selinux: Add a cache for quicker retreival of PKey SIDs

It is likely that the SID for the same PKey will be requested many
times. To reduce the time to modify QPs and process MADs use a cache to
store PKey SIDs.

This code is heavily based on the "netif" and "netport" concept
originally developed by James Morris <jmorris@redhat.com> and Paul Moore
<paul@paul-moore.com> (see security/selinux/netif.c and
security/selinux/netport.c for more information)

Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
Acked-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/include/objsec.h

@@ -144,6 +144,12 @@ struct ib_security_struct {
 	u32 sid;        /* SID of the queue pair or MAD agent */
 };
 
+struct pkey_security_struct {
+	u64	subnet_prefix; /* Port subnet prefix */
+	u16	pkey;	/* PKey number */
+	u32	sid;	/* SID of pkey */
+};
+
 extern unsigned int selinux_checkreqprot;
 
 #endif /* _SELINUX_OBJSEC_H_ */