HelenOS sources

TX_BUF_SIZE       240 uspace/drv/nic/virtio-net/virtio-net.c 	rc = virtio_setup_dma_bufs(TX_BUFFERS, TX_BUF_SIZE, true,
TX_BUF_SIZE       332 uspace/drv/nic/virtio-net/virtio-net.c 	if (size > sizeof(virtio_net) + TX_BUF_SIZE) {
HelenOS homepage, sources at GitHub