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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
18/* Intermediate node */
19#define LPM_TREE_NODE_FLAG_IM BIT(0)
20
21struct lpm_trie_node;
22
23struct lpm_trie_node {
24 struct rcu_head rcu;
25 struct lpm_trie_node __rcu *child[2];
26 u32 prefixlen;
27 u32 flags;
28 u8 data[0];
29};
30
31struct lpm_trie {
32 struct bpf_map map;
33 struct lpm_trie_node __rcu *root;
34 size_t n_entries;
35 size_t max_prefixlen;
36 size_t data_size;
37 raw_spinlock_t lock;
38};
39
40/* This trie implements a longest prefix match algorithm that can be used to
41 * match IP addresses to a stored set of ranges.
42 *
43 * Data stored in @data of struct bpf_lpm_key and struct lpm_trie_node is
44 * interpreted as big endian, so data[0] stores the most significant byte.
45 *
46 * Match ranges are internally stored in instances of struct lpm_trie_node
47 * which each contain their prefix length as well as two pointers that may
48 * lead to more nodes containing more specific matches. Each node also stores
49 * a value that is defined by and returned to userspace via the update_elem
50 * and lookup functions.
51 *
52 * For instance, let's start with a trie that was created with a prefix length
53 * of 32, so it can be used for IPv4 addresses, and one single element that
54 * matches 192.168.0.0/16. The data array would hence contain
55 * [0xc0, 0xa8, 0x00, 0x00] in big-endian notation. This documentation will
56 * stick to IP-address notation for readability though.
57 *
58 * As the trie is empty initially, the new node (1) will be places as root
59 * node, denoted as (R) in the example below. As there are no other node, both
60 * child pointers are %NULL.
61 *
62 * +----------------+
63 * | (1) (R) |
64 * | 192.168.0.0/16 |
65 * | value: 1 |
66 * | [0] [1] |
67 * +----------------+
68 *
69 * Next, let's add a new node (2) matching 192.168.0.0/24. As there is already
70 * a node with the same data and a smaller prefix (ie, a less specific one),
71 * node (2) will become a child of (1). In child index depends on the next bit
72 * that is outside of what (1) matches, and that bit is 0, so (2) will be
73 * child[0] of (1):
74 *
75 * +----------------+
76 * | (1) (R) |
77 * | 192.168.0.0/16 |
78 * | value: 1 |
79 * | [0] [1] |
80 * +----------------+
81 * |
82 * +----------------+
83 * | (2) |
84 * | 192.168.0.0/24 |
85 * | value: 2 |
86 * | [0] [1] |
87 * +----------------+
88 *
89 * The child[1] slot of (1) could be filled with another node which has bit #17
90 * (the next bit after the ones that (1) matches on) set to 1. For instance,
91 * 192.168.128.0/24:
92 *
93 * +----------------+
94 * | (1) (R) |
95 * | 192.168.0.0/16 |
96 * | value: 1 |
97 * | [0] [1] |
98 * +----------------+
99 * | |
100 * +----------------+ +------------------+
101 * | (2) | | (3) |
102 * | 192.168.0.0/24 | | 192.168.128.0/24 |
103 * | value: 2 | | value: 3 |
104 * | [0] [1] | | [0] [1] |
105 * +----------------+ +------------------+
106 *
107 * Let's add another node (4) to the game for 192.168.1.0/24. In order to place
108 * it, node (1) is looked at first, and because (4) of the semantics laid out
109 * above (bit #17 is 0), it would normally be attached to (1) as child[0].
110 * However, that slot is already allocated, so a new node is needed in between.
111 * That node does not have a value attached to it and it will never be
112 * returned to users as result of a lookup. It is only there to differentiate
113 * the traversal further. It will get a prefix as wide as necessary to
114 * distinguish its two children:
115 *
116 * +----------------+
117 * | (1) (R) |
118 * | 192.168.0.0/16 |
119 * | value: 1 |
120 * | [0] [1] |
121 * +----------------+
122 * | |
123 * +----------------+ +------------------+
124 * | (4) (I) | | (3) |
125 * | 192.168.0.0/23 | | 192.168.128.0/24 |
126 * | value: --- | | value: 3 |
127 * | [0] [1] | | [0] [1] |
128 * +----------------+ +------------------+
129 * | |
130 * +----------------+ +----------------+
131 * | (2) | | (5) |
132 * | 192.168.0.0/24 | | 192.168.1.0/24 |
133 * | value: 2 | | value: 5 |
134 * | [0] [1] | | [0] [1] |
135 * +----------------+ +----------------+
136 *
137 * 192.168.1.1/32 would be a child of (5) etc.
138 *
139 * An intermediate node will be turned into a 'real' node on demand. In the
140 * example above, (4) would be re-used if 192.168.0.0/23 is added to the trie.
141 *
142 * A fully populated trie would have a height of 32 nodes, as the trie was
143 * created with a prefix length of 32.
144 *
145 * The lookup starts at the root node. If the current node matches and if there
146 * is a child that can be used to become more specific, the trie is traversed
147 * downwards. The last node in the traversal that is a non-intermediate one is
148 * returned.
