rrc,nr: add MSG3 activity timer to rrc_nr

Signed-off-by: Carlo Galiotto <carlo@srs.io>

srsenb/hdr/stack/rrc/rrc_nr.h

@@ -104,7 +104,27 @@ public:
   class ue
   {
   public:
-    ue(rrc_nr* parent_, uint16_t rnti_, const sched_nr_ue_cfg_t& uecfg);
+    enum activity_timeout_type_t {
+      MSG3_RX_TIMEOUT = 0,   ///< Msg3 has its own timeout to quickly remove fake UEs from random PRACHs
+      UE_INACTIVITY_TIMEOUT, ///< (currently unused) UE inactivity timeout (usually bigger than reestablishment timeout)
+      MSG5_RX_TIMEOUT,       ///< (currently unused) for receiving RRCConnectionSetupComplete/RRCReestablishmentComplete
+      nulltype
+    };
+
+    /// List of results a RRC procedure may produce.
+    enum class procedure_result_code {
+      none,
+      activity_timeout,
+      error_mme_not_connected,
+      error_unknown_rnti,
+      radio_conn_with_ue_lost,
+      msg3_timeout,
+      fail_in_radio_interface_proc,
+      unspecified
+    };
+
+    /// @param [in] triggered_by_rach: indicates whether the UE is created as part of a RACH process
+    ue(rrc_nr* parent_, uint16_t rnti_, const sched_nr_ue_cfg_t& uecfg, bool triggered_by_rach = false);
 
     void send_connection_setup();
     void send_dl_ccch(asn1::rrc_nr::dl_ccch_msg_s* dl_dcch_msg);
@@ -119,14 +139,23 @@ public:
     bool     is_endc() { return endc; }
     uint16_t get_eutra_rnti() { return eutra_rnti; }
     void     get_metrics(rrc_ue_metrics_t& ue_metrics) { ue_metrics = {}; /*TODO fill RRC metrics*/ };
+
     // setters
 
     int  pack_rrc_reconfiguration();
     void deactivate_bearers();
 
+    /// methods to handle activity timer
+    std::string to_string(const activity_timeout_type_t& type);
+    void        set_activity_timeout(activity_timeout_type_t type);
+    void        set_activity(bool enabled = true);
+    void        activity_timer_expired(const activity_timeout_type_t type);
+
   private:
     rrc_nr*  parent = nullptr;
     uint16_t rnti   = SRSRAN_INVALID_RNTI;
+    /// for basic DL/UL activity timeout
+    srsran::unique_timer activity_timer;
 
     int pack_rrc_reconfiguration(asn1::dyn_octstring& packed_rrc_reconfig);
     int pack_secondary_cell_group_cfg(asn1::dyn_octstring& packed_secondary_cell_config);
@@ -179,6 +208,9 @@ public:
     rrc_nr_state_t state          = rrc_nr_state_t::RRC_IDLE;
     uint8_t        transaction_id = 0;
 
+    /// Connection release result.
+    procedure_result_code con_release_result = procedure_result_code::none;
+
     // RRC configs for UEs
     asn1::rrc_nr::cell_group_cfg_s   cell_group_cfg;
     asn1::rrc_nr::radio_bearer_cfg_s radio_bearer_cfg;

