Merge branch 'ethtool-netlink-part-one'

Michal Kubecek says:

====================
ethtool netlink interface, part 1

This is first part of netlink based alternative userspace interface for
ethtool. It aims to address some long known issues with the ioctl
interface, mainly lack of extensibility, raciness, limited error reporting
and absence of notifications. The goal is to allow userspace ethtool
utility to provide all features it currently does but without using the
ioctl interface. However, some features provided by ethtool ioctl API will
be available through other netlink interfaces (rtnetlink, devlink) if it's
more appropriate.

The interface uses generic netlink family "ethtool" and provides multicast
group "monitor" which is used for notifications. Documentation for the
interface is in Documentation/networking/ethtool-netlink.rst file. The
netlink interface is optional, it is built when CONFIG_ETHTOOL_NETLINK
(bool) option is enabled.

There are three types of request messages distinguished by suffix "_GET"
(query for information), "_SET" (modify parameters) and "_ACT" (perform an
action). Kernel reply messages have name with additional suffix "_REPLY"
(e.g. ETHTOOL_MSG_SETTINGS_GET_REPLY). Most "_SET" and "_ACT" message types
do not have matching reply type as only some of them need additional reply
data beyond numeric error code and extack. Kernel also broadcasts
notification messages ("_NTF" suffix) on changes.

Basic concepts:

- make extensions easier not only by allowing new attributes but also by
  imposing as few artificial limits as possible, e.g. by using arbitrary
  size bit sets for most bitmap attributes or by not using fixed size
  strings
- use extack for error reporting and warnings
- send netlink notifications on changes (even if they were done using the
  ioctl interface) and actions
- avoid the racy read/modify/write cycle between kernel and userspace by
  sending only attributes which userspace wants to change; there is still
  a read/modify/write cycle between generic kernel code and ethtool_ops
  handler in NIC driver but it is only in kernel and under RTNL lock
- reduce the number of name lists that need to be kept in sync between
  kernel and userspace (e.g. recognized link modes)
- where feasible, allow dump requests to query specific information for all
  network devices
- as parsing and generating netlink messages is more complicated than
  simply copying data structures between userspace API and ethtool_ops
  handlers (which most ioctl commands do), split the code into multiple
  files in net/ethtool directory; move net/core/ethtool.c also to this
  directory and rename it to ioctl.c

Changes between v8 and v9:

- fix ethnl_update_u8()
- fix description of ETHTOOL_A_LINKSTATE_LINK in rst file
- add explanation of verbose vs. compact bitset usage to documentation
- link ethtool-netlink.rst into toctree

Main changes between v7 and v8:

- preliminary patches sent as a separate series (already in net-next)
- split notification related changes out of _SET patches
- drop request specific flags from common header
- use FLAG/flag rather than GFLAG/gflag for global flags (as there are
  only global flags now)
- allow device names up to ALTIFNAMSIZ characters
- rename ETHTOOL_A_BITSET_LIST to ETHTOOL_A_BITSET_NOMASK
- rename ETHTOOL_A_BIT{,S}_* to ETHTOOL_A_BITSET_BIT{,S}_*
- use standard bitset helpers for link modes (rather than in-place
  conversion)
- use "default" rather than "standard" for unified _GET handlers
- fixed 64-bit big endian bitset code

Main changes between v6 and v7:

- split complex messages into small single purpose ones (drop info and
  request masks and one level of nesting)
- separate request information and reply data into two structures
- refactor bitset handling (no simultaneous u32/ulong handling but avoid
  kmalloc() except for long bitmaps on 64-bit big endian architectures)
- use only fixed size strings internally (will be replaced by char *
  eventually but that will require rewriting also existing ioctl code)
- rework ethnl_update_* helpers to return error code
- rename request flag constants (to ETHTOOL_[GR]FLAG_ prefix)
- convert documentation to rst

Main changes between v5 and v6:

- use ETHTOOL_MSG_ prefix for message types
- replace ETHA_ prefix for netlink attributes by ETHTOOL_A_
- replace ETH_x_IM_y for infomask bits by ETHTOOL_IM_x_y
- split GET reply types from SET requests and notifications
- split kernel and userspace message types into different enums
- remove INFO_GET requests from submitted part
- drop EVENT notifications (use rtnetlink and on-demand string set load)
- reorganize patches to reduce the number of intermitent warnings
- unify request/reply header and its processing
- another nest around strings in a string set for consistency
- more consistent identifier naming
- coding style cleanup
- get rid of some of the helpers
- set bad attribute in extack where applicable
- various bug fixes
- improve documentation and code comments, more kerneldoc comments
- more verbose commit messages

Changes between v4 and v5:

- do not panic on failed initialization, only WARN()

Main changes between RFC v3 and v4:

