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

From: Cong Wang
Date: Mon Aug 25 2014 - 17:33:55 EST

On Sun, Aug 24, 2014 at 1:21 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> 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, ...);
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