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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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.
YOSHIFUJI Hideaki10297b92007-02-09 23:25:16 +090040 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 * ==========================================================================
42 *
43 * How to write an ematch in 60 seconds
44 * ------------------------------------
YOSHIFUJI Hideaki10297b92007-02-09 23:25:16 +090045 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070046 * 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070084#include <linux/module.h>
85#include <linux/types.h>
86#include <linux/kernel.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070087#include <linux/errno.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070088#include <linux/rtnetlink.h>
89#include <linux/skbuff.h>
90#include <net/pkt_cls.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070091
92static LIST_HEAD(ematch_ops);
93static DEFINE_RWLOCK(ematch_mod_lock);
94
95static 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
YOSHIFUJI Hideaki10297b92007-02-09 23:25:16 +0900115 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116 * @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 */
125int 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;
140errout:
141 write_unlock(&ematch_mod_lock);
142 return err;
143}
144
145/**
146 * tcf_em_unregister - unregster and extended match
147 *
148 * @ops: ematch operations lookup table
149 *
150 * This function must be called by ematches to announce their disappearance
151 * for examples when the module gets unloaded. The @ops parameter must be
152 * the same as the one used for registration.
153 *
154 * Returns -ENOENT if no matching ematch was found.
155 */
156int tcf_em_unregister(struct tcf_ematch_ops *ops)
157{
158 int err = 0;
159 struct tcf_ematch_ops *e;
160
161 write_lock(&ematch_mod_lock);
162 list_for_each_entry(e, &ematch_ops, link) {
163 if (e == ops) {
164 list_del(&e->link);
165 goto out;
166 }
167 }
168
169 err = -ENOENT;
170out:
171 write_unlock(&ematch_mod_lock);
172 return err;
173}
174
175static inline struct tcf_ematch * tcf_em_get_match(struct tcf_ematch_tree *tree,
176 int index)
177{
178 return &tree->matches[index];
179}
180
181
182static int tcf_em_validate(struct tcf_proto *tp,
183 struct tcf_ematch_tree_hdr *tree_hdr,
184 struct tcf_ematch *em, struct rtattr *rta, int idx)
185{
186 int err = -EINVAL;
187 struct tcf_ematch_hdr *em_hdr = RTA_DATA(rta);
188 int data_len = RTA_PAYLOAD(rta) - sizeof(*em_hdr);
189 void *data = (void *) em_hdr + sizeof(*em_hdr);
190
191 if (!TCF_EM_REL_VALID(em_hdr->flags))
192 goto errout;
193
194 if (em_hdr->kind == TCF_EM_CONTAINER) {
195 /* Special ematch called "container", carries an index
196 * referencing an external ematch sequence. */
197 u32 ref;
198
199 if (data_len < sizeof(ref))
200 goto errout;
201 ref = *(u32 *) data;
202
203 if (ref >= tree_hdr->nmatches)
204 goto errout;
205
206 /* We do not allow backward jumps to avoid loops and jumps
207 * to our own position are of course illegal. */
208 if (ref <= idx)
209 goto errout;
210
YOSHIFUJI Hideaki10297b92007-02-09 23:25:16 +0900211
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212 em->data = ref;
213 } else {
214 /* Note: This lookup will increase the module refcnt
215 * of the ematch module referenced. In case of a failure,
216 * a destroy function is called by the underlying layer
217 * which automatically releases the reference again, therefore
218 * the module MUST not be given back under any circumstances
219 * here. Be aware, the destroy function assumes that the
220 * module is held if the ops field is non zero. */
221 em->ops = tcf_em_lookup(em_hdr->kind);
222
223 if (em->ops == NULL) {
224 err = -ENOENT;
Patrick McHardydb3d99c2007-07-11 19:46:26 -0700225#ifdef CONFIG_KMOD
226 __rtnl_unlock();
227 request_module("ematch-kind-%u", em_hdr->kind);
228 rtnl_lock();
229 em->ops = tcf_em_lookup(em_hdr->kind);
230 if (em->ops) {
231 /* We dropped the RTNL mutex in order to
232 * perform the module load. Tell the caller
233 * to replay the request. */
234 module_put(em->ops->owner);
235 err = -EAGAIN;
236 }
237#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238 goto errout;
239 }
240
241 /* ematch module provides expected length of data, so we
242 * can do a basic sanity check. */
243 if (em->ops->datalen && data_len < em->ops->datalen)
244 goto errout;
245
246 if (em->ops->change) {
247 err = em->ops->change(tp, data, data_len, em);
248 if (err < 0)
249 goto errout;
250 } else if (data_len > 0) {
251 /* ematch module doesn't provide an own change
252 * procedure and expects us to allocate and copy
253 * the ematch data.
