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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. | |
10297b99 | 40 | * |
1da177e4 LT |
41 | * ========================================================================== |
42 | * | |
43 | * How to write an ematch in 60 seconds | |
44 | * ------------------------------------ | |
10297b99 | 45 | * |
1da177e4 LT |
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 | ||
1da177e4 LT |
84 | #include <linux/module.h> |
85 | #include <linux/types.h> | |
86 | #include <linux/kernel.h> | |
1da177e4 | 87 | #include <linux/errno.h> |
1da177e4 LT |
88 | #include <linux/rtnetlink.h> |
89 | #include <linux/skbuff.h> | |
90 | #include <net/pkt_cls.h> | |
1da177e4 LT |
91 | |
92 | static LIST_HEAD(ematch_ops); | |
93 | static DEFINE_RWLOCK(ematch_mod_lock); | |
94 | ||
95 | static inline struct tcf_ematch_ops * tcf_em_lookup(u16 kind) | |
96 | { | |
97 | struct tcf_ematch_ops *e = NULL; | |
98 | ||
99 | read_lock(&ematch_mod_lock); | |
100 | list_for_each_entry(e, &ematch_ops, link) { | |
101 | if (kind == e->kind) { | |
102 | if (!try_module_get(e->owner)) | |
103 | e = NULL; | |
104 | read_unlock(&ematch_mod_lock); | |
105 | return e; | |
106 | } | |
107 | } | |
108 | read_unlock(&ematch_mod_lock); | |
109 | ||
110 | return NULL; | |
111 | } | |
112 | ||
113 | /** | |
114 | * tcf_em_register - register an extended match | |
10297b99 | 115 | * |
1da177e4 LT |
116 | * @ops: ematch operations lookup table |
117 | * | |
118 | * This function must be called by ematches to announce their presence. | |
119 | * The given @ops must have kind set to a unique identifier and the | |
120 | * callback match() must be implemented. All other callbacks are optional | |
121 | * and a fallback implementation is used instead. | |
122 | * | |
123 | * Returns -EEXISTS if an ematch of the same kind has already registered. | |
124 | */ | |
125 | int tcf_em_register(struct tcf_ematch_ops *ops) | |
126 | { | |
127 | int err = -EEXIST; | |
128 | struct tcf_ematch_ops *e; | |
129 | ||
130 | if (ops->match == NULL) | |
131 | return -EINVAL; | |
132 | ||
133 | write_lock(&ematch_mod_lock); | |
134 | list_for_each_entry(e, &ematch_ops, link) | |
135 | if (ops->kind == e->kind) | |
136 | goto errout; | |
137 | ||
138 | list_add_tail(&ops->link, &ematch_ops); | |
139 | err = 0; | |
140 | errout: | |
141 | write_unlock(&ematch_mod_lock); | |
142 | return err; | |
143 | } | |
62e3ba1b | 144 | EXPORT_SYMBOL(tcf_em_register); |
1da177e4 LT |
145 | |
146 | /** | |
147 | * tcf_em_unregister - unregster and extended match | |
148 | * | |
149 | * @ops: ematch operations lookup table | |
150 | * | |
151 | * This function must be called by ematches to announce their disappearance | |
152 | * for examples when the module gets unloaded. The @ops parameter must be | |
153 | * the same as the one used for registration. | |
154 | * | |
155 | * Returns -ENOENT if no matching ematch was found. | |
156 | */ | |
157 | int tcf_em_unregister(struct tcf_ematch_ops *ops) | |
158 | { | |
159 | int err = 0; | |
160 | struct tcf_ematch_ops *e; | |
161 | ||
162 | write_lock(&ematch_mod_lock); | |
163 | list_for_each_entry(e, &ematch_ops, link) { | |
164 | if (e == ops) { | |
