x_tables.c

Go to the documentation of this file.

/*
 * x_tables core - Backend for {ip,ip6,arp}_tables
 *
 * Copyright (C) 2006-2006 Harald Welte <[email protected]>
 *
 * Based on existing ip_tables code which is
 *   Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 *   Copyright (C) 2000-2005 Netfilter Core Team <[email protected]>
 *
 * 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 <[email protected]>");
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;
    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)
{
    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;
    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)
{
    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;

    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);

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;

    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 = 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;

    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)
{
    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),
               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) {
        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),
               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) {
        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 *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]);
    }

    if (info->jumpstack != NULL) {
        if (sizeof(void *) * info->stacksize > PAGE_SIZE) {
            for_each_possible_cpu(cpu)
                vfree(info->jumpstack[cpu]);
        } else {
            for_each_possible_cpu(cpu)
                kfree(info->jumpstack[cpu]);
        }
    }

    if (sizeof(void **) * nr_cpu_ids > PAGE_SIZE)
        vfree(info->jumpstack);
    else
        kfree(info->jumpstack);

    free_percpu(info->stackptr);

    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(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;
    }

    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();

#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;
    }

    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;
    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);
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 */

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);

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));
    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) {
        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);