srsenb/src/stack/rrc/rrc_nr.cc

@@ -161,7 +161,8 @@ rrc_nr_cfg_t rrc_nr::update_default_cfg(const rrc_nr_cfg_t& current)
 int rrc_nr::add_user(uint16_t rnti, const sched_nr_ue_cfg_t& uecfg)
 {
   if (users.count(rnti) == 0) {
-    users.insert(std::make_pair(rnti, std::unique_ptr<ue>(new ue(this, rnti, uecfg))));
+    // in the ue ctor, "triggered_by_rach" is set to true so as to start the MSG3 RX TIMEOUT when we create the ue
+    users.insert(std::make_pair(rnti, std::unique_ptr<ue>(new ue(this, rnti, uecfg, true))));
     rlc->add_user(rnti);
     pdcp->add_user(rnti);
     logger.info("Added new user rnti=0x%x", rnti);
@@ -545,11 +546,95 @@ void rrc_nr::sgnb_release_request(uint16_t nr_rnti)
   Every function in UE class is called from a mutex environment thus does not
   need extra protection.
 *******************************************************************************/
-rrc_nr::ue::ue(rrc_nr* parent_, uint16_t rnti_, const sched_nr_ue_cfg_t& uecfg_) :
+rrc_nr::ue::ue(rrc_nr* parent_, uint16_t rnti_, const sched_nr_ue_cfg_t& uecfg_, bool triggered_by_rach) :
   parent(parent_), rnti(rnti_), uecfg(uecfg_)
 {
   // Derive UE cfg from rrc_cfg_nr_t
   uecfg.phy_cfg.pdcch = parent->cfg.cell_list[0].phy_cell.pdcch;
+
+  // Set timer for MSG3_RX_TIMEOUT or UE_INACTIVITY_TIMEOUT
+  activity_timer = parent->task_sched.get_unique_timer();
+  triggered_by_rach ? set_activity_timeout(MSG3_RX_TIMEOUT) : set_activity_timeout(UE_INACTIVITY_TIMEOUT);
+}
+
+void rrc_nr::ue::set_activity_timeout(activity_timeout_type_t type)
+{
+  uint32_t deadline_ms = 0;
+
+  switch (type) {
+    case MSG3_RX_TIMEOUT:
+      // TODO: Retrieve the parameters from somewhere(RRC?) - Currently hardcoded to 100ms
+      deadline_ms = 100;
+      break;
+    case UE_INACTIVITY_TIMEOUT:
+      // TODO: Add a value for the inactivity timeout - currently no activity set this case
+      return;
+    default:
+      parent->logger.error("Unknown timeout type %d", type);
+      return;
+  }
+
+  // Currently we only set the timer for the MSG3_RX_TIMEOUT case
+  activity_timer.set(deadline_ms, [this, type](uint32_t tid) { activity_timer_expired(type); });
+  parent->logger.debug("Setting timer for %s for rnti=0x%x to %dms", to_string(type).c_str(), rnti, deadline_ms);
+
+  set_activity();
+}
+
+void rrc_nr::ue::set_activity(bool enabled)
+{
+  if (rnti == SRSRAN_MRNTI) {
+    return;
+  }
+  if (not enabled) {
+    if (activity_timer.is_running()) {
+      parent->logger.debug("Inactivity timer interrupted for rnti=0x%x", rnti);
+    }
+    activity_timer.stop();
+    return;
+  }
+
+  // re-start activity timer with current timeout value
+  activity_timer.run();
+  parent->logger.debug("Activity registered for rnti=0x%x (timeout_value=%dms)", rnti, activity_timer.duration());
+}
+
+void rrc_nr::ue::activity_timer_expired(const activity_timeout_type_t type)
+{
+  parent->logger.info("Activity timer for rnti=0x%x expired after %d ms", rnti, activity_timer.time_elapsed());
+
+  // TODO: Insert a check to ensure the RNTI exists
+#if 0
+  if (parent->s1ap->user_exists(rnti)) {
+#endif
+  switch (type) {
+    case UE_INACTIVITY_TIMEOUT:
+      // TODO: Add action to be executed
+      break;
+    case MSG3_RX_TIMEOUT:
+      // MSG3 timeout, no need to notify S1AP, just remove UE
+      parent->rem_user(rnti);
+      con_release_result = procedure_result_code::msg3_timeout;
+      break;
+    default:
+      // Unhandled activity timeout, just remove UE and log an error
+      parent->rem_user(rnti);
+      con_release_result = procedure_result_code::activity_timeout;
+      parent->logger.error(
+          "Unhandled reason for activity timer expiration. rnti=0x%x, cause %d", rnti, static_cast<unsigned>(type));
+  }
+#if 0
+  } else {
+    parent->rem_user_thread(rnti);
+  }
+#endif
+  state = rrc_nr_state_t::RRC_IDLE;
+}
+
+std::string rrc_nr::ue::to_string(const activity_timeout_type_t& type)
+{
+  constexpr static const char* options[] = {"Msg3 reception", "UE inactivity", "UE reestablishment"};
+  return srsran::enum_to_text(options, (uint32_t)activity_timeout_type_t::nulltype, (uint32_t)type);
 }
 
 void rrc_nr::ue::send_connection_setup()
@@ -1289,6 +1374,10 @@ int rrc_nr::ue::handle_sgnb_addition_request(uint16_t eutra_rnti_, const sgnb_ad
   ack_params.eps_bearer_id = req_params.eps_bearer_id;
   parent->rrc_eutra->sgnb_addition_ack(eutra_rnti_, ack_params);
 
+  // stop activity timer for msg3
+  activity_timer.stop();
+  parent->logger.debug("SgNB addition req. - Stopping MSG3 activity timer for rnti=0x%x", rnti);
+
   // recognize RNTI as ENDC user
   endc       = true;
   eutra_rnti = eutra_rnti_;
@@ -1302,6 +1391,8 @@ void rrc_nr::ue::crnti_ce_received()
   if (endc) {
     // send SgNB addition complete for ENDC users
     parent->rrc_eutra->sgnb_addition_complete(eutra_rnti, rnti);
+    activity_timer.stop();
+    parent->logger.debug("Received MAC CE-RNTI for 0x%x - stopping MSG3 timer", rnti);
 
     // Add DRB1 to MAC
     for (auto& drb : cell_group_cfg.rlc_bearer_to_add_mod_list) {