165 | list_del(&e->link); | |
166 | goto out; | |
167 | } | |
168 | } | |
169 | ||
170 | err = -ENOENT; | |
171 | out: | |
172 | write_unlock(&ematch_mod_lock); | |
173 | return err; | |
174 | } | |
62e3ba1b | 175 | EXPORT_SYMBOL(tcf_em_unregister); |
1da177e4 LT |
176 | |
177 | static inline struct tcf_ematch * tcf_em_get_match(struct tcf_ematch_tree *tree, | |
178 | int index) | |
179 | { | |
180 | return &tree->matches[index]; | |
181 | } | |
182 | ||
183 | ||
184 | static int tcf_em_validate(struct tcf_proto *tp, | |
185 | struct tcf_ematch_tree_hdr *tree_hdr, | |
add93b61 | 186 | struct tcf_ematch *em, struct nlattr *nla, int idx) |
1da177e4 LT |
187 | { |
188 | int err = -EINVAL; | |
add93b61 PM |
189 | struct tcf_ematch_hdr *em_hdr = nla_data(nla); |
190 | int data_len = nla_len(nla) - sizeof(*em_hdr); | |
1da177e4 LT |
191 | void *data = (void *) em_hdr + sizeof(*em_hdr); |
192 | ||
193 | if (!TCF_EM_REL_VALID(em_hdr->flags)) | |
194 | goto errout; | |
195 | ||
196 | if (em_hdr->kind == TCF_EM_CONTAINER) { | |
197 | /* Special ematch called "container", carries an index | |
198 | * referencing an external ematch sequence. */ | |
199 | u32 ref; | |
200 | ||
201 | if (data_len < sizeof(ref)) | |
202 | goto errout; | |
203 | ref = *(u32 *) data; | |
204 | ||
205 | if (ref >= tree_hdr->nmatches) | |
206 | goto errout; | |
207 | ||
208 | /* We do not allow backward jumps to avoid loops and jumps | |
209 | * to our own position are of course illegal. */ | |
210 | if (ref <= idx) | |
211 | goto errout; | |
212 | ||
10297b99 | 213 | |
1da177e4 LT |
214 | em->data = ref; |
215 | } else { | |
216 | /* Note: This lookup will increase the module refcnt | |
217 | * of the ematch module referenced. In case of a failure, | |
218 | * a destroy function is called by the underlying layer | |
219 | * which automatically releases the reference again, therefore | |
220 | * the module MUST not be given back under any circumstances | |
221 | * here. Be aware, the destroy function assumes that the | |
222 | * module is held if the ops field is non zero. */ | |
223 | em->ops = tcf_em_lookup(em_hdr->kind); | |
224 | ||
225 | if (em->ops == NULL) { | |
226 | err = -ENOENT; | |
db3d99c0 PM |
227 | #ifdef CONFIG_KMOD |
228 | __rtnl_unlock(); | |
229 | request_module("ematch-kind-%u", em_hdr->kind); | |
230 | rtnl_lock(); | |
231 | em->ops = tcf_em_lookup(em_hdr->kind); | |
232 | if (em->ops) { | |
233 | /* We dropped the RTNL mutex in order to | |
234 | * perform the module load. Tell the caller | |
235 | * to replay the request. */ | |
236 | module_put(em->ops->owner); | |
237 | err = -EAGAIN; | |
238 | } | |
239 | #endif | |
1da177e4 LT |
240 | goto errout; |
241 | } | |
242 | ||
243 | /* ematch module provides expected length of data, so we | |
244 | * can do a basic sanity check. */ | |
245 | if (em->ops->datalen && data_len < em->ops->datalen) | |
246 | goto errout; | |
247 | ||
248 | if (em->ops->change) { | |
249 | err = em->ops->change(tp, data, data_len, em); | |
250 | if (err < 0) | |
251 | goto errout; | |
252 | } else if (data_len > 0) { | |
253 | /* ematch module doesn't provide an own change | |
254 | * procedure and expects us to allocate and copy | |
255 | * the ematch data. | |
256 | * | |
