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 * 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/slab.h> 86#include <linux/types.h> 87#include <linux/kernel.h> 88#include <linux/errno.h> 89#include <linux/rtnetlink.h> 90#include <linux/skbuff.h> 91#include <net/pkt_cls.h> 92 93static LIST_HEAD(ematch_ops); 94static DEFINE_RWLOCK(ematch_mod_lock); 95 96static inline struct tcf_ematch_ops * tcf_em_lookup(u16 kind) 97{ 98 struct tcf_ematch_ops *e = NULL; 99 100 read_lock(&ematch_mod_lock); 101 list_for_each_entry(e, &ematch_ops, link) { 102 if (kind == e->kind) { 103 if (!try_module_get(e->owner)) 104 e = NULL; 105 read_unlock(&ematch_mod_lock); 106 return e; 107 } 108 } 109 read_unlock(&ematch_mod_lock); 110 111 return NULL; 112} 113 114/** 115 * tcf_em_register - register an extended match 116 * 117 * @ops: ematch operations lookup table 118 * 119 * This function must be called by ematches to announce their presence. 120 * The given @ops must have kind set to a unique identifier and the 121 * callback match() must be implemented. All other callbacks are optional 122 * and a fallback implementation is used instead. 123 * 124 * Returns -EEXISTS if an ematch of the same kind has already registered. 125 */ 126int tcf_em_register(struct tcf_ematch_ops *ops) 127{ 128 int err = -EEXIST; 129 struct tcf_ematch_ops *e; 130 131 if (ops->match == NULL) 132 return -EINVAL; 133 134 write_lock(&ematch_mod_lock); 135 list_for_each_entry(e, &ematch_ops, link) 136 if (ops->kind == e->kind) 137 goto errout; 138 139 list_add_tail(&ops->link, &ematch_ops); 140 err = 0; 141errout: 142 write_unlock(&ematch_mod_lock); 143 return err; 144} 145EXPORT_SYMBOL(tcf_em_register); 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 */ 158void tcf_em_unregister(struct tcf_ematch_ops *ops) 159{ 160 write_lock(&ematch_mod_lock); 161 list_del(&ops->link); 162 write_unlock(&ematch_mod_lock); 163} 164EXPORT_SYMBOL(tcf_em_unregister); 165 166static inline struct tcf_ematch * tcf_em_get_match(struct tcf_ematch_tree *tree, 167 int index) 168{ 169 return &tree->matches[index]; 170} 171 172 173static int tcf_em_validate(struct tcf_proto *tp, 174 struct tcf_ematch_tree_hdr *tree_hdr, 175 struct tcf_ematch *em, struct nlattr *nla, int idx) 176{ 177 int err = -EINVAL; 178 struct tcf_ematch_hdr *em_hdr = nla_data(nla); 179 int data_len = nla_len(nla) - sizeof(*em_hdr); 180 void *data = (void *) em_hdr + sizeof(*em_hdr); 181 182 if (!TCF_EM_REL_VALID(em_hdr->flags)) 183 goto errout; 184 185 if (em_hdr->kind == TCF_EM_CONTAINER) { 186 /* Special ematch called "container", carries an index 187 * referencing an external ematch sequence. */ 188 u32 ref; 189 190 if (data_len < sizeof(ref)) 191 goto errout; 192 ref = *(u32 *) data; 193 194 if (ref >= tree_hdr->nmatches) 195 goto errout; 196 197 /* We do not allow backward jumps to avoid loops and jumps 198 * to our own position are of course illegal. */ 199 if (ref <= idx) 200 goto errout; 201 202 203 em->data = ref; 204 } else { 205 /* Note: This lookup will increase the module refcnt 206 * of the ematch module referenced. In case of a failure, 207 * a destroy function is called by the underlying layer 208 * which automatically releases the reference again, therefore 209 * the module MUST not be given back under any circumstances 210 * here. Be aware, the destroy function assumes that the 211 * module is held if the ops field is non zero. */ 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 module_put(em->ops->owner); 226 err = -EAGAIN; 227 } 228#endif 229 goto errout; 230 } 231 232 /* ematch module provides expected length of data, so we 233 * can do a basic sanity check. */ 234 if (em->ops->datalen && data_len < em->ops->datalen) 235 goto errout; 236 237 if (em->ops->change) { 238 err = em->ops->change(tp, data, data_len, em); 239 if (err < 0) 240 goto errout; 241 } else if (data_len > 0) { 242 /* ematch module doesn't provide an own change 243 * procedure and expects us to allocate and copy 244 * the ematch data. 245 * 246 * TCF_EM_SIMPLE may be specified stating that the 247 * data only consists of a u32 integer and the module 248 * does not expected a memory reference but rather 249 * the value carried. */ 250 if (em_hdr->flags & TCF_EM_SIMPLE) { 251 if (data_len < sizeof(u32)) 252 goto errout; 253 em->data = *(u32 *) data; 254 } else { 255 void *v = kmemdup(data, data_len, GFP_KERNEL); 256 if (v == NULL) { 257 err = -ENOBUFS; 258 goto errout; 259 } 260 em->data = (unsigned long) v; 261 } 262 } 263 } 264 265 em->matchid = em_hdr->matchid; 266 em->flags = em_hdr->flags; 267 em->datalen = data_len; 268 269 err = 0; 270errout: 271 return err; 272} 273 274static const struct nla_policy em_policy[TCA_EMATCH_TREE_MAX + 1] = { 275 [TCA_EMATCH_TREE_HDR] = { .len = sizeof(struct tcf_ematch_tree_hdr) }, 276 [TCA_EMATCH_TREE_LIST] = { .type = NLA_NESTED }, 277}; 278 279/** 280 * tcf_em_tree_validate - validate ematch config TLV and build ematch tree 281 * 282 * @tp: classifier kind handle 283 * @nla: ematch tree configuration TLV 284 * @tree: destination ematch tree variable to store the resulting 285 * ematch tree. 286 * 287 * This function validates the given configuration TLV @nla and builds an 288 * ematch tree in @tree. The resulting tree must later be copied into 289 * the private classifier data using tcf_em_tree_change(). You MUST NOT 290 * provide the ematch tree variable of the private classifier data directly, 291 * the changes would not be locked properly. 292 * 293 * Returns a negative error code if the configuration TLV contains errors. 294 */ 295int tcf_em_tree_validate(struct tcf_proto *tp, struct nlattr *nla, 296 struct tcf_ematch_tree *tree) 297{ 298 int idx, list_len, matches_len, err; 299 struct nlattr *tb[TCA_EMATCH_TREE_MAX + 1]; 300 struct nlattr *rt_match, *rt_hdr, *rt_list; 301 struct tcf_ematch_tree_hdr *tree_hdr; 302 struct tcf_ematch *em; 303 304 memset(tree, 0, sizeof(*tree)); 305 if (!nla) 306 return 0; 307 308 err = nla_parse_nested(tb, TCA_EMATCH_TREE_MAX, nla, em_policy); 309 if (err < 0) 310 goto errout; 311 312 err = -EINVAL; 313 rt_hdr = tb[TCA_EMATCH_TREE_HDR]; 314 rt_list = tb[TCA_EMATCH_TREE_LIST]; 315 316 if (rt_hdr == NULL || rt_list == NULL) 317 goto errout; 318 319 tree_hdr = nla_data(rt_hdr); 320 memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); 321 322 rt_match = nla_data(rt_list); 323 list_len = nla_len(rt_list); 324 matches_len = tree_hdr->nmatches * sizeof(*em); 325 326 tree->matches = kzalloc(matches_len, GFP_KERNEL); 327 if (tree->matches == NULL) 328 goto errout; 329 330 /* We do not use nla_parse_nested here because the maximum 331 * number of attributes is unknown. This saves us the allocation 332 * for a tb buffer which would serve no purpose at all. 333 * 334 * The array of rt attributes is parsed in the order as they are 335 * provided, their type must be incremental from 1 to n. Even 336 * if it does not serve any real purpose, a failure of sticking 337 * to this policy will result in parsing failure. */ 338 for (idx = 0; nla_ok(rt_match, list_len); idx++) { 339 err = -EINVAL; 340 341 if (rt_match->nla_type != (idx + 1)) 342 goto errout_abort; 343 344 if (idx >= tree_hdr->nmatches) 345 goto errout_abort; 346 347 if (nla_len(rt_match) < sizeof(struct tcf_ematch_hdr)) 348 goto errout_abort; 349 350 em = tcf_em_get_match(tree, idx); 351 352 err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx); 353 if (err < 0) 354 goto errout_abort; 355 356 rt_match = nla_next(rt_match, &list_len); 357 } 358 359 /* Check if the number of matches provided by userspace actually 360 * complies with the array of matches. The number was used for 361 * the validation of references and a mismatch could lead to 362 * undefined references during the matching process. */ 363 if (idx != tree_hdr->nmatches) { 364 err = -EINVAL; 365 goto errout_abort; 366 } 367 368 err = 0; 369errout: 370 return err; 371 372errout_abort: 373 tcf_em_tree_destroy(tp, tree); 374 return err; 375} 376EXPORT_SYMBOL(tcf_em_tree_validate); 377 378/** 379 * tcf_em_tree_destroy - destroy an ematch tree 380 * 381 * @tp: classifier kind handle 382 * @tree: ematch tree to be deleted 383 * 384 * This functions destroys an ematch tree previously created by 385 * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that 386 * the ematch tree is not in use before calling this function. 