CONFIG_XFRM_ESPINTCP (not configurable)

modulename: espintcp.ko

configname: CONFIG_XFRM_ESPINTCP

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>XFRM_ESPINTCP
In linux kernel since version 5.1 (release Date: 2019-05-05)  
source code:
net/xfrm/espintcp.c