Get MAC address using POSIX APIs

#include <stdio.h>
#include <unistd.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>

#define MAXINTERFACES 16

void get_ip()
{
    int sock_fd;
    struct ifreq buf[MAXINTERFACES];
    struct ifconf ifc;
    int interface_num;
    char *addr;//[ADDR_LEN];

    if((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        printf("Create socket failed");
        return;
    }
    ifc.ifc_len = sizeof(buf);
    ifc.ifc_req = buf;
    if(ioctl(sock_fd, SIOCGIFCONF, (char *)&ifc) < 0)
    {
        printf("Get a list of interface addresses failed");
        return;
    }
    
    interface_num = ifc.ifc_len / sizeof(struct ifreq);
    printf("The number of interfaces is %d ", interface_num);

    while(interface_num--) 
    {
        printf("Net device: %s ", buf[interface_num].ifr_name);

        if(ioctl(sock_fd, SIOCGIFFLAGS, (char *)&buf[interface_num]) < 0)
        {
            printf("Get the active flag word of the device");
            continue;
        }
        if(buf[interface_num].ifr_flags & IFF_PROMISC)
            printf("Interface is in promiscuous mode ");

        if(buf[interface_num].ifr_flags & IFF_UP)
            printf("Interface is running ");
        else
            printf("Interface is not running ");

        if(ioctl(sock_fd, SIOCGIFADDR, (char *)&buf[interface_num]) < 0)
        {
            printf("Get interface address failed");
            continue;
        }
        addr = inet_ntoa(((struct sockaddr_in*)(&buf[interface_num].ifr_addr))->sin_addr);
        printf("IP address is %s ", addr);  
    }

close(sock_fd);
    return;
}

void get_mac()
{
    int sock_fd;
    struct ifreq buf[MAXINTERFACES];
    struct ifconf ifc;
    int interface_num;
    
    if((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        printf("Create socket failed");
        return;
    }
    ifc.ifc_len = sizeof(buf);
    ifc.ifc_req = buf;
    if(ioctl(sock_fd, SIOCGIFCONF, (char *)&ifc) < 0)
    {
        printf("Get a list of interface addresses failed");
        return;
    }
    interface_num = ifc.ifc_len / sizeof(struct ifreq);
    printf("The number of interfaces is %d ", interface_num);

    while(interface_num--) 
    {
        printf("Net device: %s ", buf[interface_num].ifr_name);

        if(ioctl(sock_fd, SIOCGIFFLAGS, (char *)&buf[interface_num]) < 0)
        {
            printf("Get the active flag word of the device");
            continue;
        }
        if(buf[interface_num].ifr_flags & IFF_PROMISC)
            printf("Interface is in promiscuous mode ");

        if(buf[interface_num].ifr_flags & IFF_UP)
            printf("Interface is running ");
        else
            printf("Interface is not running ");

        if(ioctl(sock_fd, SIOCGIFHWADDR, (char *)&buf[interface_num]) < 0)
        {
            printf("Get the hardware address of a device failed");
            continue;
        }

        printf("Mac address is: %02X:%02X:%02X:%02X:%02X:%02X ",
            (unsigned char)buf[interface_num].ifr_hwaddr.sa_data[0],
            (unsigned char)buf[interface_num].ifr_hwaddr.sa_data[1],
            (unsigned char)buf[interface_num].ifr_hwaddr.sa_data[2],
            (unsigned char)buf[interface_num].ifr_hwaddr.sa_data[3],
            (unsigned char)buf[interface_num].ifr_hwaddr.sa_data[4],
            (unsigned char)buf[interface_num].ifr_hwaddr.sa_data[5]);
    }

   close(sock_fd);
}