BlackFin UDP packet transmission

Hello.
I have BF537 based board wtih external ethernet tranciever. I setup
phy and now i want to transmit UDP packet with payload data acuired
from ADC. I don't want to use ADI driver model or lwIP. In my opinion
i want to init descriptor based DMA chain with only UDP data field
changing. Give me please info about what is UDP packet data structure
i need to transmit. Need i calculate some control sums for evey packet
or not? What is source MAC address field to be if i not know it?
Thanks,
Pavel Schukin.