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1 | /* | |
2 | * net/sched/ematch.c Extended Match API | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation; either version | |
7 | * 2 of the License, or (at your option) any later version. | |
8 | * | |
9 | * Authors: Thomas Graf <tgraf@suug.ch> | |
10 | * | |
11 | * ========================================================================== | |
12 | * | |
13 | * An extended match (ematch) is a small classification tool not worth | |
14 | * writing a full classifier for. Ematches can be interconnected to form | |
15 | * a logic expression and get attached to classifiers to extend their | |
16 | * functionatlity. | |
17 | * | |
18 | * The userspace part transforms the logic expressions into an array | |
19 | * consisting of multiple sequences of interconnected ematches separated | |
20 | * by markers. Precedence is implemented by a special ematch kind | |
21 | * referencing a sequence beyond the marker of the current sequence | |
22 | * causing the current position in the sequence to be pushed onto a stack | |
23 | * to allow the current position to be overwritten by the position referenced | |
24 | * in the special ematch. Matching continues in the new sequence until a | |
25 | * marker is reached causing the position to be restored from the stack. | |
26 | * | |
27 | * Example: | |
28 | * A AND (B1 OR B2) AND C AND D | |
29 | * | |
30 | * ------->-PUSH------- | |
31 | * -->-- / -->-- \ -->-- | |
32 | * / \ / / \ \ / \ | |
33 | * +-------+-------+-------+-------+-------+--------+ | |
34 | * | A AND | B AND | C AND | D END | B1 OR | B2 END | | |
35 | * +-------+-------+-------+-------+-------+--------+ | |
36 | * \ / | |
37 | * --------<-POP--------- | |
38 | * | |
39 | * where B is a virtual ematch referencing to sequence starting with B1. | |
40 | * | |
41 | * ========================================================================== | |
42 | * | |
43 | * How to write an ematch in 60 seconds | |
44 | * ------------------------------------ | |
45 | * | |
46 | * 1) Provide a matcher function: | |
47 | * static int my_match(struct sk_buff *skb, struct tcf_ematch *m, | |
48 | * struct tcf_pkt_info *info) | |
49 | * { | |
50 | * struct mydata *d = (struct mydata *) m->data; | |
51 | * | |
52 | * if (...matching goes here...) | |
53 | * return 1; | |
54 | * else | |
55 | * return 0; | |
56 | * } | |
57 | * | |
58 | * 2) Fill out a struct tcf_ematch_ops: | |
59 | * static struct tcf_ematch_ops my_ops = { | |
60 | * .kind = unique id, | |
61 | * .datalen = sizeof(struct mydata), | |
62 | * .match = my_match, | |
63 | * .owner = THIS_MODULE, | |
64 | * }; | |
65 | * | |
66 | * 3) Register/Unregister your ematch: | |
67 | * static int __init init_my_ematch(void) | |
68 | * { | |
69 | * return tcf_em_register(&my_ops); | |
70 | * } | |
71 | * | |
72 | * static void __exit exit_my_ematch(void) | |
73 | * { | |
74 | * tcf_em_unregister(&my_ops); | |
75 | * } | |
76 | * | |
77 | * module_init(init_my_ematch); | |
78 | * module_exit(exit_my_ematch); | |
79 | * | |
80 | * 4) By now you should have two more seconds left, barely enough to | |
81 | * open up a beer to watch the compilation going. | |
82 | */ | |
83 | ||
84 | #include <linux/module.h> | |
85 | #include <linux/slab.h> | |
86 | #include <linux/types.h> | |
87 | #include <linux/kernel.h> | |
88 | #include <linux/errno.h> | |
89 | #include <linux/rtnetlink.h> | |
90 | #include <linux/skbuff.h> | |
91 | #include <net/pkt_cls.h> | |
92 | ||
93 | static LIST_HEAD(ematch_ops); | |
94 | static DEFINE_RWLOCK(ematch_mod_lock); | |
95 | ||
96 | static struct tcf_ematch_ops *tcf_em_lookup(u16 kind) | |
97 | { | |
98 | struct tcf_ematch_ops *e = NULL; | |
99 | ||
100 | read_lock(&ematch_mod_lock); | |
101 | list_for_each_entry(e, &ematch_ops, link) { | |
