target-CU-CP: Transfer PDCP Count to target-CU-UP

Upon reception of NG RAN Status at the target CU-CP, send PDCP Status
via E1 Bearer Context Modification to the target CU-UP and update PDCP Count
upon reception of the message.

For the sake of simplicity, re-used and extended legacy e1_send_bearer_updates.
Further refactoring is not addressed in this commit.

openair2/LAYER2/nr_pdcp/cucp_cuup_handler.c

@@ -303,6 +303,20 @@ void e1_bearer_context_modif(const e1ap_bearer_mod_req_t *req)
         modified->pdcp_status->ul_count.sn = ul_count.sn;
       }
 
+      // PDCP Status received (from source CU-UP)
+      if (to_modif->pdcp_status) {
+        DevAssert(to_modif->pdcp_config);
+        DevAssert(to_modif->pdcp_config->pDCP_SN_Size_DL == to_modif->pdcp_config->pDCP_SN_Size_UL);
+        bool is_sn_len_18 = to_modif->pdcp_config->pDCP_SN_Size_DL == NR_PDCP_Config__drb__pdcp_SN_SizeDL_len18bits;
+        nr_pdcp_count_t dl_count = { .hfn = to_modif->pdcp_status->dl_count.hfn, .sn = to_modif->pdcp_status->dl_count.sn};
+        nr_pdcp_count_t ul_count = { .hfn = to_modif->pdcp_status->ul_count.hfn, .sn = to_modif->pdcp_status->ul_count.sn};
+        nr_pdcp_count_update(req->gNB_cu_cp_ue_id,
+                             to_modif->id,
+                             dl_count,
+                             ul_count,
+                             is_sn_len_18 ? LONG_SN_SIZE : SHORT_SN_SIZE);
+      }
+
       if (f1inst < 0) // no F1-U?
         continue; // nothing to do
 

openair2/RRC/NR/nr_rrc_proto.h

@@ -128,5 +128,6 @@ void openair_rrc_gNB_configuration(gNB_RRC_INST *rrc, gNB_RrcConfigurationReq *c
 NR_SRB_ToAddModList_t *createSRBlist(gNB_RRC_UE_t *ue, uint8_t reestablish);
 NR_DRB_ToAddModList_t *createDRBlist(gNB_RRC_UE_t *ue, bool reestablish);
 void activate_srb(gNB_RRC_UE_t *UE, int srb_id);
+void e1_send_bearer_updates(gNB_RRC_INST *rrc, gNB_RRC_UE_t *UE, int n, f1ap_drb_setup_t *drbs, const ngap_drb_status_t *drb_status);
 
 #endif

openair2/RRC/NR/rrc_gNB.c

@@ -2076,9 +2076,28 @@ static void store_du_f1u_tunnel(const f1ap_drb_setup_t *drbs, int n, gNB_RRC_UE_
   }
 }
 