257 | * TCF_EM_SIMPLE may be specified stating that the | |
258 | * data only consists of a u32 integer and the module | |
259 | * does not expected a memory reference but rather | |
260 | * the value carried. */ | |
261 | if (em_hdr->flags & TCF_EM_SIMPLE) { | |
262 | if (data_len < sizeof(u32)) | |
263 | goto errout; | |
264 | em->data = *(u32 *) data; | |
265 | } else { | |
c7b1b249 | 266 | void *v = kmemdup(data, data_len, GFP_KERNEL); |
1da177e4 LT |
267 | if (v == NULL) { |
268 | err = -ENOBUFS; | |
269 | goto errout; | |
270 | } | |
1da177e4 LT |
271 | em->data = (unsigned long) v; |
272 | } | |
273 | } | |
274 | } | |
275 | ||
276 | em->matchid = em_hdr->matchid; | |
277 | em->flags = em_hdr->flags; | |
278 | em->datalen = data_len; | |
279 | ||
280 | err = 0; | |
281 | errout: | |
282 | return err; | |
283 | } | |
284 | ||
285 | /** | |
286 | * tcf_em_tree_validate - validate ematch config TLV and build ematch tree | |
287 | * | |
288 | * @tp: classifier kind handle | |
add93b61 | 289 | * @nla: ematch tree configuration TLV |
1da177e4 LT |
290 | * @tree: destination ematch tree variable to store the resulting |
291 | * ematch tree. | |
292 | * | |
add93b61 | 293 | * This function validates the given configuration TLV @nla and builds an |
1da177e4 LT |
294 | * ematch tree in @tree. The resulting tree must later be copied into |
295 | * the private classifier data using tcf_em_tree_change(). You MUST NOT | |
296 | * provide the ematch tree variable of the private classifier data directly, | |
297 | * the changes would not be locked properly. | |
298 | * | |
299 | * Returns a negative error code if the configuration TLV contains errors. | |
300 | */ | |
add93b61 | 301 | int tcf_em_tree_validate(struct tcf_proto *tp, struct nlattr *nla, |
1da177e4 LT |
302 | struct tcf_ematch_tree *tree) |
303 | { | |
cee63723 | 304 | int idx, list_len, matches_len, err; |
add93b61 PM |
305 | struct nlattr *tb[TCA_EMATCH_TREE_MAX + 1]; |
306 | struct nlattr *rt_match, *rt_hdr, *rt_list; | |
1da177e4 LT |
307 | struct tcf_ematch_tree_hdr *tree_hdr; |
308 | struct tcf_ematch *em; | |
309 | ||
add93b61 | 310 | if (!nla) { |
b541ca2c TG |
311 | memset(tree, 0, sizeof(*tree)); |
312 | return 0; | |
313 | } | |
314 | ||
cee63723 PM |
315 | err = nla_parse_nested(tb, TCA_EMATCH_TREE_MAX, nla, NULL); |
316 | if (err < 0) | |
1da177e4 LT |
317 | goto errout; |
318 | ||
cee63723 | 319 | err = -EINVAL; |
add93b61 PM |
320 | rt_hdr = tb[TCA_EMATCH_TREE_HDR]; |
321 | rt_list = tb[TCA_EMATCH_TREE_LIST]; | |
1da177e4 LT |
322 | |
323 | if (rt_hdr == NULL || rt_list == NULL) | |
324 | goto errout; | |
325 | ||
add93b61 PM |
326 | if (nla_len(rt_hdr) < sizeof(*tree_hdr) || |
327 | nla_len(rt_list) < sizeof(*rt_match)) | |
1da177e4 LT |
328 | goto errout; |
329 | ||
add93b61 | 330 | tree_hdr = nla_data(rt_hdr); |
1da177e4 LT |
331 | memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); |
332 | ||
add93b61 PM |
333 | rt_match = nla_data(rt_list); |
334 | list_len = nla_len(rt_list); | |
1da177e4 LT |
335 | matches_len = tree_hdr->nmatches * sizeof(*em); |
336 | ||
0da974f4 | 337 | tree->matches = kzalloc(matches_len, GFP_KERNEL); |
1da177e4 LT |
338 | if (tree->matches == NULL) |
339 | goto errout; | |
