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Linux/net/netfilter/core.c

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  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 <net/net_namespace.h>
 23 #include <net/sock.h>
 24 
 25 #include "nf_internals.h"
 26 
 27 static DEFINE_MUTEX(afinfo_mutex);
 28 
 29 const struct nf_afinfo *nf_afinfo[NFPROTO_NUMPROTO] __read_mostly;
 30 EXPORT_SYMBOL(nf_afinfo);
 31 
 32 int nf_register_afinfo(const struct nf_afinfo *afinfo)
 33 {
 34         int err;
 35 
 36         err = mutex_lock_interruptible(&afinfo_mutex);
 37         if (err < 0)
 38                 return err;
 39         rcu_assign_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_assign_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 static DEFINE_MUTEX(nf_hook_mutex);
 57 
 58 int nf_register_hook(struct nf_hook_ops *reg)
 59 {
 60         struct nf_hook_ops *elem;
 61         int err;
 62 
 63         err = mutex_lock_interruptible(&nf_hook_mutex);
 64         if (err < 0)
 65                 return err;
 66         list_for_each_entry(elem, &nf_hooks[reg->pf][reg->hooknum], list) {
 67                 if (reg->priority < elem->priority)
 68                         break;
 69         }
 70         list_add_rcu(&reg->list, elem->list.prev);
 71         mutex_unlock(&nf_hook_mutex);
 72         return 0;
 73 }
 74 EXPORT_SYMBOL(nf_register_hook);
 75 
 76 void nf_unregister_hook(struct nf_hook_ops *reg)
 77 {
 78         mutex_lock(&nf_hook_mutex);
 79         list_del_rcu(&reg->list);
 80         mutex_unlock(&nf_hook_mutex);
 81 
 82         synchronize_net();
 83 }
 84 EXPORT_SYMBOL(nf_unregister_hook);
 85 
 86 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
 87 {
 88         unsigned int i;
 89         int err = 0;
 90 
 91         for (i = 0; i < n; i++) {
 92                 err = nf_register_hook(&reg[i]);
 93                 if (err)
 94                         goto err;
 95         }
 96         return err;
 97 
 98 err:
 99         if (i > 0)
100                 nf_unregister_hooks(reg, i);
101         return err;
102 }
103 EXPORT_SYMBOL(nf_register_hooks);
104 
105 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
106 {
107         unsigned int i;
108 
109         for (i = 0; i < n; i++)
110                 nf_unregister_hook(&reg[i]);
111 }
112 EXPORT_SYMBOL(nf_unregister_hooks);
113 
114 unsigned int nf_iterate(struct list_head *head,
115                         struct sk_buff *skb,
116                         unsigned int hook,
117                         const struct net_device *indev,
118                         const struct net_device *outdev,
119                         struct list_head **i,
120                         int (*okfn)(struct sk_buff *),
121                         int hook_thresh)
122 {
123         unsigned int verdict;
124 
125         /*
126          * The caller must not block between calls to this
127          * function because of risk of continuing from deleted element.
