Hello,
I'm trying to determine if a certain application is feasible on the AM335x, and I'm running into some confusion regarding how the AM335x handles MAC addresses. In simple terms, I'd like to be able to trick the AM335x into thinking it has another MAC address, but I don't think this is possible for the following reasons:
1. The MAC address for the AM335x is stored in an internal register and is read-only
2. The CPSW does not support promiscuous mode
As far as I can tell, these two facts make the application more or less impossible. I couldn't find anything in the TRM related to spoofing the MAC address of transmitted frames, so my assumption is that the CPSW peripheral reads the internal MAC address register, and this behaviour can't be changed. Most computer NICs have hard-coded MAC addresses with provisions to ignore them using software, so I'm just wondering if similar functionality exists on the AM335x
Even if I could spoof the MAC of outgoing frames, the inability of the CPSW to enter promiscuous mode would make it irrelevant unless incoming frames could also be filtered using a spoofed address. If my outgoing frames have a certain MAC address, their reply will come back to the same MAC address. If the receiving side is similar to the transmitting side (MAC address can only be determined from the register and not spoofed) then the frames will get filtered since the MAC addresses don't match. If you could put the CPSW in promiscuous mode you could get around this (check all incoming frames against spoofed MAC address in software) but I don't see it being possible currently.
Based on what I've found, I'm pretty confident that what I'd like to do is not possible, but I'm just wondering if anyone with some experience in the area could provide confirmation on my findings.
Thanks,
