RRC (refactor): extract target context application into dedicated function

Refactor handover target context application logic into a reusable
function nr_rrc_apply_target_context() that updates both F1AP
associations (secondary UE and DU association) and RNTI from the
target handover context.

And apply to rrc_CU_process_ue_context_modification_response()

openair2/RRC/NR/rrc_gNB.c

@@ -2579,17 +2579,9 @@ static void rrc_CU_process_ue_context_modification_response(MessageDef *msg_p, i
   // nothing is to be done, we wait for confirmation to release the UE in the
   // CU/DU)
   if (UE->ho_context && UE->ho_context->target && UE->ho_context->source) {
-    nr_ho_target_cu_t *target_ctx = UE->ho_context->target;
-    f1_ue_data_t ue_data = cu_get_f1_ue_data(UE->rrc_ue_id);
-    ue_data.secondary_ue = target_ctx->du_ue_id;
-    ue_data.du_assoc_id = target_ctx->du->assoc_id;
-    bool success = cu_update_f1_ue_data(UE->rrc_ue_id, &ue_data);
-    DevAssert(success);
-    LOG_I(NR_RRC, "UE %d handover: update RNTI from %04x to %04x\n", UE->rrc_ue_id, UE->rnti, target_ctx->new_rnti);
     nr_ho_source_cu_t *source_ctx = UE->ho_context->source;
     DevAssert(source_ctx->old_rnti == UE->rnti);
-    UE->rnti = target_ctx->new_rnti;
-    UE->nr_cellid = target_ctx->du->setup_req->cell[0].info.nr_cellid;
+    nr_rrc_apply_target_context(UE);
   }
 }
 

openair2/RRC/NR/rrc_gNB_mobility.c

@@ -63,6 +63,34 @@ static void free_ho_ctx(nr_handover_context_t *ho_ctx)
   free(ho_ctx);
 }
 
+/** @brief Apply target handover context: update F1AP associations and RNTI */
+void nr_rrc_apply_target_context(gNB_RRC_UE_t *UE)
+{
+  DevAssert(UE->ho_context);
+  DevAssert(UE->ho_context->target);
+  nr_ho_target_cu_t *target_ctx = UE->ho_context->target;
+  f1_ue_data_t ue_data = cu_get_f1_ue_data(UE->rrc_ue_id);
+  LOG_I(NR_RRC,
+        "UE %d: update CU F1AP Context DU UE ID %u => %u and RNTI %04x => %04x\n",
+        UE->rrc_ue_id,
+        ue_data.secondary_ue,
+        target_ctx->du_ue_id,
+        UE->rnti,
+        target_ctx->new_rnti);
+
+  /* update F1 data: secondary UE association and DU association */
+  ue_data.secondary_ue = target_ctx->du_ue_id;
+  ue_data.du_assoc_id = target_ctx->du->assoc_id;
+  bool success = cu_update_f1_ue_data(UE->rrc_ue_id, &ue_data);
+  DevAssert(success);
+
+  /* update UE RNTI */
+  UE->rnti = target_ctx->new_rnti;
+
+  /* update UE NR cell ID */
+  UE->nr_cellid = target_ctx->du->setup_req->cell[0].info.nr_cellid;
+}
+
 /** @brief Fill DRB to Be Setup List in F1 UE Context Setup Request (optional list)
  * @return 0 if list is empty, list size otherwise */
 static int fill_drb_to_be_setup(const gNB_RRC_INST *rrc, gNB_RRC_UE_t *ue, f1ap_drb_to_setup_t drbs[MAX_DRBS_PER_UE])

openair2/RRC/NR/rrc_gNB_mobility.h

@@ -110,4 +110,6 @@ void nr_rrc_trigger_n2_ho_target(gNB_RRC_INST *rrc, gNB_RRC_UE_t *ue);
 
 byte_array_t *get_meas_timing_config(const NR_MeasurementTimingConfiguration_t *mtc, const NR_MeasConfig_t *measConfig);
 
+void nr_rrc_apply_target_context(gNB_RRC_UE_t *UE);
+
 #endif /* RRC_GNB_MOBILITY_H_ */