1da177e4 | 340 | |
add93b61 | 341 | /* We do not use nla_parse_nested here because the maximum |
1da177e4 LT |
342 | * number of attributes is unknown. This saves us the allocation |
343 | * for a tb buffer which would serve no purpose at all. | |
10297b99 | 344 | * |
1da177e4 LT |
345 | * The array of rt attributes is parsed in the order as they are |
346 | * provided, their type must be incremental from 1 to n. Even | |
347 | * if it does not serve any real purpose, a failure of sticking | |
348 | * to this policy will result in parsing failure. */ | |
add93b61 | 349 | for (idx = 0; nla_ok(rt_match, list_len); idx++) { |
1da177e4 LT |
350 | err = -EINVAL; |
351 | ||
add93b61 | 352 | if (rt_match->nla_type != (idx + 1)) |
1da177e4 LT |
353 | goto errout_abort; |
354 | ||
355 | if (idx >= tree_hdr->nmatches) | |
356 | goto errout_abort; | |
357 | ||
add93b61 | 358 | if (nla_len(rt_match) < sizeof(struct tcf_ematch_hdr)) |
1da177e4 LT |
359 | goto errout_abort; |
360 | ||
361 | em = tcf_em_get_match(tree, idx); | |
362 | ||
363 | err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx); | |
364 | if (err < 0) | |
365 | goto errout_abort; | |
366 | ||
add93b61 | 367 | rt_match = nla_next(rt_match, &list_len); |
1da177e4 LT |
368 | } |
369 | ||
370 | /* Check if the number of matches provided by userspace actually | |
371 | * complies with the array of matches. The number was used for | |
372 | * the validation of references and a mismatch could lead to | |
373 | * undefined references during the matching process. */ | |
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(tp, tree); | |
385 | return err; | |
386 | } | |
62e3ba1b | 387 | EXPORT_SYMBOL(tcf_em_tree_validate); |
1da177e4 LT |
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_proto *tp, 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(tp, em); | |
412 | else if (!tcf_em_is_simple(em) && em->data) | |
413 | kfree((void *) em->data); | |
414 | module_put(em->ops->owner); | |
415 | } | |
416 | } | |
10297b99 | 417 | |
1da177e4 LT |
418 | tree->hdr.nmatches = 0; |
419 | kfree(tree->matches); | |
420 | } | |
62e3ba1b | 421 | EXPORT_SYMBOL(tcf_em_tree_destroy); |
1da177e4 LT |
422 | |
423 | /** | |
424 | * tcf_em_tree_dump - dump ematch tree into a rtnl message | |
425 | * | |
426 | * @skb: skb holding the rtnl message | |
427 | * @t: ematch tree to be dumped | |
428 | * @tlv: TLV type to be used to encapsulate the tree | |
429 | * | |
430 | * This function dumps a ematch tree into a rtnl message. It is valid to | |
431 | * call this function while the ematch tree is in use. | |
432 | * | |
433 | * Returns -1 if the skb tailroom is insufficient. | |
434 | */ | |
435 | int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) | |
436 | { | |
437 | int i; | |
27a884dc | 438 | u8 *tail; |
4b3550ef | 439 | struct nlattr *top_start; |
add93b61 | 440 | struct nlattr *list_start; |
1da177e4 | 441 | |
4b3550ef PM |
442 | top_start = nla_nest_start(skb, tlv); |
443 | if (top_start == NULL) | |
444 | goto nla_put_failure; | |
445 | ||
add93b61 | 446 | NLA_PUT(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr); |
1da177e4 | 447 | |
4b3550ef PM |
448 | list_start = nla_nest_start(skb, TCA_EMATCH_TREE_LIST); |
