RX_BUFFER_MULTIPLE
if (bp->rx_buffer_size % RX_BUFFER_MULTIPLE) {
RX_BUFFER_MULTIPLE);
roundup(bp->rx_buffer_size, RX_BUFFER_MULTIPLE);
buffer_size = bp->rx_buffer_size / RX_BUFFER_MULTIPLE;
#define RX_BUFFER_MAX (0xFF * RX_BUFFER_MULTIPLE) /* 16320 bytes */