1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Longest prefix match list implementation
4 *
5 * Copyright (c) 2016,2017 Daniel Mack
6 * Copyright (c) 2016 David Herrmann
7 */
8
9 #include <linux/bpf.h>
10 #include <linux/btf.h>
11 #include <linux/err.h>
12 #include <linux/slab.h>
13 #include <linux/spinlock.h>
14 #include <linux/vmalloc.h>
15 #include <net/ipv6.h>
16 #include <uapi/linux/btf.h>
17 #include <linux/btf_ids.h>
18 #include <linux/bpf_mem_alloc.h>
19
20 /* Intermediate node */
21 #define LPM_TREE_NODE_FLAG_IM BIT(0)
22
23 struct lpm_trie_node;
24
25 struct lpm_trie_node {
26 struct lpm_trie_node __rcu *child[2];
27 u32 prefixlen;
28 u32 flags;
29 u8 data[];
30 };
31
32 struct lpm_trie {
33 struct bpf_map map;
34 struct lpm_trie_node __rcu *root;
35 struct bpf_mem_alloc ma;
36 size_t n_entries;
37 size_t max_prefixlen;
38 size_t data_size;
39 raw_spinlock_t lock;
40 };
41
42 /* This trie implements a longest prefix match algorithm that can be used to
43 * match IP addresses to a stored set of ranges.
44 *
45 * Data stored in @data of struct bpf_lpm_key and struct lpm_trie_node is
46 * interpreted as big endian, so data[0] stores the most significant byte.
47 *
48 * Match ranges are internally stored in instances of struct lpm_trie_node
49 * which each contain their prefix length as well as two pointers that may
50 * lead to more nodes containing more specific matches. Each node also stores
51 * a value that is defined by and returned to userspace via the update_elem
52 * and lookup functions.
53 *
54 * For instance, let's start with a trie that was created with a prefix length
55 * of 32, so it can be used for IPv4 addresses, and one single element that
56 * matches 192.168.0.0/16. The data array would hence contain
57 * [0xc0, 0xa8, 0x00, 0x00] in big-endian notation. This documentation will
58 * stick to IP-address notation for readability though.
59 *
60 * As the trie is empty initially, the new node (1) will be places as root
61 * node, denoted as (R) in the example below. As there are no other node, both
62 * child pointers are %NULL.
63 *
64 * +----------------+
65 * | (1) (R) |
66 * | 192.168.0.0/16 |
67 * | value: 1 |
68 * | [0] [1] |
69 * +----------------+
70 *
71 * Next, let's add a new node (2) matching 192.168.0.0/24. As there is already
72 * a node with the same data and a smaller prefix (ie, a less specific one),
73 * node (2) will become a child of (1). In child index depends on the next bit
74 * that is outside of what (1) matches, and that bit is 0, so (2) will be
75 * child[0] of (1):
76 *
77 * +----------------+
78 * | (1) (R) |
79 * | 192.168.0.0/16 |
80 * | value: 1 |
81 * | [0] [1] |
82 * +----------------+
83 * |
84 * +----------------+
85 * | (2) |
86 * | 192.168.0.0/24 |
87 * | value: 2 |
88 * | [0] [1] |
89 * +----------------+
90 *
91 * The child[1] slot of (1) could be filled with another node which has bit #17
92 * (the next bit after the ones that (1) matches on) set to 1. For instance,
93 * 192.168.128.0/24:
94 *
95 * +----------------+
96 * | (1) (R) |
97 * | 192.168.0.0/16 |
98 * | value: 1 |
99 * | [0] [1] |
100 * +----------------+
101 * | |
102 * +----------------+ +------------------+
103 * | (2) | | (3) |
104 * | 192.168.0.0/24 | | 192.168.128.0/24 |
105 * | value: 2 | | value: 3 |
106 * | [0] [1] | | [0] [1] |
107 * +----------------+ +------------------+
108 *
109 * Let's add another node (4) to the game for 192.168.1.0/24. In order to place
110 * it, node (1) is looked at first, and because (4) of the semantics laid out
111 * above (bit #17 is 0), it would normally be attached to (1) as child[0].
112 * However, that slot is already allocated, so a new node is needed in between.