102 | if (kind == e->kind) { | |
103 | if (!try_module_get(e->owner)) | |
104 | e = NULL; | |
105 | read_unlock(&ematch_mod_lock); | |
106 | return e; | |
107 | } | |
108 | } | |
109 | read_unlock(&ematch_mod_lock); | |
110 | ||
111 | return NULL; | |
112 | } | |
113 | ||
114 | /** | |
115 | * tcf_em_register - register an extended match | |
116 | * | |
117 | * @ops: ematch operations lookup table | |
118 | * | |
119 | * This function must be called by ematches to announce their presence. | |
120 | * The given @ops must have kind set to a unique identifier and the | |
121 | * callback match() must be implemented. All other callbacks are optional | |
122 | * and a fallback implementation is used instead. | |
123 | * | |
124 | * Returns -EEXISTS if an ematch of the same kind has already registered. | |
125 | */ | |
126 | int tcf_em_register(struct tcf_ematch_ops *ops) | |
127 | { | |
128 | int err = -EEXIST; | |
129 | struct tcf_ematch_ops *e; | |
130 | ||
131 | if (ops->match == NULL) | |
132 | return -EINVAL; | |
133 | ||
134 | write_lock(&ematch_mod_lock); | |
135 | list_for_each_entry(e, &ematch_ops, link) | |
136 | if (ops->kind == e->kind) | |
137 | goto errout; | |
138 | ||
139 | list_add_tail(&ops->link, &ematch_ops); | |
140 | err = 0; | |
141 | errout: | |
142 | write_unlock(&ematch_mod_lock); | |
143 | return err; | |
144 | } | |
145 | EXPORT_SYMBOL(tcf_em_register); | |
146 | ||
147 | /** | |
148 | * tcf_em_unregister - unregster and extended match | |
149 | * | |
150 | * @ops: ematch operations lookup table | |
151 | * | |
152 | * This function must be called by ematches to announce their disappearance | |
153 | * for examples when the module gets unloaded. The @ops parameter must be | |
154 | * the same as the one used for registration. | |
155 | * | |
156 | * Returns -ENOENT if no matching ematch was found. | |
157 | */ | |
158 | void tcf_em_unregister(struct tcf_ematch_ops *ops) | |
159 | { | |
160 | write_lock(&ematch_mod_lock); | |
161 | list_del(&ops->link); | |
162 | write_unlock(&ematch_mod_lock); | |
163 | } | |
164 | EXPORT_SYMBOL(tcf_em_unregister); | |
165 | ||
166 | static inline struct tcf_ematch *tcf_em_get_match(struct tcf_ematch_tree *tree, | |
167 | int index) | |
168 | { | |
169 | return &tree->matches[index]; | |
170 | } | |
171 | ||
172 | ||
173 | static int tcf_em_validate(struct tcf_proto *tp, | |
174 | struct tcf_ematch_tree_hdr *tree_hdr, | |
175 | struct tcf_ematch *em, struct nlattr *nla, int idx) | |
176 | { | |
177 | int err = -EINVAL; | |
178 | struct tcf_ematch_hdr *em_hdr = nla_data(nla); | |
179 | int data_len = nla_len(nla) - sizeof(*em_hdr); | |
180 | void *data = (void *) em_hdr + sizeof(*em_hdr); | |
181 | struct net *net = dev_net(qdisc_dev(tp->q)); | |
182 | ||
183 | if (!TCF_EM_REL_VALID(em_hdr->flags)) | |
184 | goto errout; | |
185 | ||
186 | if (em_hdr->kind == TCF_EM_CONTAINER) { | |
187 | /* Special ematch called "container", carries an index | |
188 | * referencing an external ematch sequence. | |
189 | */ | |
190 | u32 ref; | |
191 | ||
192 | if (data_len < sizeof(ref)) | |
193 | goto errout; | |
194 | ref = *(u32 *) data; | |
195 | ||
196 | if (ref >= tree_hdr->nmatches) | |
197 | goto errout; | |
198 | ||
199 | /* We do not allow backward jumps to avoid loops and jumps | |
200 | * to our own position are of course illegal. | |
201 | */ | |
202 | if (ref <= idx) | |
203 | goto errout; | |
204 | ||
205 | ||
206 | em->data = ref; | |
207 | } else { | |
208 | /* Note: This lookup will increase the module refcnt | |
209 | * of the ematch module referenced. In case of a failure, | |
210 | * a destroy function is called by the underlying layer | |
211 | * which automatically releases the reference again, therefore | |
212 | * the module MUST not be given back under any circumstances | |
