Implementation E1 Setup Failure (8.2.3.3 of 3GPP TS 38.463)

- CU-CP replying to the CU-UP with a Setup Failure message in case of unsuccessfull E1 Setup Request
- message is decoded by the CU-UP, and stops the process

doc/E1-design.md

@@ -17,17 +17,22 @@ connection setup only in split-mode, the rest is the same for CU):
 sequenceDiagram
   participant c as CUCP
   participant u as CUUP
-  u->c: SCTP connection setup (in split mode)
-  u->>c: E1AP Setup Request
-  Note over c: Execute rrc_gNB_process_e1_setup_req()
-  c->>u: E1AP Setup Response
 
+  Note over c,u: E1 Setup Procedure
+  u->c: SCTP connection setup (in split mode)
+  u->>c: E1 Setup Request
+  Note over c: Execute rrc_gNB_process_e1_setup_req()
+  c->>u: E1 Setup Response
+  c-->>u: E1 Setup Failure
+
+  Note over c,u: E1 Bearer Context Setup Procedure
   Note over c: Receives PDU session setup request from AMF
   c->>u: Bearer Context Setup Request
   Note over u: Execute e1_bearer_context_setup()<br/>Configure DRBs and create GTP Tunnels for F1-U and N3
   u->>c: Bearer Context Setup Response
   Note over c: Execute rrc_gNB_process_e1_setup_req()<br/>Sends F1-U UL TNL info to DU and receives DL TNL info
 
+  Note over c,u: E1 Bearer Context Modification (CU-CP Initiated) Procedure
   c->>u: Bearer Context Modification Request
   Note over u: Execute e1_bearer_context_modif()<br/>Updates GTP Tunnels with received info
   u->>c: Bearer Context Modification Response

openair2/COMMON/e1ap_messages_def.h

@@ -27,6 +27,8 @@ MESSAGE_DEF(E1AP_SETUP_REQ  , MESSAGE_PRIORITY_MED , e1ap_setup_req_t , e1ap_set
 
 /* E1AP -> eNB_DU or eNB_CU_RRC -> E1AP application layer messages */
 MESSAGE_DEF(E1AP_SETUP_RESP , MESSAGE_PRIORITY_MED, e1ap_setup_resp_t , e1ap_setup_resp)
+/* E1AP Setup Failure: gNB-CU-CP -> gNB-CU-UP */
+MESSAGE_DEF(E1AP_SETUP_FAIL, MESSAGE_PRIORITY_MED, e1ap_setup_fail_t, e1ap_setup_fail)
 
 MESSAGE_DEF(E1AP_BEARER_CONTEXT_SETUP_REQ , MESSAGE_PRIORITY_MED , e1ap_bearer_setup_req_t , e1ap_bearer_setup_req)
 

openair2/COMMON/e1ap_messages_types.h

@@ -44,6 +44,7 @@
 #define E1AP_REGISTER_REQ(mSGpTR)                         (mSGpTR)->ittiMsg.e1ap_register_req
 #define E1AP_SETUP_REQ(mSGpTR)                            (mSGpTR)->ittiMsg.e1ap_setup_req
 #define E1AP_SETUP_RESP(mSGpTR)                           (mSGpTR)->ittiMsg.e1ap_setup_resp
+#define E1AP_SETUP_FAIL(mSGpTR)                           (mSGpTR)->ittiMsg.e1ap_setup_fail
 #define E1AP_BEARER_CONTEXT_SETUP_REQ(mSGpTR)             (mSGpTR)->ittiMsg.e1ap_bearer_setup_req
 #define E1AP_BEARER_CONTEXT_SETUP_RESP(mSGpTR)            (mSGpTR)->ittiMsg.e1ap_bearer_setup_resp
 #define E1AP_BEARER_CONTEXT_MODIFICATION_REQ(mSGpTR)      (mSGpTR)->ittiMsg.e1ap_bearer_setup_req
@@ -94,6 +95,11 @@ typedef struct e1ap_setup_resp_s {
   long transac_id;
 } e1ap_setup_resp_t;
 
+/* E1AP Setup Failure */
+typedef struct e1ap_setup_fail_s {
+  long transac_id;
+} e1ap_setup_fail_t;
+
 typedef struct cell_group_s {
   long id;
 } cell_group_t;

openair2/E1AP/e1ap.c

@@ -257,25 +257,36 @@ void e1ap_send_SETUP_RESPONSE(sctp_assoc_t assoc_id, const e1ap_setup_resp_t *e1
   e1ap_encode_send(CPtype, assoc_id, &pdu, 0, __func__);
 }
 
