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1da177e4 LT |
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 | * return 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/config.h> | |
85 | #include <linux/module.h> | |
86 | #include <linux/types.h> | |
87 | #include <linux/kernel.h> | |
88 | #include <linux/sched.h> | |
89 | #include <linux/mm.h> | |
90 | #include <linux/errno.h> | |
91 | #include <linux/interrupt.h> | |
92 | #include <linux/rtnetlink.h> | |
93 | #include <linux/skbuff.h> | |
94 | #include <net/pkt_cls.h> | |
95 | #include <config/net/ematch/stack.h> | |
96 | ||
97 | static LIST_HEAD(ematch_ops); | |
98 | static DEFINE_RWLOCK(ematch_mod_lock); | |
99 | ||
100 | static inline struct tcf_ematch_ops * tcf_em_lookup(u16 kind) | |
101 | { | |
102 | struct tcf_ematch_ops *e = NULL; | |
103 | ||
104 | read_lock(&ematch_mod_lock); | |
105 | list_for_each_entry(e, &ematch_ops, link) { | |
106 | if (kind == e->kind) { | |
107 | if (!try_module_get(e->owner)) | |
108 | e = NULL; | |
109 | read_unlock(&ematch_mod_lock); | |
110 | return e; | |
111 | } | |
112 | } | |
113 | read_unlock(&ematch_mod_lock); | |
114 | ||
115 | return NULL; | |
116 | } | |
117 | ||
118 | /** | |
119 | * tcf_em_register - register an extended match | |
120 | * | |
121 | * @ops: ematch operations lookup table | |
122 | * | |
123 | * This function must be called by ematches to announce their presence. | |
124 | * The given @ops must have kind set to a unique identifier and the | |
125 | * callback match() must be implemented. All other callbacks are optional | |
126 | * and a fallback implementation is used instead. | |
127 | * | |
128 | * Returns -EEXISTS if an ematch of the same kind has already registered. | |
129 | */ | |
130 | int tcf_em_register(struct tcf_ematch_ops *ops) | |
131 | { | |
132 | int err = -EEXIST; | |
133 | struct tcf_ematch_ops *e; | |
134 | ||
135 | if (ops->match == NULL) | |
136 | return -EINVAL; | |
137 | ||
138 | write_lock(&ematch_mod_lock); | |
139 | list_for_each_entry(e, &ematch_ops, link) | |
140 | if (ops->kind == e->kind) | |
141 | goto errout; | |
142 | ||
143 | list_add_tail(&ops->link, &ematch_ops); | |
144 | err = 0; | |
145 | errout: | |
146 | write_unlock(&ematch_mod_lock); | |
147 | return err; | |
148 | } | |
149 | ||
150 | /** | |
151 | * tcf_em_unregister - unregster and extended match | |
152 | * | |
153 | * @ops: ematch operations lookup table | |
154 | * | |
155 | * This function must be called by ematches to announce their disappearance | |
156 | * for examples when the module gets unloaded. The @ops parameter must be | |
157 | * the same as the one used for registration. | |
158 | * | |
159 | * Returns -ENOENT if no matching ematch was found. | |
160 | */ | |
161 | int tcf_em_unregister(struct tcf_ematch_ops *ops) | |
162 | { | |
163 | int err = 0; | |
164 | struct tcf_ematch_ops *e; | |
165 | ||
166 | write_lock(&ematch_mod_lock); | |
167 | list_for_each_entry(e, &ematch_ops, link) { | |
168 | if (e == ops) { | |
169 | list_del(&e->link); | |
170 | goto out; | |
171 | } | |
172 | } | |
173 | ||
174 | err = -ENOENT; | |
175 | out: | |
176 | write_unlock(&ematch_mod_lock); | |
177 | return err; | |
178 | } | |
179 | ||
180 | static inline struct tcf_ematch * tcf_em_get_match(struct tcf_ematch_tree *tree, | |
181 | int index) | |
182 | { | |
183 | return &tree->matches[index]; | |
184 | } | |
185 | ||
186 | ||
187 | static int tcf_em_validate(struct tcf_proto *tp, | |
188 | struct tcf_ematch_tree_hdr *tree_hdr, | |
189 | struct tcf_ematch *em, struct rtattr *rta, int idx) | |
190 | { | |
191 | int err = -EINVAL; | |
192 | struct tcf_ematch_hdr *em_hdr = RTA_DATA(rta); | |
193 | int data_len = RTA_PAYLOAD(rta) - sizeof(*em_hdr); | |
194 | void *data = (void *) em_hdr + sizeof(*em_hdr); | |
195 | ||
