本文介绍了一个C语言程序，用于获取Linux系统的网卡数量及其详细信息，包括网卡名称、MAC地址、IP地址、广播地址和子网掩码。通过`socket`、`ioctl`等系统调用遍历并打印所有接口信息，与`ifconfig`命令输出信息一致。

功能介绍

• 获取 Linux 系统网卡数量（包括环回）
• 遍历每张网卡
• 打印网卡的 名称、MAC 地址、IP 地址、广播地址、子网掩码

源码

interface_info.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#include <net/if.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>

int sock_get_local_info(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)) {
        interfaceNum = ifc.ifc_len / sizeof(struct ifreq);
        printf("interface num = %d\n", interfaceNum);
        while (interfaceNum-- > 0) {
            printf("\ndevice name: %s\n", buf[interfaceNum].ifr_name);

            //ignore the interface that not up or not runing
            ifrcopy = buf[interfaceNum];
            if (ioctl(fd, SIOCGIFFLAGS, &ifrcopy)) {
                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: %s\n", 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: %s\n", 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: %s\n", 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: %s\n", 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(int argc, char *argv[])
{
    sock_get_local_info();

	return EXIT_SUCCESS;
}

编译

gcc interface_info.c -o interface_info.out -Wall

运行

$ ./interface_info.out 
interface num = 2

device name: enp0s3
device mac: 08002738fcd0
device ip: 192.168.31.223
device broadAddr: 192.168.31.255
device subnetMask: 255.255.255.0

device name: lo
device mac: 000000000000
device ip: 127.0.0.1
device broadAddr: 0.0.0.0
device subnetMask: 255.0.0.0

和 ifconfig 命令显示的信息一致

$ ifconfig 
enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.31.223  netmask 255.255.255.0  broadcast 192.168.31.255
        ether 08:00:27:38:fc:d0  txqueuelen 1000  (以太网)
        RX packets 183199  bytes 179974182 (179.9 MB)
        RX errors 0  dropped 193  overruns 0  frame 0
        TX packets 68178  bytes 7018396 (7.0 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (本地环回)
        RX packets 4025  bytes 399305 (399.3 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 4025  bytes 399305 (399.3 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0