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, gfp_t gfp)
  48{
  49        unsigned int off, len;
  50        struct nf_ct_ext_type *t;
  51        size_t alloc_size;
  52
  53        rcu_read_lock();
  54        t = rcu_dereference(nf_ct_ext_types[id]);
  55        BUG_ON(t == NULL);
  56        off = ALIGN(sizeof(struct nf_ct_ext), t->align);
  57        len = off + t->len;
  58        alloc_size = t->alloc_size;
  59        rcu_read_unlock();
  60
  61        *ext = kzalloc(alloc_size, gfp);
  62        if (!*ext)
  63                return NULL;
  64
  65        (*ext)->offset[id] = off;
  66        (*ext)->len = len;
  67
  68        return (void *)(*ext) + off;
  69}
  70
  71void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  72{
  73        struct nf_ct_ext *old, *new;
  74        int i, newlen, newoff;
  75        struct nf_ct_ext_type *t;
  76
  77        /* Conntrack must not be confirmed to avoid races on reallocation. */
  78        NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
  79
  80        old = ct->ext;
  81        if (!old)
  82                return nf_ct_ext_create(&ct->ext, id, gfp);
  83
  84        if (__nf_ct_ext_exist(old, id))
  85                return NULL;
  86
  87        rcu_read_lock();
  88        t = rcu_dereference(nf_ct_ext_types[id]);
  89        BUG_ON(t == NULL);
  90
  91        newoff = ALIGN(old->len, t->align);
  92        newlen = newoff + t->len;
  93        rcu_read_unlock();
  94
  95        new = __krealloc(old, newlen, gfp);
  96        if (!new)
  97                return NULL;
  98
  99        if (new != old) {
 100                for (i = 0; i < NF_CT_EXT_NUM; i++) {
 101                        if (!__nf_ct_ext_exist(old, i))
 102                                continue;
 103
 104                        rcu_read_lock();
 105                        t = rcu_dereference(nf_ct_ext_types[i]);
 106                        if (t && t->move)
 107                                t->move((void *)new + new->offset[i],
 108                                        (void *)old + old->offset[i]);
 109                        rcu_read_unlock();
 110                }
 111                kfree_rcu(old, rcu);
 112                ct->ext = new;
 113        }
 114
 115        new->offset[id] = newoff;
 116        new->len = newlen;
 117        memset((void *)new + newoff, 0, newlen - newoff);
 118        return (void *)new + newoff;
 119}
 120EXPORT_SYMBOL(__nf_ct_ext_add);
 121
 122static void update_alloc_size(struct nf_ct_ext_type *type)
 123{
 124        int i, j;
 125        struct nf_ct_ext_type *t1, *t2;
 126        enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
 127
 128        /* unnecessary to update all types */
 129        if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
 130                min = type->id;
 131                max = type->id;
 132        }
 133
 134        /* This assumes that extended areas in conntrack for the types
 135           whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
 136        for (i = min; i <= max; i++) {
 137                t1 = rcu_dereference_protected(nf_ct_ext_types[i],
 138                                lockdep_is_held(&nf_ct_ext_type_mutex));
 139                if (!t1)
 140                        continue;
 141
 142                t1->alloc_size = ALIGN(sizeof(struct nf_ct_ext), t1->align) +
 143                                 t1->len;
 144                for (j = 0; j < NF_CT_EXT_NUM; j++) {
 145                        t2 = rcu_dereference_protected(nf_ct_ext_types[j],
 146                                lockdep_is_held(&nf_ct_ext_type_mutex));
 147                        if (t2 == NULL || t2 == t1 ||
 148                            (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
 149                                continue;
 150
 151                        t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
 152                                         + t2->len;
 153                }
 154        }
 155}
 156
 157/* This MUST be called in process context. */
 158int nf_ct_extend_register(struct nf_ct_ext_type *type)
 159{
 160        int ret = 0;
 161
 162        mutex_lock(&nf_ct_ext_type_mutex);
 163        if (nf_ct_ext_types[type->id]) {
 164                ret = -EBUSY;
 165                goto out;
 166        }
 167
 168        /* This ensures that nf_ct_ext_create() can allocate enough area
 169           before updating alloc_size */
 170        type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
 171                           + type->len;
 172        rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 173        update_alloc_size(type);
 174out:
 175        mutex_unlock(&nf_ct_ext_type_mutex);
 176        return ret;
 177}
 178EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 179
 180/* This MUST be called in process context. */
 181void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 182{
 183        mutex_lock(&nf_ct_ext_type_mutex);
 184        RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 185        update_alloc_size(type);
 186        mutex_unlock(&nf_ct_ext_type_mutex);
 187        rcu_barrier(); /* Wait for completion of call_rcu()'s */
 188}
 189EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);
 190