196 | if (!TCF_EM_REL_VALID(em_hdr->flags)) | |
197 | goto errout; | |
198 | ||
199 | if (em_hdr->kind == TCF_EM_CONTAINER) { | |
200 | /* Special ematch called "container", carries an index | |
201 | * referencing an external ematch sequence. */ | |
202 | u32 ref; | |
203 | ||
204 | if (data_len < sizeof(ref)) | |
205 | goto errout; | |
206 | ref = *(u32 *) data; | |
207 | ||
208 | if (ref >= tree_hdr->nmatches) | |
209 | goto errout; | |
210 | ||
211 | /* We do not allow backward jumps to avoid loops and jumps | |
212 | * to our own position are of course illegal. */ | |
213 | if (ref <= idx) | |
214 | goto errout; | |
215 | ||
216 | ||
217 | em->data = ref; | |
218 | } else { | |
219 | /* Note: This lookup will increase the module refcnt | |
220 | * of the ematch module referenced. In case of a failure, | |
221 | * a destroy function is called by the underlying layer | |
222 | * which automatically releases the reference again, therefore | |
223 | * the module MUST not be given back under any circumstances | |
224 | * here. Be aware, the destroy function assumes that the | |
225 | * module is held if the ops field is non zero. */ | |
226 | em->ops = tcf_em_lookup(em_hdr->kind); | |
227 | ||
228 | if (em->ops == NULL) { | |
229 | err = -ENOENT; | |
230 | goto errout; | |
231 | } | |
232 | ||
233 | /* ematch module provides expected length of data, so we | |
234 | * can do a basic sanity check. */ | |
235 | if (em->ops->datalen && data_len < em->ops->datalen) | |
236 | goto errout; | |
237 | ||
238 | if (em->ops->change) { | |
239 | err = em->ops->change(tp, data, data_len, em); | |
240 | if (err < 0) | |
241 | goto errout; | |
242 | } else if (data_len > 0) { | |
243 | /* ematch module doesn't provide an own change | |
244 | * procedure and expects us to allocate and copy | |
245 | * the ematch data. | |
246 | * | |
247 | * TCF_EM_SIMPLE may be specified stating that the | |
248 | * data only consists of a u32 integer and the module | |
249 | * does not expected a memory reference but rather | |
250 | * the value carried. */ | |
251 | if (em_hdr->flags & TCF_EM_SIMPLE) { | |
252 | if (data_len < sizeof(u32)) | |
253 | goto errout; | |
254 | em->data = *(u32 *) data; | |
255 | } else { | |
256 | void *v = kmalloc(data_len, GFP_KERNEL); | |
257 | if (v == NULL) { | |
258 | err = -ENOBUFS; | |
259 | goto errout; | |
260 | } | |
261 | memcpy(v, data, data_len); | |
262 | em->data = (unsigned long) v; | |
263 | } | |
264 | } | |
265 | } | |
266 | ||
267 | em->matchid = em_hdr->matchid; | |
268 | em->flags = em_hdr->flags; | |
269 | em->datalen = data_len; | |
270 | ||
271 | err = 0; | |
272 | errout: | |
273 | return err; | |
274 | } | |
275 | ||
276 | /** | |
277 | * tcf_em_tree_validate - validate ematch config TLV and build ematch tree | |
278 | * | |
279 | * @tp: classifier kind handle | |
280 | * @rta: ematch tree configuration TLV | |
281 | * @tree: destination ematch tree variable to store the resulting | |
282 | * ematch tree. | |
283 | * | |
284 | * This function validates the given configuration TLV @rta and builds an | |
285 | * ematch tree in @tree. The resulting tree must later be copied into | |
286 | * the private classifier data using tcf_em_tree_change(). You MUST NOT | |
287 | * provide the ematch tree variable of the private classifier data directly, | |
288 | * the changes would not be locked properly. | |
289 | * | |
290 | * Returns a negative error code if the configuration TLV contains errors. | |
291 | */ | |
292 | int tcf_em_tree_validate(struct tcf_proto *tp, struct rtattr *rta, | |
293 | struct tcf_ematch_tree *tree) | |
294 | { | |
295 | int idx, list_len, matches_len, err = -EINVAL; | |
296 | struct rtattr *tb[TCA_EMATCH_TREE_MAX]; | |
297 | struct rtattr *rt_match, *rt_hdr, *rt_list; | |
298 | struct tcf_ematch_tree_hdr *tree_hdr; | |
299 | struct tcf_ematch *em; | |
