getsockopt returns different IP_TOS value from the one set in setsockopt

I'm trying to use `setsockopt` to set `IPTOS` value to `IPTOS_THROUGHPUT`. The `setsockopt` call returned `0`. However the `getsockopt` shows the `IP_TOS` value is set to `1`, which is different from `IPTOS_THROUGHPUT` (`0x8`). Does anyone have idea what could have caused the mismatch of `IPTOS` value in the `setsockopt` and `getsockopt`? Here's the log output: Set DSCP Marking on socket 26 setsockopt on socket 26 to 8 returns 0 DSCP marking on socket 26 is 1, different from expected 8 Below is the code: ``` int iptos = IPTOS_THROUGHPUT; log(debug, 10, "Set DSCP Marking on socket %d\n", sockfd); retval = setsockopt(sockfd, IPPROTO_TCP, IP_TOS, &iptos, sizeof(iptos)); if (retval<0) { log(error, 99, "Failed to set DSCP marking on socket %d with error %d\n", sockfd, retval); } else { log(debug, 10, "setsockopt on socket %d to %d returns %d\n", sockfd, iptos, retval); int tos=0; socklen_t toslen=sizeof(tos); retval = getsockopt(sockfd, IPPROTO_TCP, IP_TOS, &tos, &toslen); if(retval<0) { log(warning, 99, "Failed to get DSCP marking on socket %d with error %d\n", sockfd, retval); }else { if( tos != iptos ) { log(warning, 99, "DSCP marking on socket %d is %d, different from expected %d\n", sockfd, tos, iptos); retval = 9999; } else { log(debug, 10, "Success: Set DSCP Marking on socket %d to %d\n", sockfd, iptos); retval = 0; } } } ```