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         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
  72 void *__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 }
 122 EXPORT_SYMBOL(__nf_ct_ext_add_length);
 123
 124 static 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. */
 160 int 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);
 176 out:
 177         mutex_unlock(&nf_ct_ext_type_mutex);
 178         return ret;
 179 }
 180 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 181
 182 /* This MUST be called in process context. */
 183 void 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 }
 191 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);