fix+refactor of the ue rrc handover preparation procedure to avoid deadlocking

srsue/hdr/stack/rrc/rrc.h

@@ -113,13 +113,14 @@ public:
     }
   }
 
-  cell_t() {
+  cell_t()
+  {
     gettimeofday(&last_update, nullptr);
     has_valid_sib1  = false;
     has_valid_sib2  = false;
     has_valid_sib3  = false;
     has_valid_sib13 = false;
-    phy_cell        = {0,0,0};
+    phy_cell        = {0, 0, 0};
     rsrp            = NAN;
     rsrq            = NAN;
     sib1            = {};
@@ -128,14 +129,11 @@ public:
     sib13           = {};
   }
 
-  cell_t(phy_interface_rrc_lte::phy_cell_t phy_cell_) : cell_t()
-  {
-    phy_cell = phy_cell_;
-  }
+  cell_t(phy_interface_rrc_lte::phy_cell_t phy_cell_) : cell_t() { phy_cell = phy_cell_; }
 
-  uint32_t get_earfcn() { return phy_cell.earfcn; }
+  uint32_t get_earfcn() const { return phy_cell.earfcn; }
 
-  uint32_t get_pci() { return phy_cell.pci; }
+  uint32_t get_pci() const { return phy_cell.pci; }
 
   void set_rsrp(float rsrp_)
   {
@@ -157,9 +155,9 @@ public:
     }
   }
 
-  float get_rsrp() { return rsrp; }
-  float get_rsrq() { return rsrq; }
-  float get_cfo_hz() { return phy_cell.cfo_hz; }
+  float get_rsrp() const { return rsrp; }
+  float get_rsrq() const { return rsrq; }
+  float get_cfo_hz() const { return phy_cell.cfo_hz; }
 
   void set_sib1(asn1::rrc::sib_type1_s* sib1_);
   void set_sib2(asn1::rrc::sib_type2_s* sib2_);
@@ -181,7 +179,7 @@ public:
   asn1::rrc::sib_type3_s*     sib3ptr() { return &sib3; }
   asn1::rrc::sib_type13_r9_s* sib13ptr() { return &sib13; }
 
-  uint32_t get_cell_id() { return (uint32_t)sib1.cell_access_related_info.cell_id.to_number(); }
+  uint32_t get_cell_id() const { return (uint32_t)sib1.cell_access_related_info.cell_id.to_number(); }
 
   bool has_sib1() { return has_valid_sib1; }
   bool has_sib2() { return has_valid_sib2; }
@@ -239,7 +237,7 @@ public:
     return 0;
   }
 
-  std::string to_string()
+  std::string to_string() const
   {
     char buf[256];
     snprintf(buf,
@@ -370,16 +368,16 @@ private:
 
   void process_pcch(srslte::unique_byte_buffer_t pdu);
 
-  stack_interface_rrc*      stack   = nullptr;
-  srslte::byte_buffer_pool* pool    = nullptr;
-  srslte::log_ref             rrc_log;
-  phy_interface_rrc_lte*    phy     = nullptr;
-  mac_interface_rrc*        mac     = nullptr;
-  rlc_interface_rrc*        rlc     = nullptr;
-  pdcp_interface_rrc*       pdcp    = nullptr;
-  nas_interface_rrc*        nas     = nullptr;
-  usim_interface_rrc*       usim    = nullptr;
-  gw_interface_rrc*         gw      = nullptr;
+  stack_interface_rrc*      stack = nullptr;
+  srslte::byte_buffer_pool* pool  = nullptr;
+  srslte::log_ref           rrc_log;
+  phy_interface_rrc_lte*    phy  = nullptr;
+  mac_interface_rrc*        mac  = nullptr;
+  rlc_interface_rrc*        rlc  = nullptr;
+  pdcp_interface_rrc*       pdcp = nullptr;
+  nas_interface_rrc*        nas  = nullptr;
+  usim_interface_rrc*       usim = nullptr;
+  gw_interface_rrc*         gw   = nullptr;
 
   srslte::unique_byte_buffer_t dedicated_info_nas;
 
