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Linux/net/netfilter/nf_conntrack_extend.c

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  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 
 22 void __nf_ct_ext_destroy(struct nf_conn *ct)
 23 {
 24         unsigned int i;
 25         struct nf_ct_ext_type *t;
 26         struct nf_ct_ext *ext = ct->ext;
 27 
 28         for (i = 0; i < NF_CT_EXT_NUM; i++) {
 29                 if (!__nf_ct_ext_exist(ext, i))
 30                         continue;
 31 
 32                 rcu_read_lock();
 33                 t = rcu_dereference(nf_ct_ext_types[i]);
 34 
 35                 /* Here the nf_ct_ext_type might have been unregisterd.
 36                  * I.e., it has responsible to cleanup private
 37                  * area in all conntracks when it is unregisterd.
 38                  */
 39                 if (t && t->destroy)
 40                         t->destroy(ct);
 41                 rcu_read_unlock();
 42         }
 43 }
 44 EXPORT_SYMBOL(__nf_ct_ext_destroy);
 45 
 46 static void *
 47 nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id,
 48                  size_t var_alloc_len, gfp_t gfp)
 49 {
 50         unsigned int off, len;
 51         struct nf_ct_ext_type *t;
 52         size_t alloc_size;
 53 
 54         rcu_read_lock();
 55         t = rcu_dereference(nf_ct_ext_types[id]);
 56         BUG_ON(t == NULL);
 57         off = ALIGN(sizeof(struct nf_ct_ext), t->align);
 58         len = off + t->len + var_alloc_len;
 59         alloc_size = t->alloc_size + var_alloc_len;
 60         rcu_read_unlock();
 61 
 62         *ext = kzalloc(alloc_size, gfp);
 63         if (!*ext)
 64                 return NULL;
 65 
 66         (*ext)->offset[id] = off;
 67         (*ext)->len = len;
 68 
 69         return (void *)(*ext) + off;
 70 }
 71 
 72 void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id,
 73                              size_t var_alloc_len, gfp_t gfp)
 74 {
 75         struct nf_ct_ext *old, *new;
 76         int i, newlen, newoff;
 77         struct nf_ct_ext_type *t;
 78 
 79         /* Conntrack must not be confirmed to avoid races on reallocation. */
 80         NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
 81 
 82         old = ct->ext;
 83         if (!old)
 84                 return nf_ct_ext_create(&ct->ext, id, var_alloc_len, gfp);
 85 
 86         if (__nf_ct_ext_exist(old, id))
 87                 return NULL;
 88 
 89         rcu_read_lock();
 90         t = rcu_dereference(nf_ct_ext_types[id]);
 91         BUG_ON(t == NULL);
 92 
 93         newoff = ALIGN(old->len, t->align);
 94         newlen = newoff + t->len + var_alloc_len;
 95         rcu_read_unlock();
 96 
 97         new = __krealloc(old, newlen, gfp);
 98         if (!new)
 99                 return NULL;
100 
101         if (new != old) {
102                 for (i = 0; i < NF_CT_EXT_NUM; i++) {
103                         if (!__nf_ct_ext_exist(old, i))
104                                 continue;
105 
106                         rcu_read_lock();
107                         t = rcu_dereference(nf_ct_ext_types[i]);
108                         if (t && t->move)
109                                 t->move((void *)new + new->offset[i],
110                                         (void *)old + old->offset[i]);
111                         rcu_read_unlock();
112                 }
113                 kfree_rcu(old, rcu);
114                 ct->ext = new;
115         }
116 
117         new->offset[id] = newoff;
118         new->len = newlen;
119         memset((void *)new + newoff, 0, newlen - newoff);
120         return (void *)new + newoff;
121 }
122 EXPORT_SYMBOL(__nf_ct_ext_add_length);
123 
124 static void update_alloc_size(struct nf_ct_ext_type *type)
125 {
126         int i, j;
127         struct nf_ct_ext_type *t1, *t2;
128         enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
129 
130         /* unnecessary to update all types */
131         if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
132                 min = type->id;
133                 max = type->id;
134         }
135 
136         /* This assumes that extended areas in conntrack for the types
137            whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
138         for (i = min; i <= max; i++) {
139                 t1 = rcu_dereference_protected(nf_ct_ext_types[i],
140                                 lockdep_is_held(&nf_ct_ext_type_mutex));
141                 if (!t1)
142                         continue;
143 
144                 t1->alloc_size = ALIGN(sizeof(struct nf_ct_ext), t1->align) +
145                                  t1->len;
146                 for (j = 0; j < NF_CT_EXT_NUM; j++) {
147                         t2 = rcu_dereference_protected(nf_ct_ext_types[j],
148                                 lockdep_is_held(&nf_ct_ext_type_mutex));
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_INIT_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);
192 

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