blkcg: misc preparations for unified hierarchy interface

[linux-2.6/btrfs-unstable.git] / net / netfilter / x_tables.c

/*
 * x_tables core - Backend for {ip,ip6,arp}_tables
 *
 * Copyright (C) 2006-2006 Harald Welte <laforge@netfilter.org>
 * Copyright (C) 2006-2012 Patrick McHardy <kaber@trash.net>
 *
 * 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.
 *
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/module.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 <linux/slab.h>
#include <linux/audit.h>
#include <net/net_namespace.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_arp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_arp/arp_tables.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 {
        unsigned int offset; /* offset in kernel */
        int delta; /* delta in 32bit user land */
};

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_tab;
        unsigned int number; /* number of slots in compat_tab[] */
        unsigned int cur; /* number of used slots in compat_tab[] */
#endif
};

static struct xt_af *xt;

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

/* Allow this many total (re)entries. */
static const unsigned int xt_jumpstack_multiplier = 2;

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

        mutex_lock(&xt[af].mutex);
        list_add(&target->list, &xt[af].target);
        mutex_unlock(&xt[af].mutex);
        return 0;
}
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)
{
        while (n-- > 0)
                xt_unregister_target(&target[n]);
}
EXPORT_SYMBOL(xt_unregister_targets);

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

        mutex_lock(&xt[af].mutex);
        list_add(&match->list, &xt[af].match);
        mutex_unlock(&xt[af].mutex);
        return 0;
}
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)
{
        while (n-- > 0)
                xt_unregister_match(&match[n]);
}
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.
 */

/* 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 = -ENOENT;

        mutex_lock(&xt[af].mutex);
        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);

struct xt_match *
xt_request_find_match(uint8_t nfproto, const char *name, uint8_t revision)
{
        struct xt_match *match;

        match = xt_find_match(nfproto, name, revision);
        if (IS_ERR(match)) {
                request_module("%st_%s", xt_prefix[nfproto], name);
                match = xt_find_match(nfproto, name, revision);
        }

        return match;
}
EXPORT_SYMBOL_GPL(xt_request_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 = -ENOENT;

        mutex_lock(&xt[af].mutex);
        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 = xt_find_target(af, name, revision);
        if (IS_ERR(target)) {
                request_module("%st_%s", xt_prefix[af], name);
                target = xt_find_target(af, name, revision);
        }

        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;

        mutex_lock(&xt[af].mutex);
        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, uint8_t nfproto)
{
        static const char *const inetbr_names[] = {
                "PREROUTING", "INPUT", "FORWARD",
                "OUTPUT", "POSTROUTING", "BROUTING",
        };
        static const char *const arp_names[] = {
                "INPUT", "FORWARD", "OUTPUT",
        };
        const char *const *names;
        unsigned int i, max;
        char *p = buf;
        bool np = false;
        int res;

        names = (nfproto == NFPROTO_ARP) ? arp_names : inetbr_names;
        max   = (nfproto == NFPROTO_ARP) ? ARRAY_SIZE(arp_names) :
                                           ARRAY_SIZE(inetbr_names);
        *p = '\0';
        for (i = 0; i < max; ++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)
{
        int ret;

        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.%u match: invalid size "
                       "%u (kernel) != (user) %u\n",
                       xt_prefix[par->family], par->match->name,
                       par->match->revision,
                       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,
                                     par->family),
                       textify_hooks(allow, sizeof(allow), par->match->hooks,
                                     par->family));
                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) {
                ret = par->match->checkentry(par);
                if (ret < 0)
                        return ret;
                else if (ret > 0)
                        /* Flag up potential errors. */
                        return -EIO;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(xt_check_match);

