Re: [PATCH net-next v6 09/15] ethtool: generic handlers for GET requests

Jiri Pirko
2019-07-04T08:49:19Z

Tue, Jul 02, 2019 at 01:50:24PM CEST, mkubecek@suse.cz wrote:

[...]

>+/* The structure holding data for unified processing GET requests consists of
>+ * two parts: request info and reply data. Request info is related to client
>+ * request and for dump request it stays constant through all processing;
>+ * reply data contains data for composing a reply message. When processing
>+ * a dump request, request info is filled only once but reply data is filled
>+ * from scratch for each reply message.
>+ *
>+ * +-----------------+-----------------+------------------+-----------------+
>+ * | common_req_info | specific info | ethnl_reply_data | specific data |
>+ * +-----------------+-----------------+------------------+-----------------+
>+ * |<---------- request info --------->|<----------- reply data ----------->|
>+ *
>+ * Request info always starts at offset 0 with struct ethnl_req_info which
>+ * holds information from parsing the common header. It may be followed by
>+ * other members for request attributes specific for current message type.
>+ * Reply data starts with struct ethnl_reply_data which may be followed by
>+ * other members holding data needed to compose a message.
>+ */
>+

[...]

>+/**
>+ * struct get_request_ops - unified handling of GET requests
>+ * @request_cmd: command id for request (GET)
>+ * @reply_cmd: command id for reply (GET_REPLY)
>+ * @hdr_attr: attribute type for request header
>+ * @max_attr: maximum (top level) attribute type
>+ * @data_size: total length of data structure
>+ * @repdata_offset: offset of "reply data" part (struct ethnl_reply_data)

For example, this looks quite scarry for me. You have one big chunk of
data (according to the scheme above) specific for cmd with reply starting
at arbitrary offset.

>+ * @request_policy: netlink policy for message contents
>+ * @header_policy: (optional) netlink policy for request header
>+ * @default_infomask: default infomask (to use if none specified)
>+ * @all_reqflags: allowed request specific flags
>+ * @allow_nodev_do: allow non-dump request with no device identification
>+ * @parse_request:
>+ * Parse request except common header (struct ethnl_req_info). Common
>+ * header is already filled on entry, the rest up to @repdata_offset
>+ * is zero initialized. This callback should only modify type specific
>+ * request info by parsed attributes from request message.
>+ * @prepare_data:
>+ * Retrieve and prepare data needed to compose a reply message. Calls to
>+ * ethtool_ops handlers should be limited to this callback. Common reply
>+ * data (struct ethnl_reply_data) is filled on entry, type specific part
>+ * after it is zero initialized. This callback should only modify the
>+ * type specific part of reply data. Device identification from struct
>+ * ethnl_reply_data is to be used as for dump requests, it iterates
>+ * through network devices which common_req_info::dev points to the
>+ * device from client request.
>+ * @reply_size:
>+ * Estimate reply message size. Returned value must be sufficient for
>+ * message payload without common reply header. The callback may returned
>+ * estimate higher than actual message size if exact calculation would
>+ * not be worth the saved memory space.
>+ * @fill_reply:
>+ * Fill reply message payload (except for common header) from reply data.
>+ * The callback must not generate more payload than previously called
>+ * ->reply_size() estimated.
>+ * @cleanup:
>+ * Optional cleanup called when reply data is no longer needed. Can be
>+ * used e.g. to free any additional data structures outside the main
>+ * structure which were allocated by ->prepare_data(). When processing
>+ * dump requests, ->cleanup() is called for each message.
>+ *
>+ * Description of variable parts of GET request handling when using the unified
>+ * infrastructure. When used, a pointer to an instance of this structure is to
>+ * be added to &get_requests array and generic handlers ethnl_get_doit(),
>+ * ethnl_get_dumpit(), ethnl_get_start() and ethnl_get_done() used in
>+ * @ethnl_genl_ops
>+ */
>+struct get_request_ops {
>+ u8 request_cmd;
>+ u8 reply_cmd;
>+ u16 hdr_attr;
>+ unsigned int max_attr;
>+ unsigned int data_size;
>+ unsigned int repdata_offset;
>+ const struct nla_policy *request_policy;
>+ const struct nla_policy *header_policy;
>+ u32 default_infomask;
>+ u32 all_reqflags;
>+ bool allow_nodev_do;
>+
>+ int (*parse_request)(struct ethnl_req_info *req_info,
>+ struct nlattr **tb,
>+ struct netlink_ext_ack *extack);
>+ int (*prepare_data)(struct ethnl_req_info *req_info,
>+ struct genl_info *info);
>+ int (*reply_size)(const struct ethnl_req_info *req_info);
>+ int (*fill_reply)(struct sk_buff *skb,
>+ const struct ethnl_req_info *req_info);
>+ void (*cleanup)(struct ethnl_req_info *req_info);
>+};
>+
> #endif /* _NET_ETHTOOL_NETLINK_H */
>--
>2.22.0
>