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b95a5c4d DM |
1 | /* |
2 | * Longest prefix match list implementation | |
3 | * | |
4 | * Copyright (c) 2016,2017 Daniel Mack | |
5 | * Copyright (c) 2016 David Herrmann | |
6 | * | |
7 | * This file is subject to the terms and conditions of version 2 of the GNU | |
8 | * General Public License. See the file COPYING in the main directory of the | |
9 | * Linux distribution for more details. | |
10 | */ | |
11 | ||
12 | #include <linux/bpf.h> | |
e8d2bec0 | 13 | #include <linux/btf.h> |
b95a5c4d DM |
14 | #include <linux/err.h> |
15 | #include <linux/slab.h> | |
16 | #include <linux/spinlock.h> | |
17 | #include <linux/vmalloc.h> | |
18 | #include <net/ipv6.h> | |
e8d2bec0 | 19 | #include <uapi/linux/btf.h> |
b95a5c4d DM |
20 | |
21 | /* Intermediate node */ | |
22 | #define LPM_TREE_NODE_FLAG_IM BIT(0) | |
23 | ||
24 | struct lpm_trie_node; | |
25 | ||
26 | struct lpm_trie_node { | |
27 | struct rcu_head rcu; | |
28 | struct lpm_trie_node __rcu *child[2]; | |
29 | u32 prefixlen; | |
30 | u32 flags; | |
31 | u8 data[0]; | |
32 | }; | |
33 | ||
34 | struct lpm_trie { | |
35 | struct bpf_map map; | |
36 | struct lpm_trie_node __rcu *root; | |
37 | size_t n_entries; | |
38 | size_t max_prefixlen; | |
39 | size_t data_size; | |
40 | raw_spinlock_t lock; | |
41 | }; | |
42 | ||
43 | /* This trie implements a longest prefix match algorithm that can be used to | |
44 | * match IP addresses to a stored set of ranges. | |
45 | * | |
46 | * Data stored in @data of struct bpf_lpm_key and struct lpm_trie_node is | |
47 | * interpreted as big endian, so data[0] stores the most significant byte. | |
48 | * | |
49 | * Match ranges are internally stored in instances of struct lpm_trie_node | |
50 | * which each contain their prefix length as well as two pointers that may | |
51 | * lead to more nodes containing more specific matches. Each node also stores | |
52 | * a value that is defined by and returned to userspace via the update_elem | |
53 | * and lookup functions. | |
54 | * | |
55 | * For instance, let's start with a trie that was created with a prefix length | |
56 | * of 32, so it can be used for IPv4 addresses, and one single element that | |
57 | * matches 192.168.0.0/16. The data array would hence contain | |
58 | * [0xc0, 0xa8, 0x00, 0x00] in big-endian notation. This documentation will | |
59 | * stick to IP-address notation for readability though. | |
60 | * | |
61 | * As the trie is empty initially, the new node (1) will be places as root | |
62 | * node, denoted as (R) in the example below. As there are no other node, both | |
63 | * child pointers are %NULL. | |
64 | * | |
65 | * +----------------+ | |
66 | * | (1) (R) | | |
67 | * | 192.168.0.0/16 | | |
68 | * | value: 1 | | |
69 | * | [0] [1] | | |
70 | * +----------------+ | |
71 | * | |
72 | * Next, let's add a new node (2) matching 192.168.0.0/24. As there is already | |
73 | * a node with the same data and a smaller prefix (ie, a less specific one), | |
74 | * node (2) will become a child of (1). In child index depends on the next bit | |
75 | * that is outside of what (1) matches, and that bit is 0, so (2) will be | |
76 | * child[0] of (1): | |
77 | * | |
78 | * +----------------+ | |
79 | * | (1) (R) | | |
80 | * | 192.168.0.0/16 | | |
81 | * | value: 1 | | |
82 | * | [0] [1] | | |
83 | * +----------------+ | |
84 | * | | |
85 | * +----------------+ | |
86 | * | (2) | | |
87 | * | 192.168.0.0/24 | | |
88 | * | value: 2 | | |
89 | * | [0] [1] | | |
90 | * +----------------+ | |
91 | * | |
92 | * The child[1] slot of (1) could be filled with another node which has bit #17 | |
93 | * (the next bit after the ones that (1) matches on) set to 1. For instance, | |
94 | * 192.168.128.0/24: | |
95 | * | |
96 | * +----------------+ | |
97 | * | (1) (R) | | |
98 | * | 192.168.0.0/16 | | |
99 | * | value: 1 | | |
100 | * | [0] [1] | | |
101 | * +----------------+ | |
102 | * | | | |
103 | * +----------------+ +------------------+ | |
104 | * | (2) | | (3) | | |
105 | * | 192.168.0.0/24 | | 192.168.128.0/24 | | |
106 | * | value: 2 | | value: 3 | | |
107 | * | [0] [1] | | [0] [1] | | |
108 | * +----------------+ +------------------+ | |
109 | * | |
110 | * Let's add another node (4) to the game for 192.168.1.0/24. In order to place | |
111 | * it, node (1) is looked at first, and because (4) of the semantics laid out | |
112 | * above (bit #17 is 0), it would normally be attached to (1) as child[0]. | |
113 | * However, that slot is already allocated, so a new node is needed in between. | |
114 | * That node does not have a value attached to it and it will never be | |
115 | * returned to users as result of a lookup. It is only there to differentiate | |
116 | * the traversal further. It will get a prefix as wide as necessary to | |
117 | * distinguish its two children: | |
118 | * | |
119 | * +----------------+ | |
120 | * | (1) (R) | | |
121 | * | 192.168.0.0/16 | | |
122 | * | value: 1 | | |
123 | * | [0] [1] | | |
124 | * +----------------+ | |
125 | * | | | |
126 | * +----------------+ +------------------+ | |
127 | * | (4) (I) | | (3) | | |
128 | * | 192.168.0.0/23 | | 192.168.128.0/24 | | |
129 | * | value: --- | | value: 3 | | |
130 | * | [0] [1] | | [0] [1] | | |
131 | * +----------------+ +------------------+ | |
132 | * | | | |
133 | * +----------------+ +----------------+ | |
134 | * | (2) | | (5) | | |
135 | * | 192.168.0.0/24 | | 192.168.1.0/24 | | |
136 | * | value: 2 | | value: 5 | | |
137 | * | [0] [1] | | [0] [1] | | |
138 | * +----------------+ +----------------+ | |
139 | * | |
140 | * 192.168.1.1/32 would be a child of (5) etc. | |
141 | * | |
142 | * An intermediate node will be turned into a 'real' node on demand. In the | |
143 | * example above, (4) would be re-used if 192.168.0.0/23 is added to the trie. | |
144 | * | |
145 | * A fully populated trie would have a height of 32 nodes, as the trie was | |
146 | * created with a prefix length of 32. | |
147 | * | |
148 | * The lookup starts at the root node. If the current node matches and if there | |
149 | * is a child that can be used to become more specific, the trie is traversed | |
150 | * downwards. The last node in the traversal that is a non-intermediate one is | |
151 | * returned. | |
152 | */ | |
153 | ||
154 | static inline int extract_bit(const u8 *data, size_t index) | |
155 | { | |
156 | return !!(data[index / 8] & (1 << (7 - (index % 8)))); | |
157 | } | |
158 | ||
159 | /** | |
160 | * longest_prefix_match() - determine the longest prefix | |
161 | * @trie: The trie to get internal sizes from | |
162 | * @node: The node to operate on | |
163 | * @key: The key to compare to @node | |
