Fix possible out of range slice access in DrayTek client

The bitloading and SNR data slices are initially sized to match the
current DSL mode. However, the device may report additional zero values
at the end (for example for VDSL2 profile 30a). Ignore those to avoid
out of range writes to the data slices.

draytek/bins.go

@@ -95,15 +95,20 @@ func readShowbinsBin(binsBits *models.BinsBits, snrData []float64, maxSNRIndex,
 		snr, _ := strconv.ParseFloat(data[1], 64)
 		bits, _ := strconv.ParseInt(data[3], 10, 64)
 
-		if bits != 0 {
-			binsBits.Data[num] = int8(bits)
-			*maxBitsIndex = num
+		if num < len(binsBits.Data) {
+			if bits != 0 {
+				binsBits.Data[num] = int8(bits)
+				*maxBitsIndex = num
+			}
 		}
-		if snr != 0 && snr != -32 {
-			snrData[num] = snr
-			*maxSNRIndex = num
-		} else {
-			snrData[num] = -32.5
+
+		if num < len(snrData) {
+			if snr != 0 && snr != -32 {
+				snrData[num] = snr
+				*maxSNRIndex = num
+			} else {
+				snrData[num] = -32.5
+			}
 		}
 	}
 }