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