原创 DE2开发板：NiosII+LWIP环境下DM9000A的驱动程序分析（web_server.c）

  /** IP address configuration in network byte order */
  struct ip_addr ip_addr;
  struct ip_addr netmask;
  struct ip_addr gw;

  err_t (* input)(struct pbuf *p, struct netif *inp);
  err_t (* output)(struct netif *netif, struct pbuf *p, struct ip_addr *ipaddr);
  err_t (* linkoutput)(struct netif *netif, struct pbuf *p);
  void *state;
#if LWIP_DHCP
  /** the DHCP client state information for this netif */
  struct dhcp *dhcp;
#endif
  /** number of bytes used in hwaddr */
  unsigned char hwaddr_len;
  /** link level hardware address of this interface */
  unsigned char hwaddr[NETIF_MAX_HWADDR_LEN];
  /** maximum transfer unit (in bytes) */
  u16_t mtu;
  /** flags (see NETIF_FLAG_ above) */
  u8_t flags;
  /** link type */
  u8_t link_type;
  /** descriptive abbreviation */
  char name[2];
  /** number of this interface */
  u8_t num;
};

typedef struct 
{
  alt_llist     llist;     /* for internal use */
  alt_lwip_dev  dev;
}alt_lwip_dev_list;
typedef struct alt_llist_s alt_llist;

struct alt_llist_s {
  alt_llist* next;     /* Pointer to the next element in the list. */
  alt_llist* previous; /* Pointer to the previous element in the list. */
};