Allow DUs to reconnect to CU

Previous to this commit, the CU creates an F1 instance and initializes
GTP after a successful connection establishment, and tears the F1
instance down after the DU disconnects. This does not work when trying
to connect multiple DUs, or have them reconnect, as e.g., GTP
re-initialization fails (socket already bound).

This commit makes the CU F1 instance creation and GTP init at CU task
init (only once), and also frees the F1 instance only after the CU task
exits, which is at termination of the application, typically.

openair2/F1AP/f1ap_cu_task.c

@@ -53,20 +53,11 @@ static void cu_task_handle_sctp_association_ind(instance_t instance,
                                                 sctp_new_association_ind_t *sctp_new_association_ind,
                                                 eth_params_t *IPaddrs)
 {
-  createF1inst(instance, NULL, NULL);
   // save the assoc id
   f1ap_cudu_inst_t *f1ap_cu_data = getCxt(instance);
   f1ap_cu_data->assoc_id         = sctp_new_association_ind->assoc_id;
   f1ap_cu_data->sctp_in_streams  = sctp_new_association_ind->in_streams;
   f1ap_cu_data->sctp_out_streams = sctp_new_association_ind->out_streams;
-  if (RC.nrrrc[instance]->node_type != ngran_gNB_CUCP) {
-    getCxt(instance)->gtpInst = cu_task_create_gtpu_instance(IPaddrs);
-    AssertFatal(getCxt(instance)->gtpInst > 0, "Failed to create CU F1-U UDP listener");
-  } else
-    LOG_I(F1AP, "In F1AP connection, don't start GTP-U, as we have also E1AP\n");
-  // Fixme: fully inconsistent instances management
-  // dirty global var is a bad fix
-  CUuniqInstance=getCxt(instance)->gtpInst;
 }
 
 static void cu_task_handle_sctp_association_resp(instance_t instance, sctp_new_association_resp_t *sctp_new_association_resp) {
@@ -76,7 +67,6 @@ static void cu_task_handle_sctp_association_resp(instance_t instance, sctp_new_a
     f1ap_cudu_inst_t *f1ap_cu_data = getCxt(instance);
     AssertFatal(f1ap_cu_data != NULL, "illegal state: SCTP shutdown for non-existing F1AP endpoint\n");
     LOG_I(F1AP, "Received SCTP shutdown for assoc_id %d, removing endpoint\n", sctp_new_association_resp->assoc_id);
-    destroyF1inst(instance);
     /* inform RRC that the DU is gone */
     MessageDef *message_p = itti_alloc_new_message(TASK_CU_F1, 0, F1AP_LOST_CONNECTION);
     message_p->ittiMsgHeader.originInstance = sctp_new_association_resp->assoc_id;
@@ -139,7 +129,19 @@ void *F1AP_CU_task(void *arg) {
   // Hardcoded instance id!
   IPaddrs = &RC.nrrrc[0]->eth_params_s;
 
-  cu_task_send_sctp_init_req(0, IPaddrs->my_addr);
+  const int instance = 0;
+  createF1inst(instance, NULL, NULL);
+  cu_task_send_sctp_init_req(instance, IPaddrs->my_addr);
+
+  if (RC.nrrrc[instance]->node_type != ngran_gNB_CUCP) {
+    getCxt(instance)->gtpInst = cu_task_create_gtpu_instance(IPaddrs);
+    AssertFatal(getCxt(instance)->gtpInst > 0, "Failed to create CU F1-U UDP listener");
+  } else {
+    LOG_I(F1AP, "In F1AP connection, don't start GTP-U, as we have also E1AP\n");
+  }
+  // Fixme: fully inconsistent instances management
+  // dirty global var is a bad fix
+  CUuniqInstance=getCxt(instance)->gtpInst;
 
   while (1) {
     itti_receive_msg(TASK_CU_F1, &received_msg);
@@ -224,5 +226,7 @@ void *F1AP_CU_task(void *arg) {
     received_msg = NULL;
   } // while
 
+  destroyF1inst(instance);
+
   return NULL;
 }