113 * That node does not have a value attached to it and it will never be
114 * returned to users as result of a lookup. It is only there to differentiate
115 * the traversal further. It will get a prefix as wide as necessary to
116 * distinguish its two children:
117 *
118 * +----------------+
119 * | (1) (R) |
120 * | 192.168.0.0/16 |
121 * | value: 1 |
122 * | [0] [1] |
123 * +----------------+
124 * | |
125 * +----------------+ +------------------+
126 * | (4) (I) | | (3) |
127 * | 192.168.0.0/23 | | 192.168.128.0/24 |
128 * | value: --- | | value: 3 |
129 * | [0] [1] | | [0] [1] |
130 * +----------------+ +------------------+
131 * | |
132 * +----------------+ +----------------+
133 * | (2) | | (5) |
134 * | 192.168.0.0/24 | | 192.168.1.0/24 |
135 * | value: 2 | | value: 5 |
136 * | [0] [1] | | [0] [1] |
137 * +----------------+ +----------------+
138 *
139 * 192.168.1.1/32 would be a child of (5) etc.
140 *
141 * An intermediate node will be turned into a 'real' node on demand. In the
142 * example above, (4) would be re-used if 192.168.0.0/23 is added to the trie.
143 *
144 * A fully populated trie would have a height of 32 nodes, as the trie was
145 * created with a prefix length of 32.
146 *
147 * The lookup starts at the root node. If the current node matches and if there
148 * is a child that can be used to become more specific, the trie is traversed
149 * downwards. The last node in the traversal that is a non-intermediate one is
150 * returned.
151 */
152
extract_bit(const u8 * data,size_t index)153 static inline int extract_bit(const u8 *data, size_t index)
154 {
155 return !!(data[index / 8] & (1 << (7 - (index % 8))));
156 }
157
158 /**
159 * __longest_prefix_match() - determine the longest prefix
160 * @trie: The trie to get internal sizes from
161 * @node: The node to operate on
162 * @key: The key to compare to @node
163 *
164 * Determine the longest prefix of @node that matches the bits in @key.
165 */
166 static __always_inline
__longest_prefix_match(const struct lpm_trie * trie,const struct lpm_trie_node * node,const struct bpf_lpm_trie_key_u8 * key)167 size_t __longest_prefix_match(const struct lpm_trie *trie,
168 const struct lpm_trie_node *node,
169 const struct bpf_lpm_trie_key_u8 *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_u8, 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
longest_prefix_match(const struct lpm_trie * trie,const struct lpm_trie_node * node,const struct bpf_lpm_trie_key_u8 * key)229 static size_t longest_prefix_match(const struct lpm_trie *trie,
230 const struct lpm_trie_node *node,
231 const struct bpf_lpm_trie_key_u8 *key)
232 {
233 return __longest_prefix_match(trie, node, key);
234 }
235
236 /* Called from syscall or from eBPF program */
trie_lookup_elem(struct bpf_map * map,void * _key)237 static void *trie_lookup_elem(struct bpf_map *map, void *_key)
238 {
239 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
240 struct lpm_trie_node *node, *found = NULL;
241 struct bpf_lpm_trie_key_u8 *key = _key;
242
243 if (key->prefixlen > trie->max_prefixlen)
244 return NULL;
245
246 /* Start walking the trie from the root node ... */
247
248 for (node = rcu_dereference_check(trie->root, rcu_read_lock_bh_held());
249 node;) {
250 unsigned int next_bit;
251 size_t matchlen;
252
253 /* Determine the longest prefix of @node that matches @key.
254 * If it's the maximum possible prefix for this trie, we have
255 * an exact match and can return it directly.
256 */
257 matchlen = __longest_prefix_match(trie, node, key);
258 if (matchlen == trie->max_prefixlen) {
259 found = node;
260 break;
261 }
262
263 /* If the number of bits that match is smaller than the prefix
264 * length of @node, bail out and return the node we have seen
265 * last in the traversal (ie, the parent).
266 */
267 if (matchlen < node->prefixlen)
268 break;
269
270 /* Consider this node as return candidate unless it is an
271 * artificially added intermediate one.
272 */
273 if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
274 found = node;
275
276 /* If the node match is fully satisfied, let's see if we can
277 * become more specific. Determine the next bit in the key and
278 * traverse down.
