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nf_queue.c
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1 #include <linux/kernel.h>
2 #include <linux/slab.h>
3 #include <linux/init.h>
4 #include <linux/module.h>
5 #include <linux/proc_fs.h>
6 #include <linux/skbuff.h>
7 #include <linux/netfilter.h>
8 #include <linux/seq_file.h>
9 #include <linux/rcupdate.h>
10 #include <net/protocol.h>
11 #include <net/netfilter/nf_queue.h>
12 #include <net/dst.h>
13 
14 #include "nf_internals.h"
15 
16 /*
17  * A queue handler may be registered for each protocol. Each is protected by
18  * long term mutex. The handler must provide an an outfn() to accept packets
19  * for queueing and must reinject all packets it receives, no matter what.
20  */
21 static const struct nf_queue_handler __rcu *queue_handler[NFPROTO_NUMPROTO] __read_mostly;
22 
23 static DEFINE_MUTEX(queue_handler_mutex);
24 
25 /* return EBUSY when somebody else is registered, return EEXIST if the
26  * same handler is registered, return 0 in case of success. */
28 {
29  int ret;
30  const struct nf_queue_handler *old;
31 
32  if (pf >= ARRAY_SIZE(queue_handler))
33  return -EINVAL;
34 
35  mutex_lock(&queue_handler_mutex);
36  old = rcu_dereference_protected(queue_handler[pf],
37  lockdep_is_held(&queue_handler_mutex));
38  if (old == qh)
39  ret = -EEXIST;
40  else if (old)
41  ret = -EBUSY;
42  else {
43  rcu_assign_pointer(queue_handler[pf], qh);
44  ret = 0;
45  }
46  mutex_unlock(&queue_handler_mutex);
47 
48  return ret;
49 }
51 
52 /* The caller must flush their queue before this */
54 {
55  const struct nf_queue_handler *old;
56 
57  if (pf >= ARRAY_SIZE(queue_handler))
58  return -EINVAL;
59 
60  mutex_lock(&queue_handler_mutex);
61  old = rcu_dereference_protected(queue_handler[pf],
62  lockdep_is_held(&queue_handler_mutex));
63  if (old && old != qh) {
64  mutex_unlock(&queue_handler_mutex);
65  return -EINVAL;
66  }
67 
68  RCU_INIT_POINTER(queue_handler[pf], NULL);
69  mutex_unlock(&queue_handler_mutex);
70 
71  synchronize_rcu();
72 
73  return 0;
74 }
76 
78 {
79  u_int8_t pf;
80 
81  mutex_lock(&queue_handler_mutex);
82  for (pf = 0; pf < ARRAY_SIZE(queue_handler); pf++) {
84  queue_handler[pf],
85  lockdep_is_held(&queue_handler_mutex)
86  ) == qh)
87  RCU_INIT_POINTER(queue_handler[pf], NULL);
88  }
89  mutex_unlock(&queue_handler_mutex);
90 
91  synchronize_rcu();
92 }
94 
95 static void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
96 {
97  /* Release those devices we held, or Alexey will kill me. */
98  if (entry->indev)
99  dev_put(entry->indev);
100  if (entry->outdev)
101  dev_put(entry->outdev);
102 #ifdef CONFIG_BRIDGE_NETFILTER
103  if (entry->skb->nf_bridge) {
104  struct nf_bridge_info *nf_bridge = entry->skb->nf_bridge;
105 
106  if (nf_bridge->physindev)
107  dev_put(nf_bridge->physindev);
108  if (nf_bridge->physoutdev)
109  dev_put(nf_bridge->physoutdev);
110  }
111 #endif
112  /* Drop reference to owner of hook which queued us. */
113  module_put(entry->elem->owner);
114 }
115 
116 /*
117  * Any packet that leaves via this function must come back
118  * through nf_reinject().
