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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/netfilter_ipv6.h>
 21 #include <linux/inetdevice.h>
 22 #include <linux/proc_fs.h>
 23 #include <linux/mutex.h>
 24 #include <linux/slab.h>
 25 #include <net/net_namespace.h>
 26 #include <net/sock.h>
 27 
 28 #include "nf_internals.h"
 29 
 30 static DEFINE_MUTEX(afinfo_mutex);
 31 
 32 const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO] __read_mostly;
 33 EXPORT_SYMBOL(nf_afinfo);
 34 const struct nf_ipv6_ops __rcu *nf_ipv6_ops __read_mostly;
 35 EXPORT_SYMBOL_GPL(nf_ipv6_ops);
 36 
 37 int nf_register_afinfo(const struct nf_afinfo *afinfo)
 38 {
 39         mutex_lock(&afinfo_mutex);
 40         RCU_INIT_POINTER(nf_afinfo[afinfo->family], afinfo);
 41         mutex_unlock(&afinfo_mutex);
 42         return 0;
 43 }
 44 EXPORT_SYMBOL_GPL(nf_register_afinfo);
 45 
 46 void nf_unregister_afinfo(const struct nf_afinfo *afinfo)
 47 {
 48         mutex_lock(&afinfo_mutex);
 49         RCU_INIT_POINTER(nf_afinfo[afinfo->family], NULL);
 50         mutex_unlock(&afinfo_mutex);
 51         synchronize_rcu();
 52 }
 53 EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
 54 
 55 struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS] __read_mostly;
 56 EXPORT_SYMBOL(nf_hooks);
 57 
 58 #ifdef HAVE_JUMP_LABEL
 59 struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
 60 EXPORT_SYMBOL(nf_hooks_needed);
 61 #endif
 62 
 63 static DEFINE_MUTEX(nf_hook_mutex);
 64 
 65 int nf_register_hook(struct nf_hook_ops *reg)
 66 {
 67         struct nf_hook_ops *elem;
 68 
 69         mutex_lock(&nf_hook_mutex);
 70         list_for_each_entry(elem, &nf_hooks[reg->pf][reg->hooknum], list) {
 71                 if (reg->priority < elem->priority)
 72                         break;
 73         }
 74         list_add_rcu(&reg->list, elem->list.prev);
 75         mutex_unlock(&nf_hook_mutex);
 76 #ifdef HAVE_JUMP_LABEL
 77         static_key_slow_inc(&nf_hooks_needed[reg->pf][reg->hooknum]);
 78 #endif
 79         return 0;
 80 }
 81 EXPORT_SYMBOL(nf_register_hook);
 82 
 83 void nf_unregister_hook(struct nf_hook_ops *reg)
 84 {
 85         mutex_lock(&nf_hook_mutex);
 86         list_del_rcu(&reg->list);
 87         mutex_unlock(&nf_hook_mutex);
 88 #ifdef HAVE_JUMP_LABEL
 89         static_key_slow_dec(&nf_hooks_needed[reg->pf][reg->hooknum]);
 90 #endif
 91         synchronize_net();
 92 }
 93 EXPORT_SYMBOL(nf_unregister_hook);
 94 
 95 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
 96 {
 97         unsigned int i;
 98         int err = 0;
 99 
100         for (i = 0; i < n; i++) {
101                 err = nf_register_hook(&reg[i]);
102                 if (err)
103                         goto err;
104         }
105         return err;
106 
107 err:
108         if (i > 0)
109                 nf_unregister_hooks(reg, i);
110         return err;
111 }
112 EXPORT_SYMBOL(nf_register_hooks);
113 
114 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
115 {
116         while (n-- > 0)
117                 nf_unregister_hook(&reg[n]);
118 }
119 EXPORT_SYMBOL(nf_unregister_hooks);
120 
121 unsigned int nf_iterate(struct list_head *head,
122                         struct sk_buff *skb,
123                         struct nf_hook_state *state,
124                         struct nf_hook_ops **elemp)
125 {
126         unsigned int verdict;
127 
128         /*
129          * The caller must not block between calls to this
130          * function because of risk of continuing from deleted element.
