selftests: add a test for ethtool pause stats

Make sure the empty nest is reported even without stats.
Make sure reporting only selected stats works fine.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/drivers/net/netdevsim/ethtool-pause.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+NSIM_ID=$((RANDOM % 1024))
+NSIM_DEV_SYS=/sys/bus/netdevsim/devices/netdevsim$NSIM_ID
+NSIM_DEV_DFS=/sys/kernel/debug/netdevsim/netdevsim$NSIM_ID
+NSIM_NETDEV=
+num_passes=0
+num_errors=0
+
+function cleanup_nsim {
+    if [ -e $NSIM_DEV_SYS ]; then
+	echo $NSIM_ID > /sys/bus/netdevsim/del_device
+    fi
+}
+
+function cleanup {
+    cleanup_nsim
+}
+
+trap cleanup EXIT
+
+function get_netdev_name {
+    local -n old=$1
+
+    new=$(ls /sys/class/net)
+
+    for netdev in $new; do
+	for check in $old; do
+            [ $netdev == $check ] && break
+	done
+
+	if [ $netdev != $check ]; then
+	    echo $netdev
+	    break
+	fi
+    done
+}
+
+function check {
+    local code=$1
+    local str=$2
+    local exp_str=$3
+
+    if [ $code -ne 0 ]; then
+	((num_errors++))
+	return
+    fi
+
+    if [ "$str" != "$exp_str"  ]; then
+	echo -e "Expected: '$exp_str', got '$str'"
+	((num_errors++))
+	return
+    fi
+
+    ((num_passes++))
+}
+
+# Bail if ethtool is too old
+if ! ethtool -h | grep include-stat 2>&1 >/dev/null; then
+    echo "SKIP: No --include-statistics support in ethtool"
+    exit 4
+fi
+
+# Make a netdevsim
+old_netdevs=$(ls /sys/class/net)
+
+modprobe netdevsim
+echo $NSIM_ID > /sys/bus/netdevsim/new_device
+
+NSIM_NETDEV=`get_netdev_name old_netdevs`
+
+set -o pipefail
+
+echo n > $NSIM_DEV_DFS/ethtool/pause/report_stats_tx
+echo n > $NSIM_DEV_DFS/ethtool/pause/report_stats_rx
+
+s=$(ethtool --json -a $NSIM_NETDEV | jq '.[].statistics')
+check $? "$s" "null"
+
+s=$(ethtool -I --json -a $NSIM_NETDEV | jq '.[].statistics')
+check $? "$s" "{}"
+
+echo y > $NSIM_DEV_DFS/ethtool/pause/report_stats_tx
+
+s=$(ethtool -I --json -a $NSIM_NETDEV | jq '.[].statistics | length')
+check $? "$s" "1"
+
+s=$(ethtool -I --json -a $NSIM_NETDEV | jq '.[].statistics.tx_pause_frames')
+check $? "$s" "2"
+
+echo y > $NSIM_DEV_DFS/ethtool/pause/report_stats_rx
+
+s=$(ethtool -I --json -a $NSIM_NETDEV | jq '.[].statistics | length')
+check $? "$s" "2"
+
+s=$(ethtool -I --json -a $NSIM_NETDEV | jq '.[].statistics.rx_pause_frames')
+check $? "$s" "1"
+s=$(ethtool -I --json -a $NSIM_NETDEV | jq '.[].statistics.tx_pause_frames')
+check $? "$s" "2"
+
+if [ $num_errors -eq 0 ]; then
+    echo "PASSED all $((num_passes)) checks"
+    exit 0
+else
+    echo "FAILED $num_errors/$((num_errors+num_passes)) checks"
+    exit 1
+fi