#ifdef CONFIG_COMPAT
int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta)
{
        struct xt_af *xp = &xt[af];

        if (!xp->compat_tab) {
                if (!xp->number)
                        return -EINVAL;
                xp->compat_tab = vmalloc(sizeof(struct compat_delta) * xp->number);
                if (!xp->compat_tab)
                        return -ENOMEM;
                xp->cur = 0;
        }

        if (xp->cur >= xp->number)
                return -EINVAL;

        if (xp->cur)
                delta += xp->compat_tab[xp->cur - 1].delta;
        xp->compat_tab[xp->cur].offset = offset;
        xp->compat_tab[xp->cur].delta = delta;
        xp->cur++;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_add_offset);

void xt_compat_flush_offsets(u_int8_t af)
{
        if (xt[af].compat_tab) {
                vfree(xt[af].compat_tab);
                xt[af].compat_tab = NULL;
                xt[af].number = 0;
                xt[af].cur = 0;
        }
}
EXPORT_SYMBOL_GPL(xt_compat_flush_offsets);

int xt_compat_calc_jump(u_int8_t af, unsigned int offset)
{
        struct compat_delta *tmp = xt[af].compat_tab;
        int mid, left = 0, right = xt[af].cur - 1;

        while (left <= right) {
                mid = (left + right) >> 1;
                if (offset > tmp[mid].offset)
                        left = mid + 1;
                else if (offset < tmp[mid].offset)
                        right = mid - 1;
                else
                        return mid ? tmp[mid - 1].delta : 0;
        }
        return left ? tmp[left - 1].delta : 0;
}
EXPORT_SYMBOL_GPL(xt_compat_calc_jump);

void xt_compat_init_offsets(u_int8_t af, unsigned int number)
{
        xt[af].number = number;
        xt[af].cur = 0;
}
EXPORT_SYMBOL(xt_compat_init_offsets);

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(const 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)
{
        int ret;

        if (XT_ALIGN(par->target->targetsize) != size) {
                pr_err("%s_tables: %s.%u target: invalid size "
                       "%u (kernel) != (user) %u\n",
                       xt_prefix[par->family], par->target->name,
                       par->target->revision,
                       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,
                                     par->family),
                       textify_hooks(allow, sizeof(allow), par->target->hooks,
                                     par->family));
                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) {
                ret = par->target->checkentry(par);
                if (ret < 0)
                        return ret;
                else if (ret > 0)
                        /* Flag up potential errors. */
                        return -EIO;
        }
        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(const 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 *info = NULL;
        size_t sz = sizeof(*info) + size;

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

        if (sz <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
                info = kmalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY);
        if (!info) {
                info = vmalloc(sz);
                if (!info)
                        return NULL;
        }
        memset(info, 0, sizeof(*info));
        info->size = size;
        return info;
}
EXPORT_SYMBOL(xt_alloc_table_info);

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

        if (info->jumpstack != NULL) {
                for_each_possible_cpu(cpu)
                        kvfree(info->jumpstack[cpu]);
                kvfree(info->jumpstack);
        }

        free_percpu(info->stackptr);

        kvfree(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;

        mutex_lock(&xt[af].mutex);
        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(seqcount_t, xt_recseq);
EXPORT_PER_CPU_SYMBOL_GPL(xt_recseq);

static int xt_jumpstack_alloc(struct xt_table_info *i)
{
        unsigned int size;
        int cpu;

        i->stackptr = alloc_percpu(unsigned int);
        if (i->stackptr == NULL)
                return -ENOMEM;

        size = sizeof(void **) * nr_cpu_ids;
        if (size > PAGE_SIZE)
                i->jumpstack = vzalloc(size);
        else
                i->jumpstack = kzalloc(size, GFP_KERNEL);
        if (i->jumpstack == NULL)
                return -ENOMEM;

        i->stacksize *= xt_jumpstack_multiplier;
        size = sizeof(void *) * i->stacksize;
        for_each_possible_cpu(cpu) {
                if (size > PAGE_SIZE)
                        i->jumpstack[cpu] = vmalloc_node(size,
                                cpu_to_node(cpu));
                else
                        i->jumpstack[cpu] = kmalloc_node(size,
                                GFP_KERNEL, cpu_to_node(cpu));
                if (i->jumpstack[cpu] == NULL)
                        /*
                         * Freeing will be done later on by the callers. The
                         * chain is: xt_replace_table -> __do_replace ->
                         * do_replace -> xt_free_table_info.
                         */
                        return -ENOMEM;
        }

        return 0;
}

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;
        int ret;

        ret = xt_jumpstack_alloc(newinfo);
        if (ret < 0) {
                *error = ret;
                return NULL;
        }

