Change order of complement & filtering

bin/checksum_delta_diff_test.py

@@ -13,16 +13,20 @@ def checksum_scapy(pkt):
     if len(pkt) % 2 == 1:
         pkt += b"\0"
 
+    # P4: ABOVE not needed (always even)
+
     # array: create an array of 16 bit values from the input
     # and then sum it up -> this might be sligthly/much higher
     # than 16 bit (additions!)
     s = sum(array.array("H", pkt))
+    # P4: summing manually into 32bit
 
     # add the (right shift 16) and the 16 right bits
     # basically: assuming 32 bit (?): add the two 16 bit "words"
     # together
     # This might still exceed 16 bit!
     s = (s >> 16) + (s & 0xffff)
+    # P4:
 
     # right shift 16 -> zero least significant bits,
     # and add the upper bits to it