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
  28         for (i = 0; i < NF_CT_EXT_NUM; i++) {
  29                 rcu_read_lock();
  30                 t = rcu_dereference(nf_ct_ext_types[i]);
  31
  32                 /* Here the nf_ct_ext_type might have been unregisterd.
  33                  * I.e., it has responsible to cleanup private
  34                  * area in all conntracks when it is unregisterd.
  35                  */
  36                 if (t && t->destroy)
  37                         t->destroy(ct);
  38                 rcu_read_unlock();
  39         }
  40 }
  41 EXPORT_SYMBOL(nf_ct_ext_destroy);
  42
  43 void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  44 {
  45         unsigned int newlen, newoff, oldlen, alloc;
  46         struct nf_ct_ext *old, *new;
  47         struct nf_ct_ext_type *t;
  48
  49         /* Conntrack must not be confirmed to avoid races on reallocation. */
  50         NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
  51
  52         old = ct->ext;
  53
  54         if (old) {
  55                 if (__nf_ct_ext_exist(old, id))
  56                         return NULL;
  57                 oldlen = old->len;
  58         } else {
  59                 oldlen = sizeof(*new);
  60         }
  61
  62         rcu_read_lock();
  63         t = rcu_dereference(nf_ct_ext_types[id]);
  64         if (!t) {
  65                 rcu_read_unlock();
  66                 return NULL;
  67         }
  68
  69         newoff = ALIGN(oldlen, t->align);
  70         newlen = newoff + t->len;
  71         rcu_read_unlock();
  72
  73         alloc = max(newlen, NF_CT_EXT_PREALLOC);
  74         new = __krealloc(old, alloc, gfp);
  75         if (!new)
  76                 return NULL;
  77
  78         if (!old) {
  79                 memset(new->offset, 0, sizeof(new->offset));
  80                 ct->ext = new;
  81         } else if (new != old) {
  82                 kfree_rcu(old, rcu);
  83                 rcu_assign_pointer(ct->ext, new);
  84         }
  85
  86         new->offset[id] = newoff;
  87         new->len = newlen;
  88         memset((void *)new + newoff, 0, newlen - newoff);
  89         return (void *)new + newoff;
  90 }
  91 EXPORT_SYMBOL(nf_ct_ext_add);
  92
  93 /* This MUST be called in process context. */
  94 int nf_ct_extend_register(const struct nf_ct_ext_type *type)
  95 {
  96         int ret = 0;
  97
  98         mutex_lock(&nf_ct_ext_type_mutex);
  99         if (nf_ct_ext_types[type->id]) {
 100                 ret = -EBUSY;
 101                 goto out;
 102         }
 103
 104         rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 105 out:
 106         mutex_unlock(&nf_ct_ext_type_mutex);
 107         return ret;
 108 }
 109 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 110
 111 /* This MUST be called in process context. */
 112 void nf_ct_extend_unregister(const struct nf_ct_ext_type *type)
 113 {
 114         mutex_lock(&nf_ct_ext_type_mutex);
 115         RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 116         mutex_unlock(&nf_ct_ext_type_mutex);
 117         synchronize_rcu();
 118 }
 119 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);