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         INIT_RCU_HEAD(&(*ext)->rcu);
  63         (*ext)->offset[id] = off;
  64         (*ext)->len = len;
  65
  66         return (void *)(*ext) + off;
  67 }
  68
  69 static void __nf_ct_ext_free_rcu(struct rcu_head *head)
  70 {
  71         struct nf_ct_ext *ext = container_of(head, struct nf_ct_ext, rcu);
  72         kfree(ext);
  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 *new;
  78         int i, 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         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         new = __krealloc(ct->ext, newlen, gfp);
  99         if (!new)
 100                 return NULL;
 101
 102         if (new != ct->ext) {
 103                 for (i = 0; i < NF_CT_EXT_NUM; i++) {
 104                         if (!nf_ct_ext_exist(ct, i))
 105                                 continue;
 106
 107                         rcu_read_lock();
 108                         t = rcu_dereference(nf_ct_ext_types[i]);
 109                         if (t && t->move)
 110                                 t->move((void *)new + new->offset[i],
 111                                         (void *)ct->ext + ct->ext->offset[i]);
 112                         rcu_read_unlock();
 113                 }
 114                 call_rcu(&ct->ext->rcu, __nf_ct_ext_free_rcu);
 115                 ct->ext = new;
 116         }
 117
 118         new->offset[id] = newoff;
 119         new->len = newlen;
 120         memset((void *)new + newoff, 0, newlen - newoff);
 121         return (void *)new + newoff;
 122 }
 123 EXPORT_SYMBOL(__nf_ct_ext_add);
 124
 125 static void update_alloc_size(struct nf_ct_ext_type *type)
 126 {
 127         int i, j;
 128         struct nf_ct_ext_type *t1, *t2;
 129         enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
 130
 131         /* unnecessary to update all types */
 132         if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
 133                 min = type->id;
 134                 max = type->id;
 135         }
 136
 137         /* This assumes that extended areas in conntrack for the types
 138            whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
 139         for (i = min; i <= max; i++) {
 140                 t1 = nf_ct_ext_types[i];
 141                 if (!t1)
 142                         continue;
 143
 144                 t1->alloc_size = sizeof(struct nf_ct_ext)
 145                                  + ALIGN(sizeof(struct nf_ct_ext), t1->align)
 146                                  + t1->len;
 147                 for (j = 0; j < NF_CT_EXT_NUM; j++) {
 148                         t2 = nf_ct_ext_types[j];
 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_assign_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);