From 5c2b72565416c70d2d52b7fcaf58abb117d04e27 Mon Sep 17 00:00:00 2001
From: Robert Schmidt <robert.schmidt@openairinterface.org>
Date: Fri, 24 May 2024 14:43:57 +0200
Subject: [PATCH] Refactor new-RNTI functionality in separate function

This function will be used in the case of a handover for getting a new
RNTI (checking that we do not reuse an already used RNTI).
---
 openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c | 27 +++----------------
 .../NR_MAC_gNB/gNB_scheduler_primitives.c     | 25 +++++++++++++++++
 openair2/LAYER2/NR_MAC_gNB/mac_proto.h        |  2 ++
 3 files changed, 30 insertions(+), 24 deletions(-)

diff --git a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c
index 1e437aa63e..061ad1ba27 100644
--- a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c
+++ b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c
@@ -40,7 +40,6 @@
 #include "common/utils/LOG/vcd_signal_dumper.h"
 #include "common/utils/nr/nr_common.h"
 #include "UTIL/OPT/opt.h"
-#include "SIMULATION/TOOLS/sim.h" // for taus
 
 /* rlc */
 #include "openair2/LAYER2/nr_rlc/nr_rlc_oai_api.h"
@@ -677,16 +676,6 @@ static NR_RA_t *find_free_nr_RA(NR_RA_t *ra_base, int ra_count, uint16_t preambl
   return NULL;
 }
 
-static const NR_RA_t *find_nr_RA_rnti(const NR_RA_t *ra_base, int ra_count, rnti_t rnti)
-{
-  for (int i = 0; i < ra_count; ++i) {
-    const NR_RA_t *ra = &ra_base[i];
-    if (ra->ra_state != nrRA_gNB_IDLE && ra->rnti == rnti)
-      return ra;
-  }
-  return NULL;
-}
-
 void nr_initiate_ra_proc(module_id_t module_idP,
                          int CC_id,
                          frame_t frameP,
@@ -712,23 +701,13 @@ void nr_initiate_ra_proc(module_id_t module_idP,
   }
 
   if (ra->rnti == 0) { // This condition allows for the usage of a preconfigured rnti for the CFRA
-    int loop = 0;
-    bool exist_connected_ue, exist_in_pending_ra_ue;
-    rnti_t trial = 0;
-    do {
-      // 3GPP TS 38.321 version 15.13.0 Section 7.1 Table 7.1-1: RNTI values
-      while (trial < 1 || trial > 0xffef)
-        trial = (taus() % 0xffef) + 1;
-      exist_connected_ue = find_nr_UE(&nr_mac->UE_info, trial) != NULL;
-      exist_in_pending_ra_ue = find_nr_RA_rnti(cc->ra, sizeofArray(cc->ra), ra->rnti) != NULL;
-      loop++;
-    } while (loop < 100 && (exist_connected_ue || exist_in_pending_ra_ue) );
-    if (loop == 100) {
+    bool rnti_found = nr_mac_get_new_rnti(&nr_mac->UE_info, cc->ra, sizeofArray(cc->ra), &ra->rnti);
+    if (!rnti_found) {
       LOG_E(NR_MAC, "initialisation random access: no more available RNTIs for new UE\n");
+      nr_clear_ra_proc(ra);
       NR_SCHED_UNLOCK(&nr_mac->sched_lock);
       return;
     }
-    ra->rnti = trial;
   }
 
   ra->preamble_frame = frameP;
diff --git a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
index 5ae2eb8607..b091cf69ee 100644
--- a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
+++ b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
@@ -53,6 +53,8 @@
 #include "uper_encoder.h"
 #include "uper_decoder.h"
 
+#include "SIMULATION/TOOLS/sim.h" // for taus
+
 #define ENABLE_MAC_PAYLOAD_DEBUG
 #define DEBUG_gNB_SCHEDULER 1
 
@@ -3395,3 +3397,26 @@ bool nr_mac_remove_lcid(NR_UE_sched_ctrl_t *sched_ctrl, long lcid)
   seq_arr_erase(&sched_ctrl->lc_config, elm.it);
   return true;
 }
+
+static const NR_RA_t *find_nr_RA_rnti(const NR_RA_t *ra_base, int ra_count, rnti_t rnti)
+{
+  for (int i = 0; i < ra_count; ++i) {
+    const NR_RA_t *ra = &ra_base[i];
+    if (ra->ra_state != nrRA_gNB_IDLE && ra->rnti == rnti)
+      return ra;
+  }
+  return NULL;
+}
+
+bool nr_mac_get_new_rnti(NR_UEs_t *UEs, const NR_RA_t *ra_base, int ra_count, rnti_t *rnti)
+{
+  int loop = 0;
+  bool exist_connected_ue, exist_in_pending_ra_ue;
+  do {
+    *rnti = (taus() % 0xffef) + 1;
+    exist_connected_ue = find_nr_UE(UEs, *rnti) != NULL;
+    exist_in_pending_ra_ue = find_nr_RA_rnti(ra_base, ra_count, *rnti) != NULL;
+    loop++;
+  } while (loop < 100 && (exist_connected_ue || exist_in_pending_ra_ue));
+  return loop < 100; // nothing found: loop count 100
+}
diff --git a/openair2/LAYER2/NR_MAC_gNB/mac_proto.h b/openair2/LAYER2/NR_MAC_gNB/mac_proto.h
index 4ee100f812..a75b9c0f60 100644
--- a/openair2/LAYER2/NR_MAC_gNB/mac_proto.h
+++ b/openair2/LAYER2/NR_MAC_gNB/mac_proto.h
@@ -477,4 +477,6 @@ void process_addmod_bearers_cellGroupConfig(NR_UE_sched_ctrl_t *sched_ctrl,
 bool nr_mac_add_lcid(NR_UE_sched_ctrl_t *sched_ctrl, const nr_lc_config_t *c);
 bool nr_mac_remove_lcid(NR_UE_sched_ctrl_t *sched_ctrl, long lcid);
 
+bool nr_mac_get_new_rnti(NR_UEs_t *UEs, const NR_RA_t *ra_base, int ra_count, rnti_t *rnti);
+
 #endif /*__LAYER2_NR_MAC_PROTO_H__*/