Mon, Feb 18, 2019 at 07:21:24PM CET, mkubecek@suse.cz wrote:

Note: this is marked as RFC because it's rather late in the cycle; the plan
is to make a regular submission (with changes based on review) once
net-next reopens after the 5.1 merge window. The full (work in progress)
series, together with the (userspace) ethtool counterpart can be found at
https://github.com/mkubecek/ethnl

This is first part of alternative userspace interface for ethtool. The aim
is to address some long known issues with the ioctl interface, mainly lack
of extensibility, raciness, limited error reporting and absence of
notifications.

The interface uses generic netlink family "ethtool"; it provides multicast
group "monitor" which is used for notifications. Documentation for the
interface is in Documentation/networking/ethtool-netlink.txt

Basic concepts:

- the goal is to provide all features of ioctl interface but allow
 easier future extensions; at some point, it should be possible to have
 full ethtool functionality without using the ioctl interface

I'm not sure it is a good idea to map the existing iface to netlink
fully. There are things in ethtool which are not really unique for
Ethernet. Those things should be put somewhere else.

- inextensibility of ioctl interface resulted in way too many commands,
 many of them obsoleted by newer ones; reduce the number by  ignoring the
 obsolete commands and grouping some together
- for "set" type commands, allows passing only the attributes to be
 changed; therefore we don't need a get-modify-set cycle (which is
 inherently racy), userspace can simply say what it wants to change
- provide notifications to multicast group "monitor" like rtnetlink does,
 i.e. in the form of messages close to replies to "get" requests
- allow dump requests to get some information about all network devices
 providing it
- be less dependent on ethtool and kernel being in sync; allow e.g. saying
 "ethtool -s eth0 advertise foo off" without ethtool knowing what "foo"
 means; it's kernel's job to know what mode "xyz" is and if it exists and
 is supported

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

ToDo / open questions:

- some features provided by ethtool would rather belong to devlink (and
 some are already superseded by devlink); however, only few drivers
 provide devlink interface at the moment and as recent discussion on
 flashing revealed, we cannot rely on devlink's presence

Could you explain why please?

- while the netlink interface allows easy future extensions, ethtool_ops
 interface does not; some settings could be implemented using tunables and
 accessed via relevant netlink messages (as well as tunables) from
 userspace but in the long term, something better will be needed

- currently, all communication with drivers via ethtool_ops is done
 under RTNL as this is what ioctl interface does and likely many
 ethtool_ops handlers rely on that; if we are going to rework ethtool_ops
 in the future ("phase two"), it would be nice to get rid of it

- ethtool_ops should pass extack pointer to allow drivers more meaningful
 error reporting; it's not clear, however, how to pass information about
 offending attribute

- notifications are sent whenever a change is done via netlink API or
 ioctl API and for netdev features also whenever they are updated using
 netdev_change_features(); it would be desirable to notify also about
 link state and negotiation result (speed/duplex and partner link
 modes) but it would be more tricky

Michal Kubecek (21):
 netlink: introduce nla_put_bitfield32()
 ethtool: move to its own directory
 ethtool: introduce ethtool netlink interface
 ethtool: helper functions for netlink interface
 ethtool: netlink bitset handling
 ethtool: support for netlink notifications
 ethtool: implement EVENT notifications
 ethtool: generic handlers for GET requests
 ethtool: move string arrays into common file
 ethtool: provide string sets with GET_STRSET request
 ethtool: provide driver/device information in GET_INFO request
 ethtool: provide permanent hardware address in GET_INFO request
 ethtool: provide timestamping information in GET_INFO request
 ethtool: provide link mode names as a string set
 ethtool: provide link settings and link modes in GET_SETTINGS request
 ethtool: provide WoL information in GET_SETTINGS request
 ethtool: provide message level in GET_SETTINGS request
 ethtool: provide link state in GET_SETTINGS request
 ethtool: provide device features in GET_SETTINGS request
 ethtool: provide private flags in GET_SETTINGS request
 ethtool: send netlink notifications about setting changes

Documentation/networking/ethtool-netlink.txt | 441 +++++++++++++
include/linux/ethtool_netlink.h              |  17 +
include/linux/netdevice.h                    |  14 +
include/net/netlink.h                        |  15 +
include/uapi/linux/ethtool.h                 |  10 +
include/uapi/linux/ethtool_netlink.h         | 265 ++++++++
include/uapi/linux/net_tstamp.h              |  13 +
net/Kconfig                                  |   8 +
net/Makefile                                 |   2 +-
net/core/Makefile                            |   2 +-
net/ethtool/Makefile                         |   7 +
net/ethtool/bitset.c                         | 572 +++++++++++++++++
net/ethtool/bitset.h                         |  40 ++
net/ethtool/common.c                         | 227 +++++++
net/ethtool/common.h                         |  29 +
net/ethtool/info.c                           | 332 ++++++++++
net/{core/ethtool.c => ethtool/ioctl.c}      | 244 ++-----
net/ethtool/netlink.c                        | 634 +++++++++++++++++++
net/ethtool/netlink.h                        | 252 ++++++++
net/ethtool/settings.c                       | 559 ++++++++++++++++
net/ethtool/strset.c                         | 461 ++++++++++++++
21 files changed, 3937 insertions(+), 207 deletions(-)
create mode 100644 Documentation/networking/ethtool-netlink.txt
create mode 100644 include/linux/ethtool_netlink.h
create mode 100644 include/uapi/linux/ethtool_netlink.h
create mode 100644 net/ethtool/Makefile
create mode 100644 net/ethtool/bitset.c
create mode 100644 net/ethtool/bitset.h
create mode 100644 net/ethtool/common.c
create mode 100644 net/ethtool/common.h
create mode 100644 net/ethtool/info.c
rename net/{core/ethtool.c => ethtool/ioctl.c} (91%)
create mode 100644 net/ethtool/netlink.c
create mode 100644 net/ethtool/netlink.h
create mode 100644 net/ethtool/settings.c
create mode 100644 net/ethtool/strset.c

-- 
2.20.1