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 /* Horrible trick to figure out smallest amount worth kmallocing. */
  23 #define CACHE(x) (x) + 0 *
  24 enum {
  25         NF_CT_EXT_MIN_SIZE =
  26 #include <linux/kmalloc_sizes.h>
  27         1 };
  28 #undef CACHE
  29
  30 void __nf_ct_ext_destroy(struct nf_conn *ct)
  31 {
  32         unsigned int i;
  33         struct nf_ct_ext_type *t;
  34
  35         for (i = 0; i < NF_CT_EXT_NUM; i++) {
  36                 if (!nf_ct_ext_exist(ct, i))
  37                         continue;
  38
  39                 rcu_read_lock();
  40                 t = rcu_dereference(nf_ct_ext_types[i]);
  41
  42                 /* Here the nf_ct_ext_type might have been unregisterd.
  43                  * I.e., it has responsible to cleanup private
  44                  * area in all conntracks when it is unregisterd.
  45                  */
  46                 if (t && t->destroy)
  47                         t->destroy(ct);
  48                 rcu_read_unlock();
  49         }
  50 }
  51 EXPORT_SYMBOL(__nf_ct_ext_destroy);
  52
  53 static void *
  54 nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
  55 {
  56         unsigned int off, len, real_len;
  57         struct nf_ct_ext_type *t;
  58
  59         rcu_read_lock();
  60         t = rcu_dereference(nf_ct_ext_types[id]);
  61         BUG_ON(t == NULL);
  62         off = ALIGN(sizeof(struct nf_ct_ext), t->align);
  63         len = off + t->len;
  64         real_len = t->alloc_size;
  65         rcu_read_unlock();
  66
  67         *ext = kzalloc(real_len, gfp);
  68         if (!*ext)
  69                 return NULL;
  70
  71         (*ext)->offset[id] = off;
  72         (*ext)->len = len;
  73         (*ext)->real_len = real_len;
  74
  75         return (void *)(*ext) + off;
  76 }
  77
  78 void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  79 {
  80         struct nf_ct_ext *new;
  81         int i, newlen, newoff;
  82         struct nf_ct_ext_type *t;
  83
  84         if (!ct->ext)
  85                 return nf_ct_ext_create(&ct->ext, id, gfp);
  86
  87         if (nf_ct_ext_exist(ct, id))
  88                 return NULL;
  89
  90         rcu_read_lock();
  91         t = rcu_dereference(nf_ct_ext_types[id]);
  92         BUG_ON(t == NULL);
  93
  94         newoff = ALIGN(ct->ext->len, t->align);
  95         newlen = newoff + t->len;
  96         rcu_read_unlock();
  97
  98         if (newlen >= ct->ext->real_len) {
  99                 new = kmalloc(newlen, gfp);
 100                 if (!new)
 101                         return NULL;
 102
 103                 memcpy(new, ct->ext, ct->ext->len);
 104
 105                 for (i = 0; i < NF_CT_EXT_NUM; i++) {
 106                         if (!nf_ct_ext_exist(ct, i))
 107                                 continue;
 108
 109                         rcu_read_lock();
 110                         t = rcu_dereference(nf_ct_ext_types[i]);
 111                         if (t && t->move)
 112                                 t->move(ct, ct->ext + ct->ext->offset[id]);
 113                         rcu_read_unlock();
 114                 }
 115                 kfree(ct->ext);
 116                 new->real_len = newlen;
 117                 ct->ext = new;
 118         }
 119
 120         ct->ext->offset[id] = newoff;
 121         ct->ext->len = newlen;
 122         memset((void *)ct->ext + newoff, 0, newlen - newoff);
 123         return (void *)ct->ext + newoff;
 124 }
 125 EXPORT_SYMBOL(__nf_ct_ext_add);
 126
 127 static void update_alloc_size(struct nf_ct_ext_type *type)
 128 {
 129         int i, j;
 130         struct nf_ct_ext_type *t1, *t2;
 131         enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
 132
 133         /* unnecessary to update all types */
 134         if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
 135                 min = type->id;
 136                 max = type->id;
 137         }
 138
 139         /* This assumes that extended areas in conntrack for the types
 140            whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
 141         for (i = min; i <= max; i++) {
 142                 t1 = nf_ct_ext_types[i];
 143                 if (!t1)
 144                         continue;
 145
 146                 t1->alloc_size = sizeof(struct nf_ct_ext)
 147                                  + ALIGN(sizeof(struct nf_ct_ext), t1->align)
 148                                  + t1->len;
 149                 for (j = 0; j < NF_CT_EXT_NUM; j++) {
 150                         t2 = nf_ct_ext_types[j];
 151                         if (t2 == NULL || t2 == t1 ||
 152                             (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
 153                                 continue;
 154
 155                         t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
 156                                          + t2->len;
 157                 }
 158                 if (t1->alloc_size < NF_CT_EXT_MIN_SIZE)
 159                         t1->alloc_size = NF_CT_EXT_MIN_SIZE;
 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         synchronize_rcu();
 194 }
 195 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);