summaryrefslogtreecommitdiffstats
path: root/net/sched/ematch.c
blob: 0fd0768a17c6cc9ab5b627bbfd94bee9c03b9657 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
/*
 * net/sched/ematch.c		Extended Match API
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 * Authors:	Thomas Graf <tgraf@suug.ch>
 *
 * ==========================================================================
 *
 * An extended match (ematch) is a small classification tool not worth
 * writing a full classifier for. Ematches can be interconnected to form
 * a logic expression and get attached to classifiers to extend their
 * functionatlity.
 *
 * The userspace part transforms the logic expressions into an array
 * consisting of multiple sequences of interconnected ematches separated
 * by markers. Precedence is implemented by a special ematch kind
 * referencing a sequence beyond the marker of the current sequence
 * causing the current position in the sequence to be pushed onto a stack
 * to allow the current position to be overwritten by the position referenced
 * in the special ematch. Matching continues in the new sequence until a
 * marker is reached causing the position to be restored from the stack.
 *
 * Example:
 *          A AND (B1 OR B2) AND C AND D
 *
 *              ------->-PUSH-------
 *    -->--    /         -->--      \   -->--
 *   /     \  /         /     \      \ /     \
 * +-------+-------+-------+-------+-------+--------+
 * | A AND | B AND | C AND | D END | B1 OR | B2 END |
 * +-------+-------+-------+-------+-------+--------+
 *                    \                      /
 *                     --------<-POP---------
 *
 * where B is a virtual ematch referencing to sequence starting with B1.
 * 
 * ==========================================================================
 *
 * How to write an ematch in 60 seconds
 * ------------------------------------
 * 
 *   1) Provide a matcher function:
 *      static int my_match(struct sk_buff *skb, struct tcf_ematch *m,
 *                          struct tcf_pkt_info *info)
 *      {
 *      	struct mydata *d = (struct mydata *) m->data;
 *
 *      	if (...matching goes here...)
 *      		return 1;
 *      	else
 *      		return 0;
 *      }
 *
 *   2) Fill out a struct tcf_ematch_ops:
 *      static struct tcf_ematch_ops my_ops = {
 *      	.kind = unique id,
 *      	.datalen = sizeof(struct mydata),
 *      	.match = my_match,
 *      	.owner = THIS_MODULE,
 *      };
 *
 *   3) Register/Unregister your ematch:
 *      static int __init init_my_ematch(void)
 *      {
 *      	return tcf_em_register(&my_ops);
 *      }
 *
 *      static void __exit exit_my_ematch(void)
 *      {
 *      	return tcf_em_unregister(&my_ops);
 *      }
 *
 *      module_init(init_my_ematch);
 *      module_exit(exit_my_ematch);
 *
 *   4) By now you should have two more seconds left, barely enough to
 *      open up a beer to watch the compilation going.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/rtnetlink.h>
#include <linux/skbuff.h>
#include <net/pkt_cls.h>

static LIST_HEAD(ematch_ops);
static DEFINE_RWLOCK(ematch_mod_lock);

static inline struct tcf_ematch_ops * tcf_em_lookup(u16 kind)
{
	struct tcf_ematch_ops *e = NULL;

	read_lock(&ematch_mod_lock);
	list_for_each_entry(e, &ematch_ops, link) {
		if (kind == e->kind) {
			if (!try_module_get(e->owner))
				e = NULL;
			read_unlock(&ematch_mod_lock);
			return e;
		}
	}
	read_unlock(&ematch_mod_lock);

	return NULL;
}

/**
 * tcf_em_register - register an extended match
 * 
 * @ops: ematch operations lookup table
 *
 * This function must be called by ematches to announce their presence.
 * The given @ops must have kind set to a unique identifier and the
 * callback match() must be implemented. All other callbacks are optional
 * and a fallback implementation is used instead.
 *
 * Returns -EEXISTS if an ematch of the same kind has already registered.
 */
int tcf_em_register(struct tcf_ematch_ops *ops)
{
	int err = -EEXIST;
	struct tcf_ematch_ops *e;

	if (ops->match == NULL)
		return -EINVAL;

	write_lock(&ematch_mod_lock);
	list_for_each_entry(e, &ematch_ops, link)
		if (ops->kind == e->kind)
			goto errout;

	list_add_tail(&ops->link, &ematch_ops);
	err = 0;
errout:
	write_unlock(&ematch_mod_lock);
	return err;
}