149 */
150
151static inline int extract_bit(const u8 *data, size_t index)
152{
153 return !!(data[index / 8] & (1 << (7 - (index % 8))));
154}
155
156/**
157 * longest_prefix_match() - determine the longest prefix
158 * @trie: The trie to get internal sizes from
159 * @node: The node to operate on
160 * @key: The key to compare to @node
161 *
162 * Determine the longest prefix of @node that matches the bits in @key.
163 */
164static size_t longest_prefix_match(const struct lpm_trie *trie,
165 const struct lpm_trie_node *node,
166 const struct bpf_lpm_trie_key *key)
167{
168 u32 limit = min(node->prefixlen, key->prefixlen);
169 u32 prefixlen = 0, i = 0;
170
171 BUILD_BUG_ON(offsetof(struct lpm_trie_node, data) % sizeof(u32));
172 BUILD_BUG_ON(offsetof(struct bpf_lpm_trie_key, data) % sizeof(u32));
173
174#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && defined(CONFIG_64BIT)
175
176 /* data_size >= 16 has very small probability.
177 * We do not use a loop for optimal code generation.
178 */
179 if (trie->data_size >= 8) {
180 u64 diff = be64_to_cpu(*(__be64 *)node->data ^
181 *(__be64 *)key->data);
182
183 prefixlen = 64 - fls64(diff);
184 if (prefixlen >= limit)
185 return limit;
186 if (diff)
187 return prefixlen;
188 i = 8;
189 }
190#endif
191
192 while (trie->data_size >= i + 4) {
193 u32 diff = be32_to_cpu(*(__be32 *)&node->data[i] ^
194 *(__be32 *)&key->data[i]);
195
196 prefixlen += 32 - fls(diff);
197 if (prefixlen >= limit)
198 return limit;
199 if (diff)
200 return prefixlen;
201 i += 4;
202 }
203
204 if (trie->data_size >= i + 2) {
205 u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] ^
206 *(__be16 *)&key->data[i]);
207
208 prefixlen += 16 - fls(diff);
209 if (prefixlen >= limit)
210 return limit;
211 if (diff)
212 return prefixlen;
213 i += 2;
214 }
215
216 if (trie->data_size >= i + 1) {
217 prefixlen += 8 - fls(node->data[i] ^ key->data[i]);
218
219 if (prefixlen >= limit)
220 return limit;
221 }
222
223 return prefixlen;
224}
225
226/* Called from syscall or from eBPF program */
227static void *trie_lookup_elem(struct bpf_map *map, void *_key)
228{
229 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
230 struct lpm_trie_node *node, *found = NULL;
231 struct bpf_lpm_trie_key *key = _key;
232
233 /* Start walking the trie from the root node ... */
234
235 for (node = rcu_dereference(trie->root); node;) {
236 unsigned int next_bit;
237 size_t matchlen;
238
239 /* Determine the longest prefix of @node that matches @key.
240 * If it's the maximum possible prefix for this trie, we have
241 * an exact match and can return it directly.
242 */
243 matchlen = longest_prefix_match(trie, node, key);
244 if (matchlen == trie->max_prefixlen) {
245 found = node;
246 break;
247 }
248
249 /* If the number of bits that match is smaller than the prefix
250 * length of @node, bail out and return the node we have seen
251 * last in the traversal (ie, the parent).
252 */
253 if (matchlen < node->prefixlen)
254 break;
255
256 /* Consider this node as return candidate unless it is an
257 * artificially added intermediate one.
258 */
259 if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
260 found = node;
261
262 /* If the node match is fully satisfied, let's see if we can
263 * become more specific. Determine the next bit in the key and
264 * traverse down.
265 */
266 next_bit = extract_bit(key->data, node->prefixlen);
267 node = rcu_dereference(node->child[next_bit]);
268 }
269
270 if (!found)
271 return NULL;
272
273 return found->data + trie->data_size;
274}
275
276static struct lpm_trie_node *lpm_trie_node_alloc(const struct lpm_trie *trie,
277 const void *value)
278{
279 struct lpm_trie_node *node;
280 size_t size = sizeof(struct lpm_trie_node) + trie->data_size;
281
282 if (value)
283 size += trie->map.value_size;
284
285 node = kmalloc_node(size, GFP_ATOMIC | __GFP_NOWARN,
286 trie->map.numa_node);
287 if (!node)
288 return NULL;
289
290 node->flags = 0;
291
292 if (value)
293 memcpy(node->data + trie->data_size, value,
294 trie->map.value_size);
295
296 return node;
297}
298
299/* Called from syscall or from eBPF program */
300static int trie_update_elem(struct bpf_map *map,
301 void *_key, void *value, u64 flags)
302{
303 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
304 struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL;
305 struct lpm_trie_node __rcu **slot;
306 struct bpf_lpm_trie_key *key = _key;
307 unsigned long irq_flags;
308 unsigned int next_bit;
309 size_t matchlen = 0;
310 int ret = 0;
311
312 if (unlikely(flags > BPF_EXIST))
313 return -EINVAL;
314
315 if (key->prefixlen > trie->max_prefixlen)
316 return -EINVAL;
317
318 raw_spin_lock_irqsave(&trie->lock, irq_flags);
319
320 /* Allocate and fill a new node */
321
322 if (trie->n_entries == trie->map.max_entries) {
323 ret = -ENOSPC;
324 goto out;
325 }
326
327 new_node = lpm_trie_node_alloc(trie, value);
328 if (!new_node) {
329 ret = -ENOMEM;
330 goto out;
331 }
332
333 trie->n_entries++;
334
335 new_node->prefixlen = key->prefixlen;
336 RCU_INIT_POINTER(new_node->child[0], NULL);
337 RCU_INIT_POINTER(new_node->child[1], NULL);
338 memcpy(new_node->data, key->data, trie->data_size);
339
340 /* Now find a slot to attach the new node. To do that, walk the tree
341 * from the root and match as many bits as possible for each node until
342 * we either find an empty slot or a slot that needs to be replaced by
343 * an intermediate node.
