root/net/netfilter/nf_conntrack_extend.c

DEFINITIONS

1. __nf_ct_ext_destroy
2. nf_ct_ext_create
3. __nf_ct_ext_free_rcu
4. __nf_ct_ext_add
5. update_alloc_size
6. nf_ct_extend_register
7. nf_ct_extend_unregister

/* Structure dynamic extension infrastructure
 * Copyright (C) 2004 Rusty Russell IBM Corporation
 * Copyright (C) 2007 Netfilter Core Team <coreteam@netfilter.org>
 * Copyright (C) 2007 USAGI/WIDE Project <http://www.linux-ipv6.org>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <net/netfilter/nf_conntrack_extend.h>

static struct nf_ct_ext_type *nf_ct_ext_types[NF_CT_EXT_NUM];
static DEFINE_MUTEX(nf_ct_ext_type_mutex);

void __nf_ct_ext_destroy(struct nf_conn *ct)
{
        unsigned int i;
        struct nf_ct_ext_type *t;

        for (i = 0; i < NF_CT_EXT_NUM; i++) {
                if (!nf_ct_ext_exist(ct, i))
                        continue;

                rcu_read_lock();
                t = rcu_dereference(nf_ct_ext_types[i]);

                /* Here the nf_ct_ext_type might have been unregisterd.
                 * I.e., it has responsible to cleanup private
                 * area in all conntracks when it is unregisterd.
                 */
                if (t && t->destroy)
                        t->destroy(ct);
                rcu_read_unlock();
        }
}
EXPORT_SYMBOL(__nf_ct_ext_destroy);

static void *
nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
{
        unsigned int off, len;
        struct nf_ct_ext_type *t;

        rcu_read_lock();
        t = rcu_dereference(nf_ct_ext_types[id]);
        BUG_ON(t == NULL);
        off = ALIGN(sizeof(struct nf_ct_ext), t->align);
        len = off + t->len;
        rcu_read_unlock();

        *ext = kzalloc(t->alloc_size, gfp);
        if (!*ext)
                return NULL;

        INIT_RCU_HEAD(&(*ext)->rcu);
        (*ext)->offset[id] = off;
        (*ext)->len = len;

        return (void *)(*ext) + off;
}

static void __nf_ct_ext_free_rcu(struct rcu_head *head)
{
        struct nf_ct_ext *ext = container_of(head, struct nf_ct_ext, rcu);
        kfree(ext);
}

void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
{
        struct nf_ct_ext *new;
        int i, newlen, newoff;
        struct nf_ct_ext_type *t;

        /* Conntrack must not be confirmed to avoid races on reallocation. */
        NF_CT_ASSERT(!nf_ct_is_confirmed(ct));

        if (!ct->ext)
                return nf_ct_ext_create(&ct->ext, id, gfp);

        if (nf_ct_ext_exist(ct, id))
                return NULL;

        rcu_read_lock();
        t = rcu_dereference(nf_ct_ext_types[id]);
        BUG_ON(t == NULL);

        newoff = ALIGN(ct->ext->len, t->align);
        newlen = newoff + t->len;
        rcu_read_unlock();

        new = __krealloc(ct->ext, newlen, gfp);
        if (!new)
                return NULL;

        if (new != ct->ext) {
                for (i = 0; i < NF_CT_EXT_NUM; i++) {
                        if (!nf_ct_ext_exist(ct, i))
                                continue;

                        rcu_read_lock();
                        t = rcu_dereference(nf_ct_ext_types[i]);
                        if (t && t->move)
                                t->move((void *)new + new->offset[i],
                                        (void *)ct->ext + ct->ext->offset[i]);
                        rcu_read_unlock();
                }
                call_rcu(&ct->ext->rcu, __nf_ct_ext_free_rcu);
                ct->ext = new;
        }

        new->offset[id] = newoff;
        new->len = newlen;
        memset((void *)new + newoff, 0, newlen - newoff);
        return (void *)new + newoff;
}
EXPORT_SYMBOL(__nf_ct_ext_add);

static void update_alloc_size(struct nf_ct_ext_type *type)
{
        int i, j;
        struct nf_ct_ext_type *t1, *t2;
        enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;

        /* unnecessary to update all types */
        if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
                min = type->id;
                max = type->id;
        }

        /* This assumes that extended areas in conntrack for the types
           whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
        for (i = min; i <= max; i++) {
                t1 = nf_ct_ext_types[i];
                if (!t1)
                        continue;

                t1->alloc_size = sizeof(struct nf_ct_ext)
                                 + ALIGN(sizeof(struct nf_ct_ext), t1->align)
                                 + t1->len;
                for (j = 0; j < NF_CT_EXT_NUM; j++) {
                        t2 = nf_ct_ext_types[j];
                        if (t2 == NULL || t2 == t1 ||
                            (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
                                continue;

                        t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
                                         + t2->len;
                }
        }
}

/* This MUST be called in process context. */
int nf_ct_extend_register(struct nf_ct_ext_type *type)
{
        int ret = 0;

        mutex_lock(&nf_ct_ext_type_mutex);
        if (nf_ct_ext_types[type->id]) {
                ret = -EBUSY;
                goto out;
        }

        /* This ensures that nf_ct_ext_create() can allocate enough area
           before updating alloc_size */
        type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
                           + type->len;
        rcu_assign_pointer(nf_ct_ext_types[type->id], type);
        update_alloc_size(type);
out:
        mutex_unlock(&nf_ct_ext_type_mutex);
        return ret;
}
EXPORT_SYMBOL_GPL(nf_ct_extend_register);

/* This MUST be called in process context. */
void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
{
        mutex_lock(&nf_ct_ext_type_mutex);
        rcu_assign_pointer(nf_ct_ext_types[type->id], NULL);
        update_alloc_size(type);
        mutex_unlock(&nf_ct_ext_type_mutex);
        synchronize_rcu();
}
EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);