/**
 * tcf_em_unregister - unregster and extended match
 *
 * @ops: ematch operations lookup table
 *
 * This function must be called by ematches to announce their disappearance
 * for examples when the module gets unloaded. The @ops parameter must be
 * the same as the one used for registration.
 *
 * Returns -ENOENT if no matching ematch was found.
 */
int tcf_em_unregister(struct tcf_ematch_ops *ops)
{
	int err = 0;
	struct tcf_ematch_ops *e;

	write_lock(&ematch_mod_lock);
	list_for_each_entry(e, &ematch_ops, link) {
		if (e == ops) {
			list_del(&e->link);
			goto out;
		}
	}

	err = -ENOENT;
out:
	write_unlock(&ematch_mod_lock);
	return err;
}

static inline struct tcf_ematch * tcf_em_get_match(struct tcf_ematch_tree *tree,
						   int index)
{
	return &tree->matches[index];
}


static int tcf_em_validate(struct tcf_proto *tp,
			   struct tcf_ematch_tree_hdr *tree_hdr,
			   struct tcf_ematch *em, struct rtattr *rta, int idx)
{
	int err = -EINVAL;
	struct tcf_ematch_hdr *em_hdr = RTA_DATA(rta);
	int data_len = RTA_PAYLOAD(rta) - sizeof(*em_hdr);
	void *data = (void *) em_hdr + sizeof(*em_hdr);

	if (!TCF_EM_REL_VALID(em_hdr->flags))
		goto errout;

	if (em_hdr->kind == TCF_EM_CONTAINER) {
		/* Special ematch called "container", carries an index
		 * referencing an external ematch sequence. */
		u32 ref;

		if (data_len < sizeof(ref))
			goto errout;
		ref = *(u32 *) data;

		if (ref >= tree_hdr->nmatches)
			goto errout;

		/* We do not allow backward jumps to avoid loops and jumps
		 * to our own position are of course illegal. */
		if (ref <= idx)
			goto errout;

		
		em->data = ref;
	} else {
		/* Note: This lookup will increase the module refcnt
		 * of the ematch module referenced. In case of a failure,
		 * a destroy function is called by the underlying layer
		 * which automatically releases the reference again, therefore
		 * the module MUST not be given back under any circumstances
		 * here. Be aware, the destroy function assumes that the
		 * module is held if the ops field is non zero. */
		em->ops = tcf_em_lookup(em_hdr->kind);

		if (em->ops == NULL) {
			err = -ENOENT;
			goto errout;
		}

		/* ematch module provides expected length of data, so we
		 * can do a basic sanity check. */
		if (em->ops->datalen && data_len < em->ops->datalen)
			goto errout;

		if (em->ops->change) {
			err = em->ops->change(tp, data, data_len, em);
			if (err < 0)
				goto errout;
		} else if (data_len > 0) {
			/* ematch module doesn't provide an own change
			 * procedure and expects us to allocate and copy
			 * the ematch data.
			 *
			 * TCF_EM_SIMPLE may be specified stating that the
			 * data only consists of a u32 integer and the module
			 * does not expected a memory reference but rather
			 * the value carried. */
			if (em_hdr->flags & TCF_EM_SIMPLE) {
				if (data_len < sizeof(u32))
					goto errout;
				em->data = *(u32 *) data;
			} else {
				void *v = kmalloc(data_len, GFP_KERNEL);
				if (v == NULL) {
					err = -ENOBUFS;
					goto errout;
				}
				memcpy(v, data, data_len);
				em->data = (unsigned long) v;
			}
		}
	}

	em->matchid = em_hdr->matchid;
	em->flags = em_hdr->flags;
	em->datalen = data_len;

