fix reestablishment after S1 handover by setting ncc accordingly

srsenb/hdr/stack/rrc/rrc_bearer_cfg.h

@@ -36,9 +36,11 @@ public:
 
   bool set_security_capabilities(const asn1::s1ap::ue_security_cap_s& caps);
   void set_security_key(const asn1::fixed_bitstring<256, false, true>& key);
+  void set_ncc(uint8_t ncc_) { ncc = ncc_; }
 
   asn1::rrc::security_algorithm_cfg_s get_security_algorithm_cfg();
   const srslte::as_security_config_t& get_as_sec_cfg() const { return sec_cfg; }
+  uint8_t                             get_ncc() const { return ncc; }
   bool                                is_as_sec_cfg_valid() const { return k_enb_present; }
 
   void regenerate_keys_handover(uint32_t new_pci, uint32_t new_dl_earfcn);
@@ -52,6 +54,7 @@ private:
   asn1::s1ap::ue_security_cap_s security_capabilities = {};
   uint8_t                       k_enb[32]             = {}; // Provided by MME
   srslte::as_security_config_t  sec_cfg               = {};
+  uint8_t                       ncc                   = 0;
 };
 
 class bearer_cfg_handler

srsenb/hdr/stack/rrc/rrc_ue.h

@@ -50,7 +50,7 @@ public:
   rrc_state_t get_state();
 
   void send_connection_setup();
-  void send_connection_reest();
+  void send_connection_reest(uint8_t ncc);
   void send_connection_reject();
   void send_connection_release();
   void send_connection_reest_rej();

srsenb/src/stack/rrc/rrc_mobility.cc

@@ -1050,6 +1050,7 @@ void rrc::ue::rrc_mobility::handle_ho_req(idle_st& s, const ho_req_rx_ev& ho_req
   rrc_conn_recfg_r8_ies_s& recfg_r8 = dl_dcch_msg.msg.c1().rrc_conn_recfg().crit_exts.c1().rrc_conn_recfg_r8();
 
   // Apply new Security Config based on HandoverRequest
+  // See TS 33.401, Sec. 7.2.8.4.3
   recfg_r8.security_cfg_ho_present = true;
   recfg_r8.security_cfg_ho.handov_type.set(security_cfg_ho_s::handov_type_c_::types_opts::intra_lte);
   recfg_r8.security_cfg_ho.handov_type.intra_lte().security_algorithm_cfg_present = true;
@@ -1143,8 +1144,10 @@ bool rrc::ue::rrc_mobility::apply_ho_prep_cfg(const ho_prep_info_r8_ies_s&    ho
   }
 
   // Regenerate AS Keys
+  // See TS 33.401, Sec. 7.2.8.4.3
   rrc_ue->ue_security_cfg.set_security_capabilities(ho_req_msg.protocol_ies.ue_security_cap.value);
   rrc_ue->ue_security_cfg.set_security_key(ho_req_msg.protocol_ies.security_context.value.next_hop_param);
+  rrc_ue->ue_security_cfg.set_ncc(ho_req_msg.protocol_ies.security_context.value.next_hop_chaining_count);
   rrc_ue->ue_security_cfg.regenerate_keys_handover(target_cell_cfg.pci, target_cell_cfg.dl_earfcn);
 
   // Save UE Capabilities

srsenb/src/stack/rrc/rrc_ue.cc

@@ -340,7 +340,7 @@ void rrc::ue::handle_rrc_con_reest_req(rrc_conn_reest_request_s* msg)
     if (parent->users.count(old_rnti)) {
       parent->rrc_log->info("ConnectionReestablishmentRequest for rnti=0x%x. Sending Connection Reestablishment\n",
                             old_rnti);
-      send_connection_reest();
+      send_connection_reest(parent->users[old_rnti]->ue_security_cfg.get_ncc());
 
       // Cancel Handover in Target eNB if on-going
       parent->users[old_rnti]->mobility_handler->trigger(rrc_mobility::ho_cancel_ev{});
@@ -386,7 +386,7 @@ void rrc::ue::handle_rrc_con_reest_req(rrc_conn_reest_request_s* msg)
   return;
 }
 
-void rrc::ue::send_connection_reest()
+void rrc::ue::send_connection_reest(uint8_t ncc)
 {
   // Re-Establish SRB1
   bearer_list.add_srb(1);
@@ -403,6 +403,9 @@ void rrc::ue::send_connection_reest()
   fill_rrc_setup_rr_config_dedicated(rr_cfg);
   phys_cfg_ded_s* phy_cfg = &rr_cfg->phys_cfg_ded;
 
+  // Set NCC
+  reest.next_hop_chaining_count = ncc;
+
   // Apply ConnectionReest Configuration to MAC scheduler
   mac_ctrl->handle_con_reest(reest);