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.

3 files changed, 26 insertions, 13 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;
 
diff --git a/src/libsystemd/sd-netlink/netlink-types.c b/src/libsystemd/sd-netlink/netlink-types.c
index 72799da887..fe9e5f9826 100644
--- a/src/libsystemd/sd-netlink/netlink-types.c
+++ b/src/libsystemd/sd-netlink/netlink-types.c
@@ -460,6 +460,24 @@ const NLTypeSystem rtnl_type_system = {
         .types = rtnl_types,
 };
 
+void type_get_type_system(const NLType *nl_type, const NLTypeSystem **ret) {
+        assert(nl_type);
+        assert(ret);
+        assert(nl_type->type == NETLINK_TYPE_NESTED);
+        assert(nl_type->type_system);
+
+        *ret = nl_type->type_system;
+}
+
+void type_get_type_system_union(const NLType *nl_type, const NLTypeSystemUnion **ret) {
+        assert(nl_type);
+        assert(ret);
+        assert(nl_type->type == NETLINK_TYPE_UNION);
+        assert(nl_type->type_system_union);
+
+        *ret = nl_type->type_system_union;
+}
+
 int type_system_get_type(const NLTypeSystem *type_system, const NLType **ret, uint16_t type) {
         const NLType *nl_type;
 
@@ -493,11 +511,7 @@ int type_system_get_type_system(const NLTypeSystem *type_system, const NLTypeSys
         if (r < 0)
                 return r;
 
-        assert(nl_type->type == NETLINK_TYPE_NESTED);
-        assert(nl_type->type_system);
-
-        *ret = nl_type->type_system;
-
+        type_get_type_system(nl_type, ret);
         return 0;
 }
 
@@ -511,11 +525,7 @@ int type_system_get_type_system_union(const NLTypeSystem *type_system, const NLT
         if (r < 0)
                 return r;
 
-        assert(nl_type->type == NETLINK_TYPE_UNION);
-        assert(nl_type->type_system_union);
-
-        *ret = nl_type->type_system_union;
-
+        type_get_type_system_union(nl_type, ret);
         return 0;
 }
 
diff --git a/src/libsystemd/sd-netlink/netlink-types.h b/src/libsystemd/sd-netlink/netlink-types.h
index 1bb1b21da9..74a59bb7c2 100644
--- a/src/libsystemd/sd-netlink/netlink-types.h
+++ b/src/libsystemd/sd-netlink/netlink-types.h
@@ -65,6 +65,8 @@ struct NLType {
         const NLTypeSystemUnion *type_system_union;
 };
 
+void type_get_type_system(const NLType *type, const NLTypeSystem **ret);
+void type_get_type_system_union(const NLType *type, const NLTypeSystemUnion **ret);
 int type_system_get_type(const NLTypeSystem *type_system, const NLType **ret, uint16_t type);
 int type_system_get_type_system(const NLTypeSystem *type_system, const NLTypeSystem **ret, uint16_t type);
 int type_system_get_type_system_union(const NLTypeSystem *type_system, const NLTypeSystemUnion **ret, uint16_t type);