119  */
120 static int __nf_queue(struct sk_buff *skb,
121  struct nf_hook_ops *elem,
122  u_int8_t pf, unsigned int hook,
123  struct net_device *indev,
124  struct net_device *outdev,
125  int (*okfn)(struct sk_buff *),
126  unsigned int queuenum)
127 {
128  int status = -ENOENT;
129  struct nf_queue_entry *entry = NULL;
130 #ifdef CONFIG_BRIDGE_NETFILTER
131  struct net_device *physindev;
132  struct net_device *physoutdev;
133 #endif
134  const struct nf_afinfo *afinfo;
135  const struct nf_queue_handler *qh;
136 
137  /* QUEUE == DROP if no one is waiting, to be safe. */
138  rcu_read_lock();
139 
140  qh = rcu_dereference(queue_handler[pf]);
141  if (!qh) {
142  status = -ESRCH;
143  goto err_unlock;
144  }
145 
146  afinfo = nf_get_afinfo(pf);
147  if (!afinfo)
148  goto err_unlock;
149 
150  entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
151  if (!entry) {
152  status = -ENOMEM;
153  goto err_unlock;
154  }
155 
156  *entry = (struct nf_queue_entry) {
157  .skb = skb,
158  .elem = elem,
159  .pf = pf,
160  .hook = hook,
161  .indev = indev,
162  .outdev = outdev,
163  .okfn = okfn,
164  };
165 
166  /* If it's going away, ignore hook. */
167  if (!try_module_get(entry->elem->owner)) {
168  status = -ECANCELED;
169  goto err_unlock;
170  }
171  /* Bump dev refs so they don't vanish while packet is out */
172  if (indev)
173  dev_hold(indev);
174  if (outdev)
175  dev_hold(outdev);
176 #ifdef CONFIG_BRIDGE_NETFILTER
177  if (skb->nf_bridge) {
178  physindev = skb->nf_bridge->physindev;
179  if (physindev)
180  dev_hold(physindev);
181  physoutdev = skb->nf_bridge->physoutdev;
182  if (physoutdev)
183  dev_hold(physoutdev);
184  }
185 #endif
186  skb_dst_force(skb);
187  afinfo->saveroute(skb, entry);
188  status = qh->outfn(entry, queuenum);
189 
190  rcu_read_unlock();
191 
192  if (status < 0) {
193  nf_queue_entry_release_refs(entry);
194  goto err;
195  }
196 
197  return 0;
198 
199 err_unlock:
200  rcu_read_unlock();
201 err:
202  kfree(entry);
203  return status;
204 }
205 
206 #ifdef CONFIG_BRIDGE_NETFILTER
207 /* When called from bridge netfilter, skb->data must point to MAC header
208  * before calling skb_gso_segment(). Else, original MAC header is lost
209  * and segmented skbs will be sent to wrong destination.
210  */
211 static void nf_bridge_adjust_skb_data(struct sk_buff *skb)
212 {
213  if (skb->nf_bridge)
214  __skb_push(skb, skb->network_header - skb->mac_header);
215 }
216 
217 static void nf_bridge_adjust_segmented_data(struct sk_buff *skb)
218 {
219  if (skb->nf_bridge)
220  __skb_pull(skb, skb->network_header - skb->mac_header);
221 }
222 #else
223 #define nf_bridge_adjust_skb_data(s) do {} while (0)
224 #define nf_bridge_adjust_segmented_data(s) do {} while (0)
225 #endif
226 
227 int nf_queue(struct sk_buff *skb,
228  struct nf_hook_ops *elem,
229  u_int8_t pf, unsigned int hook,
230  struct net_device *indev,
231  struct net_device *outdev,
232  int (*okfn)(struct sk_buff *),
233  unsigned int queuenum)
234 {
235  struct sk_buff *segs;
236  int err = -EINVAL;
237  unsigned int queued;
238 
239  if (!skb_is_gso(skb))
240  return __nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
241  queuenum);
242 
243  switch (pf) {
244  case NFPROTO_IPV4:
245  skb->protocol = htons(ETH_P_IP);
246  break;
247  case NFPROTO_IPV6:
248  skb->protocol = htons(ETH_P_IPV6);
249  break;
250  }
251 
253  segs = skb_gso_segment(skb, 0);
254  /* Does not use PTR_ERR to limit the number of error codes that can be
255  * returned by nf_queue. For instance, callers rely on -ECANCELED to mean
256  * 'ignore this hook'.