213 | * here. Be aware, the destroy function assumes that the | |
214 | * module is held if the ops field is non zero. | |
215 | */ | |
216 | em->ops = tcf_em_lookup(em_hdr->kind); | |
217 | ||
218 | if (em->ops == NULL) { | |
219 | err = -ENOENT; | |
220 | #ifdef CONFIG_MODULES | |
221 | __rtnl_unlock(); | |
222 | request_module("ematch-kind-%u", em_hdr->kind); | |
223 | rtnl_lock(); | |
224 | em->ops = tcf_em_lookup(em_hdr->kind); | |
225 | if (em->ops) { | |
226 | /* We dropped the RTNL mutex in order to | |
227 | * perform the module load. Tell the caller | |
228 | * to replay the request. | |
229 | */ | |
230 | module_put(em->ops->owner); | |
231 | em->ops = NULL; | |
232 | err = -EAGAIN; | |
233 | } | |
234 | #endif | |
235 | goto errout; | |
236 | } | |
237 | ||
238 | /* ematch module provides expected length of data, so we | |
239 | * can do a basic sanity check. | |
240 | */ | |
241 | if (em->ops->datalen && data_len < em->ops->datalen) | |
242 | goto errout; | |
243 | ||
244 | if (em->ops->change) { | |
245 | err = em->ops->change(net, data, data_len, em); | |
246 | if (err < 0) | |
247 | goto errout; | |
248 | } else if (data_len > 0) { | |
249 | /* ematch module doesn't provide an own change | |
250 | * procedure and expects us to allocate and copy | |
251 | * the ematch data. | |
252 | * | |
253 | * TCF_EM_SIMPLE may be specified stating that the | |
254 | * data only consists of a u32 integer and the module | |
255 | * does not expected a memory reference but rather | |
256 | * the value carried. | |
257 | */ | |
258 | if (em_hdr->flags & TCF_EM_SIMPLE) { | |
259 | if (data_len < sizeof(u32)) | |
260 | goto errout; | |
261 | em->data = *(u32 *) data; | |
262 | } else { | |
263 | void *v = kmemdup(data, data_len, GFP_KERNEL); | |
264 | if (v == NULL) { | |
265 | err = -ENOBUFS; | |
266 | goto errout; | |
267 | } | |
268 | em->data = (unsigned long) v; | |
269 | } | |
270 | } | |
271 | } | |
272 | ||
273 | em->matchid = em_hdr->matchid; | |
274 | em->flags = em_hdr->flags; | |
275 | em->datalen = data_len; | |
276 | em->net = net; | |
277 | ||
278 | err = 0; | |
279 | errout: | |
280 | return err; | |
281 | } | |
282 | ||
283 | static const struct nla_policy em_policy[TCA_EMATCH_TREE_MAX + 1] = { | |
284 | [TCA_EMATCH_TREE_HDR] = { .len = sizeof(struct tcf_ematch_tree_hdr) }, | |
285 | [TCA_EMATCH_TREE_LIST] = { .type = NLA_NESTED }, | |
286 | }; | |
287 | ||
288 | /** | |
289 | * tcf_em_tree_validate - validate ematch config TLV and build ematch tree | |
290 | * | |
291 | * @tp: classifier kind handle | |
292 | * @nla: ematch tree configuration TLV | |
293 | * @tree: destination ematch tree variable to store the resulting | |
294 | * ematch tree. | |
295 | * | |
296 | * This function validates the given configuration TLV @nla and builds an | |
297 | * ematch tree in @tree. The resulting tree must later be copied into | |
298 | * the private classifier data using tcf_em_tree_change(). You MUST NOT | |
299 | * provide the ematch tree variable of the private classifier data directly, | |
300 | * the changes would not be locked properly. | |
301 | * | |
302 | * Returns a negative error code if the configuration TLV contains errors. | |
303 | */ | |
304 | int tcf_em_tree_validate(struct tcf_proto *tp, struct nlattr *nla, | |
305 | struct tcf_ematch_tree *tree) | |
306 | { | |
307 | int idx, list_len, matches_len, err; | |
308 | struct nlattr *tb[TCA_EMATCH_TREE_MAX + 1]; | |
309 | struct nlattr *rt_match, *rt_hdr, *rt_list; | |
310 | struct tcf_ematch_tree_hdr *tree_hdr; | |
311 | struct tcf_ematch *em; | |
312 | ||
313 | memset(tree, 0, sizeof(*tree)); | |
314 | if (!nla) | |
315 | return 0; | |
316 | ||
317 | err = nla_parse_nested(tb, TCA_EMATCH_TREE_MAX, nla, em_policy); | |
318 | if (err < 0) | |
