1 /* 2 * Longest prefix match list implementation 3 * 4 * Copyright (c) 2016,2017 Daniel Mack 5 * Copyright (c) 2016 David Herrmann 6 * 7 * This file is subject to the terms and conditions of version 2 of the GNU 8 * General Public License. See the file COPYING in the main directory of the 9 * Linux distribution for more details. 10 */ 11 12 #include <linux/bpf.h> 13 #include <linux/btf.h> 14 #include <linux/err.h> 15 #include <linux/slab.h> 16 #include <linux/spinlock.h> 17 #include <linux/vmalloc.h> 18 #include <net/ipv6.h> 19 #include <uapi/linux/btf.h> 20 21 /* Intermediate node */ 22 #define LPM_TREE_NODE_FLAG_IM BIT(0) 23 24 struct lpm_trie_node; 25 26 struct lpm_trie_node { 27 struct rcu_head rcu; 28 struct lpm_trie_node __rcu *child[2]; 29 u32 prefixlen; 30 u32 flags; 31 u8 data[0]; 32 }; 33 34 struct lpm_trie { 35 struct bpf_map map; 36 struct lpm_trie_node __rcu *root; 37 size_t n_entries; 38 size_t max_prefixlen; 39 size_t data_size; 40 raw_spinlock_t lock; 41 }; 42 43 /* This trie implements a longest prefix match algorithm that can be used to 44 * match IP addresses to a stored set of ranges. 45 * 46 * Data stored in @data of struct bpf_lpm_key and struct lpm_trie_node is 47 * interpreted as big endian, so data[0] stores the most significant byte. 48 * 49 * Match ranges are internally stored in instances of struct lpm_trie_node 50 * which each contain their prefix length as well as two pointers that may 51 * lead to more nodes containing more specific matches. Each node also stores 52 * a value that is defined by and returned to userspace via the update_elem 53 * and lookup functions. 54 * 55 * For instance, let's start with a trie that was created with a prefix length 56 * of 32, so it can be used for IPv4 addresses, and one single element that 57 * matches 192.168.0.0/16. The data array would hence contain 58 * [0xc0, 0xa8, 0x00, 0x00] in big-endian notation. This documentation will 59 * stick to IP-address notation for readability though. 60 * 61 * As the trie is empty initially, the new node (1) will be places as root 62 * node, denoted as (R) in the example below. As there are no other node, both 63 * child pointers are %NULL. 64 * 65 * +----------------+ 66 * | (1) (R) | 67 * | 192.168.0.0/16 | 68 * | value: 1 | 69 * | [0] [1] | 70 * +----------------+ 71 * 72 * Next, let's add a new node (2) matching 192.168.0.0/24. As there is already 73 * a node with the same data and a smaller prefix (ie, a less specific one), 74 * node (2) will become a child of (1). In child index depends on the next bit 75 * that is outside of what (1) matches, and that bit is 0, so (2) will be 76 * child[0] of (1): 77 * 78 * +----------------+ 79 * | (1) (R) | 80 * | 192.168.0.0/16 | 81 * | value: 1 | 82 * | [0] [1] | 83 * +----------------+ 84 * | 85 * +----------------+ 86 * | (2) | 87 * | 192.168.0.0/24 | 88 * | value: 2 | 89 * | [0] [1] | 90 * +----------------+ 91 * 92 * The child[1] slot of (1) could be filled with another node which has bit #17 93 * (the next bit after the ones that (1) matches on) set to 1. For instance, 94 * 192.168.128.0/24: 95 * 96 * +----------------+ 97 * | (1) (R) | 98 * | 192.168.0.0/16 | 99 * | value: 1 | 100 * | [0] [1] | 101 * +----------------+ 102 * | | 103 * +----------------+ +------------------+ 104 * | (2) | | (3) | 105 * | 192.168.0.0/24 | | 192.168.128.0/24 | 106 * | value: 2 | | value: 3 | 107 * | [0] [1] | | [0] [1] | 108 * +----------------+ +------------------+ 109 * 110 * Let's add another node (4) to the game for 192.168.1.0/24. In order to place 111 * it, node (1) is looked at first, and because (4) of the semantics laid out 112 * above (bit #17 is 0), it would normally be attached to (1) as child[0]. 113 * However, that slot is already allocated, so a new node is needed in between. 