Re-establish RLC for SRB1 only when receiving RRCReestablishmentRequest

- according to 5.3.7.4 of TS 38.331: 1> re-establish RLC for SRB1;
- gNB:
1) re-establish RLC for SRB1 in nr_rlc_update_id
2) re-establish RLC for remaining RBs concurrently with RRCReconfiguration

issue: gNB) in nr_rlc_update_id the gNB is re-establishing RLC for all
            RBs at the same time when receiving RRCReestablishmentRequest
            from UE
        UE) according to the specs, the UE is re-establishing RLC for
            SRB1 with RRCReestablishmentRequest the other RBs are
            re-established during RRCReconfiguration (in our case in
            nr_rrc_ue_process_RadioBearerConfig) when receiving
            reestablishRLC IE in rlc_BearerToAddModList
    RLC TX) this leads to RLC counters mismatch after re-establishment:
            control PDUs discarded until max nb of retx is reached
            and then UL failure occurs

openair2/LAYER2/NR_MAC_gNB/mac_rrc_dl_handler.c

@@ -687,6 +687,12 @@ void dl_rrc_message_transfer(const f1ap_dl_rrc_message_t *dl_rrc)
     nr_mac_enable_ue_rrc_processing_timer(mac, UE, /* apply_cellGroup = */ true);
     NR_SCHED_UNLOCK(&mac->sched_lock);
     UE->expect_reconfiguration = false;
+    /* Re-establish RLC for all remaining bearers */
+    if (UE->reestablish_rlc) {
+      for (int i = 1; i < UE->UE_sched_ctrl.dl_lc_num; ++i)
+        nr_rlc_reestablish_entity(dl_rrc->gNB_DU_ue_id, UE->UE_sched_ctrl.dl_lc_ids[i]);
+      UE->reestablish_rlc = false;
+    }
   }
 
   if (dl_rrc->old_gNB_DU_ue_id != NULL) {
@@ -716,6 +722,9 @@ void dl_rrc_message_transfer(const f1ap_dl_rrc_message_t *dl_rrc)
     pthread_mutex_unlock(&mac->sched_lock);
     nr_rlc_remove_ue(dl_rrc->gNB_DU_ue_id);
     nr_rlc_update_id(*dl_rrc->old_gNB_DU_ue_id, dl_rrc->gNB_DU_ue_id);
+    /* Set flag to trigger RLC re-establishment
+     * for remaining RBs in next RRCReconfiguration */
+    UE->reestablish_rlc = true;
     /* 38.331 clause 5.3.7.4: apply the specified configuration defined in 9.2.1 for SRB1 */
     nr_rlc_reconfigure_entity(dl_rrc->gNB_DU_ue_id, 1, NULL);
     instance_t f1inst = get_f1_gtp_instance();

openair2/LAYER2/NR_MAC_gNB/nr_mac_gNB.h

@@ -683,6 +683,8 @@ typedef struct {
   NR_CellGroupConfig_t *CellGroup;
   /// CellGroupConfig that is to be activated after the next reconfiguration
   bool expect_reconfiguration;
+  /// reestablishRLC has to be signaled in RRCreconfiguration
+  bool reestablish_rlc;
   NR_CellGroupConfig_t *reconfigCellGroup;
   bool apply_cellgroup;
   NR_UE_NR_Capability_t *capability;

openair2/LAYER2/nr_rlc/nr_rlc_oai_api.c

@@ -650,7 +650,7 @@ void nr_rlc_reestablish_entity(int ue_id, int lc_id)
   nr_rlc_entity_t *rb = get_rlc_entity_from_lcid(ue, lc_id);
 
   if (rb != NULL) {
-    LOG_D(RLC, "%s: RB found! (channel ID %d), re-establish RLC\n", __func__, lc_id);
+    LOG_D(RLC, "RB found! (channel ID %d), re-establish RLC\n", lc_id);
     rb->reestablishment(rb);
   } else {
     LOG_E(RLC, "no RLC entity found (channel ID %d) for reestablishment\n", lc_id);
@@ -1065,12 +1065,11 @@ bool nr_rlc_update_id(int from_id, int to_id)
   }
   ue->ue_id = to_id;
   LOG_I(RLC, "Update old UE ID %d context to ID %d\n", from_id, to_id);
-  for (int i = 0; i < sizeof(ue->srb) / sizeof(ue->srb[0]); ++i)
-    if (ue->srb[i])
-      ue->srb[i]->reestablishment(ue->srb[i]);
-  for (int i = 0; i < sizeof(ue->drb) / sizeof(ue->drb[0]); ++i)
-    if (ue->drb[i])
-      ue->drb[i]->reestablishment(ue->drb[i]);
+  /* re-establish RLC for SRB1: according to 5.3.7.4 of TS 38.331 */
+  if (ue->srb[0]) {
+    LOG_I(RLC, "Re-establish RLC for SRB 1\n");
+    ue->srb[0]->reestablishment(ue->srb[0]);
+  }
   nr_rlc_manager_unlock(nr_rlc_ue_manager);
   return true;
 }

openair2/RRC/NR/rrc_gNB.c

@@ -1080,6 +1080,10 @@ static void rrc_gNB_process_RRCReestablishmentComplete(const protocol_ctxt_t *co
   for (i = 1; i < ue_p->masterCellGroup->rlc_BearerToAddModList->list.count; ++i)
     asn1cSeqAdd(&cellGroupConfig->rlc_BearerToAddModList->list, ue_p->masterCellGroup->rlc_BearerToAddModList->list.array[i]);
 
+  /*
+   * At this stage, PDCP entity are re-established and reestablishRLC is flagged
+   * with RRCReconfiguration to complete RLC re-establishment of remaining bearers
+   */
   for (i = 0; i < cellGroupConfig->rlc_BearerToAddModList->list.count; i++) {
     asn1cCallocOne(cellGroupConfig->rlc_BearerToAddModList->list.array[i]->reestablishRLC,
                    NR_RLC_BearerConfig__reestablishRLC_true);