@@ -407,8 +405,8 @@ private:
   srslte::phy_cfg_t           current_phy_cfg, previous_phy_cfg = {};
   srslte::mac_cfg_t           current_mac_cfg, previous_mac_cfg = {};
   bool                        current_scell_configured[SRSLTE_MAX_CARRIERS] = {};
-  bool                        pending_mob_reconf = false;
-  asn1::rrc::rrc_conn_recfg_s mob_reconf         = {};
+  bool                        pending_mob_reconf                            = false;
+  asn1::rrc::rrc_conn_recfg_s mob_reconf                                    = {};
 
   srslte::as_security_config_t sec_cfg = {};
 
@@ -516,6 +514,7 @@ private:
   enum class cs_result_t { changed_cell, same_cell, no_cell };
 
   // RRC procedures (fwd declared)
+  class phy_cell_select_proc;
   class cell_search_proc;
   class si_acquire_proc;
   class serving_cell_config_proc;
@@ -526,6 +525,8 @@ private:
   class go_idle_proc;
   class cell_reselection_proc;
   class connection_reest_proc;
+  class ho_prep_proc;
+  srslte::proc_t<phy_cell_select_proc>                                       phy_cell_selector;
   srslte::proc_t<cell_search_proc, phy_interface_rrc_lte::cell_search_ret_t> cell_searcher;
   srslte::proc_t<si_acquire_proc>                                            si_acquirer;
   srslte::proc_t<serving_cell_config_proc>                                   serv_cell_cfg;
@@ -536,6 +537,7 @@ private:
   srslte::proc_t<plmn_search_proc>                                           plmn_searcher;
   srslte::proc_t<cell_reselection_proc>                                      cell_reselector;
   srslte::proc_t<connection_reest_proc>                                      connection_reest;
+  srslte::proc_t<ho_prep_proc>                                               ho_prep_proc;
 
   srslte::proc_manager_list_t callback_list;
 
@@ -572,9 +574,7 @@ private:
   bool con_reconfig(asn1::rrc::rrc_conn_recfg_s* reconfig);
   void con_reconfig_failed();
   bool con_reconfig_ho(asn1::rrc::rrc_conn_recfg_s* reconfig);
-  bool ho_prepare();
   void ho_failed();
-  void start_ho();
   void start_go_idle();
   void rrc_connection_release(const std::string& cause);
   void radio_link_failure();

srsue/hdr/stack/rrc/rrc_procedures.h

@@ -35,7 +35,7 @@ namespace srsue {
 
 // background workers use this event to signal the result of a cell select phy procedure
 struct cell_select_event_t {
-  cell_select_event_t(bool c_) : cs_ret(c_) {}
+  explicit cell_select_event_t(bool c_) : cs_ret(c_) {}
   bool cs_ret;
 };
 
@@ -43,6 +43,22 @@ struct cell_select_event_t {
  *         Procedures
  *******************************/
 
+class rrc::phy_cell_select_proc
+{
+public:
+  explicit phy_cell_select_proc(rrc* parent_);
+  srslte::proc_outcome_t init(const cell_t& target_cell);
+  srslte::proc_outcome_t react(cell_select_event_t ev);
+  void                   then(const srslte::proc_state_t& result);
+  srslte::proc_outcome_t step() { return srslte::proc_outcome_t::yield; }
+  static const char*     name() { return "PHY Cell Select"; }
+
+private:
+  // args
+  rrc*          rrc_ptr;
+  const cell_t* target_cell;
+};
+
 class rrc::cell_search_proc
 {
 public:
@@ -85,8 +101,7 @@ public:
   struct si_acq_timer_expired {
     uint32_t timer_id;
   };
-  struct sib_received_ev {
-  };
+  struct sib_received_ev {};
 
   explicit si_acquire_proc(rrc* parent_);
   srslte::proc_outcome_t init(uint32_t sib_index_);
@@ -287,6 +302,31 @@ private:
   srslte::proc_outcome_t cell_criteria();
 };
 