- use more kerneldoc style comments
- strict attribute policy checking
- use macros for tables of link mode names and parameters
- provide permanent hardware address in rtnetlink
- coding style cleanup
- split too long patches, reorder
- wrap more ETHA_SETTINGS_* attributes in nests
- add also some SET_* implementation into submitted part

Main changes between RFC v2 and RFC v3:

- do not allow building as a module (no netdev notifiers needed)
- drop some obsolete fields
- add permanent hw address, timestamping and private flags support
- rework bitset handling to get rid of variable length arrays
- notify monitor on device renames
- restructure GET_SETTINGS/SET_SETTINGS messages
- split too long patches and submit only first part of the series

Main changes between RFC v1 and RFC v2:

- support dumps for all "get" requests
- provide notifications for changes related to supported request types
- support getting string sets (both global and per device)
- support getting/setting device features
- get rid of family specific header, everything passed as attributes
- split netlink code into multiple files in net/ethtool/ directory
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

19 files changed, 3683 insertions, 55 deletions

diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
new file mode 100644
index 000000000000..c60afba69e3c
--- /dev/null
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -0,0 +1,520 @@
+=============================
+Netlink interface for ethtool
+=============================
+
+
+Basic information
+=================
+
+Netlink interface for ethtool uses generic netlink family ``ethtool``
+(userspace application should use macros ``ETHTOOL_GENL_NAME`` and
+``ETHTOOL_GENL_VERSION`` defined in ``<linux/ethtool_netlink.h>`` uapi
+header). This family does not use a specific header, all information in
+requests and replies is passed using netlink attributes.
+
+The ethtool netlink interface uses extended ACK for error and warning
+reporting, userspace application developers are encouraged to make these
+messages available to user in a suitable way.
+
+Requests can be divided into three categories: "get" (retrieving information),
+"set" (setting parameters) and "action" (invoking an action).
+
+All "set" and "action" type requests require admin privileges
+(``CAP_NET_ADMIN`` in the namespace). Most "get" type requests are allowed for
+anyone but there are exceptions (where the response contains sensitive
+information). In some cases, the request as such is allowed for anyone but
+unprivileged users have attributes with sensitive information (e.g.
+wake-on-lan password) omitted.
+
+
+Conventions
+===========
+
+Attributes which represent a boolean value usually use NLA_U8 type so that we
+can distinguish three states: "on", "off" and "not present" (meaning the
+information is not available in "get" requests or value is not to be changed
+in "set" requests). For these attributes, the "true" value should be passed as
+number 1 but any non-zero value should be understood as "true" by recipient.
+In the tables below, "bool" denotes NLA_U8 attributes interpreted in this way.
+
+In the message structure descriptions below, if an attribute name is suffixed
+with "+", parent nest can contain multiple attributes of the same type. This
+implements an array of entries.
+
+
+Request header
+==============
+
+Each request or reply message contains a nested attribute with common header.
+Structure of this header is
+
+  ==============================  ======  =============================
+  ``ETHTOOL_A_HEADER_DEV_INDEX``  u32     device ifindex
+  ``ETHTOOL_A_HEADER_DEV_NAME``   string  device name
+  ``ETHTOOL_A_HEADER_FLAGS``      u32     flags common for all requests
+  ==============================  ======  =============================
+
+``ETHTOOL_A_HEADER_DEV_INDEX`` and ``ETHTOOL_A_HEADER_DEV_NAME`` identify the
+device message relates to. One of them is sufficient in requests, if both are
+used, they must identify the same device. Some requests, e.g. global string
+sets, do not require device identification. Most ``GET`` requests also allow
+dump requests without device identification to query the same information for
+all devices providing it (each device in a separate message).
+
+``ETHTOOL_A_HEADER_FLAGS`` is a bitmap of request flags common for all request
+types. The interpretation of these flags is the same for all request types but
+the flags may not apply to requests. Recognized flags are:
+
+  =================================  ===================================
