Add triggering of F1 UE Context release command

-Add also a temporary artificial trigger just to be able to test with OAI UE
-Comment out most of the part of the UE context release command handler function at the DU in order to separate properly the RRC from F1AP functionality later.

openair2/F1AP/f1ap_cu_ue_context_management.c

@@ -907,12 +907,14 @@ int CU_send_UE_CONTEXT_RELEASE_COMMAND(instance_t instance,
 
   /* optional */
   /* c4. RRCContainer */
-  asn1cSequenceAdd(out->protocolIEs.list, F1AP_UEContextReleaseCommandIEs_t, ie4);
-  ie4->id                             = F1AP_ProtocolIE_ID_id_RRCContainer;
-  ie4->criticality                    = F1AP_Criticality_ignore;
-  ie4->value.present                  = F1AP_UEContextReleaseCommandIEs__value_PR_RRCContainer;
-  OCTET_STRING_fromBuf(&ie4->value.choice.RRCContainer, (const char *)cmd->rrc_container,
+  if(cmd->rrc_container!=NULL){
+    asn1cSequenceAdd(out->protocolIEs.list, F1AP_UEContextReleaseCommandIEs_t, ie4);
+    ie4->id                             = F1AP_ProtocolIE_ID_id_RRCContainer;
+    ie4->criticality                    = F1AP_Criticality_ignore;
+    ie4->value.present                  = F1AP_UEContextReleaseCommandIEs__value_PR_RRCContainer;
+    OCTET_STRING_fromBuf(&ie4->value.choice.RRCContainer, (const char *)cmd->rrc_container,
                        cmd->rrc_container_length);
+  }
 
   /* encode */
   if (f1ap_encode_pdu(&pdu, &buffer, &len) < 0) {

openair2/F1AP/f1ap_du_ue_context_management.c

@@ -683,14 +683,14 @@ int DU_handle_UE_CONTEXT_RELEASE_COMMAND(instance_t       instance,
   protocol_ctxt_t ctxt;
   DevAssert(pdu);
   container = &pdu->choice.initiatingMessage->value.choice.UEContextReleaseCommand;
-  /* GNB_CU_UE_F1AP_ID */
+  // GNB_CU_UE_F1AP_ID 
   F1AP_FIND_PROTOCOLIE_BY_ID(F1AP_UEContextReleaseCommandIEs_t, ie, container,
                              F1AP_ProtocolIE_ID_id_gNB_CU_UE_F1AP_ID, true);
   ctxt.rnti = f1ap_get_rnti_by_cu_id(DUtype, instance, ie->value.choice.GNB_CU_UE_F1AP_ID);
   ctxt.instance = instance;
   ctxt.module_id = instance;
   ctxt.enb_flag  = 1;
-  /* GNB_DU_UE_F1AP_ID */
+  // GNB_DU_UE_F1AP_ID 
   F1AP_FIND_PROTOCOLIE_BY_ID(F1AP_UEContextReleaseCommandIEs_t, ie, container,
                              F1AP_ProtocolIE_ID_id_gNB_DU_UE_F1AP_ID, true);
   const rnti_t rnti = f1ap_get_rnti_by_du_id(DUtype, instance,
@@ -700,7 +700,7 @@ int DU_handle_UE_CONTEXT_RELEASE_COMMAND(instance_t       instance,
               rnti, ctxt.rnti);
   int UE_out_of_sync = 0;
 
-  if (RC.nrrrc && RC.nrrrc[instance]->node_type == ngran_gNB_DU) {
+  /*if (RC.nrrrc && RC.nrrrc[instance]->node_type == ngran_gNB_DU) {
     for (int n = 0; n < MAX_MOBILES_PER_GNB; ++n) {
       if (RC.nrmac[instance]->UE_info.active[n] == TRUE
           && rnti == RC.nrmac[instance]->UE_info.rnti[n]) {
@@ -718,13 +718,13 @@ int DU_handle_UE_CONTEXT_RELEASE_COMMAND(instance_t       instance,
     }
   }
 
-  /* We don't need the Cause */
-  /* Optional RRC Container: if present, send to UE */
+  // We don't need the Cause 
+  // Optional RRC Container: if present, send to UE 
   F1AP_FIND_PROTOCOLIE_BY_ID(F1AP_UEContextReleaseCommandIEs_t, ie, container,
                              F1AP_ProtocolIE_ID_id_RRCContainer, false);
 
   if (ie && !UE_out_of_sync) {
-    /* RRC message and UE is reachable, send message */
+    // RRC message and UE is reachable, send message 
     const sdu_size_t sdu_len = ie->value.choice.RRCContainer.size;
     mem_block_t *pdu_p = NULL;
     pdu_p = get_free_mem_block(sdu_len, __func__);
@@ -775,8 +775,8 @@ int DU_handle_UE_CONTEXT_RELEASE_COMMAND(instance_t       instance,
     ue_context_p = rrc_eNB_get_ue_context(RC.rrc[ctxt.instance], ctxt.rnti);
 
     if (ue_context_p && !UE_out_of_sync) {
-      /* UE exists and is in sync so we start a timer before releasing the
-       * connection */
+      // UE exists and is in sync so we start a timer before releasing the
+      //  connection 
       pthread_mutex_lock(&rrc_release_freelist);
 