164 | * | |
165 | * Determine the longest prefix of @node that matches the bits in @key. | |
166 | */ | |
167 | static size_t longest_prefix_match(const struct lpm_trie *trie, | |
168 | const struct lpm_trie_node *node, | |
169 | const struct bpf_lpm_trie_key *key) | |
170 | { | |
171 | size_t prefixlen = 0; | |
172 | size_t i; | |
173 | ||
174 | for (i = 0; i < trie->data_size; i++) { | |
175 | size_t b; | |
176 | ||
177 | b = 8 - fls(node->data[i] ^ key->data[i]); | |
178 | prefixlen += b; | |
179 | ||
180 | if (prefixlen >= node->prefixlen || prefixlen >= key->prefixlen) | |
181 | return min(node->prefixlen, key->prefixlen); | |
182 | ||
183 | if (b < 8) | |
184 | break; | |
185 | } | |
186 | ||
187 | return prefixlen; | |
188 | } | |
189 | ||
190 | /* Called from syscall or from eBPF program */ | |
191 | static void *trie_lookup_elem(struct bpf_map *map, void *_key) | |
192 | { | |
193 | struct lpm_trie *trie = container_of(map, struct lpm_trie, map); | |
194 | struct lpm_trie_node *node, *found = NULL; | |
195 | struct bpf_lpm_trie_key *key = _key; | |
196 | ||
197 | /* Start walking the trie from the root node ... */ | |
198 | ||
199 | for (node = rcu_dereference(trie->root); node;) { | |
200 | unsigned int next_bit; | |
201 | size_t matchlen; | |
202 | ||
203 | /* Determine the longest prefix of @node that matches @key. | |
204 | * If it's the maximum possible prefix for this trie, we have | |
205 | * an exact match and can return it directly. | |
206 | */ | |
207 | matchlen = longest_prefix_match(trie, node, key); | |
208 | if (matchlen == trie->max_prefixlen) { | |
209 | found = node; | |
210 | break; | |
211 | } | |
212 | ||
213 | /* If the number of bits that match is smaller than the prefix | |
214 | * length of @node, bail out and return the node we have seen | |
215 | * last in the traversal (ie, the parent). | |
216 | */ | |
217 | if (matchlen < node->prefixlen) | |
218 | break; | |
219 | ||
220 | /* Consider this node as return candidate unless it is an | |
221 | * artificially added intermediate one. | |
222 | */ | |
223 | if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) | |
224 | found = node; | |
225 | ||
226 | /* If the node match is fully satisfied, let's see if we can | |
227 | * become more specific. Determine the next bit in the key and | |
228 | * traverse down. | |
229 | */ | |
230 | next_bit = extract_bit(key->data, node->prefixlen); | |
231 | node = rcu_dereference(node->child[next_bit]); | |
232 | } | |
233 | ||
234 | if (!found) | |
235 | return NULL; | |
236 | ||
237 | return found->data + trie->data_size; | |
238 | } | |
239 | ||
240 | static struct lpm_trie_node *lpm_trie_node_alloc(const struct lpm_trie *trie, | |
241 | const void *value) | |
242 | { | |
243 | struct lpm_trie_node *node; | |
244 | size_t size = sizeof(struct lpm_trie_node) + trie->data_size; | |
245 | ||
246 | if (value) | |
247 | size += trie->map.value_size; | |
248 | ||
96eabe7a MKL |
249 | node = kmalloc_node(size, GFP_ATOMIC | __GFP_NOWARN, |
250 | trie->map.numa_node); | |
b95a5c4d DM |
251 | if (!node) |
252 | return NULL; | |
253 | ||
254 | node->flags = 0; | |
255 | ||
256 | if (value) | |
257 | memcpy(node->data + trie->data_size, value, | |
258 | trie->map.value_size); | |
259 | ||
260 | return node; | |
261 | } | |
262 | ||
263 | /* Called from syscall or from eBPF program */ | |
264 | static int trie_update_elem(struct bpf_map *map, | |
265 | void *_key, void *value, u64 flags) | |
266 | { | |
267 | struct lpm_trie *trie = container_of(map, struct lpm_trie, map); | |
d140199a | 268 | struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL; |
b95a5c4d DM |
269 | struct lpm_trie_node __rcu **slot; |
270 | struct bpf_lpm_trie_key *key = _key; | |
271 | unsigned long irq_flags; | |
272 | unsigned int next_bit; | |
273 | size_t matchlen = 0; | |
274 | int ret = 0; | |
275 | ||
276 | if (unlikely(flags > BPF_EXIST)) | |
277 | return -EINVAL; | |
278 | ||
279 | if (key->prefixlen > trie->max_prefixlen) | |
280 | return -EINVAL; | |
281 | ||
282 | raw_spin_lock_irqsave(&trie->lock, irq_flags); | |
283 | ||
284 | /* Allocate and fill a new node */ | |
285 | ||
286 | if (trie->n_entries == trie->map.max_entries) { | |
287 | ret = -ENOSPC; | |
288 | goto out; | |
289 | } | |
290 | ||
291 | new_node = lpm_trie_node_alloc(trie, value); | |
292 | if (!new_node) { | |
293 | ret = -ENOMEM; | |
294 | goto out; | |
295 | } | |
296 | ||
297 | trie->n_entries++; | |
298 | ||
299 | new_node->prefixlen = key->prefixlen; | |
300 | RCU_INIT_POINTER(new_node->child[0], NULL); | |
301 | RCU_INIT_POINTER(new_node->child[1], NULL); | |
302 | memcpy(new_node->data, key->data, trie->data_size); | |
303 | ||
304 | /* Now find a slot to attach the new node. To do that, walk the tree | |
305 | * from the root and match as many bits as possible for each node until | |
306 | * we either find an empty slot or a slot that needs to be replaced by | |
307 | * an intermediate node. | |
308 | */ | |
309 | slot = &trie->root; | |
310 | ||
311 | while ((node = rcu_dereference_protected(*slot, | |
312 | lockdep_is_held(&trie->lock)))) { | |
313 | matchlen = longest_prefix_match(trie, node, key); | |
314 | ||
315 | if (node->prefixlen != matchlen || | |
316 | node->prefixlen == key->prefixlen || | |
317 | node->prefixlen == trie->max_prefixlen) | |
318 | break; | |
319 | ||
320 | next_bit = extract_bit(key->data, node->prefixlen); | |
321 | slot = &node->child[next_bit]; | |
322 | } | |
323 | ||
324 | /* If the slot is empty (a free child pointer or an empty root), | |
325 | * simply assign the @new_node to that slot and be done. | |
326 | */ | |
327 | if (!node) { | |
328 | rcu_assign_pointer(*slot, new_node); | |
329 | goto out; | |
330 | } | |
331 | ||
332 | /* If the slot we picked already exists, replace it with @new_node | |
333 | * which already has the correct data array set. | |
334 | */ | |
335 | if (node->prefixlen == matchlen) { | |
336 | new_node->child[0] = node->child[0]; | |
337 | new_node->child[1] = node->child[1]; | |
338 | ||
339 | if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) | |
340 | trie->n_entries--; | |
341 | ||
342 | rcu_assign_pointer(*slot, new_node); | |
343 | kfree_rcu(node, rcu); | |
344 | ||
345 | goto out; | |
346 | } | |
347 | ||
348 | /* If the new node matches the prefix completely, it must be inserted | |
349 | * as an ancestor. Simply insert it between @node and *@slot. | |
350 | */ | |
351 | if (matchlen == key->prefixlen) { | |
352 | next_bit = extract_bit(node->data, matchlen); | |
353 | rcu_assign_pointer(new_node->child[next_bit], node); | |
354 | rcu_assign_pointer(*slot, new_node); | |
355 | goto out; | |
356 | } | |
