Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 748 insertions, 0 deletions

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
new file mode 100644
index 000000000..3c2d8722d
--- /dev/null
+++ b/kernel/bpf/lpm_trie.c
@@ -0,0 +1,748 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Longest prefix match list implementation
+ *
+ * Copyright (c) 2016,2017 Daniel Mack
+ * Copyright (c) 2016 David Herrmann
+ */
+
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/vmalloc.h>
+#include <net/ipv6.h>
+#include <uapi/linux/btf.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[];
+};
+
+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;
+	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)
+{
+	u32 limit = min(node->prefixlen, key->prefixlen);
+	u32 prefixlen = 0, i = 0;
+
+	BUILD_BUG_ON(offsetof(struct lpm_trie_node, data) % sizeof(u32));
+	BUILD_BUG_ON(offsetof(struct bpf_lpm_trie_key, data) % sizeof(u32));
+
+#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && defined(CONFIG_64BIT)
+
+	/* data_size >= 16 has very small probability.
+	 * We do not use a loop for optimal code generation.
+	 */
+	if (trie->data_size >= 8) {
+		u64 diff = be64_to_cpu(*(__be64 *)node->data ^
+				       *(__be64 *)key->data);
+
+		prefixlen = 64 - fls64(diff);
+		if (prefixlen >= limit)
+			return limit;
+		if (diff)
+			return prefixlen;
+		i = 8;
+	}
+#endif
+
+	while (trie->data_size >= i + 4) {
+		u32 diff = be32_to_cpu(*(__be32 *)&node->data[i] ^
+				       *(__be32 *)&key->data[i]);
+
+		prefixlen += 32 - fls(diff);
+		if (prefixlen >= limit)
+			return limit;
+		if (diff)
+			return prefixlen;
+		i += 4;
+	}
+
+	if (trie->data_size >= i + 2) {
+		u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] ^
+				       *(__be16 *)&key->data[i]);
+
+		prefixlen += 16 - fls(diff);
+		if (prefixlen >= limit)
+			return limit;
+		if (diff)
+			return prefixlen;
+		i += 2;
+	}
+
+	if (trie->data_size >= i + 1) {
+		prefixlen += 8 - fls(node->data[i] ^ key->data[i]);
+
+		if (prefixlen >= limit)
+			return limit;
+	}
+
+	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;
+
+	if (key->prefixlen > trie->max_prefixlen)
+		return NULL;
+
+	/* 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;
+
+	node = kmalloc_node(size, GFP_ATOMIC | __GFP_NOWARN,
+			    trie->map.numa_node);
+	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);
+	struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL;
+	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;
+
+	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);
+	}
+
+	spin_unlock_irqrestore(&trie->lock, irq_flags);
+
+	return ret;
+}
+
+/* Called from syscall or from eBPF program */
+static int trie_delete_elem(struct bpf_map *map, void *_key)
+{
+	struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
+	struct bpf_lpm_trie_key *key = _key;
+	struct lpm_trie_node __rcu **trim, **trim2;
+	struct lpm_trie_node *node, *parent;
+	unsigned long irq_flags;
+	unsigned int next_bit;
+	size_t matchlen = 0;
+	int ret = 0;
+
+	if (key->prefixlen > trie->max_prefixlen)
+		return -EINVAL;
+
+	spin_lock_irqsave(&trie->lock, irq_flags);
+
+	/* Walk the tree looking for an exact key/length match and keeping
+	 * 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.
+	 */
+	trim = &trie->root;
+	trim2 = trim;
+	parent = NULL;
+	while ((node = rcu_dereference_protected(
+		       *trim, lockdep_is_held(&trie->lock)))) {
+		matchlen = longest_prefix_match(trie, node, key);
+
+		if (node->prefixlen != matchlen ||
+		    node->prefixlen == key->prefixlen)
+			break;
+
+		parent = node;
+		trim2 = trim;
+		next_bit = extract_bit(key->data, node->prefixlen);
+		trim = &node->child[next_bit];
+	}
+
+	if (!node || node->prefixlen != key->prefixlen ||
+	    node->prefixlen != matchlen ||
+	    (node->flags & LPM_TREE_NODE_FLAG_IM)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	trie->n_entries--;
+
+	/* If the node we are removing has two children, simply mark it
+	 * as intermediate and we are done.
