Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame] | 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 | |
| 93 | static LIST_HEAD(ematch_ops); |
| 94 | static DEFINE_RWLOCK(ematch_mod_lock); |
| 95 | |
| 96 | static 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 | */ |
| 126 | int 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; |
| 141 | errout: |
| 142 | write_unlock(&ematch_mod_lock); |
| 143 | return err; |
| 144 | } |
| 145 | EXPORT_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 | */ |
| 158 | void 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 | } |
| 164 | EXPORT_SYMBOL(tcf_em_unregister); |
| 165 | |
| 166 | static 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 | |
| 173 | static 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 | struct net *net = dev_net(qdisc_dev(tp->q)); |
| 182 | |
| 183 | if (!TCF_EM_REL_VALID(em_hdr->flags)) |
| 184 | goto errout; |
| 185 | |
| 186 | if (em_hdr->kind == TCF_EM_CONTAINER) { |
| 187 | /* Special ematch called "container", carries an index |
| 188 | * referencing an external ematch sequence. |
| 189 | */ |
| 190 | u32 ref; |
| 191 | |
| 192 | if (data_len < sizeof(ref)) |
| 193 | goto errout; |
| 194 | ref = *(u32 *) data; |
| 195 | |
| 196 | if (ref >= tree_hdr->nmatches) |
| 197 | goto errout; |
| 198 | |
| 199 | /* We do not allow backward jumps to avoid loops and jumps |
| 200 | * to our own position are of course illegal. |
| 201 | */ |
| 202 | if (ref <= idx) |
| 203 | goto errout; |
| 204 | |
| 205 | |
| 206 | em->data = ref; |
| 207 | } else { |
| 208 | /* Note: This lookup will increase the module refcnt |
| 209 | * of the ematch module referenced. In case of a failure, |
| 210 | * a destroy function is called by the underlying layer |
| 211 | * which automatically releases the reference again, therefore |
| 212 | * the module MUST not be given back under any circumstances |
| 213 | * here. Be aware, the destroy function assumes that the |
| 214 | * module is held if the ops field is non zero. |
| 215 | */ |
| 216 | em->ops = tcf_em_lookup(em_hdr->kind); |
| 217 | |
| 218 | if (em->ops == NULL) { |
| 219 | err = -ENOENT; |
| 220 | #ifdef CONFIG_MODULES |
| 221 | __rtnl_unlock(); |
| 222 | request_module("ematch-kind-%u", em_hdr->kind); |
| 223 | rtnl_lock(); |
| 224 | em->ops = tcf_em_lookup(em_hdr->kind); |
| 225 | if (em->ops) { |
| 226 | /* We dropped the RTNL mutex in order to |
| 227 | * perform the module load. Tell the caller |
| 228 | * to replay the request. |
| 229 | */ |
| 230 | module_put(em->ops->owner); |
| 231 | em->ops = NULL; |
| 232 | err = -EAGAIN; |
| 233 | } |
| 234 | #endif |
| 235 | goto errout; |
| 236 | } |
| 237 | |
| 238 | /* ematch module provides expected length of data, so we |
| 239 | * can do a basic sanity check. |
| 240 | */ |
| 241 | if (em->ops->datalen && data_len < em->ops->datalen) |
| 242 | goto errout; |
| 243 | |
| 244 | if (em->ops->change) { |
| 245 | err = em->ops->change(net, data, data_len, em); |
| 246 | if (err < 0) |
| 247 | goto errout; |
| 248 | } else if (data_len > 0) { |
| 249 | /* ematch module doesn't provide an own change |
| 250 | * procedure and expects us to allocate and copy |
| 251 | * the ematch data. |
| 252 | * |
| 253 | * TCF_EM_SIMPLE may be specified stating that the |
| 254 | * data only consists of a u32 integer and the module |