319 | goto errout; | |
320 | ||
321 | err = -EINVAL; | |
322 | rt_hdr = tb[TCA_EMATCH_TREE_HDR]; | |
323 | rt_list = tb[TCA_EMATCH_TREE_LIST]; | |
324 | ||
325 | if (rt_hdr == NULL || rt_list == NULL) | |
326 | goto errout; | |
327 | ||
328 | tree_hdr = nla_data(rt_hdr); | |
329 | memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); | |
330 | ||
331 | rt_match = nla_data(rt_list); | |
332 | list_len = nla_len(rt_list); | |
333 | matches_len = tree_hdr->nmatches * sizeof(*em); | |
334 | ||
335 | tree->matches = kzalloc(matches_len, GFP_KERNEL); | |
336 | if (tree->matches == NULL) | |
337 | goto errout; | |
338 | ||
339 | /* We do not use nla_parse_nested here because the maximum | |
340 | * number of attributes is unknown. This saves us the allocation | |
341 | * for a tb buffer which would serve no purpose at all. | |
342 | * | |
343 | * The array of rt attributes is parsed in the order as they are | |
344 | * provided, their type must be incremental from 1 to n. Even | |
345 | * if it does not serve any real purpose, a failure of sticking | |
346 | * to this policy will result in parsing failure. | |
347 | */ | |
348 | for (idx = 0; nla_ok(rt_match, list_len); idx++) { | |
349 | err = -EINVAL; | |
350 | ||
351 | if (rt_match->nla_type != (idx + 1)) | |
352 | goto errout_abort; | |
353 | ||
354 | if (idx >= tree_hdr->nmatches) | |
355 | goto errout_abort; | |
356 | ||
357 | if (nla_len(rt_match) < sizeof(struct tcf_ematch_hdr)) | |
358 | goto errout_abort; | |
359 | ||
360 | em = tcf_em_get_match(tree, idx); | |
361 | ||
362 | err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx); | |
363 | if (err < 0) | |
364 | goto errout_abort; | |
365 | ||
366 | rt_match = nla_next(rt_match, &list_len); | |
367 | } | |
368 | ||
369 | /* Check if the number of matches provided by userspace actually | |
370 | * complies with the array of matches. The number was used for | |
371 | * the validation of references and a mismatch could lead to | |
372 | * undefined references during the matching process. | |
373 | */ | |
374 | if (idx != tree_hdr->nmatches) { | |
375 | err = -EINVAL; | |
376 | goto errout_abort; | |
377 | } | |
378 | ||
379 | err = 0; | |
380 | errout: | |
381 | return err; | |
382 | ||
383 | errout_abort: | |
384 | tcf_em_tree_destroy(tree); | |
385 | return err; | |
386 | } | |
387 | EXPORT_SYMBOL(tcf_em_tree_validate); | |
388 | ||
389 | /** | |
390 | * tcf_em_tree_destroy - destroy an ematch tree | |
391 | * | |
392 | * @tp: classifier kind handle | |
393 | * @tree: ematch tree to be deleted | |
394 | * | |
395 | * This functions destroys an ematch tree previously created by | |
396 | * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that | |
397 | * the ematch tree is not in use before calling this function. | |
398 | */ | |
399 | void tcf_em_tree_destroy(struct tcf_ematch_tree *tree) | |
400 | { | |
401 | int i; | |
402 | ||
403 | if (tree->matches == NULL) | |
404 | return; | |
405 | ||
406 | for (i = 0; i < tree->hdr.nmatches; i++) { | |
407 | struct tcf_ematch *em = tcf_em_get_match(tree, i); | |
408 | ||
409 | if (em->ops) { | |
410 | if (em->ops->destroy) | |
411 | em->ops->destroy(em); | |
412 | else if (!tcf_em_is_simple(em)) | |
413 | kfree((void *) em->data); | |
414 | module_put(em->ops->owner); | |
415 | } | |
416 | } | |
417 | ||
418 | tree->hdr.nmatches = 0; | |
419 | kfree(tree->matches); | |
420 | tree->matches = NULL; | |
421 | } | |
422 | EXPORT_SYMBOL(tcf_em_tree_destroy); | |
423 | ||
424 | /** | |
425 | * tcf_em_tree_dump - dump ematch tree into a rtnl message | |
426 | * | |
427 | * @skb: skb holding the rtnl message | |
428 | * @t: ematch tree to be dumped | |
429 | * @tlv: TLV type to be used to encapsulate the tree | |
430 | * | |
431 | * This function dumps a ematch tree into a rtnl message. It is valid to | |
