get iface index

gistfile1.txt

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/ethtool.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <string.h>
#include <errno.h>


static int iface_get_id(const char *device)
{
    struct ifreq ifr;

    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));

    int fd = socket(PF_PACKET, SOCK_DGRAM, 0);
    if (fd == -1) {
        perror("get raw socket fail");
        return -1;
    }

    if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) {
        perror("ioctl SIOCGIFINDEX fail");
        return -1;
    }

    return ifr.ifr_ifindex;
}

int main()
{
    const char *device = "eth0";
    int dev_id = iface_get_id(device);
    if (dev_id == -1) {
        fprintf(stderr, "fail to get index\n");
    } else {
        printf("device %s's index is %d'\n", device, dev_id);
    }
    
    return 0;
}