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Ethernet hardware loopback

I am working on a hardware implementation using a PHY chip that allows far-end loopback, that is, data from the host that is sent to this chip is echoed back exactly as received. I wanted to create some software that would use this loopback to test the hardware out, but the echoed data has the source and destination addresses set to the same values as when they went out from the computer.

Is it possible to automatically differentiate the transmitted frames from the received frames, since they have the same source and destination addresses? Wireshark sees both the transmitted and the received packets, and I don't see any indication as to which is which in the display. Obviously (?), the earlier one should be the transmitted frame, but I don't know of any way to tell programatically.

Is there a way to tell the transmitted from the received and filter out the transmitted frame?