cu_cp,rrc: add helper to get rrc reject pdu when rrc ue creation fails

Author: FabianEckermann

include/srsran/rrc/rrc_du.h

@@ -51,6 +51,9 @@ class rrc_du_ue_repository
   rrc_du_ue_repository()          = default;
   virtual ~rrc_du_ue_repository() = default;
 
+  /// \brief Get the RRC Reject message to send to the UE.
+  virtual byte_buffer get_rrc_reject() = 0;
+
   /// Creates a new RRC UE object and returns a handle to it.
   virtual rrc_ue_interface* add_ue(const rrc_ue_creation_message& msg) = 0;
 

lib/rrc/rrc_du_impl.cpp

@@ -9,9 +9,10 @@
  */
 
 #include "rrc_du_impl.h"
-#include "../ran/gnb_format.h"
 #include "ue/rrc_measurement_types_asn1_converters.h"
+#include "ue/rrc_ue_helpers.h"
 #include "srsran/asn1/rrc_nr/cell_group_config.h"
+#include "srsran/asn1/rrc_nr/dl_ccch_msg.h"
 #include "srsran/cu_cp/cu_cp_types.h"
 
 using namespace srsran;
@@ -95,6 +96,14 @@ bool rrc_du_impl::handle_served_cell_list(const std::vector<cu_cp_du_served_cell
   return true;
 }
 
+byte_buffer rrc_du_impl::get_rrc_reject()
+{
+  // pack RRC Reconfig
+  dl_ccch_msg_s dl_ccch_msg;
+  dl_ccch_msg.msg.set_c1().set_rrc_reject().crit_exts.set_rrc_reject();
+  return pack_into_pdu(dl_ccch_msg, "RRCReject");
+}
+
 rrc_ue_interface* rrc_du_impl::add_ue(const rrc_ue_creation_message& msg)
 {
   // If the DU to CU container is missing, assume the DU can't serve the UE, so the CU-CP should reject the UE, see

lib/rrc/rrc_du_impl.h

@@ -34,6 +34,7 @@ class rrc_du_impl : public rrc_du_interface
   bool handle_served_cell_list(const std::vector<cu_cp_du_served_cells_item>& served_cell_list) override;
 
   // rrc_du_ue_repository
+  byte_buffer       get_rrc_reject() override;
   rrc_ue_interface* add_ue(const rrc_ue_creation_message& msg) override;
   void              release_ues() override;