114 * That node does not have a value attached to it and it will never be 115 * returned to users as result of a lookup. It is only there to differentiate 116 * the traversal further. It will get a prefix as wide as necessary to 117 * distinguish its two children: 118 * 119 * +----------------+ 120 * | (1) (R) | 121 * | 192.168.0.0/16 | 122 * | value: 1 | 123 * | [0] [1] | 124 * +----------------+ 125 * | | 126 * +----------------+ +------------------+ 127 * | (4) (I) | | (3) | 128 * | 192.168.0.0/23 | | 192.168.128.0/24 | 129 * | value: --- | | value: 3 | 130 * | [0] [1] | | [0] [1] | 131 * +----------------+ +------------------+ 132 * | | 133 * +----------------+ +----------------+ 134 * | (2) | | (5) | 135 * | 192.168.0.0/24 | | 192.168.1.0/24 | 136 * | value: 2 | | value: 5 | 137 * | [0] [1] | | [0] [1] | 138 * +----------------+ +----------------+ 139 * 140 * 192.168.1.1/32 would be a child of (5) etc. 141 * 142 * An intermediate node will be turned into a 'real' node on demand. In the 143 * example above, (4) would be re-used if 192.168.0.0/23 is added to the trie. 144 * 145 * A fully populated trie would have a height of 32 nodes, as the trie was 146 * created with a prefix length of 32. 147 * 148 * The lookup starts at the root node. If the current node matches and if there 149 * is a child that can be used to become more specific, the trie is traversed 150 * downwards. The last node in the traversal that is a non-intermediate one is 151 * returned. 152 */ 153 154 static inline int extract_bit(const u8 *data, size_t index) 155 { 156 return !!(data[index / 8] & (1 << (7 - (index % 8)))); 157 } 158 159 /** 160 * longest_prefix_match() - determine the longest prefix 161 * @trie: The trie to get internal sizes from 162 * @node: The node to operate on 163 * @key: The key to compare to @node 164 * 165 * Determine the longest prefix of @node that matches the bits in @key. 166 */ 167 static size_t longest_prefix_match(const struct lpm_trie *trie, 168 const struct lpm_trie_node *node, 169 const struct bpf_lpm_trie_key *key) 170 { 171 u32 limit = min(node->prefixlen, key->prefixlen); 172 u32 prefixlen = 0, i = 0; 173 174 BUILD_BUG_ON(offsetof(struct lpm_trie_node, data) % sizeof(u32)); 175 BUILD_BUG_ON(offsetof(struct bpf_lpm_trie_key, data) % sizeof(u32)); 176 177 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && defined(CONFIG_64BIT) 178 179 /* data_size >= 16 has very small probability. 180 * We do not use a loop for optimal code generation. 181 */ 182 if (trie->data_size >= 8) { 183 u64 diff = be64_to_cpu(*(__be64 *)node->data ^ 184 *(__be64 *)key->data); 185 186 prefixlen = 64 - fls64(diff); 187 if (prefixlen >= limit) 188 return limit; 189 if (diff) 190 return prefixlen; 191 i = 8; 192 } 193 #endif 194 195 while (trie->data_size >= i + 4) { 196 u32 diff = be32_to_cpu(*(__be32 *)&node->data[i] ^ 197 *(__be32 *)&key->data[i]); 198 199 prefixlen += 32 - fls(diff); 200 if (prefixlen >= limit) 201 return limit; 202 if (diff) 203 return prefixlen; 204 i += 4; 205 } 206 207 if (trie->data_size >= i + 2) { 208 u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] ^ 209 *(__be16 *)&key->data[i]); 210 211 prefixlen += 16 - fls(diff); 212 if (prefixlen >= limit) 213 return limit; 214 if (diff) 215 return prefixlen; 216 i += 2; 217 } 218 219 if (trie->data_size >= i + 1) { 220 prefixlen += 8 - fls(node->data[i] ^ key->data[i]); 221 222 if (prefixlen >= limit) 223 return limit; 224 } 225 226 return prefixlen; 227 } 228 229 /* Called from syscall or from eBPF program */ 230 static void *trie_lookup_elem(struct bpf_map *map, void *_key) 231 { 232 struct lpm_trie *trie = container_of(map, struct lpm_trie, map); 233 struct lpm_trie_node *node, *found = NULL; 234 struct bpf_lpm_trie_key *key = _key; 235 236 /* Start walking the trie from the root node ... */ 237 238 for (node = rcu_dereference(trie->root); node;) { 239 unsigned int next_bit; 240 size_t matchlen; 241 242 /* Determine the longest prefix of @node that matches @key. 243 * If it's the maximum possible prefix for this trie, we have 244 * an exact match and can return it directly. 