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/mm.h> 88#include <linux/errno.h> 89#include <linux/interrupt.h> 90#include <linux/rtnetlink.h> 91#include <linux/skbuff.h> 92#include <net/pkt_cls.h> 93 94static LIST_HEAD(ematch_ops); 95static DEFINE_RWLOCK(ematch_mod_lock); 96 97static inline struct tcf_ematch_ops * tcf_em_lookup(u16 kind) 98{ 99 struct tcf_ematch_ops *e = NULL; 100 101 read_lock(&ematch_mod_lock); 102 list_for_each_entry(e, &ematch_ops, link) { 103 if (kind == e->kind) { 104 if (!try_module_get(e->owner)) 105 e = NULL; 106 read_unlock(&ematch_mod_lock); 107 return e; 108 } 109 } 110 read_unlock(&ematch_mod_lock); 111 112 return NULL; 113} 114 115/** 116 * tcf_em_register - register an extended match 117 * 118 * @ops: ematch operations lookup table 119 * 120 * This function must be called by ematches to announce their presence. 121 * The given @ops must have kind set to a unique identifier and the 122 * callback match() must be implemented. All other callbacks are optional 123 * and a fallback implementation is used instead. 124 * 125 * Returns -EEXISTS if an ematch of the same kind has already registered. 126 */ 127int tcf_em_register(struct tcf_ematch_ops *ops) 128{ 129 int err = -EEXIST; 130 struct tcf_ematch_ops *e; 131 132 if (ops->match == NULL) 133 return -EINVAL; 134 135 write_lock(&ematch_mod_lock); 136 list_for_each_entry(e, &ematch_ops, link) 137 if (ops->kind == e->kind) 138 goto errout; 139 140 list_add_tail(&ops->link, &ematch_ops); 141 err = 0; 142errout: 143 write_unlock(&ematch_mod_lock); 144 return err; 145} 146 147/** 148 * tcf_em_unregister - unregster and extended match 149 * 150 * @ops: ematch operations lookup table 151 * 152 * This function must be called by ematches to announce their disappearance 153 * for examples when the module gets unloaded. The @ops parameter must be 154 * the same as the one used for registration. 155 * 156 * Returns -ENOENT if no matching ematch was found. 157 */ 158int tcf_em_unregister(struct tcf_ematch_ops *ops) 159{ 160 int err = 0; 161 struct tcf_ematch_ops *e; 162 163 write_lock(&ematch_mod_lock); 164 list_for_each_entry(e, &ematch_ops, link) { 165 if (e == ops) { 166 list_del(&e->link); 167 goto out; 168 } 169 } 170 171 err = -ENOENT; 172out: 173 write_unlock(&ematch_mod_lock); 174 return err; 175} 176 177static inline struct tcf_ematch * tcf_em_get_match(struct tcf_ematch_tree *tree, 178 int index) 179{ 180 return &tree->matches[index]; 181} 182 183 184static int tcf_em_validate(struct tcf_proto *tp, 185 struct tcf_ematch_tree_hdr *tree_hdr, 186 struct tcf_ematch *em, struct rtattr *rta, int idx) 187{ 188 int err = -EINVAL; 189 struct tcf_ematch_hdr *em_hdr = RTA_DATA(rta); 190 int data_len = RTA_PAYLOAD(rta) - sizeof(*em_hdr); 191 void *data = (void *) em_hdr + sizeof(*em_hdr); 192 193 if (!TCF_EM_REL_VALID(em_hdr->flags)) 194 goto errout; 195 196 if (em_hdr->kind == TCF_EM_CONTAINER) { 197 /* Special ematch called "container", carries an index 198 * referencing an external ematch sequence. */ 199 u32 ref; 200 201 if (data_len < sizeof(ref)) 202 goto errout; 203 ref = *(u32 *) data; 204 205 if (ref >= tree_hdr->nmatches) 206 goto errout; 207 208 /* We do not allow backward jumps to avoid loops and jumps 209 * to our own position are of course