#include <string.h>
#include <assert.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>

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

int main(int argc, const char *argv[])
{
    #define _IPV6_CUSTOM_FILE "/var/if_inet6"
    #define _IPV6_RESOURCE_FILE "/proc/net/if_inet6"
    FILE *fp = NULL;
    char address[8][5];
    unsigned int if_idx = 0, plen = 0, scope = 0, dad_status = 0;
    char iface[32] = {0};
    unsigned int tmp = 0;
    struct in6_addr ipv6addr = in6addr_any;
    char txt_ipv6_address[130];

    memset((char *)address, 0x00, sizeof(address));
    fp = fopen(_IPV6_CUSTOM_FILE, "r");
    if (NULL == fp) {
        printf("fopen %s failure.\n", _IPV6_CUSTOM_FILE);
            fp = fopen(_IPV6_RESOURCE_FILE, "r");
            if (NULL == fp) {
                    printf("fopen %s failure.\n", _IPV6_RESOURCE_FILE);
                    return NULL;
            }

    }
    while (EOF != fscanf(fp, "%4s%4s%4s%4s%4s%4s%4s%4s %02x %02x %02x %02x %20s\n",
        address[0], address[1], address[2], address[3],
        address[4], address[5], address[6], address[7],
        &if_idx, &plen, &scope, &dad_status, iface))
    {
        int i;
        for (i = 0; i < 8; ++i) {
            sscanf(address[i], "%4x", &tmp);
            ipv6addr.s6_addr16[i] = htons((unsigned short int)tmp);
        }
        if (!(IN6_IS_ADDR_LOOPBACK(ipv6addr.s6_addr32)
            || IN6_IS_ADDR_UNSPECIFIED(ipv6addr.s6_addr32)
            || IN6_IS_ADDR_LINKLOCAL(ipv6addr.s6_addr32))){
            inet_ntop(AF_INET6, &ipv6addr, txt_ipv6_address, INET6_ADDRSTRLEN);
            //break;
        }
    }
    fclose(fp);
    printf( txt_ipv6_address );

    return 0;
}