xref: /linux/net/netfilter/nf_queue.c (revision 0be3ff0c) 
1 /*
2  * Rusty Russell (C)2000 -- This code is GPL.
3  * Patrick McHardy (c) 2006-2012
4  */
5 
6 #include <linux/kernel.h>
7 #include <linux/slab.h>
8 #include <linux/init.h>
9 #include <linux/module.h>
10 #include <linux/proc_fs.h>
11 #include <linux/skbuff.h>
12 #include <linux/netfilter.h>
13 #include <linux/netfilter_ipv4.h>
14 #include <linux/netfilter_ipv6.h>
15 #include <linux/netfilter_bridge.h>
16 #include <linux/seq_file.h>
17 #include <linux/rcupdate.h>
18 #include <net/protocol.h>
19 #include <net/netfilter/nf_queue.h>
20 #include <net/dst.h>
21 
22 #include "nf_internals.h"
23 
24 static const struct nf_queue_handler __rcu *nf_queue_handler;
25 
26 /*
27  * Hook for nfnetlink_queue to register its queue handler.
28  * We do this so that most of the NFQUEUE code can be modular.
29  *
30  * Once the queue is registered it must reinject all packets it
31  * receives, no matter what.
32  */
33 
34 void nf_register_queue_handler(const struct nf_queue_handler *qh)
35 {
36 	/* should never happen, we only have one queueing backend in kernel */
37 	WARN_ON(rcu_access_pointer(nf_queue_handler));
38 	rcu_assign_pointer(nf_queue_handler, qh);
39 }
40 EXPORT_SYMBOL(nf_register_queue_handler);
41 
42 /* The caller must flush their queue before this */
43 void nf_unregister_queue_handler(void)
44 {
45 	RCU_INIT_POINTER(nf_queue_handler, NULL);
46 }
47 EXPORT_SYMBOL(nf_unregister_queue_handler);
48 
49 static void nf_queue_sock_put(struct sock *sk)
50 {
51 #ifdef CONFIG_INET
52 	sock_gen_put(sk);
53 #else
54 	sock_put(sk);
55 #endif
56 }
57 
58 static void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
59 {
60 	struct nf_hook_state *state = &entry->state;
61 
62 	/* Release those devices we held, or Alexey will kill me. */
63 	dev_put(state->in);
64 	dev_put(state->out);
65 	if (state->sk)
66 		nf_queue_sock_put(state->sk);
67 
68 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
69 	dev_put(entry->physin);
70 	dev_put(entry->physout);
71 #endif
72 }
73 
74 void nf_queue_entry_free(struct nf_queue_entry *entry)
75 {
76 	nf_queue_entry_release_refs(entry);
77 	kfree(entry);
78 }
79 EXPORT_SYMBOL_GPL(nf_queue_entry_free);
80 
81 static void __nf_queue_entry_init_physdevs(struct nf_queue_entry *entry)
82 {
83 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
84 	const struct sk_buff *skb = entry->skb;
85 	struct nf_bridge_info *nf_bridge;
86 
87 	nf_bridge = nf_bridge_info_get(skb);
88 	if (nf_bridge) {
89 		entry->physin = nf_bridge_get_physindev(skb);
90 		entry->physout = nf_bridge_get_physoutdev(skb);
91 	} else {
92 		entry->physin = NULL;
93 		entry->physout = NULL;
94 	}
95 #endif
96 }
97 
98 /* Bump dev refs so they don't vanish while packet is out */
99 bool nf_queue_entry_get_refs(struct nf_queue_entry *entry)
100 {
101 	struct nf_hook_state *state = &entry->state;
102 
103 	if (state->sk && !refcount_inc_not_zero(&state->sk->sk_refcnt))
104 		return false;
105 
106 	dev_hold(state->in);
107 	dev_hold(state->out);
108 
109 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
110 	dev_hold(entry->physin);