245 */ 246 matchlen = longest_prefix_match(trie, node, key); 247 if (matchlen == trie->max_prefixlen) { 248 found = node; 249 break; 250 } 251 252 /* If the number of bits that match is smaller than the prefix 253 * length of @node, bail out and return the node we have seen 254 * last in the traversal (ie, the parent). 255 */ 256 if (matchlen < node->prefixlen) 257 break; 258 259 /* Consider this node as return candidate unless it is an 260 * artificially added intermediate one. 261 */ 262 if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) 263 found = node; 264 265 /* If the node match is fully satisfied, let's see if we can 266 * become more specific. Determine the next bit in the key and 267 * traverse down. 268 */ 269 next_bit = extract_bit(key->data, node->prefixlen); 270 node = rcu_dereference(node->child[next_bit]); 271 } 272 273 if (!found) 274 return NULL; 275 276 return found->data + trie->data_size; 277 } 278 279 static struct lpm_trie_node *lpm_trie_node_alloc(const struct lpm_trie *trie, 280 const void *value) 281 { 282 struct lpm_trie_node *node; 283 size_t size = sizeof(struct lpm_trie_node) + trie->data_size; 284 285 if (value) 286 size += trie->map.value_size; 287 288 node = kmalloc_node(size, GFP_ATOMIC | __GFP_NOWARN, 289 trie->map.numa_node); 290 if (!node) 291 return NULL; 292 293 node->flags = 0; 294 295 if (value) 296 memcpy(node->data + trie->data_size, value, 297 trie->map.value_size); 298 299 return node; 300 } 301 302 /* Called from syscall or from eBPF program */ 303 static int trie_update_elem(struct bpf_map *map, 304 void *_key, void *value, u64 flags) 305 { 306 struct lpm_trie *trie = container_of(map, struct lpm_trie, map); 307 struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL; 308 struct lpm_trie_node __rcu **slot; 309 struct bpf_lpm_trie_key *key = _key; 310 unsigned long irq_flags; 311 unsigned int next_bit; 312 size_t matchlen = 0; 313 int ret = 0; 314 315 if (unlikely(flags > BPF_EXIST)) 316 return -EINVAL; 317 318 if (key->prefixlen > trie->max_prefixlen) 319 return -EINVAL; 320 321 raw_spin_lock_irqsave(&trie->lock, irq_flags); 322 323 /* Allocate and fill a new node */ 324 325 if (trie->n_entries == trie->map.max_entries) { 326 ret = -ENOSPC; 327 goto out; 328 } 329 330 new_node = lpm_trie_node_alloc(trie, value); 331 if (!new_node) { 332 ret = -ENOMEM; 333 goto out; 334 } 335 336 trie->n_entries++; 337 338 new_node->prefixlen = key->prefixlen; 339 RCU_INIT_POINTER(new_node->child[0], NULL); 340 RCU_INIT_POINTER(new_node->child[1], NULL); 341 memcpy(new_node->data, key->data, trie->data_size); 342 343 /* Now find a slot to attach the new node. To do that, walk the tree 344 * from the root and match as many bits as possible for each node until 345 * we either find an empty slot or a slot that needs to be replaced by 346 * an intermediate node. 347 */ 348 slot = &trie->root; 349 350 while ((node = rcu_dereference_protected(*slot, 351 lockdep_is_held(&trie->lock)))) { 352 matchlen = longest_prefix_match(trie, node, key); 353 354 if (node->prefixlen != matchlen || 355 node->prefixlen == key->prefixlen || 356 node->prefixlen == trie->max_prefixlen) 357 break; 358 359 next_bit = extract_bit(key->data, node->prefixlen); 360 slot = &node->child[next_bit]; 361 } 362 363 /* If the slot is empty (a free child pointer or an empty root), 364 * simply assign the @new_node to that slot and be done. 365 */ 366 if (!node) { 