+  ``ETHTOOL_FLAG_COMPACT_BITSETS``   use compact format bitsets in reply
+  ``ETHTOOL_FLAG_OMIT_REPLY``        omit optional reply (_SET and _ACT)
+  =================================  ===================================
+
+New request flags should follow the general idea that if the flag is not set,
+the behaviour is backward compatible, i.e. requests from old clients not aware
+of the flag should be interpreted the way the client expects. A client must
+not set flags it does not understand.
+
+
+Bit sets
+========
+
+For short bitmaps of (reasonably) fixed length, standard ``NLA_BITFIELD32``
+type is used. For arbitrary length bitmaps, ethtool netlink uses a nested
+attribute with contents of one of two forms: compact (two binary bitmaps
+representing bit values and mask of affected bits) and bit-by-bit (list of
+bits identified by either index or name).
+
+Verbose (bit-by-bit) bitsets allow sending symbolic names for bits together
+with their values which saves a round trip (when the bitset is passed in a
+request) or at least a second request (when the bitset is in a reply). This is
+useful for one shot applications like traditional ethtool command. On the
+other hand, long running applications like ethtool monitor (displaying
+notifications) or network management daemons may prefer fetching the names
+only once and using compact form to save message size. Notifications from
+ethtool netlink interface always use compact form for bitsets.
+
+A bitset can represent either a value/mask pair (``ETHTOOL_A_BITSET_NOMASK``
+not set) or a single bitmap (``ETHTOOL_A_BITSET_NOMASK`` set). In requests
+modifying a bitmap, the former changes the bit set in mask to values set in
+value and preserves the rest; the latter sets the bits set in the bitmap and
+clears the rest.
+
+Compact form: nested (bitset) atrribute contents:
+
+  ============================  ======  ============================
+  ``ETHTOOL_A_BITSET_NOMASK``   flag    no mask, only a list
+  ``ETHTOOL_A_BITSET_SIZE``     u32     number of significant bits
+  ``ETHTOOL_A_BITSET_VALUE``    binary  bitmap of bit values
+  ``ETHTOOL_A_BITSET_MASK``     binary  bitmap of valid bits
+  ============================  ======  ============================
+
+Value and mask must have length at least ``ETHTOOL_A_BITSET_SIZE`` bits
+rounded up to a multiple of 32 bits. They consist of 32-bit words in host byte
+order, words ordered from least significant to most significant (i.e. the same
+way as bitmaps are passed with ioctl interface).
+
+For compact form, ``ETHTOOL_A_BITSET_SIZE`` and ``ETHTOOL_A_BITSET_VALUE`` are
+mandatory. ``ETHTOOL_A_BITSET_MASK`` attribute is mandatory if
+``ETHTOOL_A_BITSET_NOMASK`` is not set (bitset represents a value/mask pair);
+if ``ETHTOOL_A_BITSET_NOMASK`` is not set, ``ETHTOOL_A_BITSET_MASK`` is not
+allowed (bitset represents a single bitmap.
+
+Kernel bit set length may differ from userspace length if older application is
+used on newer kernel or vice versa. If userspace bitmap is longer, an error is
+issued only if the request actually tries to set values of some bits not
+recognized by kernel.
+
+Bit-by-bit form: nested (bitset) attribute contents:
+
+ +------------------------------------+--------+-----------------------------+
+ | ``ETHTOOL_A_BITSET_NOMASK``        | flag   | no mask, only a list        |
+ +------------------------------------+--------+-----------------------------+
+ | ``ETHTOOL_A_BITSET_SIZE``          | u32    | number of significant bits  |
+ +------------------------------------+--------+-----------------------------+
+ | ``ETHTOOL_A_BITSET_BITS``          | nested | array of bits               |
+ +-+----------------------------------+--------+-----------------------------+
+ | | ``ETHTOOL_A_BITSET_BITS_BIT+``   | nested | one bit                     |
+ +-+-+--------------------------------+--------+-----------------------------+
+ | | | ``ETHTOOL_A_BITSET_BIT_INDEX`` | u32    | bit index (0 for LSB)       |
+ +-+-+--------------------------------+--------+-----------------------------+
+ | | | ``ETHTOOL_A_BITSET_BIT_NAME``  | string | bit name                    |
+ +-+-+--------------------------------+--------+-----------------------------+
+ | | | ``ETHTOOL_A_BITSET_BIT_VALUE`` | flag   | present if bit is set       |
+ +-+-+--------------------------------+--------+-----------------------------+
+
+Bit size is optional for bit-by-bit form. ``ETHTOOL_A_BITSET_BITS`` nest can
+only contain ``ETHTOOL_A_BITSET_BITS_BIT`` attributes but there can be an
+arbitrary number of them.  A bit may be identified by its index or by its