344 */
345 slot = &trie->root;
346
347 while ((node = rcu_dereference_protected(*slot,
348 lockdep_is_held(&trie->lock)))) {
349 matchlen = longest_prefix_match(trie, node, key);
350
351 if (node->prefixlen != matchlen ||
352 node->prefixlen == key->prefixlen ||
353 node->prefixlen == trie->max_prefixlen)
354 break;
355
356 next_bit = extract_bit(key->data, node->prefixlen);
357 slot = &node->child[next_bit];
358 }
359
360 /* If the slot is empty (a free child pointer or an empty root),
361 * simply assign the @new_node to that slot and be done.
362 */
363 if (!node) {
364 rcu_assign_pointer(*slot, new_node);
365 goto out;
366 }
367
368 /* If the slot we picked already exists, replace it with @new_node
369 * which already has the correct data array set.
370 */
371 if (node->prefixlen == matchlen) {
372 new_node->child[0] = node->child[0];
373 new_node->child[1] = node->child[1];
374
375 if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
376 trie->n_entries--;
377
378 rcu_assign_pointer(*slot, new_node);
379 kfree_rcu(node, rcu);
380
381 goto out;
382 }
383
384 /* If the new node matches the prefix completely, it must be inserted
385 * as an ancestor. Simply insert it between @node and *@slot.
386 */
387 if (matchlen == key->prefixlen) {
388 next_bit = extract_bit(node->data, matchlen);
389 rcu_assign_pointer(new_node->child[next_bit], node);
390 rcu_assign_pointer(*slot, new_node);
391 goto out;
392 }
393
394 im_node = lpm_trie_node_alloc(trie, NULL);
395 if (!im_node) {
396 ret = -ENOMEM;
397 goto out;
398 }
399
400 im_node->prefixlen = matchlen;
401 im_node->flags |= LPM_TREE_NODE_FLAG_IM;
402 memcpy(im_node->data, node->data, trie->data_size);
403
404 /* Now determine which child to install in which slot */
405 if (extract_bit(key->data, matchlen)) {
406 rcu_assign_pointer(im_node->child[0], node);
407 rcu_assign_pointer(im_node->child[1], new_node);
408 } else {
409 rcu_assign_pointer(im_node->child[0], new_node);
410 rcu_assign_pointer(im_node->child[1], node);
411 }
412
413 /* Finally, assign the intermediate node to the determined spot */
414 rcu_assign_pointer(*slot, im_node);
415
416out:
417 if (ret) {
418 if (new_node)
419 trie->n_entries--;
420
421 kfree(new_node);
422 kfree(im_node);
423 }
424
425 raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
426
427 return ret;
428}
429
430/* Called from syscall or from eBPF program */
431static int trie_delete_elem(struct bpf_map *map, void *_key)
432{
433 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
434 struct bpf_lpm_trie_key *key = _key;
435 struct lpm_trie_node __rcu **trim, **trim2;
436 struct lpm_trie_node *node, *parent;
437 unsigned long irq_flags;
438 unsigned int next_bit;
439 size_t matchlen = 0;
440 int ret = 0;
441
442 if (key->prefixlen > trie->max_prefixlen)
443 return -EINVAL;
444
445 raw_spin_lock_irqsave(&trie->lock, irq_flags);
446
447 /* Walk the tree looking for an exact key/length match and keeping
448 * track of the path we traverse. We will need to know the node
449 * we wish to delete, and the slot that points to the node we want
450 * to delete. We may also need to know the nodes parent and the
451 * slot that contains it.
452 */
453 trim = &trie->root;
454 trim2 = trim;
455 parent = NULL;
456 while ((node = rcu_dereference_protected(
457 *trim, lockdep_is_held(&trie->lock)))) {
458 matchlen = longest_prefix_match(trie, node, key);
459
460 if (node->prefixlen != matchlen ||
461 node->prefixlen == key->prefixlen)
462 break;
463
464 parent = node;
465 trim2 = trim;
466 next_bit = extract_bit(key->data, node->prefixlen);
467 trim = &node->child[next_bit];
468 }
469
470 if (!node || node->prefixlen != key->prefixlen ||
471 node->prefixlen != matchlen ||
472 (node->flags & LPM_TREE_NODE_FLAG_IM)) {
473 ret = -ENOENT;
474 goto out;
475 }
476
477 trie->n_entries--;
478
479 /* If the node we are removing has two children, simply mark it
480 * as intermediate and we are done.
