fix crnti mac ce handling in the rrc in normal (no handover) case

lib/include/srslte/common/byte_buffer.h

@@ -132,7 +132,7 @@ public:
   }
   uint32_t get_headroom() { return msg - buffer; }
   // Returns the remaining space from what is reported to be the length of msg
-  uint32_t                  get_tailroom() { return (sizeof(buffer) - (msg - buffer) - N_bytes); }
+  uint32_t                  get_tailroom() const { return (sizeof(buffer) - (msg - buffer) - N_bytes); }
   std::chrono::microseconds get_latency_us() const { return md.tp.get_latency_us(); }
 
   std::chrono::high_resolution_clock::time_point get_timestamp() const { return md.tp.get_timestamp(); }
@@ -147,6 +147,9 @@ public:
     N_bytes += size;
   }
 
+  // vector-like interface
+  void           resize(size_t size) { N_bytes = size; }
+  size_t         capacity() const { return get_tailroom(); }
   uint8_t*       data() { return msg; }
   const uint8_t* data() const { return msg; }
   uint32_t       size() const { return N_bytes; }

srsenb/hdr/stack/rrc/mac_controller.h

@@ -56,6 +56,7 @@ public:
   void handle_ho_prep(const asn1::rrc::ho_prep_info_r8_ies_s& ho_prep);
 
   const ue_cfg_t& get_ue_sched_cfg() const { return current_sched_ue_cfg; }
+  bool            is_crnti_set() const { return crnti_set; }
 
   void set_scell_activation(const std::bitset<SRSLTE_MAX_CARRIERS>& scell_mask);
   void set_drb_activation(bool active);

srsenb/hdr/stack/rrc/rrc.h

@@ -171,6 +171,7 @@ private:
   void config_mac();
   void parse_ul_dcch(uint16_t rnti, uint32_t lcid, srslte::unique_byte_buffer_t pdu);
   void parse_ul_ccch(uint16_t rnti, srslte::unique_byte_buffer_t pdu);
+  void send_rrc_connection_reject(uint16_t rnti);
 
   uint32_t              paging_tti = INVALID_TTI;
   srslte::byte_buffer_t byte_buf_paging;

srsenb/hdr/stack/rrc/rrc_ue.h

@@ -98,6 +98,7 @@ public:
   int  get_cqi(uint16_t* pmi_idx, uint16_t* n_pucch, uint32_t ue_cc_idx);
   int  get_ri(uint32_t m_ri, uint16_t* ri_idx);
   bool is_allocated() const;
+  bool is_crnti_set() const { return mac_ctrl.is_crnti_set(); }
 
   void send_dl_ccch(asn1::rrc::dl_ccch_msg_s* dl_ccch_msg);
   bool send_dl_dcch(const asn1::rrc::dl_dcch_msg_s* dl_dcch_msg,

srsenb/src/stack/rrc/rrc.cc

@@ -193,18 +193,48 @@ void rrc::upd_user(uint16_t new_rnti, uint16_t old_rnti)
 
   // Send Reconfiguration to old_rnti if is RRC_CONNECT or RRC Release if already released here
   auto old_it = users.find(old_rnti);
-  if (old_it != users.end()) {
-    auto ue_ptr = old_it->second.get();
-    if (ue_ptr->mobility_handler->is_ho_running()) {
-      ue_ptr->mobility_handler->trigger(ue::rrc_mobility::user_crnti_upd_ev{old_rnti, new_rnti});
-    } else if (ue_ptr->is_connected()) {
+  if (old_it == users.end()) {
+    send_rrc_connection_reject(old_rnti);
+    return;
+  }
+  ue* ue_ptr = old_it->second.get();
+
+  if (ue_ptr->mobility_handler->is_ho_running()) {
+    ue_ptr->mobility_handler->trigger(ue::rrc_mobility::user_crnti_upd_ev{old_rnti, new_rnti});
+  } else {
+    logger.info("Resuming rnti=0x%x RRC connection due to received C-RNTI CE from rnti=0x%x.", old_rnti, new_rnti);
+    if (ue_ptr->is_connected()) {
+      // Send a new RRC Reconfiguration to overlay previous
       old_it->second->send_connection_reconf();
-    } else {
-      old_it->second->send_connection_reject();
     }
   }
 }
 
+// Note: this method is not part of UE methods, because the UE context may not exist anymore when reject is sent
+void rrc::send_rrc_connection_reject(uint16_t rnti)
+{
+  dl_ccch_msg_s dl_ccch_msg;
+  dl_ccch_msg.msg.set_c1().set_rrc_conn_reject().crit_exts.set_c1().set_rrc_conn_reject_r8().wait_time = 10;
+
+  // Allocate a new PDU buffer, pack the message and send to PDCP
+  srslte::unique_byte_buffer_t pdu = srslte::make_byte_buffer();
+  if (pdu == nullptr) {
+    logger.error("Allocating pdu");
+    return;
+  }
+  asn1::bit_ref bref(pdu->msg, pdu->get_tailroom());
+  if (dl_ccch_msg.pack(bref) != asn1::SRSASN_SUCCESS) {
+    logger.error(pdu->msg, bref.distance_bytes(), "Failed to pack DL-CCCH-Msg:");
+    return;
+  }
+  pdu->N_bytes = bref.distance_bytes();
+
+  char buf[32] = {};
+  sprintf(buf, "SRB0 - rnti=0x%x", rnti);
+  log_rrc_message(buf, Tx, pdu.get(), dl_ccch_msg, dl_ccch_msg.msg.c1().type().to_string());
+  rlc->write_sdu(rnti, RB_ID_SRB0, std::move(pdu));
+}
+
 /*******************************************************************************
   PDCP interface
 *******************************************************************************/