Refactor iperf3 function in runtest.sh for improved argument handling and readability

runtest.sh

@@ -109,23 +109,27 @@ while [ "$COUNTER" -lt "$NUM_TESTS" ]; do
 
     # iperf3 function
     run_iperf() {
-      local target=$1
-      local mode=$2  # tcp or udp
-      local direction=$3  # up or down
-
-      local args="-c $target -J -t $IPERF_DURATION"
-      [ "$mode" = "udp" ] && args="$args -u -b 10M"
-
-      [ "$direction" = "down" ] && args="$args -R"
-
-      iperf3 $args 2>/dev/null | jq -r '
+      local target="$1"
+      local mode="$2"
+      local direction="$3"
+      local args=("-c" "$target" "-J" "-t" "10")
+    
+      if [ "$mode" = "udp" ]; then
+        args+=("-u")
+      fi
+    
+      if [ "$direction" = "down" ]; then
+        args+=("--reverse")
+      fi
+    
+      iperf3 "${args[@]}" 2>/dev/null | jq -r '
         if .error then "0" else
           if .end then
             if .end.sum_received then .end.sum_received.bits_per_second
             elif .end.sum then .end.sum.bits_per_second
             else "0" end
           else "0" end
-        end'
+        end' || echo "0"
     }
 
     echo "    Running iperf3 tests..."