[IPSEC] xfrm: Abstract out encapsulation modes

This patch adds the structure xfrm_mode.  It is meant to represent
the operations carried out by transport/tunnel modes.

By doing this we allow additional encapsulation modes to be added
without clogging up the xfrm_input/xfrm_output paths.

Candidate modes include 4-to-6 tunnel mode, 6-to-4 tunnel mode, and
BEET modes.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index ed7c974..ed5bb34 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -20,6 +20,8 @@
 #include <net/ip6_fib.h>
 
 #define XFRM_ALIGN8(len)	(((len) + 7) & ~7)
+#define MODULE_ALIAS_XFRM_MODE(family, encap) \
+	MODULE_ALIAS("xfrm-mode-" __stringify(family) "-" __stringify(encap))
 
 extern struct sock *xfrm_nl;
 extern u32 sysctl_xfrm_aevent_etime;
@@ -164,6 +166,7 @@
 	/* Reference to data common to all the instances of this
 	 * transformer. */
 	struct xfrm_type	*type;
+	struct xfrm_mode	*mode;
 
 	/* Security context */
 	struct xfrm_sec_ctx	*security;
@@ -205,6 +208,7 @@
 struct xfrm_policy_afinfo {
 	unsigned short		family;
 	struct xfrm_type	*type_map[256];
+	struct xfrm_mode	*mode_map[XFRM_MODE_MAX];
 	struct dst_ops		*dst_ops;
 	void			(*garbage_collect)(void);
 	int			(*dst_lookup)(struct xfrm_dst **dst, struct flowi *fl);
@@ -267,6 +271,19 @@
 extern struct xfrm_type *xfrm_get_type(u8 proto, unsigned short family);
 extern void xfrm_put_type(struct xfrm_type *type);
 
+struct xfrm_mode {
+	int (*input)(struct xfrm_state *x, struct sk_buff *skb);
+	int (*output)(struct sk_buff *skb);
+
+	struct module *owner;
+	unsigned int encap;
+};
+
+extern int xfrm_register_mode(struct xfrm_mode *mode, int family);
+extern int xfrm_unregister_mode(struct xfrm_mode *mode, int family);
+extern struct xfrm_mode *xfrm_get_mode(unsigned int encap, int family);
+extern void xfrm_put_mode(struct xfrm_mode *mode);
+
 struct xfrm_tmpl
 {
 /* id in template is interpreted as: