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