PF_KEY sockets

modulename: af_key.ko

configname: CONFIG_NET_KEY

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>PF_KEY sockets
In linux kernel since version 2.6.12  
PF_KEYv2 socket family, compatible to KAME ones.
They are required if you are going to use IPsec tools ported
from KAME.

Say Y unless you know what you are doing.

source code:

depends
CONFIG_NET

is selected by
CONFIG_NET_KEY_MIGRATE