return -EINVAL;
        }
        if (par->match->table != NULL &&
            strcmp(par->match->table, par->table) != 0) {
                pr_err("%s_tables: %s match: only valid in %s table, not %s\n",
                       xt_prefix[par->family], par->match->name,
                       par->match->table, par->table);
                return -EINVAL;
        }
        if (par->match->hooks && (par->hook_mask & ~par->match->hooks) != 0) {
                char used[64], allow[64];

                pr_err("%s_tables: %s match: used from hooks %s, but only "
                       "valid from %s\n",
                       xt_prefix[par->family], par->match->name,
                       textify_hooks(used, sizeof(used), par->hook_mask),
                       textify_hooks(allow, sizeof(allow), par->match->hooks));
                return -EINVAL;
        }
        if (par->match->proto && (par->match->proto != proto || inv_proto)) {
                pr_err("%s_tables: %s match: only valid for protocol %u\n",
                       xt_prefix[par->family], par->match->name,
                       par->match->proto);
                return -EINVAL;
        }
        if (par->match->checkentry != NULL && !par->match->checkentry(par))
                return -EINVAL;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_check_match);

#ifdef CONFIG_COMPAT
int xt_compat_add_offset(u_int8_t af, unsigned int offset, short delta)
{
        struct compat_delta *tmp;

        tmp = kmalloc(sizeof(struct compat_delta), GFP_KERNEL);
        if (!tmp)
                return -ENOMEM;

        tmp->offset = offset;
        tmp->delta = delta;

        if (xt[af].compat_offsets) {
                tmp->next = xt[af].compat_offsets->next;
                xt[af].compat_offsets->next = tmp;
        } else {
                xt[af].compat_offsets = tmp;
                tmp->next = NULL;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_add_offset);

void xt_compat_flush_offsets(u_int8_t af)
{
        struct compat_delta *tmp, *next;

        if (xt[af].compat_offsets) {
                for (tmp = xt[af].compat_offsets; tmp; tmp = next) {
                        next = tmp->next;
                        kfree(tmp);
                }
                xt[af].compat_offsets = NULL;
        }
}
EXPORT_SYMBOL_GPL(xt_compat_flush_offsets);

short xt_compat_calc_jump(u_int8_t af, unsigned int offset)
{
        struct compat_delta *tmp;
        short delta;

        for (tmp = xt[af].compat_offsets, delta = 0; tmp; tmp = tmp->next)
                if (tmp->offset < offset)
                        delta += tmp->delta;
        return delta;
}
EXPORT_SYMBOL_GPL(xt_compat_calc_jump);

int xt_compat_match_offset(const struct xt_match *match)
{
        u_int16_t csize = match->compatsize ? : match->matchsize;
        return XT_ALIGN(match->matchsize) - COMPAT_XT_ALIGN(csize);
}
EXPORT_SYMBOL_GPL(xt_compat_match_offset);

int xt_compat_match_from_user(struct xt_entry_match *m, void **dstptr,
                              unsigned int *size)
{
        const struct xt_match *match = m->u.kernel.match;
        struct compat_xt_entry_match *cm = (struct compat_xt_entry_match *)m;
        int pad, off = xt_compat_match_offset(match);
        u_int16_t msize = cm->u.user.match_size;

        m = *dstptr;
        memcpy(m, cm, sizeof(*cm));
        if (match->compat_from_user)
                match->compat_from_user(m->data, cm->data);
        else
                memcpy(m->data, cm->data, msize - sizeof(*cm));
        pad = XT_ALIGN(match->matchsize) - match->matchsize;
        if (pad > 0)
                memset(m->data + match->matchsize, 0, pad);

        msize += off;
        m->u.user.match_size = msize;

        *size += off;
        *dstptr += msize;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_match_from_user);

int xt_compat_match_to_user(struct xt_entry_match *m, void __user **dstptr,
                            unsigned int *size)
{
        const struct xt_match *match = m->u.kernel.match;
        struct compat_xt_entry_match __user *cm = *dstptr;
        int off = xt_compat_match_offset(match);
        u_int16_t msize = m->u.user.match_size - off;

        if (copy_to_user(cm, m, sizeof(*cm)) ||
            put_user(msize, &cm->u.user.match_size) ||
            copy_to_user(cm->u.user.name, m->u.kernel.match->name,
                         strlen(m->u.kernel.match->name) + 1))
                return -EFAULT;

        if (match->compat_to_user) {
                if (match->compat_to_user((void __user *)cm->data, m->data))
                        return -EFAULT;
        } else {
                if (copy_to_user(cm->data, m->data, msize - sizeof(*cm)))
                        return -EFAULT;
        }