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

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

        newinfo->initial_entries = private->initial_entries;
        /*
         * Ensure contents of newinfo are visible before assigning to
         * private.
         */
        smp_wmb();
        table->private = newinfo;

        /*
         * 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();

#ifdef CONFIG_AUDIT
        if (audit_enabled) {
                struct audit_buffer *ab;

                ab = audit_log_start(current->audit_context, GFP_KERNEL,
                                     AUDIT_NETFILTER_CFG);
                if (ab) {
                        audit_log_format(ab, "table=%s family=%u entries=%u",
                                         table->name, table->af,
                                         private->number);
                        audit_log_end(ab);
                }
        }
#endif

        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;
        }

        mutex_lock(&xt[table->af].mutex);
        /* 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;
        pr_debug("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);
        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 (*table->name)
                seq_printf(seq, "%s\n", table->name);
        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_DATA(inode);
        }
        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);
                if (*match->name)
                        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 nf_mttg_trav *trav;
        trav = __seq_open_private(file, &xt_match_seq_ops, sizeof(*trav));
        if (!trav)
                return -ENOMEM;

        trav->nfproto = (unsigned long)PDE_DATA(inode);
        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);
                if (*target->name)
                        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 nf_mttg_trav *trav;
        trav = __seq_open_private(file, &xt_target_seq_ops, sizeof(*trav));
        if (!trav)
                return -ENOMEM;

        trav->nfproto = (unsigned long)PDE_DATA(inode);
        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 */

/**
 * xt_hook_link - set up hooks for a new table
 * @table:      table with metadata needed to set up hooks
 * @fn:         Hook function
 *
 * This function will take care of creating and registering the necessary
 * Netfilter hooks for XT tables.
 */
struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)
{
        unsigned int hook_mask = table->valid_hooks;
        uint8_t i, num_hooks = hweight32(hook_mask);
        uint8_t hooknum;
        struct nf_hook_ops *ops;
        int ret;

        ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
        if (ops == NULL)
                return ERR_PTR(-ENOMEM);

        for (i = 0, hooknum = 0; i < num_hooks && hook_mask != 0;
             hook_mask >>= 1, ++hooknum) {
                if (!(hook_mask & 1))
                        continue;
                ops[i].hook     = fn;
                ops[i].owner    = table->me;
                ops[i].pf       = table->af;
                ops[i].hooknum  = hooknum;
                ops[i].priority = table->priority;
                ++i;
        }

        ret = nf_register_hooks(ops, num_hooks);
        if (ret < 0) {
                kfree(ops);
                return ERR_PTR(ret);
        }

        return ops;
}
EXPORT_SYMBOL_GPL(xt_hook_link);

/**
 * xt_hook_unlink - remove hooks for a table
 * @ops:        nf_hook_ops array as returned by nf_hook_link
 * @hook_mask:  the very same mask that was passed to nf_hook_link
 */
void xt_hook_unlink(const struct xt_table *table, struct nf_hook_ops *ops)
{
        nf_unregister_hooks(ops, hweight32(table->valid_hooks));
        kfree(ops);
}
EXPORT_SYMBOL_GPL(xt_hook_unlink);

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));
        remove_proc_entry(buf, net->proc_net);

out_remove_tables:
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);
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));
        remove_proc_entry(buf, net->proc_net);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TARGETS, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);
#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) {
                seqcount_init(&per_cpu(xt_recseq, i));
        }

        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_tab = 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);