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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 | * 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(®->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(®->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(®[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(®[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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