        *size -= off;
        *dstptr += msize;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_match_to_user);
#endif /* CONFIG_COMPAT */

int xt_check_target(struct xt_tgchk_param *par,
                    unsigned int size, u_int8_t proto, bool inv_proto)
{
        if (XT_ALIGN(par->target->targetsize) != size) {
                pr_err("%s_tables: %s target: invalid size %Zu != %u\n",
                       xt_prefix[par->family], par->target->name,
                       XT_ALIGN(par->target->targetsize), size);
                return -EINVAL;
        }
        if (par->target->table != NULL &&
            strcmp(par->target->table, par->table) != 0) {
                pr_err("%s_tables: %s target: only valid in %s table, not %s\n",
                       xt_prefix[par->family], par->target->name,
                       par->target->table, par->table);
                return -EINVAL;
        }
        if (par->target->hooks && (par->hook_mask & ~par->target->hooks) != 0) {
                char used[64], allow[64];

                pr_err("%s_tables: %s target: used from hooks %s, but only "
                       "usable from %s\n",
                       xt_prefix[par->family], par->target->name,
                       textify_hooks(used, sizeof(used), par->hook_mask),
                       textify_hooks(allow, sizeof(allow), par->target->hooks));
                return -EINVAL;
        }
        if (par->target->proto && (par->target->proto != proto || inv_proto)) {
                pr_err("%s_tables: %s target: only valid for protocol %u\n",
                       xt_prefix[par->family], par->target->name,
                       par->target->proto);
                return -EINVAL;
        }
        if (par->target->checkentry != NULL && !par->target->checkentry(par))
                return -EINVAL;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_check_target);

#ifdef CONFIG_COMPAT
int xt_compat_target_offset(const struct xt_target *target)
{
        u_int16_t csize = target->compatsize ? : target->targetsize;
        return XT_ALIGN(target->targetsize) - COMPAT_XT_ALIGN(csize);
}
EXPORT_SYMBOL_GPL(xt_compat_target_offset);

void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
                                unsigned int *size)
{
        const struct xt_target *target = t->u.kernel.target;
        struct compat_xt_entry_target *ct = (struct compat_xt_entry_target *)t;
        int pad, off = xt_compat_target_offset(target);
        u_int16_t tsize = ct->u.user.target_size;

        t = *dstptr;
        memcpy(t, ct, sizeof(*ct));
        if (target->compat_from_user)
                target->compat_from_user(t->data, ct->data);
        else
                memcpy(t->data, ct->data, tsize - sizeof(*ct));
        pad = XT_ALIGN(target->targetsize) - target->targetsize;
        if (pad > 0)
                memset(t->data + target->targetsize, 0, pad);

        tsize += off;
        t->u.user.target_size = tsize;

        *size += off;
        *dstptr += tsize;
}
EXPORT_SYMBOL_GPL(xt_compat_target_from_user);

int xt_compat_target_to_user(struct xt_entry_target *t, void __user **dstptr,
                             unsigned int *size)
{
        const struct xt_target *target = t->u.kernel.target;
        struct compat_xt_entry_target __user *ct = *dstptr;
        int off = xt_compat_target_offset(target);
        u_int16_t tsize = t->u.user.target_size - off;

        if (copy_to_user(ct, t, sizeof(*ct)) ||
            put_user(tsize, &ct->u.user.target_size) ||
            copy_to_user(ct->u.user.name, t->u.kernel.target->name,
                         strlen(t->u.kernel.target->name) + 1))
                return -EFAULT;

        if (target->compat_to_user) {
                if (target->compat_to_user((void __user *)ct->data, t->data))
                        return -EFAULT;
        } else {
                if (copy_to_user(ct->data, t->data, tsize - sizeof(*ct)))
                        return -EFAULT;
        }

        *size -= off;
        *dstptr += tsize;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_target_to_user);
#endif

struct xt_table_info *xt_alloc_table_info(unsigned int size)
{
        struct xt_table_info *newinfo;
        int cpu;

        /* Pedantry: prevent them from hitting BUG() in vmalloc.c --RR */
        if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages)
                return NULL;

        newinfo = kzalloc(XT_TABLE_INFO_SZ, GFP_KERNEL);
        if (!newinfo)
                return NULL;

        newinfo->size = size;

        for_each_possible_cpu(cpu) {
                if (size <= PAGE_SIZE)
                        newinfo->entries[cpu] = kmalloc_node(size,
                                                        GFP_KERNEL,
                                                        cpu_to_node(cpu));
                else
                        newinfo->entries[cpu] = vmalloc_node(size,
                                                        cpu_to_node(cpu));

                if (newinfo->entries[cpu] == NULL) {
                        xt_free_table_info(newinfo);
                        return NULL;
                }
        }

        return newinfo;
}
EXPORT_SYMBOL(xt_alloc_table_info);

void xt_free_table_info(struct xt_table_info *info)
{
        int cpu;

        for_each_possible_cpu(cpu) {
                if (info->size <= PAGE_SIZE)
                        kfree(info->entries[cpu]);
                else
                        vfree(info->entries[cpu]);
        }
        kfree(info);
}
EXPORT_SYMBOL(xt_free_table_info);

/* Find table by name, grabs mutex & ref.  Returns ERR_PTR() on error. */
struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
                                    const char *name)
{
        struct xt_table *t;

        if (mutex_lock_interruptible(&xt[af].mutex) != 0)
                return ERR_PTR(-EINTR);

        list_for_each_entry(t, &net->xt.tables[af], list)
                if (strcmp(t->name, name) == 0 && try_module_get(t->me))
                        return t;
        mutex_unlock(&xt[af].mutex);
        return NULL;
}
EXPORT_SYMBOL_GPL(xt_find_table_lock);

void xt_table_unlock(struct xt_table *table)
{
        mutex_unlock(&xt[table->af].mutex);
}
EXPORT_SYMBOL_GPL(xt_table_unlock);

#ifdef CONFIG_COMPAT
void xt_compat_lock(u_int8_t af)
{
        mutex_lock(&xt[af].compat_mutex);
}
EXPORT_SYMBOL_GPL(xt_compat_lock);

void xt_compat_unlock(u_int8_t af)
{
        mutex_unlock(&xt[af].compat_mutex);
}
EXPORT_SYMBOL_GPL(xt_compat_unlock);
#endif

DEFINE_PER_CPU(struct xt_info_lock, xt_info_locks);
EXPORT_PER_CPU_SYMBOL_GPL(xt_info_locks);


struct xt_table_info *
xt_replace_table(struct xt_table *table,
              unsigned int num_counters,
              struct xt_table_info *newinfo,
              int *error)
{
        struct xt_table_info *private;

        /* Do the substitution. */
        local_bh_disable();
        private = table->private;

        /* Check inside lock: is the old number correct? */
        if (num_counters != private->number) {
                duprintf("num_counters != table->private->number (%u/%u)\n",
                         num_counters, private->number);
                local_bh_enable();
                *error = -EAGAIN;
                return NULL;
        }

        table->private = newinfo;
        newinfo->initial_entries = private->initial_entries;

        /*
         * Even though table entries have now been swapped, other CPU's
         * may still be using the old entries. This is okay, because
         * resynchronization happens because of the locking done
         * during the get_counters() routine.
         */
        local_bh_enable();

        return private;
}
EXPORT_SYMBOL_GPL(xt_replace_table);

struct xt_table *xt_register_table(struct net *net,
                                   const struct xt_table *input_table,
                                   struct xt_table_info *bootstrap,
                                   struct xt_table_info *newinfo)
{
        int ret;
        struct xt_table_info *private;
        struct xt_table *t, *table;

        /* Don't add one object to multiple lists. */
        table = kmemdup(input_table, sizeof(struct xt_table), GFP_KERNEL);
        if (!table) {
                ret = -ENOMEM;
                goto out;
        }

        ret = mutex_lock_interruptible(&xt[table->af].mutex);
        if (ret != 0)
                goto out_free;

