# Re: \[PATCH v5 net-next 06/29\] bpf: add lookup/update/delete/iterate methods to BPF maps

- From: Cong Wang \<hidden\>
- Date: 2014-08-25 21:33:52 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2014/08/4320678
- Thread: https://ratatoskr.run/linux-api/2014/08/4320051/t.md

```text
On Sun, Aug 24, 2014 at 1:21 PM, Alexei Starovoitov [ref] wrote:
> 'maps' is a generic storage of different types for sharing data between kernel
> and userspace.
>
> The maps are accessed from user space via BPF syscall, which has commands:
>
> - create a map with given type and attributes
>   fd = bpf_map_create(map_type, struct nlattr *attr, int len)
>   returns fd or negative error
>
> - lookup key in a given map referenced by fd
>   err = bpf_map_lookup_elem(int fd, void *key, void *value)
>   returns zero and stores found elem into value or negative error
>
> - create or update key/value pair in a given map
>   err = bpf_map_update_elem(int fd, void *key, void *value)
>   returns zero or negative error
>
> - find and delete element by key in a given map
>   err = bpf_map_delete_elem(int fd, void *key)
>
> - iterate map elements (based on input key return next_key)
>   err = bpf_map_get_next_key(int fd, void *key, void *next_key)


I think you need to document the bpf() syscall instead of wrappers on it,
from a developer's point of view. You will anyway need to document a new
syscall with a man page as a general rule.

In the changelog I mean something like:

err = bpf(BPF_MAP_LOOKUP_ELEM, ...);
```