367 rcu_assign_pointer(*slot, new_node); 368 goto out; 369 } 370 371 /* If the slot we picked already exists, replace it with @new_node 372 * which already has the correct data array set. 373 */ 374 if (node->prefixlen == matchlen) { 375 new_node->child[0] = node->child[0]; 376 new_node->child[1] = node->child[1]; 377 378 if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) 379 trie->n_entries--; 380 381 rcu_assign_pointer(*slot, new_node); 382 kfree_rcu(node, rcu); 383 384 goto out; 385 } 386 387 /* If the new node matches the prefix completely, it must be inserted 388 * as an ancestor. Simply insert it between @node and *@slot. 389 */ 390 if (matchlen == key->prefixlen) { 391 next_bit = extract_bit(node->data, matchlen); 392 rcu_assign_pointer(new_node->child[next_bit], node); 393 rcu_assign_pointer(*slot, new_node); 394 goto out; 395 } 396 397 im_node = lpm_trie_node_alloc(trie, NULL); 398 if (!im_node) { 399 ret = -ENOMEM; 400 goto out; 401 } 402 403 im_node->prefixlen = matchlen; 404 im_node->flags |= LPM_TREE_NODE_FLAG_IM; 405 memcpy(im_node->data, node->data, trie->data_size); 406 407 /* Now determine which child to install in which slot */ 408 if (extract_bit(key->data, matchlen)) { 409 rcu_assign_pointer(im_node->child[0], node); 410 rcu_assign_pointer(im_node->child[1], new_node); 411 } else { 412 rcu_assign_pointer(im_node->child[0], new_node); 413 rcu_assign_pointer(im_node->child[1], node); 414 } 415 416 /* Finally, assign the intermediate node to the determined spot */ 417 rcu_assign_pointer(*slot, im_node); 418 419 out: 420 if (ret) { 421 if (new_node) 422 trie->n_entries--; 423 424 kfree(new_node); 425 kfree(im_node); 426 } 427 428 raw_spin_unlock_irqrestore(&trie->lock, irq_flags); 429 430 return ret; 431 } 432 433 /* Called from syscall or from eBPF program */ 434 static int trie_delete_elem(struct bpf_map *map, void *_key) 435 { 436 struct lpm_trie *trie = container_of(map, struct lpm_trie, map); 437 struct bpf_lpm_trie_key *key = _key; 438 struct lpm_trie_node __rcu **trim, **trim2; 439 struct lpm_trie_node *node, *parent; 440 unsigned long irq_flags; 441 unsigned int next_bit; 442 size_t matchlen = 0; 443 int ret = 0; 444 445 if (key->prefixlen > trie->max_prefixlen) 446 return -EINVAL; 447 448 raw_spin_lock_irqsave(&trie->lock, irq_flags); 449 450 /* Walk the tree looking for an exact key/length match and keeping 451 * track of the path we traverse. We will need to know the node 452 * we wish to delete, and the slot that points to the node we want 453 * to delete. We may also need to know the nodes parent and the 454 * slot that contains it. 455 */ 456 trim = &trie->root; 457 trim2 = trim; 458 parent = NULL; 459 while ((node = rcu_dereference_protected( 460 *trim, lockdep_is_held(&trie->lock)))) { 461 matchlen = longest_prefix_match(trie, node, key); 462 463 if (node->prefixlen != matchlen || 464 node->prefixlen == key->prefixlen) 465 break; 466 467 parent = node; 468 trim2 = trim; 469 next_bit = extract_bit(key->data, node->prefixlen); 470 trim = &node->child[next_bit]; 471 } 472 473 if (!node || node->prefixlen != key->prefixlen || 474 node->prefixlen != matchlen || 475 (node->flags & LPM_TREE_NODE_FLAG_IM)) { 476 ret = -ENOENT; 477 goto out; 478 } 479 480 trie->n_entries--; 481 482 /* If the node we are removing has two children, simply mark it 483 * as intermediate and we are done. 484 */ 485 if (rcu_access_pointer(node->child[0]) && 486 rcu_access_pointer(node->child[1])) { 487 node->flags |= LPM_TREE_NODE_FLAG_IM; 488 goto out; 489 } 490 491 /* If the parent of the node we are about to delete is an intermediate 492 * node, and the deleted node doesn't have any children, we can delete 493 * the intermediate parent as well and promote its other child 494 * up the tree. Doing