TCP_DROP_SYNFIN kernel option side effects?!

[h bagade]

Hi all,

I need to add this option to kernel in order to defeating Nmap
OS-Fingerprinting. My system is running as Web Server and  also it is the
gateway on the network.
I want to know if setting this option has any side effects on other parts
of the system? Is there any situation that SYN and FIN bits are set both in
TCP packets? Is it a normal situation?

Any helps or comments are really appreciated.