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

1 #include <sys/ioctl.h>
2
3 int ioctl(int d, int request, ...);
4
5 //参数
6 //int d：是一个文件描述符
7 //int request ：表示要请求的信息。如IP地址、网络掩码等
8 //......: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

 1  /* Interface request structure used for socket ioctl‘s.  All interface
 2     ioctl‘s must have parameter definitions which begin with ifr_name.
 3     The remainder may be interface specific.  */
 4
 5 struct ifreq
 6 {
 7 # define IFHWADDRLEN    6
 8 # define IFNAMSIZ   IF_NAMESIZE
 9      union
10        {
11      char ifrn_name[IFNAMSIZ];   /* Interface name, e.g. "en0".  */
12        } ifr_ifrn;
13
14      union
15        {
16      struct sockaddr ifru_addr;
17      struct sockaddr ifru_dstaddr;
18      struct sockaddr ifru_broadaddr;
19      struct sockaddr ifru_netmask;
20      struct sockaddr ifru_hwaddr;
21      short int ifru_flags;
22      int ifru_ivalue;
23      int ifru_mtu;
24      struct ifmap ifru_map;
25      char ifru_slave[IFNAMSIZ];  /* Just fits the size */
26      char ifru_newname[IFNAMSIZ];
27      __caddr_t ifru_data;
28        } ifr_ifru;
29    };
30  # define ifr_name   ifr_ifrn.ifrn_name  /* interface name   */
31  # define ifr_hwaddr ifr_ifru.ifru_hwaddr    /* MAC address      */
32  # define ifr_addr   ifr_ifru.ifru_addr  /* address      */
33  # define ifr_dstaddr    ifr_ifru.ifru_dstaddr   /* other end of p-p lnk */
34  # define ifr_broadaddr  ifr_ifru.ifru_broadaddr /* broadcast address    */
35  # define ifr_netmask    ifr_ifru.ifru_netmask   /* interface net mask   */
36  # define ifr_flags  ifr_ifru.ifru_flags /* flags        */
37  # define ifr_metric ifr_ifru.ifru_ivalue    /* metric       */
38  # define ifr_mtu    ifr_ifru.ifru_mtu   /* mtu          */
39  # define ifr_map    ifr_ifru.ifru_map   /* device map       */
40  # define ifr_slave  ifr_ifru.ifru_slave /* slave device     */
41  # define ifr_data   ifr_ifru.ifru_data  /* for use by interface */
42  # define ifr_ifindex    ifr_ifru.ifru_ivalue    /* interface index      */
43  # define ifr_bandwidth  ifr_ifru.ifru_ivalue    /* link bandwidth   */
44  # define ifr_qlen   ifr_ifru.ifru_ivalue    /* queue length     */
45  # define ifr_newname    ifr_ifru.ifru_newname   /* New name     */
46  # define _IOT_ifreq _IOT(_IOTS(char),IFNAMSIZ,_IOTS(char),16,0,0)
47  # define _IOT_ifreq_short _IOT(_IOTS(char),IFNAMSIZ,_IOTS(short),1,0,0)
48  # define _IOT_ifreq_int _IOT(_IOTS(char),IFNAMSIZ,_IOTS(int),1,0,0)

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。

 1  /* Structure used in SIOCGIFCONF request.  Used to retrieve interface
 2     configuration for machine (useful for programs which must know all
 3     networks accessible).  */
 4
 5  struct ifconf
 6    {
 7      int ifc_len;            /* Size of buffer.  */
 8      union
 9        {
10      __caddr_t ifcu_buf;
11      struct ifreq *ifcu_req;
12        } ifc_ifcu;
13    };
14  # define ifc_buf    ifc_ifcu.ifcu_buf   /* Buffer address.  */
15  # define ifc_req    ifc_ifcu.ifcu_req   /* Array of structures.  */
16  # define _IOT_ifconf _IOT(_IOTS(struct ifconf),1,0,0,0,0) /* not right */
17  #endif  /* Misc.  */

下面程序是获取本机的IP地址

 1 #include <stdio.h>
 2 #include <sys/socket.h>
 3 #include <string.h>
 4 #include <sys/types.h>
 5 #include <netinet/in.h>
 6 #include <sys/ioctl.h>
 7 #include <net/if.h>
 8
 9 //#define ETH_NAME "eth0"
10 //#define NET_NAME  "wlan1"
11
12 int main(int argc, char *argv[])
13 {
14     if(argc != 2) {
15         printf("using %s <ETH_NAME>\n", argv[0]);
16         return 0;
17     }
18
19     int sock = 0;
20     struct sockaddr_in sin;
21     struct ifreq ifr;//用来保存接口的信息
22
23     sock = socket(AF_INET, SOCK_DGRAM, 0);
24     if(sock == -1) {
25         perror("socket");
26         return 1;
27     }
28
29     strcpy(ifr.ifr_name, argv[1]);
30     int ret = ioctl(sock,  SIOCGIFADDR, &ifr);//SIOCGIFADDR 获取接口地址
31     if(ret < 0) {
32         perror("ioctl");
33         return 1;
34     }
35
36     memcpy(&sin, &ifr.ifr_addr, sizeof(sin));//将获得地址拷贝到 sockaddr_in 结构体中
37     printf("%s\n", inet_ntoa(sin.sin_addr));//显示
38     return 0;
39
40 }

运行结果如下：