481 */
482 if (rcu_access_pointer(node->child[0]) &&
483 rcu_access_pointer(node->child[1])) {
484 node->flags |= LPM_TREE_NODE_FLAG_IM;
485 goto out;
486 }
487
488 /* If the parent of the node we are about to delete is an intermediate
489 * node, and the deleted node doesn't have any children, we can delete
490 * the intermediate parent as well and promote its other child
491 * up the tree. Doing this maintains the invariant that all
492 * intermediate nodes have exactly 2 children and that there are no
493 * unnecessary intermediate nodes in the tree.
494 */
495 if (parent && (parent->flags & LPM_TREE_NODE_FLAG_IM) &&
496 !node->child[0] && !node->child[1]) {
497 if (node == rcu_access_pointer(parent->child[0]))
498 rcu_assign_pointer(
499 *trim2, rcu_access_pointer(parent->child[1]));
500 else
501 rcu_assign_pointer(
502 *trim2, rcu_access_pointer(parent->child[0]));
503 kfree_rcu(parent, rcu);
504 kfree_rcu(node, rcu);
505 goto out;
506 }
507
508 /* The node we are removing has either zero or one child. If there
509 * is a child, move it into the removed node's slot then delete
510 * the node. Otherwise just clear the slot and delete the node.
511 */
512 if (node->child[0])
513 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[0]));
514 else if (node->child[1])
515 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1]));
516 else
517 RCU_INIT_POINTER(*trim, NULL);
518 kfree_rcu(node, rcu);
519
520out:
521 raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
522
523 return ret;
524}
525
526#define LPM_DATA_SIZE_MAX 256
527#define LPM_DATA_SIZE_MIN 1
528
529#define LPM_VAL_SIZE_MAX (KMALLOC_MAX_SIZE - LPM_DATA_SIZE_MAX - \
530 sizeof(struct lpm_trie_node))
531#define LPM_VAL_SIZE_MIN 1
532
533#define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key) + (X))
534#define LPM_KEY_SIZE_MAX LPM_KEY_SIZE(LPM_DATA_SIZE_MAX)
535#define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN)
536
537#define LPM_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE | \
538 BPF_F_ACCESS_MASK)
539
540static struct bpf_map *trie_alloc(union bpf_attr *attr)
541{
542 struct lpm_trie *trie;
543 u64 cost = sizeof(*trie), cost_per_node;
544 int ret;
545
546 if (!capable(CAP_SYS_ADMIN))
547 return ERR_PTR(-EPERM);
548
549 /* check sanity of attributes */
550 if (attr->max_entries == 0 ||
551 !(attr->map_flags & BPF_F_NO_PREALLOC) ||
552 attr->map_flags & ~LPM_CREATE_FLAG_MASK ||
553 !bpf_map_flags_access_ok(attr->map_flags) ||
554 attr->key_size < LPM_KEY_SIZE_MIN ||
555 attr->key_size > LPM_KEY_SIZE_MAX ||
556 attr->value_size < LPM_VAL_SIZE_MIN ||
557 attr->value_size > LPM_VAL_SIZE_MAX)
558 return ERR_PTR(-EINVAL);
559
560 trie = kzalloc(sizeof(*trie), GFP_USER | __GFP_NOWARN);
561 if (!trie)
562 return ERR_PTR(-ENOMEM);
563
564 /* copy mandatory map attributes */
565 bpf_map_init_from_attr(&trie->map, attr);
566 trie->data_size = attr->key_size -
567 offsetof(struct bpf_lpm_trie_key, data);
568 trie->max_prefixlen = trie->data_size * 8;
569
570 cost_per_node = sizeof(struct lpm_trie_node) +
571 attr->value_size + trie->data_size;
572 cost += (u64) attr->max_entries * cost_per_node;
573
574 ret = bpf_map_charge_init(&trie->map.memory, cost);
575 if (ret)
576 goto out_err;
577
578 raw_spin_lock_init(&trie->lock);
579
580 return &trie->map;
581out_err:
582 kfree(trie);
583 return ERR_PTR(ret);
584}
585
586static void trie_free(struct bpf_map *map)
587{
588 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
589 struct lpm_trie_node __rcu **slot;
590 struct lpm_trie_node *node;
591
592 /* Wait for outstanding programs to complete
593 * update/lookup/delete/get_next_key and free the trie.
594 */
595 synchronize_rcu();
596
597 /* Always start at the root and walk down to a node that has no
598 * children. Then free that node, nullify its reference in the parent
599 * and start over.
600 */
601
602 for (;;) {
603 slot = &trie->root;
604
605 for (;;) {
606 node = rcu_dereference_protected(*slot, 1);
607 if (!node)
608 goto out;
609
610 if (rcu_access_pointer(node->child[0])) {
611 slot = &node->child[0];
612 continue;
613 }
614
615 if (rcu_access_pointer(node->child[1])) {
616 slot = &node->child[1];
617 continue;
618 }
619
620 kfree(node);
621 RCU_INIT_POINTER(*slot, NULL);
622 break;
623 }
624 }
625
626out:
627 kfree(trie);
628}
629
630static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key)
631{
632 struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root;
633 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
634 struct bpf_lpm_trie_key *key = _key, *next_key = _next_key;
635 struct lpm_trie_node **node_stack = NULL;
636 int err = 0, stack_ptr = -1;
637 unsigned int next_bit;
638 size_t matchlen;
639
640 /* The get_next_key follows postorder. For the 4 node example in
641 * the top of this file, the trie_get_next_key() returns the following
642 * one after another:
643 * 192.168.0.0/24
644 * 192.168.1.0/24
645 * 192.168.128.0/24
646 * 192.168.0.0/16
647 *
648 * The idea is to return more specific keys before less specific ones.