	err = 0;
errout:
	return err;
}

/**
 * tcf_em_tree_validate - validate ematch config TLV and build ematch tree
 *
 * @tp: classifier kind handle
 * @rta: ematch tree configuration TLV
 * @tree: destination ematch tree variable to store the resulting
 *        ematch tree.
 *
 * This function validates the given configuration TLV @rta and builds an
 * ematch tree in @tree. The resulting tree must later be copied into
 * the private classifier data using tcf_em_tree_change(). You MUST NOT
 * provide the ematch tree variable of the private classifier data directly,
 * the changes would not be locked properly.
 *
 * Returns a negative error code if the configuration TLV contains errors.
 */
int tcf_em_tree_validate(struct tcf_proto *tp, struct rtattr *rta,
			 struct tcf_ematch_tree *tree)
{
	int idx, list_len, matches_len, err = -EINVAL;
	struct rtattr *tb[TCA_EMATCH_TREE_MAX];
	struct rtattr *rt_match, *rt_hdr, *rt_list;
	struct tcf_ematch_tree_hdr *tree_hdr;
	struct tcf_ematch *em;

	if (!rta) {
		memset(tree, 0, sizeof(*tree));
		return 0;
	}

	if (rtattr_parse_nested(tb, TCA_EMATCH_TREE_MAX, rta) < 0)
		goto errout;

	rt_hdr = tb[TCA_EMATCH_TREE_HDR-1];
	rt_list = tb[TCA_EMATCH_TREE_LIST-1];

	if (rt_hdr == NULL || rt_list == NULL)
		goto errout;

	if (RTA_PAYLOAD(rt_hdr) < sizeof(*tree_hdr) ||
	    RTA_PAYLOAD(rt_list) < sizeof(*rt_match))
		goto errout;

	tree_hdr = RTA_DATA(rt_hdr);
	memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr));

	rt_match = RTA_DATA(rt_list);
	list_len = RTA_PAYLOAD(rt_list);
	matches_len = tree_hdr->nmatches * sizeof(*em);

	tree->matches = kzalloc(matches_len, GFP_KERNEL);
	if (tree->matches == NULL)
		goto errout;

	/* We do not use rtattr_parse_nested here because the maximum
	 * number of attributes is unknown. This saves us the allocation
	 * for a tb buffer which would serve no purpose at all.
	 * 
	 * The array of rt attributes is parsed in the order as they are
	 * provided, their type must be incremental from 1 to n. Even
	 * if it does not serve any real purpose, a failure of sticking
	 * to this policy will result in parsing failure. */
	for (idx = 0; RTA_OK(rt_match, list_len); idx++) {
		err = -EINVAL;

		if (rt_match->rta_type != (idx + 1))
			goto errout_abort;

		if (idx >= tree_hdr->nmatches)
			goto errout_abort;

		if (RTA_PAYLOAD(rt_match) < sizeof(struct tcf_ematch_hdr))
			goto errout_abort;

		em = tcf_em_get_match(tree, idx);

		err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx);
		if (err < 0)
			goto errout_abort;

		rt_match = RTA_NEXT(rt_match, list_len);
	}

	/* Check if the number of matches provided by userspace actually
	 * complies with the array of matches. The number was used for
	 * the validation of references and a mismatch could lead to
	 * undefined references during the matching process. */
	if (idx != tree_hdr->nmatches) {
		err = -EINVAL;
		goto errout_abort;
	}

	err = 0;
errout:
	return err;

errout_abort:
	tcf_em_tree_destroy(tp, tree);
	return err;
}

/**
 * tcf_em_tree_destroy - destroy an ematch tree
 *
 * @tp: classifier kind handle
 * @tree: ematch tree to be deleted
 *
 * This functions destroys an ematch tree previously created by
 * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that
 * the ematch tree is not in use before calling this function.
 */
void tcf_em_tree_destroy(struct tcf_proto *tp, struct tcf_ematch_tree *tree)
{
	int i;

	if (tree->matches == NULL)
		return;

	for (i = 0; i < tree->hdr.nmatches; i++) {
		struct tcf_ematch *em = tcf_em_get_match(tree, i);

