Improve iperf3 error handling in runtest.sh by capturing stderr and logging detailed error messages

runtest.sh

@@ -110,23 +110,25 @@ while [ "$COUNTER" -lt "$NUM_TESTS" ]; do
     packet_loss=$(ping -c $PING_COUNT -q $PING_TARGET | grep -oP '\d+(?=% packet loss)')
     jitter=$(ping -c $PING_COUNT $PING_TARGET | grep "time=" | awk '{print $(NF-1)}' | sed 's/time=//g' | awk '{sum+=$1; sumsq+=$1*$1} END {if (NR>1) print sqrt(sumsq/NR - (sum/NR)**2); else print 0}')
 
-    # iperf3 function
     run_iperf() {
       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
-
+    
+      local tmp_err
+      tmp_err=$(mktemp)
+    
       local result
-      result=$(iperf3 "${args[@]}" 2>/dev/null | jq -r '
+      result=$(iperf3 "${args[@]}" 2>"$tmp_err" | jq -r '
         if .error then
           "iperf3-error"
         elif has("end") | not then
@@ -138,15 +140,19 @@ while [ "$COUNTER" -lt "$NUM_TESTS" ]; do
         else
           "unexpected-format"
         end' || echo "execution-failed")
-
+    
       if [[ "$result" == "iperf3-error" || "$result" == "no-end" || "$result" == "unexpected-format" || "$result" == "execution-failed" ]]; then
         echo "$(date -Iseconds),iperf $mode $direction to $target failed with '$result'" >> "$FAILURE_LOG"
-        echo "0"  # Fallback value for CSV
+        echo "[stderr] $(cat "$tmp_err")" >> "$FAILURE_LOG"
+        echo "0"
       else
         echo "$result"
       fi
+    
+      rm -f "$tmp_err"
     }
 
+
     echo "    Running iperf3 tests..."
 
     # Run them all. These are in bits per second, convert as needed later.