257  */
258  if (IS_ERR(segs))
259  goto out_err;
260  queued = 0;
261  err = 0;
262  do {
263  struct sk_buff *nskb = segs->next;
264 
265  segs->next = NULL;
266  if (err == 0) {
268  err = __nf_queue(segs, elem, pf, hook, indev,
269  outdev, okfn, queuenum);
270  }
271  if (err == 0)
272  queued++;
273  else
274  kfree_skb(segs);
275  segs = nskb;
276  } while (segs);
277 
278  if (queued) {
279  kfree_skb(skb);
280  return 0;
281  }
282  out_err:
284  return err;
285 }
286 
287 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
288 {
289  struct sk_buff *skb = entry->skb;
290  struct nf_hook_ops *elem = entry->elem;
291  const struct nf_afinfo *afinfo;
292  int err;
293 
294  rcu_read_lock();
295 
296  nf_queue_entry_release_refs(entry);
297 
298  /* Continue traversal iff userspace said ok... */
299  if (verdict == NF_REPEAT) {
300  elem = list_entry(elem->list.prev, struct nf_hook_ops, list);
301  verdict = NF_ACCEPT;
302  }
303 
304  if (verdict == NF_ACCEPT) {
305  afinfo = nf_get_afinfo(entry->pf);
306  if (!afinfo || afinfo->reroute(skb, entry) < 0)
307  verdict = NF_DROP;
308  }
309 
310  if (verdict == NF_ACCEPT) {
311  next_hook:
312  verdict = nf_iterate(&nf_hooks[entry->pf][entry->hook],
313  skb, entry->hook,
314  entry->indev, entry->outdev, &elem,
315  entry->okfn, INT_MIN);
316  }
317 
318  switch (verdict & NF_VERDICT_MASK) {
319  case NF_ACCEPT:
320  case NF_STOP:
322  entry->okfn(skb);
323  local_bh_enable();
324  break;
325  case NF_QUEUE:
326  err = __nf_queue(skb, elem, entry->pf, entry->hook,
327  entry->indev, entry->outdev, entry->okfn,
328  verdict >> NF_VERDICT_QBITS);
329  if (err < 0) {
330  if (err == -ECANCELED)
331  goto next_hook;
332  if (err == -ESRCH &&
333  (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
334  goto next_hook;
335  kfree_skb(skb);
336  }
337  break;
338  case NF_STOLEN:
339  break;
340  default:
341  kfree_skb(skb);
342  }
343  rcu_read_unlock();
344  kfree(entry);
345 }
347 
348 #ifdef CONFIG_PROC_FS
349 static void *seq_start(struct seq_file *seq, loff_t *pos)
350 {
351  if (*pos >= ARRAY_SIZE(queue_handler))
352  return NULL;
353 
354  return pos;
355 }
356 
357 static void *seq_next(struct seq_file *s, void *v, loff_t *pos)
358 {
359  (*pos)++;
360 
361  if (*pos >= ARRAY_SIZE(queue_handler))
362  return NULL;
363 
364  return pos;
365 }
366 
367 static void seq_stop(struct seq_file *s, void *v)
368 {
369 
370 }
371 
372 static int seq_show(struct seq_file *s, void *v)
373 {
374  int ret;
375  loff_t *pos = v;
376  const struct nf_queue_handler *qh;
377 
378  rcu_read_lock();
379  qh = rcu_dereference(queue_handler[*pos]);
380  if (!qh)
381  ret = seq_printf(s, "%2lld NONE\n", *pos);
382  else
383  ret = seq_printf(s, "%2lld %s\n", *pos, qh->name);
384  rcu_read_unlock();
385 
386  return ret;
387 }
388 
389 static const struct seq_operations nfqueue_seq_ops = {
390  .start = seq_start,
391  .next = seq_next,
392  .stop = seq_stop,
393  .show = seq_show,
394 };
395 
396 static int nfqueue_open(struct inode *inode, struct file *file)
397 {
398  return seq_open(file, &nfqueue_seq_ops);
399 }
400 
401 static const struct file_operations nfqueue_file_ops = {
402  .owner = THIS_MODULE,
403  .open = nfqueue_open,
404  .read = seq_read,
405  .llseek = seq_lseek,
406  .release = seq_release,
407 };
408 #endif /* PROC_FS */
409 
410 
412 {
413 #ifdef CONFIG_PROC_FS
414  if (!proc_create("nf_queue", S_IRUGO,
415  proc_net_netfilter, &nfqueue_file_ops))
416  return -1;
417 #endif
418  return 0;
419 }
420