254 *
255 * TCF_EM_SIMPLE may be specified stating that the
256 * data only consists of a u32 integer and the module
257 * does not expected a memory reference but rather
258 * the value carried. */
259 if (em_hdr->flags & TCF_EM_SIMPLE) {
260 if (data_len < sizeof(u32))
261 goto errout;
262 em->data = *(u32 *) data;
263 } else {
Arnaldo Carvalho de Meloc7b1b242006-11-21 01:19:40 -0200264 void *v = kmemdup(data, data_len, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 if (v == NULL) {
266 err = -ENOBUFS;
267 goto errout;
268 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269 em->data = (unsigned long) v;
270 }
271 }
272 }
273
274 em->matchid = em_hdr->matchid;
275 em->flags = em_hdr->flags;
276 em->datalen = data_len;
277
278 err = 0;
279errout:
280 return err;
281}
282
283/**
284 * tcf_em_tree_validate - validate ematch config TLV and build ematch tree
285 *
286 * @tp: classifier kind handle
287 * @rta: ematch tree configuration TLV
288 * @tree: destination ematch tree variable to store the resulting
289 * ematch tree.
290 *
291 * This function validates the given configuration TLV @rta and builds an
292 * ematch tree in @tree. The resulting tree must later be copied into
293 * the private classifier data using tcf_em_tree_change(). You MUST NOT
294 * provide the ematch tree variable of the private classifier data directly,
295 * the changes would not be locked properly.
296 *
297 * Returns a negative error code if the configuration TLV contains errors.
298 */
299int tcf_em_tree_validate(struct tcf_proto *tp, struct rtattr *rta,
300 struct tcf_ematch_tree *tree)
301{
302 int idx, list_len, matches_len, err = -EINVAL;
303 struct rtattr *tb[TCA_EMATCH_TREE_MAX];
304 struct rtattr *rt_match, *rt_hdr, *rt_list;
305 struct tcf_ematch_tree_hdr *tree_hdr;
306 struct tcf_ematch *em;
307
Thomas Grafb541ca22005-11-08 09:39:17 -0800308 if (!rta) {
309 memset(tree, 0, sizeof(*tree));
310 return 0;
311 }
312
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 if (rtattr_parse_nested(tb, TCA_EMATCH_TREE_MAX, rta) < 0)
314 goto errout;
315
316 rt_hdr = tb[TCA_EMATCH_TREE_HDR-1];
317 rt_list = tb[TCA_EMATCH_TREE_LIST-1];
318
319 if (rt_hdr == NULL || rt_list == NULL)
320 goto errout;
321
322 if (RTA_PAYLOAD(rt_hdr) < sizeof(*tree_hdr) ||
323 RTA_PAYLOAD(rt_list) < sizeof(*rt_match))
324 goto errout;
325
326 tree_hdr = RTA_DATA(rt_hdr);
327 memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr));
328
329 rt_match = RTA_DATA(rt_list);
330 list_len = RTA_PAYLOAD(rt_list);
331 matches_len = tree_hdr->nmatches * sizeof(*em);
332
Panagiotis Issaris0da974f2006-07-21 14:51:30 -0700333 tree->matches = kzalloc(matches_len, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334 if (tree->matches == NULL)
335 goto errout;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700336
337 /* We do not use rtattr_parse_nested here because the maximum
338 * number of attributes is unknown. This saves us the allocation
339 * for a tb buffer which would serve no purpose at all.
YOSHIFUJI Hideaki10297b92007-02-09 23:25:16 +0900340 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 * The array of rt attributes is parsed in the order as they are
342 * provided, their type must be incremental from 1 to n. Even
343 * if it does not serve any real purpose, a failure of sticking
344 * to this policy will result in parsing failure. */
345 for (idx = 0; RTA_OK(rt_match, list_len); idx++) {
346 err = -EINVAL;
347
348 if (rt_match->rta_type != (idx + 1))
349 goto errout_abort;
350
351 if (idx >= tree_hdr->nmatches)
352 goto errout_abort;
353
354 if (RTA_PAYLOAD(rt_match) < sizeof(struct tcf_ematch_hdr))
355 goto errout_abort;
356
357 em = tcf_em_get_match(tree, idx);
358
359 err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx);
360 if (err < 0)
361 goto errout_abort;
362
363 rt_match = RTA_NEXT(rt_match, list_len);
364 }
365
366 /* Check if the number of matches provided by userspace actually
367 * complies with the array of matches. The number was used for
368 * the validation of references and a mismatch could lead to
369 * undefined references during the matching process. */
370 if (idx != tree_hdr->nmatches) {
371 err = -EINVAL;
372 goto errout_abort;
373 }
374
375 err = 0;
376errout:
377 return err;
378
379errout_abort:
380 tcf_em_tree_destroy(tp, tree);
381 return err;
382}
383
384/**
385 * tcf_em_tree_destroy - destroy an ematch tree
386 *
387 * @tp: classifier kind handle
388 * @tree: ematch tree to be deleted
389 *
390 * This functions destroys an ematch tree previously created by
391 * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that
392 * the ematch tree is not in use before calling this function.
