lpm_trie.c 19.9 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246
/*
 * Longest prefix match list implementation
 *
 * Copyright (c) 2016,2017 Daniel Mack
 * Copyright (c) 2016 David Herrmann
 *
 * This file is subject to the terms and conditions of version 2 of the GNU
 * General Public License.  See the file COPYING in the main directory of the
 * Linux distribution for more details.
 */

#include <linux/bpf.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include <net/ipv6.h>

/* Intermediate node */
#define LPM_TREE_NODE_FLAG_IM BIT(0)

struct lpm_trie_node;

struct lpm_trie_node {
	struct rcu_head rcu;
	struct lpm_trie_node __rcu	*child[2];
	u32				prefixlen;
	u32				flags;
	u8				data[0];
};

struct lpm_trie {
	struct bpf_map			map;
	struct lpm_trie_node __rcu	*root;
	size_t				n_entries;
	size_t				max_prefixlen;
	size_t				data_size;
	raw_spinlock_t			lock;
};

/* This trie implements a longest prefix match algorithm that can be used to
 * match IP addresses to a stored set of ranges.
 *
 * Data stored in @data of struct bpf_lpm_key and struct lpm_trie_node is
 * interpreted as big endian, so data[0] stores the most significant byte.
 *
 * Match ranges are internally stored in instances of struct lpm_trie_node
 * which each contain their prefix length as well as two pointers that may
 * lead to more nodes containing more specific matches. Each node also stores
 * a value that is defined by and returned to userspace via the update_elem
 * and lookup functions.
 *
 * For instance, let's start with a trie that was created with a prefix length
 * of 32, so it can be used for IPv4 addresses, and one single element that
 * matches 192.168.0.0/16. The data array would hence contain
 * [0xc0, 0xa8, 0x00, 0x00] in big-endian notation. This documentation will
 * stick to IP-address notation for readability though.
 *
 * As the trie is empty initially, the new node (1) will be places as root
 * node, denoted as (R) in the example below. As there are no other node, both
 * child pointers are %NULL.
 *
 *              +----------------+
 *              |       (1)  (R) |
 *              | 192.168.0.0/16 |
 *              |    value: 1    |
 *              |   [0]    [1]   |
 *              +----------------+
 *
 * Next, let's add a new node (2) matching 192.168.0.0/24. As there is already
 * a node with the same data and a smaller prefix (ie, a less specific one),
 * node (2) will become a child of (1). In child index depends on the next bit
 * that is outside of what (1) matches, and that bit is 0, so (2) will be
 * child[0] of (1):
 *
 *              +----------------+
 *              |       (1)  (R) |
 *              | 192.168.0.0/16 |
 *              |    value: 1    |
 *              |   [0]    [1]   |
 *              +----------------+
 *                   |
 *    +----------------+
 *    |       (2)      |
 *    | 192.168.0.0/24 |
 *    |    value: 2    |
 *    |   [0]    [1]   |
 *    +----------------+
 *
 * The child[1] slot of (1) could be filled with another node which has bit #17
 * (the next bit after the ones that (1) matches on) set to 1. For instance,
 * 192.168.128.0/24:
 *
 *              +----------------+
 *              |       (1)  (R) |
 *              | 192.168.0.0/16 |
 *              |    value: 1    |
 *              |   [0]    [1]   |
 *              +----------------+
 *                   |      |
 *    +----------------+  +------------------+
 *    |       (2)      |  |        (3)       |
 *    | 192.168.0.0/24 |  | 192.168.128.0/24 |
 *    |    value: 2    |  |     value: 3     |
 *    |   [0]    [1]   |  |    [0]    [1]    |
 *    +----------------+  +------------------+
 *
 * Let's add another node (4) to the game for 192.168.1.0/24. In order to place
 * it, node (1) is looked at first, and because (4) of the semantics laid out
 * above (bit #17 is 0), it would normally be attached to (1) as child[0].
 * However, that slot is already allocated, so a new node is needed in between.
 * That node does not have a value attached to it and it will never be
 * returned to users as result of a lookup. It is only there to differentiate
 * the traversal further. It will get a prefix as wide as necessary to
 * distinguish its two children:
 *
 *                      +----------------+
 *                      |       (1)  (R) |
 *                      | 192.168.0.0/16 |
 *                      |    value: 1    |
 *                      |   [0]    [1]   |
 *                      +----------------+
 *                           |      |
 *            +----------------+  +------------------+
 *            |       (4)  (I) |  |        (3)       |
 *            | 192.168.0.0/23 |  | 192.168.128.0/24 |
 *            |    value: ---  |  |     value: 3     |
 *            |   [0]    [1]   |  |    [0]    [1]    |
 *            +----------------+  +------------------+
 *                 |      |
 *  +----------------+  +----------------+
 *  |       (2)      |  |       (5)      |
 *  | 192.168.0.0/24 |  | 192.168.1.0/24 |
 *  |    value: 2    |  |     value: 5   |
 *  |   [0]    [1]   |  |   [0]    [1]   |
 *  +----------------+  +----------------+
 *
 * 192.168.1.1/32 would be a child of (5) etc.
 *
 * An intermediate node will be turned into a 'real' node on demand. In the
 * example above, (4) would be re-used if 192.168.0.0/23 is added to the trie.
 *
 * A fully populated trie would have a height of 32 nodes, as the trie was
 * created with a prefix length of 32.
 *
 * The lookup starts at the root node. If the current node matches and if there
 * is a child that can be used to become more specific, the trie is traversed
 * downwards. The last node in the traversal that is a non-intermediate one is
 * returned.
 */