+class rrc::ho_prep_proc
+{
+public:
+  struct t304_expiry {};
+
+  explicit ho_prep_proc(rrc* rrc_);
+  srslte::proc_outcome_t init(const asn1::rrc::rrc_conn_recfg_s& rrc_reconf);
+  srslte::proc_outcome_t react(cell_select_event_t ev);
+  srslte::proc_outcome_t react(t304_expiry ev);
+  srslte::proc_outcome_t step();
+  void                   then(const srslte::proc_state_t& result);
+  static const char*     name() { return "Handover Preparation"; }
+
+private:
+  rrc* rrc_ptr = nullptr;
+
+  // args
+  asn1::rrc::rrc_conn_recfg_r8_ies_s recfg_r8;
+  cell_t                             ho_src_cell;
+  uint16_t                           ho_src_rnti = 0;
+
+  // state
+  uint32_t target_earfcn;
+};
+
 } // namespace srsue
 
 #endif // SRSLTE_RRC_PROCEDURES_H

srsue/src/stack/rrc/rrc.cc

@@ -89,6 +89,7 @@ rrc::rrc(stack_interface_rrc* stack_) :
   last_state(RRC_STATE_CONNECTED),
   drb_up(false),
   rrc_log("RRC"),
+  phy_cell_selector(this),
   cell_searcher(this),
   si_acquirer(this),
   serv_cell_cfg(this),
@@ -99,6 +100,7 @@ rrc::rrc(stack_interface_rrc* stack_) :
   plmn_searcher(this),
   cell_reselector(this),
   connection_reest(this),
+  ho_prep_proc(this),
   serving_cell(unique_cell_t(new cell_t()))
 {
   measurements = std::unique_ptr<rrc_meas>(new rrc_meas());
@@ -1042,103 +1044,6 @@ void rrc::send_rrc_con_reconfig_complete()
   send_ul_dcch_msg(RB_ID_SRB1, ul_dcch_msg);
 }
 