649 */
650
651 /* Empty trie */
652 search_root = rcu_dereference(trie->root);
653 if (!search_root)
654 return -ENOENT;
655
656 /* For invalid key, find the leftmost node in the trie */
657 if (!key || key->prefixlen > trie->max_prefixlen)
658 goto find_leftmost;
659
660 node_stack = kmalloc_array(trie->max_prefixlen,
661 sizeof(struct lpm_trie_node *),
662 GFP_ATOMIC | __GFP_NOWARN);
663 if (!node_stack)
664 return -ENOMEM;
665
666 /* Try to find the exact node for the given key */
667 for (node = search_root; node;) {
668 node_stack[++stack_ptr] = node;
669 matchlen = longest_prefix_match(trie, node, key);
670 if (node->prefixlen != matchlen ||
671 node->prefixlen == key->prefixlen)
672 break;
673
674 next_bit = extract_bit(key->data, node->prefixlen);
675 node = rcu_dereference(node->child[next_bit]);
676 }
677 if (!node || node->prefixlen != key->prefixlen ||
678 (node->flags & LPM_TREE_NODE_FLAG_IM))
679 goto find_leftmost;
680
681 /* The node with the exactly-matching key has been found,
682 * find the first node in postorder after the matched node.
683 */
684 node = node_stack[stack_ptr];
685 while (stack_ptr > 0) {
686 parent = node_stack[stack_ptr - 1];
687 if (rcu_dereference(parent->child[0]) == node) {
688 search_root = rcu_dereference(parent->child[1]);
689 if (search_root)
690 goto find_leftmost;
691 }
692 if (!(parent->flags & LPM_TREE_NODE_FLAG_IM)) {
693 next_node = parent;
694 goto do_copy;
695 }
696
697 node = parent;
698 stack_ptr--;
699 }
700
701 /* did not find anything */
702 err = -ENOENT;
703 goto free_stack;
704
705find_leftmost:
706 /* Find the leftmost non-intermediate node, all intermediate nodes
707 * have exact two children, so this function will never return NULL.
708 */
709 for (node = search_root; node;) {
710 if (node->flags & LPM_TREE_NODE_FLAG_IM) {
711 node = rcu_dereference(node->child[0]);
712 } else {
713 next_node = node;
714 node = rcu_dereference(node->child[0]);
715 if (!node)
716 node = rcu_dereference(next_node->child[1]);
717 }
718 }
719do_copy:
720 next_key->prefixlen = next_node->prefixlen;
721 memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key, data),
722 next_node->data, trie->data_size);
723free_stack:
724 kfree(node_stack);
725 return err;
726}
727
728static int trie_check_btf(const struct bpf_map *map,
729 const struct btf *btf,
730 const struct btf_type *key_type,
731 const struct btf_type *value_type)
732{
733 /* Keys must have struct bpf_lpm_trie_key embedded. */
734 return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ?
735 -EINVAL : 0;
736}
737
738const struct bpf_map_ops trie_map_ops = {
739 .map_alloc = trie_alloc,
740 .map_free = trie_free,
741 .map_get_next_key = trie_get_next_key,
742 .map_lookup_elem = trie_lookup_elem,
743 .map_update_elem = trie_update_elem,
744 .map_delete_elem = trie_delete_elem,
745 .map_check_btf = trie_check_btf,
746};
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
23struct lpm_trie_node;
24
25struct lpm_trie_node {
26 struct lpm_trie_node __rcu *child[2];
27 u32 prefixlen;
28 u32 flags;
29 u8 data[];
30};
31
32struct 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
153static 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 */
166static __always_inline
167size_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
229static 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 */
237static 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
291static struct lpm_trie_node *lpm_trie_node_alloc(struct lpm_trie *trie,
292 const void *value,
293 bool disable_migration)
294{
295 struct lpm_trie_node *node;
296
297 if (disable_migration)
298 migrate_disable();
299 node = bpf_mem_cache_alloc(&trie->ma);
300 if (disable_migration)
301 migrate_enable();
302
303 if (!node)
304 return NULL;
305
306 node->flags = 0;
307
308 if (value)
309 memcpy(node->data + trie->data_size, value,
310 trie->map.value_size);
311
312 return node;
313}
314
315static int trie_check_add_elem(struct lpm_trie *trie, u64 flags)
316{
317 if (flags == BPF_EXIST)
318 return -ENOENT;
319 if (trie->n_entries == trie->map.max_entries)
320 return -ENOSPC;
321 trie->n_entries++;
322 return 0;
323}
324
325/* Called from syscall or from eBPF program */
326static long trie_update_elem(struct bpf_map *map,
327 void *_key, void *value, u64 flags)
328{
329 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
330 struct lpm_trie_node *node, *im_node, *new_node;
331 struct lpm_trie_node *free_node = NULL;
332 struct lpm_trie_node __rcu **slot;
333 struct bpf_lpm_trie_key_u8 *key = _key;
334 unsigned long irq_flags;
335 unsigned int next_bit;
336 size_t matchlen = 0;
337 int ret = 0;
338
339 if (unlikely(flags > BPF_EXIST))
340 return -EINVAL;
341
342 if (key->prefixlen > trie->max_prefixlen)
343 return -EINVAL;
344
345 /* Allocate and fill a new node. Need to disable migration before
346 * invoking bpf_mem_cache_alloc().
