On 12/9/22 3:24 AM, Donald Hunter wrote:
Add documentation for the BPF_MAP_TYPE_SK_STORAGE including
kernel version introduced, usage and examples.
Thanks for writing the doc for sk_storage!
+User space
+----------
+
+bpf_map_update_elem()
+~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: c
+
+ int bpf_map_update_elem(int map_fd, const void *key, const void *value, __u64 flags)
+
+Socket-local storage for the socket identified by ``key`` belonging to
+``map_fd`` can be added or updated using the ``bpf_map_update_elem()`` libbpf > +function. ``key`` must be a pointer to a valid ``fd`` in the user space
+program. The ``flags`` parameter can be used to control the update behaviour:
The "``key`` belonging to ``map_fd``" seems confusing. Also, it is useful to
highlight the ``key`` is a _socket_ ``fd``.
May be something like:
A socket-local storage can be added/updated locally to a socket identified by a
_socket_ ``fd`` stored in the pointer ``key``. The pointer ``value`` has the
data to be added/updated to the socket ``fd``. The type and size of ``value``
should be the same as the value type of the map definition.
Feel free to rephrase the above in a better way.
+
+- ``BPF_ANY`` will create storage for ``fd`` or update existing storage.
+- ``BPF_NOEXIST`` will create storage for ``fd`` only if it did not already
+ exist, otherwise the call will fail with ``-EEXIST``.
+- ``BPF_EXIST`` will update existing storage for ``fd`` if it already exists,
+ otherwise the call will fail with ``-ENOENT``.
+
+Returns ``0`` on success, or negative error in case of failure.
+
+bpf_map_lookup_elem()
+~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: c
+
+ int bpf_map_lookup_elem(int map_fd, const void *key, void *value)
+
+Socket-local storage for the socket identified by ``key`` belonging to
+``map_fd`` can be retrieved using the ``bpf_map_lookup_elem()`` libbpf
+function. ``key`` must be a pointer to a valid ``fd`` in the user space
Same here.
+program. Returns ``0`` on success, or negative error in case of failure.
+
+bpf_map_delete_elem()
+~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: c
+
+ int bpf_map_delete_elem(int map_fd, const void *key)
+
+Socket-local storage for the socket identified by ``key`` belonging to
+``map_fd`` can be deleted using the ``bpf_map_delete_elem()`` libbpf
+function. Returns ``0`` on success, or negative error in case of failure.
Same here.