this maintains the invariant that all 495 * intermediate nodes have exactly 2 children and that there are no 496 * unnecessary intermediate nodes in the tree. 497 */ 498 if (parent && (parent->flags & LPM_TREE_NODE_FLAG_IM) && 499 !node->child[0] && !node->child[1]) { 500 if (node == rcu_access_pointer(parent->child[0])) 501 rcu_assign_pointer( 502 *trim2, rcu_access_pointer(parent->child[1])); 503 else 504 rcu_assign_pointer( 505 *trim2, rcu_access_pointer(parent->child[0])); 506 kfree_rcu(parent, rcu); 507 kfree_rcu(node, rcu); 508 goto out; 509 } 510 511 /* The node we are removing has either zero or one child. If there 512 * is a child, move it into the removed node's slot then delete 513 * the node. Otherwise just clear the slot and delete the node. 514 */ 515 if (node->child[0]) 516 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[0])); 517 else if (node->child[1]) 518 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1])); 519 else 520 RCU_INIT_POINTER(*trim, NULL); 521 kfree_rcu(node, rcu); 522 523 out: 524 raw_spin_unlock_irqrestore(&trie->lock, irq_flags); 525 526 return ret; 527 } 528 529 #define LPM_DATA_SIZE_MAX 256 530 #define LPM_DATA_SIZE_MIN 1 531 532 #define LPM_VAL_SIZE_MAX (KMALLOC_MAX_SIZE - LPM_DATA_SIZE_MAX - \ 533 sizeof(struct lpm_trie_node)) 534 #define LPM_VAL_SIZE_MIN 1 535 536 #define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key) + (X)) 537 #define LPM_KEY_SIZE_MAX LPM_KEY_SIZE(LPM_DATA_SIZE_MAX) 538 #define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN) 539 540 #define LPM_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE | \ 541 BPF_F_RDONLY | BPF_F_WRONLY) 542 543 static struct bpf_map *trie_alloc(union bpf_attr *attr) 544 { 545 struct lpm_trie *trie; 546 u64 cost = sizeof(*trie), cost_per_node; 547 int ret; 548 549 if (!capable(CAP_SYS_ADMIN)) 550 return ERR_PTR(-EPERM); 551 552 /* check sanity of attributes */ 553 if (attr->max_entries == 0 || 554 !(attr->map_flags & BPF_F_NO_PREALLOC) || 555 attr->map_flags & ~LPM_CREATE_FLAG_MASK || 556 attr->key_size < LPM_KEY_SIZE_MIN || 557 attr->key_size > LPM_KEY_SIZE_MAX || 558 attr->value_size < LPM_VAL_SIZE_MIN || 559 attr->value_size > LPM_VAL_SIZE_MAX) 560 return ERR_PTR(-EINVAL); 561 562 trie = kzalloc(sizeof(*trie), GFP_USER | __GFP_NOWARN); 563 if (!trie) 564 return ERR_PTR(-ENOMEM); 565 566 /* copy mandatory map attributes */ 567 bpf_map_init_from_attr(&trie->map, attr); 568 trie->data_size = attr->key_size - 569 offsetof(struct bpf_lpm_trie_key, data); 570 trie->max_prefixlen = trie->data_size * 8; 571 572 cost_per_node = sizeof(struct lpm_trie_node) + 573 attr->value_size + trie->data_size; 574 cost += (u64) attr->max_entries * cost_per_node; 575 if (cost >= U32_MAX - PAGE_SIZE) { 576 ret = -E2BIG; 577 goto out_err; 578 } 579 580 trie->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; 581 582 ret = bpf_map_precharge_memlock(trie->map.pages); 583 if (ret) 584 goto out_err; 585 586 raw_spin_lock_init(&trie->lock); 587 588 return &trie->map; 589 out_err: 590 kfree(trie); 591 return ERR_PTR(ret); 592 } 593 594 static void trie_free(struct bpf_map *map) 595 { 596 struct lpm_trie *trie = container_of(map, struct lpm_trie, map); 597 struct lpm_trie_node __rcu **slot; 598 struct lpm_trie_node *node; 599 600 /* Wait for outstanding programs to complete 601 * update/lookup/delete/get_next_key and free the trie. 602 */ 603 synchronize_rcu(); 604 605 /* Always start at the root and walk down to a node that has no 606 * children. Then free that node, nullify its reference in the parent 607 * and start over. 608 */ 609 610 for (;;) { 611 slot = &trie->root; 612 613 for (;;) { 614 node = rcu_dereference_protected(*slot, 1); 615 if (!node) 616 goto out; 617 618 if (rcu_access_pointer(node->child[0])) { 