Netfilter OSF over NFNETLINK interface

modulename: nfnetlink_osf.ko

configname: CONFIG_NETFILTER_NETLINK_OSF

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>Network packet filtering framework (Netfilter)
└─>Core Netfilter Configuration
└─>Netfilter OSF over NFNETLINK interface
In linux kernel since version 4.2 (release Date: 2015-08-30)  
If this option is enabled, the kernel will include support
for passive OS fingerprint via NFNETLINK.

source code: