selftests: forwarding: ETS: Use Qdisc counters

Currently the SW-datapath ETS selftests use "ip link" stats to obtain the
number of packets that went through a given band. mlxsw then uses ethtool
per-priority counters.

Instead, change both to use qdiscs. In SW datapath this is the obvious
choice, and now that mlxsw offloads FIFO, this should work on the offloaded
datapath as well. This has the effect of verifying that the FIFO offload
works.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/drivers/net/mlxsw/sch_ets.sh

@@ -56,11 +56,19 @@ switch_destroy()
 }
 
 # Callback from sch_ets_tests.sh
-get_stats()
+collect_stats()
 {
-	local band=$1; shift
+	local -a streams=("$@")
+	local stream
 
-	ethtool_stats_get "$h2" rx_octets_prio_$band
+	# Wait for qdisc counter update so that we don't get it mid-way through.
+	busywait_for_counter 1000 +1 \
+		qdisc_parent_stats_get $swp2 10:$((${streams[0]} + 1)) .bytes \
+		> /dev/null
+
+	for stream in ${streams[@]}; do
+		qdisc_parent_stats_get $swp2 10:$((stream + 1)) .bytes
+	done
 }
 
 bail_on_lldpad