calipso: Add a label cache.

This works in exactly the same way as the CIPSO label cache.
The idea is to allow the lsm to cache the result of a secattr
lookup so that it doesn't need to perform the lookup for
every skbuff.

It introduces two sysctl controls:
 calipso_cache_enable - enables/disables the cache.
 calipso_cache_bucket_size - sets the size of a cache bucket.

Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

net/netlabel/netlabel_calipso.h

@@ -144,5 +144,8 @@ int calipso_skbuff_setattr(struct sk_buff *skb,
 			   const struct calipso_doi *doi_def,
 			   const struct netlbl_lsm_secattr *secattr);
 int calipso_skbuff_delattr(struct sk_buff *skb);
+void calipso_cache_invalidate(void);
+int calipso_cache_add(const unsigned char *calipso_ptr,
+		      const struct netlbl_lsm_secattr *secattr);
 
 #endif