357 | ||
358 | im_node = lpm_trie_node_alloc(trie, NULL); | |
359 | if (!im_node) { | |
360 | ret = -ENOMEM; | |
361 | goto out; | |
362 | } | |
363 | ||
364 | im_node->prefixlen = matchlen; | |
365 | im_node->flags |= LPM_TREE_NODE_FLAG_IM; | |
366 | memcpy(im_node->data, node->data, trie->data_size); | |
367 | ||
368 | /* Now determine which child to install in which slot */ | |
369 | if (extract_bit(key->data, matchlen)) { | |
370 | rcu_assign_pointer(im_node->child[0], node); | |
371 | rcu_assign_pointer(im_node->child[1], new_node); | |
372 | } else { | |
373 | rcu_assign_pointer(im_node->child[0], new_node); | |
374 | rcu_assign_pointer(im_node->child[1], node); | |
375 | } | |
376 | ||
377 | /* Finally, assign the intermediate node to the determined spot */ | |
378 | rcu_assign_pointer(*slot, im_node); | |
379 | ||
380 | out: | |
381 | if (ret) { | |
382 | if (new_node) | |
383 | trie->n_entries--; | |
384 | ||
385 | kfree(new_node); | |
386 | kfree(im_node); | |
387 | } | |
388 | ||
389 | raw_spin_unlock_irqrestore(&trie->lock, irq_flags); | |
390 | ||
391 | return ret; | |
392 | } | |
393 | ||
e454cf59 CG |
394 | /* Called from syscall or from eBPF program */ |
395 | static int trie_delete_elem(struct bpf_map *map, void *_key) | |
b95a5c4d | 396 | { |
e454cf59 CG |
397 | struct lpm_trie *trie = container_of(map, struct lpm_trie, map); |
398 | struct bpf_lpm_trie_key *key = _key; | |
b5d7388f CG |
399 | struct lpm_trie_node __rcu **trim, **trim2; |
400 | struct lpm_trie_node *node, *parent; | |
e454cf59 CG |
401 | unsigned long irq_flags; |
402 | unsigned int next_bit; | |
403 | size_t matchlen = 0; | |
404 | int ret = 0; | |
405 | ||
406 | if (key->prefixlen > trie->max_prefixlen) | |
407 | return -EINVAL; | |
408 | ||
409 | raw_spin_lock_irqsave(&trie->lock, irq_flags); | |
410 | ||
411 | /* Walk the tree looking for an exact key/length match and keeping | |
b5d7388f CG |
412 | * track of the path we traverse. We will need to know the node |
413 | * we wish to delete, and the slot that points to the node we want | |
414 | * to delete. We may also need to know the nodes parent and the | |
415 | * slot that contains it. | |
e454cf59 CG |
416 | */ |
417 | trim = &trie->root; | |
b5d7388f CG |
418 | trim2 = trim; |
419 | parent = NULL; | |
420 | while ((node = rcu_dereference_protected( | |
421 | *trim, lockdep_is_held(&trie->lock)))) { | |
e454cf59 CG |
422 | matchlen = longest_prefix_match(trie, node, key); |
423 | ||
424 | if (node->prefixlen != matchlen || | |
425 | node->prefixlen == key->prefixlen) | |
426 | break; | |
427 | ||
b5d7388f CG |
428 | parent = node; |
429 | trim2 = trim; | |
e454cf59 | 430 | next_bit = extract_bit(key->data, node->prefixlen); |
b5d7388f | 431 | trim = &node->child[next_bit]; |
e454cf59 CG |
432 | } |
433 | ||
434 | if (!node || node->prefixlen != key->prefixlen || | |
435 | (node->flags & LPM_TREE_NODE_FLAG_IM)) { | |
436 | ret = -ENOENT; | |
437 | goto out; | |
438 | } | |
439 | ||
440 | trie->n_entries--; | |
441 | ||
b5d7388f | 442 | /* If the node we are removing has two children, simply mark it |
e454cf59 CG |
443 | * as intermediate and we are done. |
444 | */ | |
b5d7388f | 445 | if (rcu_access_pointer(node->child[0]) && |
e454cf59 CG |
446 | rcu_access_pointer(node->child[1])) { |
447 | node->flags |= LPM_TREE_NODE_FLAG_IM; | |