illegal. */ 210 if (ref <= idx) 211 goto errout; 212 213 214 em->data = ref; 215 } else { 216 /* Note: This lookup will increase the module refcnt 217 * of the ematch module referenced. In case of a failure, 218 * a destroy function is called by the underlying layer 219 * which automatically releases the reference again, therefore 220 * the module MUST not be given back under any circumstances 221 * here. Be aware, the destroy function assumes that the 222 * module is held if the ops field is non zero. */ 223 em->ops = tcf_em_lookup(em_hdr->kind); 224 225 if (em->ops == NULL) { 226 err = -ENOENT; 227 goto errout; 228 } 229 230 /* ematch module provides expected length of data, so we 231 * can do a basic sanity check. */ 232 if (em->ops->datalen && data_len < em->ops->datalen) 233 goto errout; 234 235 if (em->ops->change) { 236 err = em->ops->change(tp, data, data_len, em); 237 if (err < 0) 238 goto errout; 239 } else if (data_len > 0) { 240 /* ematch module doesn't provide an own change 241 * procedure and expects us to allocate and copy 242 * the ematch data. 243 * 244 * TCF_EM_SIMPLE may be specified stating that the 245 * data only consists of a u32 integer and the module 246 * does not expected a memory reference but rather 247 * the value carried. */ 248 if (em_hdr->flags & TCF_EM_SIMPLE) { 249 if (data_len < sizeof(u32)) 250 goto errout; 251 em->data = *(u32 *) data; 252 } else { 253 void *v = kmemdup(data, data_len, GFP_KERNEL); 254 if (v == NULL) { 255 err = -ENOBUFS; 256 goto errout; 257 } 258 em->data = (unsigned long) v; 259 } 260 } 261 } 262 263 em->matchid = em_hdr->matchid; 264 em->flags = em_hdr->flags; 265 em->datalen = data_len; 266 267 err = 0; 268errout: 269 return err; 270} 271 272/** 273 * tcf_em_tree_validate - validate ematch config TLV and build ematch tree 274 * 275 * @tp: classifier kind handle 276 * @rta: ematch tree configuration TLV 277 * @tree: destination ematch tree variable to store the resulting 278 * ematch tree. 279 * 280 * This function validates the given configuration TLV @rta and builds an 281 * ematch tree in @tree. The resulting tree must later be copied into 282 * the private classifier data using tcf_em_tree_change(). You MUST NOT 283 * provide the ematch tree variable of the private classifier data directly, 284 * the changes would not be locked properly. 285 * 286 * Returns a negative error code if the configuration TLV contains errors. 287 */ 288int tcf_em_tree_validate(struct tcf_proto *tp, struct rtattr *rta, 289 struct tcf_ematch_tree *tree) 290{ 291 int idx, list_len, matches_len, err = -EINVAL; 292 struct rtattr *tb[TCA_EMATCH_TREE_MAX]; 293 struct rtattr *rt_match, *rt_hdr, *rt_list; 294 struct tcf_ematch_tree_hdr *tree_hdr; 295 struct tcf_ematch *em; 296 297 if (!rta) { 298 memset(tree, 0, sizeof(*tree)); 299 return 0; 300 } 301 302 if (rtattr_parse_nested(tb, TCA_EMATCH_TREE_MAX, rta) < 0) 303 goto errout; 304 305 rt_hdr = tb[TCA_EMATCH_TREE_HDR-1]; 306 rt_list = tb[TCA_EMATCH_TREE_LIST-1]; 307 308 if (rt_hdr == NULL || rt_list == NULL) 309 goto errout; 310 311 if (RTA_PAYLOAD(rt_hdr) < sizeof(*tree_hdr) || 312 RTA_PAYLOAD(rt_list) < sizeof(*rt_match)) 313 goto errout; 314 315 tree_hdr = RTA_DATA(rt_hdr); 316 memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); 317 318 