+name. When used in requests, listed bits are set to 0 or 1 according to
+``ETHTOOL_A_BITSET_BIT_VALUE``, the rest is preserved. A request fails if
+index exceeds kernel bit length or if name is not recognized.
+
+When ``ETHTOOL_A_BITSET_NOMASK`` flag is present, bitset is interpreted as
+a simple bitmap. ``ETHTOOL_A_BITSET_BIT_VALUE`` attributes are not used in
+such case. Such bitset represents a bitmap with listed bits set and the rest
+zero.
+
+In requests, application can use either form. Form used by kernel in reply is
+determined by ``ETHTOOL_FLAG_COMPACT_BITSETS`` flag in flags field of request
+header. Semantics of value and mask depends on the attribute.
+
+
+List of message types
+=====================
+
+All constants identifying message types use ``ETHTOOL_CMD_`` prefix and suffix
+according to message purpose:
+
+  ==============    ======================================
+  ``_GET``          userspace request to retrieve data
+  ``_SET``          userspace request to set data
+  ``_ACT``          userspace request to perform an action
+  ``_GET_REPLY``    kernel reply to a ``GET`` request
+  ``_SET_REPLY``    kernel reply to a ``SET`` request
+  ``_ACT_REPLY``    kernel reply to an ``ACT`` request
+  ``_NTF``          kernel notification
+  ==============    ======================================
+
+Userspace to kernel:
+
+  ===================================== ================================
+  ``ETHTOOL_MSG_STRSET_GET``            get string set
+  ``ETHTOOL_MSG_LINKINFO_GET``          get link settings
+  ``ETHTOOL_MSG_LINKINFO_SET``          set link settings
+  ``ETHTOOL_MSG_LINKMODES_GET``         get link modes info
+  ``ETHTOOL_MSG_LINKMODES_SET``         set link modes info
+  ``ETHTOOL_MSG_LINKSTATE_GET``         get link state
+  ===================================== ================================
+
+Kernel to userspace:
+
+  ===================================== ================================
+  ``ETHTOOL_MSG_STRSET_GET_REPLY``      string set contents
+  ``ETHTOOL_MSG_LINKINFO_GET_REPLY``    link settings
+  ``ETHTOOL_MSG_LINKINFO_NTF``          link settings notification
+  ``ETHTOOL_MSG_LINKMODES_GET_REPLY``   link modes info
+  ``ETHTOOL_MSG_LINKMODES_NTF``         link modes notification
+  ``ETHTOOL_MSG_LINKSTATE_GET_REPLY``   link state info
+  ===================================== ================================
+
+``GET`` requests are sent by userspace applications to retrieve device
+information. They usually do not contain any message specific attributes.
+Kernel replies with corresponding "GET_REPLY" message. For most types, ``GET``
+request with ``NLM_F_DUMP`` and no device identification can be used to query
+the information for all devices supporting the request.
+
+If the data can be also modified, corresponding ``SET`` message with the same
+layout as corresponding ``GET_REPLY`` is used to request changes. Only
+attributes where a change is requested are included in such request (also, not
+all attributes may be changed). Replies to most ``SET`` request consist only
+of error code and extack; if kernel provides additional data, it is sent in
+the form of corresponding ``SET_REPLY`` message which can be suppressed by
+setting ``ETHTOOL_FLAG_OMIT_REPLY`` flag in request header.
+
+Data modification also triggers sending a ``NTF`` message with a notification.
+These usually bear only a subset of attributes which was affected by the
+change. The same notification is issued if the data is modified using other
+means (mostly ioctl ethtool interface). Unlike notifications from ethtool
+netlink code which are only sent if something actually changed, notifications
+triggered by ioctl interface may be sent even if the request did not actually
+change any data.
+
+``ACT`` messages request kernel (driver) to perform a specific action. If some
+information is reported by kernel (which can be suppressed by setting
+``ETHTOOL_FLAG_OMIT_REPLY`` flag in request header), the reply takes form of
+an ``ACT_REPLY`` message. Performing an action also triggers a notification
+(``NTF`` message).
+
+Later sections describe the format and semantics of these messages.
+
+
+STRSET_GET
+==========
+
+Requests contents of a string set as provided by ioctl commands
+``ETHTOOL_GSSET_INFO`` and ``ETHTOOL_GSTRINGS.`` String sets are not user
+writeable so that the corresponding ``STRSET_SET`` message is only used in
+kernel replies. There are two types of string sets: global (independent of
+a device, e.g. device feature names) and device specific (e.g. device private
+flags).
+
+Request contents:
+