393 */
394void tcf_em_tree_destroy(struct tcf_proto *tp, struct tcf_ematch_tree *tree)
395{
396 int i;
397
398 if (tree->matches == NULL)
399 return;
400
401 for (i = 0; i < tree->hdr.nmatches; i++) {
402 struct tcf_ematch *em = tcf_em_get_match(tree, i);
403
404 if (em->ops) {
405 if (em->ops->destroy)
406 em->ops->destroy(tp, em);
407 else if (!tcf_em_is_simple(em) && em->data)
408 kfree((void *) em->data);
409 module_put(em->ops->owner);
410 }
411 }
YOSHIFUJI Hideaki10297b92007-02-09 23:25:16 +0900412
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 tree->hdr.nmatches = 0;
414 kfree(tree->matches);
415}
416
417/**
418 * tcf_em_tree_dump - dump ematch tree into a rtnl message
419 *
420 * @skb: skb holding the rtnl message
421 * @t: ematch tree to be dumped
422 * @tlv: TLV type to be used to encapsulate the tree
423 *
424 * This function dumps a ematch tree into a rtnl message. It is valid to
425 * call this function while the ematch tree is in use.
426 *
427 * Returns -1 if the skb tailroom is insufficient.
428 */
429int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv)
430{
431 int i;
Arnaldo Carvalho de Melo27a884d2007-04-19 20:29:13 -0700432 u8 *tail;
433 struct rtattr *top_start = (struct rtattr *)skb_tail_pointer(skb);
434 struct rtattr *list_start;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435
436 RTA_PUT(skb, tlv, 0, NULL);
437 RTA_PUT(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr);
438
Arnaldo Carvalho de Melo27a884d2007-04-19 20:29:13 -0700439 list_start = (struct rtattr *)skb_tail_pointer(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 RTA_PUT(skb, TCA_EMATCH_TREE_LIST, 0, NULL);
441
Arnaldo Carvalho de Melo27a884d2007-04-19 20:29:13 -0700442 tail = skb_tail_pointer(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443 for (i = 0; i < tree->hdr.nmatches; i++) {
Arnaldo Carvalho de Melo27a884d2007-04-19 20:29:13 -0700444 struct rtattr *match_start = (struct rtattr *)tail;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 struct tcf_ematch *em = tcf_em_get_match(tree, i);
446 struct tcf_ematch_hdr em_hdr = {
447 .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER,
448 .matchid = em->matchid,
449 .flags = em->flags
450 };
451
452 RTA_PUT(skb, i+1, sizeof(em_hdr), &em_hdr);
453
454 if (em->ops && em->ops->dump) {
455 if (em->ops->dump(skb, em) < 0)
456 goto rtattr_failure;
457 } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) {
458 u32 u = em->data;
459 RTA_PUT_NOHDR(skb, sizeof(u), &u);
460 } else if (em->datalen > 0)
461 RTA_PUT_NOHDR(skb, em->datalen, (void *) em->data);
462
Arnaldo Carvalho de Melo27a884d2007-04-19 20:29:13 -0700463 tail = skb_tail_pointer(skb);
464 match_start->rta_len = tail - (u8 *)match_start;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700465 }
466
Arnaldo Carvalho de Melo27a884d2007-04-19 20:29:13 -0700467 list_start->rta_len = tail - (u8 *)list_start;
468 top_start->rta_len = tail - (u8 *)top_start;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469
470 return 0;
471
472rtattr_failure:
473 return -1;
474}
475
476static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em,
477 struct tcf_pkt_info *info)
478{
479 int r = em->ops->match(skb, em, info);
480 return tcf_em_is_inverted(em) ? !r : r;
481}
482
483/* Do not use this function directly, use tcf_em_tree_match instead */
484int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree,
485 struct tcf_pkt_info *info)
486{
487 int stackp = 0, match_idx = 0, res = 0;
488 struct tcf_ematch *cur_match;
489 int stack[CONFIG_NET_EMATCH_STACK];
490
491proceed:
492 while (match_idx < tree->hdr.nmatches) {
493 cur_match = tcf_em_get_match(tree, match_idx);
494
495 if (tcf_em_is_container(cur_match)) {
496 if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK))
497 goto stack_overflow;
498
499 stack[stackp++] = match_idx;
500 match_idx = cur_match->data;
501 goto proceed;
502 }
503
504 res = tcf_em_match(skb, cur_match, info);
505
506 if (tcf_em_early_end(cur_match, res))
507 break;
508
509 match_idx++;
510 }
511
512pop_stack:
513 if (stackp > 0) {
514 match_idx = stack[--stackp];
515 cur_match = tcf_em_get_match(tree, match_idx);
516
517 if (tcf_em_early_end(cur_match, res))
518 goto pop_stack;
519 else {
520 match_idx++;
521 goto proceed;
522 }
523 }
524
525 return res;
526
527stack_overflow:
528 if (net_ratelimit())
529 printk("Local stack overflow, increase NET_EMATCH_STACK\n");
530 return -1;
531}
532
533EXPORT_SYMBOL(tcf_em_register);
534EXPORT_SYMBOL(tcf_em_unregister);
535EXPORT_SYMBOL(tcf_em_tree_validate);
536EXPORT_SYMBOL(tcf_em_tree_destroy);
537EXPORT_SYMBOL(tcf_em_tree_dump);
538EXPORT_SYMBOL(__tcf_em_tree_match);