Revert "Delay PDU session resource setup request if necessary"

This reverts commit 0f100a6e, which
introduced a hack to possibly wait with a PDU session setup at the RRC
in case a RRC UE capability transaction (requesting UE capabilities from
a UE) was ongoing. This happened, as we delayed the UE capabilities to
after the first RRC reconfiguration; in that case, certain UEs were
requesting the next PDU session, and if RRC did not delay the new PDU
session (as requested from the core), this procedure might occur while
UE capability enquiry was ongoing, leading to failures in these
transactions.

openair2/RRC/NR/nr_rrc_defs.h

@@ -323,9 +323,6 @@ typedef struct gNB_RRC_UE_s {
   /* Nas Pdu */
   ngap_pdu_t nas_pdu;
 
-  /* hack, see rrc_gNB_process_NGAP_PDUSESSION_SETUP_REQ() for more info */
-  int max_delays_pdu_session;
-
 } gNB_RRC_UE_t;
 
 typedef struct rrc_gNB_ue_context_s {

openair2/RRC/NR/rrc_gNB.c

@@ -2218,10 +2218,9 @@ void *rrc_gnb_task(void *args_p) {
         break;
 
       case TIMER_HAS_EXPIRED:
-        if (TIMER_HAS_EXPIRED(msg_p).timer_id == stats_timer_id)
-          write_rrc_stats(RC.nrrrc[0]);
-        else
-          itti_send_msg_to_task(TASK_RRC_GNB, 0, TIMER_HAS_EXPIRED(msg_p).arg); /* see rrc_gNB_process_NGAP_PDUSESSION_SETUP_REQ() */
+        /* only this one handled for now */
+        DevAssert(TIMER_HAS_EXPIRED(msg_p).timer_id == stats_timer_id);
+        write_rrc_stats(RC.nrrrc[0]);
         break;
 
       case F1AP_INITIAL_UL_RRC_MESSAGE:

openair2/RRC/NR/rrc_gNB_NGAP.c

@@ -815,28 +815,6 @@ rrc_gNB_send_NGAP_PDUSESSION_SETUP_RESP(
   return;
 }
 
-/* \brief checks if any transaction is ongoing for any xid of this UE */
-static bool transaction_ongoing(const gNB_RRC_UE_t *UE)
-{
-  for (int xid = 0; xid < 4; ++xid)
-    if (UE->xids[xid] != RRC_ACTION_NONE)
-      return true;
-  return false;
-}
-
-/* \brief delays the ongoing transaction (in msg_p) by setting a timer to wait
- * 10ms; upon expiry, delivers to RRC, which sends the message to itself */
-static void delay_transaction(MessageDef *msg_p, int wait_us)
-{
-  MessageDef *new = itti_alloc_new_message(TASK_RRC_GNB, 0, NGAP_PDUSESSION_SETUP_REQ);
-  ngap_pdusession_setup_req_t *n = &NGAP_PDUSESSION_SETUP_REQ(new);
-  *n = NGAP_PDUSESSION_SETUP_REQ(msg_p);
-
-  int instance = msg_p->ittiMsgHeader.originInstance;
-  long timer_id;
-  timer_setup(0, wait_us, TASK_RRC_GNB, instance, TIMER_ONE_SHOT, new, &timer_id);
-}
-
 //------------------------------------------------------------------------------
 void rrc_gNB_process_NGAP_PDUSESSION_SETUP_REQ(MessageDef *msg_p, instance_t instance)
 //------------------------------------------------------------------------------
@@ -862,24 +840,6 @@ void rrc_gNB_process_NGAP_PDUSESSION_SETUP_REQ(MessageDef *msg_p, instance_t ins
 
   AssertFatal(UE->rrc_ue_id == msg->gNB_ue_ngap_id, "logic bug\n");
   UE->amf_ue_ngap_id = msg->amf_ue_ngap_id;
-
-  /* This is a hack. We observed that with some UEs, PDU session requests might
-   * come in quick succession, faster than the RRC reconfiguration for the PDU
-   * session requests can be carried out (UE is doing reconfig, and second PDU
-   * session request arrives). We don't have currently the means to "queue up"
-   * these transactions, which would probably involve some rework of the RRC.
-   * To still allow these requests to come in and succeed, we below check and delay transactions
-   * for 10ms. However, to not accidentally end up in infinite loops, the
-   * maximum number is capped on a per-UE basis as indicated in variable
-   * max_delays_pdu_session. */
-  if (UE->max_delays_pdu_session > 0 && transaction_ongoing(UE)) {
-    int wait_us = 10000;
-    LOG_D(RRC, "UE %d: delay PDU session setup by %d us, pending %d retries\n", UE->rrc_ue_id, wait_us, UE->max_delays_pdu_session);
-    delay_transaction(msg_p, wait_us);
-    UE->max_delays_pdu_session--;
-    return;
-  }
-
   trigger_bearer_setup(rrc, UE, msg->nb_pdusessions_tosetup, msg->pdusession_setup_params, msg->ueAggMaxBitRateDownlink);
   return;
 }

openair2/RRC/NR/rrc_gNB_UE_context.c

@@ -202,7 +202,6 @@ rrc_gNB_ue_context_t *rrc_gNB_create_ue_context(sctp_assoc_t assoc_id,
               "UE F1 Context for ID %d already exists, logic bug\n",
               ue->rrc_ue_id);
   cu_add_f1_ue_data(ue->rrc_ue_id, &ue_data);
-  ue->max_delays_pdu_session = 20; /* see rrc_gNB_process_NGAP_PDUSESSION_SETUP_REQ() */
 
   RB_INSERT(rrc_nr_ue_tree_s, &rrc_instance_pP->rrc_ue_head, ue_context_p);
   LOG_I(NR_RRC,