347 */
348 new_node = lpm_trie_node_alloc(trie, value, true);
349 if (!new_node)
350 return -ENOMEM;
351
352 raw_spin_lock_irqsave(&trie->lock, irq_flags);
353
354 new_node->prefixlen = key->prefixlen;
355 RCU_INIT_POINTER(new_node->child[0], NULL);
356 RCU_INIT_POINTER(new_node->child[1], NULL);
357 memcpy(new_node->data, key->data, trie->data_size);
358
359 /* Now find a slot to attach the new node. To do that, walk the tree
360 * from the root and match as many bits as possible for each node until
361 * we either find an empty slot or a slot that needs to be replaced by
362 * an intermediate node.
363 */
364 slot = &trie->root;
365
366 while ((node = rcu_dereference_protected(*slot,
367 lockdep_is_held(&trie->lock)))) {
368 matchlen = longest_prefix_match(trie, node, key);
369
370 if (node->prefixlen != matchlen ||
371 node->prefixlen == key->prefixlen)
372 break;
373
374 next_bit = extract_bit(key->data, node->prefixlen);
375 slot = &node->child[next_bit];
376 }
377
378 /* If the slot is empty (a free child pointer or an empty root),
379 * simply assign the @new_node to that slot and be done.
380 */
381 if (!node) {
382 ret = trie_check_add_elem(trie, flags);
383 if (ret)
384 goto out;
385
386 rcu_assign_pointer(*slot, new_node);
387 goto out;
388 }
389
390 /* If the slot we picked already exists, replace it with @new_node
391 * which already has the correct data array set.
392 */
393 if (node->prefixlen == matchlen) {
394 if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) {
395 if (flags == BPF_NOEXIST) {
396 ret = -EEXIST;
397 goto out;
398 }
399 } else {
400 ret = trie_check_add_elem(trie, flags);
401 if (ret)
402 goto out;
403 }
404
405 new_node->child[0] = node->child[0];
406 new_node->child[1] = node->child[1];
407
408 rcu_assign_pointer(*slot, new_node);
409 free_node = node;
410
411 goto out;
412 }
413
414 ret = trie_check_add_elem(trie, flags);
415 if (ret)
416 goto out;
417
418 /* If the new node matches the prefix completely, it must be inserted
419 * as an ancestor. Simply insert it between @node and *@slot.
420 */
421 if (matchlen == key->prefixlen) {
422 next_bit = extract_bit(node->data, matchlen);
423 rcu_assign_pointer(new_node->child[next_bit], node);
424 rcu_assign_pointer(*slot, new_node);
425 goto out;
426 }
427
428 /* migration is disabled within the locked scope */
429 im_node = lpm_trie_node_alloc(trie, NULL, false);
430 if (!im_node) {
431 trie->n_entries--;
432 ret = -ENOMEM;
433 goto out;
434 }
435
436 im_node->prefixlen = matchlen;
437 im_node->flags |= LPM_TREE_NODE_FLAG_IM;
438 memcpy(im_node->data, node->data, trie->data_size);
439
440 /* Now determine which child to install in which slot */
441 if (extract_bit(key->data, matchlen)) {
442 rcu_assign_pointer(im_node->child[0], node);
443 rcu_assign_pointer(im_node->child[1], new_node);
444 } else {
445 rcu_assign_pointer(im_node->child[0], new_node);
446 rcu_assign_pointer(im_node->child[1], node);
447 }
448
449 /* Finally, assign the intermediate node to the determined slot */
450 rcu_assign_pointer(*slot, im_node);
451
452out:
453 raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
454
455 migrate_disable();
456 if (ret)
457 bpf_mem_cache_free(&trie->ma, new_node);
458 bpf_mem_cache_free_rcu(&trie->ma, free_node);
459 migrate_enable();
460
461 return ret;
462}
463
464/* Called from syscall or from eBPF program */
465static long trie_delete_elem(struct bpf_map *map, void *_key)
466{
467 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
468 struct lpm_trie_node *free_node = NULL, *free_parent = NULL;
469 struct bpf_lpm_trie_key_u8 *key = _key;
470 struct lpm_trie_node __rcu **trim, **trim2;
471 struct lpm_trie_node *node, *parent;
472 unsigned long irq_flags;
473 unsigned int next_bit;
474 size_t matchlen = 0;
475 int ret = 0;
476
477 if (key->prefixlen > trie->max_prefixlen)
478 return -EINVAL;
479
480 raw_spin_lock_irqsave(&trie->lock, irq_flags);
481
482 /* Walk the tree looking for an exact key/length match and keeping
483 * track of the path we traverse. We will need to know the node
484 * we wish to delete, and the slot that points to the node we want
485 * to delete. We may also need to know the nodes parent and the
486 * slot that contains it.