279 */
280 next_bit = extract_bit(key->data, node->prefixlen);
281 node = rcu_dereference_check(node->child[next_bit],
282 rcu_read_lock_bh_held());
283 }
284
285 if (!found)
286 return NULL;
287
288 return found->data + trie->data_size;
289 }
290
lpm_trie_node_alloc(struct lpm_trie * trie,const void * value)291 static struct lpm_trie_node *lpm_trie_node_alloc(struct lpm_trie *trie,
292 const void *value)
293 {
294 struct lpm_trie_node *node;
295
296 node = bpf_mem_cache_alloc(&trie->ma);
297
298 if (!node)
299 return NULL;
300
301 node->flags = 0;
302
303 if (value)
304 memcpy(node->data + trie->data_size, value,
305 trie->map.value_size);
306
307 return node;
308 }
309
trie_check_add_elem(struct lpm_trie * trie,u64 flags)310 static int trie_check_add_elem(struct lpm_trie *trie, u64 flags)
311 {
312 if (flags == BPF_EXIST)
313 return -ENOENT;
314 if (trie->n_entries == trie->map.max_entries)
315 return -ENOSPC;
316 trie->n_entries++;
317 return 0;
318 }
319
320 /* Called from syscall or from eBPF program */
trie_update_elem(struct bpf_map * map,void * _key,void * value,u64 flags)321 static long trie_update_elem(struct bpf_map *map,
322 void *_key, void *value, u64 flags)
323 {
324 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
325 struct lpm_trie_node *node, *im_node, *new_node;
326 struct lpm_trie_node *free_node = NULL;
327 struct lpm_trie_node __rcu **slot;
328 struct bpf_lpm_trie_key_u8 *key = _key;
329 unsigned long irq_flags;
330 unsigned int next_bit;
331 size_t matchlen = 0;
332 int ret = 0;
333
334 if (unlikely(flags > BPF_EXIST))
335 return -EINVAL;
336
337 if (key->prefixlen > trie->max_prefixlen)
338 return -EINVAL;
339
340 /* Allocate and fill a new node */
341 new_node = lpm_trie_node_alloc(trie, value);
342 if (!new_node)
343 return -ENOMEM;
344
345 raw_spin_lock_irqsave(&trie->lock, irq_flags);
346
347 new_node->prefixlen = key->prefixlen;
348 RCU_INIT_POINTER(new_node->child[0], NULL);
349 RCU_INIT_POINTER(new_node->child[1], NULL);
350 memcpy(new_node->data, key->data, trie->data_size);
351
352 /* Now find a slot to attach the new node. To do that, walk the tree
353 * from the root and match as many bits as possible for each node until
354 * we either find an empty slot or a slot that needs to be replaced by
355 * an intermediate node.
356 */
357 slot = &trie->root;
358
359 while ((node = rcu_dereference_protected(*slot,
360 lockdep_is_held(&trie->lock)))) {
361 matchlen = longest_prefix_match(trie, node, key);
362
363 if (node->prefixlen != matchlen ||
364 node->prefixlen == key->prefixlen)
365 break;
366
367 next_bit = extract_bit(key->data, node->prefixlen);
368 slot = &node->child[next_bit];
369 }
370
371 /* If the slot is empty (a free child pointer or an empty root),
372 * simply assign the @new_node to that slot and be done.
373 */
374 if (!node) {
375 ret = trie_check_add_elem(trie, flags);
376 if (ret)
377 goto out;
378
379 rcu_assign_pointer(*slot, new_node);
380 goto out;
381 }
382
383 /* If the slot we picked already exists, replace it with @new_node
384 * which already has the correct data array set.
385 */
386 if (node->prefixlen == matchlen) {
387 if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) {
388 if (flags == BPF_NOEXIST) {
389 ret = -EEXIST;
390 goto out;
391 }
392 } else {
393 ret = trie_check_add_elem(trie, flags);
394 if (ret)
395 goto out;
396 }
397
398 new_node->child[0] = node->child[0];
399 new_node->child[1] = node->child[1];
400
401 rcu_assign_pointer(*slot, new_node);
402 free_node = node;
403
404 goto out;
405 }
406
407 ret = trie_check_add_elem(trie, flags);
408 if (ret)
409 goto out;
410
411 /* If the new node matches the prefix completely, it must be inserted
412 * as an ancestor. Simply insert it between @node and *@slot.
