[U-Boot] How to random my mac in u-boot

[Peter Pan]

Recently, we had a issue that we need to start more than one board at
a time. The problem
we are facing is that every board is using the same u-boot, which
makes them all have the
same mac address.

Firstly, I think I can gives out a random MAC as we need, but I can
not find any rand() or srand()
function in U-Boot.

My U-Boot version is 2009.11 and my board is based on MPC8247.

Is there a chance that I can do this random job when U-Boot starts?