cu_cp,du_processor,rrc: Get release context from rrc for ue context release

Author: FabianEckermann

include/srsran/cu_cp/du_processor.h

@@ -198,9 +198,9 @@ class du_processor_rrc_ue_control_message_notifier
   /// \returns The result of the rrc reconfiguration.
   virtual async_task<bool> on_rrc_reconfiguration_request(const cu_cp_rrc_reconfiguration_procedure_request& msg) = 0;
 
-  /// \brief Notify the RRC UE to Release an UE.
-  /// \returns The location info of the UE.
-  virtual cu_cp_user_location_info_nr on_rrc_ue_release() = 0;
+  /// \brief Get the RRC UE release context.
+  /// \returns The release context of the UE.
+  virtual rrc_ue_release_context get_rrc_ue_release_context() = 0;
 };
 
 /// Handler for an NGAP entity to communicate with the DU processor

include/srsran/rrc/rrc_ue.h

@@ -258,6 +258,11 @@ class rrc_ue_dl_nas_message_handler
   virtual void handle_dl_nas_transport_message(const dl_nas_transport_message& msg) = 0;
 };
 
+struct rrc_ue_release_context {
+  cu_cp_user_location_info_nr user_location_info;
+  byte_buffer                 rrc_release_pdu;
+};
+
 /// Handle control messages.
 class rrc_ue_control_message_handler
 {
@@ -274,9 +279,9 @@ class rrc_ue_control_message_handler
   virtual async_task<bool>
   handle_rrc_ue_capability_transfer_request(const cu_cp_ue_capability_transfer_request& msg) = 0;
 
-  /// \brief Handle an RRC UE Release.
-  /// \returns The location info of the UE.
-  virtual cu_cp_user_location_info_nr handle_rrc_ue_release() = 0;
+  /// \brief Get the RRC UE release context.
+  /// \returns The release context of the UE.
+  virtual rrc_ue_release_context get_rrc_ue_release_context() = 0;
 };
 
 /// Handler to initialize the security context from NGAP.

lib/cu_cp/adapters/du_processor_adapters.h

@@ -205,10 +205,10 @@ class du_processor_rrc_ue_adapter : public du_processor_rrc_ue_control_message_n
     return rrc_ue_handler->handle_rrc_reconfiguration_request(msg);
   }
 
-  virtual cu_cp_user_location_info_nr on_rrc_ue_release() override
+  virtual rrc_ue_release_context get_rrc_ue_release_context() override
   {
     srsran_assert(rrc_ue_handler != nullptr, "RRC UE handler must not be nullptr");
-    return rrc_ue_handler->handle_rrc_ue_release();
+    return rrc_ue_handler->get_rrc_ue_release_context();
   }
 
 private:

lib/cu_cp/du_processor_impl.cpp

@@ -455,8 +455,10 @@ du_processor_impl::handle_new_ue_context_release_command(const cu_cp_ue_context_
   release_complete.pdu_session_res_list_cxt_rel_cpl =
       rrc->find_ue(cmd.ue_index)->get_rrc_ue_up_resource_manager().get_pdu_sessions();
 
-  // Call RRC UE notifier to release the UE and add the location info to the UE context release complete message
-  release_complete.user_location_info = ue->get_rrc_ue_notifier().on_rrc_ue_release();
+  // Call RRC UE notifier to get the release context of the UE and add the location info to the UE context release
+  // complete message
+  rrc_ue_release_context release_context = ue->get_rrc_ue_notifier().get_rrc_ue_release_context();
+  release_complete.user_location_info    = release_context.user_location_info;
 
   handle_ue_context_release_command(cmd);
 

lib/rrc/ue/rrc_ue_impl.h

@@ -66,7 +66,7 @@ class rrc_ue_impl final : public rrc_ue_interface
   // rrc_ue_control_message_handler
   async_task<bool> handle_rrc_reconfiguration_request(const cu_cp_rrc_reconfiguration_procedure_request& msg) override;
   async_task<bool> handle_rrc_ue_capability_transfer_request(const cu_cp_ue_capability_transfer_request& msg) override;
-  cu_cp_user_location_info_nr handle_rrc_ue_release() override;
+  rrc_ue_release_context get_rrc_ue_release_context() override;
 
   // rrc_ue_context_handler
   rrc_reestablishment_ue_context_t get_context() override;

lib/rrc/ue/rrc_ue_message_handlers.cpp

@@ -289,20 +289,21 @@ async_task<bool> rrc_ue_impl::handle_rrc_ue_capability_transfer_request(const cu
   return launch_async<rrc_ue_capability_transfer_procedure>(context, *this, *event_mng, logger);
 }
 
-cu_cp_user_location_info_nr rrc_ue_impl::handle_rrc_ue_release()
+rrc_ue_release_context rrc_ue_impl::get_rrc_ue_release_context()
 {
   // prepare location info to return
-  cu_cp_user_location_info_nr user_location_info;
-  user_location_info.nr_cgi      = context.cell.cgi;
-  user_location_info.tai.plmn_id = context.cell.cgi.plmn_hex;
-  user_location_info.tai.tac     = context.cell.tac;
+  rrc_ue_release_context release_context;
+  release_context.user_location_info.nr_cgi      = context.cell.cgi;
+  release_context.user_location_info.tai.plmn_id = context.cell.cgi.plmn_hex;
+  release_context.user_location_info.tai.tac     = context.cell.tac;
 
   dl_dcch_msg_s dl_dcch_msg;
   dl_dcch_msg.msg.set_c1().set_rrc_release().crit_exts.set_rrc_release();
 
-  send_dl_dcch(srb_id_t::srb1, dl_dcch_msg);
+  // pack DL CCCH msg
+  release_context.rrc_release_pdu = pack_into_pdu(dl_dcch_msg);
 
-  return user_location_info;
+  return release_context;
 }
 
 rrc_reestablishment_ue_context_t rrc_ue_impl::get_context()

tests/unittests/cu_cp/test_helpers.h

@@ -383,12 +383,12 @@ struct dummy_du_processor_rrc_ue_control_message_notifier : public du_processor_
     });
   }
 
-  cu_cp_user_location_info_nr on_rrc_ue_release() override
+  rrc_ue_release_context get_rrc_ue_release_context() override
   {
-    logger.info("Received a new RRC UE Release request");
-    cu_cp_user_location_info_nr user_location_info;
+    logger.info("Received a new request to get RRC UE release context");
+    rrc_ue_release_context release_context;
     // TODO: Add values
-    return user_location_info;
+    return release_context;
   }
 
   optional<cu_cp_radio_bearer_config> last_radio_bearer_cfg;