}
ethernetif_init
在初始化协议栈时，netif_add(mLocalNetif,&ipaddr, &netmask, &gw, NULL, ethernetif_init, tcpip_input)。
ethernetif_init做的工作：
（1） 初始化struct ethernetif
（2） 初始化struct net_if
（3） 调用硬件初始化low_level_init(netif);
/** * Should be called at the beginning of the program to set up the * network interface. It calls the function low_level_init() to do the * actual setup of the hardware. * * This function should be passed as a parameter to netif_add(). * * @param netif the lwip network interface structure for this ethernetif * @return ERR_OK if the loopif is initialized * ERR_MEM if private data couldn't be allocated * any other err_t on error */ err_t ethernetif_init(struct netif *netif) { struct ethernetif *ethernetif; LWIP_ASSERT(\ ethernetif = mem_malloc(sizeof(struct ethernetif)); if (ethernetif == NULL) { LWIP_DEBUGF(NETIF_DEBUG, (\ return ERR_MEM; } #if LWIP_NETIF_HOSTNAME /* Initialize interface hostname */ netif->hostname = \#endif /* LWIP_NETIF_HOSTNAME */ /* * Initialize the snmp variables and counters inside the struct netif. * The last argument should be replaced with your link speed, in units * of bits per second. */ NETIF_INIT_SNMP(netif, snmp_ifType_ethernet_csmacd, LINK_SPEED_OF_YOUR_NETIF_IN_BPS); netif->state = ethernetif; netif->name[0] = IFNAME0; netif->name[1] = IFNAME1; /* We directly use etharp_output() here to save a function call. * You can instead declare your own function an call etharp_output() * from it if you have to do some checks before sending (e.g. if link * is available...) */ netif->output = etharp_output; netif->linkoutput = low_level_output; ethernetif->ethaddr = (struct eth_addr *)&(netif->hwaddr[0]); /* initialize the hardware */ low_level_init(netif); return ERR_OK; }
low_level_init
它是网卡硬件初始化的代码。它被ethernetif_init调用。
/** * In this function, the hardware should be initialized. * Called from ethernetif_init(). * * @param netif the already initialized lwip network interface structure * for this ethernetif */ static void low_level_init(struct netif *netif) { struct ethernetif *ethernetif = netif->state; /* set MAC hardware address length */ netif->hwaddr_len = ETHARP_HWADDR_LEN; /* set MAC hardware address */ netif->hwaddr[0] = 0x00; netif->hwaddr[1] = 0x50; netif->hwaddr[2] = 0x50; netif->hwaddr[3] = 0x50; netif->hwaddr[4] = 0x50; netif->hwaddr[5] = 0x01; /* maximum transfer unit */ netif->mtu = 1500; /* device capabilities */ /* don't set NETIF_FLAG_ETHARP if this device is not an ethernet one */ netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_LINK_UP; /* Do whatever else is needed to initialize interface. */ }
low_level_output
它是实现网卡发送数据的函数。
它发送链表structpbuf中的所有数据。
在代码：
netif->linkoutput = low_level_output;
中，low_level_output被赋于netif->linkoutput。
/** * This function should do the actual transmission of the packet. The packet is * contained in the pbuf that is passed to the function. This pbuf * might be chained. * * @param netif the lwip network interface structure for this ethernetif * @param p the MAC packet to send (e.g. IP packet including MAC addresses and type) * @return ERR_OK if the packet could be sent * an err_t value if the packet couldn't be sent * * @note Returning ERR_MEM here if a DMA queue of your MAC is full can lead to * strange results. You might consider waiting for space in the DMA queue * to become availale since the stack doesn't retry to send a packet * dropped because of memory failure (except for the TCP timers). */ static err_t low_level_output(struct netif *netif, struct pbuf *p) { struct ethernetif *ethernetif = netif->state; struct pbuf *q; initiate transfer(); #if ETH_PAD_SIZE pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */ #endif for(q = p; q != NULL; q = q->next) { /* Send the data from the pbuf to the interface, one pbuf at a time. The size of the data in each pbuf is kept in the ->len variable. */ send data from(q->payload, q->len); } signal that packet should be sent(); #if ETH_PAD_SIZE pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */ #endif LINK_STATS_INC(link.xmit);