       for (uint16_t release_num = 0; release_num < NUMBER_OF_UE_MAX; release_num++) {
@@ -800,18 +800,18 @@ int DU_handle_UE_CONTEXT_RELEASE_COMMAND(instance_t       instance,
       pthread_mutex_unlock(&rrc_release_freelist);
       ue_context_p->ue_context.ue_release_timer_s1 = 0;
     } else if (ue_context_p && UE_out_of_sync) {
-      /* UE exists and is out of sync, drop the connection */
+      // UE exists and is out of sync, drop the connection 
       mac_eNB_rrc_ul_failure(instance, 0, 0, 0, rnti);
     } else {
       LOG_E(F1AP, "no ue_context for RNTI %x, acknowledging release\n", rnti);
     }
 
-    /* TODO send this once the connection has really been released */
+    // TODO send this once the connection has really been released 
     f1ap_ue_context_release_cplt_t cplt;
     cplt.rnti = ctxt.rnti;
     DU_send_UE_CONTEXT_RELEASE_COMPLETE(instance, &cplt);
     return 0;
-  }
+  }*/
 }
 int DU_send_UE_CONTEXT_RELEASE_COMPLETE(instance_t instance,
                                         f1ap_ue_context_release_cplt_t *cplt) {

openair2/RRC/NR/rrc_gNB.c

@@ -1515,6 +1515,18 @@ rrc_gNB_process_RRCReconfigurationComplete(
     free(DRB_Release_configList2);
     ue_context_pP->ue_context.DRB_Release_configList2[xid] = NULL;
   }
+  //Temporarily trigger artificially UE context release for the CU case just to be able to test it with OAI UE. To be removed later
+  if(0){
+    if(NODE_IS_CU(RC.nrrrc[ctxt_pP->instance]->node_type)){
+      MessageDef *message_p;
+      message_p = itti_alloc_new_message (TASK_RRC_GNB, 0, F1AP_UE_CONTEXT_RELEASE_CMD);
+      f1ap_ue_context_release_cmd_t *rel_cmd=&F1AP_UE_CONTEXT_RELEASE_CMD (message_p);
+      rel_cmd->rnti = ctxt_pP->rnti;
+      rel_cmd->cause = F1AP_CAUSE_RADIO_NETWORK;
+      rel_cmd->cause_value = 10; // 10 = F1AP_CauseRadioNetwork_normal_release
+      itti_send_msg_to_task(TASK_CU_F1, ctxt_pP->module_id, message_p);
+    }
+  }
 }
 
 //-----------------------------------------------------------------------------
@@ -3925,15 +3937,27 @@ void nr_rrc_subframe_process(protocol_ctxt_t *const ctxt_pP, const int CC_id) {
 
         // Remove here the MAC and RRC context when RRC is not connected or gNB is not connected to CN5G
         if(ue_context_p->ue_context.StatusRrc < NR_RRC_CONNECTED || ue_context_p->ue_context.gNB_ue_ngap_id == 0) {
-          mac_remove_nr_ue(ctxt_pP->module_id, ctxt_pP->rnti);
-          rrc_rlc_remove_ue(ctxt_pP);
-          pdcp_remove_UE(ctxt_pP);
-
-          /* remove RRC UE Context */
-          ue_context_p = rrc_gNB_get_ue_context(RC.nrrrc[ctxt_pP->module_id], ctxt_pP->rnti);
-          if (ue_context_p) {
-            rrc_gNB_remove_ue_context(ctxt_pP, RC.nrrrc[ctxt_pP->module_id], ue_context_p);
-            LOG_I(NR_RRC, "remove UE %x \n", ctxt_pP->rnti);
+          if(!NODE_IS_CU(RC.nrrrc[ctxt_pP->instance]->node_type)){
+            mac_remove_nr_ue(ctxt_pP->module_id, ctxt_pP->rnti);
+            rrc_rlc_remove_ue(ctxt_pP);
+            pdcp_remove_UE(ctxt_pP);
+
+            /* remove RRC UE Context */
+            ue_context_p = rrc_gNB_get_ue_context(RC.nrrrc[ctxt_pP->module_id], ctxt_pP->rnti);
+            if (ue_context_p) {
+              rrc_gNB_remove_ue_context(ctxt_pP, RC.nrrrc[ctxt_pP->module_id], ue_context_p);
+              LOG_I(NR_RRC, "remove UE %x \n", ctxt_pP->rnti);
+            }
+          }
+          // In case of CU trigger UE context release command towards the DU
+          else{
+            MessageDef *message_p;
+            message_p = itti_alloc_new_message (TASK_RRC_GNB, 0, F1AP_UE_CONTEXT_RELEASE_CMD);
+            f1ap_ue_context_release_cmd_t *rel_cmd=&F1AP_UE_CONTEXT_RELEASE_CMD (message_p);
+            rel_cmd->rnti = ctxt_pP->rnti;
+            rel_cmd->cause = F1AP_CAUSE_RADIO_NETWORK;
+            rel_cmd->cause_value = 10; // 10 = F1AP_CauseRadioNetwork_normal_release
+            itti_send_msg_to_task(TASK_CU_F1, ctxt_pP->module_id, message_p);
           }
         }