Handling E1 connection loss on CU-CP

- it triggers the RRC callback after SCTP SHUTDOWN indication
- CUUP entity cleanup at RRC level

openair2/COMMON/e1ap_messages_def.h

@@ -22,6 +22,9 @@
 /* gNB_CUUP application layer -> E1AP messages */
 MESSAGE_DEF(E1AP_REGISTER_REQ, MESSAGE_PRIORITY_MED, e1ap_register_req_t, e1ap_register_req)
 
+/* E1AP -> RRC to inform about lost connection */
+MESSAGE_DEF(E1AP_LOST_CONNECTION, MESSAGE_PRIORITY_MED, e1ap_lost_connection_t, e1ap_lost_connection)
+
 /* E1AP Interface Management Messages */
 /* E1AP Setup Request: gNB-CU-UP -> gNB-CU-CP */
 MESSAGE_DEF(E1AP_SETUP_REQ  , MESSAGE_PRIORITY_MED , e1ap_setup_req_t , e1ap_setup_req)

openair2/COMMON/e1ap_messages_types.h

@@ -51,6 +51,7 @@
 #define E1AP_BEARER_CONTEXT_MODIFICATION_RESP(mSGpTR)     (mSGpTR)->ittiMsg.e1ap_bearer_modif_resp
 #define E1AP_BEARER_CONTEXT_RELEASE_CMD(mSGpTR)           (mSGpTR)->ittiMsg.e1ap_bearer_release_cmd
 #define E1AP_BEARER_CONTEXT_RELEASE_CPLT(mSGpTR)          (mSGpTR)->ittiMsg.e1ap_bearer_release_cplt
+#define E1AP_LOST_CONNECTION(mSGpTR)                      (mSGpTR)->ittiMsg.e1ap_lost_connection
 
 typedef net_ip_address_t e1ap_net_ip_address_t;
 
@@ -279,4 +280,10 @@ typedef struct e1ap_bearer_modif_resp_s {
   pdu_session_modif_t pduSessionMod[E1AP_MAX_NUM_PDU_SESSIONS];
 } e1ap_bearer_modif_resp_t;
 
+/* E1AP Connection Loss indication */
+typedef struct e1ap_lost_connection_t {
+  int dummy;
+} e1ap_lost_connection_t;
+
+
 #endif /* E1AP_MESSAGES_TYPES_H */

openair2/E1AP/e1ap.c

@@ -1774,6 +1774,16 @@ static void e1_task_handle_sctp_association_resp(E1_t type, instance_t instance,
 {
   DevAssert(sctp_new_association_resp != NULL);
   getCxtE1(instance)->sockState = sctp_new_association_resp->sctp_state;
+
+  if (sctp_new_association_resp->sctp_state == SCTP_STATE_SHUTDOWN) {
+    LOG_I(E1AP, "Received SCTP shutdown for assoc_id %d, removing CUCP endpoint\n", sctp_new_association_resp->assoc_id);
+    /* inform RRC that the CU-UP is gone */
+    MessageDef *message_p = itti_alloc_new_message(TASK_CUCP_E1, 0, E1AP_LOST_CONNECTION);
+    message_p->ittiMsgHeader.originInstance = sctp_new_association_resp->assoc_id;
+    itti_send_msg_to_task(TASK_RRC_GNB, instance, message_p);
+    return;
+  }
+
   if (sctp_new_association_resp->sctp_state != SCTP_STATE_ESTABLISHED) {
     LOG_W(E1AP, "Received unsuccessful result for SCTP association (%u), instance %ld, cnx_id %u\n",
           sctp_new_association_resp->sctp_state,

openair2/RRC/NR/nr_rrc_proto.h

@@ -129,6 +129,9 @@ sctp_assoc_t get_existing_cuup_for_ue(const gNB_RRC_INST *rrc, const gNB_RRC_UE_
 sctp_assoc_t get_new_cuup_for_ue(const gNB_RRC_INST *rrc, const gNB_RRC_UE_t *ue, int sst, int sd);
 int rrc_gNB_process_e1_setup_req(sctp_assoc_t assoc_id, e1ap_setup_req_t *req);
 
+/* Process indication of E1 connection loss on CU-CP */
+void rrc_gNB_process_e1_lost_connection(gNB_RRC_INST *rrc, e1ap_lost_connection_t *lc, sctp_assoc_t assoc_id);
+
 void bearer_context_setup_direct(e1ap_bearer_setup_req_t *req,
                                  instance_t instance);
 

openair2/RRC/NR/rrc_gNB.c

@@ -2476,6 +2476,10 @@ void *rrc_gnb_task(void *args_p) {
         rrc_gNB_process_e1_bearer_context_release_cplt(&E1AP_BEARER_CONTEXT_RELEASE_CPLT(msg_p));
         break;
 
+      case E1AP_LOST_CONNECTION: /* CUCP */
+        rrc_gNB_process_e1_lost_connection(RC.nrrrc[0], &E1AP_LOST_CONNECTION(msg_p), msg_p->ittiMsgHeader.originInstance);
+        break;
+
       case NGAP_PAGING_IND:
         rrc_gNB_process_PAGING_IND(msg_p, instance);
         break;

openair2/RRC/NR/rrc_gNB_cuup.c

@@ -189,3 +189,28 @@ int rrc_gNB_process_e1_setup_req(sctp_assoc_t assoc_id, e1ap_setup_req_t *req)
 
   return 0;
 }
+
+/**
+ * @brief RRC Processing of the indication of E1 connection loss on CU-CP
+*/
+void rrc_gNB_process_e1_lost_connection(gNB_RRC_INST *rrc, e1ap_lost_connection_t *lc, sctp_assoc_t assoc_id)
+{
+  LOG_I(NR_RRC, "Received E1 connection loss indication on RRC\n");
+  AssertFatal(assoc_id != 0, "illegal assoc_id == 0: should be -1 (monolithic) or >0 (split)\n");
+  nr_rrc_cuup_container_t e = {.assoc_id = assoc_id};
+  nr_rrc_cuup_container_t *cuup = RB_FIND(rrc_cuup_tree, &rrc->cuups, &e);
+  if (cuup == NULL) {
+    LOG_W(NR_RRC, "CU-UP for assoc_id %d not found!\n", assoc_id);
+    return;
+  }
+  if (cuup->setup_req != NULL) {
+    e1ap_setup_req_t *req = cuup->setup_req;
+    LOG_I(NR_RRC, "releasing CU-UP %s on assoc_id %d\n", req->gNB_cu_up_name, assoc_id);
+    free(cuup->setup_req);
+  }
+  nr_rrc_cuup_container_t *removed = RB_REMOVE(rrc_cuup_tree, &rrc->cuups, cuup);
+  // Free relevant CU-UP structures
+  free(cuup);
+  DevAssert(removed != NULL);
+  rrc->num_cuups--;
+}