IP: ESP transformation

modulename: esp4.ko

configname: CONFIG_INET_ESP

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>IP: ESP transformation
In linux kernel since version 2.6.12  
Support for IPsec ESP (Encapsulating Security Payload).

ESP can be used with various encryption and authentication algorithms.
Besides enabling ESP support itself, this option enables the generic
implementations of the algorithms that RFC 8221 lists as MUST be
implemented. If you need any other algorithms, you'll need to enable
them in the crypto API. You should also enable accelerated
implementations of any needed algorithms when available.

If unsure, say Y.

source code: