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Commit e454cf59 authored by Craig Gallek's avatar Craig Gallek Committed by David S. Miller
Browse files

bpf: Implement map_delete_elem for BPF_MAP_TYPE_LPM_TRIE 



This is a simple non-recursive delete operation.  It prunes paths
of empty nodes in the tree, but it does not try to further compress
the tree as nodes are removed.

Signed-off-by: default avatarCraig Gallek <kraig@google.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 173f4c5e

kernel/bpf/lpm_trie.c

+77 −3
Original line number Diff line number Diff line
@@ -389,10 +389,84 @@ static int trie_update_elem(struct bpf_map *map, 
	return ret;

}



static int trie_delete_elem(struct bpf_map *map, void *key)

/* Called from syscall or from eBPF program */

static int trie_delete_elem(struct bpf_map *map, void *_key)

{

	/* TODO */

	return -ENOSYS;

	struct lpm_trie *trie = container_of(map, struct lpm_trie, map);

	struct bpf_lpm_trie_key *key = _key;

	struct lpm_trie_node __rcu **trim;

	struct lpm_trie_node *node;

	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

	 * track of where we could begin trimming the tree.  The trim-point

	 * is the sub-tree along the walk consisting of only single-child

	 * intermediate nodes and ending at a leaf node that we want to

	 * remove.

	 */

	trim = &trie->root;

	node = rcu_dereference_protected(

		trie->root, lockdep_is_held(&trie->lock));

	while (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);

		/* If we hit a node that has more than one child or is a valid

		 * prefix itself, do not remove it. Reset the root of the trim

		 * path to its descendant on our path.

		 */

		if (!(node->flags & LPM_TREE_NODE_FLAG_IM) ||

		    (node->child[0] && node->child[1]))

			trim = &node->child[next_bit];

		node = rcu_dereference_protected(

			node->child[next_bit], lockdep_is_held(&trie->lock));

	}



	if (!node || node->prefixlen != key->prefixlen ||

	    (node->flags & LPM_TREE_NODE_FLAG_IM)) {

		ret = -ENOENT;

		goto out;

	}



	trie->n_entries--;



	/* If the node we are removing is not a leaf node, 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;

	}



	/* trim should now point to the slot holding the start of a path from

	 * zero or more intermediate nodes to our leaf node for deletion.

	 */

	while ((node = rcu_dereference_protected(

			*trim, lockdep_is_held(&trie->lock)))) {

		RCU_INIT_POINTER(*trim, NULL);

		trim = rcu_access_pointer(node->child[0]) ?

			&node->child[0] :

			&node->child[1];

		kfree_rcu(node, rcu);

	}



out:

	raw_spin_unlock_irqrestore(&trie->lock, irq_flags);



	return ret;

}



#define LPM_DATA_SIZE_MAX	256