netdevsim: Support for L3 HW stats

"L3 stats" is a suite of interface statistics aimed at reflecting traffic taking place in a HW device, on an object corresponding to some software netdevice. Support for this stats suite has been added recently, in commit ca0a53dcec94 ("Merge branch 'net-hw-counters-for-soft-devices'").

In this patch set:

- Patch #1 adds support for L3 stats to netdevsim.

Real devices can have various conditions for when an L3 counter is available. To simulate this, netdevsim maintains a list of devices suitable for HW stats collection. Only when l3_stats is enabled on both a netdevice itself, and in netdevsim, will netdevsim contribute values to L3 stats.

This enablement and disablement is done via debugfs:

    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/enable_ifindex
    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/disable_ifindex

Besides this, there is a third toggle to mark a device for future failure:

    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/fail_next_enable

- This allows HW-independent testing of stats reporting and in-kernel APIs, as well as a test for enablement rollback, which is difficult to do otherwise. This netdevsim-specific selftest is added in patch #2.

- Patch #3 adds another driver-specific selftest, namely a test aimed at checking mlxsw-induced stats monitoring events.

v3:
- Patch #1:
- Rewrite the fops definitions as macros. clang didn't like the previous approach to reducing redundancy.

v2:
- Patch #1:
- Embed fops into a structure that carries the necessary metadata together with the fops. Extract the data in the generic write handler to determine what debugfs file the op pertains to. This obviates the need to have a per-debugfs file helper wrapper.

Petr Machata (3):
netdevsim: Introduce support for L3 offload xstats
selftests: netdevsim: hw_stats_l3: Add a new test
selftests: mlxsw: hw_stats_l3: Add a new test

 drivers/net/netdevsim/Makefile                |   2 +-
 drivers/net/netdevsim/dev.c                   |  17 +-
 drivers/net/netdevsim/hwstats.c               | 486 ++++++++++++++++++
 drivers/net/netdevsim/netdevsim.h             |  23 +
 .../drivers/net/mlxsw/hw_stats_l3.sh          |  31 ++
 .../drivers/net/netdevsim/hw_stats_l3.sh      | 421 +++++++++++++++
 tools/testing/selftests/net/forwarding/lib.sh |  60 +++
 7 files changed, 1037 insertions(+), 3 deletions(-)
 create mode 100644 drivers/net/netdevsim/hwstats.c
 create mode 100755 tools/testing/selftests/drivers/net/mlxsw/hw_stats_l3.sh
 create mode 100755 tools/testing/selftests/drivers/net/netdevsim/hw_stats_l3.sh

2.31.1