static inline int extract_bit(const u8 *data, size_t index)
{
	return !!(data[index / 8] & (1 << (7 - (index % 8))));
}

/**
 * longest_prefix_match() - determine the longest prefix
 * @trie:	The trie to get internal sizes from
 * @node:	The node to operate on
 * @key:	The key to compare to @node
 *
 * Determine the longest prefix of @node that matches the bits in @key.
 */
static size_t longest_prefix_match(const struct lpm_trie *trie,
				   const struct lpm_trie_node *node,
				   const struct bpf_lpm_trie_key *key)
{
	size_t prefixlen = 0;
	size_t i;

	for (i = 0; i < trie->data_size; i++) {
		size_t b;

		b = 8 - fls(node->data[i] ^ key->data[i]);
		prefixlen += b;

		if (prefixlen >= node->prefixlen || prefixlen >= key->prefixlen)
			return min(node->prefixlen, key->prefixlen);

		if (b < 8)
			break;
	}

	return prefixlen;
}

/* Called from syscall or from eBPF program */
static void *trie_lookup_elem(struct bpf_map *map, void *_key)
{
	struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
	struct lpm_trie_node *node, *found = NULL;
	struct bpf_lpm_trie_key *key = _key;

	/* Start walking the trie from the root node ... */

	for (node = rcu_dereference(trie->root); node;) {
		unsigned int next_bit;
		size_t matchlen;

		/* Determine the longest prefix of @node that matches @key.
		 * If it's the maximum possible prefix for this trie, we have
		 * an exact match and can return it directly.
		 */
		matchlen = longest_prefix_match(trie, node, key);
		if (matchlen == trie->max_prefixlen) {
			found = node;
			break;
		}

		/* If the number of bits that match is smaller than the prefix
		 * length of @node, bail out and return the node we have seen
		 * last in the traversal (ie, the parent).
		 */
		if (matchlen < node->prefixlen)
			break;

		/* Consider this node as return candidate unless it is an
		 * artificially added intermediate one.
		 */
		if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
			found = node;

		/* If the node match is fully satisfied, let's see if we can
		 * become more specific. Determine the next bit in the key and
		 * traverse down.
		 */
		next_bit = extract_bit(key->data, node->prefixlen);
		node = rcu_dereference(node->child[next_bit]);
	}

	if (!found)
		return NULL;

	return found->data + trie->data_size;
}

static struct lpm_trie_node *lpm_trie_node_alloc(const struct lpm_trie *trie,
						 const void *value)
{
	struct lpm_trie_node *node;
	size_t size = sizeof(struct lpm_trie_node) + trie->data_size;

	if (value)
		size += trie->map.value_size;

