1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * net/sched/ematch.c Extended Match API
4 *
5 * Authors: Thomas Graf <tgraf@suug.ch>
6 *
7 * ==========================================================================
8 *
9 * An extended match (ematch) is a small classification tool not worth
10 * writing a full classifier for. Ematches can be interconnected to form
11 * a logic expression and get attached to classifiers to extend their
12 * functionatlity.
13 *
14 * The userspace part transforms the logic expressions into an array
15 * consisting of multiple sequences of interconnected ematches separated
16 * by markers. Precedence is implemented by a special ematch kind
17 * referencing a sequence beyond the marker of the current sequence
18 * causing the current position in the sequence to be pushed onto a stack
19 * to allow the current position to be overwritten by the position referenced
20 * in the special ematch. Matching continues in the new sequence until a
21 * marker is reached causing the position to be restored from the stack.
22 *
23 * Example:
24 * A AND (B1 OR B2) AND C AND D
25 *
26 * ------->-PUSH-------
27 * -->-- / -->-- \ -->--
28 * / \ / / \ \ / \
29 * +-------+-------+-------+-------+-------+--------+
30 * | A AND | B AND | C AND | D END | B1 OR | B2 END |
31 * +-------+-------+-------+-------+-------+--------+
32 * \ /
33 * --------<-POP---------
34 *
35 * where B is a virtual ematch referencing to sequence starting with B1.
36 *
37 * ==========================================================================
38 *
39 * How to write an ematch in 60 seconds
40 * ------------------------------------
41 *
42 * 1) Provide a matcher function:
43 * static int my_match(struct sk_buff *skb, struct tcf_ematch *m,
44 * struct tcf_pkt_info *info)
45 * {
46 * struct mydata *d = (struct mydata *) m->data;
47 *
48 * if (...matching goes here...)
49 * return 1;
50 * else
51 * return 0;
52 * }
53 *
54 * 2) Fill out a struct tcf_ematch_ops:
55 * static struct tcf_ematch_ops my_ops = {
56 * .kind = unique id,
57 * .datalen = sizeof(struct mydata),
58 * .match = my_match,
59 * .owner = THIS_MODULE,
60 * };
61 *
62 * 3) Register/Unregister your ematch:
63 * static int __init init_my_ematch(void)
64 * {
65 * return tcf_em_register(&my_ops);
66 * }
67 *
68 * static void __exit exit_my_ematch(void)
69 * {
70 * tcf_em_unregister(&my_ops);
71 * }
72 *
73 * module_init(init_my_ematch);
74 * module_exit(exit_my_ematch);
75 *
76 * 4) By now you should have two more seconds left, barely enough to
77 * open up a beer to watch the compilation going.
78 */
79
80 #include <linux/module.h>
81 #include <linux/slab.h>
82 #include <linux/types.h>
83 #include <linux/kernel.h>
84 #include <linux/errno.h>
85 #include <linux/rtnetlink.h>
86 #include <linux/skbuff.h>
87 #include <net/pkt_cls.h>
88
89 static LIST_HEAD(ematch_ops);
90 static DEFINE_RWLOCK(ematch_mod_lock);
91
92 static struct tcf_ematch_ops *tcf_em_lookup(u16 kind)
93 {
94 struct tcf_ematch_ops *e = NULL;
95
96 read_lock(&ematch_mod_lock);
97 list_for_each_entry(e, &ematch_ops, link) {
98 if (kind == e->kind) {
99 if (!try_module_get(e->owner))
100 e = NULL;
101 read_unlock(&ematch_mod_lock);
102 return e;
103 }
104 }
105 read_unlock(&ematch_mod_lock);
106
107 return NULL;
108 }
109
110 /**
111 * tcf_em_register - register an extended match
112 *
113 * @ops: ematch operations lookup table
114 *
115 * This function must be called by ematches to announce their presence.
116 * The given @ops must have kind set to a unique identifier and the
117 * callback match() must be implemented. All other callbacks are optional
118 * and a fallback implementation is used instead.
119 *
120 * Returns -EEXISTS if an ematch of the same kind has already registered.
