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Linux/net/netfilter/core.c

  1 /* netfilter.c: look after the filters for various protocols.
  2  * Heavily influenced by the old firewall.c by David Bonn and Alan Cox.
  3  *
  4  * Thanks to Rob `CmdrTaco' Malda for not influencing this code in any
  5  * way.
  6  *
  7  * Rusty Russell (C)2000 -- This code is GPL.
  8  * Patrick McHardy (c) 2006-2012
  9  */
 10 #include <linux/kernel.h>
 11 #include <linux/netfilter.h>
 12 #include <net/protocol.h>
 13 #include <linux/init.h>
 14 #include <linux/skbuff.h>
 15 #include <linux/wait.h>
 16 #include <linux/module.h>
 17 #include <linux/interrupt.h>
 18 #include <linux/if.h>
 19 #include <linux/netdevice.h>
 20 #include <linux/inetdevice.h>
 21 #include <linux/proc_fs.h>
 22 #include <linux/mutex.h>
 23 #include <linux/slab.h>
 24 #include <net/net_namespace.h>
 25 #include <net/sock.h>
 26 
 27 #include "nf_internals.h"
 28 
 29 static DEFINE_MUTEX(afinfo_mutex);
 30 
 31 const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO] __read_mostly;
 32 EXPORT_SYMBOL(nf_afinfo);
 33 const struct nf_ipv6_ops __rcu *nf_ipv6_ops __read_mostly;
 34 EXPORT_SYMBOL_GPL(nf_ipv6_ops);
 35 
 36 int nf_register_afinfo(const struct nf_afinfo *afinfo)
 37 {
 38         int err;
 39 
 40         err = mutex_lock_interruptible(&afinfo_mutex);
 41         if (err < 0)
 42                 return err;
 43         RCU_INIT_POINTER(nf_afinfo[afinfo->family], afinfo);
 44         mutex_unlock(&afinfo_mutex);
 45         return 0;
 46 }
 47 EXPORT_SYMBOL_GPL(nf_register_afinfo);
 48 
 49 void nf_unregister_afinfo(const struct nf_afinfo *afinfo)
 50 {
 51         mutex_lock(&afinfo_mutex);
 52         RCU_INIT_POINTER(nf_afinfo[afinfo->family], NULL);
 53         mutex_unlock(&afinfo_mutex);
 54         synchronize_rcu();
 55 }
 56 EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
 57 
 58 struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS] __read_mostly;
 59 EXPORT_SYMBOL(nf_hooks);
 60 
 61 #if defined(CONFIG_JUMP_LABEL)
 62 struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
 63 EXPORT_SYMBOL(nf_hooks_needed);
 64 #endif
 65 
 66 static DEFINE_MUTEX(nf_hook_mutex);
 67 
 68 int nf_register_hook(struct nf_hook_ops *reg)
 69 {
 70         struct nf_hook_ops *elem;
 71         int err;
 72 
 73         err = mutex_lock_interruptible(&nf_hook_mutex);
 74         if (err < 0)
 75                 return err;
 76         list_for_each_entry(elem, &nf_hooks[reg->pf][reg->hooknum], list) {
 77                 if (reg->priority < elem->priority)
 78                         break;
 79         }
 80         list_add_rcu(&reg->list, elem->list.prev);
 81         mutex_unlock(&nf_hook_mutex);
 82 #if defined(CONFIG_JUMP_LABEL)
 83         static_key_slow_inc(&nf_hooks_needed[reg->pf][reg->hooknum]);
 84 #endif
 85         return 0;
 86 }
 87 EXPORT_SYMBOL(nf_register_hook);
 88 
 89 void nf_unregister_hook(struct nf_hook_ops *reg)
 90 {
 91         mutex_lock(&nf_hook_mutex);
 92         list_del_rcu(&reg->list);
 93         mutex_unlock(&nf_hook_mutex);
 94 #if defined(CONFIG_JUMP_LABEL)
 95         static_key_slow_dec(&nf_hooks_needed[reg->pf][reg->hooknum]);
 96 #endif
 97         synchronize_net();
 98 }
 99 EXPORT_SYMBOL(nf_unregister_hook);
100 
101 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
102 {
103         unsigned int i;
104         int err = 0;
105 
106         for (i = 0; i < n; i++) {
107                 err = nf_register_hook(&reg[i]);
108                 if (err)
109                         goto err;
110         }
111         return err;
112 
113 err:
114         if (i > 0)
115                 nf_unregister_hooks(reg, i);
116         return err;
117 }
118 EXPORT_SYMBOL(nf_register_hooks);
119 
120 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
121 {