247 248
	node = kmalloc_node(size, GFP_ATOMIC | __GFP_NOWARN,
			    trie->map.numa_node);
249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265
	if (!node)
		return NULL;

	node->flags = 0;

	if (value)
		memcpy(node->data + trie->data_size, value,
		       trie->map.value_size);

	return node;
}

/* Called from syscall or from eBPF program */
static int trie_update_elem(struct bpf_map *map,
			    void *_key, void *value, u64 flags)
{
	struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
266
	struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL;
267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391
	struct lpm_trie_node __rcu **slot;
	struct bpf_lpm_trie_key *key = _key;
	unsigned long irq_flags;
	unsigned int next_bit;
	size_t matchlen = 0;
	int ret = 0;

	if (unlikely(flags > BPF_EXIST))
		return -EINVAL;

	if (key->prefixlen > trie->max_prefixlen)
		return -EINVAL;

	raw_spin_lock_irqsave(&trie->lock, irq_flags);

	/* Allocate and fill a new node */

	if (trie->n_entries == trie->map.max_entries) {
		ret = -ENOSPC;
		goto out;
	}

	new_node = lpm_trie_node_alloc(trie, value);
	if (!new_node) {
		ret = -ENOMEM;
		goto out;
	}

	trie->n_entries++;

	new_node->prefixlen = key->prefixlen;
	RCU_INIT_POINTER(new_node->child[0], NULL);
	RCU_INIT_POINTER(new_node->child[1], NULL);
	memcpy(new_node->data, key->data, trie->data_size);

	/* Now find a slot to attach the new node. To do that, walk the tree
	 * from the root and match as many bits as possible for each node until
	 * we either find an empty slot or a slot that needs to be replaced by
	 * an intermediate node.
	 */
	slot = &trie->root;

	while ((node = rcu_dereference_protected(*slot,
					lockdep_is_held(&trie->lock)))) {
		matchlen = longest_prefix_match(trie, node, key);

		if (node->prefixlen != matchlen ||
		    node->prefixlen == key->prefixlen ||
		    node->prefixlen == trie->max_prefixlen)
			break;

		next_bit = extract_bit(key->data, node->prefixlen);
		slot = &node->child[next_bit];
	}

	/* If the slot is empty (a free child pointer or an empty root),
	 * simply assign the @new_node to that slot and be done.
	 */
	if (!node) {
		rcu_assign_pointer(*slot, new_node);
		goto out;
	}

	/* If the slot we picked already exists, replace it with @new_node
	 * which already has the correct data array set.
	 */
	if (node->prefixlen == matchlen) {
		new_node->child[0] = node->child[0];
		new_node->child[1] = node->child[1];

		if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
			trie->n_entries--;

		rcu_assign_pointer(*slot, new_node);
		kfree_rcu(node, rcu);

		goto out;
	}

	/* If the new node matches the prefix completely, it must be inserted
	 * as an ancestor. Simply insert it between @node and *@slot.
	 */
	if (matchlen == key->prefixlen) {
		next_bit = extract_bit(node->data, matchlen);
		rcu_assign_pointer(new_node->child[next_bit], node);
		rcu_assign_pointer(*slot, new_node);
		goto out;
	}

	im_node = lpm_trie_node_alloc(trie, NULL);
	if (!im_node) {
		ret = -ENOMEM;
		goto out;
	}

	im_node->prefixlen = matchlen;
	im_node->flags |= LPM_TREE_NODE_FLAG_IM;
	memcpy(im_node->data, node->data, trie->data_size);

	/* Now determine which child to install in which slot */
	if (extract_bit(key->data, matchlen)) {
		rcu_assign_pointer(im_node->child[0], node);
		rcu_assign_pointer(im_node->child[1], new_node);
	} else {
		rcu_assign_pointer(im_node->child[0], new_node);
		rcu_assign_pointer(im_node->child[1], node);
	}