121 */
122 int tcf_em_register(struct tcf_ematch_ops *ops)
123 {
124 int err = -EEXIST;
125 struct tcf_ematch_ops *e;
126
127 if (ops->match == NULL)
128 return -EINVAL;
129
130 write_lock(&ematch_mod_lock);
131 list_for_each_entry(e, &ematch_ops, link)
132 if (ops->kind == e->kind)
133 goto errout;
134
135 list_add_tail(&ops->link, &ematch_ops);
136 err = 0;
137 errout:
138 write_unlock(&ematch_mod_lock);
139 return err;
140 }
141 EXPORT_SYMBOL(tcf_em_register);
142
143 /**
144 * tcf_em_unregister - unregister and extended match
145 *
146 * @ops: ematch operations lookup table
147 *
148 * This function must be called by ematches to announce their disappearance
149 * for examples when the module gets unloaded. The @ops parameter must be
150 * the same as the one used for registration.
151 *
152 * Returns -ENOENT if no matching ematch was found.
153 */
154 void tcf_em_unregister(struct tcf_ematch_ops *ops)
155 {
156 write_lock(&ematch_mod_lock);
157 list_del(&ops->link);
158 write_unlock(&ematch_mod_lock);
159 }
160 EXPORT_SYMBOL(tcf_em_unregister);
161
162 static inline struct tcf_ematch *tcf_em_get_match(struct tcf_ematch_tree *tree,
163 int index)
164 {
165 return &tree->matches[index];
166 }
167
168
169 static int tcf_em_validate(struct tcf_proto *tp,
170 struct tcf_ematch_tree_hdr *tree_hdr,
171 struct tcf_ematch *em, struct nlattr *nla, int idx)
172 {
173 int err = -EINVAL;
174 struct tcf_ematch_hdr *em_hdr = nla_data(nla);
175 int data_len = nla_len(nla) - sizeof(*em_hdr);
176 void *data = (void *) em_hdr + sizeof(*em_hdr);
177 struct net *net = tp->chain->block->net;
178
179 if (!TCF_EM_REL_VALID(em_hdr->flags))
180 goto errout;
181
182 if (em_hdr->kind == TCF_EM_CONTAINER) {
183 /* Special ematch called "container", carries an index
184 * referencing an external ematch sequence.
185 */
186 u32 ref;
187
188 if (data_len < sizeof(ref))
189 goto errout;
190 ref = *(u32 *) data;
191
192 if (ref >= tree_hdr->nmatches)
193 goto errout;
194
195 /* We do not allow backward jumps to avoid loops and jumps
196 * to our own position are of course illegal.
197 */
198 if (ref <= idx)
199 goto errout;
200
201
202 em->data = ref;
203 } else {
204 /* Note: This lookup will increase the module refcnt
205 * of the ematch module referenced. In case of a failure,
206 * a destroy function is called by the underlying layer
207 * which automatically releases the reference again, therefore
208 * the module MUST not be given back under any circumstances
209 * here. Be aware, the destroy function assumes that the
210 * module is held if the ops field is non zero.
211 */
212 em->ops = tcf_em_lookup(em_hdr->kind);
213
214 if (em->ops == NULL) {
215 err = -ENOENT;
216 #ifdef CONFIG_MODULES
217 __rtnl_unlock();
218 request_module("ematch-kind-%u", em_hdr->kind);
219 rtnl_lock();
220 em->ops = tcf_em_lookup(em_hdr->kind);
221 if (em->ops) {
222 /* We dropped the RTNL mutex in order to
223 * perform the module load. Tell the caller
224 * to replay the request.
225 */
226 module_put(em->ops->owner);
227 em->ops = NULL;
228 err = -EAGAIN;
229 }
230 #endif
231 goto errout;
232 }
233
234 /* ematch module provides expected length of data, so we
235 * can do a basic sanity check.
236 */
237 if (em->ops->datalen && data_len < em->ops->datalen)
238 goto errout;
239
240 if (em->ops->change) {
241 err = -EINVAL;
242 if (em_hdr->flags & TCF_EM_SIMPLE)
243 goto errout;
244 err = em->ops->change(net, data, data_len, em);
245 if (err < 0)
246 goto errout;
247 } else if (data_len > 0) {
248 /* ematch module doesn't provide an own change
249 * procedure and expects us to allocate and copy
250 * the ematch data.
251 *
252 * TCF_EM_SIMPLE may be specified stating that the
253 * data only consists of a u32 integer and the module
254 * does not expected a memory reference but rather
255 * the value carried.
