使用struct ifreq实现ifconfig

ifconfig是我们查看/设定网口状态常用的命令，其实这个命令就是对一些系统函数的封装，通过对struct ifreq的修改，我们可以很轻易地设定网口状态，获取网口状态。

这个结构体位于<net/if.h>头文件中，打开去看看吧，对照着英文注释，很容易找到自己想要的东西。而网卡相关的一些ioctl操作， 也就是用于查询/修改状态的标记位，都在<linux/sockios.h>中，很清晰的，找份源码看看吧。下面是一个小示例，演示了获取信息的过程，如果有需要，也可以启用那个修改状态的函数，注意，修改状态标记位的时候，需要用到超级用户的权限。

/** * \file getifstat.c * \author  wzj * \brief 访问这个struct ifconf 修改，查询状态 * \version  * \note   * \date: 2012年08月11日星期六22:55:25 */ #include <net/if.h>/* for ifconf */#include <linux/sockios.h>/* for net status mask */#include <netinet/in.h>/* for sockaddr_in */#include <sys/socket.h>#include <sys/types.h>#include <sys/ioctl.h>#include <stdio.h>#define MAX_INTERFACE(16)void port_status(unsigned int flags);/* set == 0: do clean , set == 1: do set! */int set_if_flags(char *pif_name, int sock, int staus, int set){struct ifreq ifr;int ret = 0;strncpy(ifr.ifr_name, pif_name, strlen(pif_name) + 1);ret = ioctl(sock, SIOCGIFFLAGS, &ifr);if(ret)return -1;/* set or clean */if(set)ifr.ifr_flags |= status;else ifr.ifr_flags &= ~status;/* set flags */ret = ioctl(sock, SIOCSIFFLAGS, &ifr);if(ret)return -1;return 0;}int get_if_info(int fd){struct ifreq buf[MAX_INTERFACE];struct ifconf ifc;int ret = 0;int if_num = 0;ifc.ifc_len = sizeof(buf);ifc.ifc_buf = (caddr_t) buf;ret = ioctl(fd, SIOCGIFCONF, (char*)&ifc);if(ret){printf("get if config info failed");return -1;}/* 网口总数 ifc.ifc_len 应该是一个出入参数 */if_num = ifc.ifc_len/sizeof(struct ifreq);printf("interface num is interface = %d\n", if_num);while(if_num-- > 0){printf("net device: %s\n", buf[if_num].ifr_name);/* 获取第n个网口信息 */ret = ioctl(fd, SIOCGIFFLAGS, (char*)&buf[if_num]);if(ret)continue;/* 获取网口状态 */port_status(buf[if_num].ifr_flags);/* 获取当前网卡的ip地址 */ret = ioctl(fd, SIOCGIFADDR, (char*)&buf[if_num]);if(ret)continue;printf("IP address is: \n%s\n", inet_ntoa(((struct sockaddr_in *)(&buf[if_num].ifr_addr))->sin_addr));/* 获取当前网卡的mac */ret = ioctl(fd, SIOCGIFHWADDR, (char*)&buf[if_num]);if(ret)continue;printf("%02x:%02x:%02x:%02x:%02x:%02x\n\n",(unsigned char)buf[if_num].ifr_hwaddr.sa_data[0],(unsigned char)buf[if_num].ifr_hwaddr.sa_data[1],(unsigned char)buf[if_num].ifr_hwaddr.sa_data[2],(unsigned char)buf[if_num].ifr_hwaddr.sa_data[3],(unsigned char)buf[if_num].ifr_hwaddr.sa_data[4],(unsigned char)buf[if_num].ifr_hwaddr.sa_data[5]);}}void port_status(unsigned int flags){if(flags & IFF_UP){printf("is up\n");}if(flags & IFF_BROADCAST){printf("is broadcast\n");}if(flags & IFF_LOOPBACK){printf("is loop back\n");}if(flags & IFF_POINTOPOINT){printf("is point to point\n");}if(flags & IFF_RUNNING){printf("is running\n");}if(flags & IFF_PROMISC){printf("is promisc\n");}}int main(){int fd;fd = socket(AF_INET, SOCK_DGRAM, 0);if(fd > 0){get_if_info(fd);close(fd);}return 0;}