        /* Don't autoload: we'd eat our tail... */
        list_for_each_entry(t, &net->xt.tables[table->af], list) {
                if (strcmp(t->name, table->name) == 0) {
                        ret = -EEXIST;
                        goto unlock;
                }
        }

        /* Simplifies replace_table code. */
        table->private = bootstrap;

        if (!xt_replace_table(table, 0, newinfo, &ret))
                goto unlock;

        private = table->private;
        duprintf("table->private->number = %u\n", private->number);

        /* save number of initial entries */
        private->initial_entries = private->number;

        list_add(&table->list, &net->xt.tables[table->af]);
        mutex_unlock(&xt[table->af].mutex);
        return table;

 unlock:
        mutex_unlock(&xt[table->af].mutex);
out_free:
        kfree(table);
out:
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(xt_register_table);

void *xt_unregister_table(struct xt_table *table)
{
        struct xt_table_info *private;

        mutex_lock(&xt[table->af].mutex);
        private = table->private;
        list_del(&table->list);
        mutex_unlock(&xt[table->af].mutex);
        kfree(table);

        return private;
}
EXPORT_SYMBOL_GPL(xt_unregister_table);

#ifdef CONFIG_PROC_FS
struct xt_names_priv {
        struct seq_net_private p;
        u_int8_t af;
};
static void *xt_table_seq_start(struct seq_file *seq, loff_t *pos)
{
        struct xt_names_priv *priv = seq->private;
        struct net *net = seq_file_net(seq);
        u_int8_t af = priv->af;

        mutex_lock(&xt[af].mutex);
        return seq_list_start(&net->xt.tables[af], *pos);
}

static void *xt_table_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct xt_names_priv *priv = seq->private;
        struct net *net = seq_file_net(seq);
        u_int8_t af = priv->af;

        return seq_list_next(v, &net->xt.tables[af], pos);
}

static void xt_table_seq_stop(struct seq_file *seq, void *v)
{
        struct xt_names_priv *priv = seq->private;
        u_int8_t af = priv->af;

        mutex_unlock(&xt[af].mutex);
}

static int xt_table_seq_show(struct seq_file *seq, void *v)
{
        struct xt_table *table = list_entry(v, struct xt_table, list);

        if (strlen(table->name))
                return seq_printf(seq, "%s\n", table->name);
        else
                return 0;
}

static const struct seq_operations xt_table_seq_ops = {
        .start  = xt_table_seq_start,
        .next   = xt_table_seq_next,
        .stop   = xt_table_seq_stop,
        .show   = xt_table_seq_show,
};

static int xt_table_open(struct inode *inode, struct file *file)
{
        int ret;
        struct xt_names_priv *priv;

        ret = seq_open_net(inode, file, &xt_table_seq_ops,
                           sizeof(struct xt_names_priv));
        if (!ret) {
                priv = ((struct seq_file *)file->private_data)->private;
                priv->af = (unsigned long)PDE(inode)->data;
        }
        return ret;
}

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

/*
 * Traverse state for ip{,6}_{tables,matches} for helping crossing
 * the multi-AF mutexes.
 */
struct nf_mttg_trav {
        struct list_head *head, *curr;
        uint8_t class, nfproto;
};

enum {
        MTTG_TRAV_INIT,
        MTTG_TRAV_NFP_UNSPEC,
        MTTG_TRAV_NFP_SPEC,
        MTTG_TRAV_DONE,
};

static void *xt_mttg_seq_next(struct seq_file *seq, void *v, loff_t *ppos,
    bool is_target)
{
        static const uint8_t next_class[] = {
                [MTTG_TRAV_NFP_UNSPEC] = MTTG_TRAV_NFP_SPEC,
                [MTTG_TRAV_NFP_SPEC]   = MTTG_TRAV_DONE,
        };
        struct nf_mttg_trav *trav = seq->private;

