struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "eth0");

        ioctl(s, SIOCGIFINDEX, &ifr)
        setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE,  ifr.ifr_name, 16);
The length needs to be fixed to 16