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- UID
- 1029342
- 性别
- 男
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在lwIP中，是通过结构体netif来描述一个硬件网络接口的，在单网卡中，这个结构体只有一个，多网卡中可有何网卡数目相同的netif结构体，它们构成一个数据链。下面的代码选自netif.h，是netif结构体的代码描述：[cpp] view plaincopyprint?
- /** Generic data structure used for all lwIP network interfaces.
- * The following fields should be filled in by the initialization
- * function for the device driver: hwaddr_len, hwaddr[], mtu, flags
- * 用于所有lwIP网络接口的通用数据结构体
- * 设备驱动函数在初始化时应该填充以下数据域:hwaddr_len,hwaddr[],mtu,flags.*/
- struct netif {
- /** pointer to next in linked list */
- struct netif *next;
- /** IP address configuration in network byte order */
- struct ip_addr ip_addr; //IP地址
- struct ip_addr netmask; //子网掩码
- struct ip_addr gw; //默认网关
- /** This function is called by the network device driver
- * to pass a packet up the TCP/IP stack.
- 这个函数由网络设备驱动所调用，从网卡中接收数据包并传递给TCP/IP协议栈*/
- err_t (* input)(struct pbuf *p, struct netif *inp); //从网卡中接收一包数据
- /** This function is called by the IP module when it wants
- * to send a packet on the interface. This function typically
- * first resolves the hardware address, then sends the packet.
- 当IP模块向接口发送一个数据包时调用此函数。这个函数通常首先解析
- 硬件地址，然后发送数据包*/
- err_t (* output)(struct netif *netif, struct pbuf *p, //IP层调用此函数向网卡发送一包数据
- struct ip_addr *ipaddr);
- /** This function is called by the ARP module when it wants
- * to send a packet on the interface. This function outputs
- * the pbuf as-is on the link medium.
- 当ARP模块向接口发送一个数据包时调用此函数。这个函数向链路输出一个pbuf。*/
- err_t (* linkoutput)(struct netif *netif, struct pbuf *p); //ARP模块调用这个函数向网卡发送一包数据
- #if LWIP_NETIF_STATUS_CALLBACK //netif状态被改变时该函数被调用,未使用
- /** This function is called when the netif state is set to up or down
- */
- void (* status_callback)(struct netif *netif);
- #endif /* LWIP_NETIF_STATUS_CALLBACK */
- #if LWIP_NETIF_LINK_CALLBACK //未使用
- /** This function is called when the netif link is set to up or down
- netif连接改变时调用
- */
- void (* link_callback)(struct netif *netif);
- #endif /* LWIP_NETIF_LINK_CALLBACK */
- /** This field can be set by the device driver and could point
- * to state information for the device.
- * 这个域能够通过设备驱动设置并且能够指向设备的信息状态，供用户自行使用*/
- void *state;
- #if LWIP_DHCP //使能DHCP
- /** the DHCP client state information for this netif */
- struct dhcp *dhcp;
- #endif /* LWIP_DHCP */
- #if LWIP_AUTOIP
- /** the AutoIP client state information for this netif */
- struct autoip *autoip;
- #endif
- #if LWIP_NETIF_HOSTNAME
- /* the hostname for this netif, NULL is a valid value NULL也是一个有效值*/
- char* hostname;
- #endif /* LWIP_NETIF_HOSTNAME */
- /** maximum transfer unit (in bytes) 最大发送单元(单位:字节)以太网为1500*/
- u16_t mtu;
- /** number of bytes used in hwaddr 硬件地址长度*/
- u8_t hwaddr_len;
- /** link level hardware address of this interface 接口的连接层硬件地址*/
- u8_t hwaddr[NETIF_MAX_HWADDR_LEN]; //=6
- /** flags (see NETIF_FLAG_ above) 标志位*/
- u8_t flags;
- /** descriptive abbreviation 描述缩写*/
- char name[2];
- /** number of this interface 接口号,如果两个网络接口具有相同的描述缩写(即上面的name字段),就用num字段来区分相同类型的不同网络接口*/
- u8_t num;
- #if LWIP_SNMP
- /** link type (from "snmp_ifType" enum from snmp.h) 连接类型*/
- u8_t link_type;
- /** (estimate) link speed (预计)连接速度*/
- u32_t link_speed;
- /** timestamp at last change made (up/down) 最后up/down变化时间戳*/
- u32_t ts;
- /** counters 计数器*/
- u32_t ifinoctets;
- u32_t ifinucastpkts;
- u32_t ifinnucastpkts;
- u32_t ifindiscards;
- u32_t ifoutoctets;
- u32_t ifoutucastpkts;
- u32_t ifoutnucastpkts;
- u32_t ifoutdiscards;
- #endif /* LWIP_SNMP */
- #if LWIP_IGMP
- /* This function could be called to add or delete a entry in the multicast filter table of the ethernet MAC.*/
- err_t (*igmp_mac_filter)( struct netif *netif, struct ip_addr *group, u8_t action);
- #endif /* LWIP_IGMP */
- #if LWIP_NETIF_HWADDRHINT
- u8_t *addr_hint;
- #endif /* LWIP_NETIF_HWADDRHINT */
- #if ENABLE_LOOPBACK
- /* List of packets to be queued for ourselves. */
- struct pbuf *loop_first;
- struct pbuf *loop_last;
- #if LWIP_LOOPBACK_MAX_PBUFS
- u16_t loop_cnt_current;
- #endif /* LWIP_LOOPBACK_MAX_PBUFS */
- #endif /* ENABLE_LOOPBACK */
- }; // END struct netif
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