bpf: Handle BPF_EXIST and BPF_NOEXIST for LPM trie

Add the currently missing handling for the BPF_EXIST and BPF_NOEXIST
flags. These flags can be specified by users and are relevant since LPM
trie supports exact matches during update.

Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map implementation")
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20241206110622.1161752-4-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index b5e281a55760be68ceca93caadb7aa608a7cd55b..be5bf03895328c7eb524d2a4da841ba93d8adba3 100644 (file)
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -375,6 +375,10 @@ static long trie_update_elem(struct bpf_map *map,
         * simply assign the @new_node to that slot and be done.
         */
        if (!node) {
+               if (flags == BPF_EXIST) {
+                       ret = -ENOENT;
+                       goto out;
+               }
                rcu_assign_pointer(*slot, new_node);
                goto out;
        }
@@ -383,18 +387,31 @@ static long trie_update_elem(struct bpf_map *map,
         * which already has the correct data array set.
         */
        if (node->prefixlen == matchlen) {
+               if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) {
+                       if (flags == BPF_NOEXIST) {
+                               ret = -EEXIST;
+                               goto out;
+                       }
+                       trie->n_entries--;
+               } else if (flags == BPF_EXIST) {
+                       ret = -ENOENT;
+                       goto out;
+               }
+
                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);
                free_node = node;
 
                goto out;
        }
 
+       if (flags == BPF_EXIST) {
+               ret = -ENOENT;
+               goto out;
+       }
+
        /* If the new node matches the prefix completely, it must be inserted
         * as an ancestor. Simply insert it between @node and *@slot.
         */