Paging (RRC): refactor NGAP Paging handler in CUCP

RRC now builds F1AP paging messages directly by calling F1AP/direct
callbacks and aligning the CU/DU intergace with the F1AP design in the CU.
Messages are forwarded based on TAI-based cell matching across DUs.

- Remove F1AP_PAGING_IND message def and f1ap_paging_ind_t.
  RRC no longer sends ITTI F1AP_PAGING_IND; it builds f1ap_paging_t
  and passes it to the DU path.

- rrc_gNB_process_PAGING_IND: new signature (rrc, instance, msg)
  with const where appropriate; call in rrc_gnb_task() updated.

- NGAP handler logic: For each TAI, match (PLMN + TAC) to
  rrc->configuration; collect matching TAIs. Build one f1ap_paging_t
  (5G-S-TMSI via nr_construct_5g_s_tmsi(), identity type
  F1AP_PAGING_IDENTITY_CN_UE, optional drx/priority/origin copied
  from ngap_paging_ind_t), call rrc_send_paging_to_dus(), then
  free_f1ap_paging(). Remove the previous AssertFatal stub, CC loop,
  NODE_IS_CU branch, and UE lookup logic: it is now handled by
  F1AP/direct CU callbacks.

- rrc_gNB_du: Add rrc_send_paging_to_dus(rrc, tais, n_tai, msg).
  Iterate DUs with RB_FOREACH; for each DU, fill msg->cells from
  du->cells whose (PLMN + TAC) matches any requested TAI, set
  n_cells, then call rrc->mac_rrc.paging_transfer(du->assoc_id,
  msg). Skip DUs with no matching cells. Prevents duplicate paging
  when multiple TAIs map to the same PLMN.

openair2/COMMON/f1ap_messages_def.h

@@ -65,4 +65,3 @@ MESSAGE_DEF(F1AP_UE_CONTEXT_MODIFICATION_REFUSE, MESSAGE_PRIORITY_MED, f1ap_ue_c
 
 /* CU -> DU*/
 MESSAGE_DEF(F1AP_PAGING, MESSAGE_PRIORITY_MED, f1ap_paging_t, f1ap_paging)
-MESSAGE_DEF(F1AP_PAGING_IND, MESSAGE_PRIORITY_MED, f1ap_paging_ind_t, f1ap_paging_ind)

openair2/COMMON/f1ap_messages_types.h

@@ -68,7 +68,6 @@
 #define F1AP_UE_CONTEXT_RELEASE_CMD(mSGpTR)        (mSGpTR)->ittiMsg.f1ap_ue_context_release_cmd
 #define F1AP_UE_CONTEXT_RELEASE_COMPLETE(mSGpTR)   (mSGpTR)->ittiMsg.f1ap_ue_context_release_complete
 
-#define F1AP_PAGING_IND(mSGpTR)                    (mSGpTR)->ittiMsg.f1ap_paging_ind
 #define F1AP_PAGING(mSGpTR)                        (mSGpTR)->ittiMsg.f1ap_paging
 
 /* Length of the transport layer address string
@@ -633,15 +632,6 @@ typedef struct f1ap_ue_context_rel_cplt_t {
   uint32_t gNB_DU_ue_id;
 } f1ap_ue_context_rel_cplt_t;
 
-typedef struct f1ap_paging_ind_s {
-  uint16_t ueidentityindexvalue;
-  uint64_t fiveg_s_tmsi;
-  uint8_t  fiveg_s_tmsi_length;
-  plmn_id_t plmn;
-  uint64_t nr_cellid;
-  uint8_t  paging_drx;
-} f1ap_paging_ind_t;
-
 typedef struct f1ap_paging_cell_item_s {
   plmn_id_t plmn;
   uint64_t nr_cellid;