432 | * call this function while the ematch tree is in use. | |
433 | * | |
434 | * Returns -1 if the skb tailroom is insufficient. | |
435 | */ | |
436 | int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) | |
437 | { | |
438 | int i; | |
439 | u8 *tail; | |
440 | struct nlattr *top_start; | |
441 | struct nlattr *list_start; | |
442 | ||
443 | top_start = nla_nest_start(skb, tlv); | |
444 | if (top_start == NULL) | |
445 | goto nla_put_failure; | |
446 | ||
447 | if (nla_put(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr)) | |
448 | goto nla_put_failure; | |
449 | ||
450 | list_start = nla_nest_start(skb, TCA_EMATCH_TREE_LIST); | |
451 | if (list_start == NULL) | |
452 | goto nla_put_failure; | |
453 | ||
454 | tail = skb_tail_pointer(skb); | |
455 | for (i = 0; i < tree->hdr.nmatches; i++) { | |
456 | struct nlattr *match_start = (struct nlattr *)tail; | |
457 | struct tcf_ematch *em = tcf_em_get_match(tree, i); | |
458 | struct tcf_ematch_hdr em_hdr = { | |
459 | .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, | |
460 | .matchid = em->matchid, | |
461 | .flags = em->flags | |
462 | }; | |
463 | ||
464 | if (nla_put(skb, i + 1, sizeof(em_hdr), &em_hdr)) | |
465 | goto nla_put_failure; | |
466 | ||
467 | if (em->ops && em->ops->dump) { | |
468 | if (em->ops->dump(skb, em) < 0) | |
469 | goto nla_put_failure; | |
470 | } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { | |
471 | u32 u = em->data; | |
472 | nla_put_nohdr(skb, sizeof(u), &u); | |
473 | } else if (em->datalen > 0) | |
474 | nla_put_nohdr(skb, em->datalen, (void *) em->data); | |
475 | ||
476 | tail = skb_tail_pointer(skb); | |
477 | match_start->nla_len = tail - (u8 *)match_start; | |
478 | } | |
479 | ||
480 | nla_nest_end(skb, list_start); | |
481 | nla_nest_end(skb, top_start); | |
482 | ||
483 | return 0; | |
484 | ||
485 | nla_put_failure: | |
486 | return -1; | |
487 | } | |
488 | EXPORT_SYMBOL(tcf_em_tree_dump); | |
489 | ||
490 | static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, | |
491 | struct tcf_pkt_info *info) | |
492 | { | |
493 | int r = em->ops->match(skb, em, info); | |
494 | ||
495 | return tcf_em_is_inverted(em) ? !r : r; | |
496 | } | |
497 | ||
498 | /* Do not use this function directly, use tcf_em_tree_match instead */ | |
499 | int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, | |
500 | struct tcf_pkt_info *info) | |
501 | { | |
502 | int stackp = 0, match_idx = 0, res = 0; | |
503 | struct tcf_ematch *cur_match; | |
504 | int stack[CONFIG_NET_EMATCH_STACK]; | |
505 | ||
506 | proceed: | |
507 | while (match_idx < tree->hdr.nmatches) { | |
508 | cur_match = tcf_em_get_match(tree, match_idx); | |
509 | ||
510 | if (tcf_em_is_container(cur_match)) { | |
511 | if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) | |
512 | goto stack_overflow; | |
513 | ||
514 | stack[stackp++] = match_idx; | |
515 | match_idx = cur_match->data; | |
516 | goto proceed; | |
517 | } | |
518 | ||
519 | res = tcf_em_match(skb, cur_match, info); | |
520 | ||
521 | if (tcf_em_early_end(cur_match, res)) | |
522 | break; | |
523 | ||
524 | match_idx++; | |
525 | } | |
526 | ||
527 | pop_stack: | |
528 | if (stackp > 0) { | |
529 | match_idx = stack[--stackp]; | |
530 | cur_match = tcf_em_get_match(tree, match_idx); | |
531 | ||
532 | if (tcf_em_is_inverted(cur_match)) | |
533 | res = !res; | |
534 | ||
535 | if (tcf_em_early_end(cur_match, res)) { | |
536 | goto pop_stack; | |
537 | } else { | |
538 | match_idx++; | |
539 | goto proceed; | |
540 | } | |
541 | } | |
542 | ||
543 | return res; | |
544 | ||
545 | stack_overflow: | |
546 | net_warn_ratelimited("tc ematch: local stack overflow, increase NET_EMATCH_STACK\n"); | |
547 | return -1; | |
548 | } | |
549 | EXPORT_SYMBOL(__tcf_em_tree_match); |