[RFC PATCH net-next v3 00/21] ethtool netlink interface, part 1

From: Michal Kubecek
Date: Mon Feb 18 2019 - 13:21:31 EST

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

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

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
- 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

- 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