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

太过爱你忘了你带给我的痛 2021-08-29 15:48 248阅读 0赞

**目录**

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

<table style="width:576px;"> 
 <tbody> 
 <tr> 
 <td style="vertical-align:top;"> SIOCGIFCONF SIOCSIFADDR SIOCGIFADDR SIOCSIFFLAGS SIOCGIFFLAGS SIOCSIFDSTADDR SIOCGIFDSTADDR SIOCGIFBRDADDR SIOCSIFBRDADDR SIOCGIFNETMASK SIOCSIFNETMASK SIOCGIFMETRIC SIOCSIFMETRIC SIOCGIFMTU SIOCxxx </td> 
 <td style="vertical-align:top;"> 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） </td> 
 <td style="vertical-align:top;"> 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 ifreq &nbsp; </td> 
 </tr> 
 </tbody> 
</table>

### 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	6
    	union
    	{
    		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）

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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 vector
 struct 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$

[Center]: /images/20210728/8fb42d8383bd4b1d9637e995d3956c5d.png