122         while (n-- > 0)
123                 nf_unregister_hook(&reg[n]);
124 }
125 EXPORT_SYMBOL(nf_unregister_hooks);
126 
127 unsigned int nf_iterate(struct list_head *head,
128                         struct sk_buff *skb,
129                         unsigned int hook,
130                         const struct net_device *indev,
131                         const struct net_device *outdev,
132                         struct nf_hook_ops **elemp,
133                         int (*okfn)(struct sk_buff *),
134                         int hook_thresh)
135 {
136         unsigned int verdict;
137 
138         /*
139          * The caller must not block between calls to this
140          * function because of risk of continuing from deleted element.
141          */
142         list_for_each_entry_continue_rcu((*elemp), head, list) {
143                 if (hook_thresh > (*elemp)->priority)
144                         continue;
145 
146                 /* Optimization: we don't need to hold module
147                    reference here, since function can't sleep. --RR */
148 repeat:
149                 verdict = (*elemp)->hook(*elemp, skb, indev, outdev, okfn);
150                 if (verdict != NF_ACCEPT) {
151 #ifdef CONFIG_NETFILTER_DEBUG
152                         if (unlikely((verdict & NF_VERDICT_MASK)
153                                                         > NF_MAX_VERDICT)) {
154                                 NFDEBUG("Evil return from %p(%u).\n",
155                                         (*elemp)->hook, hook);
156                                 continue;
157                         }
158 #endif
159                         if (verdict != NF_REPEAT)
160                                 return verdict;
161                         goto repeat;
162                 }
163         }
164         return NF_ACCEPT;
165 }
166 
167 
168 /* Returns 1 if okfn() needs to be executed by the caller,
169  * -EPERM for NF_DROP, 0 otherwise. */
170 int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
171                  struct net_device *indev,
172                  struct net_device *outdev,
173                  int (*okfn)(struct sk_buff *),
174                  int hook_thresh)
175 {
176         struct nf_hook_ops *elem;
177         unsigned int verdict;
178         int ret = 0;
179 
180         /* We may already have this, but read-locks nest anyway */
181         rcu_read_lock();
182 
183         elem = list_entry_rcu(&nf_hooks[pf][hook], struct nf_hook_ops, list);
184 next_hook:
185         verdict = nf_iterate(&nf_hooks[pf][hook], skb, hook, indev,
186                              outdev, &elem, okfn, hook_thresh);
187         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
188                 ret = 1;
189         } else if ((verdict & NF_VERDICT_MASK) == NF_DROP) {
190                 kfree_skb(skb);
191                 ret = NF_DROP_GETERR(verdict);
192                 if (ret == 0)
193                         ret = -EPERM;
194         } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
195                 int err = nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
196                                                 verdict >> NF_VERDICT_QBITS);
197                 if (err < 0) {
198                         if (err == -ECANCELED)
199                                 goto next_hook;
200                         if (err == -ESRCH &&
201                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
202                                 goto next_hook;
203                         kfree_skb(skb);
204                 }
205         }
206         rcu_read_unlock();
207         return ret;
208 }
209 EXPORT_SYMBOL(nf_hook_slow);
210 
211 
212 int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
213 {
214         if (writable_len > skb->len)
215                 return 0;
