It seems that the implementation (at code level) does not match with the 
actual behaviour. I would like to seek expertise on clarifying my 
understanding in UDP implementation so that this phenomenon can be 
explained.

How about you just add some printks or use a tool like systemtap to instrument
the code path?  That should give some insights what is actually going on.

-Andi


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VGER BF report: U 0.473534