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         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
  71 static void __nf_ct_ext_free_rcu(struct rcu_head *head)
  72 {
  73         struct nf_ct_ext *ext = container_of(head, struct nf_ct_ext, rcu);
  74         kfree(ext);
  75 }
  76
  77 void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  78 {
  79         struct nf_ct_ext *old, *new;
  80         int i, 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, 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         BUG_ON(t == NULL);
  96
  97         newoff = ALIGN(old->len, t->align);
  98         newlen = newoff + t->len;
  99         rcu_read_unlock();
 100
 101         new = __krealloc(old, newlen, gfp);
 102         if (!new)
 103                 return NULL;
 104
 105         if (new != old) {
 106                 for (i = 0; i < NF_CT_EXT_NUM; i++) {
 107                         if (!__nf_ct_ext_exist(old, i))
 108                                 continue;
 109
 110                         rcu_read_lock();
 111                         t = rcu_dereference(nf_ct_ext_types[i]);
 112                         if (t && t->move)
 113                                 t->move((void *)new + new->offset[i],
 114                                         (void *)old + old->offset[i]);
 115                         rcu_read_unlock();
 116                 }
 117                 call_rcu(&old->rcu, __nf_ct_ext_free_rcu);
 118                 ct->ext = new;
 119         }
 120
 121         new->offset[id] = newoff;
 122         new->len = newlen;
 123         memset((void *)new + newoff, 0, newlen - newoff);
 124         return (void *)new + newoff;
 125 }
 126 EXPORT_SYMBOL(__nf_ct_ext_add);
 127
 128 static void update_alloc_size(struct nf_ct_ext_type *type)
 129 {
 130         int i, j;
 131         struct nf_ct_ext_type *t1, *t2;
 132         enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
 133
 134         /* unnecessary to update all types */
 135         if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
 136                 min = type->id;
 137                 max = type->id;
 138         }
 139
 140         /* This assumes that extended areas in conntrack for the types
 141            whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
 142         for (i = min; i <= max; i++) {
 143                 t1 = rcu_dereference_protected(nf_ct_ext_types[i],
 144                                 lockdep_is_held(&nf_ct_ext_type_mutex));
 145                 if (!t1)
 146                         continue;
 147
 148                 t1->alloc_size = ALIGN(sizeof(struct nf_ct_ext), t1->align) +
 149                                  t1->len;
 150                 for (j = 0; j < NF_CT_EXT_NUM; j++) {
 151                         t2 = rcu_dereference_protected(nf_ct_ext_types[j],
 152                                 lockdep_is_held(&nf_ct_ext_type_mutex));
 153                         if (t2 == NULL || t2 == t1 ||
 154                             (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
 155                                 continue;
 156
 157                         t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
 158                                          + t2->len;
 159                 }
 160         }
 161 }
 162
 163 /* This MUST be called in process context. */
 164 int nf_ct_extend_register(struct nf_ct_ext_type *type)
 165 {
 166         int ret = 0;
 167
 168         mutex_lock(&nf_ct_ext_type_mutex);
 169         if (nf_ct_ext_types[type->id]) {
 170                 ret = -EBUSY;
 171                 goto out;
 172         }
 173
 174         /* This ensures that nf_ct_ext_create() can allocate enough area
 175            before updating alloc_size */
 176         type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
 177                            + type->len;
 178         rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 179         update_alloc_size(type);
 180 out:
 181         mutex_unlock(&nf_ct_ext_type_mutex);
 182         return ret;
 183 }
 184 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 185
 186 /* This MUST be called in process context. */
 187 void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 188 {
 189         mutex_lock(&nf_ct_ext_type_mutex);
 190         rcu_assign_pointer(nf_ct_ext_types[type->id], NULL);
 191         update_alloc_size(type);
 192         mutex_unlock(&nf_ct_ext_type_mutex);
 193         rcu_barrier(); /* Wait for completion of call_rcu()'s */
 194 }
 195 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);