448 | goto out; | |
449 | } | |
450 | ||
b5d7388f CG |
451 | /* If the parent of the node we are about to delete is an intermediate |
452 | * node, and the deleted node doesn't have any children, we can delete | |
453 | * the intermediate parent as well and promote its other child | |
454 | * up the tree. Doing this maintains the invariant that all | |
455 | * intermediate nodes have exactly 2 children and that there are no | |
456 | * unnecessary intermediate nodes in the tree. | |
e454cf59 | 457 | */ |
b5d7388f CG |
458 | if (parent && (parent->flags & LPM_TREE_NODE_FLAG_IM) && |
459 | !node->child[0] && !node->child[1]) { | |
460 | if (node == rcu_access_pointer(parent->child[0])) | |
461 | rcu_assign_pointer( | |
462 | *trim2, rcu_access_pointer(parent->child[1])); | |
463 | else | |
464 | rcu_assign_pointer( | |
465 | *trim2, rcu_access_pointer(parent->child[0])); | |
466 | kfree_rcu(parent, rcu); | |
e454cf59 | 467 | kfree_rcu(node, rcu); |
b5d7388f | 468 | goto out; |
e454cf59 CG |
469 | } |
470 | ||
b5d7388f CG |
471 | /* The node we are removing has either zero or one child. If there |
472 | * is a child, move it into the removed node's slot then delete | |
473 | * the node. Otherwise just clear the slot and delete the node. | |
474 | */ | |
475 | if (node->child[0]) | |
476 | rcu_assign_pointer(*trim, rcu_access_pointer(node->child[0])); | |
477 | else if (node->child[1]) | |
478 | rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1])); | |
479 | else | |
480 | RCU_INIT_POINTER(*trim, NULL); | |
481 | kfree_rcu(node, rcu); | |
482 | ||
e454cf59 CG |
483 | out: |
484 | raw_spin_unlock_irqrestore(&trie->lock, irq_flags); | |
485 | ||
486 | return ret; | |
b95a5c4d DM |
487 | } |
488 | ||
c502faf9 DB |
489 | #define LPM_DATA_SIZE_MAX 256 |
490 | #define LPM_DATA_SIZE_MIN 1 | |
491 | ||
492 | #define LPM_VAL_SIZE_MAX (KMALLOC_MAX_SIZE - LPM_DATA_SIZE_MAX - \ | |
493 | sizeof(struct lpm_trie_node)) | |
494 | #define LPM_VAL_SIZE_MIN 1 | |
495 | ||
496 | #define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key) + (X)) | |
497 | #define LPM_KEY_SIZE_MAX LPM_KEY_SIZE(LPM_DATA_SIZE_MAX) | |
498 | #define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN) | |
499 | ||
6e71b04a CF |
500 | #define LPM_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE | \ |
501 | BPF_F_RDONLY | BPF_F_WRONLY) | |
96eabe7a | 502 | |
b95a5c4d DM |
503 | static struct bpf_map *trie_alloc(union bpf_attr *attr) |
504 | { | |
b95a5c4d | 505 | struct lpm_trie *trie; |
c502faf9 | 506 | u64 cost = sizeof(*trie), cost_per_node; |
b95a5c4d DM |
507 | int ret; |
508 | ||
509 | if (!capable(CAP_SYS_ADMIN)) | |
510 | return ERR_PTR(-EPERM); | |
511 | ||
512 | /* check sanity of attributes */ | |
513 | if (attr->max_entries == 0 || | |
96eabe7a MKL |
514 | !(attr->map_flags & BPF_F_NO_PREALLOC) || |
515 | attr->map_flags & ~LPM_CREATE_FLAG_MASK || | |
c502faf9 DB |
516 | attr->key_size < LPM_KEY_SIZE_MIN || |
517 | attr->key_size > LPM_KEY_SIZE_MAX || | |
518 | attr->value_size < LPM_VAL_SIZE_MIN || | |
519 | attr->value_size > LPM_VAL_SIZE_MAX) | |
b95a5c4d DM |
520 | return ERR_PTR(-EINVAL); |
521 | ||
522 | trie = kzalloc(sizeof(*trie), GFP_USER | __GFP_NOWARN); | |
523 | if (!trie) | |
524 | return ERR_PTR(-ENOMEM); | |
525 | ||
526 | /* copy mandatory map attributes */ | |