+	 */
+	if (rcu_access_pointer(node->child[0]) &&
+	    rcu_access_pointer(node->child[1])) {
+		node->flags |= LPM_TREE_NODE_FLAG_IM;
+		goto out;
+	}
+
+	/* 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.
+	 */
+	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);
+		kfree_rcu(node, rcu);
+		goto out;
+	}
+
+	/* 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);
+
+out:
+	spin_unlock_irqrestore(&trie->lock, irq_flags);
+
+	return ret;
+}
+
+#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)
+
+#define LPM_CREATE_FLAG_MASK	(BPF_F_NO_PREALLOC | BPF_F_NUMA_NODE |	\
+				 BPF_F_ACCESS_MASK)
+
+static struct bpf_map *trie_alloc(union bpf_attr *attr)
+{
+	struct lpm_trie *trie;
+	u64 cost = sizeof(*trie), cost_per_node;
+	int ret;
+
+	if (!bpf_capable())
+		return ERR_PTR(-EPERM);
+
+	/* check sanity of attributes */
+	if (attr->max_entries == 0 ||
+	    !(attr->map_flags & BPF_F_NO_PREALLOC) ||
+	    attr->map_flags & ~LPM_CREATE_FLAG_MASK ||
+	    !bpf_map_flags_access_ok(attr->map_flags) ||
+	    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)
+		return ERR_PTR(-EINVAL);
+
+	trie = kzalloc(sizeof(*trie), GFP_USER | __GFP_NOWARN);
+	if (!trie)
+		return ERR_PTR(-ENOMEM);
+
+	/* copy mandatory map attributes */
+	bpf_map_init_from_attr(&trie->map, attr);
+	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;
+	cost += (u64) attr->max_entries * cost_per_node;
+
+	ret = bpf_map_charge_init(&trie->map.memory, cost);
+	if (ret)
+		goto out_err;
+
+	spin_lock_init(&trie->lock);
+
+	return &trie->map;
+out_err:
+	kfree(trie);
+	return ERR_PTR(ret);
+}
+
+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;
+
+	/* 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, 1);
+			if (!node)
+				goto out;
+
+			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;
+		}
+	}
+
+out:
+	kfree(trie);
+}
+
+static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key)
+{
+	struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root;
+	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 */
+	search_root = rcu_dereference(trie->root);
+	if (!search_root)
+		return -ENOENT;
+
+	/* For invalid key, find the leftmost node in the trie */
+	if (!key || key->prefixlen > trie->max_prefixlen)
+		goto find_leftmost;
+
+	node_stack = kmalloc_array(trie->max_prefixlen,
+				   sizeof(struct lpm_trie_node *),
+				   GFP_ATOMIC | __GFP_NOWARN);
+	if (!node_stack)
+		return -ENOMEM;
+
+	/* Try to find the exact node for the given key */
+	for (node = search_root; node;) {
+		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 ||
+	    (node->flags & LPM_TREE_NODE_FLAG_IM))
+		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];
+		if (rcu_dereference(parent->child[0]) == node) {
+			search_root = rcu_dereference(parent->child[1]);
+			if (search_root)
+				goto find_leftmost;
+		}
+		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.
+	 */
+	for (node = search_root; node;) {
+		if (node->flags & LPM_TREE_NODE_FLAG_IM) {
+			node = rcu_dereference(node->child[0]);
+		} else {
+			next_node = node;
+			node = rcu_dereference(node->child[0]);
+			if (!node)
+				node = rcu_dereference(next_node->child[1]);
+		}
+	}
+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;
+}
+
+static int trie_check_btf(const struct bpf_map *map,
+			  const struct btf *btf,
+			  const struct btf_type *key_type,
+			  const struct btf_type *value_type)
+{
+	/* Keys must have struct bpf_lpm_trie_key embedded. */
+	return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ?
+	       -EINVAL : 0;
+}
+
+static int trie_map_btf_id;
+const struct bpf_map_ops trie_map_ops = {
+	.map_meta_equal = bpf_map_meta_equal,
+	.map_alloc = trie_alloc,
+	.map_free = trie_free,
+	.map_get_next_key = trie_get_next_key,
+	.map_lookup_elem = trie_lookup_elem,
+	.map_update_elem = trie_update_elem,
+	.map_delete_elem = trie_delete_elem,
+	.map_check_btf = trie_check_btf,
+	.map_btf_name = "lpm_trie",
+	.map_btf_id = &trie_map_btf_id,
+};