	/* Finally, assign the intermediate node to the determined spot */
	rcu_assign_pointer(*slot, im_node);

out:
	if (ret) {
		if (new_node)
			trie->n_entries--;

		kfree(new_node);
		kfree(im_node);
	}

	raw_spin_unlock_irqrestore(&trie->lock, irq_flags);

	return ret;
}

392 393
/* Called from syscall or from eBPF program */
static int trie_delete_elem(struct bpf_map *map, void *_key)
394
{
395 396
	struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
	struct bpf_lpm_trie_key *key = _key;
C
Craig Gallek 已提交
397 398
	struct lpm_trie_node __rcu **trim, **trim2;
	struct lpm_trie_node *node, *parent;
399 400 401 402 403 404 405 406 407 408 409
	unsigned long irq_flags;
	unsigned int next_bit;
	size_t matchlen = 0;
	int ret = 0;

	if (key->prefixlen > trie->max_prefixlen)
		return -EINVAL;

	raw_spin_lock_irqsave(&trie->lock, irq_flags);

	/* Walk the tree looking for an exact key/length match and keeping
C
Craig Gallek 已提交
410 411 412 413
	 * track of the path we traverse.  We will need to know the node
	 * we wish to delete, and the slot that points to the node we want
	 * to delete.  We may also need to know the nodes parent and the
	 * slot that contains it.
414 415
	 */
	trim = &trie->root;
C
Craig Gallek 已提交
416 417 418 419
	trim2 = trim;
	parent = NULL;
	while ((node = rcu_dereference_protected(
		       *trim, lockdep_is_held(&trie->lock)))) {
420 421 422 423 424 425
		matchlen = longest_prefix_match(trie, node, key);

		if (node->prefixlen != matchlen ||
		    node->prefixlen == key->prefixlen)
			break;

C
Craig Gallek 已提交
426 427
		parent = node;
		trim2 = trim;
428
		next_bit = extract_bit(key->data, node->prefixlen);
C
Craig Gallek 已提交
429
		trim = &node->child[next_bit];
430 431 432 433 434 435 436 437 438 439
	}

	if (!node || node->prefixlen != key->prefixlen ||
	    (node->flags & LPM_TREE_NODE_FLAG_IM)) {
		ret = -ENOENT;
		goto out;
	}

	trie->n_entries--;

C
Craig Gallek 已提交
440
	/* If the node we are removing has two children, simply mark it
441 442
	 * as intermediate and we are done.
	 */
C
Craig Gallek 已提交
443
	if (rcu_access_pointer(node->child[0]) &&
444 445 446 447 448
	    rcu_access_pointer(node->child[1])) {
		node->flags |= LPM_TREE_NODE_FLAG_IM;
		goto out;
	}

C
Craig Gallek 已提交
449 450 451 452 453 454
	/* If the parent of the node we are about to delete is an intermediate
	 * node, and the deleted node doesn't have any children, we can delete
	 * the intermediate parent as well and promote its other child
	 * up the tree.  Doing this maintains the invariant that all
	 * intermediate nodes have exactly 2 children and that there are no
	 * unnecessary intermediate nodes in the tree.
455
	 */
C
Craig Gallek 已提交
456 457 458 459 460 461 462 463 464
	if (parent && (parent->flags & LPM_TREE_NODE_FLAG_IM) &&
	    !node->child[0] && !node->child[1]) {
		if (node == rcu_access_pointer(parent->child[0]))
			rcu_assign_pointer(
				*trim2, rcu_access_pointer(parent->child[1]));
		else
			rcu_assign_pointer(
				*trim2, rcu_access_pointer(parent->child[0]));
		kfree_rcu(parent, rcu);
465
		kfree_rcu(node, rcu);
C
Craig Gallek 已提交
466
		goto out;
467 468
	}

