target/iscsi_target: Add NodeACL tags for initiator group support

Thanks for reviews, looking a lot better.

---- 8< ----

Initiator access config could be easier. The way other storage vendors
have addressed this is to support initiator groups: the admin adds
initiator WWNs to the group, and then LUN permissions can be granted for
the entire group at once.

Instead of changing ktarget's configfs interface, this patch keeps
the configfs interface per-initiator-wwn and just adds a 'tag' field
for each. This should be enough for user tools like targetcli to group
initiator ACLs and sync their configurations.

acl_tag is not used internally, but needs to be kept in configfs so that
all user tools can avoid dependencies on each other.

Code tested to work, although userspace pieces still to be implemented.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

include/target/target_core_base.h

@@ -507,6 +507,8 @@ struct se_node_acl {
 	bool			acl_stop:1;
 	u32			queue_depth;
 	u32			acl_index;
+#define MAX_ACL_TAG_SIZE 64
+	char			acl_tag[MAX_ACL_TAG_SIZE];
 	u64			num_cmds;
 	u64			read_bytes;
 	u64			write_bytes;

include/target/target_core_fabric.h

@@ -142,6 +142,8 @@ int	core_tpg_del_initiator_node_acl(struct se_portal_group *,
 		struct se_node_acl *, int);
 int	core_tpg_set_initiator_node_queue_depth(struct se_portal_group *,
 		unsigned char *, u32, int);
+int	core_tpg_set_initiator_node_tag(struct se_portal_group *,
+		struct se_node_acl *, const char *);
 int	core_tpg_register(struct target_core_fabric_ops *, struct se_wwn *,
 		struct se_portal_group *, void *, int);
 int	core_tpg_deregister(struct se_portal_group *);