selftests: drivers: hw: add test for the ethtool standard counters

selftests: drivers: hw: add test for the ethtool standard counters

Add a new selftest - ethtool_std_stats.sh - which validates the
eth-ctrl, eth-mac and pause standard statistics exported by an
interface. Collision related eth-mac counters as well as the error ones
will be checked against zero since that is the most likely correct
scenario.

The central part of this patch is the traffic_test() function which
gathers the 'before' counter values, sends a batch of traffic and then
interrogates again the same counters in order to determine if the delta
is on target. The function receives an array through which the caller
can request what counters to be interrogated and, for each of them, what
is their target delta value.

The output from this selftest looks as follows on a LX2160ARDB board:

 $ ./run_kselftest.sh -t drivers/net/hw:ethtool_std_stats.sh
 TAP version 13
 1..1
 # timeout set to 0
 # selftests: drivers/net/hw: ethtool_std_stats.sh
 # TAP version 13
 # 1..26
 # ok 1 ethtool_std_stats.eth-ctrl-MACControlFramesTransmitted
 # ok 2 ethtool_std_stats.eth-ctrl-MACControlFramesReceived
 # ok 3 ethtool_std_stats.eth-mac-FrameCheckSequenceErrors
 # ok 4 ethtool_std_stats.eth-mac-AlignmentErrors
 # ok 5 ethtool_std_stats.eth-mac-FramesLostDueToIntMACXmitError
 # ok 6 ethtool_std_stats.eth-mac-CarrierSenseErrors # SKIP
 # ok 7 ethtool_std_stats.eth-mac-FramesLostDueToIntMACRcvError
 # ok 8 ethtool_std_stats.eth-mac-InRangeLengthErrors # SKIP
 # ok 9 ethtool_std_stats.eth-mac-OutOfRangeLengthField # SKIP
 # ok 10 ethtool_std_stats.eth-mac-FrameTooLongErrors # SKIP
 # ok 11 ethtool_std_stats.eth-mac-FramesAbortedDueToXSColls # SKIP
 # ok 12 ethtool_std_stats.eth-mac-SingleCollisionFrames # SKIP
 # ok 13 ethtool_std_stats.eth-mac-MultipleCollisionFrames # SKIP
 # ok 14 ethtool_std_stats.eth-mac-FramesWithDeferredXmissions # SKIP
 # ok 15 ethtool_std_stats.eth-mac-LateCollisions # SKIP
 # ok 16 ethtool_std_stats.eth-mac-FramesWithExcessiveDeferral # SKIP
 # ok 17 ethtool_std_stats.eth-mac-BroadcastFramesXmittedOK
 # ok 18 ethtool_std_stats.eth-mac-OctetsTransmittedOK
 # ok 19 ethtool_std_stats.eth-mac-BroadcastFramesReceivedOK
 # ok 20 ethtool_std_stats.eth-mac-OctetsReceivedOK
 # ok 21 ethtool_std_stats.eth-mac-FramesTransmittedOK
 # ok 22 ethtool_std_stats.eth-mac-MulticastFramesXmittedOK
 # ok 23 ethtool_std_stats.eth-mac-FramesReceivedOK
 # ok 24 ethtool_std_stats.eth-mac-MulticastFramesReceivedOK
 # ok 25 ethtool_std_stats.pause-tx_pause_frames
 # ok 26 ethtool_std_stats.pause-rx_pause_frames
 # # 10 skipped test(s) detected.  Consider enabling relevant config options to improve coverage.
 # # Totals: pass:16 fail:0 xfail:0 xpass:0 skip:10 error:0
 ok 1 selftests: drivers/net/hw: ethtool_std_stats.sh

Please note that not all MACs are counting the software injected pause
frames as real Tx pause. For example, on a LS1028ARDB the selftest
output will reflect the fact that neither the ENETC MAC, nor the Felix
switch MAC are able to detect Tx pause frames injected by software.

 $ ./run_kselftest.sh -t drivers/net/hw:ethtool_std_stats.sh
 (...)
 # # software sent pause frames not detected
 # ok 25 ethtool_std_stats.pause-tx_pause_frames # XFAIL
 # ok 26 ethtool_std_stats.pause-rx_pause_frames

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20260330152933.2195885-10-ioana.ciornei@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>