rt_match = RTA_DATA(rt_list); 319 list_len = RTA_PAYLOAD(rt_list); 320 matches_len = tree_hdr->nmatches * sizeof(*em); 321 322 tree->matches = kzalloc(matches_len, GFP_KERNEL); 323 if (tree->matches == NULL) 324 goto errout; 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; 365errout: 366 return err; 367 368errout_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 */ 383void 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 */ 418int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) 419{ 420 int i; 421 u8 *tail; 422 struct rtattr *top_start = (struct rtattr *)skb_tail_pointer(skb); 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_pointer(skb); 429 RTA_PUT(skb, TCA_EMATCH_TREE_LIST, 0, NULL); 430 431 tail = skb_tail_pointer(skb); 432 for (i = 0; i < tree->hdr.nmatches; i++) { 433 struct rtattr *match_start = (struct rtattr *)tail; 434 struct tcf_ematch *em = tcf_em_get_match(tree, i); 435 struct tcf_ematch_hdr em_hdr = { 436 .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, 437 .matchid = em->matchid, 438 .flags = em->flags 439 }; 440 441 RTA_PUT(skb, i+1, sizeof(em_hdr), &em_hdr); 442 443 if (em->ops && em->ops->dump) { 444 if (em->ops->dump(skb, em) < 0) 445 goto rtattr_failure; 446 } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { 447 u32 u = em->data; 448 RTA_PUT_NOHDR(skb, sizeof(u), &u); 449 } else if (em->datalen > 0) 450 RTA_PUT_NOHDR(skb, em->datalen, (void *) em->data); 451 452 tail = skb_tail_pointer(skb); 453 match_start->rta_len = tail - (u8 *)match_start; 454 } 455 456 list_start->rta_len = tail - (u8 *)list_start; 457 top_start->rta_len = tail - (u8 *)top_start; 458 459 return 0; 460 461rtattr_failure: 462 return -1; 463} 464 465static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, 466 struct tcf_pkt_info *info) 467{ 468 int r = em->ops->match(skb, em, info); 469 return tcf_em_is_inverted(em) ? !r : r; 470} 471 472/* Do not use this function directly, use tcf_em_tree_match instead */ 473int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, 474 struct tcf_pkt_info *info) 475{ 476 int stackp = 0, match_idx = 0, res = 0; 477 struct tcf_ematch *cur_match; 478 int stack[CONFIG_NET_EMATCH_STACK]; 479 480proceed: 481 while (match_idx < tree->hdr.nmatches) { 482 cur_match = tcf_em_get_match(tree, match_idx); 483 484 if (tcf_em_is_container(cur_match)) { 485 if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) 486 goto stack_overflow; 487 488 stack[stackp++] = match_idx; 489 match_idx = cur_match->data; 490 goto proceed; 491 } 492 493 res = tcf_em_match(skb, cur_match, info); 494 495 if (tcf_em_early_end(cur_match, res)) 496 break; 497 498 match_idx++; 499 } 500 501pop_stack: 502 if (stackp > 0) { 503 match_idx = stack[--stackp]; 504 cur_match = tcf_em_get_match(tree, match_idx); 505 506 if (tcf_em_early_end(cur_match, res)) 507 goto pop_stack; 508 else { 509 match_idx++; 510 goto proceed; 511 } 512 } 513 514 return res; 515 516stack_overflow: 517 if (net_ratelimit()) 518 printk("Local stack overflow, increase NET_EMATCH_STACK\n"); 519 return -1; 520} 521 522EXPORT_SYMBOL(tcf_em_register); 523EXPORT_SYMBOL(tcf_em_unregister); 524EXPORT_SYMBOL(tcf_em_tree_validate); 525EXPORT_SYMBOL(tcf_em_tree_destroy); 526EXPORT_SYMBOL(tcf_em_tree_dump); 527EXPORT_SYMBOL(__tcf_em_tree_match); 528