		if (em->ops) {
			if (em->ops->destroy)
				em->ops->destroy(tp, em);
			else if (!tcf_em_is_simple(em) && em->data)
				kfree((void *) em->data);
			module_put(em->ops->owner);
		}
	}
	
	tree->hdr.nmatches = 0;
	kfree(tree->matches);
}

/**
 * tcf_em_tree_dump - dump ematch tree into a rtnl message
 *
 * @skb: skb holding the rtnl message
 * @t: ematch tree to be dumped
 * @tlv: TLV type to be used to encapsulate the tree
 *
 * This function dumps a ematch tree into a rtnl message. It is valid to
 * call this function while the ematch tree is in use.
 *
 * Returns -1 if the skb tailroom is insufficient.
 */
int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv)
{
	int i;
	struct rtattr * top_start = (struct rtattr*) skb->tail;
	struct rtattr * list_start;

	RTA_PUT(skb, tlv, 0, NULL);
	RTA_PUT(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr);

	list_start = (struct rtattr *) skb->tail;
	RTA_PUT(skb, TCA_EMATCH_TREE_LIST, 0, NULL);

	for (i = 0; i < tree->hdr.nmatches; i++) {
		struct rtattr *match_start = (struct rtattr*) skb->tail;
		struct tcf_ematch *em = tcf_em_get_match(tree, i);
		struct tcf_ematch_hdr em_hdr = {
			.kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER,
			.matchid = em->matchid,
			.flags = em->flags
		};

		RTA_PUT(skb, i+1, sizeof(em_hdr), &em_hdr);

		if (em->ops && em->ops->dump) {
			if (em->ops->dump(skb, em) < 0)
				goto rtattr_failure;
		} else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) {
			u32 u = em->data;
			RTA_PUT_NOHDR(skb, sizeof(u), &u);
		} else if (em->datalen > 0)
			RTA_PUT_NOHDR(skb, em->datalen, (void *) em->data);

		match_start->rta_len = skb->tail - (u8*) match_start;
	}

	list_start->rta_len = skb->tail - (u8 *) list_start;
	top_start->rta_len = skb->tail - (u8 *) top_start;

	return 0;

rtattr_failure:
	return -1;
}

static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em,
			       struct tcf_pkt_info *info)
{
	int r = em->ops->match(skb, em, info);
	return tcf_em_is_inverted(em) ? !r : r;
}

/* Do not use this function directly, use tcf_em_tree_match instead */
int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree,
			struct tcf_pkt_info *info)
{
	int stackp = 0, match_idx = 0, res = 0;
	struct tcf_ematch *cur_match;
	int stack[CONFIG_NET_EMATCH_STACK];

proceed:
	while (match_idx < tree->hdr.nmatches) {
		cur_match = tcf_em_get_match(tree, match_idx);

		if (tcf_em_is_container(cur_match)) {
			if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK))
				goto stack_overflow;

			stack[stackp++] = match_idx;
			match_idx = cur_match->data;
			goto proceed;
		}

		res = tcf_em_match(skb, cur_match, info);

		if (tcf_em_early_end(cur_match, res))
			break;

		match_idx++;
	}

pop_stack:
	if (stackp > 0) {
		match_idx = stack[--stackp];
		cur_match = tcf_em_get_match(tree, match_idx);

		if (tcf_em_early_end(cur_match, res))
			goto pop_stack;
		else {
			match_idx++;
			goto proceed;
		}
	}

	return res;

stack_overflow:
	if (net_ratelimit())
		printk("Local stack overflow, increase NET_EMATCH_STACK\n");
	return -1;
}

EXPORT_SYMBOL(tcf_em_register);
EXPORT_SYMBOL(tcf_em_unregister);
EXPORT_SYMBOL(tcf_em_tree_validate);
EXPORT_SYMBOL(tcf_em_tree_destroy);
EXPORT_SYMBOL(tcf_em_tree_dump);
EXPORT_SYMBOL(__tcf_em_tree_match);
OpenPOWER on IntegriCloud