syscall (SYS_clock_gettime, CLOCK_REALTIME, &ts);
nonce_lower = ts.tv_nsec;
nonce_upper = ts.tv_sec ^ clib_host_to_net_u32 (nonce_lower);
syscall (SYS_clock_gettime, CLOCK_REALTIME, &ts);
nonce_lower = ts.tv_nsec;
nonce_upper = ts.tv_sec ^ clib_host_to_net_u32 (nonce_lower);