216 
217         /* Not exclusive use of packet?  Must copy. */
218         if (!skb_cloned(skb)) {
219                 if (writable_len <= skb_headlen(skb))
220                         return 1;
221         } else if (skb_clone_writable(skb, writable_len))
222                 return 1;
223 
224         if (writable_len <= skb_headlen(skb))
225                 writable_len = 0;
226         else
227                 writable_len -= skb_headlen(skb);
228 
229         return !!__pskb_pull_tail(skb, writable_len);
230 }
231 EXPORT_SYMBOL(skb_make_writable);
232 
233 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
234 /* This does not belong here, but locally generated errors need it if connection
235    tracking in use: without this, connection may not be in hash table, and hence
236    manufactured ICMP or RST packets will not be associated with it. */
237 void (*ip_ct_attach)(struct sk_buff *, const struct sk_buff *)
238                 __rcu __read_mostly;
239 EXPORT_SYMBOL(ip_ct_attach);
240 
241 void nf_ct_attach(struct sk_buff *new, const struct sk_buff *skb)
242 {
243         void (*attach)(struct sk_buff *, const struct sk_buff *);
244 
245         if (skb->nfct) {
246                 rcu_read_lock();
247                 attach = rcu_dereference(ip_ct_attach);
248                 if (attach)
249                         attach(new, skb);
250                 rcu_read_unlock();
251         }
252 }
253 EXPORT_SYMBOL(nf_ct_attach);
254 
255 void (*nf_ct_destroy)(struct nf_conntrack *) __rcu __read_mostly;
256 EXPORT_SYMBOL(nf_ct_destroy);
257 
258 void nf_conntrack_destroy(struct nf_conntrack *nfct)
259 {
260         void (*destroy)(struct nf_conntrack *);
261 
262         rcu_read_lock();
263         destroy = rcu_dereference(nf_ct_destroy);
264         BUG_ON(destroy == NULL);
265         destroy(nfct);
266         rcu_read_unlock();
267 }
268 EXPORT_SYMBOL(nf_conntrack_destroy);
269 
270 struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
271 EXPORT_SYMBOL_GPL(nfq_ct_hook);
272 
273 struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook __read_mostly;
274 EXPORT_SYMBOL_GPL(nfq_ct_nat_hook);
275 
276 #endif /* CONFIG_NF_CONNTRACK */
277 
278 #ifdef CONFIG_NF_NAT_NEEDED
279 void (*nf_nat_decode_session_hook)(struct sk_buff *, struct flowi *);
280 EXPORT_SYMBOL(nf_nat_decode_session_hook);
281 #endif
282 
283 static int __net_init netfilter_net_init(struct net *net)
284 {
285 #ifdef CONFIG_PROC_FS
286         net->nf.proc_netfilter = proc_net_mkdir(net, "netfilter",
287                                                 net->proc_net);
288         if (!net->nf.proc_netfilter) {
289                 if (!net_eq(net, &init_net))
290                         pr_err("cannot create netfilter proc entry");
291 
292                 return -ENOMEM;
293         }
294 #endif
295         return 0;
296 }
297 
298 static void __net_exit netfilter_net_exit(struct net *net)
299 {
300         remove_proc_entry("netfilter", net->proc_net);
301 }
302 
303 static struct pernet_operations netfilter_net_ops = {
304         .init = netfilter_net_init,
305         .exit = netfilter_net_exit,
306 };
307 
308 int __init netfilter_init(void)
309 {
310         int i, h, ret;
311 
312         for (i = 0; i < ARRAY_SIZE(nf_hooks); i++) {
313                 for (h = 0; h < NF_MAX_HOOKS; h++)
314                         INIT_LIST_HEAD(&nf_hooks[i][h]);
315         }
316 
317         ret = register_pernet_subsys(&netfilter_net_ops);
318         if (ret < 0)
319                 goto err;
320 
321         ret = netfilter_log_init();
322         if (ret < 0)
323                 goto err_pernet;
324 
325         return 0;
326 err_pernet:
327         unregister_pernet_subsys(&netfilter_net_ops);
328 err:
329         return ret;
330 }
331 

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