[PFKEYV2]: CONFIG_NET_KEY_MIGRATE option

Add CONFIG_NET_KEY_MIGRATE option which makes it possible for user
application to send or receive MIGRATE message to/from PF_KEY socket.
Signed-off-by: Shinta Sugimoto <shinta.sugimoto@ericsson.com>
Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/Kconfig

@@ -45,4 +45,19 @@ config NET_KEY
 
 	  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.