-bool rrc::ho_prepare()
-{
-  if (pending_mob_reconf) {
-    rrc_conn_recfg_r8_ies_s* mob_reconf_r8 = &mob_reconf.crit_exts.c1().rrc_conn_recfg_r8();
-    mob_ctrl_info_s*         mob_ctrl_info = &mob_reconf_r8->mob_ctrl_info;
-    rrc_log->info("Processing HO command to target PCell=%d\n", mob_ctrl_info->target_pci);
-
-    uint32_t target_earfcn = (mob_ctrl_info->carrier_freq_present) ? mob_ctrl_info->carrier_freq.dl_carrier_freq
-                                                                   : serving_cell->get_earfcn();
-
-    if (not has_neighbour_cell(target_earfcn, mob_ctrl_info->target_pci)) {
-      rrc_log->console("Received HO command to unknown PCI=%d\n", mob_ctrl_info->target_pci);
-      rrc_log->error(
-          "Could not find target cell earfcn=%d, pci=%d\n", serving_cell->get_earfcn(), mob_ctrl_info->target_pci);
-      return false;
-    }
-
-    // Section 5.3.5.4
-    t310.stop();
-    t304.set(mob_ctrl_info->t304.to_number(), [this](uint32_t tid) { timer_expired(tid); });
-
-    // Save serving cell and current configuration
-    ho_src_cell = *serving_cell;
-    mac_interface_rrc::ue_rnti_t uernti;
-    mac->get_rntis(&uernti);
-    ho_src_rnti = uernti.crnti;
-
-    // Reset/Reestablish stack
-    pdcp->reestablish();
-    rlc->reestablish();
-    mac->wait_uplink();
-    mac->clear_rntis();
-    mac->reset();
-    phy->reset();
-
-    mac->set_ho_rnti(mob_ctrl_info->new_ue_id.to_number(), mob_ctrl_info->target_pci);
-
-    // Apply common config, but do not send to lower layers if Dedicated is present (to avoid sending twice)
-    apply_rr_config_common(&mob_ctrl_info->rr_cfg_common, !mob_reconf_r8->rr_cfg_ded_present);
-
-    if (mob_reconf_r8->rr_cfg_ded_present) {
-      apply_rr_config_dedicated(&mob_reconf_r8->rr_cfg_ded);
-    }
-
-    cell_t* target_cell = get_neighbour_cell_handle(target_earfcn, mob_ctrl_info->target_pci);
-    if (not phy->cell_select(&target_cell->phy_cell)) {
-      rrc_log->error("Could not synchronize with target cell %s. Removing cell and trying to return to source %s\n",
-                     target_cell->to_string().c_str(),
-                     serving_cell->to_string().c_str());
-
-      // Remove cell from list to avoid cell re-selection, picking the same cell
-      target_cell->set_rsrp(-INFINITY);
-
-      return false;
-    }
-
-    set_serving_cell(target_cell->phy_cell, false);
-
-    // Extract and apply scell config if any
-    apply_scell_config(mob_reconf_r8);
-
-    if (mob_ctrl_info->rach_cfg_ded_present) {
-      rrc_log->info("Starting non-contention based RA with preamble_idx=%d, mask_idx=%d\n",
-                    mob_ctrl_info->rach_cfg_ded.ra_preamb_idx,
-                    mob_ctrl_info->rach_cfg_ded.ra_prach_mask_idx);
-      mac->start_noncont_ho(mob_ctrl_info->rach_cfg_ded.ra_preamb_idx, mob_ctrl_info->rach_cfg_ded.ra_prach_mask_idx);
-    } else {
-      rrc_log->info("Starting contention-based RA\n");
-      mac->start_cont_ho();
-    }
-
-    int ncc = -1;
-    if (mob_reconf_r8->security_cfg_ho_present) {
-      ncc = mob_reconf_r8->security_cfg_ho.handov_type.intra_lte().next_hop_chaining_count;
-      if (mob_reconf_r8->security_cfg_ho.handov_type.intra_lte().key_change_ind) {
-        rrc_log->console("keyChangeIndicator in securityConfigHO not supported\n");
-        return false;
-      }
-      if (mob_reconf_r8->security_cfg_ho.handov_type.intra_lte().security_algorithm_cfg_present) {
-        sec_cfg.cipher_algo = (CIPHERING_ALGORITHM_ID_ENUM)mob_reconf_r8->security_cfg_ho.handov_type.intra_lte()
-                                  .security_algorithm_cfg.ciphering_algorithm.to_number();
-        sec_cfg.integ_algo = (INTEGRITY_ALGORITHM_ID_ENUM)mob_reconf_r8->security_cfg_ho.handov_type.intra_lte()
-                                 .security_algorithm_cfg.integrity_prot_algorithm.to_number();
-        rrc_log->info("Changed Ciphering to %s and Integrity to %s\n",
-                      ciphering_algorithm_id_text[sec_cfg.cipher_algo],
-                      integrity_algorithm_id_text[sec_cfg.integ_algo]);
-      }
-    }
-
-    usim->generate_as_keys_ho(mob_ctrl_info->target_pci, serving_cell->get_earfcn(), ncc, &sec_cfg);
-
-    pdcp->config_security_all(sec_cfg);
-    send_rrc_con_reconfig_complete();
-  }
-  return true;
-}
-
 void rrc::ho_ra_completed(bool ra_successful)
 {
   cmd_msg_t msg;
@@ -1170,39 +1075,17 @@ void rrc::process_ho_ra_completed(bool ra_successful)
 
 bool rrc::con_reconfig_ho(rrc_conn_recfg_s* reconfig)
 {
-  rrc_conn_recfg_r8_ies_s* mob_reconf_r8 = &reconfig->crit_exts.c1().rrc_conn_recfg_r8();
-  if (mob_reconf_r8->mob_ctrl_info.target_pci == serving_cell->get_pci()) {
-    rrc_log->console("Warning: Received HO command to own cell\n");
-    rrc_log->warning("Received HO command to own cell\n");
-    return false;
-  }
-
-  rrc_log->info("Received HO command to target PCell=%d\n", mob_reconf_r8->mob_ctrl_info.target_pci);
-  rrc_log->console("Received HO command to target PCell=%d, NCC=%d\n",
-                   mob_reconf_r8->mob_ctrl_info.target_pci,
-                   mob_reconf_r8->security_cfg_ho.handov_type.intra_lte().next_hop_chaining_count);
-
   // store mobilityControlInfo
   mob_reconf         = *reconfig;
   pending_mob_reconf = true;
 
