[XFRM] STATE: Common receive function for route optimization extension headers.

XFRM_STATE_WILDRECV flag is introduced; the last resort state is set
it and receives packet which is not route optimized but uses such
extension headers i.e. Mobile IPv6 signaling (binding update and
acknowledgement).  A node enabled Mobile IPv6 adds the state.

Based on MIPL2 kernel patch.

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>
diff --git a/include/linux/xfrm.h b/include/linux/xfrm.h
index 66343d3..a7c9e4c 100644
--- a/include/linux/xfrm.h
+++ b/include/linux/xfrm.h
@@ -256,6 +256,7 @@
 #define XFRM_STATE_NOECN	1
 #define XFRM_STATE_DECAP_DSCP	2
 #define XFRM_STATE_NOPMTUDISC	4
+#define XFRM_STATE_WILDRECV	8
 };
 
 struct xfrm_usersa_id {