testing: selftests: net: forwarding: add devlink-required functionali…

…ty to test (hard) dropped stats field

Add devlink_trap_drop_packets_get function, as well as test that are
used to verify devlink (hard) dropped stats functionality works.

Signed-off-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/forwarding/devlink_lib.sh

@@ -324,6 +324,14 @@ devlink_trap_rx_bytes_get()
 		| jq '.[][][]["stats"]["rx"]["bytes"]'
 }
 
+devlink_trap_drop_packets_get()
+{
+	local trap_name=$1; shift
+
+	devlink -js trap show $DEVLINK_DEV trap $trap_name \
+		| jq '.[][][]["stats"]["rx"]["dropped"]'
+}
+
 devlink_trap_stats_idle_test()
 {
 	local trap_name=$1; shift
@@ -345,6 +353,24 @@ devlink_trap_stats_idle_test()
 	fi
 }
 
+devlink_trap_drop_stats_idle_test()
+{
+	local trap_name=$1; shift
+	local t0_packets t0_bytes
+
+	t0_packets=$(devlink_trap_drop_packets_get $trap_name)
+
+	sleep 1
+
+	t1_packets=$(devlink_trap_drop_packets_get $trap_name)
+
+	if [[ $t0_packets -eq $t1_packets ]]; then
+		return 0
+	else
+		return 1
+	fi
+}
+
 devlink_traps_enable_all()
 {
 	local trap_name