413 */
414 if (matchlen == key->prefixlen) {
415 next_bit = extract_bit(node->data, matchlen);
416 rcu_assign_pointer(new_node->child[next_bit], node);
417 rcu_assign_pointer(*slot, new_node);
418 goto out;
419 }
420
421 im_node = lpm_trie_node_alloc(trie, NULL);
422 if (!im_node) {
423 trie->n_entries--;
424 ret = -ENOMEM;
425 goto out;
426 }
427
428 im_node->prefixlen = matchlen;
429 im_node->flags |= LPM_TREE_NODE_FLAG_IM;
430 memcpy(im_node->data, node->data, trie->data_size);
431
432 /* Now determine which child to install in which slot */
433 if (extract_bit(key->data, matchlen)) {
434 rcu_assign_pointer(im_node->child[0], node);
435 rcu_assign_pointer(im_node->child[1], new_node);
436 } else {
437 rcu_assign_pointer(im_node->child[0], new_node);
438 rcu_assign_pointer(im_node->child[1], node);
439 }
440
441 /* Finally, assign the intermediate node to the determined slot */
442 rcu_assign_pointer(*slot, im_node);
443
444 out:
445 raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
446
447 if (ret)
448 bpf_mem_cache_free(&trie->ma, new_node);
449 bpf_mem_cache_free_rcu(&trie->ma, free_node);
450
451 return ret;
452 }
453
454 /* Called from syscall or from eBPF program */
trie_delete_elem(struct bpf_map * map,void * _key)455 static long trie_delete_elem(struct bpf_map *map, void *_key)
456 {
457 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
458 struct lpm_trie_node *free_node = NULL, *free_parent = NULL;
459 struct bpf_lpm_trie_key_u8 *key = _key;
460 struct lpm_trie_node __rcu **trim, **trim2;
461 struct lpm_trie_node *node, *parent;
462 unsigned long irq_flags;
463 unsigned int next_bit;
464 size_t matchlen = 0;
465 int ret = 0;
466
467 if (key->prefixlen > trie->max_prefixlen)
468 return -EINVAL;
469
470 raw_spin_lock_irqsave(&trie->lock, irq_flags);
471
472 /* Walk the tree looking for an exact key/length match and keeping
473 * track of the path we traverse. We will need to know the node
474 * we wish to delete, and the slot that points to the node we want
475 * to delete. We may also need to know the nodes parent and the
476 * slot that contains it.
477 */
478 trim = &trie->root;
479 trim2 = trim;
480 parent = NULL;
481 while ((node = rcu_dereference_protected(
482 *trim, lockdep_is_held(&trie->lock)))) {
483 matchlen = longest_prefix_match(trie, node, key);
484
485 if (node->prefixlen != matchlen ||
486 node->prefixlen == key->prefixlen)
487 break;
488
489 parent = node;
490 trim2 = trim;
491 next_bit = extract_bit(key->data, node->prefixlen);
492 trim = &node->child[next_bit];
493 }
494
495 if (!node || node->prefixlen != key->prefixlen ||
496 node->prefixlen != matchlen ||
497 (node->flags & LPM_TREE_NODE_FLAG_IM)) {
498 ret = -ENOENT;
499 goto out;
500 }
501
502 trie->n_entries--;
503
504 /* If the node we are removing has two children, simply mark it
505 * as intermediate and we are done.
506 */
507 if (rcu_access_pointer(node->child[0]) &&
508 rcu_access_pointer(node->child[1])) {
509 node->flags |= LPM_TREE_NODE_FLAG_IM;
510 goto out;
511 }
512
513 /* If the parent of the node we are about to delete is an intermediate
514 * node, and the deleted node doesn't have any children, we can delete
515 * the intermediate parent as well and promote its other child
516 * up the tree. Doing this maintains the invariant that all
517 * intermediate nodes have exactly 2 children and that there are no
518 * unnecessary intermediate nodes in the tree.
519 */
520 if (parent && (parent->flags & LPM_TREE_NODE_FLAG_IM) &&
521 !node->child[0] && !node->child[1]) {
522 if (node == rcu_access_pointer(parent->child[0]))
523 rcu_assign_pointer(
524 *trim2, rcu_access_pointer(parent->child[1]));
525 else
526 rcu_assign_pointer(
527 *trim2, rcu_access_pointer(parent->child[0]));
528 free_parent = parent;
529 free_node = node;
530 goto out;
531 }
532
533 /* The node we are removing has either zero or one child. If there
534 * is a child, move it into the removed node's slot then delete
535 * the node. Otherwise just clear the slot and delete the node.
