Change order of complement & filtering

doc/plan.org

@@ -5245,6 +5245,16 @@ likely this is the cause for the main error:
 
 **** go through all steps again and try to understand why it (silently) fails later
 *** 2019-07-13: fix overflow error
+*** 2019-07-15: fix off-by-one-sometimes
+    - scapy shift code / return does not work
+**** scapy code results
+Using     meta.v6sum = (bit<16>) ((((tmp>>8) & 0xff)|tmp<<8) & 0xffff)
+;
+
+we get on the wire:
+
+sum 0x324a (incorrect -> 0x5429),
+
 ** The NetPFGA saga
 Problems encountered:
 - The logfile for a compile run is 10k+ lines