+/**
+ * @brief E1 Setup Failure ASN1 messager builder
+ * @ref 9.2.1.6 GNB-CU-UP E1 SETUP FAILURE of 3GPP TS 38.463
+*/
 static void fill_SETUP_FAILURE(long transac_id, E1AP_E1AP_PDU_t *pdu)
 {
   /* Create */
   /* 0. pdu Type */
   pdu->present = E1AP_E1AP_PDU_PR_unsuccessfulOutcome;
   asn1cCalloc(pdu->choice.unsuccessfulOutcome, initMsg);
+  /* mandatory */
+  /**
+   * Message Type IE
+   * -  procedureCode (integer)
+   * -  Type of Message (choice)
+   * @ref clause 9.3.1.1 of 3GPP TS 38.463
+   */
   initMsg->procedureCode = E1AP_ProcedureCode_id_gNB_CU_UP_E1Setup;
   initMsg->criticality = E1AP_Criticality_reject;
   initMsg->value.present = E1AP_UnsuccessfulOutcome__value_PR_GNB_CU_UP_E1SetupFailure;
   E1AP_GNB_CU_UP_E1SetupFailure_t *out = &pdu->choice.unsuccessfulOutcome->value.choice.GNB_CU_UP_E1SetupFailure;
   /* mandatory */
-  /* c1. Transaction ID (integer value) */
+  /* c1. Transaction ID (integer value), clause 9.3.1.53 of 3GPP TS 38.463 */
   asn1cSequenceAdd(out->protocolIEs.list, E1AP_GNB_CU_UP_E1SetupFailureIEs_t, ieC1);
   ieC1->id                         = E1AP_ProtocolIE_ID_id_TransactionID;
   ieC1->criticality                = E1AP_Criticality_reject;
   ieC1->value.present              = E1AP_GNB_CU_UP_E1SetupFailureIEs__value_PR_TransactionID;
   ieC1->value.choice.TransactionID = transac_id;
   /* mandatory */
-  /* c2. cause (integer value) */
+  /* c2. cause (integer value), clause 9.3.1.2 of 3GPP TS 38.463 */
   asn1cSequenceAdd(out->protocolIEs.list, E1AP_GNB_CU_UP_E1SetupFailureIEs_t, ieC2);
   ieC2->id                         = E1AP_ProtocolIE_ID_id_Cause;
   ieC2->criticality                = E1AP_Criticality_ignore;
@@ -284,8 +295,12 @@ static void fill_SETUP_FAILURE(long transac_id, E1AP_E1AP_PDU_t *pdu)
   ieC2->value.choice.Cause.choice.radioNetwork = E1AP_CauseRadioNetwork_unspecified;
 }
 
+/**
+ * @brief E1 Setup Failure ASN1 messager encoder
+*/
 void e1apCUCP_send_SETUP_FAILURE(sctp_assoc_t assoc_id, long transac_id)
 {
+  LOG_D(E1AP, "CU-CP: Encoding E1AP Setup Failure for transac_id %ld...\n", transac_id);
   E1AP_E1AP_PDU_t pdu = {0};
   fill_SETUP_FAILURE(transac_id, &pdu);
   e1ap_encode_send(CPtype, assoc_id, &pdu, 0, __func__);
@@ -404,18 +419,31 @@ int e1apCUUP_handle_SETUP_RESPONSE(sctp_assoc_t assoc_id, e1ap_upcp_inst_t *inst
   return 0;
 }
 
+/**
+ * @brief E1 Setup Failure ASN1 messager decoder on CU-UP
+*/
 int e1apCUUP_handle_SETUP_FAILURE(sctp_assoc_t assoc_id, e1ap_upcp_inst_t *inst, const E1AP_E1AP_PDU_t *pdu)
 {
+  LOG_D(E1AP, "CU-UP: Decoding E1AP Setup Failure...\n");
   E1AP_GNB_CU_UP_E1SetupFailureIEs_t *ie;
   DevAssert(pdu != NULL);
   E1AP_GNB_CU_UP_E1SetupFailure_t *in = &pdu->choice.unsuccessfulOutcome->value.choice.GNB_CU_UP_E1SetupFailure;
   /* Transaction ID */
   F1AP_FIND_PROTOCOLIE_BY_ID(E1AP_GNB_CU_UP_E1SetupFailureIEs_t, ie, in,
                              E1AP_ProtocolIE_ID_id_TransactionID, true);
+  long transaction_id;
+  long old_transaction_id = inst->cuup.setupReq.transac_id;
+  transaction_id = ie->value.choice.TransactionID;
+  if (old_transaction_id != transaction_id)
+    LOG_E(E1AP, "Transaction IDs do not match %ld != %ld\n", old_transaction_id, transaction_id);
+  E1AP_free_transaction_identifier(transaction_id);
+
   /* Cause */
   F1AP_FIND_PROTOCOLIE_BY_ID(E1AP_GNB_CU_UP_E1SetupFailureIEs_t, ie, in,
                              E1AP_ProtocolIE_ID_id_Cause, true);
 
