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/kmemleak.h>
  13 #include <linux/module.h>
  14 #include <linux/mutex.h>
  15 #include <linux/rcupdate.h>
  16 #include <linux/slab.h>
  17 #include <linux/skbuff.h>
  18 #include <net/netfilter/nf_conntrack_extend.h>
  19
  20 static struct nf_ct_ext_type __rcu *nf_ct_ext_types[NF_CT_EXT_NUM];
  21 static DEFINE_MUTEX(nf_ct_ext_type_mutex);
  22 #define NF_CT_EXT_PREALLOC      128u /* conntrack events are on by default */
  23
  24 void nf_ct_ext_destroy(struct nf_conn *ct)
  25 {
  26         unsigned int i;
  27         struct nf_ct_ext_type *t;
  28
  29         for (i = 0; i < NF_CT_EXT_NUM; i++) {
  30                 rcu_read_lock();
  31                 t = rcu_dereference(nf_ct_ext_types[i]);
  32
  33                 /* Here the nf_ct_ext_type might have been unregisterd.
  34                  * I.e., it has responsible to cleanup private
  35                  * area in all conntracks when it is unregisterd.
  36                  */
  37                 if (t && t->destroy)
  38                         t->destroy(ct);
  39                 rcu_read_unlock();
  40         }
  41 }
  42 EXPORT_SYMBOL(nf_ct_ext_destroy);
  43
  44 void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  45 {
  46         unsigned int newlen, newoff, oldlen, alloc;
  47         struct nf_ct_ext *old, *new;
  48         struct nf_ct_ext_type *t;
  49
  50         /* Conntrack must not be confirmed to avoid races on reallocation. */
  51         WARN_ON(nf_ct_is_confirmed(ct));
  52
  53         old = ct->ext;
  54
  55         if (old) {
  56                 if (__nf_ct_ext_exist(old, id))
  57                         return NULL;
  58                 oldlen = old->len;
  59         } else {
  60                 oldlen = sizeof(*new);
  61         }
  62
  63         rcu_read_lock();
  64         t = rcu_dereference(nf_ct_ext_types[id]);
  65         if (!t) {
  66                 rcu_read_unlock();
  67                 return NULL;
  68         }
  69
  70         newoff = ALIGN(oldlen, t->align);
  71         newlen = newoff + t->len;
  72         rcu_read_unlock();
  73
  74         alloc = max(newlen, NF_CT_EXT_PREALLOC);
  75         kmemleak_not_leak(old);
  76         new = __krealloc(old, alloc, gfp);
  77         if (!new)
  78                 return NULL;
  79
  80         if (!old) {
  81                 memset(new->offset, 0, sizeof(new->offset));
  82                 ct->ext = new;
  83         } else if (new != old) {
  84                 kfree_rcu(old, rcu);
  85                 rcu_assign_pointer(ct->ext, new);
  86         }
  87
  88         new->offset[id] = newoff;
  89         new->len = newlen;
  90         memset((void *)new + newoff, 0, newlen - newoff);
  91         return (void *)new + newoff;
  92 }
  93 EXPORT_SYMBOL(nf_ct_ext_add);
  94
  95 /* This MUST be called in process context. */
  96 int nf_ct_extend_register(const struct nf_ct_ext_type *type)
  97 {
  98         int ret = 0;
  99
 100         mutex_lock(&nf_ct_ext_type_mutex);
 101         if (nf_ct_ext_types[type->id]) {
 102                 ret = -EBUSY;
 103                 goto out;
 104         }
 105
 106         rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 107 out:
 108         mutex_unlock(&nf_ct_ext_type_mutex);
 109         return ret;
 110 }
 111 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 112
 113 /* This MUST be called in process context. */
 114 void nf_ct_extend_unregister(const struct nf_ct_ext_type *type)
 115 {
 116         mutex_lock(&nf_ct_ext_type_mutex);
 117         RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 118         mutex_unlock(&nf_ct_ext_type_mutex);
 119         synchronize_rcu();
 120 }
 121 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);