sock_set_ipv4_ucast_ttl
int sock_set_ipv4_ucast_ttl(int fd, int);
if (sock_set_ipv4_ucast_ttl(fd, ttl) == -1)
sock_set_ipv4_ucast_ttl(fd, -1);
if (sock_set_ipv4_ucast_ttl(fd, 255) == -1) {