interface.c

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

#ifdef __sunos__
#include <sys/sockio.h>
#endif

#define inaddrr(x) (*(struct in_addr *) &ifr->x[sizeof sa.sin_port])

#if defined(__AIX) || defined(_AIX)
#define MAX(x,y) ((x) > (y) ? (x) : (y))
#define SIZE(p) MAX((p).sa_len, sizeof(p))
#else
#define IFRSIZE ((int)(size * sizeof (struct ifreq)))
#endif


int main ()
{
    unsigned char	*u = NULL;
    int	sockfd;
    int	size = 1;
    struct ifreq	*ifr;
    struct ifconf	ifc;
    struct sockaddr_in	sa;
    struct arpreq	arp;
    char	macStr[128];

    if (0 > (sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP)))
    {
        printf ("Error: Unable to open socket.\n");
        exit (1);
    }

#if defined(__AIX__) || defined(_AIX)
    if (ioctl (sockfd, SIOCGSIZIFCONF, &size) == -1)
{
perror("Error getting size of interface :");
exit (1);
}

ifc.ifc_req = (struct ifreq *) malloc (size);
ifc.ifc_len = size;

if (ioctl(sockfd, SIOCGIFCONF, &ifc))
{
printf ("Error: ioctl SIOCFIFCONF.\n");
exit (1);
}
#else
    ifc.ifc_len = IFRSIZE;
    ifc.ifc_req = NULL;

    do
    {
        ++size;
/* realloc buffer size until no overflow occurs */

        if (NULL == (ifc.ifc_req = (struct ifreq*)realloc(ifc.ifc_req, IFRSIZE)))
        {
            printf ("Error: Unable to allocate mememory.\n");
            exit (1);
        }

        ifc.ifc_len = IFRSIZE;
        if (ioctl(sockfd, SIOCGIFCONF, &ifc))
        {
            printf ("Error: ioctl SIOCFIFCONF.\n");
            exit (1);
        }
    } while (IFRSIZE <= ifc.ifc_len);
#endif

    ifr = ifc.ifc_req;

    while ((char *) ifr < (char *) ifc.ifc_req + ifc.ifc_len)
    {
        printf("Interface: %s\n", ifr->ifr_name);
        printf("IP Address: %s\n", inet_ntoa(inaddrr(ifr_addr.sa_data)));


        u = NULL;
#if defined(__linux__) || defined(linux)
        if (0 == ioctl(sockfd, SIOCGIFHWADDR, ifr))
            u = (unsigned char *) &ifr->ifr_addr.sa_data;
        else
        {
#endif

            arp.arp_pa = ifr->ifr_addr;
            if (0 == ioctl (sockfd, SIOCGARP, &arp))
                u = (unsigned char *) arp.arp_ha.sa_data;
            else
                perror ("Error during ioctl");
#if defined(__linux__) || defined(linux)
        }
#endif

        memset (macStr, 0, sizeof (macStr));
        if (u && u[0] + u[1] + u[2] + u[3] + u[4] + u[5])
        {
            sprintf (macStr, "%2.2X-%2.2X-%2.2X-%2.2X-%2.2X-%2.2X", u[0], u[1], u[2], u[3], u[4], u[5]);
            printf ("HW Address: %s", macStr);
        }

        printf("\n");


#if defined(__AIX) || defined(_AIX)
        ifr = ((char *) ifr + sizeof(ifr->ifr_name) + SIZE(ifr->ifr_addr));
#else
        ++ifr;
#endif
    }

    close(sockfd);
}