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 *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
  27         for (i = 0; i < NF_CT_EXT_NUM; i++) {
  28                 if (!nf_ct_ext_exist(ct, i))
  29                         continue;
  30
  31                 rcu_read_lock();
  32                 t = rcu_dereference(nf_ct_ext_types[i]);
  33
  34                 /* Here the nf_ct_ext_type might have been unregisterd.
  35                  * I.e., it has responsible to cleanup private
  36                  * area in all conntracks when it is unregisterd.
  37                  */
  38                 if (t && t->destroy)
  39                         t->destroy(ct);
  40                 rcu_read_unlock();
  41         }
  42 }
  43 EXPORT_SYMBOL(__nf_ct_ext_destroy);
  44
  45 static void *
  46 nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
  47 {
  48         unsigned int off, len;
  49         struct nf_ct_ext_type *t;
  50
  51         rcu_read_lock();
  52         t = rcu_dereference(nf_ct_ext_types[id]);
  53         BUG_ON(t == NULL);
  54         off = ALIGN(sizeof(struct nf_ct_ext), t->align);
  55         len = off + t->len;
  56         rcu_read_unlock();
  57
  58         *ext = kzalloc(t->alloc_size, gfp);
  59         if (!*ext)
  60                 return NULL;
  61
  62         (*ext)->offset[id] = off;
  63         (*ext)->len = len;
  64
  65         return (void *)(*ext) + off;
  66 }
  67
  68 void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  69 {
  70         struct nf_ct_ext *new;
  71         int i, newlen, newoff;
  72         struct nf_ct_ext_type *t;
  73
  74         /* Conntrack must not be confirmed to avoid races on reallocation. */
  75         NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
  76
  77         if (!ct->ext)
  78                 return nf_ct_ext_create(&ct->ext, id, gfp);
  79
  80         if (nf_ct_ext_exist(ct, id))
  81                 return NULL;
  82
  83         rcu_read_lock();
  84         t = rcu_dereference(nf_ct_ext_types[id]);
  85         BUG_ON(t == NULL);
  86
  87         newoff = ALIGN(ct->ext->len, t->align);
  88         newlen = newoff + t->len;
  89         rcu_read_unlock();
  90
  91         if (newlen >= ksize(ct->ext)) {
  92                 new = kmalloc(newlen, gfp);
  93                 if (!new)
  94                         return NULL;
  95
  96                 memcpy(new, ct->ext, ct->ext->len);
  97
  98                 for (i = 0; i < NF_CT_EXT_NUM; i++) {
  99                         if (!nf_ct_ext_exist(ct, i))
 100                                 continue;
 101
 102                         rcu_read_lock();
 103                         t = rcu_dereference(nf_ct_ext_types[i]);
 104                         if (t && t->move)
 105                                 t->move((void *)new + new->offset[i],
 106                                         (void *)ct->ext + ct->ext->offset[i]);
 107                         rcu_read_unlock();
 108                 }
 109                 kfree(ct->ext);
 110                 ct->ext = new;
 111         }
 112
 113         ct->ext->offset[id] = newoff;
 114         ct->ext->len = newlen;
 115         memset((void *)ct->ext + newoff, 0, newlen - newoff);
 116         return (void *)ct->ext + newoff;
 117 }
 118 EXPORT_SYMBOL(__nf_ct_ext_add);
 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 = nf_ct_ext_types[i];
 136                 if (!t1)
 137                         continue;
 138
 139                 t1->alloc_size = sizeof(struct nf_ct_ext)
 140                                  + ALIGN(sizeof(struct nf_ct_ext), t1->align)
 141                                  + t1->len;
 142                 for (j = 0; j < NF_CT_EXT_NUM; j++) {
 143                         t2 = nf_ct_ext_types[j];
 144                         if (t2 == NULL || t2 == t1 ||
 145                             (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
 146                                 continue;
 147
 148                         t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
 149                                          + t2->len;
 150                 }
 151         }
 152 }
 153
 154 /* This MUST be called in process context. */
 155 int nf_ct_extend_register(struct nf_ct_ext_type *type)
 156 {
 157         int ret = 0;
 158
 159         mutex_lock(&nf_ct_ext_type_mutex);
 160         if (nf_ct_ext_types[type->id]) {
 161                 ret = -EBUSY;
 162                 goto out;
 163         }
 164
 165         /* This ensures that nf_ct_ext_create() can allocate enough area
 166            before updating alloc_size */
 167         type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
 168                            + type->len;
 169         rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 170         update_alloc_size(type);
 171 out:
 172         mutex_unlock(&nf_ct_ext_type_mutex);
 173         return ret;
 174 }
 175 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 176
 177 /* This MUST be called in process context. */
 178 void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 179 {
 180         mutex_lock(&nf_ct_ext_type_mutex);
 181         rcu_assign_pointer(nf_ct_ext_types[type->id], NULL);
 182         update_alloc_size(type);
 183         mutex_unlock(&nf_ct_ext_type_mutex);
 184         synchronize_rcu();
 185 }
 186 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);