I only have one adaptor in the PC. So everything must go through that network card.
If you have single ethernet interface then it does not mean that you have the only adapter seen by WinpkFilter, because you always have the dial-up(NDISWANIP) interface.
If i put the adaptor in to tunnel mode and dont have SendPacketToAdapter or SendPacketToMSTCP then all packets should be dropped and no networking should function.
You are right, if you filter in tunnel mode and don’t reinject packets to stack then any network activity is disabled. I suppose something is wrong with your code, definitions or the network interface you filter.