487 */
488 trim = &trie->root;
489 trim2 = trim;
490 parent = NULL;
491 while ((node = rcu_dereference_protected(
492 *trim, lockdep_is_held(&trie->lock)))) {
493 matchlen = longest_prefix_match(trie, node, key);
494
495 if (node->prefixlen != matchlen ||
496 node->prefixlen == key->prefixlen)
497 break;
498
499 parent = node;
500 trim2 = trim;
501 next_bit = extract_bit(key->data, node->prefixlen);
502 trim = &node->child[next_bit];
503 }
504
505 if (!node || node->prefixlen != key->prefixlen ||
506 node->prefixlen != matchlen ||
507 (node->flags & LPM_TREE_NODE_FLAG_IM)) {
508 ret = -ENOENT;
509 goto out;
510 }
511
512 trie->n_entries--;
513
514 /* If the node we are removing has two children, simply mark it
515 * as intermediate and we are done.
516 */
517 if (rcu_access_pointer(node->child[0]) &&
518 rcu_access_pointer(node->child[1])) {
519 node->flags |= LPM_TREE_NODE_FLAG_IM;
520 goto out;
521 }
522
523 /* If the parent of the node we are about to delete is an intermediate
524 * node, and the deleted node doesn't have any children, we can delete
525 * the intermediate parent as well and promote its other child
526 * up the tree. Doing this maintains the invariant that all
527 * intermediate nodes have exactly 2 children and that there are no
528 * unnecessary intermediate nodes in the tree.
529 */
530 if (parent && (parent->flags & LPM_TREE_NODE_FLAG_IM) &&
531 !node->child[0] && !node->child[1]) {
532 if (node == rcu_access_pointer(parent->child[0]))
533 rcu_assign_pointer(
534 *trim2, rcu_access_pointer(parent->child[1]));
535 else
536 rcu_assign_pointer(
537 *trim2, rcu_access_pointer(parent->child[0]));
538 free_parent = parent;
539 free_node = node;
540 goto out;
541 }
542
543 /* The node we are removing has either zero or one child. If there
544 * is a child, move it into the removed node's slot then delete
545 * the node. Otherwise just clear the slot and delete the node.
546 */
547 if (node->child[0])
548 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[0]));
549 else if (node->child[1])
550 rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1]));
551 else
552 RCU_INIT_POINTER(*trim, NULL);
553 free_node = node;
554
555out:
556 raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
557
558 migrate_disable();
559 bpf_mem_cache_free_rcu(&trie->ma, free_parent);
560 bpf_mem_cache_free_rcu(&trie->ma, free_node);
561 migrate_enable();
562
563 return ret;
564}
565
566#define LPM_DATA_SIZE_MAX 256
567#define LPM_DATA_SIZE_MIN 1
568
569#define LPM_VAL_SIZE_MAX (KMALLOC_MAX_SIZE - LPM_DATA_SIZE_MAX - \
570 sizeof(struct lpm_trie_node))
571#define LPM_VAL_SIZE_MIN 1
572
573#define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key_u8) + (X))
574#define LPM_KEY_SIZE_MAX LPM_KEY_SIZE(LPM_DATA_SIZE_MAX)
575#define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN)
576
577#define LPM_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE | \
578 BPF_F_ACCESS_MASK)
579
580static struct bpf_map *trie_alloc(union bpf_attr *attr)
581{
582 struct lpm_trie *trie;
583 size_t leaf_size;
584 int err;
585
586 /* check sanity of attributes */
587 if (attr->max_entries == 0 ||
588 !(attr->map_flags & BPF_F_NO_PREALLOC) ||
589 attr->map_flags & ~LPM_CREATE_FLAG_MASK ||
590 !bpf_map_flags_access_ok(attr->map_flags) ||
591 attr->key_size < LPM_KEY_SIZE_MIN ||
592 attr->key_size > LPM_KEY_SIZE_MAX ||
593 attr->value_size < LPM_VAL_SIZE_MIN ||
594 attr->value_size > LPM_VAL_SIZE_MAX)
595 return ERR_PTR(-EINVAL);
596
597 trie = bpf_map_area_alloc(sizeof(*trie), NUMA_NO_NODE);
598 if (!trie)
599 return ERR_PTR(-ENOMEM);
600
601 /* copy mandatory map attributes */
602 bpf_map_init_from_attr(&trie->map, attr);
603 trie->data_size = attr->key_size -
604 offsetof(struct bpf_lpm_trie_key_u8, data);
605 trie->max_prefixlen = trie->data_size * 8;
606
607 raw_spin_lock_init(&trie->lock);
608
609 /* Allocate intermediate and leaf nodes from the same allocator */
610 leaf_size = sizeof(struct lpm_trie_node) + trie->data_size +
611 trie->map.value_size;
612 err = bpf_mem_alloc_init(&trie->ma, leaf_size, false);
613 if (err)
614 goto free_out;
615 return &trie->map;
616
617free_out:
618 bpf_map_area_free(trie);
619 return ERR_PTR(err);
620}
621
622static void trie_free(struct bpf_map *map)
623{
624 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
625 struct lpm_trie_node __rcu **slot;
626 struct lpm_trie_node *node;
627
628 /* Always start at the root and walk down to a node that has no
629 * children. Then free that node, nullify its reference in the parent
630 * and start over.
631 */
632
633 for (;;) {
634 slot = &trie->root;
635
636 for (;;) {
637 node = rcu_dereference_protected(*slot, 1);
638 if (!node)
639 goto out;
640
641 if (rcu_access_pointer(node->child[0])) {
642 slot = &node->child[0];
643 continue;
644 }
645
646 if (rcu_access_pointer(node->child[1])) {
647 slot = &node->child[1];
648 continue;
649 }
650
651 /* No bpf program may access the map, so freeing the
652 * node without waiting for the extra RCU GP.