+ +---------------------------------------+--------+------------------------+
+ | ``ETHTOOL_A_STRSET_HEADER``           | nested | request header         |
+ +---------------------------------------+--------+------------------------+
+ | ``ETHTOOL_A_STRSET_STRINGSETS``       | nested | string set to request  |
+ +-+-------------------------------------+--------+------------------------+
+ | | ``ETHTOOL_A_STRINGSETS_STRINGSET+`` | nested | one string set         |
+ +-+-+-----------------------------------+--------+------------------------+
+ | | | ``ETHTOOL_A_STRINGSET_ID``        | u32    | set id                 |
+ +-+-+-----------------------------------+--------+------------------------+
+
+Kernel response contents:
+
+ +---------------------------------------+--------+-----------------------+
+ | ``ETHTOOL_A_STRSET_HEADER``           | nested | reply header          |
+ +---------------------------------------+--------+-----------------------+
+ | ``ETHTOOL_A_STRSET_STRINGSETS``       | nested | array of string sets  |
+ +-+-------------------------------------+--------+-----------------------+
+ | | ``ETHTOOL_A_STRINGSETS_STRINGSET+`` | nested | one string set        |
+ +-+-+-----------------------------------+--------+-----------------------+
+ | | | ``ETHTOOL_A_STRINGSET_ID``        | u32    | set id                |
+ +-+-+-----------------------------------+--------+-----------------------+
+ | | | ``ETHTOOL_A_STRINGSET_COUNT``     | u32    | number of strings     |
+ +-+-+-----------------------------------+--------+-----------------------+
+ | | | ``ETHTOOL_A_STRINGSET_STRINGS``   | nested | array of strings      |
+ +-+-+-+---------------------------------+--------+-----------------------+
+ | | | | ``ETHTOOL_A_STRINGS_STRING+``   | nested | one string            |
+ +-+-+-+-+-------------------------------+--------+-----------------------+
+ | | | | | ``ETHTOOL_A_STRING_INDEX``    | u32    | string index          |
+ +-+-+-+-+-------------------------------+--------+-----------------------+
+ | | | | | ``ETHTOOL_A_STRING_VALUE``    | string | string value          |
+ +-+-+-+-+-------------------------------+--------+-----------------------+
+ | ``ETHTOOL_A_STRSET_COUNTS_ONLY``      | flag   | return only counts    |
+ +---------------------------------------+--------+-----------------------+
+
+Device identification in request header is optional. Depending on its presence
+a and ``NLM_F_DUMP`` flag, there are three type of ``STRSET_GET`` requests:
+
+ - no ``NLM_F_DUMP,`` no device: get "global" stringsets
+ - no ``NLM_F_DUMP``, with device: get string sets related to the device
+ - ``NLM_F_DUMP``, no device: get device related string sets for all devices
+
+If there is no ``ETHTOOL_A_STRSET_STRINGSETS`` array, all string sets of
+requested type are returned, otherwise only those specified in the request.
+Flag ``ETHTOOL_A_STRSET_COUNTS_ONLY`` tells kernel to only return string
+counts of the sets, not the actual strings.
+
+
+LINKINFO_GET
+============
+
+Requests link settings as provided by ``ETHTOOL_GLINKSETTINGS`` except for
+link modes and autonegotiation related information. The request does not use
+any attributes.
+
+Request contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKINFO_HEADER``         nested  request header
+  ====================================  ======  ==========================
+
+Kernel response contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKINFO_HEADER``         nested  reply header
+  ``ETHTOOL_A_LINKINFO_PORT``           u8      physical port
+  ``ETHTOOL_A_LINKINFO_PHYADDR``        u8      phy MDIO address
+  ``ETHTOOL_A_LINKINFO_TP_MDIX``        u8      MDI(-X) status
+  ``ETHTOOL_A_LINKINFO_TP_MDIX_CTRL``   u8      MDI(-X) control
+  ``ETHTOOL_A_LINKINFO_TRANSCEIVER``    u8      transceiver
+  ====================================  ======  ==========================
+
+Attributes and their values have the same meaning as matching members of the
+corresponding ioctl structures.
+
+``LINKINFO_GET`` allows dump requests (kernel returns reply message for all
+devices supporting the request).
+
+
+LINKINFO_SET
+============
+
+``LINKINFO_SET`` request allows setting some of the attributes reported by
+``LINKINFO_GET``.
+
+Request contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKINFO_HEADER``         nested  request header
+  ``ETHTOOL_A_LINKINFO_PORT``           u8      physical port
+  ``ETHTOOL_A_LINKINFO_PHYADDR``        u8      phy MDIO address
+  ``ETHTOOL_A_LINKINFO_TP_MDIX_CTRL``   u8      MDI(-X) control
+  ====================================  ======  ==========================
+
+MDI(-X) status and transceiver cannot be set, request with the corresponding
+attributes is rejected.
+
+
+LINKMODES_GET
+=============
+
+Requests link modes (supported, advertised and peer advertised) and related
+information (autonegotiation status, link speed and duplex) as provided by
+``ETHTOOL_GLINKSETTINGS``. The request does not use any attributes.
+
+Request contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKMODES_HEADER``        nested  request header
+  ====================================  ======  ==========================
+
+Kernel response contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKMODES_HEADER``        nested  reply header
+  ``ETHTOOL_A_LINKMODES_AUTONEG``       u8      autonegotiation status
+  ``ETHTOOL_A_LINKMODES_OURS``          bitset  advertised link modes
+  ``ETHTOOL_A_LINKMODES_PEER``          bitset  partner link modes
+  ``ETHTOOL_A_LINKMODES_SPEED``         u32     link speed (Mb/s)
+  ``ETHTOOL_A_LINKMODES_DUPLEX``        u8      duplex mode
+  ====================================  ======  ==========================
+
+For ``ETHTOOL_A_LINKMODES_OURS``, value represents advertised modes and mask
+represents supported modes. ``ETHTOOL_A_LINKMODES_PEER`` in the reply is a bit
+list.
+
+``LINKMODES_GET`` allows dump requests (kernel returns reply messages for all
+devices supporting the request).
+
+
+LINKMODES_SET
+=============
+
+Request contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKMODES_HEADER``        nested  request header
+  ``ETHTOOL_A_LINKMODES_AUTONEG``       u8      autonegotiation status
+  ``ETHTOOL_A_LINKMODES_OURS``          bitset  advertised link modes
+  ``ETHTOOL_A_LINKMODES_PEER``          bitset  partner link modes
+  ``ETHTOOL_A_LINKMODES_SPEED``         u32     link speed (Mb/s)
+  ``ETHTOOL_A_LINKMODES_DUPLEX``        u8      duplex mode
+  ====================================  ======  ==========================
+
+``ETHTOOL_A_LINKMODES_OURS`` bit set allows setting advertised link modes. If
+autonegotiation is on (either set now or kept from before), advertised modes
+are not changed (no ``ETHTOOL_A_LINKMODES_OURS`` attribute) and at least one
+of speed and duplex is specified, kernel adjusts advertised modes to all
+supported modes matching speed, duplex or both (whatever is specified). This
+autoselection is done on ethtool side with ioctl interface, netlink interface
+is supposed to allow requesting changes without knowing what exactly kernel
+supports.
+
+
+LINKSTATE_GET
+=============
+
+Requests link state information. At the moment, only link up/down flag (as
+provided by ``ETHTOOL_GLINK`` ioctl command) is provided but some future
+extensions are planned (e.g. link down reason). This request does not have any
+attributes.
+
+Request contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKSTATE_HEADER``        nested  request header
+  ====================================  ======  ==========================
+
+Kernel response contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKSTATE_HEADER``        nested  reply header
+  ``ETHTOOL_A_LINKSTATE_LINK``          bool    link state (up/down)
+  ====================================  ======  ==========================
+
+For most NIC drivers, the value of ``ETHTOOL_A_LINKSTATE_LINK`` returns
+carrier flag provided by ``netif_carrier_ok()`` but there are drivers which
+define their own handler.
+
+``LINKSTATE_GET`` allows dump requests (kernel returns reply messages for all
+devices supporting the request).
+
+
+Request translation
+===================
+
+The following table maps ioctl commands to netlink commands providing their
+functionality. Entries with "n/a" in right column are commands which do not
+have their netlink replacement yet.
+
+  =================================== =====================================
+  ioctl command                       netlink command
+  =================================== =====================================
+  ``ETHTOOL_GSET``                    ``ETHTOOL_MSG_LINKINFO_GET``
+                                      ``ETHTOOL_MSG_LINKMODES_GET``
+  ``ETHTOOL_SSET``                    ``ETHTOOL_MSG_LINKINFO_SET``
+                                      ``ETHTOOL_MSG_LINKMODES_SET``
+  ``ETHTOOL_GDRVINFO``                n/a
+  ``ETHTOOL_GREGS``                   n/a
+  ``ETHTOOL_GWOL``                    n/a
+  ``ETHTOOL_SWOL``                    n/a
+  ``ETHTOOL_GMSGLVL``                 n/a
+  ``ETHTOOL_SMSGLVL``                 n/a
+  ``ETHTOOL_NWAY_RST``                n/a
