On 02/06/2018 05:37 PM, Pablo Neira Ayuso wrote:
> This patch allows netlink busses to provide object descriptions to
> userspace, in terms of supported attributes and its corresponding
> datatypes.
>
> Userspace sends a requests that looks like:
>
> netlink header
> NLA_DESC_REQ_BUS
> NLA_DESC_REQ_DATA
>
> Where NLA_DESC_REQ_BUS is the netlink bus/protocol number, eg.
> NETLINK_NETFILTER, and NLA_DESC_REQ_DATA is an attribute layout is
> specific to the bus that you are inspecting, this is useful for both
> nfnetlink and genetlink since they need to what subsystem in the bus
> specifically you're targeting to.
>
> Then, the netlink description subsystem response via netlink dump looks
> like this:
>
> netlink header
> NLA_DESC_NUM_OBJS
> NLA_DESC_OBJS (nest)
> NLA_DESC_LIST_ITEM (nest)
> NLA_DESC_OBJ_ID
> NLA_DESC_OBJ_ATTRS_MAX
> NLA_DESC_OBJ_ATTRS (nest)
> NLA_DESC_LIST_ITEM (nest)
> NLA_DESC_ATTR_NUM
> NLA_DESC_ATTR_TYPE
> NLA_DESC_ATTR_LEN
> NLA_DESC_ATTR_MAXVAL
> NLA_DESC_ATTR_NEST_ID
> NLA_DESC_LIST_ITEM (nest)
> ...
>
> Each object definition is composed of an unique ID, the number of
> attributes and the list of attribute definitions.
>
> The NETLINK_DESC bus provides a generic interface to retrieve the list
> of existing objects and its attributes via netlink dump. This new
> description family autoloads module dependencies based on what userspace
> requests.
>
> Each bus needs to register a struct nl_desc_subsys definition, that
> provides the lookup and parse callbacks. These route the description
> requests to the corresponding backend subsystem for genetlink and
> nfnetlink. The lookup callback returns struct nl_desc_objs that provides
> the array of object descriptions.
>
> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> ---
> include/net/net_namespace.h | 1 +
> include/net/nldesc.h | 160 ++++++++++++++
> include/uapi/linux/netlink.h | 67 ++++++
> net/netlink/Makefile | 2 +-
> net/netlink/desc.c | 499 +++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 728 insertions(+), 1 deletion(-)
> create mode 100644 include/net/nldesc.h
> create mode 100644 net/netlink/desc.c
>
> diff --git a/include/net/nldesc.h b/include/net/nldesc.h
> new file mode 100644
> index 000000000000..19306a648f10
> --- /dev/null
> +++ b/include/net/nldesc.h
> @@ -0,0 +1,160 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __NET_NLDESC_H
> +#define __NET_NLDESC_H
> +
> +#include <linux/types.h>
> +
> +struct nl_desc_cmd;
> +struct nl_desc_obj;
> +
> +struct nl_desc_cmds {
> + int max;
> + const struct nl_desc_cmd *table;
> +};
> +
> +struct nl_desc_objs {
> + int max;
> + const struct nl_desc_obj **table;
> +};
> +
> +struct nl_desc_req {
> + u32 bus;
> +};
> +
> +struct net;
> +struct sk_buff;
> +struct nlmsghdr;
> +struct nlattr;
> +
> +
> +/**
> + * struct nl_desc_obj - netlink object description
> + * @id: unique ID to identify this netlink object
> + * @max: number of attributes to describe this object
@attr_max:
> + * @attrs: array of attribute descriptions
> + */
> +struct nl_desc_obj {
> + u16 id;
> + u16 attr_max;
> + const struct nl_desc_attr *attrs;
> +};
Is there a test program for this?
Maybe add it to tools/testing/ ?
thanks,
--
~Randy
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