linux c 获取网络接口信息 ioct l函数 ifreq ifconf 结构体简介

ioctl

struct ifreq

struct ifconf

ioctl

原型如下：

#include <sys/ioctl.h>
int ioctl(int fd, int request, ...);

参数：

fd ：文件描述符

request：表示要请求的信息。如IP地址、网络掩码等

... ：后面的可变参数根据request而定

比如我们请求所有网络接口的清单：

struct ifconf IoCtlReq;
...
ioctl( Sock, SIOCGIFCONF, &IoCtlReq )

与接口相关的request如下表所示

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

结构体 struct ifreq用来保存某个接口的信息。

// if.h
/** 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 6union{char ifrn_name[IFNAMSIZ];        /* if 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    ifru_flags;int  ifru_ivalue;int ifru_mtu;struct  ifmap ifru_map;char    ifru_slave[IFNAMSIZ];   /* Just fits the size */char    ifru_newname[IFNAMSIZ];void __user *    ifru_data;struct    if_settings ifru_settings;} 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 ifr_settings    ifr_ifru.ifru_settings  /* Device/proto settings*/

ifr_name 标识了某一接口。

可以通过ioctl获取该接口的信息。如：

ioctl(Sock, SIOCGIFNETMASK, &IfReq);//获取网络接口地址掩码

该代码需要先对IfReq->ifr_name赋值，然后获取与IfReq->ifr_name向匹配的网络接口的地址掩码

struct ifconf

结构体struct ifconf通常用来保存所有接口信息

// if.h
/** 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 {char __user *ifcu_buf;struct ifreq __user *ifcu_req;} ifc_ifcu;
};
#define ifc_buf ifc_ifcu.ifcu_buf       /* buffer address   */
#define ifc_req ifc_ifcu.ifcu_req       /* array of structures  */

该结构体可以用来获取所哟网络接口的名字和信息（不是全部信息，是ip地址）

实例：

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <string.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
typedef uint32_t uint32;
#define MAX_IF 10
int main()
{struct ifreq ifVec[MAX_IF];//用来保存所有接口int sock = -1;if ((sock = socket( AF_INET, SOCK_DGRAM, 0 )) < 0){fprintf(stderr, "Error:%d, cannot open RAM;\n");}// get if vectorstruct ifconf ioIfConf;ioIfConf.ifc_buf = (void *)ifVec;ioIfConf.ifc_len = sizeof(ifVec);printf("Len:%d\n", ioIfConf.ifc_len);if (ioctl(sock, SIOCGIFCONF, &ioIfConf) < 0) //获取所有网络接口信息{fprintf(stderr, "Error:%d   ioctl IFCONF\n");}printf("Len:%d\n", ioIfConf.ifc_len); // 和前面到len对比，发现ioctl修改里len到大小//循环打印每个网络接口到信息{struct ifreq *ifPt;struct ifreq *ifEndPt;ifPt = ifVec;ifEndPt = (void *)((char *)ifVec + ioIfConf.ifc_len);for (ifPt = ifVec; ifPt < ifEndPt; ifPt++){struct ifreq ifReq;if (ifPt->ifr_addr.sa_family != AF_INET){continue;}// Temp keepers of interface params...uint32 u32_addr, u32_mask;/*   打印ip地址  */char ipDotBuf[16], subnetDotBuf[16], maskDotBuf[16]; // 保存点分十进制到ip地址u32_addr = ((struct sockaddr_in *)&ifPt->ifr_addr)->sin_addr.s_addr;inet_ntop(AF_INET, &u32_addr, ipDotBuf, (socklen_t )sizeof(ipDotBuf));printf("IP Address: %s\n", ipDotBuf);/*    打印地址掩码    */bzero(&ifReq, sizeof(struct ifreq));memcpy(ifReq.ifr_name, ifPt->ifr_name, sizeof(ifReq.ifr_name));if (ioctl(sock, SIOCGIFNETMASK, &ifReq ) < 0){fprintf(stderr, "Error: %d, cannot get mask\n", errno);}else{u32_mask = ((struct sockaddr_in *)&ifReq.ifr_addr)->sin_addr.s_addr;inet_ntop(AF_INET, &u32_mask, maskDotBuf, (socklen_t )sizeof(maskDotBuf));printf("Mask: %s\n", maskDotBuf);}/*    打印MTU    */bzero(&ifReq, sizeof(struct ifreq));memcpy(ifReq.ifr_name, ifPt->ifr_name, sizeof(ifReq.ifr_name));if (ioctl(sock, SIOCGIFMTU, &ifReq ) < 0){fprintf(stderr, "Error: %d, cannot get MTU\n", errno);}else{printf("SIOCGIFMTU:%d\n", ifReq.ifr_mtu);}/*    其他信息的打印方式与掩码和MTU相同    */}}
}

运行结果：

windeal@ubuntu:~/Windeal/apue$ ./exe
Len:320
Len:64
IP Address: 127.0.0.1
Mask: 255.0.0.0
SIOCGIFMTU:16436
IP Address: 172.17.92.198
Mask: 255.255.254.0
SIOCGIFMTU:1500
windeal@ubuntu:~/Windeal/apue$