536 */
537 if (node->child[0])
538 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[0]));
539 else if (node->child[1])
540 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1]));
541 else
542 RCU_INIT_POINTER(*trim, NULL);
543 free_node = node;
544
545 out:
546 raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
547
548 bpf_mem_cache_free_rcu(&trie->ma, free_parent);
549 bpf_mem_cache_free_rcu(&trie->ma, free_node);
550
551 return ret;
552 }
553
554 #define LPM_DATA_SIZE_MAX 256
555 #define LPM_DATA_SIZE_MIN 1
556
557 #define LPM_VAL_SIZE_MAX (KMALLOC_MAX_SIZE - LPM_DATA_SIZE_MAX - \
558 sizeof(struct lpm_trie_node))
559 #define LPM_VAL_SIZE_MIN 1
560
561 #define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key_u8) + (X))
562 #define LPM_KEY_SIZE_MAX LPM_KEY_SIZE(LPM_DATA_SIZE_MAX)
563 #define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN)
564
565 #define LPM_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE | \
566 BPF_F_ACCESS_MASK)
567
trie_alloc(union bpf_attr * attr)568 static struct bpf_map *trie_alloc(union bpf_attr *attr)
569 {
570 struct lpm_trie *trie;
571 size_t leaf_size;
572 int err;
573
574 /* check sanity of attributes */
575 if (attr->max_entries == 0 ||
576 !(attr->map_flags & BPF_F_NO_PREALLOC) ||
577 attr->map_flags & ~LPM_CREATE_FLAG_MASK ||
578 !bpf_map_flags_access_ok(attr->map_flags) ||
579 attr->key_size < LPM_KEY_SIZE_MIN ||
580 attr->key_size > LPM_KEY_SIZE_MAX ||
581 attr->value_size < LPM_VAL_SIZE_MIN ||
582 attr->value_size > LPM_VAL_SIZE_MAX)
583 return ERR_PTR(-EINVAL);
584
585 trie = bpf_map_area_alloc(sizeof(*trie), NUMA_NO_NODE);
586 if (!trie)
587 return ERR_PTR(-ENOMEM);
588
589 /* copy mandatory map attributes */
590 bpf_map_init_from_attr(&trie->map, attr);
591 trie->data_size = attr->key_size -
592 offsetof(struct bpf_lpm_trie_key_u8, data);
593 trie->max_prefixlen = trie->data_size * 8;
594
595 raw_spin_lock_init(&trie->lock);
596
597 /* Allocate intermediate and leaf nodes from the same allocator */
598 leaf_size = sizeof(struct lpm_trie_node) + trie->data_size +
599 trie->map.value_size;
600 err = bpf_mem_alloc_init(&trie->ma, leaf_size, false);
601 if (err)
602 goto free_out;
603 return &trie->map;
604
605 free_out:
606 bpf_map_area_free(trie);
607 return ERR_PTR(err);
608 }
609
trie_free(struct bpf_map * map)610 static void trie_free(struct bpf_map *map)
611 {
612 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
613 struct lpm_trie_node __rcu **slot;
614 struct lpm_trie_node *node;
615
616 /* Always start at the root and walk down to a node that has no
617 * children. Then free that node, nullify its reference in the parent
618 * and start over.
619 */
620
621 for (;;) {
622 slot = &trie->root;
623
624 for (;;) {
625 node = rcu_dereference_protected(*slot, 1);
626 if (!node)
627 goto out;
628
629 if (rcu_access_pointer(node->child[0])) {
630 slot = &node->child[0];
631 continue;
632 }
633
634 if (rcu_access_pointer(node->child[1])) {
635 slot = &node->child[1];
636 continue;
637 }
638
639 /* No bpf program may access the map, so freeing the
640 * node without waiting for the extra RCU GP.
641 */
642 bpf_mem_cache_raw_free(node);
643 RCU_INIT_POINTER(*slot, NULL);
644 break;
645 }
646 }
647
648 out:
649 bpf_mem_alloc_destroy(&trie->ma);
650 bpf_map_area_free(trie);
651 }
652
trie_get_next_key(struct bpf_map * map,void * _key,void * _next_key)653 static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key)
654 {
655 struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root;
656 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
657 struct bpf_lpm_trie_key_u8 *key = _key, *next_key = _next_key;
658 struct lpm_trie_node **node_stack = NULL;
659 int err = 0, stack_ptr = -1;
660 unsigned int next_bit;
661 size_t matchlen = 0;
662
663 /* The get_next_key follows postorder. For the 4 node example in
664 * the top of this file, the trie_get_next_key() returns the following
665 * one after another:
666 * 192.168.0.0/24
667 * 192.168.1.0/24
668 * 192.168.128.0/24
669 * 192.168.0.0/16
670 *
671 * The idea is to return more specific keys before less specific ones.