131          */
132         list_for_each_entry_continue_rcu((*elemp), head, list) {
133                 if (state->thresh > (*elemp)->priority)
134                         continue;
135 
136                 /* Optimization: we don't need to hold module
137                    reference here, since function can't sleep. --RR */
138 repeat:
139                 verdict = (*elemp)->hook(*elemp, skb, state);
140                 if (verdict != NF_ACCEPT) {
141 #ifdef CONFIG_NETFILTER_DEBUG
142                         if (unlikely((verdict & NF_VERDICT_MASK)
143                                                         > NF_MAX_VERDICT)) {
144                                 NFDEBUG("Evil return from %p(%u).\n",
145                                         (*elemp)->hook, state->hook);
146                                 continue;
147                         }
148 #endif
149                         if (verdict != NF_REPEAT)
150                                 return verdict;
151                         goto repeat;
152                 }
153         }
154         return NF_ACCEPT;
155 }
156 
157 
158 /* Returns 1 if okfn() needs to be executed by the caller,
159  * -EPERM for NF_DROP, 0 otherwise. */
160 int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state)
161 {
162         struct nf_hook_ops *elem;
163         unsigned int verdict;
164         int ret = 0;
165 
166         /* We may already have this, but read-locks nest anyway */
167         rcu_read_lock();
168 
169         elem = list_entry_rcu(&nf_hooks[state->pf][state->hook],
170                               struct nf_hook_ops, list);
171 next_hook:
172         verdict = nf_iterate(&nf_hooks[state->pf][state->hook], skb, state,
173                              &elem);
174         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
175                 ret = 1;
176         } else if ((verdict & NF_VERDICT_MASK) == NF_DROP) {
177                 kfree_skb(skb);
178                 ret = NF_DROP_GETERR(verdict);
179                 if (ret == 0)
180                         ret = -EPERM;
181         } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
182                 int err = nf_queue(skb, elem, state,
183                                    verdict >> NF_VERDICT_QBITS);
184                 if (err < 0) {
185                         if (err == -ECANCELED)
186                                 goto next_hook;
187                         if (err == -ESRCH &&
188                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
189                                 goto next_hook;
190                         kfree_skb(skb);
191                 }
192         }
193         rcu_read_unlock();
194         return ret;
195 }
196 EXPORT_SYMBOL(nf_hook_slow);
197 
198 
199 int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
200 {
201         if (writable_len > skb->len)
202                 return 0;
203 
204         /* Not exclusive use of packet?  Must copy. */
205         if (!skb_cloned(skb)) {
206                 if (writable_len <= skb_headlen(skb))
207                         return 1;
208         } else if (skb_clone_writable(skb, writable_len))
209                 return 1;
210 
211         if (writable_len <= skb_headlen(skb))
212                 writable_len = 0;
213         else
214                 writable_len -= skb_headlen(skb);
215 
216         return !!__pskb_pull_tail(skb, writable_len);
217 }
218 EXPORT_SYMBOL(skb_make_writable);
219 
220 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
221 /* This does not belong here, but locally generated errors need it if connection
222    tracking in use: without this, connection may not be in hash table, and hence
223    manufactured ICMP or RST packets will not be associated with it. */
224 void (*ip_ct_attach)(struct sk_buff *, const struct sk_buff *)
225                 __rcu __read_mostly;
226 EXPORT_SYMBOL(ip_ct_attach);
227 
228 void nf_ct_attach(struct sk_buff *new, const struct sk_buff *skb)
229 {
230         void (*attach)(struct sk_buff *, const struct sk_buff *);
231 
232         if (skb->nfct) {
233                 rcu_read_lock();
234                 attach = rcu_dereference(ip_ct_attach);
235                 if (attach)
236                         attach(new, skb);
237                 rcu_read_unlock();
238         }
239 }
240 EXPORT_SYMBOL(nf_ct_attach);
241 
242 void (*nf_ct_destroy)(struct nf_conntrack *) __rcu __read_mostly;
243 EXPORT_SYMBOL(nf_ct_destroy);
244 
245 void nf_conntrack_destroy(struct nf_conntrack *nfct)
246 {
247         void (*destroy)(struct nf_conntrack *);
248 
249         rcu_read_lock();
250         destroy = rcu_dereference(nf_ct_destroy);
251         BUG_ON(destroy == NULL);
252         destroy(nfct);
253         rcu_read_unlock();
254 }
255 EXPORT_SYMBOL(nf_conntrack_destroy);
256 
257 struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
258 EXPORT_SYMBOL_GPL(nfq_ct_hook);
259 
260 struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook __read_mostly;
261 EXPORT_SYMBOL_GPL(nfq_ct_nat_hook);
262 
263 #endif /* CONFIG_NF_CONNTRACK */
264 
265 #ifdef CONFIG_NF_NAT_NEEDED
266 void (*nf_nat_decode_session_hook)(struct sk_buff *, struct flowi *);
267 EXPORT_SYMBOL(nf_nat_decode_session_hook);
268 #endif
269 
270 static int __net_init netfilter_net_init(struct net *net)
271 {
272 #ifdef CONFIG_PROC_FS
273         net->nf.proc_netfilter = proc_net_mkdir(net, "netfilter",
274                                                 net->proc_net);
275         if (!net->nf.proc_netfilter) {
276                 if (!net_eq(net, &init_net))
277                         pr_err("cannot create netfilter proc entry");
278 
279                 return -ENOMEM;
280         }
281 #endif
282         return 0;
283 }
284 
285 static void __net_exit netfilter_net_exit(struct net *net)
286 {
287         remove_proc_entry("netfilter", net->proc_net);
288 }
289 
290 static struct pernet_operations netfilter_net_ops = {
291         .init = netfilter_net_init,
292         .exit = netfilter_net_exit,
293 };
294 
295 int __init netfilter_init(void)
296 {
297         int i, h, ret;
298 
299         for (i = 0; i < ARRAY_SIZE(nf_hooks); i++) {
300                 for (h = 0; h < NF_MAX_HOOKS; h++)
301                         INIT_LIST_HEAD(&nf_hooks[i][h]);
302         }
303 
304         ret = register_pernet_subsys(&netfilter_net_ops);
305         if (ret < 0)
306                 goto err;
307 
308         ret = netfilter_log_init();
309         if (ret < 0)
310                 goto err_pernet;
311 
312         return 0;
313 err_pernet:
314         unregister_pernet_subsys(&netfilter_net_ops);
315 err:
316         return ret;
317 }
318 

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