C
Craig Gallek 已提交
469 470 471 472 473 474 475 476 477 478 479 480
	/* The node we are removing has either zero or one child. If there
	 * is a child, move it into the removed node's slot then delete
	 * the node.  Otherwise just clear the slot and delete the node.
	 */
	if (node->child[0])
		rcu_assign_pointer(*trim, rcu_access_pointer(node->child[0]));
	else if (node->child[1])
		rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1]));
	else
		RCU_INIT_POINTER(*trim, NULL);
	kfree_rcu(node, rcu);

481 482 483 484
out:
	raw_spin_unlock_irqrestore(&trie->lock, irq_flags);

	return ret;
485 486
}

487 488 489 490 491 492 493 494 495 496 497
#define LPM_DATA_SIZE_MAX	256
#define LPM_DATA_SIZE_MIN	1

#define LPM_VAL_SIZE_MAX	(KMALLOC_MAX_SIZE - LPM_DATA_SIZE_MAX - \
				 sizeof(struct lpm_trie_node))
#define LPM_VAL_SIZE_MIN	1

#define LPM_KEY_SIZE(X)		(sizeof(struct bpf_lpm_trie_key) + (X))
#define LPM_KEY_SIZE_MAX	LPM_KEY_SIZE(LPM_DATA_SIZE_MAX)
#define LPM_KEY_SIZE_MIN	LPM_KEY_SIZE(LPM_DATA_SIZE_MIN)

498 499
#define LPM_CREATE_FLAG_MASK	(BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE |	\
				 BPF_F_RDONLY | BPF_F_WRONLY)
500

501 502 503
static struct bpf_map *trie_alloc(union bpf_attr *attr)
{
	struct lpm_trie *trie;
504
	u64 cost = sizeof(*trie), cost_per_node;
505 506 507 508 509 510 511
	int ret;

	if (!capable(CAP_SYS_ADMIN))
		return ERR_PTR(-EPERM);

	/* check sanity of attributes */
	if (attr->max_entries == 0 ||
512 513
	    !(attr->map_flags & BPF_F_NO_PREALLOC) ||
	    attr->map_flags & ~LPM_CREATE_FLAG_MASK ||
514 515 516 517
	    attr->key_size < LPM_KEY_SIZE_MIN ||
	    attr->key_size > LPM_KEY_SIZE_MAX ||
	    attr->value_size < LPM_VAL_SIZE_MIN ||
	    attr->value_size > LPM_VAL_SIZE_MAX)
518 519 520 521 522 523 524
		return ERR_PTR(-EINVAL);

	trie = kzalloc(sizeof(*trie), GFP_USER | __GFP_NOWARN);
	if (!trie)
		return ERR_PTR(-ENOMEM);

	/* copy mandatory map attributes */
525
	bpf_map_init_from_attr(&trie->map, attr);
526 527 528 529 530 531
	trie->data_size = attr->key_size -
			  offsetof(struct bpf_lpm_trie_key, data);
	trie->max_prefixlen = trie->data_size * 8;

	cost_per_node = sizeof(struct lpm_trie_node) +
			attr->value_size + trie->data_size;
532 533 534 535 536 537
	cost += (u64) attr->max_entries * cost_per_node;
	if (cost >= U32_MAX - PAGE_SIZE) {
		ret = -E2BIG;
		goto out_err;
	}

538 539 540
	trie->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;

	ret = bpf_map_precharge_memlock(trie->map.pages);
541 542
	if (ret)
		goto out_err;
543 544 545 546

	raw_spin_lock_init(&trie->lock);

	return &trie->map;
547 548 549
out_err:
	kfree(trie);
	return ERR_PTR(ret);
550 551 552 553 554 555 556 557
}

static void trie_free(struct bpf_map *map)
{
	struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
	struct lpm_trie_node __rcu **slot;
	struct lpm_trie_node *node;

558 559 560 561
	/* Wait for outstanding programs to complete
	 * update/lookup/delete/get_next_key and free the trie.
	 */
	synchronize_rcu();
562 563 564 565 566 567 568 569 570 571 572 573 574