672 */
673
674 /* Empty trie */
675 search_root = rcu_dereference(trie->root);
676 if (!search_root)
677 return -ENOENT;
678
679 /* For invalid key, find the leftmost node in the trie */
680 if (!key || key->prefixlen > trie->max_prefixlen)
681 goto find_leftmost;
682
683 node_stack = kmalloc_array(trie->max_prefixlen + 1,
684 sizeof(struct lpm_trie_node *),
685 GFP_ATOMIC | __GFP_NOWARN);
686 if (!node_stack)
687 return -ENOMEM;
688
689 /* Try to find the exact node for the given key */
690 for (node = search_root; node;) {
691 node_stack[++stack_ptr] = node;
692 matchlen = longest_prefix_match(trie, node, key);
693 if (node->prefixlen != matchlen ||
694 node->prefixlen == key->prefixlen)
695 break;
696
697 next_bit = extract_bit(key->data, node->prefixlen);
698 node = rcu_dereference(node->child[next_bit]);
699 }
700 if (!node || node->prefixlen != matchlen ||
701 (node->flags & LPM_TREE_NODE_FLAG_IM))
702 goto find_leftmost;
703
704 /* The node with the exactly-matching key has been found,
705 * find the first node in postorder after the matched node.
706 */
707 node = node_stack[stack_ptr];
708 while (stack_ptr > 0) {
709 parent = node_stack[stack_ptr - 1];
710 if (rcu_dereference(parent->child[0]) == node) {
711 search_root = rcu_dereference(parent->child[1]);
712 if (search_root)
713 goto find_leftmost;
714 }
715 if (!(parent->flags & LPM_TREE_NODE_FLAG_IM)) {
716 next_node = parent;
717 goto do_copy;
718 }
719
720 node = parent;
721 stack_ptr--;
722 }
723
724 /* did not find anything */
725 err = -ENOENT;
726 goto free_stack;
727
728 find_leftmost:
729 /* Find the leftmost non-intermediate node, all intermediate nodes
730 * have exact two children, so this function will never return NULL.
731 */
732 for (node = search_root; node;) {
733 if (node->flags & LPM_TREE_NODE_FLAG_IM) {
734 node = rcu_dereference(node->child[0]);
735 } else {
736 next_node = node;
737 node = rcu_dereference(node->child[0]);
738 if (!node)
739 node = rcu_dereference(next_node->child[1]);
740 }
741 }
742 do_copy:
743 next_key->prefixlen = next_node->prefixlen;
744 memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key_u8, data),
745 next_node->data, trie->data_size);
746 free_stack:
747 kfree(node_stack);
748 return err;
749 }
750
trie_check_btf(const struct bpf_map * map,const struct btf * btf,const struct btf_type * key_type,const struct btf_type * value_type)751 static int trie_check_btf(const struct bpf_map *map,
752 const struct btf *btf,
753 const struct btf_type *key_type,
754 const struct btf_type *value_type)
755 {
756 /* Keys must have struct bpf_lpm_trie_key_u8 embedded. */
757 return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ?
758 -EINVAL : 0;
759 }
760
trie_mem_usage(const struct bpf_map * map)761 static u64 trie_mem_usage(const struct bpf_map *map)
762 {
763 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
764 u64 elem_size;
765
766 elem_size = sizeof(struct lpm_trie_node) + trie->data_size +
767 trie->map.value_size;
768 return elem_size * READ_ONCE(trie->n_entries);
769 }
770
771 BTF_ID_LIST_SINGLE(trie_map_btf_ids, struct, lpm_trie)
772 const struct bpf_map_ops trie_map_ops = {
773 .map_meta_equal = bpf_map_meta_equal,
774 .map_alloc = trie_alloc,
775 .map_free = trie_free,
776 .map_get_next_key = trie_get_next_key,
777 .map_lookup_elem = trie_lookup_elem,
778 .map_update_elem = trie_update_elem,
779 .map_delete_elem = trie_delete_elem,
780 .map_lookup_batch = generic_map_lookup_batch,
781 .map_update_batch = generic_map_update_batch,
782 .map_delete_batch = generic_map_delete_batch,
783 .map_check_btf = trie_check_btf,
784 .map_mem_usage = trie_mem_usage,
785 .map_btf_id = &trie_map_btf_ids[0],
786 };
787