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/module.h> 85 #include <linux/types.h> 86 #include <linux/kernel.h> 87 #include <linux/sched.h> 88 #include <linux/mm.h> 89 #include <linux/errno.h> 90 #include <linux/interrupt.h> 91 #include <linux/rtnetlink.h> 92 #include <linux/skbuff.h> 93 #include <net/pkt_cls.h> 94 95 static LIST_HEAD(ematch_ops); 96 static DEFINE_RWLOCK(ematch_mod_lock); 97 98 static inline struct tcf_ematch_ops * tcf_em_lookup(u16 kind) 99 { 100 struct tcf_ematch_ops *e = NULL; 101 102 read_lock(&ematch_mod_lock); 103 list_for_each_entry(e, &ematch_ops, link) { 104 if (kind == e->kind) { 105 if (!try_module_get(e->owner)) 106 e = NULL; 107 read_unlock(&ematch_mod_lock); 108 return e; 109 } 110 } 111 read_unlock(&ematch_mod_lock); 112 113 return NULL; 114 } 115 116 /** 117 * tcf_em_register - register an extended match 118 * 119 * @ops: ematch operations lookup table 120 * 121 * This function must be called by ematches to announce their presence. 122 * The given @ops must have kind set to a unique identifier and the 123 * callback match() must be implemented. All other callbacks are optional 124 * and a fallback implementation is used instead. 125 * 126 * Returns -EEXISTS if an ematch of the same kind has already registered. 127 */ 128 int tcf_em_register(struct tcf_ematch_ops *ops) 129 { 130 int err = -EEXIST; 131 struct tcf_ematch_ops *e; 132 133 if (ops->match == NULL) 134 return -EINVAL; 135 136 write_lock(&ematch_mod_lock); 137 list_for_each_entry(e, &ematch_ops, link) 138 if (ops->kind == e->kind) 139 goto errout; 140 141 list_add_tail(&ops->link, &ematch_ops); 142 err = 0; 143 errout: 144 write_unlock(&ematch_mod_lock); 145 return err; 146 } 147 148 /** 149 * tcf_em_unregister - unregster and extended match 150 * 151 * @ops: ematch operations lookup table 152 * 153 * This function must be called by ematches to announce their disappearance 154 * for examples when the module gets unloaded. The @ops parameter must be 155 * the same as the one used for registration. 156 * 157 * Returns -ENOENT if no matching ematch was found. 158 */ 159 int tcf_em_unregister(struct tcf_ematch_ops *ops) 160 { 161 int err = 0; 162 struct tcf_ematch_ops *e; 163 164 write_lock(&ematch_mod_lock); 165 list_for_each_entry(e, &ematch_ops, link) { 166 if (e == ops) { 167 list_del(&e->link); 168 goto out; 169 } 170 } 171 172 err = -ENOENT; 173 out: 174 write_unlock(&ematch_mod_lock); 175 return err; 176 } 177 178 static inline struct tcf_ematch * tcf_em_get_match(struct tcf_ematch_tree *tree, 179 int index) 180 { 181 return &tree->matches[index]; 182 } 183 184 185 static int tcf_em_validate(struct tcf_proto *tp, 186 struct tcf_ematch_tree_hdr *tree_hdr, 187 struct tcf_ematch *em, struct rtattr *rta, int idx) 188 { 189 int err = -EINVAL; 190 struct tcf_ematch_hdr *em_hdr = RTA_DATA(rta); 191 int data_len = RTA_PAYLOAD(rta) - sizeof(*em_hdr); 192 void *data = (void *) em_hdr + sizeof(*em_hdr); 193 194 if (!TCF_EM_REL_VALID(em_hdr->flags)) 195 goto errout; 196 197 if (em_hdr->kind == TCF_EM_CONTAINER) { 198 /* Special ematch called "container", carries an index 199 * referencing an external ematch sequence. */ 200 u32 ref; 201 202 if (data_len < sizeof(ref)) 203 goto errout; 204 ref = *(u32 *) data; 205 206 if (ref >= tree_hdr->nmatches) 207 goto errout; 208 209 /* We do not allow backward jumps to avoid loops and jumps 210 * to our own position are of course illegal. */ 211 if (ref <= idx) 212 goto errout; 213 214 215 em->data = ref; 216 } else { 217 /* Note: This lookup will increase the module refcnt 218 * of the ematch module referenced. In case of a failure, 219 * a destroy function is called by the underlying layer 220 * which automatically releases the reference again, therefore 221 * the module MUST not be given back under any circumstances 222 * here. Be aware, the destroy function assumes that the 223 * module is held if the ops field is non zero. */ 224 em->ops = tcf_em_lookup(em_hdr->kind); 225 226 if (em->ops == NULL) { 227 err = -ENOENT; 228 goto errout; 229 } 230 231 /* ematch module provides expected length of data, so we 232 * can do a basic sanity check. */ 233 if (em->ops->datalen && data_len < em->ops->datalen) 234 goto errout; 235 236 if (em->ops->change) { 237 err = em->ops->change(tp, data, data_len, em); 238 if (err < 0) 239 goto errout; 240 } else if (data_len > 0) { 241 /* ematch module doesn't provide an own change 242 * procedure and expects us to allocate and copy 243 * the ematch data. 244 * 245 * TCF_EM_SIMPLE may be specified stating that the 246 * data only consists of a u32 integer and the module 247 * does not expected a memory reference but rather 248 * the value carried. */ 249 if (em_hdr->flags & TCF_EM_SIMPLE) { 250 if (data_len < sizeof(u32)) 251 goto errout; 252 em->data = *(u32 *) data; 253 } else { 254 void *v = kmemdup(data, data_len, GFP_KERNEL); 255 if (v == NULL) { 256 err = -ENOBUFS; 257 goto errout; 258 } 259 em->data = (unsigned long) v; 260 } 261 } 262 } 263 264 em->matchid = em_hdr->matchid; 265 em->flags = em_hdr->flags; 266 em->datalen = data_len; 267 268 err = 0; 269 errout: 270 return err; 271 } 272 273 /** 274 * tcf_em_tree_validate - validate ematch config TLV and build ematch tree 275 * 276 * @tp: classifier kind handle 277 * @rta: ematch tree configuration TLV 278 * @tree: destination ematch tree variable to store the resulting 279 * ematch tree. 280 * 281 * This function validates the given configuration TLV @rta and builds an 282 * ematch tree in @tree. The resulting tree must later be copied into 283 * the private classifier data using tcf_em_tree_change(). You MUST NOT 284 * provide the ematch tree variable of the private classifier data directly, 285 * the changes would not be locked properly. 286 * 287 * Returns a negative error code if the configuration TLV contains errors. 288 */ 289 int tcf_em_tree_validate(struct tcf_proto *tp, struct rtattr *rta, 290 struct tcf_ematch_tree *tree) 291 { 292 int idx, list_len, matches_len, err = -EINVAL; 293 struct rtattr *tb[TCA_EMATCH_TREE_MAX]; 294 struct rtattr *rt_match, *rt_hdr, *rt_list; 295 struct tcf_ematch_tree_hdr *tree_hdr; 296 struct tcf_ematch *em; 297 298 if (!rta) { 299 memset(tree, 0, sizeof(*tree)); 300 return 0; 301 } 302 303 if (rtattr_parse_nested(tb, TCA_EMATCH_TREE_MAX, rta) < 0) 304 goto errout; 305 306 rt_hdr = tb[TCA_EMATCH_TREE_HDR-1]; 307 rt_list = tb[TCA_EMATCH_TREE_LIST-1]; 308 309 if (rt_hdr == NULL || rt_list == NULL) 310 goto errout; 311 312 if (RTA_PAYLOAD(rt_hdr) < sizeof(*tree_hdr) || 313 RTA_PAYLOAD(rt_list) < sizeof(*rt_match)) 314 goto errout; 315 316 tree_hdr = RTA_DATA(rt_hdr); 317 memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); 318 319 rt_match = RTA_DATA(rt_list); 320 list_len = RTA_PAYLOAD(rt_list); 321 matches_len = tree_hdr->nmatches * sizeof(*em); 322 323 tree->matches = kzalloc(matches_len, GFP_KERNEL); 324 if (tree->matches == NULL) 325 goto errout; 326 327 /* We do not use rtattr_parse_nested here because the maximum 328 * number of attributes is unknown. This saves us the allocation 329 * for a tb buffer which would serve no purpose at all. 330 * 331 * The array of rt attributes is parsed in the order as they are 332 * provided, their type must be incremental from 1 to n. Even 333 * if it does not serve any real purpose, a failure of sticking 334 * to this policy will result in parsing failure. */ 335 for (idx = 0; RTA_OK(rt_match, list_len); idx++) { 336 err = -EINVAL; 337 338 if (rt_match->rta_type != (idx + 1)) 339 goto errout_abort; 340 341 if (idx >= tree_hdr->nmatches) 342 goto errout_abort; 343 344 if (RTA_PAYLOAD(rt_match) < sizeof(struct tcf_ematch_hdr)) 345 goto errout_abort; 346 347 em = tcf_em_get_match(tree, idx); 348 349 err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx); 350 if (err < 0) 351 goto errout_abort; 352 353 rt_match = RTA_NEXT(rt_match, list_len); 354 } 355 356 /* Check if the number of matches provided by userspace actually 357 * complies with the array of matches. The number was used for 358 * the validation of references and a mismatch could lead to 359 * undefined references during the matching process. */ 360 if (idx != tree_hdr->nmatches) { 361 err = -EINVAL; 362 goto errout_abort; 363 } 364 365 err = 0; 366 errout: 367 return err; 368 369 errout_abort: 370 tcf_em_tree_destroy(tp, tree); 371 return err; 372 } 373 374 /** 375 * tcf_em_tree_destroy - destroy an ematch tree 376 * 377 * @tp: classifier kind handle 378 * @tree: ematch tree to be deleted 379 * 380 * This functions destroys an ematch tree previously created by 381 * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that 382 * the ematch tree is not in use before calling this function. 