-/* \brief use list of DRBs and send the corresponding bearer update message via
- * E1 to the CU of this UE. Also updates TEID info internally */
-static void e1_send_bearer_updates(gNB_RRC_INST *rrc, gNB_RRC_UE_t *UE, int n, f1ap_drb_setup_t *drbs)
+static void fill_e1_bearer_modif_pdcp_status(gNB_RRC_UE_t *UE,
+                                             DRB_nGRAN_to_mod_t *drb_to_mod,
+                                             const int drb_id,
+                                             const bool um_on_default_drb,
+                                             const ngap_drb_status_t *drb_status)
+{
+  DevAssert(drb_status);
+  drb_to_mod->id = drb_id;
+  drb_to_mod->pdcp_sn_status_requested = false;
+  // PDCP SN Status Information
+  drb_to_mod->pdcp_config = calloc_or_fail(1, sizeof(*drb_to_mod->pdcp_config));
+  set_bearer_context_pdcp_config(drb_to_mod->pdcp_config, get_drb(UE, drb_id), um_on_default_drb);
+  drb_to_mod->pdcp_status = calloc_or_fail(1, sizeof(*drb_to_mod->pdcp_status));
+  drb_to_mod->pdcp_status->dl_count.hfn = drb_status->dl_count.hfn;
+  drb_to_mod->pdcp_status->dl_count.sn = drb_status->dl_count.pdcp_sn;
+  drb_to_mod->pdcp_status->ul_count.hfn = drb_status->ul_count.hfn;
+  drb_to_mod->pdcp_status->ul_count.sn = drb_status->ul_count.pdcp_sn;
+}
+
+/** @brief Fill and send Bearer Context Modification Request with:
+ * (1) from F1 UE Context DRB to setup list, or (2) with PDCP Status Request */
+void e1_send_bearer_updates(gNB_RRC_INST *rrc, gNB_RRC_UE_t *UE, int n, f1ap_drb_setup_t *drbs, const ngap_drb_status_t *drb_status)
 {
   // Quit bearer updates if no CU-UP is associated
   if (!is_cuup_associated(rrc)) {
@@ -2110,6 +2129,9 @@ static void e1_send_bearer_updates(gNB_RRC_INST *rrc, gNB_RRC_UE_t *UE, int n, f
       // PDCP SN Status Request
       drb_to_mod.pdcp_sn_status_requested = true;
       LOG_I(NR_RRC, "PDCP Status requested (drb_id=%d)\n", drb_id);
+    } else if (drb_status) {
+      /* On-going handover: send PDCP Status */
+      fill_e1_bearer_modif_pdcp_status(UE, &drb_to_mod, drb_id, rrc->configuration.um_on_default_drb, drb_status);
     }
     rrc_pdu_session_param_t *pdu = find_pduSession_from_drbId(UE, drb_id);
     if (!pdu)
@@ -2183,7 +2205,7 @@ static void rrc_CU_process_ue_context_setup_response(MessageDef *msg_p, instance
     AssertFatal(UE->Srb[1].Active && UE->Srb[2].Active, "SRBs 1 and 2 must be active during DRB Establishment");
     store_du_f1u_tunnel(resp->drbs, resp->drbs_len, UE);
     if (num_drb == 0)
-      e1_send_bearer_updates(rrc, UE, resp->drbs_len, resp->drbs);
+      e1_send_bearer_updates(rrc, UE, resp->drbs_len, resp->drbs, NULL);
     else
       cuup_notify_reestablishment(rrc, UE);
   }
@@ -2317,7 +2339,7 @@ static void rrc_CU_process_ue_context_modification_response(MessageDef *msg_p, i
   bool is_inter_cu_ho = UE->ho_context && UE->ho_context->source && !UE->ho_context->target;
   if (resp->drbs_len > 0 || is_inter_cu_ho) {
     store_du_f1u_tunnel(resp->drbs, resp->drbs_len, UE);
-    e1_send_bearer_updates(rrc, UE, resp->drbs_len, resp->drbs);
+    e1_send_bearer_updates(rrc, UE, resp->drbs_len, resp->drbs, NULL);
   }
 
   if (resp->du_to_cu_rrc_info) {

openair2/RRC/NR/rrc_gNB_NGAP.c

@@ -1639,16 +1639,7 @@ int rrc_gNB_process_NGAP_DL_RAN_STATUS_TRANSFER(MessageDef *msg_p, instance_t in
           s->dl_count.sn_len == NGAP_SN_LENGTH_18 ? "18-bit" : "12-bit");
 
     // Send to PDCP layer
-    for (int j = 0; j < MAX_DRBS_PER_UE; j++) {
-      if (UE->established_drbs[j].drb_id == s->drb_id)
-        nr_pdcp_update_ran_status(UE->rrc_ue_id,
-                                  s->drb_id,
-                                  s->ul_count.pdcp_sn,
-                                  s->ul_count.hfn,
-                                  s->dl_count.pdcp_sn,
-                                  s->dl_count.hfn,
-                                  s->dl_count.sn_len == NGAP_SN_LENGTH_18);
-    }
+    e1_send_bearer_updates(rrc, UE, 0, NULL, s);
   }
 
   return 0;