	/* Always start at the root and walk down to a node that has no
	 * children. Then free that node, nullify its reference in the parent
	 * and start over.
	 */

	for (;;) {
		slot = &trie->root;

		for (;;) {
			node = rcu_dereference_protected(*slot,
					lockdep_is_held(&trie->lock));
			if (!node)
575
				goto out;
576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592

			if (rcu_access_pointer(node->child[0])) {
				slot = &node->child[0];
				continue;
			}

			if (rcu_access_pointer(node->child[1])) {
				slot = &node->child[1];
				continue;
			}

			kfree(node);
			RCU_INIT_POINTER(*slot, NULL);
			break;
		}
	}

593 594
out:
	kfree(trie);
595 596
}

597
static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key)
598
{
599
	struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root;
600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618
	struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
	struct bpf_lpm_trie_key *key = _key, *next_key = _next_key;
	struct lpm_trie_node **node_stack = NULL;
	int err = 0, stack_ptr = -1;
	unsigned int next_bit;
	size_t matchlen;

	/* The get_next_key follows postorder. For the 4 node example in
	 * the top of this file, the trie_get_next_key() returns the following
	 * one after another:
	 *   192.168.0.0/24
	 *   192.168.1.0/24
	 *   192.168.128.0/24
	 *   192.168.0.0/16
	 *
	 * The idea is to return more specific keys before less specific ones.
	 */

	/* Empty trie */
619 620
	search_root = rcu_dereference(trie->root);
	if (!search_root)
621 622 623
		return -ENOENT;

	/* For invalid key, find the leftmost node in the trie */
624
	if (!key || key->prefixlen > trie->max_prefixlen)
625 626 627
		goto find_leftmost;

	node_stack = kmalloc(trie->max_prefixlen * sizeof(struct lpm_trie_node *),
628
			     GFP_ATOMIC | __GFP_NOWARN);
629 630 631 632
	if (!node_stack)
		return -ENOMEM;

	/* Try to find the exact node for the given key */
633
	for (node = search_root; node;) {
634 635 636 637 638 639 640 641 642 643
		node_stack[++stack_ptr] = node;
		matchlen = longest_prefix_match(trie, node, key);
		if (node->prefixlen != matchlen ||
		    node->prefixlen == key->prefixlen)
			break;

		next_bit = extract_bit(key->data, node->prefixlen);
		node = rcu_dereference(node->child[next_bit]);
	}
	if (!node || node->prefixlen != key->prefixlen ||
644
	    (node->flags & LPM_TREE_NODE_FLAG_IM))
645 646 647 648 649 650 651 652
		goto find_leftmost;

	/* The node with the exactly-matching key has been found,
	 * find the first node in postorder after the matched node.
	 */
	node = node_stack[stack_ptr];
	while (stack_ptr > 0) {
		parent = node_stack[stack_ptr - 1];
653 654 655 656
		if (rcu_dereference(parent->child[0]) == node) {
			search_root = rcu_dereference(parent->child[1]);
			if (search_root)
				goto find_leftmost;
657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674
		}
		if (!(parent->flags & LPM_TREE_NODE_FLAG_IM)) {
			next_node = parent;
			goto do_copy;
		}

		node = parent;
		stack_ptr--;
	}

	/* did not find anything */
	err = -ENOENT;
	goto free_stack;

find_leftmost:
	/* Find the leftmost non-intermediate node, all intermediate nodes
	 * have exact two children, so this function will never return NULL.
	 */
675
	for (node = search_root; node;) {
676 677 678 679 680 681 682 683 684 685 686
		if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
			next_node = node;
		node = rcu_dereference(node->child[0]);
	}
do_copy:
	next_key->prefixlen = next_node->prefixlen;
	memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key, data),
	       next_node->data, trie->data_size);
free_stack:
	kfree(node_stack);
	return err;
687 688
}

689
const struct bpf_map_ops trie_map_ops = {
690 691
	.map_alloc = trie_alloc,
	.map_free = trie_free,
692
	.map_get_next_key = trie_get_next_key,
693 694 695 696
	.map_lookup_elem = trie_lookup_elem,
	.map_update_elem = trie_update_elem,
	.map_delete_elem = trie_delete_elem,
};