619 slot = &node->child[0]; 620 continue; 621 } 622 623 if (rcu_access_pointer(node->child[1])) { 624 slot = &node->child[1]; 625 continue; 626 } 627 628 kfree(node); 629 RCU_INIT_POINTER(*slot, NULL); 630 break; 631 } 632 } 633 634 out: 635 kfree(trie); 636 } 637 638 static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key) 639 { 640 struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root; 641 struct lpm_trie *trie = container_of(map, struct lpm_trie, map); 642 struct bpf_lpm_trie_key *key = _key, *next_key = _next_key; 643 struct lpm_trie_node **node_stack = NULL; 644 int err = 0, stack_ptr = -1; 645 unsigned int next_bit; 646 size_t matchlen; 647 648 /* The get_next_key follows postorder. For the 4 node example in 649 * the top of this file, the trie_get_next_key() returns the following 650 * one after another: 651 * 192.168.0.0/24 652 * 192.168.1.0/24 653 * 192.168.128.0/24 654 * 192.168.0.0/16 655 * 656 * The idea is to return more specific keys before less specific ones. 657 */ 658 659 /* Empty trie */ 660 search_root = rcu_dereference(trie->root); 661 if (!search_root) 662 return -ENOENT; 663 664 /* For invalid key, find the leftmost node in the trie */ 665 if (!key || key->prefixlen > trie->max_prefixlen) 666 goto find_leftmost; 667 668 node_stack = kmalloc_array(trie->max_prefixlen, 669 sizeof(struct lpm_trie_node *), 670 GFP_ATOMIC | __GFP_NOWARN); 671 if (!node_stack) 672 return -ENOMEM; 673 674 /* Try to find the exact node for the given key */ 675 for (node = search_root; node;) { 676 node_stack[++stack_ptr] = node; 677 matchlen = longest_prefix_match(trie, node, key); 678 if (node->prefixlen != matchlen || 679 node->prefixlen == key->prefixlen) 680 break; 681 682 next_bit = extract_bit(key->data, node->prefixlen); 683 node = rcu_dereference(node->child[next_bit]); 684 } 685 if (!node || node->prefixlen != key->prefixlen || 686 (node->flags & LPM_TREE_NODE_FLAG_IM)) 687 goto find_leftmost; 688 689 /* The node with the exactly-matching key has been found, 690 * find the first node in postorder after the matched node. 691 */ 692 node = node_stack[stack_ptr]; 693 while (stack_ptr > 0) { 694 parent = node_stack[stack_ptr - 1]; 695 if (rcu_dereference(parent->child[0]) == node) { 696 search_root = rcu_dereference(parent->child[1]); 697 if (search_root) 698 goto find_leftmost; 699 } 700 if (!(parent->flags & LPM_TREE_NODE_FLAG_IM)) { 701 next_node = parent; 702 goto do_copy; 703 } 704 705 node = parent; 706 stack_ptr--; 707 } 708 709 /* did not find anything */ 710 err = -ENOENT; 711 goto free_stack; 712 713 find_leftmost: 714 /* Find the leftmost non-intermediate node, all intermediate nodes 715 * have exact two children, so this function will never return NULL. 716 */ 717 for (node = search_root; node;) { 718 if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) 719 next_node = node; 720 node = rcu_dereference(node->child[0]); 721 } 722 do_copy: 723 next_key->prefixlen = next_node->prefixlen; 724 memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key, data), 725 next_node->data, trie->data_size); 726 free_stack: 727 kfree(node_stack); 728 return err; 729 } 730 731 static int trie_check_btf(const struct bpf_map *map, 732 const struct btf *btf, 733 const struct btf_type *key_type, 734 const struct btf_type *value_type) 735 { 736 /* Keys must have struct bpf_lpm_trie_key embedded. */ 737 return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ? 738 -EINVAL : 0; 739 } 740 741 const struct bpf_map_ops trie_map_ops = { 742 .map_alloc = trie_alloc, 743 .map_free = trie_free, 744 .map_get_next_key = trie_get_next_key, 745 .map_lookup_elem = trie_lookup_elem, 746 .map_update_elem = trie_update_elem, 747 .map_delete_elem = trie_delete_elem, 748 .map_check_btf = trie_check_btf, 749 }; 750