128          */
129         list_for_each_continue_rcu(*i, head) {
130                 struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
131 
132                 if (hook_thresh > elem->priority)
133                         continue;
134 
135                 /* Optimization: we don't need to hold module
136                    reference here, since function can't sleep. --RR */
137                 verdict = elem->hook(hook, skb, indev, outdev, okfn);
138                 if (verdict != NF_ACCEPT) {
139 #ifdef CONFIG_NETFILTER_DEBUG
140                         if (unlikely((verdict & NF_VERDICT_MASK)
141                                                         > NF_MAX_VERDICT)) {
142                                 NFDEBUG("Evil return from %p(%u).\n",
143                                         elem->hook, hook);
144                                 continue;
145                         }
146 #endif
147                         if (verdict != NF_REPEAT)
148                                 return verdict;
149                         *i = (*i)->prev;
150                 }
151         }
152         return NF_ACCEPT;
153 }
154 
155 
156 /* Returns 1 if okfn() needs to be executed by the caller,
157  * -EPERM for NF_DROP, 0 otherwise. */
158 int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
159                  struct net_device *indev,
160                  struct net_device *outdev,
161                  int (*okfn)(struct sk_buff *),
162                  int hook_thresh)
163 {
164         struct list_head *elem;
165         unsigned int verdict;
166         int ret = 0;
167 
168         /* We may already have this, but read-locks nest anyway */
169         rcu_read_lock();
170 
171         elem = &nf_hooks[pf][hook];
172 next_hook:
173         verdict = nf_iterate(&nf_hooks[pf][hook], skb, hook, indev,
174                              outdev, &elem, okfn, hook_thresh);
175         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
176                 ret = 1;
177         } else if (verdict == NF_DROP) {
178                 kfree_skb(skb);
179                 ret = -EPERM;
180         } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
181                 if (!nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
182                               verdict >> NF_VERDICT_BITS))
183                         goto next_hook;
184         }
185         rcu_read_unlock();
186         return ret;
187 }
188 EXPORT_SYMBOL(nf_hook_slow);
189 
190 
191 int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
192 {
193         if (writable_len > skb->len)
194                 return 0;
195 
196         /* Not exclusive use of packet?  Must copy. */
197         if (!skb_cloned(skb)) {
198                 if (writable_len <= skb_headlen(skb))
199                         return 1;
200         } else if (skb_clone_writable(skb, writable_len))
201                 return 1;
202 
203         if (writable_len <= skb_headlen(skb))
204                 writable_len = 0;
205         else
206                 writable_len -= skb_headlen(skb);
207 
208         return !!__pskb_pull_tail(skb, writable_len);
209 }
210 EXPORT_SYMBOL(skb_make_writable);
211 
212 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
213 /* This does not belong here, but locally generated errors need it if connection
214    tracking in use: without this, connection may not be in hash table, and hence
215    manufactured ICMP or RST packets will not be associated with it. */
216 void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *);
217 EXPORT_SYMBOL(ip_ct_attach);
218 
219 void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
220 {
221         void (*attach)(struct sk_buff *, struct sk_buff *);
222 
223         if (skb->nfct) {
224                 rcu_read_lock();
225                 attach = rcu_dereference(ip_ct_attach);
226                 if (attach)
227                         attach(new, skb);
228                 rcu_read_unlock();
229         }
230 }
231 EXPORT_SYMBOL(nf_ct_attach);
232 
233 void (*nf_ct_destroy)(struct nf_conntrack *);
234 EXPORT_SYMBOL(nf_ct_destroy);
235 
236 void nf_conntrack_destroy(struct nf_conntrack *nfct)
237 {
238         void (*destroy)(struct nf_conntrack *);
239 
240         rcu_read_lock();
241         destroy = rcu_dereference(nf_ct_destroy);
242         BUG_ON(destroy == NULL);
243         destroy(nfct);
244         rcu_read_unlock();
245 }
246 EXPORT_SYMBOL(nf_conntrack_destroy);
247 #endif /* CONFIG_NF_CONNTRACK */
248 
249 #ifdef CONFIG_PROC_FS
250 struct proc_dir_entry *proc_net_netfilter;
251 EXPORT_SYMBOL(proc_net_netfilter);
252 #endif
253 
254 void __init netfilter_init(void)
255 {
256         int i, h;
257         for (i = 0; i < ARRAY_SIZE(nf_hooks); i++) {
258                 for (h = 0; h < NF_MAX_HOOKS; h++)
259                         INIT_LIST_HEAD(&nf_hooks[i][h]);
260         }
261 
262 #ifdef CONFIG_PROC_FS
263         proc_net_netfilter = proc_mkdir("netfilter", init_net.proc_net);
264         if (!proc_net_netfilter)
265                 panic("cannot create netfilter proc entry");
266 #endif
267 
268         if (netfilter_queue_init() < 0)
269                 panic("cannot initialize nf_queue");
270         if (netfilter_log_init() < 0)
271                 panic("cannot initialize nf_log");
272 }
273 
274 #ifdef CONFIG_SYSCTL
275 struct ctl_path nf_net_netfilter_sysctl_path[] = {
276         { .procname = "net", .ctl_name = CTL_NET, },
277         { .procname = "netfilter", .ctl_name = NET_NETFILTER, },
278         { }
279 };
280 EXPORT_SYMBOL_GPL(nf_net_netfilter_sysctl_path);
281 #endif /* CONFIG_SYSCTL */
282 

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