387 */ 388void tcf_em_tree_destroy(struct tcf_proto *tp, struct tcf_ematch_tree *tree) 389{ 390 int i; 391 392 if (tree->matches == NULL) 393 return; 394 395 for (i = 0; i < tree->hdr.nmatches; i++) { 396 struct tcf_ematch *em = tcf_em_get_match(tree, i); 397 398 if (em->ops) { 399 if (em->ops->destroy) 400 em->ops->destroy(tp, em); 401 else if (!tcf_em_is_simple(em)) 402 kfree((void *) em->data); 403 module_put(em->ops->owner); 404 } 405 } 406 407 tree->hdr.nmatches = 0; 408 kfree(tree->matches); 409 tree->matches = NULL; 410} 411EXPORT_SYMBOL(tcf_em_tree_destroy); 412 413/** 414 * tcf_em_tree_dump - dump ematch tree into a rtnl message 415 * 416 * @skb: skb holding the rtnl message 417 * @t: ematch tree to be dumped 418 * @tlv: TLV type to be used to encapsulate the tree 419 * 420 * This function dumps a ematch tree into a rtnl message. It is valid to 421 * call this function while the ematch tree is in use. 422 * 423 * Returns -1 if the skb tailroom is insufficient. 424 */ 425int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) 426{ 427 int i; 428 u8 *tail; 429 struct nlattr *top_start; 430 struct nlattr *list_start; 431 432 top_start = nla_nest_start(skb, tlv); 433 if (top_start == NULL) 434 goto nla_put_failure; 435 436 NLA_PUT(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr); 437 438 list_start = nla_nest_start(skb, TCA_EMATCH_TREE_LIST); 439 if (list_start == NULL) 440 goto nla_put_failure; 441 442 tail = skb_tail_pointer(skb); 443 for (i = 0; i < tree->hdr.nmatches; i++) { 444 struct nlattr *match_start = (struct nlattr *)tail; 445 struct tcf_ematch *em = tcf_em_get_match(tree, i); 446 struct tcf_ematch_hdr em_hdr = { 447 .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, 448 .matchid = em->matchid, 449 .flags = em->flags 450 }; 451 452 NLA_PUT(skb, i+1, sizeof(em_hdr), &em_hdr); 453 454 if (em->ops && em->ops->dump) { 455 if (em->ops->dump(skb, em) < 0) 456 goto nla_put_failure; 457 } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { 458 u32 u = em->data; 459 nla_put_nohdr(skb, sizeof(u), &u); 460 } else if (em->datalen > 0) 461 nla_put_nohdr(skb, em->datalen, (void *) em->data); 462 463 tail = skb_tail_pointer(skb); 464 match_start->nla_len = tail - (u8 *)match_start; 465 } 466 467 nla_nest_end(skb, list_start); 468 nla_nest_end(skb, top_start); 469 470 return 0; 471 472nla_put_failure: 473 return -1; 474} 475EXPORT_SYMBOL(tcf_em_tree_dump); 476 477static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, 478 struct tcf_pkt_info *info) 479{ 480 int r = em->ops->match(skb, em, info); 481 return tcf_em_is_inverted(em) ? !r : r; 482} 483 484/* Do not use this function directly, use tcf_em_tree_match instead */ 485int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, 486 struct tcf_pkt_info *info) 487{ 488 int stackp = 0, match_idx = 0, res = 0; 489 struct tcf_ematch *cur_match; 490 int stack[CONFIG_NET_EMATCH_STACK]; 491 492proceed: 493 while (match_idx < tree->hdr.nmatches) { 494 cur_match = tcf_em_get_match(tree, match_idx); 495 496 if (tcf_em_is_container(cur_match)) { 497 if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) 498 goto stack_overflow; 499 500 stack[stackp++] = match_idx; 501 match_idx = cur_match->data; 502 goto proceed; 503 } 504 505 res = tcf_em_match(skb, cur_match, info); 506 507 if (tcf_em_early_end(cur_match, res)) 508 break; 509 510 match_idx++; 511 } 512 513pop_stack: 514 if (stackp > 0) { 515 match_idx = stack[--stackp]; 516 cur_match = tcf_em_get_match(tree, match_idx); 517 518 if (tcf_em_early_end(cur_match, res)) 519 goto pop_stack; 520 else { 521 match_idx++; 522 goto proceed; 523 } 524 } 525 526 return res; 527 528stack_overflow: 529 if (net_ratelimit()) 530 printk(KERN_WARNING "tc ematch: local stack overflow," 531 " increase NET_EMATCH_STACK\n"); 532 return -1; 533} 534EXPORT_SYMBOL(__tcf_em_tree_match); 535