+  ``ETHTOOL_GLINK``                   ``ETHTOOL_MSG_LINKSTATE_GET``
+  ``ETHTOOL_GEEPROM``                 n/a
+  ``ETHTOOL_SEEPROM``                 n/a
+  ``ETHTOOL_GCOALESCE``               n/a
+  ``ETHTOOL_SCOALESCE``               n/a
+  ``ETHTOOL_GRINGPARAM``              n/a
+  ``ETHTOOL_SRINGPARAM``              n/a
+  ``ETHTOOL_GPAUSEPARAM``             n/a
+  ``ETHTOOL_SPAUSEPARAM``             n/a
+  ``ETHTOOL_GRXCSUM``                 n/a
+  ``ETHTOOL_SRXCSUM``                 n/a
+  ``ETHTOOL_GTXCSUM``                 n/a
+  ``ETHTOOL_STXCSUM``                 n/a
+  ``ETHTOOL_GSG``                     n/a
+  ``ETHTOOL_SSG``                     n/a
+  ``ETHTOOL_TEST``                    n/a
+  ``ETHTOOL_GSTRINGS``                ``ETHTOOL_MSG_STRSET_GET``
+  ``ETHTOOL_PHYS_ID``                 n/a
+  ``ETHTOOL_GSTATS``                  n/a
+  ``ETHTOOL_GTSO``                    n/a
+  ``ETHTOOL_STSO``                    n/a
+  ``ETHTOOL_GPERMADDR``               rtnetlink ``RTM_GETLINK``
+  ``ETHTOOL_GUFO``                    n/a
+  ``ETHTOOL_SUFO``                    n/a
+  ``ETHTOOL_GGSO``                    n/a
+  ``ETHTOOL_SGSO``                    n/a
+  ``ETHTOOL_GFLAGS``                  n/a
+  ``ETHTOOL_SFLAGS``                  n/a
+  ``ETHTOOL_GPFLAGS``                 n/a
+  ``ETHTOOL_SPFLAGS``                 n/a
+  ``ETHTOOL_GRXFH``                   n/a
+  ``ETHTOOL_SRXFH``                   n/a
+  ``ETHTOOL_GGRO``                    n/a
+  ``ETHTOOL_SGRO``                    n/a
+  ``ETHTOOL_GRXRINGS``                n/a
+  ``ETHTOOL_GRXCLSRLCNT``             n/a
+  ``ETHTOOL_GRXCLSRULE``              n/a
+  ``ETHTOOL_GRXCLSRLALL``             n/a
+  ``ETHTOOL_SRXCLSRLDEL``             n/a
+  ``ETHTOOL_SRXCLSRLINS``             n/a
+  ``ETHTOOL_FLASHDEV``                n/a
+  ``ETHTOOL_RESET``                   n/a
+  ``ETHTOOL_SRXNTUPLE``               n/a
+  ``ETHTOOL_GRXNTUPLE``               n/a
+  ``ETHTOOL_GSSET_INFO``              ``ETHTOOL_MSG_STRSET_GET``
+  ``ETHTOOL_GRXFHINDIR``              n/a
+  ``ETHTOOL_SRXFHINDIR``              n/a
+  ``ETHTOOL_GFEATURES``               n/a
+  ``ETHTOOL_SFEATURES``               n/a
+  ``ETHTOOL_GCHANNELS``               n/a
+  ``ETHTOOL_SCHANNELS``               n/a
+  ``ETHTOOL_SET_DUMP``                n/a
+  ``ETHTOOL_GET_DUMP_FLAG``           n/a
+  ``ETHTOOL_GET_DUMP_DATA``           n/a
+  ``ETHTOOL_GET_TS_INFO``             n/a
+  ``ETHTOOL_GMODULEINFO``             n/a
+  ``ETHTOOL_GMODULEEEPROM``           n/a
+  ``ETHTOOL_GEEE``                    n/a
+  ``ETHTOOL_SEEE``                    n/a
+  ``ETHTOOL_GRSSH``                   n/a
+  ``ETHTOOL_SRSSH``                   n/a
+  ``ETHTOOL_GTUNABLE``                n/a
+  ``ETHTOOL_STUNABLE``                n/a
+  ``ETHTOOL_GPHYSTATS``               n/a
+  ``ETHTOOL_PERQUEUE``                n/a
+  ``ETHTOOL_GLINKSETTINGS``           ``ETHTOOL_MSG_LINKINFO_GET``
+                                      ``ETHTOOL_MSG_LINKMODES_GET``
+  ``ETHTOOL_SLINKSETTINGS``           ``ETHTOOL_MSG_LINKINFO_SET``
+                                      ``ETHTOOL_MSG_LINKMODES_SET``
+  ``ETHTOOL_PHY_GTUNABLE``            n/a
+  ``ETHTOOL_PHY_STUNABLE``            n/a
+  ``ETHTOOL_GFECPARAM``               n/a
+  ``ETHTOOL_SFECPARAM``               n/a
+  =================================== =====================================
diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst
index 5acab1290e03..bee73be7af93 100644
--- a/Documentation/networking/index.rst
+++ b/Documentation/networking/index.rst
@@ -16,6 +16,7 @@ Contents:
    devlink-info-versions
    devlink-trap
    devlink-trap-netdevsim
+   ethtool-netlink
    ieee802154
    j1939
    kapi
diff --git a/include/linux/ethtool_netlink.h b/include/linux/ethtool_netlink.h
new file mode 100644
index 000000000000..d01b77887f82
--- /dev/null
+++ b/include/linux/ethtool_netlink.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_ETHTOOL_NETLINK_H_
+#define _LINUX_ETHTOOL_NETLINK_H_
+
+#include <uapi/linux/ethtool_netlink.h>
+#include <linux/ethtool.h>
+#include <linux/netdevice.h>
+
+#define __ETHTOOL_LINK_MODE_MASK_NWORDS \
+	DIV_ROUND_UP(__ETHTOOL_LINK_MODE_MASK_NBITS, 32)
+
+enum ethtool_multicast_groups {
+	ETHNL_MCGRP_MONITOR,
+};
+
+#endif /* _LINUX_ETHTOOL_NETLINK_H_ */
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 469a297b58c0..f007155ae8f4 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4393,6 +4393,15 @@ struct netdev_notifier_bonding_info {
 void netdev_bonding_info_change(struct net_device *dev,
 				struct netdev_bonding_info *bonding_info);
 
