selftests: forwarding: lib: Allow reading TC rule byte counters

The function tc_rule_stats_get() fetches a packet counter of a given TC
rule. Extend it to support byte counters as well by adding an optional
argument with selector.
Signed-off-by: NPetr Machata <petrm@mellanox.com>
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -593,9 +593,10 @@ tc_rule_stats_get()
 	local dev=$1; shift
 	local pref=$1; shift
 	local dir=$1; shift
+	local selector=${1:-.packets}; shift
 
 	tc -j -s filter show dev $dev ${dir:-ingress} pref $pref \
-	    | jq '.[1].options.actions[].stats.packets'
+	    | jq ".[1].options.actions[].stats$selector"
 }
 
 ethtool_stats_get()