383 */ 384 void tcf_em_tree_destroy(struct tcf_proto *tp, struct tcf_ematch_tree *tree) 385 { 386 int i; 387 388 if (tree->matches == NULL) 389 return; 390 391 for (i = 0; i < tree->hdr.nmatches; i++) { 392 struct tcf_ematch *em = tcf_em_get_match(tree, i); 393 394 if (em->ops) { 395 if (em->ops->destroy) 396 em->ops->destroy(tp, em); 397 else if (!tcf_em_is_simple(em) && em->data) 398 kfree((void *) em->data); 399 module_put(em->ops->owner); 400 } 401 } 402 403 tree->hdr.nmatches = 0; 404 kfree(tree->matches); 405 } 406 407 /** 408 * tcf_em_tree_dump - dump ematch tree into a rtnl message 409 * 410 * @skb: skb holding the rtnl message 411 * @t: ematch tree to be dumped 412 * @tlv: TLV type to be used to encapsulate the tree 413 * 414 * This function dumps a ematch tree into a rtnl message. It is valid to 415 * call this function while the ematch tree is in use. 416 * 417 * Returns -1 if the skb tailroom is insufficient. 418 */ 419 int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) 420 { 421 int i; 422 struct rtattr * top_start = (struct rtattr*) skb->tail; 423 struct rtattr * list_start; 424 425 RTA_PUT(skb, tlv, 0, NULL); 426 RTA_PUT(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr); 427 428 list_start = (struct rtattr *) skb->tail; 429 RTA_PUT(skb, TCA_EMATCH_TREE_LIST, 0, NULL); 430 431 for (i = 0; i < tree->hdr.nmatches; i++) { 432 struct rtattr *match_start = (struct rtattr*) skb->tail; 433 struct tcf_ematch *em = tcf_em_get_match(tree, i); 434 struct tcf_ematch_hdr em_hdr = { 435 .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, 436 .matchid = em->matchid, 437 .flags = em->flags 438 }; 439 440 RTA_PUT(skb, i+1, sizeof(em_hdr), &em_hdr); 441 442 if (em->ops && em->ops->dump) { 443 if (em->ops->dump(skb, em) < 0) 444 goto rtattr_failure; 445 } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { 446 u32 u = em->data; 447 RTA_PUT_NOHDR(skb, sizeof(u), &u); 448 } else if (em->datalen > 0) 449 RTA_PUT_NOHDR(skb, em->datalen, (void *) em->data); 450 451 match_start->rta_len = skb->tail - (u8*) match_start; 452 } 453 454 list_start->rta_len = skb->tail - (u8 *) list_start; 455 top_start->rta_len = skb->tail - (u8 *) top_start; 456 457 return 0; 458 459 rtattr_failure: 460 return -1; 461 } 462 463 static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, 464 struct tcf_pkt_info *info) 465 { 466 int r = em->ops->match(skb, em, info); 467 return tcf_em_is_inverted(em) ? !r : r; 468 } 469 470 /* Do not use this function directly, use tcf_em_tree_match instead */ 471 int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, 472 struct tcf_pkt_info *info) 473 { 474 int stackp = 0, match_idx = 0, res = 0; 475 struct tcf_ematch *cur_match; 476 int stack[CONFIG_NET_EMATCH_STACK]; 477 478 proceed: 479 while (match_idx < tree->hdr.nmatches) { 480 cur_match = tcf_em_get_match(tree, match_idx); 481 482 if (tcf_em_is_container(cur_match)) { 483 if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) 484 goto stack_overflow; 485 486 stack[stackp++] = match_idx; 487 match_idx = cur_match->data; 488 goto proceed; 489 } 490 491 res = tcf_em_match(skb, cur_match, info); 492 493 if (tcf_em_early_end(cur_match, res)) 494 break; 495 496 match_idx++; 497 } 498 499 pop_stack: 500 if (stackp > 0) { 501 match_idx = stack[--stackp]; 502 cur_match = tcf_em_get_match(tree, match_idx); 503 504 if (tcf_em_early_end(cur_match, res)) 505 goto pop_stack; 506 else { 507 match_idx++; 508 goto proceed; 509 } 510 } 511 512 return res; 513 514 stack_overflow: 515 if (net_ratelimit()) 516 printk("Local stack overflow, increase NET_EMATCH_STACK\n"); 517 return -1; 518 } 519 520 EXPORT_SYMBOL(tcf_em_register); 521 EXPORT_SYMBOL(tcf_em_unregister); 522 EXPORT_SYMBOL(tcf_em_tree_validate); 523 EXPORT_SYMBOL(tcf_em_tree_destroy); 524 EXPORT_SYMBOL(tcf_em_tree_dump); 525 EXPORT_SYMBOL(__tcf_em_tree_match); 526