| 255 | * does not expected a memory reference but rather |
| 256 | * the value carried. |
| 257 | */ |
| 258 | if (em_hdr->flags & TCF_EM_SIMPLE) { |
| 259 | if (data_len < sizeof(u32)) |
| 260 | goto errout; |
| 261 | em->data = *(u32 *) data; |
| 262 | } else { |
| 263 | void *v = kmemdup(data, data_len, GFP_KERNEL); |
| 264 | if (v == NULL) { |
| 265 | err = -ENOBUFS; |
| 266 | goto errout; |
| 267 | } |
| 268 | em->data = (unsigned long) v; |
| 269 | } |
| 270 | } |
| 271 | } |
| 272 | |
| 273 | em->matchid = em_hdr->matchid; |
| 274 | em->flags = em_hdr->flags; |
| 275 | em->datalen = data_len; |
| 276 | em->net = net; |
| 277 | |
| 278 | err = 0; |
| 279 | errout: |
| 280 | return err; |
| 281 | } |
| 282 | |
| 283 | static const struct nla_policy em_policy[TCA_EMATCH_TREE_MAX + 1] = { |
| 284 | [TCA_EMATCH_TREE_HDR] = { .len = sizeof(struct tcf_ematch_tree_hdr) }, |
| 285 | [TCA_EMATCH_TREE_LIST] = { .type = NLA_NESTED }, |
| 286 | }; |
| 287 | |
| 288 | /** |
| 289 | * tcf_em_tree_validate - validate ematch config TLV and build ematch tree |
| 290 | * |
| 291 | * @tp: classifier kind handle |
| 292 | * @nla: ematch tree configuration TLV |
| 293 | * @tree: destination ematch tree variable to store the resulting |
| 294 | * ematch tree. |
| 295 | * |
| 296 | * This function validates the given configuration TLV @nla and builds an |
| 297 | * ematch tree in @tree. The resulting tree must later be copied into |
| 298 | * the private classifier data using tcf_em_tree_change(). You MUST NOT |
| 299 | * provide the ematch tree variable of the private classifier data directly, |
| 300 | * the changes would not be locked properly. |
| 301 | * |
| 302 | * Returns a negative error code if the configuration TLV contains errors. |
| 303 | */ |
| 304 | int tcf_em_tree_validate(struct tcf_proto *tp, struct nlattr *nla, |
| 305 | struct tcf_ematch_tree *tree) |
| 306 | { |
| 307 | int idx, list_len, matches_len, err; |
| 308 | struct nlattr *tb[TCA_EMATCH_TREE_MAX + 1]; |
| 309 | struct nlattr *rt_match, *rt_hdr, *rt_list; |
| 310 | struct tcf_ematch_tree_hdr *tree_hdr; |
| 311 | struct tcf_ematch *em; |
| 312 | |
| 313 | memset(tree, 0, sizeof(*tree)); |
| 314 | if (!nla) |
| 315 | return 0; |
| 316 | |
| 317 | err = nla_parse_nested(tb, TCA_EMATCH_TREE_MAX, nla, em_policy); |
| 318 | if (err < 0) |
| 319 | goto errout; |
| 320 | |
| 321 | err = -EINVAL; |
| 322 | rt_hdr = tb[TCA_EMATCH_TREE_HDR]; |
| 323 | rt_list = tb[TCA_EMATCH_TREE_LIST]; |
| 324 | |
| 325 | if (rt_hdr == NULL || rt_list == NULL) |
| 326 | goto errout; |
| 327 | |
| 328 | tree_hdr = nla_data(rt_hdr); |
| 329 | memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); |
| 330 | |
| 331 | rt_match = nla_data(rt_list); |
| 332 | list_len = nla_len(rt_list); |
| 333 | matches_len = tree_hdr->nmatches * sizeof(*em); |
| 334 | |
| 335 | tree->matches = kzalloc(matches_len, GFP_KERNEL); |
| 336 | if (tree->matches == NULL) |
| 337 | goto errout; |
| 338 | |
| 339 | /* We do not use nla_parse_nested here because the maximum |
| 340 | * number of attributes is unknown. This saves us the allocation |
| 341 | * for a tb buffer which would serve no purpose at all. |
| 342 | * |
| 343 | * The array of rt attributes is parsed in the order as they are |
| 344 | * provided, their type must be incremental from 1 to n. Even |