bd475643 | 527 | bpf_map_init_from_attr(&trie->map, attr); |
b95a5c4d DM |
528 | trie->data_size = attr->key_size - |
529 | offsetof(struct bpf_lpm_trie_key, data); | |
530 | trie->max_prefixlen = trie->data_size * 8; | |
531 | ||
532 | cost_per_node = sizeof(struct lpm_trie_node) + | |
533 | attr->value_size + trie->data_size; | |
c502faf9 DB |
534 | cost += (u64) attr->max_entries * cost_per_node; |
535 | if (cost >= U32_MAX - PAGE_SIZE) { | |
536 | ret = -E2BIG; | |
537 | goto out_err; | |
538 | } | |
539 | ||
b95a5c4d DM |
540 | trie->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; |
541 | ||
542 | ret = bpf_map_precharge_memlock(trie->map.pages); | |
c502faf9 DB |
543 | if (ret) |
544 | goto out_err; | |
b95a5c4d DM |
545 | |
546 | raw_spin_lock_init(&trie->lock); | |
547 | ||
548 | return &trie->map; | |
c502faf9 DB |
549 | out_err: |
550 | kfree(trie); | |
551 | return ERR_PTR(ret); | |
b95a5c4d DM |
552 | } |
553 | ||
554 | static void trie_free(struct bpf_map *map) | |
555 | { | |
556 | struct lpm_trie *trie = container_of(map, struct lpm_trie, map); | |
557 | struct lpm_trie_node __rcu **slot; | |
558 | struct lpm_trie_node *node; | |
559 | ||
9a3efb6b YS |
560 | /* Wait for outstanding programs to complete |
561 | * update/lookup/delete/get_next_key and free the trie. | |
562 | */ | |
563 | synchronize_rcu(); | |
b95a5c4d DM |
564 | |
565 | /* Always start at the root and walk down to a node that has no | |
566 | * children. Then free that node, nullify its reference in the parent | |
567 | * and start over. | |
568 | */ | |
569 | ||
570 | for (;;) { | |
571 | slot = &trie->root; | |
572 | ||
573 | for (;;) { | |
6c5f6102 | 574 | node = rcu_dereference_protected(*slot, 1); |
b95a5c4d | 575 | if (!node) |
9a3efb6b | 576 | goto out; |
b95a5c4d DM |
577 | |
578 | if (rcu_access_pointer(node->child[0])) { | |
579 | slot = &node->child[0]; | |
580 | continue; | |
581 | } | |
582 | ||
583 | if (rcu_access_pointer(node->child[1])) { | |
584 | slot = &node->child[1]; | |
585 | continue; | |
586 | } | |
587 | ||
588 | kfree(node); | |
589 | RCU_INIT_POINTER(*slot, NULL); | |
590 | break; | |
591 | } | |
592 | } | |
593 | ||
9a3efb6b YS |
594 | out: |
595 | kfree(trie); | |
b95a5c4d DM |
596 | } |
597 | ||
b471f2f1 | 598 | static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key) |
f38837b0 | 599 | { |
6dd1ec6c | 600 | struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root; |
b471f2f1 YS |
601 | struct lpm_trie *trie = container_of(map, struct lpm_trie, map); |
602 | struct bpf_lpm_trie_key *key = _key, *next_key = _next_key; | |
b471f2f1 | 603 | struct lpm_trie_node **node_stack = NULL; |
b471f2f1 YS |
604 | int err = 0, stack_ptr = -1; |
605 | unsigned int next_bit; | |
606 | size_t matchlen; | |
607 | ||
608 | /* The get_next_key follows postorder. For the 4 node example in | |
609 | * the top of this file, the trie_get_next_key() returns the following | |
610 | * one after another: | |
611 | * 192.168.0.0/24 | |
612 | * 192.168.1.0/24 | |
613 | * 192.168.128.0/24 | |
614 | * 192.168.0.0/16 | |
615 | * | |
616 | * The idea is to return more specific keys before less specific ones. | |
617 | */ | |
618 | ||
619 | /* Empty trie */ | |
6dd1ec6c YS |
620 | search_root = rcu_dereference(trie->root); |
621 | if (!search_root) | |
b471f2f1 YS |
622 | return -ENOENT; |
623 | ||