111 	dev_hold(entry->physout);
112 #endif
113 	return true;
114 }
115 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
116 
117 void nf_queue_nf_hook_drop(struct net *net)
118 {
119 	const struct nf_queue_handler *qh;
120 
121 	rcu_read_lock();
122 	qh = rcu_dereference(nf_queue_handler);
123 	if (qh)
124 		qh->nf_hook_drop(net);
125 	rcu_read_unlock();
126 }
127 EXPORT_SYMBOL_GPL(nf_queue_nf_hook_drop);
128 
129 static void nf_ip_saveroute(const struct sk_buff *skb,
130 			    struct nf_queue_entry *entry)
131 {
132 	struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
133 
134 	if (entry->state.hook == NF_INET_LOCAL_OUT) {
135 		const struct iphdr *iph = ip_hdr(skb);
136 
137 		rt_info->tos = iph->tos;
138 		rt_info->daddr = iph->daddr;
139 		rt_info->saddr = iph->saddr;
140 		rt_info->mark = skb->mark;
141 	}
142 }
143 
144 static void nf_ip6_saveroute(const struct sk_buff *skb,
145 			     struct nf_queue_entry *entry)
146 {
147 	struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
148 
149 	if (entry->state.hook == NF_INET_LOCAL_OUT) {
150 		const struct ipv6hdr *iph = ipv6_hdr(skb);
151 
152 		rt_info->daddr = iph->daddr;
153 		rt_info->saddr = iph->saddr;
154 		rt_info->mark = skb->mark;
155 	}
156 }
157 
158 static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
159 		      unsigned int index, unsigned int queuenum)
160 {
161 	struct nf_queue_entry *entry = NULL;
162 	const struct nf_queue_handler *qh;
163 	unsigned int route_key_size;
164 	int status;
165 
166 	/* QUEUE == DROP if no one is waiting, to be safe. */
167 	qh = rcu_dereference(nf_queue_handler);
168 	if (!qh)
169 		return -ESRCH;
170 
171 	switch (state->pf) {
172 	case AF_INET:
173 		route_key_size = sizeof(struct ip_rt_info);
174 		break;
175 	case AF_INET6:
176 		route_key_size = sizeof(struct ip6_rt_info);
177 		break;
178 	default:
179 		route_key_size = 0;
180 		break;
181 	}
182 
183 	if (skb_sk_is_prefetched(skb)) {
184 		struct sock *sk = skb->sk;
185 
186 		if (!sk_is_refcounted(sk)) {
187 			if (!refcount_inc_not_zero(&sk->sk_refcnt))
188 				return -ENOTCONN;
189 
190 			/* drop refcount on skb_orphan */
191 			skb->destructor = sock_edemux;
192 		}
193 	}
194 
195 	entry = kmalloc(sizeof(*entry) + route_key_size, GFP_ATOMIC);
196 	if (!entry)
197 		return -ENOMEM;
198 
199 	if (skb_dst(skb) && !skb_dst_force(skb)) {
200 		kfree(entry);
201 		return -ENETDOWN;
202 	}
203 
204 	*entry = (struct nf_queue_entry) {
205 		.skb	= skb,
206 		.state	= *state,
207 		.hook_index = index,
208 		.size	= sizeof(*entry) + route_key_size,
209 	};
210 
211 	__nf_queue_entry_init_physdevs(entry);
212 
213 	if (!nf_queue_entry_get_refs(entry)) {
214 		kfree(entry);
215 		return -ENOTCONN;
216 	}
217 
218 	switch (entry->state.pf) {
219 	case AF_INET:
220 		nf_ip_saveroute(skb, entry);
221 		break;
222 	case AF_INET6:
223 		nf_ip6_saveroute(skb, entry);
224 		break;
225 	}
226 
227 	status = qh->outfn(entry, queuenum);
228 	if (status < 0) {
229 		nf_queue_entry_free(entry);
230 		return status;
231 	}
232 
233 	return 0;
234 }
235 
236 /* Packets leaving via this function must come back through nf_reinject(). */
