Now Npcap can have a send-to-Rx adapter. The send-to-Rx adapter will inject all its packets to "Receive Path" (Rx) instead of normal "Send Path" (Tx). So that instead of sending traffic to the network, the adapter will pretend to receive the injected traffic from the network in this way.
Currently only one send-to-Rx adapter is supported by specifying SendToRx value in Npcap driver service's registry key (need to restart the driver to take effect).
Npcap driver service's registry key is usually in: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\npf. In this key. You need to manually create a REG_SZ value named SendToRx, the value is the name of the adapter you want to be send-to-Rx adapter. The name is usually like format of \Device\{F5A00000-E19A-4D17-B6D9-A23FE1852573}. You can query this value using Nmap's nmap --iflist command, you will get a similar value like \Device\NPF_{F5A00000-E19A-4D17-B6D9-A23FE1852573}, but they are NOT THE SAME. You need to remove the NPF_ in this string and copy it to registry's SendToRx value. Then reboot the driver by net stop npf and net start npf.