        switch (trav->class) {
        case MTTG_TRAV_INIT:
                trav->class = MTTG_TRAV_NFP_UNSPEC;
                mutex_lock(&xt[NFPROTO_UNSPEC].mutex);
                trav->head = trav->curr = is_target ?
                        &xt[NFPROTO_UNSPEC].target : &xt[NFPROTO_UNSPEC].match;
                break;
        case MTTG_TRAV_NFP_UNSPEC:
                trav->curr = trav->curr->next;
                if (trav->curr != trav->head)
                        break;
                mutex_unlock(&xt[NFPROTO_UNSPEC].mutex);
                mutex_lock(&xt[trav->nfproto].mutex);
                trav->head = trav->curr = is_target ?
                        &xt[trav->nfproto].target : &xt[trav->nfproto].match;
                trav->class = next_class[trav->class];
                break;
        case MTTG_TRAV_NFP_SPEC:
                trav->curr = trav->curr->next;
                if (trav->curr != trav->head)
                        break;
                /* fallthru, _stop will unlock */
        default:
                return NULL;
        }

        if (ppos != NULL)
                ++*ppos;
        return trav;
}

static void *xt_mttg_seq_start(struct seq_file *seq, loff_t *pos,
    bool is_target)
{
        struct nf_mttg_trav *trav = seq->private;
        unsigned int j;

        trav->class = MTTG_TRAV_INIT;
        for (j = 0; j < *pos; ++j)
                if (xt_mttg_seq_next(seq, NULL, NULL, is_target) == NULL)
                        return NULL;
        return trav;
}

static void xt_mttg_seq_stop(struct seq_file *seq, void *v)
{
        struct nf_mttg_trav *trav = seq->private;

        switch (trav->class) {
        case MTTG_TRAV_NFP_UNSPEC:
                mutex_unlock(&xt[NFPROTO_UNSPEC].mutex);
                break;
        case MTTG_TRAV_NFP_SPEC:
                mutex_unlock(&xt[trav->nfproto].mutex);
                break;
        }
}

static void *xt_match_seq_start(struct seq_file *seq, loff_t *pos)
{
        return xt_mttg_seq_start(seq, pos, false);
}

static void *xt_match_seq_next(struct seq_file *seq, void *v, loff_t *ppos)
{
        return xt_mttg_seq_next(seq, v, ppos, false);
}

static int xt_match_seq_show(struct seq_file *seq, void *v)
{
        const struct nf_mttg_trav *trav = seq->private;
        const struct xt_match *match;

        switch (trav->class) {
        case MTTG_TRAV_NFP_UNSPEC:
        case MTTG_TRAV_NFP_SPEC:
                if (trav->curr == trav->head)
                        return 0;
                match = list_entry(trav->curr, struct xt_match, list);
                return (*match->name == '\0') ? 0 :
                       seq_printf(seq, "%s\n", match->name);
        }
        return 0;
}

static const struct seq_operations xt_match_seq_ops = {
        .start  = xt_match_seq_start,
        .next   = xt_match_seq_next,
        .stop   = xt_mttg_seq_stop,
        .show   = xt_match_seq_show,
};

static int xt_match_open(struct inode *inode, struct file *file)
{
        struct seq_file *seq;
        struct nf_mttg_trav *trav;
        int ret;

        trav = kmalloc(sizeof(*trav), GFP_KERNEL);

        if (trav == NULL)
                return -ENOMEM;

        ret = seq_open(file, &xt_match_seq_ops);
        if (ret < 0) {
                kfree(trav);
                return ret;
        }

        seq = file->private_data;
        seq->private = trav;
        trav->nfproto = (unsigned long)PDE(inode)->data;
        return 0;
}

static const struct file_operations xt_match_ops = {
        .owner   = THIS_MODULE,
        .open    = xt_match_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release_private,
};

static void *xt_target_seq_start(struct seq_file *seq, loff_t *pos)
{
        return xt_mttg_seq_start(seq, pos, true);
}

static void *xt_target_seq_next(struct seq_file *seq, void *v, loff_t *ppos)
{
        return xt_mttg_seq_next(seq, v, ppos, true);
}

static int xt_target_seq_show(struct seq_file *seq, void *v)
{
        const struct nf_mttg_trav *trav = seq->private;
        const struct xt_target *target;

        switch (trav->class) {
        case MTTG_TRAV_NFP_UNSPEC:
        case MTTG_TRAV_NFP_SPEC:
                if (trav->curr == trav->head)
                        return 0;
                target = list_entry(trav->curr, struct xt_target, list);
                return (*target->name == '\0') ? 0 :
                       seq_printf(seq, "%s\n", target->name);
        }
        return 0;
}