237 int nf_queue(struct sk_buff *skb, struct nf_hook_state *state,
238 	     unsigned int index, unsigned int verdict)
239 {
240 	int ret;
241 
242 	ret = __nf_queue(skb, state, index, verdict >> NF_VERDICT_QBITS);
243 	if (ret < 0) {
244 		if (ret == -ESRCH &&
245 		    (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
246 			return 1;
247 		kfree_skb(skb);
248 	}
249 
250 	return 0;
251 }
252 EXPORT_SYMBOL_GPL(nf_queue);
253 
254 static unsigned int nf_iterate(struct sk_buff *skb,
255 			       struct nf_hook_state *state,
256 			       const struct nf_hook_entries *hooks,
257 			       unsigned int *index)
258 {
259 	const struct nf_hook_entry *hook;
260 	unsigned int verdict, i = *index;
261 
262 	while (i < hooks->num_hook_entries) {
263 		hook = &hooks->hooks[i];
264 repeat:
265 		verdict = nf_hook_entry_hookfn(hook, skb, state);
266 		if (verdict != NF_ACCEPT) {
267 			*index = i;
268 			if (verdict != NF_REPEAT)
269 				return verdict;
270 			goto repeat;
271 		}
272 		i++;
273 	}
274 
275 	*index = i;
276 	return NF_ACCEPT;
277 }
278 
279 static struct nf_hook_entries *nf_hook_entries_head(const struct net *net, u8 pf, u8 hooknum)
280 {
281 	switch (pf) {
282 #ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
283 	case NFPROTO_BRIDGE:
284 		return rcu_dereference(net->nf.hooks_bridge[hooknum]);
285 #endif
286 	case NFPROTO_IPV4:
287 		return rcu_dereference(net->nf.hooks_ipv4[hooknum]);
288 	case NFPROTO_IPV6:
289 		return rcu_dereference(net->nf.hooks_ipv6[hooknum]);
290 	default:
291 		WARN_ON_ONCE(1);
292 		return NULL;
293 	}
294 
295 	return NULL;
296 }
297 
298 /* Caller must hold rcu read-side lock */
299 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
300 {
301 	const struct nf_hook_entry *hook_entry;
302 	const struct nf_hook_entries *hooks;
303 	struct sk_buff *skb = entry->skb;
304 	const struct net *net;
305 	unsigned int i;
306 	int err;
307 	u8 pf;
308 
309 	net = entry->state.net;
310 	pf = entry->state.pf;
311 
312 	hooks = nf_hook_entries_head(net, pf, entry->state.hook);
313 
314 	i = entry->hook_index;
315 	if (WARN_ON_ONCE(!hooks || i >= hooks->num_hook_entries)) {
316 		kfree_skb(skb);
317 		nf_queue_entry_free(entry);
318 		return;
319 	}
320 
321 	hook_entry = &hooks->hooks[i];
322 
323 	/* Continue traversal iff userspace said ok... */
324 	if (verdict == NF_REPEAT)
325 		verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state);
326 
327 	if (verdict == NF_ACCEPT) {
328 		if (nf_reroute(skb, entry) < 0)
329 			verdict = NF_DROP;
330 	}
331 
332 	if (verdict == NF_ACCEPT) {
333 next_hook:
334 		++i;
335 		verdict = nf_iterate(skb, &entry->state, hooks, &i);
336 	}
337 
338 	switch (verdict & NF_VERDICT_MASK) {
339 	case NF_ACCEPT:
340 	case NF_STOP:
341 		local_bh_disable();
342 		entry->state.okfn(entry->state.net, entry->state.sk, skb);
343 		local_bh_enable();
344 		break;
345 	case NF_QUEUE:
346 		err = nf_queue(skb, &entry->state, i, verdict);
347 		if (err == 1)
348 			goto next_hook;
349 		break;
350 	case NF_STOLEN:
351 		break;
352 	default:
353 		kfree_skb(skb);
354 	}
355 
356 	nf_queue_entry_free(entry);
357 }
358 EXPORT_SYMBOL(nf_reinject);
359