624 | /* For invalid key, find the leftmost node in the trie */ | |
6dd1ec6c | 625 | if (!key || key->prefixlen > trie->max_prefixlen) |
b471f2f1 | 626 | goto find_leftmost; |
b471f2f1 | 627 | |
6da2ec56 KC |
628 | node_stack = kmalloc_array(trie->max_prefixlen, |
629 | sizeof(struct lpm_trie_node *), | |
630 | GFP_ATOMIC | __GFP_NOWARN); | |
b471f2f1 YS |
631 | if (!node_stack) |
632 | return -ENOMEM; | |
633 | ||
634 | /* Try to find the exact node for the given key */ | |
6dd1ec6c | 635 | for (node = search_root; node;) { |
b471f2f1 YS |
636 | node_stack[++stack_ptr] = node; |
637 | matchlen = longest_prefix_match(trie, node, key); | |
638 | if (node->prefixlen != matchlen || | |
639 | node->prefixlen == key->prefixlen) | |
640 | break; | |
641 | ||
642 | next_bit = extract_bit(key->data, node->prefixlen); | |
643 | node = rcu_dereference(node->child[next_bit]); | |
644 | } | |
645 | if (!node || node->prefixlen != key->prefixlen || | |
6dd1ec6c | 646 | (node->flags & LPM_TREE_NODE_FLAG_IM)) |
b471f2f1 | 647 | goto find_leftmost; |
b471f2f1 YS |
648 | |
649 | /* The node with the exactly-matching key has been found, | |
650 | * find the first node in postorder after the matched node. | |
651 | */ | |
652 | node = node_stack[stack_ptr]; | |
653 | while (stack_ptr > 0) { | |
654 | parent = node_stack[stack_ptr - 1]; | |
6dd1ec6c YS |
655 | if (rcu_dereference(parent->child[0]) == node) { |
656 | search_root = rcu_dereference(parent->child[1]); | |
657 | if (search_root) | |
658 | goto find_leftmost; | |
b471f2f1 YS |
659 | } |
660 | if (!(parent->flags & LPM_TREE_NODE_FLAG_IM)) { | |
661 | next_node = parent; | |
662 | goto do_copy; | |
663 | } | |
664 | ||
665 | node = parent; | |
666 | stack_ptr--; | |
667 | } | |
668 | ||
669 | /* did not find anything */ | |
670 | err = -ENOENT; | |
671 | goto free_stack; | |
672 | ||
673 | find_leftmost: | |
674 | /* Find the leftmost non-intermediate node, all intermediate nodes | |
675 | * have exact two children, so this function will never return NULL. | |
676 | */ | |
6dd1ec6c | 677 | for (node = search_root; node;) { |
b471f2f1 YS |
678 | if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) |
679 | next_node = node; | |
680 | node = rcu_dereference(node->child[0]); | |
681 | } | |
682 | do_copy: | |
683 | next_key->prefixlen = next_node->prefixlen; | |
684 | memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key, data), | |
685 | next_node->data, trie->data_size); | |
686 | free_stack: | |
687 | kfree(node_stack); | |
688 | return err; | |
f38837b0 AS |
689 | } |
690 | ||
e8d2bec0 DB |
691 | static int trie_check_btf(const struct bpf_map *map, |
692 | const struct btf_type *key_type, | |
693 | const struct btf_type *value_type) | |
694 | { | |
695 | /* Keys must have struct bpf_lpm_trie_key embedded. */ | |
696 | return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ? | |
697 | -EINVAL : 0; | |
698 | } | |
699 | ||
40077e0c | 700 | const struct bpf_map_ops trie_map_ops = { |
b95a5c4d DM |
701 | .map_alloc = trie_alloc, |
702 | .map_free = trie_free, | |
f38837b0 | 703 | .map_get_next_key = trie_get_next_key, |
b95a5c4d DM |
704 | .map_lookup_elem = trie_lookup_elem, |
705 | .map_update_elem = trie_update_elem, | |
706 | .map_delete_elem = trie_delete_elem, | |
e8d2bec0 | 707 | .map_check_btf = trie_check_btf, |
b95a5c4d | 708 | }; |