653 */
654 bpf_mem_cache_raw_free(node);
655 RCU_INIT_POINTER(*slot, NULL);
656 break;
657 }
658 }
659
660out:
661 bpf_mem_alloc_destroy(&trie->ma);
662 bpf_map_area_free(trie);
663}
664
665static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key)
666{
667 struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root;
668 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
669 struct bpf_lpm_trie_key_u8 *key = _key, *next_key = _next_key;
670 struct lpm_trie_node **node_stack = NULL;
671 int err = 0, stack_ptr = -1;
672 unsigned int next_bit;
673 size_t matchlen = 0;
674
675 /* The get_next_key follows postorder. For the 4 node example in
676 * the top of this file, the trie_get_next_key() returns the following
677 * one after another:
678 * 192.168.0.0/24
679 * 192.168.1.0/24
680 * 192.168.128.0/24
681 * 192.168.0.0/16
682 *
683 * The idea is to return more specific keys before less specific ones.
684 */
685
686 /* Empty trie */
687 search_root = rcu_dereference(trie->root);
688 if (!search_root)
689 return -ENOENT;
690
691 /* For invalid key, find the leftmost node in the trie */
692 if (!key || key->prefixlen > trie->max_prefixlen)
693 goto find_leftmost;
694
695 node_stack = kmalloc_array(trie->max_prefixlen + 1,
696 sizeof(struct lpm_trie_node *),
697 GFP_ATOMIC | __GFP_NOWARN);
698 if (!node_stack)
699 return -ENOMEM;
700
701 /* Try to find the exact node for the given key */
702 for (node = search_root; node;) {
703 node_stack[++stack_ptr] = node;
704 matchlen = longest_prefix_match(trie, node, key);
705 if (node->prefixlen != matchlen ||
706 node->prefixlen == key->prefixlen)
707 break;
708
709 next_bit = extract_bit(key->data, node->prefixlen);
710 node = rcu_dereference(node->child[next_bit]);
711 }
712 if (!node || node->prefixlen != matchlen ||
713 (node->flags & LPM_TREE_NODE_FLAG_IM))
714 goto find_leftmost;
715
716 /* The node with the exactly-matching key has been found,
717 * find the first node in postorder after the matched node.
718 */
719 node = node_stack[stack_ptr];
720 while (stack_ptr > 0) {
721 parent = node_stack[stack_ptr - 1];
722 if (rcu_dereference(parent->child[0]) == node) {
723 search_root = rcu_dereference(parent->child[1]);
724 if (search_root)
725 goto find_leftmost;
726 }
727 if (!(parent->flags & LPM_TREE_NODE_FLAG_IM)) {
728 next_node = parent;
729 goto do_copy;
730 }
731
732 node = parent;
733 stack_ptr--;
734 }
735
736 /* did not find anything */
737 err = -ENOENT;
738 goto free_stack;
739
740find_leftmost:
741 /* Find the leftmost non-intermediate node, all intermediate nodes
742 * have exact two children, so this function will never return NULL.
743 */
744 for (node = search_root; node;) {
745 if (node->flags & LPM_TREE_NODE_FLAG_IM) {
746 node = rcu_dereference(node->child[0]);
747 } else {
748 next_node = node;
749 node = rcu_dereference(node->child[0]);
750 if (!node)
751 node = rcu_dereference(next_node->child[1]);
752 }
753 }
754do_copy:
755 next_key->prefixlen = next_node->prefixlen;
756 memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key_u8, data),
757 next_node->data, trie->data_size);
758free_stack:
759 kfree(node_stack);
760 return err;
761}
762
763static int trie_check_btf(const struct bpf_map *map,
764 const struct btf *btf,
765 const struct btf_type *key_type,
766 const struct btf_type *value_type)
767{
768 /* Keys must have struct bpf_lpm_trie_key_u8 embedded. */
769 return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ?
770 -EINVAL : 0;
771}
772
773static u64 trie_mem_usage(const struct bpf_map *map)
774{
775 struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
776 u64 elem_size;
777
778 elem_size = sizeof(struct lpm_trie_node) + trie->data_size +
779 trie->map.value_size;
780 return elem_size * READ_ONCE(trie->n_entries);
781}
782
783BTF_ID_LIST_SINGLE(trie_map_btf_ids, struct, lpm_trie)
784const struct bpf_map_ops trie_map_ops = {
785 .map_meta_equal = bpf_map_meta_equal,
786 .map_alloc = trie_alloc,
787 .map_free = trie_free,
788 .map_get_next_key = trie_get_next_key,
789 .map_lookup_elem = trie_lookup_elem,
790 .map_update_elem = trie_update_elem,
791 .map_delete_elem = trie_delete_elem,
792 .map_lookup_batch = generic_map_lookup_batch,
793 .map_update_batch = generic_map_update_batch,
794 .map_delete_batch = generic_map_delete_batch,
795 .map_check_btf = trie_check_btf,
796 .map_mem_usage = trie_mem_usage,
797 .map_btf_id = &trie_map_btf_ids[0],
798};