| 345 | * if it does not serve any real purpose, a failure of sticking |
| 346 | * to this policy will result in parsing failure. |
| 347 | */ |
| 348 | for (idx = 0; nla_ok(rt_match, list_len); idx++) { |
| 349 | err = -EINVAL; |
| 350 | |
| 351 | if (rt_match->nla_type != (idx + 1)) |
| 352 | goto errout_abort; |
| 353 | |
| 354 | if (idx >= tree_hdr->nmatches) |
| 355 | goto errout_abort; |
| 356 | |
| 357 | if (nla_len(rt_match) < sizeof(struct tcf_ematch_hdr)) |
| 358 | goto errout_abort; |
| 359 | |
| 360 | em = tcf_em_get_match(tree, idx); |
| 361 | |
| 362 | err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx); |
| 363 | if (err < 0) |
| 364 | goto errout_abort; |
| 365 | |
| 366 | rt_match = nla_next(rt_match, &list_len); |
| 367 | } |
| 368 | |
| 369 | /* Check if the number of matches provided by userspace actually |
| 370 | * complies with the array of matches. The number was used for |
| 371 | * the validation of references and a mismatch could lead to |
| 372 | * undefined references during the matching process. |
| 373 | */ |
| 374 | if (idx != tree_hdr->nmatches) { |
| 375 | err = -EINVAL; |
| 376 | goto errout_abort; |
| 377 | } |
| 378 | |
| 379 | err = 0; |
| 380 | errout: |
| 381 | return err; |
| 382 | |
| 383 | errout_abort: |
| 384 | tcf_em_tree_destroy(tree); |
| 385 | return err; |
| 386 | } |
| 387 | EXPORT_SYMBOL(tcf_em_tree_validate); |
| 388 | |
| 389 | /** |
| 390 | * tcf_em_tree_destroy - destroy an ematch tree |
| 391 | * |
| 392 | * @tp: classifier kind handle |
| 393 | * @tree: ematch tree to be deleted |
| 394 | * |
| 395 | * This functions destroys an ematch tree previously created by |
| 396 | * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that |
| 397 | * the ematch tree is not in use before calling this function. |
| 398 | */ |
| 399 | void tcf_em_tree_destroy(struct tcf_ematch_tree *tree) |
| 400 | { |
| 401 | int i; |
| 402 | |
| 403 | if (tree->matches == NULL) |
| 404 | return; |
| 405 | |
| 406 | for (i = 0; i < tree->hdr.nmatches; i++) { |
| 407 | struct tcf_ematch *em = tcf_em_get_match(tree, i); |
| 408 | |
| 409 | if (em->ops) { |
| 410 | if (em->ops->destroy) |
| 411 | em->ops->destroy(em); |
| 412 | else if (!tcf_em_is_simple(em)) |
| 413 | kfree((void *) em->data); |
| 414 | module_put(em->ops->owner); |
| 415 | } |
| 416 | } |
| 417 | |
| 418 | tree->hdr.nmatches = 0; |
| 419 | kfree(tree->matches); |
| 420 | tree->matches = NULL; |
| 421 | } |
| 422 | EXPORT_SYMBOL(tcf_em_tree_destroy); |
| 423 | |
| 424 | /** |
| 425 | * tcf_em_tree_dump - dump ematch tree into a rtnl message |
| 426 | * |
| 427 | * @skb: skb holding the rtnl message |
| 428 | * @t: ematch tree to be dumped |
| 429 | * @tlv: TLV type to be used to encapsulate the tree |
| 430 | * |
| 431 | * This function dumps a ematch tree into a rtnl message. It is valid to |
| 432 | * call this function while the ematch tree is in use. |
| 433 | * |
| 434 | * Returns -1 if the skb tailroom is insufficient. |
| 435 | */ |
| 436 | int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) |
| 437 | { |
| 438 | int i; |
| 439 | u8 *tail; |
| 440 | struct nlattr *top_start; |
| 441 | struct nlattr *list_start; |
| 442 | |
| 443 | top_start = nla_nest_start(skb, tlv); |
| 444 | if (top_start == NULL) |
| 445 | goto nla_put_failure; |