256 */
257 if (em_hdr->flags & TCF_EM_SIMPLE) {
258 if (em->ops->datalen > 0)
259 goto errout;
260 if (data_len < sizeof(u32))
261 goto errout;
262 em->data = *(u32 *) data;
263 } else {
264 void *v = kmemdup(data, data_len, GFP_KERNEL);
265 if (v == NULL) {
266 err = -ENOBUFS;
267 goto errout;
268 }
269 em->data = (unsigned long) v;
270 }
271 em->datalen = data_len;
272 }
273 }
274
275 em->matchid = em_hdr->matchid;
276 em->flags = em_hdr->flags;
277 em->net = net;
278
279 err = 0;
280 errout:
281 return err;
282 }
283
284 static const struct nla_policy em_policy[TCA_EMATCH_TREE_MAX + 1] = {
285 [TCA_EMATCH_TREE_HDR] = { .len = sizeof(struct tcf_ematch_tree_hdr) },
286 [TCA_EMATCH_TREE_LIST] = { .type = NLA_NESTED },
287 };
288
289 /**
290 * tcf_em_tree_validate - validate ematch config TLV and build ematch tree
291 *
292 * @tp: classifier kind handle
293 * @nla: ematch tree configuration TLV
294 * @tree: destination ematch tree variable to store the resulting
295 * ematch tree.
296 *
297 * This function validates the given configuration TLV @nla and builds an
298 * ematch tree in @tree. The resulting tree must later be copied into
299 * the private classifier data using tcf_em_tree_change(). You MUST NOT
300 * provide the ematch tree variable of the private classifier data directly,
301 * the changes would not be locked properly.
302 *
303 * Returns a negative error code if the configuration TLV contains errors.
304 */
305 int tcf_em_tree_validate(struct tcf_proto *tp, struct nlattr *nla,
306 struct tcf_ematch_tree *tree)
307 {
308 int idx, list_len, matches_len, err;
309 struct nlattr *tb[TCA_EMATCH_TREE_MAX + 1];
310 struct nlattr *rt_match, *rt_hdr, *rt_list;
311 struct tcf_ematch_tree_hdr *tree_hdr;
312 struct tcf_ematch *em;
313
314 memset(tree, 0, sizeof(*tree));
315 if (!nla)
316 return 0;
317
318 err = nla_parse_nested_deprecated(tb, TCA_EMATCH_TREE_MAX, nla,
319 em_policy, NULL);
320 if (err < 0)
321 goto errout;
322
323 err = -EINVAL;
324 rt_hdr = tb[TCA_EMATCH_TREE_HDR];
325 rt_list = tb[TCA_EMATCH_TREE_LIST];
326
327 if (rt_hdr == NULL || rt_list == NULL)
328 goto errout;
329
330 tree_hdr = nla_data(rt_hdr);
331 memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr));
332
333 rt_match = nla_data(rt_list);
334 list_len = nla_len(rt_list);
335 matches_len = tree_hdr->nmatches * sizeof(*em);
336
337 tree->matches = kzalloc(matches_len, GFP_KERNEL);
338 if (tree->matches == NULL)
339 goto errout;
340
341 /* We do not use nla_parse_nested here because the maximum
342 * number of attributes is unknown. This saves us the allocation
343 * for a tb buffer which would serve no purpose at all.
344 *
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.
349 */
350 for (idx = 0; nla_ok(rt_match, list_len); idx++) {
351 err = -EINVAL;
352
353 if (rt_match->nla_type != (idx + 1))
354 goto errout_abort;
355
356 if (idx >= tree_hdr->nmatches)
357 goto errout_abort;
358
359 if (nla_len(rt_match) < sizeof(struct tcf_ematch_hdr))
360 goto errout_abort;
361
362 em = tcf_em_get_match(tree, idx);
363
364 err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx);
365 if (err < 0)
366 goto errout_abort;
367
368 rt_match = nla_next(rt_match, &list_len);
369 }
370
371 /* Check if the number of matches provided by userspace actually
372 * complies with the array of matches. The number was used for
373 * the validation of references and a mismatch could lead to
374 * undefined references during the matching process.
375 */
376 if (idx != tree_hdr->nmatches) {
377 err = -EINVAL;
378 goto errout_abort;
379 }
380
381 err = 0;
382 errout:
383 return err;
384
385 errout_abort:
386 tcf_em_tree_destroy(tree);
387 return err;
388 }
389 EXPORT_SYMBOL(tcf_em_tree_validate);
390
391 /**
392 * tcf_em_tree_destroy - destroy an ematch tree
393 *
394 * @tree: ematch tree to be deleted
395 *
396 * This functions destroys an ematch tree previously created by
397 * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that
398 * the ematch tree is not in use before calling this function.
