Libbpf userspace function `bpf_map__lookup_and_delete_elem`

Allows to lookup BPF map value corresponding to provided key and atomically delete it afterwards.

Definition

int bpf_map__lookup_and_delete_elem(const struct bpf_map *map, const void *key, size_t key_sz, void *value, size_t value_sz, __u64 flags);

Parameters

map: BPF map to lookup element in
key: pointer to memory containing bytes of the key used for lookup
key_sz: size in bytes of key data, needs to match BPF map definition's key_size
value: pointer to memory in which looked up value will be stored
value_sz: size in byte of value data memory; it has to match BPF map definition's value_size. For per-CPU BPF maps value size has to be a product of BPF map value size and number of possible CPUs in the system (could be fetched with libbpf_num_possible_cpus()). Note also that for per-CPU values value size has to be aligned up to closest 8 bytes for alignment reasons, so expected size is: round_up(value_size, 8) * libbpf_num_possible_cpus().
flags: flags passed to kernel for this operation

Return

0, on success; negative error, otherwise

bpf_map__lookup_and_delete_elem() is high-level equivalent of bpf_map_lookup_and_delete_elem() API with added check for key and value size.

Docs could be improved

This part of the docs is incomplete, contributions are very welcome