linux/net/netfilter/nf_conntrack_extend.c
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   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 i, 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                for (i = 0; i < NF_CT_EXT_NUM; i++) {
 103                        if (!__nf_ct_ext_exist(old, i))
 104                                continue;
 105
 106                        rcu_read_lock();
 107                        t = rcu_dereference(nf_ct_ext_types[i]);
 108                        if (t && t->move)
 109                                t->move((void *)new + new->offset[i],
 110                                        (void *)old + old->offset[i]);
 111                        rcu_read_unlock();
 112                }
 113                kfree_rcu(old, rcu);
 114                ct->ext = new;
 115        }
 116
 117        new->offset[id] = newoff;
 118        new->len = newlen;
 119        memset((void *)new + newoff, 0, newlen - newoff);
 120        return (void *)new + newoff;
 121}
 122EXPORT_SYMBOL(__nf_ct_ext_add_length);
 123
 124static void update_alloc_size(struct nf_ct_ext_type *type)
 125{
 126        int i, j;
 127        struct nf_ct_ext_type *t1, *t2;
 128        enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
 129
 130        /* unnecessary to update all types */
 131        if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
 132                min = type->id;
 133                max = type->id;
 134        }
 135
 136        /* This assumes that extended areas in conntrack for the types
 137           whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
 138        for (i = min; i <= max; i++) {
 139                t1 = rcu_dereference_protected(nf_ct_ext_types[i],
 140                                lockdep_is_held(&nf_ct_ext_type_mutex));
 141                if (!t1)
 142                        continue;
 143
 144                t1->alloc_size = ALIGN(sizeof(struct nf_ct_ext), t1->align) +
 145                                 t1->len;
 146                for (j = 0; j < NF_CT_EXT_NUM; j++) {
 147                        t2 = rcu_dereference_protected(nf_ct_ext_types[j],
 148                                lockdep_is_held(&nf_ct_ext_type_mutex));
 149                        if (t2 == NULL || t2 == t1 ||
 150                            (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
 151                                continue;
 152
 153                        t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
 154                                         + t2->len;
 155                }
 156        }
 157}
 158
 159/* This MUST be called in process context. */
 160int nf_ct_extend_register(struct nf_ct_ext_type *type)
 161{
 162        int ret = 0;
 163
 164        mutex_lock(&nf_ct_ext_type_mutex);
 165        if (nf_ct_ext_types[type->id]) {
 166                ret = -EBUSY;
 167                goto out;
 168        }
 169
 170        /* This ensures that nf_ct_ext_create() can allocate enough area
 171           before updating alloc_size */
 172        type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
 173                           + type->len;
 174        rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 175        update_alloc_size(type);
 176out:
 177        mutex_unlock(&nf_ct_ext_type_mutex);
 178        return ret;
 179}
 180EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 181
 182/* This MUST be called in process context. */
 183void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 184{
 185        mutex_lock(&nf_ct_ext_type_mutex);
 186        RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 187        update_alloc_size(type);
 188        mutex_unlock(&nf_ct_ext_type_mutex);
 189        rcu_barrier(); /* Wait for completion of call_rcu()'s */
 190}
 191EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);
 192
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