Merge branch 'bpf-lpm-get-next-key'

Yonghong Song says:

====================
This patch set implements MAP_GET_NEXT_KEY command for LPM_TRIE map.
This command is really useful for key enumeration, and for key deletion
if what keys in the trie are unknown.

Patch #1 implements the functionality in the kernel and patch #2
adds a test case in tools/testing/selftests/bpf.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 93 insertions, 2 deletions

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index 584e02227671..d7ea96218516 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -591,9 +591,100 @@ unlock:
 	raw_spin_unlock(&trie->lock);
 }
 
-static int trie_get_next_key(struct bpf_map *map, void *key, void *next_key)
+static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key)
 {
-	return -ENOTSUPP;
+	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, *next_node = NULL, *parent;
+	struct lpm_trie_node **node_stack = NULL;
+	struct lpm_trie_node __rcu **root;
+	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 */
+	if (!rcu_dereference(trie->root))
+		return -ENOENT;
+
+	/* For invalid key, find the leftmost node in the trie */
+	if (!key || key->prefixlen > trie->max_prefixlen) {
+		root = &trie->root;
+		goto find_leftmost;
+	}
+
+	node_stack = kmalloc(trie->max_prefixlen * sizeof(struct lpm_trie_node *),
+			     GFP_USER | __GFP_NOWARN);
+	if (!node_stack)
+		return -ENOMEM;
+
+	/* Try to find the exact node for the given key */
+	for (node = rcu_dereference(trie->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)) {
+		root = &trie->root;
+		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 &&
+		    rcu_dereference(parent->child[1])) {
+			root = &parent->child[1];
+			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 = rcu_dereference(*root); node;) {
+		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;
 }
 
 const struct bpf_map_ops trie_map_ops = {