Support for Transformation(XFRM) user configuration interface like IPsec used by native Linux tools. If unsure, say Y.
Support sub policy for developers. By using sub policy with main one, two policies can be applied to the same packet at once. Policy which lives shorter time in kernel should be a sub. If unsure, say N.
A feature to update locator(s) of a given IPsec security association dynamically. This feature is required, for instance, in a Mobile IPv6 environment with IPsec configuration where mobile nodes change their attachment point to the Internet. If unsure, say N.
This statistics is not a SNMP/MIB specification but shows statistics about transformation error (or almost error) factor at packet processing for developer. If unsure, say N.
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.
Add a PF_KEY MIGRATE message to PF_KEYv2 socket family. The PF_KEY MIGRATE message is used to dynamically update locator(s) of a given IPsec security association. This feature is required, for instance, in a Mobile IPv6 environment with IPsec configuration where mobile nodes change their attachment point to the Internet. Detail information can be found in the internet-draft <draft-sugimoto-mip6-pfkey-migrate>. If unsure, say N.