300 | ||
301 | if (rtattr_parse_nested(tb, TCA_EMATCH_TREE_MAX, rta) < 0) | |
302 | goto errout; | |
303 | ||
304 | rt_hdr = tb[TCA_EMATCH_TREE_HDR-1]; | |
305 | rt_list = tb[TCA_EMATCH_TREE_LIST-1]; | |
306 | ||
307 | if (rt_hdr == NULL || rt_list == NULL) | |
308 | goto errout; | |
309 | ||
310 | if (RTA_PAYLOAD(rt_hdr) < sizeof(*tree_hdr) || | |
311 | RTA_PAYLOAD(rt_list) < sizeof(*rt_match)) | |
312 | goto errout; | |
313 | ||
314 | tree_hdr = RTA_DATA(rt_hdr); | |
315 | memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); | |
316 | ||
317 | rt_match = RTA_DATA(rt_list); | |
318 | list_len = RTA_PAYLOAD(rt_list); | |
319 | matches_len = tree_hdr->nmatches * sizeof(*em); | |
320 | ||
321 | tree->matches = kmalloc(matches_len, GFP_KERNEL); | |
322 | if (tree->matches == NULL) | |
323 | goto errout; | |
324 | memset(tree->matches, 0, matches_len); | |
325 | ||
326 | /* We do not use rtattr_parse_nested here because the maximum | |
327 | * number of attributes is unknown. This saves us the allocation | |
328 | * for a tb buffer which would serve no purpose at all. | |
329 | * | |
330 | * The array of rt attributes is parsed in the order as they are | |
331 | * provided, their type must be incremental from 1 to n. Even | |
332 | * if it does not serve any real purpose, a failure of sticking | |
333 | * to this policy will result in parsing failure. */ | |
334 | for (idx = 0; RTA_OK(rt_match, list_len); idx++) { | |
335 | err = -EINVAL; | |
336 | ||
337 | if (rt_match->rta_type != (idx + 1)) | |
338 | goto errout_abort; | |
339 | ||
340 | if (idx >= tree_hdr->nmatches) | |
341 | goto errout_abort; | |
342 | ||
343 | if (RTA_PAYLOAD(rt_match) < sizeof(struct tcf_ematch_hdr)) | |
344 | goto errout_abort; | |
345 | ||
346 | em = tcf_em_get_match(tree, idx); | |
347 | ||
348 | err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx); | |
349 | if (err < 0) | |
350 | goto errout_abort; | |
351 | ||
352 | rt_match = RTA_NEXT(rt_match, list_len); | |
353 | } | |
354 | ||
355 | /* Check if the number of matches provided by userspace actually | |
356 | * complies with the array of matches. The number was used for | |
357 | * the validation of references and a mismatch could lead to | |
358 | * undefined references during the matching process. */ | |
359 | if (idx != tree_hdr->nmatches) { | |
360 | err = -EINVAL; | |
361 | goto errout_abort; | |
362 | } | |
363 | ||
364 | err = 0; | |
365 | errout: | |
366 | return err; | |
367 | ||
368 | errout_abort: | |
369 | tcf_em_tree_destroy(tp, tree); | |
370 | return err; | |
371 | } | |
372 | ||
373 | /** | |
374 | * tcf_em_tree_destroy - destroy an ematch tree | |
375 | * | |
376 | * @tp: classifier kind handle | |
377 | * @tree: ematch tree to be deleted | |
378 | * | |
379 | * This functions destroys an ematch tree previously created by | |
380 | * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that | |
381 | * the ematch tree is not in use before calling this function. | |
382 | */ | |
383 | void tcf_em_tree_destroy(struct tcf_proto *tp, struct tcf_ematch_tree *tree) | |
384 | { | |
385 | int i; | |
386 | ||
387 | if (tree->matches == NULL) | |
388 | return; | |
389 | ||
390 | for (i = 0; i < tree->hdr.nmatches; i++) { | |
391 | struct tcf_ematch *em = tcf_em_get_match(tree, i); | |
392 | ||
393 | if (em->ops) { | |
394 | if (em->ops->destroy) | |
395 | em->ops->destroy(tp, em); | |
396 | else if (!tcf_em_is_simple(em) && em->data) | |
397 | kfree((void *) em->data); | |
398 | module_put(em->ops->owner); | |
399 | } | |
400 | } | |
401 | ||
402 | tree->hdr.nmatches = 0; | |
403 | kfree(tree->matches); | |
404 | } | |
405 | ||
406 | /** | |
407 | * tcf_em_tree_dump - dump ematch tree into a rtnl message | |
408 | * | |
409 | * @skb: skb holding the rtnl message | |
410 | * @t: ematch tree to be dumped | |
411 | * @tlv: TLV type to be used to encapsulate the tree | |
412 | * | |
413 | * This function dumps a ematch tree into a rtnl message. It is valid to | |
414 | * call this function while the ematch tree is in use. | |
415 | * | |
416 | * Returns -1 if the skb tailroom is insufficient. | |
417 | */ | |
418 | int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) | |
419 | { | |
420 | int i; | |
421 | struct rtattr * top_start = (struct rtattr*) skb->tail; | |
422 | struct rtattr * list_start; | |
423 | ||
424 | RTA_PUT(skb, tlv, 0, NULL); | |
425 | RTA_PUT(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr); | |
426 | ||
427 | list_start = (struct rtattr *) skb->tail; | |
428 | RTA_PUT(skb, TCA_EMATCH_TREE_LIST, 0, NULL); | |
429 | ||
430 | for (i = 0; i < tree->hdr.nmatches; i++) { | |
431 | struct rtattr *match_start = (struct rtattr*) skb->tail; | |
432 | struct tcf_ematch *em = tcf_em_get_match(tree, i); | |
433 | struct tcf_ematch_hdr em_hdr = { | |
434 | .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, | |
435 | .matchid = em->matchid, | |
436 | .flags = em->flags | |
437 | }; | |
438 | ||
439 | RTA_PUT(skb, i+1, sizeof(em_hdr), &em_hdr); | |
440 | ||
441 | if (em->ops && em->ops->dump) { | |
442 | if (em->ops->dump(skb, em) < 0) | |
443 | goto rtattr_failure; | |
444 | } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { | |
445 | u32 u = em->data; | |
446 | RTA_PUT_NOHDR(skb, sizeof(u), &u); | |
447 | } else if (em->datalen > 0) | |
448 | RTA_PUT_NOHDR(skb, em->datalen, (void *) em->data); | |
449 | ||
450 | match_start->rta_len = skb->tail - (u8*) match_start; | |
451 | } | |
452 | ||
453 | list_start->rta_len = skb->tail - (u8 *) list_start; | |
454 | top_start->rta_len = skb->tail - (u8 *) top_start; | |
455 | ||
456 | return 0; | |
457 | ||
458 | rtattr_failure: | |
459 | return -1; | |
460 | } | |
461 | ||
462 | static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, | |
463 | struct tcf_pkt_info *info) | |
464 | { | |
465 | int r = em->ops->match(skb, em, info); | |
466 | return tcf_em_is_inverted(em) ? !r : r; | |
467 | } | |
468 | ||
469 | /* Do not use this function directly, use tcf_em_tree_match instead */ | |
470 | int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, | |
471 | struct tcf_pkt_info *info) | |
472 | { | |
473 | int stackp = 0, match_idx = 0, res = 0; | |
474 | struct tcf_ematch *cur_match; | |
475 | int stack[CONFIG_NET_EMATCH_STACK]; | |
476 | ||
477 | proceed: | |
478 | while (match_idx < tree->hdr.nmatches) { | |
479 | cur_match = tcf_em_get_match(tree, match_idx); | |
480 | ||
481 | if (tcf_em_is_container(cur_match)) { | |
482 | if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) | |
483 | goto stack_overflow; | |
484 | ||
485 | stack[stackp++] = match_idx; | |
486 | match_idx = cur_match->data; | |
487 | goto proceed; | |
488 | } | |
489 | ||
490 | res = tcf_em_match(skb, cur_match, info); | |
491 | ||
492 | if (tcf_em_early_end(cur_match, res)) | |
493 | break; | |
494 | ||
495 | match_idx++; | |
496 | } | |
497 | ||
498 | pop_stack: | |
499 | if (stackp > 0) { | |
500 | match_idx = stack[--stackp]; | |
501 | cur_match = tcf_em_get_match(tree, match_idx); | |
502 | ||
503 | if (tcf_em_early_end(cur_match, res)) | |
504 | goto pop_stack; | |
505 | else { | |
506 | match_idx++; | |
507 | goto proceed; | |
508 | } | |
509 | } | |
510 | ||
511 | return res; | |
512 | ||
513 | stack_overflow: | |
514 | if (net_ratelimit()) | |
515 | printk("Local stack overflow, increase NET_EMATCH_STACK\n"); | |
516 | return -1; | |
517 | } | |
518 | ||
519 | EXPORT_SYMBOL(tcf_em_register); | |
520 | EXPORT_SYMBOL(tcf_em_unregister); | |
521 | EXPORT_SYMBOL(tcf_em_tree_validate); | |
522 | EXPORT_SYMBOL(tcf_em_tree_destroy); | |
523 | EXPORT_SYMBOL(tcf_em_tree_dump); | |
524 | EXPORT_SYMBOL(__tcf_em_tree_match); |