struct ifreq学习和实例

一、struct ifreq结构体

这个结构定义在/usr/include/net/if.h，用来配置和获取ip地址，掩码，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 6# 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),16,0,0)# define _IOT_ifreq_short _IOT(_IOTS(char),IFNAMSIZ,_IOTS(short),1,0,0)# define _IOT_ifreq_int _IOT(_IOTS(char),IFNAMSIZ,_IOTS(int),1,0,0)

二、用法：

通过ioctl()函数调用
下表列出了网络相关ioctl请求的request 参数以及arg 地址必须指向的数据类型：

　　

类别Request说明数据类型套
接
口SIOCATMARK 
SIOCSPGRP 
SIOCGPGRP是否位于带外标记 
设置套接口的进程ID 或进程组ID 
获取套接口的进程ID 或进程组IDint 
int 
int文
件FIONBIN 
FIOASYNC 
FIONREAD 
FIOSETOWN 
FIOGETOWN设置/ 清除非阻塞I/O 标志 
设置/ 清除信号驱动异步I/O 标志 
获取接收缓存区中的字节数 
设置文件的进程ID 或进程组ID 
获取文件的进程ID 或进程组IDint 
int 
int 
int 
int接
口SIOCGIFCONF 
SIOCSIFADDR 
SIOCGIFADDR 
SIOCSIFFLAGS 
SIOCGIFFLAGS 
SIOCSIFDSTADDR 
SIOCGIFDSTADDR 
SIOCGIFBRDADDR 
SIOCSIFBRDADDR 
SIOCGIFNETMASK 
SIOCSIFNETMASK 
SIOCGIFMETRIC 
SIOCSIFMETRIC 
SIOCGIFMTU 
SIOCxxx获取所有接口的清单 
设置接口地址 
获取接口地址 
设置接口标志 
获取接口标志 
设置点到点地址 
获取点到点地址 
获取广播地址 
设置广播地址 
获取子网掩码 
设置子网掩码 
获取接口的测度 
设置接口的测度 
获取接口MTU 
（还有很多取决于系统的实现）struct ifconf 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreq 
struct ifreqARPSIOCSARP 
SIOCGARP 
SIOCDARP创建/ 修改ARP 表项 
获取ARP 表项 
删除ARP 表项struct arpreq 
struct arpreq 
struct arpreq路
由SIOCADDRT 
SIOCDELRT增加路径 
删除路径struct rtentry 
struct rtentry流I_xxx

实例一，获取网卡的IP地址：

#include <string.h>#include <sys/socket.h>#include <sys/ioctl.h>#include <net/if.h>#include <stdio.h>#include <netinet/in.h>#include <arpa/inet.h>int main(){        int inet_sock;        struct ifreq ifr;        inet_sock = socket(AF_INET, SOCK_DGRAM, 0);        strcpy(ifr.ifr_name, "eth0");        //SIOCGIFADDR标志代表获取接口地址        if (ioctl(inet_sock, SIOCGIFADDR, &ifr) <  0)                perror("ioctl");        printf("%s\n", inet_ntoa(((struct sockaddr_in*)&(ifr.ifr_addr))->sin_addr));        return 0;}

实例二，实现简单ifconfig功能：

/** * \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 status, 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;}

运行结果：

interface num is interface = 2
net device: eth0
is up
is broadcast
is running
IP address is: 
192.168.100.200
54:be:f7:33:57:26


net device: lo
is up
is loop back
is running
IP address is: 
127.0.0.1
00:00:00:00:00:00

参考转载博客地址：

http://blog.csdn.net/dsg333/article/details/7525634

http://blog.csdn.net/kulung/article/details/6442597

http://blog.csdn.net/joker0910/article/details/7855998