+  LOG_E(E1AP, "received E1 Setup Failure, please check the CU-CP output and the CU-UP parameters\n");
+  exit(1);
   return 0;
 }
 
@@ -1875,6 +1903,10 @@ void *E1AP_CUCP_task(void *arg) {
         e1ap_send_SETUP_RESPONSE(assoc_id, &E1AP_SETUP_RESP(msg));
         break;
 
+      case E1AP_SETUP_FAIL:
+        e1apCUCP_send_SETUP_FAILURE(assoc_id, E1AP_SETUP_FAIL(msg).transac_id);
+        break;
+
       case E1AP_BEARER_CONTEXT_SETUP_REQ:
         e1apCUCP_send_BEARER_CONTEXT_SETUP_REQUEST(assoc_id, &E1AP_BEARER_CONTEXT_SETUP_REQ(msg));
         break;

openair2/RRC/NR/rrc_gNB_cuup.c

@@ -122,6 +122,19 @@ sctp_assoc_t get_new_cuup_for_ue(const gNB_RRC_INST *rrc, const gNB_RRC_UE_t *ue
   return ue_data.e1_assoc_id;
 }
 
+static void e1ap_setup_failure(sctp_assoc_t assoc_id, uint64_t transac_id)
+{
+  MessageDef *msg_p = itti_alloc_new_message(TASK_RRC_GNB, 0, E1AP_SETUP_FAIL);
+  msg_p->ittiMsgHeader.originInstance = assoc_id;
+  e1ap_setup_fail_t *setup_fail = &E1AP_SETUP_FAIL(msg_p);
+  setup_fail->transac_id = transac_id;
+  LOG_I(NR_RRC, "Triggering E1AP Setup Failure for transac_id %ld (%ld), assoc_id %ld\n",
+        transac_id,
+        E1AP_SETUP_FAIL(msg_p).transac_id,
+        msg_p->ittiMsgHeader.originInstance);
+  itti_send_msg_to_task(TASK_CUCP_E1, 0 /*unused by callee*/, msg_p);
+}
+
 int rrc_gNB_process_e1_setup_req(sctp_assoc_t assoc_id, e1ap_setup_req_t *req)
 {
   AssertFatal(req->supported_plmns <= PLMN_LIST_MAX_SIZE, "Supported PLMNs is more than PLMN_LIST_MAX_SIZE\n");
@@ -138,6 +151,7 @@ int rrc_gNB_process_e1_setup_req(sctp_assoc_t assoc_id, e1ap_setup_req_t *req)
             c->setup_req->gNB_cu_up_id,
             c->setup_req->gNB_cu_up_name,
             c->assoc_id);
+      e1ap_setup_failure(assoc_id, req->transac_id);
       return -1;
     }
   }
@@ -151,11 +165,12 @@ int rrc_gNB_process_e1_setup_req(sctp_assoc_t assoc_id, e1ap_setup_req_t *req)
             id->mnc,
             rrc->configuration.mcc[i],
             rrc->configuration.mnc[i]);
+      e1ap_setup_failure(assoc_id, req->transac_id);
       return -1;
     }
   }
 
-  LOG_I(RRC, "Accepting new CU-UP ID %ld name %s (assoc_id %d)\n", req->gNB_cu_up_id, req->gNB_cu_up_name, assoc_id);
+  LOG_I(NR_RRC, "Accepting new CU-UP ID %ld name %s (assoc_id %d)\n", req->gNB_cu_up_id, req->gNB_cu_up_name, assoc_id);
   nr_rrc_cuup_container_t *cuup = malloc(sizeof(*cuup));
   AssertFatal(cuup, "out of memory\n");
   cuup->setup_req = malloc(sizeof(*cuup->setup_req));