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>
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 1346ee0..7cae236 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -507,6 +507,8 @@
 	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;