static const struct seq_operations xt_target_seq_ops = {
        .start  = xt_target_seq_start,
        .next   = xt_target_seq_next,
        .stop   = xt_mttg_seq_stop,
        .show   = xt_target_seq_show,
};

static int xt_target_open(struct inode *inode, struct file *file)
{
        struct seq_file *seq;
        struct nf_mttg_trav *trav;
        int ret;

        trav = kmalloc(sizeof(*trav), GFP_KERNEL);
        if (trav == NULL)
                return -ENOMEM;

        ret = seq_open(file, &xt_target_seq_ops);
        if (ret < 0) {
                kfree(trav);
                return ret;
        }

        seq = file->private_data;
        seq->private = trav;
        trav->nfproto = (unsigned long)PDE(inode)->data;
        return 0;
}

static const struct file_operations xt_target_ops = {
        .owner   = THIS_MODULE,
        .open    = xt_target_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release_private,
};

#define FORMAT_TABLES   "_tables_names"
#define FORMAT_MATCHES  "_tables_matches"
#define FORMAT_TARGETS  "_tables_targets"

#endif /* CONFIG_PROC_FS */

int xt_proto_init(struct net *net, u_int8_t af)
{
#ifdef CONFIG_PROC_FS
        char buf[XT_FUNCTION_MAXNAMELEN];
        struct proc_dir_entry *proc;
#endif

        if (af >= ARRAY_SIZE(xt_prefix))
                return -EINVAL;


#ifdef CONFIG_PROC_FS
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        proc = proc_create_data(buf, 0440, net->proc_net, &xt_table_ops,
                                (void *)(unsigned long)af);
        if (!proc)
                goto out;

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
        proc = proc_create_data(buf, 0440, net->proc_net, &xt_match_ops,
                                (void *)(unsigned long)af);
        if (!proc)
                goto out_remove_tables;

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TARGETS, sizeof(buf));
        proc = proc_create_data(buf, 0440, net->proc_net, &xt_target_ops,
                                (void *)(unsigned long)af);
        if (!proc)
                goto out_remove_matches;
#endif

        return 0;

#ifdef CONFIG_PROC_FS
out_remove_matches:
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
        proc_net_remove(net, buf);

out_remove_tables:
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        proc_net_remove(net, buf);
out:
        return -1;
#endif
}
EXPORT_SYMBOL_GPL(xt_proto_init);

void xt_proto_fini(struct net *net, u_int8_t af)
{
#ifdef CONFIG_PROC_FS
        char buf[XT_FUNCTION_MAXNAMELEN];

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        proc_net_remove(net, buf);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TARGETS, sizeof(buf));
        proc_net_remove(net, buf);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
        proc_net_remove(net, buf);
#endif /*CONFIG_PROC_FS*/
}
EXPORT_SYMBOL_GPL(xt_proto_fini);

static int __net_init xt_net_init(struct net *net)
{
        int i;

        for (i = 0; i < NFPROTO_NUMPROTO; i++)
                INIT_LIST_HEAD(&net->xt.tables[i]);
        return 0;
}

static struct pernet_operations xt_net_ops = {
        .init = xt_net_init,
};

static int __init xt_init(void)
{
        unsigned int i;
        int rv;

        for_each_possible_cpu(i) {
                struct xt_info_lock *lock = &per_cpu(xt_info_locks, i);
                spin_lock_init(&lock->lock);
                lock->readers = 0;
        }

        xt = kmalloc(sizeof(struct xt_af) * NFPROTO_NUMPROTO, GFP_KERNEL);
        if (!xt)
                return -ENOMEM;

        for (i = 0; i < NFPROTO_NUMPROTO; i++) {
                mutex_init(&xt[i].mutex);
#ifdef CONFIG_COMPAT
                mutex_init(&xt[i].compat_mutex);
                xt[i].compat_offsets = NULL;
#endif
                INIT_LIST_HEAD(&xt[i].target);
                INIT_LIST_HEAD(&xt[i].match);
        }
        rv = register_pernet_subsys(&xt_net_ops);
        if (rv < 0)
                kfree(xt);
        return rv;
}

static void __exit xt_fini(void)
{
        unregister_pernet_subsys(&xt_net_ops);
        kfree(xt);
}

module_init(xt_init);
module_exit(xt_fini);