Linux获取网络接口信息

linux获取网络接口信息需要用到的函数为ioctl（），结构体struct ifreq，struct ifconf

1.ioctl（）函数原型及作用

 #include <sys/ioctl.h>

 int ioctl(int d, int request, ...);

 //参数
 //int d：是一个文件描述符
 //int request ：表示要请求的信息。如IP地址、网络掩码等
 //......:可变参数，根据request而定

下面是ioctl请求的request参数以及arg地址必须指向的数据类型：

2.struct ifreq结构体

　　这个结构定义在include/net/if.h，用来配置ip地址，激活接口，配置MTU等接口信息的

  /* Interface request structure used for socket ioctl's.  All interface
     ioctl's must have parameter definitions which begin with ifr_name.
     The remainder may be interface specific.  */

 struct ifreq
 {
 # define IFHWADDRLEN
 # define IFNAMSIZ   IF_NAMESIZE
      union
        {
      char ifrn_name[IFNAMSIZ];   /* Interface name, e.g. "en0".  */
        } ifr_ifrn;

      union
        {
      struct sockaddr ifru_addr;
      struct sockaddr ifru_dstaddr;
      struct sockaddr ifru_broadaddr;
      struct sockaddr ifru_netmask;
      struct sockaddr ifru_hwaddr;
      short int ifru_flags;
      int ifru_ivalue;
      int ifru_mtu;
      struct ifmap ifru_map;
      char ifru_slave[IFNAMSIZ];  /* Just fits the size */
      char ifru_newname[IFNAMSIZ];
      __caddr_t ifru_data;
        } ifr_ifru;
    };
  # define ifr_name   ifr_ifrn.ifrn_name  /* interface name   */
  # define ifr_hwaddr ifr_ifru.ifru_hwaddr    /* MAC address      */
  # define ifr_addr   ifr_ifru.ifru_addr  /* address      */
  # define ifr_dstaddr    ifr_ifru.ifru_dstaddr   /* other end of p-p lnk */
  # define ifr_broadaddr  ifr_ifru.ifru_broadaddr /* broadcast address    */
  # define ifr_netmask    ifr_ifru.ifru_netmask   /* interface net mask   */
  # define ifr_flags  ifr_ifru.ifru_flags /* flags        */
  # define ifr_metric ifr_ifru.ifru_ivalue    /* metric       */
  # define ifr_mtu    ifr_ifru.ifru_mtu   /* mtu          */
  # define ifr_map    ifr_ifru.ifru_map   /* device map       */
  # define ifr_slave  ifr_ifru.ifru_slave /* slave device     */
  # define ifr_data   ifr_ifru.ifru_data  /* for use by interface */
  # define ifr_ifindex    ifr_ifru.ifru_ivalue    /* interface index      */
  # define ifr_bandwidth  ifr_ifru.ifru_ivalue    /* link bandwidth   */
  # define ifr_qlen   ifr_ifru.ifru_ivalue    /* queue length     */
  # define ifr_newname    ifr_ifru.ifru_newname   /* New name     */
  # define _IOT_ifreq _IOT(_IOTS(char),IFNAMSIZ,_IOTS(char),,,)
  # define _IOT_ifreq_short _IOT(_IOTS(char),IFNAMSIZ,_IOTS(short),,,)
  # define _IOT_ifreq_int _IOT(_IOTS(char),IFNAMSIZ,_IOTS(int),,,)

3.struct ifconf

　　ifreq包含在ifconf结构中。而ifconf结构通常是用来保存所有接口的信息的。

  /* Structure used in SIOCGIFCONF request.  Used to retrieve interface
     configuration for machine (useful for programs which must know all
     networks accessible).  */

  struct ifconf
    {
      int ifc_len;            /* Size of buffer.  */
      union
        {
      __caddr_t ifcu_buf;
      struct ifreq *ifcu_req;
        } ifc_ifcu;
    };
  # define ifc_buf    ifc_ifcu.ifcu_buf   /* Buffer address.  */
  # define ifc_req    ifc_ifcu.ifcu_req   /* Array of structures.  */
  # define _IOT_ifconf _IOT(_IOTS(struct ifconf),,,,,) /* not right */
  #endif  /* Misc.  */

下面程序是获取本机的IP地址

 #include <stdio.h>
 #include <sys/socket.h>
 #include <string.h>
 #include <sys/types.h>
 #include <netinet/in.h>
 #include <sys/ioctl.h>
 #include <net/if.h>
 #include <arpa/inet.h>

 #ifndef IFNAMESZ
 #define IFNAMESZ 16
 #endif

 int main(int argc, char *argv[])
 {
     if (argc != ) {
         printf("using %s <ETH_NAME>\n", argv[]);
         return ;
     }   

     int sock = ;
     struct sockaddr_in sin;
     struct ifreq ifr;//用来保存接口的信息

     sock = socket(AF_INET, SOCK_DGRAM, );
     if (sock == -) {
         perror("socket");
         return ;
     }
     memcpy(ifr.ifr_name, argv[], IFNAMESZ);
     ifr.ifr_name[IFNAMESZ - ] = '\0';

     if (ioctl(sock,  SIOCGIFADDR, &ifr) == ) { //SIOCGIFADDR 获取接口地址
         memcpy(&sin, &ifr.ifr_addr, sizeof(sin));   //将获得地址拷贝到 sockaddr_in 结构体中
         printf("Ip: %s\n", inet_ntoa(sin.sin_addr));
     }   

     if (ioctl(sock, SIOCGIFNETMASK, &ifr) == ) {
         memcpy(&sin, &ifr.ifr_netmask, sizeof(sin));
         printf("netmask: %s\n", inet_ntoa(sin.sin_addr));
     }
     close(sock);

     return ;
 }

运行结果如下：