-  start_ho();
-  return true;
-}
+  if (not ho_prep_proc.launch(*reconfig)) {
+    rrc_log->error("Unable to launch Handover Preparation procedure\n");
+    return false;
+  }
+  callback_list.add_proc(ho_prep_proc);
 
-void rrc::start_ho()
-{
-  callback_list.add_task([this]() {
-    if (state != RRC_STATE_CONNECTED) {
-      rrc_log->info("HO interrupted, since RRC is no longer in connected state\n");
-      return srslte::proc_outcome_t::success;
-    }
-    if (not ho_prepare()) {
-      con_reconfig_failed();
-      return srslte::proc_outcome_t::error;
-    }
-    return srslte::proc_outcome_t::success;
-  });
+  return true;
 }
 
 void rrc::start_go_idle()
@@ -1275,6 +1158,7 @@ bool rrc::con_reconfig(rrc_conn_recfg_s* reconfig)
 // HO failure from T304 expiry 5.3.5.6
 void rrc::ho_failed()
 {
+  ho_prep_proc.trigger(ho_prep_proc::t304_expiry{});
   start_con_restablishment(reest_cause_e::ho_fail);
 }
 
@@ -1304,9 +1188,7 @@ void rrc::handle_rrc_con_reconfig(uint32_t lcid, rrc_conn_recfg_s* reconfig)
 
   rrc_conn_recfg_r8_ies_s* reconfig_r8 = &reconfig->crit_exts.c1().rrc_conn_recfg_r8();
   if (reconfig_r8->mob_ctrl_info_present) {
-    if (!con_reconfig_ho(reconfig)) {
-      con_reconfig_failed();
-    }
+    con_reconfig_ho(reconfig);
   } else {
     if (!con_reconfig(reconfig)) {
       con_reconfig_failed();
@@ -1401,9 +1283,7 @@ void rrc::cell_search_completed(const phy_interface_rrc_lte::cell_search_ret_t&
 
 void rrc::cell_select_completed(bool cs_ret)
 {
-  cell_select_event_t ev{cs_ret};
-  cell_searcher.trigger(ev);
-  cell_selector.trigger(ev);
+  phy_cell_selector.trigger(cell_select_event_t{cs_ret});
 }
 
 /*******************************************************************************

srsue/src/stack/rrc/rrc_procedures.cc

@@ -20,6 +20,7 @@
  */
 
 #include "srsue/hdr/stack/rrc/rrc_procedures.h"
+#include "srslte/common/security.h"
 #include "srslte/common/tti_point.h"
 #include <inttypes.h> // for printing uint64_t
 
@@ -33,6 +34,36 @@ namespace srsue {
 using srslte::proc_outcome_t;
 using srslte::tti_point;
 
+/**************************************
+ *    PHY Cell Select Procedure
+ *************************************/
+
+rrc::phy_cell_select_proc::phy_cell_select_proc(rrc* parent_) : rrc_ptr(parent_) {}
+
+srslte::proc_outcome_t rrc::phy_cell_select_proc::init(const cell_t& target_cell_)
+{
+  target_cell = &target_cell_;
+  Info("Starting for %s\n", target_cell->to_string().c_str());
+  rrc_ptr->stack->start_cell_select(&target_cell->phy_cell);
+  return proc_outcome_t::yield;
+}
+
+srslte::proc_outcome_t rrc::phy_cell_select_proc::react(cell_select_event_t ev)
+{
+  if (not ev.cs_ret) {
+    Error("Couldn't select new serving cell\n");
+    return proc_outcome_t::error;
+  }
+  return proc_outcome_t::success;
+}
+
+void rrc::phy_cell_select_proc::then(const srslte::proc_state_t& result)
+{
+  // Warn other procedures that depend on this procedure
+  rrc_ptr->cell_searcher.trigger(cell_select_event_t{result.is_success()});
+  rrc_ptr->cell_selector.trigger(cell_select_event_t{result.is_success()});
+}
+
 /**************************************
  *       Cell Search Procedure
  *************************************/
@@ -92,7 +123,10 @@ proc_outcome_t rrc::cell_search_proc::handle_cell_found(const phy_interface_rrc_
 
