The NETLINK_TYPE_META pseudo-type is actually equivalent to an empty
nested type. Drop it and define an empty type-system instead.
This also has the nice side-effect that m->container_type_system[0] is
never NULL (which has really nasty side-effects if you try to read
attributes).
Right now we store the maximum type-ID of a type-system. This prevents us
from creating empty type-systems. Store the "count" instead, which should
be treated as max+1.
Note that type_system_union_protocol_get_type_system() currently has a
nasty hack to treat empty type-systems as invalid. This might need some
modification later on as well.
Same as NLType, move NLTypeSystem into netlink-types.c and hide it from
the outside. Provide an accessor function for the 'max' field that is used
to allocate suitable array sizes.
Note that this will probably be removed later on, anyway. Once we support
bigger type-systems, it just seems impractical to allocate such big arrays
for each container entry. An RBTree would probably do just fine.
If we extend NLType to support arrays and further extended types, we
really want to avoid hard-coding the type-layout outside of
netlink-types.c. We already avoid accessing nl_type->type_system outside
of netlink-types.c, extend this to also avoid accessing any other fields.
Provide accessor functions for nl_type->type and nl_type->size and then
move NLType away from the type-system header.
With this in place, follow-up patches can safely turn "type_system" and
"type_system_union" into a real "union { }", and then add another type for
arrays.
Make sure we never access type->type_system or type->type_system_union
directly. This is an implementation detail of the type-system and we
should always use the accessors. Right now, they only exist for 2-level
accesses (type-system to type-system). This patch introduces the 1-level
accessors (type to type-system) and makes use of it.
This patch makes sure the proper assertions are in place, so we never
accidentally access sub-type-systems for non-nested/union types.
Note that this places hard-asserts on the accessors. This should be fine,
as we expect callers to only access sub type-systems if they *know*
they're dealing with nested types.
The NLA_ names are used to name real datatypes we extract out of netlink
messages. The kernel has an internal enum with the same names
(NLA_foobar), which is *NOT* binary compatible to our types. Furthermore,
we support a different set of types than the kernel (as we try to treat
some kernel peculiarities as our own types to simplify the API).
Rename NLA_ to NETLINK_TYPE_ to make clear that this is our own set of
types.
