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