net/netfilter/nf_conntrack_extend.c

   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
  19 static struct nf_ct_ext_type __rcu *nf_ct_ext_types[NF_CT_EXT_NUM];
  20 static DEFINE_MUTEX(nf_ct_ext_type_mutex);
  21
  22 void __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 }
  44 EXPORT_SYMBOL(__nf_ct_ext_destroy);
  45
  46 static void *
  47 nf_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         if (!t) {
  57                 rcu_read_unlock();
  58                 return NULL;
  59         }
  60
  61         off = ALIGN(sizeof(struct nf_ct_ext), t->align);
  62         len = off + t->len + var_alloc_len;
  63         alloc_size = t->alloc_size + var_alloc_len;
  64         rcu_read_unlock();
  65
  66         *ext = kzalloc(alloc_size, gfp);
  67         if (!*ext)
  68                 return NULL;
  69
  70         (*ext)->offset[id] = off;
  71         (*ext)->len = len;
  72
  73         return (void *)(*ext) + off;
  74 }
  75
  76 void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id,
  77                              size_t var_alloc_len, gfp_t gfp)
  78 {
  79         struct nf_ct_ext *old, *new;
  80         int newlen, newoff;
  81         struct nf_ct_ext_type *t;
  82
  83         /* Conntrack must not be confirmed to avoid races on reallocation. */
  84         NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
  85
  86         old = ct->ext;
  87         if (!old)
  88                 return nf_ct_ext_create(&ct->ext, id, var_alloc_len, gfp);
  89
  90         if (__nf_ct_ext_exist(old, id))
  91                 return NULL;
  92
  93         rcu_read_lock();
  94         t = rcu_dereference(nf_ct_ext_types[id]);
  95         if (!t) {
  96                 rcu_read_unlock();
  97                 return NULL;
  98         }
  99
 100         newoff = ALIGN(old->len, t->align);
 101         newlen = newoff + t->len + var_alloc_len;
 102         rcu_read_unlock();
 103
 104         new = __krealloc(old, newlen, gfp);
 105         if (!new)
 106                 return NULL;
 107
 108         if (new != old) {
 109                 kfree_rcu(old, rcu);
 110                 rcu_assign_pointer(ct->ext, new);
 111         }
 112
 113         new->offset[id] = newoff;
 114         new->len = newlen;
 115         memset((void *)new + newoff, 0, newlen - newoff);
 116         return (void *)new + newoff;
 117 }
 118 EXPORT_SYMBOL(__nf_ct_ext_add_length);
 119
 120 static void update_alloc_size(struct nf_ct_ext_type *type)
 121 {
 122         int i, j;
 123         struct nf_ct_ext_type *t1, *t2;
 124         enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
 125
 126         /* unnecessary to update all types */
 127         if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
 128                 min = type->id;
 129                 max = type->id;
 130         }
 131
 132         /* This assumes that extended areas in conntrack for the types
 133            whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
 134         for (i = min; i <= max; i++) {
 135                 t1 = rcu_dereference_protected(nf_ct_ext_types[i],
 136                                 lockdep_is_held(&nf_ct_ext_type_mutex));
 137                 if (!t1)
 138                         continue;
 139
 140                 t1->alloc_size = ALIGN(sizeof(struct nf_ct_ext), t1->align) +
 141                                  t1->len;
 142                 for (j = 0; j < NF_CT_EXT_NUM; j++) {
 143                         t2 = rcu_dereference_protected(nf_ct_ext_types[j],
 144                                 lockdep_is_held(&nf_ct_ext_type_mutex));
 145                         if (t2 == NULL || t2 == t1 ||
 146                             (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
 147                                 continue;
 148
 149                         t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
 150                                          + t2->len;
 151                 }
 152         }
 153 }
 154
 155 /* This MUST be called in process context. */
 156 int nf_ct_extend_register(struct nf_ct_ext_type *type)
 157 {
 158         int ret = 0;
 159
 160         mutex_lock(&nf_ct_ext_type_mutex);
 161         if (nf_ct_ext_types[type->id]) {
 162                 ret = -EBUSY;
 163                 goto out;
 164         }
 165
 166         /* This ensures that nf_ct_ext_create() can allocate enough area
 167            before updating alloc_size */
 168         type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
 169                            + type->len;
 170         rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 171         update_alloc_size(type);
 172 out:
 173         mutex_unlock(&nf_ct_ext_type_mutex);
 174         return ret;
 175 }
 176 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 177
 178 /* This MUST be called in process context. */
 179 void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 180 {
 181         mutex_lock(&nf_ct_ext_type_mutex);
 182         RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 183         update_alloc_size(type);
 184         mutex_unlock(&nf_ct_ext_type_mutex);
 185         synchronize_rcu();
 186 }
 187 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);