Hi there, Right now, I am trying to do such a thing. If a computer has multiple interface A and B, assume the packet is from device A. At ip layer, before the packet is transmitted to transport layer, I change the source address and destination address of the IP header and transmit to transport layer to pretend that this packet is from device B. Not sure whether this can work or not. There are other interface specific information in the skb structure like the net_device member. If I pass the packet to transport layer only with my proposed modification, will the application's socket detect this? I didn't look into the socket match code, not sure if the socket match will check other information in skb struct beside the ip address and port number. Thanks for your help. Bill