LXR linux/net/netfilter/nf_conntrack

   1/* Structure dynamic extension infrastructure
   2 * Copyright (C) 2004 Rusty Russell IBM Corporation
   3 * Copyright (C) 2007 Netfilter Core Team <coreteam@netfilter.org>
   4 * Copyright (C) 2007 USAGI/WIDE Project <http://www.linux-ipv6.org>
   5 *
   6 *      This program is free software; you can redistribute it and/or
   7 *      modify it under the terms of the GNU General Public License
   8 *      as published by the Free Software Foundation; either version
   9 *      2 of the License, or (at your option) any later version.
  10 */
  11#include <linux/kernel.h>
  12#include <linux/module.h>
  13#include <linux/mutex.h>
  14#include <linux/rcupdate.h>
  15#include <linux/slab.h>
  16#include <linux/skbuff.h>
  17#include <net/netfilter/nf_conntrack_extend.h>
  18
  19static struct nf_ct_ext_type __rcu *nf_ct_ext_types[NF_CT_EXT_NUM];
  20static DEFINE_MUTEX(nf_ct_ext_type_mutex);
  21
  22void __nf_ct_ext_destroy(struct nf_conn *ct)
  23{
  24        unsigned int i;
  25        struct nf_ct_ext_type *t;
  26        struct nf_ct_ext *ext = ct->ext;
  27
  28        for (i = 0; i < NF_CT_EXT_NUM; i++) {
  29                if (!__nf_ct_ext_exist(ext, i))
  30                        continue;
  31
  32                rcu_read_lock();
  33                t = rcu_dereference(nf_ct_ext_types[i]);
  34
  35                /* Here the nf_ct_ext_type might have been unregisterd.
  36                 * I.e., it has responsible to cleanup private
  37                 * area in all conntracks when it is unregisterd.
  38                 */
  39                if (t && t->destroy)
  40                        t->destroy(ct);
  41                rcu_read_unlock();
  42        }
  43}
  44EXPORT_SYMBOL(__nf_ct_ext_destroy);
  45
  46static void *
  47nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id,
  48                 size_t var_alloc_len, gfp_t gfp)
  49{
  50        unsigned int off, len;
  51        struct nf_ct_ext_type *t;
  52        size_t alloc_size;
  53
  54        rcu_read_lock();
  55        t = rcu_dereference(nf_ct_ext_types[id]);
  56        BUG_ON(t == NULL);
  57        off = ALIGN(sizeof(struct nf_ct_ext), t->align);
  58        len = off + t->len + var_alloc_len;
  59        alloc_size = t->alloc_size + var_alloc_len;
  60        rcu_read_unlock();
  61
  62        *ext = kzalloc(alloc_size, gfp);
  63        if (!*ext)
  64                return NULL;
  65
  66        (*ext)->offset[id] = off;
  67        (*ext)->len = len;
  68
  69        return (void *)(*ext) + off;
  70}
  71
  72void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id,
  73                             size_t var_alloc_len, gfp_t gfp)
  74{
  75        struct nf_ct_ext *old, *new;
  76        int newlen, newoff;
  77        struct nf_ct_ext_type *t;
  78
  79        /* Conntrack must not be confirmed to avoid races on reallocation. */
  80        NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
  81
  82        old = ct->ext;
  83        if (!old)
  84                return nf_ct_ext_create(&ct->ext, id, var_alloc_len, gfp);
  85
  86        if (__nf_ct_ext_exist(old, id))
  87                return NULL;
  88
  89        rcu_read_lock();
  90        t = rcu_dereference(nf_ct_ext_types[id]);
  91        BUG_ON(t == NULL);
  92
  93        newoff = ALIGN(old->len, t->align);
  94        newlen = newoff + t->len + var_alloc_len;
  95        rcu_read_unlock();
  96
  97        new = __krealloc(old, newlen, gfp);
  98        if (!new)
  99                return NULL;
 100
 101        if (new != old) {
 102                kfree_rcu(old, rcu);
 103                rcu_assign_pointer(ct->ext, new);
 104        }
 105
 106        new->offset[id] = newoff;
 107        new->len = newlen;
 108        memset((void *)new + newoff, 0, newlen - newoff);
 109        return (void *)new + newoff;
 110}
 111EXPORT_SYMBOL(__nf_ct_ext_add_length);
 112
 113static void update_alloc_size(struct nf_ct_ext_type *type)
 114{
 115        int i, j;
 116        struct nf_ct_ext_type *t1, *t2;
 117        enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
 118
 119        /* unnecessary to update all types */
 120        if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
 121                min = type->id;
 122                max = type->id;
 123        }
 124
 125        /* This assumes that extended areas in conntrack for the types
 126           whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
 127        for (i = min; i <= max; i++) {
 128                t1 = rcu_dereference_protected(nf_ct_ext_types[i],
 129                                lockdep_is_held(&nf_ct_ext_type_mutex));
 130                if (!t1)
 131                        continue;
 132
 133                t1->alloc_size = ALIGN(sizeof(struct nf_ct_ext), t1->align) +
 134                                 t1->len;
 135                for (j = 0; j < NF_CT_EXT_NUM; j++) {
 136                        t2 = rcu_dereference_protected(nf_ct_ext_types[j],
 137                                lockdep_is_held(&nf_ct_ext_type_mutex));
 138                        if (t2 == NULL || t2 == t1 ||
 139                            (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
 140                                continue;
 141
 142                        t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
 143                                         + t2->len;
 144                }
 145        }
 146}
 147
 148/* This MUST be called in process context. */
 149int nf_ct_extend_register(struct nf_ct_ext_type *type)
 150{
 151        int ret = 0;
 152
 153        mutex_lock(&nf_ct_ext_type_mutex);
 154        if (nf_ct_ext_types[type->id]) {
 155                ret = -EBUSY;
 156                goto out;
 157        }
 158
 159        /* This ensures that nf_ct_ext_create() can allocate enough area
 160           before updating alloc_size */
 161        type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
 162                           + type->len;
 163        rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 164        update_alloc_size(type);
 165out:
 166        mutex_unlock(&nf_ct_ext_type_mutex);
 167        return ret;
 168}
 169EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 170
 171/* This MUST be called in process context. */
 172void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 173{
 174        mutex_lock(&nf_ct_ext_type_mutex);
 175        RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 176        update_alloc_size(type);
 177        mutex_unlock(&nf_ct_ext_type_mutex);
 178        rcu_barrier(); /* Wait for completion of call_rcu()'s */
 179}
 180EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);
 181