最近项目中需要获取linux系统的所有网口信息并设置默认网口，通过查询资料发现通过linux提供的ioctl()函数可以获取相关信息。下面首先介绍几个需要使用到的结构体，然后提供一个实例。
1. 结构体ifconf和ifreq
//ifconf通常是用来保存所有接口信息的
struct ifconf
{
int ifc_len; /* size of buffer */
union
{
char *ifcu_buf; /* input from user->kernel*/
struct ifreq *ifcu_req; /* return from kernel->user*/
} ifc_ifcu;
};
//ifreq用来保存某个接口的信息
struct ifreq {
char ifr_name[IFNAMSIZ];
union {
struct sockaddr ifru_addr;
struct sockaddr ifru_dstaddr;
struct sockaddr ifru_broadaddr;
short ifru_flags;
int ifru_metric;
caddr_t ifru_data;
} ifr_ifru;
};
2. 结构体sockaddr和sockaddr_in
struct sockaddr {
unsigned short sa_family; // 2 bytes address family, AF_xxx
char sa_data[14]; // 14 bytes of protocol address
};
struct sockaddr_in {
short sin_family; // 2 bytes e.g. AF_INET, AF_INET6
unsigned short sin_port; // 2 bytes e.g. htons(3490)
struct in_addr sin_addr; // 4 bytes see struct in_addr, below
char sin_zero[8]; // 8 bytes zero this if you want to
};
struct in_addr {
unsigned long s_addr; // 4 bytes load with inet_pton()
};
二者长度一样，都是16个字节，即占用的内存大小是一致的，因此可以互相转化。二者是并列结构，指向sockaddr_in结构的指针也可以指向sockaddr。
3. 实例
#include
#include
#include
#include
#include
#include
int getInterfaceInfo(void)
{
int fd;
int interfaceNum = 0;
struct ifreq buf[16];
struct ifconf ifc;
struct ifreq ifrcopy;
char mac[16] = {0};
char ip[32] = {0};
char broadAddr[32] = {0};
char subnetMask[32] = {0};
if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
perror(“socket”);
close(fd);
return -1;
}
ifc.ifc_len = sizeof(buf);
ifc.ifc_buf = (caddr_t)buf;
if (!ioctl(fd, SIOCGIFCONF, (char *)&ifc))//获取所有网口信息
{
interfaceNum = ifc.ifc_len / sizeof(struct ifreq);
printf(“interface num = %dn”, interfaceNum);
while (interfaceNum– > 0) //逐个提取
{
printf(“ndevice name: %sn”, buf[interfaceNum].ifr_name);
//ignore the interface that not up or not runing
ifrcopy = buf[interfaceNum];
if (ioctl(fd, SIOCGIFFLAGS, &ifrcopy))//设置网口标记
{
printf(“ioctl: %s [%s:%d]n”, strerror(errno), __FILE__, __LINE__);
close(fd);
return -1;
}
//get the mac of this interface
if (!ioctl(fd, SIOCGIFHWADDR, (char *)(&buf[interfaceNum])))
{
memset(mac, 0, sizeof(mac));
snprintf(mac, sizeof(mac), “%02x%02x%02x%02x%02x%02x”,
(unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[0],
(unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[1],
(unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[2],
(unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[3],
(unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[4],
(unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[5]);
printf(“device mac: %sn”, mac);
}
else
{
printf(“ioctl: %s [%s:%d]n”, strerror(errno), __FILE__, __LINE__);
close(fd);
return -1;
}
//get the IP of this interface
if (!ioctl(fd, SIOCGIFADDR, (char *)&buf[interfaceNum]))
{
snprintf(ip, sizeof(ip), “%s”,
(char *)inet_ntoa(((struct sockaddr_in * &
(buf[interfaceNum].ifr_addr))->sin_addr));
printf(“device ip: %sn”, ip);
}
else
{
printf(“ioctl: %s [%s:%d]n”, strerror(errno), __FILE__, __LINE__);
close(fd);
return -1;
}
//get the broad address of this interface
if (!ioctl(fd, SIOCGIFBRDADDR, &buf[interfaceNum]))
{
snprintf(broadAddr, sizeof(broadAddr), “%s”,
(char *)inet_ntoa(((struct sockaddr_in *)&
(buf[interfaceNum].ifr_broadaddr))->sin_addr));
printf(“device broadAddr: %sn”, broadAddr);
}
else
{
printf(“ioctl: %s [%s:%d]n”, strerror(errno), __FILE__, __LINE__);
close(fd);
return -1;
}
//get the subnet mask of this interface
if (!ioctl(fd, SIOCGIFNETMASK, &buf[interfaceNum]))
{
snprintf(subnetMask, sizeof(subnetMask), “%s”,
(char *)inet_ntoa(((struct sockaddr_in *)&
(buf[interfaceNum].ifr_netmask))->sin_addr));
printf(“device subnetMask: %sn”, subnetMask);
}
else
{
printf(“ioctl: %s [%s:%d]n”, strerror(errno), __FILE__, __LINE__);
close(fd);
return -1;
}
}
}
else
{
printf(“ioctl: %s [%s:%d]n”, strerror(errno), __FILE__, __LINE__);
close(fd);
return -1;
}
close(fd);
return 0;
}
int main(void)
{
getInterfaceInfo();
return 0;
}
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