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 #define NF_CT_EXT_PREALLOC      128u /* conntrack events are on by default */
  22
  23 void __nf_ct_ext_destroy(struct nf_conn *ct)
  24 {
  25         unsigned int i;
  26         struct nf_ct_ext_type *t;
  27         struct nf_ct_ext *ext = ct->ext;
  28
  29         for (i = 0; i < NF_CT_EXT_NUM; i++) {
  30                 if (!__nf_ct_ext_exist(ext, i))
  31                         continue;
  32
  33                 rcu_read_lock();
  34                 t = rcu_dereference(nf_ct_ext_types[i]);
  35
  36                 /* Here the nf_ct_ext_type might have been unregisterd.
  37                  * I.e., it has responsible to cleanup private
  38                  * area in all conntracks when it is unregisterd.
  39                  */
  40                 if (t && t->destroy)
  41                         t->destroy(ct);
  42                 rcu_read_unlock();
  43         }
  44 }
  45 EXPORT_SYMBOL(__nf_ct_ext_destroy);
  46
  47 static void *
  48 nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
  49 {
  50         unsigned int off, len, alloc;
  51         struct nf_ct_ext_type *t;
  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         rcu_read_unlock();
  63
  64         alloc = max(len, NF_CT_EXT_PREALLOC);
  65         *ext = kzalloc(alloc, 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 /* This MUST be called in process context. */
 119 int nf_ct_extend_register(struct nf_ct_ext_type *type)
 120 {
 121         int ret = 0;
 122
 123         mutex_lock(&nf_ct_ext_type_mutex);
 124         if (nf_ct_ext_types[type->id]) {
 125                 ret = -EBUSY;
 126                 goto out;
 127         }
 128
 129         rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 130 out:
 131         mutex_unlock(&nf_ct_ext_type_mutex);
 132         return ret;
 133 }
 134 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 135
 136 /* This MUST be called in process context. */
 137 void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 138 {
 139         mutex_lock(&nf_ct_ext_type_mutex);
 140         RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 141         mutex_unlock(&nf_ct_ext_type_mutex);
 142         synchronize_rcu();
 143 }
 144 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);