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

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