2019-12-07 IPPROTO_RAW

    if (sendfd < 0) {
        if ((sendfd = socket (AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0) {
                perror ("socket() failed ");
                exit (EXIT_FAILURE);
        }

        if (setsockopt (sendfd, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on)) < 0) {
                perror ("setsockopt() failed to set IP_HDRINCL ");
                exit (EXIT_FAILURE);
        }
    }