get mac addr

bsd_get_mac.c

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

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

int bsd_get_mac(const char ifname[], uint8_t mac[]) {
        struct ifreq *ifrp;
        struct ifconf ifc;
        char buf[512];
        int sockfd, len = 0;
        ifc.ifc_len = sizeof(buf);
        ifc.ifc_buf = buf;

        sockfd = socket(AF_INET, SOCK_DGRAM, 0);
        if (ioctl(sockfd, SIOCGIFCONF, &ifc) < 0) {
                perror("ioctl");
                return -1;
        }
        if (ifc.ifc_len > sizeof(buf))
                return 1;
        ifrp = ifc.ifc_req;
        do {
                struct sockaddr *sa = &ifrp->ifr_addr;
                if (((struct sockaddr_dl *)sa)->sdl_type == IFT_ETHER) {
                        if (strcmp(ifname, ifrp->ifr_name) == 0) {
                                memcpy(mac, LLADDR((struct sockaddr_dl *)&ifrp->ifr_addr), 6);
                                return 0;
                        }
                }
                ifrp = (struct ifreq *)(sa->sa_len + (caddr_t)&ifrp->ifr_addr);
                len += sa->sa_len + sizeof(ifrp->ifr_name);
        } while (len < ifc.ifc_len);
        return 0;
}

int main(void) {
        uint8_t mac[6];
        bsd_get_mac("en0", mac);
        printf("%02x:%02x:%02x:%02x:%02x:%02x\n",
                        mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
        return 0;
}