399 */
400 void tcf_em_tree_destroy(struct tcf_ematch_tree *tree)
401 {
402 int i;
403
404 if (tree->matches == NULL)
405 return;
406
407 for (i = 0; i < tree->hdr.nmatches; i++) {
408 struct tcf_ematch *em = tcf_em_get_match(tree, i);
409
410 if (em->ops) {
411 if (em->ops->destroy)
412 em->ops->destroy(em);
413 else if (!tcf_em_is_simple(em))
414 kfree((void *) em->data);
415 module_put(em->ops->owner);
416 }
417 }
418
419 tree->hdr.nmatches = 0;
420 kfree(tree->matches);
421 tree->matches = NULL;
422 }
423 EXPORT_SYMBOL(tcf_em_tree_destroy);
424
425 /**
426 * tcf_em_tree_dump - dump ematch tree into a rtnl message
427 *
428 * @skb: skb holding the rtnl message
429 * @tree: ematch tree to be dumped
430 * @tlv: TLV type to be used to encapsulate the tree
431 *
432 * This function dumps a ematch tree into a rtnl message. It is valid to
433 * call this function while the ematch tree is in use.
434 *
435 * Returns -1 if the skb tailroom is insufficient.
436 */
437 int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv)
438 {
439 int i;
440 u8 *tail;
441 struct nlattr *top_start;
442 struct nlattr *list_start;
443
444 top_start = nla_nest_start_noflag(skb, tlv);
445 if (top_start == NULL)
446 goto nla_put_failure;
447
448 if (nla_put(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr))
449 goto nla_put_failure;
450
451 list_start = nla_nest_start_noflag(skb, TCA_EMATCH_TREE_LIST);
452 if (list_start == NULL)
453 goto nla_put_failure;
454
455 tail = skb_tail_pointer(skb);
456 for (i = 0; i < tree->hdr.nmatches; i++) {
457 struct nlattr *match_start = (struct nlattr *)tail;
458 struct tcf_ematch *em = tcf_em_get_match(tree, i);
459 struct tcf_ematch_hdr em_hdr = {
460 .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER,
461 .matchid = em->matchid,
462 .flags = em->flags
463 };
464
465 if (nla_put(skb, i + 1, sizeof(em_hdr), &em_hdr))
466 goto nla_put_failure;
467
468 if (em->ops && em->ops->dump) {
469 if (em->ops->dump(skb, em) < 0)
470 goto nla_put_failure;
471 } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) {
472 u32 u = em->data;
473 nla_put_nohdr(skb, sizeof(u), &u);
474 } else if (em->datalen > 0)
475 nla_put_nohdr(skb, em->datalen, (void *) em->data);
476
477 tail = skb_tail_pointer(skb);
478 match_start->nla_len = tail - (u8 *)match_start;
479 }
480
481 nla_nest_end(skb, list_start);
482 nla_nest_end(skb, top_start);
483
484 return 0;
485
486 nla_put_failure:
487 return -1;
488 }
489 EXPORT_SYMBOL(tcf_em_tree_dump);
490
491 static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em,
492 struct tcf_pkt_info *info)
493 {
494 int r = em->ops->match(skb, em, info);
495
496 return tcf_em_is_inverted(em) ? !r : r;
497 }
498
499 /* Do not use this function directly, use tcf_em_tree_match instead */
500 int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree,
501 struct tcf_pkt_info *info)
502 {
503 int stackp = 0, match_idx = 0, res = 0;
504 struct tcf_ematch *cur_match;
505 int stack[CONFIG_NET_EMATCH_STACK];
506
507 proceed:
508 while (match_idx < tree->hdr.nmatches) {
509 cur_match = tcf_em_get_match(tree, match_idx);
510
511 if (tcf_em_is_container(cur_match)) {
512 if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK))
513 goto stack_overflow;
514
515 stack[stackp++] = match_idx;
516 match_idx = cur_match->data;
517 goto proceed;
518 }
519
520 res = tcf_em_match(skb, cur_match, info);
521
522 if (tcf_em_early_end(cur_match, res))
523 break;
524
525 match_idx++;
526 }
527
528 pop_stack:
529 if (stackp > 0) {
530 match_idx = stack[--stackp];
531 cur_match = tcf_em_get_match(tree, match_idx);
532
533 if (tcf_em_is_inverted(cur_match))
534 res = !res;
535
536 if (tcf_em_early_end(cur_match, res)) {
537 goto pop_stack;
538 } else {
539 match_idx++;
540 goto proceed;
541 }
542 }
543
544 return res;
545
546 stack_overflow:
547 net_warn_ratelimited("tc ematch: local stack overflow, increase NET_EMATCH_STACK\n");
548 return -1;
549 }
550 EXPORT_SYMBOL(__tcf_em_tree_match);
551
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