+#if IS_ENABLED(CONFIG_ETHTOOL_NETLINK)
+void ethtool_notify(struct net_device *dev, unsigned int cmd, const void *data);
+#else
+static inline void ethtool_notify(struct net_device *dev, unsigned int cmd,
+				  const void *data)
+{
+}
+#endif
+
 static inline
 struct sk_buff *skb_gso_segment(struct sk_buff *skb, netdev_features_t features)
 {
diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index f44155840b07..116bcbf09c74 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -606,6 +606,9 @@ enum ethtool_stringset {
 	ETH_SS_PHY_STATS,
 	ETH_SS_PHY_TUNABLES,
 	ETH_SS_LINK_MODES,
+
+	/* add new constants above here */
+	ETH_SS_COUNT
 };
 
 /**
diff --git a/include/uapi/linux/ethtool_netlink.h b/include/uapi/linux/ethtool_netlink.h
new file mode 100644
index 000000000000..02f82f42a889
--- /dev/null
+++ b/include/uapi/linux/ethtool_netlink.h
@@ -0,0 +1,204 @@
+/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
+/*
+ * include/uapi/linux/ethtool_netlink.h - netlink interface for ethtool
+ *
+ * See Documentation/networking/ethtool-netlink.txt in kernel source tree for
+ * doucumentation of the interface.
+ */
+
+#ifndef _UAPI_LINUX_ETHTOOL_NETLINK_H_
+#define _UAPI_LINUX_ETHTOOL_NETLINK_H_
+
+#include <linux/ethtool.h>
+
+/* message types - userspace to kernel */
+enum {
+	ETHTOOL_MSG_USER_NONE,
+	ETHTOOL_MSG_STRSET_GET,
+	ETHTOOL_MSG_LINKINFO_GET,
+	ETHTOOL_MSG_LINKINFO_SET,
+	ETHTOOL_MSG_LINKMODES_GET,
+	ETHTOOL_MSG_LINKMODES_SET,
+	ETHTOOL_MSG_LINKSTATE_GET,
+
+	/* add new constants above here */
+	__ETHTOOL_MSG_USER_CNT,
+	ETHTOOL_MSG_USER_MAX = __ETHTOOL_MSG_USER_CNT - 1
+};
+
+/* message types - kernel to userspace */
+enum {
+	ETHTOOL_MSG_KERNEL_NONE,
+	ETHTOOL_MSG_STRSET_GET_REPLY,
+	ETHTOOL_MSG_LINKINFO_GET_REPLY,
+	ETHTOOL_MSG_LINKINFO_NTF,
+	ETHTOOL_MSG_LINKMODES_GET_REPLY,
+	ETHTOOL_MSG_LINKMODES_NTF,
+	ETHTOOL_MSG_LINKSTATE_GET_REPLY,
+
+	/* add new constants above here */
+	__ETHTOOL_MSG_KERNEL_CNT,
+	ETHTOOL_MSG_KERNEL_MAX = __ETHTOOL_MSG_KERNEL_CNT - 1
+};
+
+/* request header */
+
+/* use compact bitsets in reply */
+#define ETHTOOL_FLAG_COMPACT_BITSETS	(1 << 0)
+/* provide optional reply for SET or ACT requests */
+#define ETHTOOL_FLAG_OMIT_REPLY	(1 << 1)
+
+#define ETHTOOL_FLAG_ALL (ETHTOOL_FLAG_COMPACT_BITSETS | \
+			  ETHTOOL_FLAG_OMIT_REPLY)
+
+enum {
+	ETHTOOL_A_HEADER_UNSPEC,
+	ETHTOOL_A_HEADER_DEV_INDEX,		/* u32 */
+	ETHTOOL_A_HEADER_DEV_NAME,		/* string */
+	ETHTOOL_A_HEADER_FLAGS,			/* u32 - ETHTOOL_FLAG_* */
+
+	/* add new constants above here */
+	__ETHTOOL_A_HEADER_CNT,
+	ETHTOOL_A_HEADER_MAX = __ETHTOOL_A_HEADER_CNT - 1
+};
+
+/* bit sets */
+
+enum {
+	ETHTOOL_A_BITSET_BIT_UNSPEC,
+	ETHTOOL_A_BITSET_BIT_INDEX,		/* u32 */
+	ETHTOOL_A_BITSET_BIT_NAME,		/* string */
+	ETHTOOL_A_BITSET_BIT_VALUE,		/* flag */
+
+	/* add new constants above here */
+	__ETHTOOL_A_BITSET_BIT_CNT,
+	ETHTOOL_A_BITSET_BIT_MAX = __ETHTOOL_A_BITSET_BIT_CNT - 1
+};
+
+enum {
+	ETHTOOL_A_BITSET_BITS_UNSPEC,
+	ETHTOOL_A_BITSET_BITS_BIT,		/* nest - _A_BITSET_BIT_* */
+
+	/* add new constants above here */
+	__ETHTOOL_A_BITSET_BITS_CNT,
+	ETHTOOL_A_BITSET_BITS_MAX = __ETHTOOL_A_BITSET_BITS_CNT -