449 | if (list_start == NULL) | |
450 | goto nla_put_failure; | |
1da177e4 | 451 | |
27a884dc | 452 | tail = skb_tail_pointer(skb); |
1da177e4 | 453 | for (i = 0; i < tree->hdr.nmatches; i++) { |
add93b61 | 454 | struct nlattr *match_start = (struct nlattr *)tail; |
1da177e4 LT |
455 | struct tcf_ematch *em = tcf_em_get_match(tree, i); |
456 | struct tcf_ematch_hdr em_hdr = { | |
457 | .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, | |
458 | .matchid = em->matchid, | |
459 | .flags = em->flags | |
460 | }; | |
461 | ||
add93b61 | 462 | NLA_PUT(skb, i+1, sizeof(em_hdr), &em_hdr); |
1da177e4 LT |
463 | |
464 | if (em->ops && em->ops->dump) { | |
465 | if (em->ops->dump(skb, em) < 0) | |
add93b61 | 466 | goto nla_put_failure; |
1da177e4 LT |
467 | } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { |
468 | u32 u = em->data; | |
add93b61 | 469 | nla_put_nohdr(skb, sizeof(u), &u); |
1da177e4 | 470 | } else if (em->datalen > 0) |
add93b61 | 471 | nla_put_nohdr(skb, em->datalen, (void *) em->data); |
1da177e4 | 472 | |
27a884dc | 473 | tail = skb_tail_pointer(skb); |
add93b61 | 474 | match_start->nla_len = tail - (u8 *)match_start; |
1da177e4 LT |
475 | } |
476 | ||
4b3550ef PM |
477 | nla_nest_end(skb, list_start); |
478 | nla_nest_end(skb, top_start); | |
1da177e4 LT |
479 | |
480 | return 0; | |
481 | ||
add93b61 | 482 | nla_put_failure: |
1da177e4 LT |
483 | return -1; |
484 | } | |
62e3ba1b | 485 | EXPORT_SYMBOL(tcf_em_tree_dump); |
1da177e4 LT |
486 | |
487 | static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, | |
488 | struct tcf_pkt_info *info) | |
489 | { | |
490 | int r = em->ops->match(skb, em, info); | |
491 | return tcf_em_is_inverted(em) ? !r : r; | |
492 | } | |
493 | ||
494 | /* Do not use this function directly, use tcf_em_tree_match instead */ | |
495 | int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, | |
496 | struct tcf_pkt_info *info) | |
497 | { | |
498 | int stackp = 0, match_idx = 0, res = 0; | |
499 | struct tcf_ematch *cur_match; | |
500 | int stack[CONFIG_NET_EMATCH_STACK]; | |
501 | ||
502 | proceed: | |
503 | while (match_idx < tree->hdr.nmatches) { | |
504 | cur_match = tcf_em_get_match(tree, match_idx); | |
505 | ||
506 | if (tcf_em_is_container(cur_match)) { | |
507 | if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) | |
508 | goto stack_overflow; | |
509 | ||
510 | stack[stackp++] = match_idx; | |
511 | match_idx = cur_match->data; | |
512 | goto proceed; | |
513 | } | |
514 | ||
515 | res = tcf_em_match(skb, cur_match, info); | |
516 | ||
517 | if (tcf_em_early_end(cur_match, res)) | |
518 | break; | |
519 | ||
520 | match_idx++; | |
521 | } | |
522 | ||
523 | pop_stack: | |
524 | if (stackp > 0) { | |
525 | match_idx = stack[--stackp]; | |
526 | cur_match = tcf_em_get_match(tree, match_idx); | |
527 | ||
528 | if (tcf_em_early_end(cur_match, res)) | |
529 | goto pop_stack; | |
530 | else { | |
531 | match_idx++; | |
532 | goto proceed; | |
533 | } | |
534 | } | |
535 | ||
536 | return res; | |
537 | ||
538 | stack_overflow: | |
539 | if (net_ratelimit()) | |
540 | printk("Local stack overflow, increase NET_EMATCH_STACK\n"); | |
541 | return -1; | |
542 | } | |
1da177e4 | 543 | EXPORT_SYMBOL(__tcf_em_tree_match); |