sd-netlink: don't access type->type_system[_union] directly

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.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/libsystemd/sd-netlink/netlink-message.c b/src/libsystemd/sd-netlink/netlink-message.c
index 601124cc05..887327c9ae 100644
--- a/src/libsystemd/sd-netlink/netlink-message.c
+++ b/src/libsystemd/sd-netlink/netlink-message.c
@@ -85,7 +85,8 @@ int message_new(sd_netlink *rtnl, sd_netlink_message **ret, uint16_t type) {
 
         m->hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
 
-        m->container_type_system[0] = nl_type->type_system;
+        if (nl_type->type == NETLINK_TYPE_NESTED)
+                type_get_type_system(nl_type, &m->container_type_system[0]);
         m->hdr->nlmsg_len = size;
         m->hdr->nlmsg_type = type;
 
@@ -872,9 +873,9 @@ int sd_netlink_message_rewind(sd_netlink_message *m) {
                 return r;
 
         if (type->type == NETLINK_TYPE_NESTED) {
-                const NLTypeSystem *type_system = type->type_system;
+                const NLTypeSystem *type_system;
 
-                assert(type_system);
+                type_get_type_system(type, &type_system);
 
                 m->container_type_system[0] = type_system;