Say Y unless you know what you are doing.
+config NET_KEY_MIGRATE
+ bool "PF_KEY MIGRATE (EXPERIMENTAL)"
+ depends on NET_KEY && EXPERIMENTAL
+ select XFRM_MIGRATE
+ ---help---
+ 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.