Linux下利用ioctl函数获取网卡信息_ioctl查询网卡是否存在-优快云博客

linux下的ioctl函数原型如下：

#include <sys/ioctl.h>

int ioctl(int handle, int cmd, [int *argc, int argv])

函数成功返回0，失败返回-1.

其相关命令接口如下：

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ID	int int int
文件	FIONBIO 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ID	int 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 ifreq
ARP	SIOCSARP 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

在这里我们需要用到的结构体

#include<netinet/in.h>

struct sockaddr_in {

short sin_family; /* Address family */

unsigned short sin_port; /* Port number */

struct in_addr sin_addr; /* Internet address */

unsigned char sin_zero[8]; /* Same size as struct sockaddr */

};

#include <net/if.h>

struct ifreq
{
#define IFHWADDRLEN 6
union
{
charifrn_name[IFNAMSIZ];
} ifr_ifrn;

union {
structsockaddr ifru_addr;
structsockaddr ifru_dstaddr;
structsockaddr ifru_broadaddr;
structsockaddr ifru_netmask;
struct sockaddr ifru_hwaddr;
shortifru_flags;
intifru_ivalue;
intifru_mtu;
struct ifmap ifru_map;
charifru_slave[IFNAMSIZ];
charifru_newname[IFNAMSIZ];
void __user * ifru_data;
structif_settings ifru_settings;
} ifr_ifru;
};

#define ifr_name ifr_ifrn.ifrn_name
#define ifr_hwaddr ifr_ifru.ifru_hwaddr
#defineifr_addr ifr_ifru.ifru_addr
#defineifr_dstaddr ifr_ifru.ifru_dstaddr
#defineifr_broadaddr ifr_ifru.ifru_broadaddr
#defineifr_netmask ifr_ifru.ifru_netmask
#defineifr_flags ifr_ifru.ifru_flags
#defineifr_metric ifr_ifru.ifru_ivalue
#defineifr_mtu ifr_ifru.ifru_mtu
#define ifr_map ifr_ifru.ifru_map
#define ifr_slave ifr_ifru.ifru_slave
#defineifr_data ifr_ifru.ifru_data
#define ifr_ifindex ifr_ifru.ifru_ivalue
#define ifr_bandwidth ifr_ifru.ifru_ivalue
#define ifr_qlen ifr_ifru.ifru_ivalue
#define ifr_newname ifr_ifru.ifru_newname
#define ifr_settings ifr_ifru.ifru_setting

ioctl函数能获取到IP地址、子网掩码、广播地址、硬件MAC地址等信息，至于网关及路由表比较复杂，在此不讨论。

具体代码如下：（测试通过）

#include <stdio.h>

#include <stdlib.h>

#include <net/if.h>

#include <unistd.h>

#include <sys/ioctl.h>

#include <arpa/inet.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <errno.h>

#include <fcntl.h>

#include <netinet/in.h>

#include <net/route.h>

#include <string.h>

#include <net/if_arp.h>

int main()

{

struct sockaddr_in *sin;

struct ifreq ifr;

FILE *dns;

FILE *gw;

char *ip = new char(16);

char *netmask = new char(16);

char *broadcast = new char(16);

//char *ip = (char *)malloc(16);

char *mac = new char(32);

//char *mac = (char *)malloc(32);

int socket_fd;

if((socket_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0){

perror("socket");

exit(1);

}

memset(&ifr, 0, sizeof(ifr));

strcpy(ifr.ifr_name, "eth0");

memset(&sin, 0, sizeof(sin));

//获取IP地址

if(ioctl(socket_fd, SIOCGIFADDR, &ifr) != -1){

sin = (struct sockaddr_in *)&ifr.ifr_addr;

strcpy(ip, inet_ntoa(sin->sin_addr));

printf("IP address is %s\n", ip);

}

//获取广播地址

if(ioctl(socket_fd, SIOCGIFBRDADDR, &ifr) != -1){

sin = (struct sockaddr_in *)&ifr.ifr_broadaddr;

strcpy(broadcast, inet_ntoa(sin->sin_addr));

printf("Broadcast is %s\n", broadcast);

}

//获取子网掩码

if(ioctl(socket_fd, SIOCGIFNETMASK, &ifr) != -1){

sin = (struct sockaddr_in *)&ifr.ifr_broadaddr;

strcpy(netmask, inet_ntoa(sin->sin_addr));

printf("Net-mask is %s\n", netmask);

}

//获取硬件MAC地址

if(ioctl(socket_fd, SIOCGIFHWADDR, &ifr) != -1){

sin = (struct sockaddr_in *)&ifr.ifr_netmask;

sprintf(mac, "%02x:%02x:%02x:%02x:%02x:%02x",

(unsigned char)ifr.ifr_netmask.sa_data[0],

(unsigned char)ifr.ifr_netmask.sa_data[1],

(unsigned char)ifr.ifr_netmask.sa_data[2],

(unsigned char)ifr.ifr_netmask.sa_data[3],

(unsigned char)ifr.ifr_netmask.sa_data[4],

(unsigned char)ifr.ifr_netmask.sa_data[5]);

printf("Mac address is %s\n", mac);

}

return 0;

}

至于获取网关以及DNS，我是通过相关命令获得的。

主要代码如下：

//获取网关，利用route -n 命令可以看到相关的网关。连接标志是‘UG’

if(gw_fd = popen("route -n | grep 'UG'", "r")){

fread(temp,1,128, gw_fd);

sscanf(temp, "%*s%s", szNetGate);

printf("Gateway is %s\n", szNetGate);

}

//获取DNS；一般DNS保存在/etc/reslov.conf文件中。具体获得方法要根据实际情况而定。

我的配置文件中是这样的

root@nill:/home/arm-none-linux# cat /etc/resolv.conf

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)

# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN

nameserver 202.96.134.133

上面的202.96.134.133就是我需要获取的主DNS，没有备用DNS

if(dns_fd = popen("cat /etc/reslov.conf | grep 'nameserver'", "r")){

fread(temp,1,128, gw_fd);

sscanf(temp, "%*s%s%*s%s", szDNS1,szDNS2);

printf("DNS1 is %s",szDNS1);

printf("DNS2is %s", szDNS2);

}

转载地址：http://5375342.blog.51cto.com/5365342/1209335

写在前面

获取与设置网卡信息的方法有很多种，本文就传统的通过ioctl接口获取的方法做个记录。

此外，通过ioctl还可以获取网卡设备的映射属性。更进一步，可以让我们查看，修改，删除系统的ARP高速缓存和路由表信息。

相关结构体

这里主要相关的两个结构体定义在glibc头文件/usr/include/net/if.h中，分别为struct ifconf和struct ifreq。

/* 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
      {
        __caddr_t ifcu_buf;
        struct ifreq *ifcu_req;
      } ifc_ifcu;
  };
# define ifc_buf        ifc_ifcu.ifcu_buf       /* Buffer address.  */
# define ifc_req        ifc_ifcu.ifcu_req       /* Array of structures.  */
# define _IOT_ifconf _IOT(_IOTS(struct ifconf),1,0,0,0,0) /* not right */
#endif  /* Misc.  */

从注释信息中可以看出struct ifconf主要是用来利用ioctl函数的SIOCGIFCONF request来获取系统中所有网络接口的信息。关于它的具体用法，后文会有示例。

既然是关于系统中所有的网络接口信息，那么一个网络接口信息用什么结构来表示呢？这就是struct ifreq的用处了。

/* 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)

struct ifreq中的信息就是一个网络接口的所有属性了，平时用的最多的ifconfig命令的输出就是这些属性的陈列。