net/netfilter/nf_conntrack_extend.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Structure dynamic extension infrastructure
   3  * Copyright (C) 2004 Rusty Russell IBM Corporation
   4  * Copyright (C) 2007 Netfilter Core Team <coreteam@netfilter.org>
   5  * Copyright (C) 2007 USAGI/WIDE Project <http://www.linux-ipv6.org>
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/kmemleak.h>
   9 #include <linux/module.h>
  10 #include <linux/mutex.h>
  11 #include <linux/rcupdate.h>
  12 #include <linux/slab.h>
  13 #include <linux/skbuff.h>
  14 #include <net/netfilter/nf_conntrack_extend.h>
  15
  16 static struct nf_ct_ext_type __rcu *nf_ct_ext_types[NF_CT_EXT_NUM];
  17 static DEFINE_MUTEX(nf_ct_ext_type_mutex);
  18 #define NF_CT_EXT_PREALLOC      128u /* conntrack events are on by default */
  19
  20 void nf_ct_ext_destroy(struct nf_conn *ct)
  21 {
  22         unsigned int i;
  23         struct nf_ct_ext_type *t;
  24
  25         for (i = 0; i < NF_CT_EXT_NUM; i++) {
  26                 rcu_read_lock();
  27                 t = rcu_dereference(nf_ct_ext_types[i]);
  28
  29                 /* Here the nf_ct_ext_type might have been unregisterd.
  30                  * I.e., it has responsible to cleanup private
  31                  * area in all conntracks when it is unregisterd.
  32                  */
  33                 if (t && t->destroy)
  34                         t->destroy(ct);
  35                 rcu_read_unlock();
  36         }
  37
  38         kfree(ct->ext);
  39 }
  40 EXPORT_SYMBOL(nf_ct_ext_destroy);
  41
  42 void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  43 {
  44         unsigned int newlen, newoff, oldlen, alloc;
  45         struct nf_ct_ext_type *t;
  46         struct nf_ct_ext *new;
  47
  48         /* Conntrack must not be confirmed to avoid races on reallocation. */
  49         WARN_ON(nf_ct_is_confirmed(ct));
  50
  51
  52         if (ct->ext) {
  53                 const struct nf_ct_ext *old = ct->ext;
  54
  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(ct->ext, alloc, gfp);
  75         if (!new)
  76                 return NULL;
  77
  78         if (!ct->ext)
  79                 memset(new->offset, 0, sizeof(new->offset));
  80
  81         new->offset[id] = newoff;
  82         new->len = newlen;
  83         memset((void *)new + newoff, 0, newlen - newoff);
  84
  85         ct->ext = new;
  86         return (void *)new + newoff;
  87 }
  88 EXPORT_SYMBOL(nf_ct_ext_add);
  89
  90 /* This MUST be called in process context. */
  91 int nf_ct_extend_register(const struct nf_ct_ext_type *type)
  92 {
  93         int ret = 0;
  94
  95         mutex_lock(&nf_ct_ext_type_mutex);
  96         if (nf_ct_ext_types[type->id]) {
  97                 ret = -EBUSY;
  98                 goto out;
  99         }
 100
 101         rcu_assign_pointer(nf_ct_ext_types[type->id], type);
 102 out:
 103         mutex_unlock(&nf_ct_ext_type_mutex);
 104         return ret;
 105 }
 106 EXPORT_SYMBOL_GPL(nf_ct_extend_register);
 107
 108 /* This MUST be called in process context. */
 109 void nf_ct_extend_unregister(const struct nf_ct_ext_type *type)
 110 {
 111         mutex_lock(&nf_ct_ext_type_mutex);
 112         RCU_INIT_POINTER(nf_ct_ext_types[type->id], NULL);
 113         mutex_unlock(&nf_ct_ext_type_mutex);
 114         synchronize_rcu();
 115 }
 116 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);