[XFRM]: BEET mode

This patch introduces the BEET mode (Bound End-to-End Tunnel) with as
specified by the ietf draft at the following link:

http://www.ietf.org/internet-drafts/draft-nikander-esp-beet-mode-06.txt

The patch provides only single family support (i.e. inner family =
outer family).

Signed-off-by: Diego Beltrami <diego.beltrami@gmail.com>
Signed-off-by: Miika Komu     <miika@iki.fi>
Signed-off-by: Herbert Xu     <herbert@gondor.apana.org.au>
Signed-off-by: Abhinav Pathak <abhinav.pathak@hiit.fi>
Signed-off-by: Jeff Ahrenholz <ahrenholz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ipsec.h b/include/linux/ipsec.h
index d3c5276..d17a630 100644
--- a/include/linux/ipsec.h
+++ b/include/linux/ipsec.h
@@ -12,7 +12,8 @@
 enum {
 	IPSEC_MODE_ANY		= 0,	/* We do not support this for SA */
 	IPSEC_MODE_TRANSPORT	= 1,
-	IPSEC_MODE_TUNNEL	= 2
+	IPSEC_MODE_TUNNEL	= 2,
+	IPSEC_MODE_BEET         = 3
 };
 
 enum {