RBD_SIZE
next = addr + RFD_SIZE + RBD_SIZE + ETH_FRAME_LEN + 10;
next2 = next + RFD_SIZE + RBD_SIZE + ETH_FRAME_LEN + 10;
init_rbd.rbd_bufl = addr + RFD_SIZE + RBD_SIZE;
ether1_writebuffer (dev, &init_rbd, addr + RFD_SIZE, RBD_SIZE);
ether1_readbuffer (dev, &rbd, rbdaddr, RBD_SIZE);