DMA_CFG_DESC_TX_0_L4_LENGTH_MSK
d->dma.d0 |= (tcp_hdr_len & DMA_CFG_DESC_TX_0_L4_LENGTH_MSK);
(tcp_hdrlen(skb) & DMA_CFG_DESC_TX_0_L4_LENGTH_MSK);
(sizeof(struct udphdr) & DMA_CFG_DESC_TX_0_L4_LENGTH_MSK);
d->dma.l4_hdr_len |= tcp_hdr_len & DMA_CFG_DESC_TX_0_L4_LENGTH_MSK;