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