| 446 | |
| 447 | if (nla_put(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr)) |
| 448 | goto nla_put_failure; |
| 449 | |
| 450 | list_start = nla_nest_start(skb, TCA_EMATCH_TREE_LIST); |
| 451 | if (list_start == NULL) |
| 452 | goto nla_put_failure; |
| 453 | |
| 454 | tail = skb_tail_pointer(skb); |
| 455 | for (i = 0; i < tree->hdr.nmatches; i++) { |
| 456 | struct nlattr *match_start = (struct nlattr *)tail; |
| 457 | struct tcf_ematch *em = tcf_em_get_match(tree, i); |
| 458 | struct tcf_ematch_hdr em_hdr = { |
| 459 | .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, |
| 460 | .matchid = em->matchid, |
| 461 | .flags = em->flags |
| 462 | }; |
| 463 | |
| 464 | if (nla_put(skb, i + 1, sizeof(em_hdr), &em_hdr)) |
| 465 | goto nla_put_failure; |
| 466 | |
| 467 | if (em->ops && em->ops->dump) { |
| 468 | if (em->ops->dump(skb, em) < 0) |
| 469 | goto nla_put_failure; |
| 470 | } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { |
| 471 | u32 u = em->data; |
| 472 | nla_put_nohdr(skb, sizeof(u), &u); |
| 473 | } else if (em->datalen > 0) |
| 474 | nla_put_nohdr(skb, em->datalen, (void *) em->data); |
| 475 | |
| 476 | tail = skb_tail_pointer(skb); |
| 477 | match_start->nla_len = tail - (u8 *)match_start; |
| 478 | } |
| 479 | |
| 480 | nla_nest_end(skb, list_start); |
| 481 | nla_nest_end(skb, top_start); |
| 482 | |
| 483 | return 0; |
| 484 | |
| 485 | nla_put_failure: |
| 486 | return -1; |
| 487 | } |
| 488 | EXPORT_SYMBOL(tcf_em_tree_dump); |
| 489 | |
| 490 | static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, |
| 491 | struct tcf_pkt_info *info) |
| 492 | { |
| 493 | int r = em->ops->match(skb, em, info); |
| 494 | |
| 495 | return tcf_em_is_inverted(em) ? !r : r; |
| 496 | } |
| 497 | |
| 498 | /* Do not use this function directly, use tcf_em_tree_match instead */ |
| 499 | int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, |
| 500 | struct tcf_pkt_info *info) |
| 501 | { |
| 502 | int stackp = 0, match_idx = 0, res = 0; |
| 503 | struct tcf_ematch *cur_match; |
| 504 | int stack[CONFIG_NET_EMATCH_STACK]; |
| 505 | |
| 506 | proceed: |
| 507 | while (match_idx < tree->hdr.nmatches) { |
| 508 | cur_match = tcf_em_get_match(tree, match_idx); |
| 509 | |
| 510 | if (tcf_em_is_container(cur_match)) { |
| 511 | if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) |
| 512 | goto stack_overflow; |
| 513 | |
| 514 | stack[stackp++] = match_idx; |
| 515 | match_idx = cur_match->data; |
| 516 | goto proceed; |
| 517 | } |
| 518 | |
| 519 | res = tcf_em_match(skb, cur_match, info); |
| 520 | |
| 521 | if (tcf_em_early_end(cur_match, res)) |
| 522 | break; |
| 523 | |
| 524 | match_idx++; |
| 525 | } |
| 526 | |
| 527 | pop_stack: |
| 528 | if (stackp > 0) { |
| 529 | match_idx = stack[--stackp]; |
| 530 | cur_match = tcf_em_get_match(tree, match_idx); |
| 531 | |
| 532 | if (tcf_em_is_inverted(cur_match)) |
| 533 | res = !res; |
| 534 | |
| 535 | if (tcf_em_early_end(cur_match, res)) { |
| 536 | goto pop_stack; |
| 537 | } else { |
| 538 | match_idx++; |
| 539 | goto proceed; |
| 540 | } |
| 541 | } |
| 542 | |
| 543 | return res; |
| 544 | |
| 545 | stack_overflow: |
| 546 | net_warn_ratelimited("tc ematch: local stack overflow, increase NET_EMATCH_STACK\n"); |
| 547 | return -1; |
| 548 | } |
| 549 | EXPORT_SYMBOL(__tcf_em_tree_match); |