   // set new serving cell in PHY
   state = state_t::phy_cell_select;
-  rrc_ptr->stack->start_cell_select(&rrc_ptr->serving_cell->phy_cell);
+  if (not rrc_ptr->phy_cell_selector.launch(rrc_ptr->serving_cell->phy_cell)) {
+    Error("Couldn't start phy cell selection\n");
+    return proc_outcome_t::error;
+  }
   return proc_outcome_t::yield;
 }
 
@@ -366,8 +400,7 @@ proc_outcome_t rrc::si_acquire_proc::react(si_acq_timer_expired ev)
 rrc::serving_cell_config_proc::serving_cell_config_proc(rrc* parent_) :
   rrc_ptr(parent_),
   log_h(srslte::logmap::get("RRC"))
-{
-}
+{}
 
 /*
  * Retrieves all required SIB or configures them if already retrieved before
@@ -508,7 +541,10 @@ proc_outcome_t rrc::cell_selection_proc::start_cell_selection()
       Info("Selected cell: %s\n", rrc_ptr->serving_cell->to_string().c_str());
 
       state = search_state_t::cell_selection;
-      rrc_ptr->stack->start_cell_select(&rrc_ptr->serving_cell->phy_cell);
+      if (not rrc_ptr->phy_cell_selector.launch(rrc_ptr->serving_cell->phy_cell)) {
+        Error("Failed to launch PHY Cell Selection\n");
+        return proc_outcome_t::error;
+      }
       return proc_outcome_t::yield;
     }
   }
@@ -735,8 +771,7 @@ void rrc::plmn_search_proc::then(const srslte::proc_state_t& result) const
 rrc::connection_request_proc::connection_request_proc(rrc* parent_) :
   rrc_ptr(parent_),
   log_h(srslte::logmap::get("RRC"))
-{
-}
+{}
 
 proc_outcome_t rrc::connection_request_proc::init(srslte::establishment_cause_t cause_,
                                                   srslte::unique_byte_buffer_t  dedicated_info_nas_)
@@ -1292,4 +1327,158 @@ proc_outcome_t rrc::connection_reest_proc::step()
   return ret;
 }
 
+/**************************************
+ *    Handover Preparation Procedure
+ *************************************/
+
+rrc::ho_prep_proc::ho_prep_proc(srsue::rrc* rrc_) : rrc_ptr(rrc_) {}
+
+srslte::proc_outcome_t rrc::ho_prep_proc::init(const asn1::rrc::rrc_conn_recfg_s& rrc_reconf)
+{
+  Info("Starting...\n");
+  recfg_r8                                  = rrc_reconf.crit_exts.c1().rrc_conn_recfg_r8();
+  asn1::rrc::mob_ctrl_info_s* mob_ctrl_info = &recfg_r8.mob_ctrl_info;
+
+  if (recfg_r8.mob_ctrl_info.target_pci == rrc_ptr->serving_cell->get_pci()) {
+    rrc_ptr->rrc_log->console("Warning: Received HO command to own cell\n");
+    Warning("Received HO command to own cell\n");
+    return proc_outcome_t::error;
+  }
+
+  Info("Received HO command to target PCell=%d\n", recfg_r8.mob_ctrl_info.target_pci);
+  rrc_ptr->rrc_log->console("Received HO command to target PCell=%d, NCC=%d\n",
+                            recfg_r8.mob_ctrl_info.target_pci,
+                            recfg_r8.security_cfg_ho.handov_type.intra_lte().next_hop_chaining_count);
+
+  target_earfcn = (mob_ctrl_info->carrier_freq_present) ? mob_ctrl_info->carrier_freq.dl_carrier_freq
+                                                        : rrc_ptr->serving_cell->get_earfcn();
+
+  if (not rrc_ptr->has_neighbour_cell(target_earfcn, mob_ctrl_info->target_pci)) {
+    rrc_ptr->rrc_log->console("Received HO command to unknown PCI=%d\n", mob_ctrl_info->target_pci);
+    Error("Could not find target cell earfcn=%d, pci=%d\n",
+          rrc_ptr->serving_cell->get_earfcn(),
+          mob_ctrl_info->target_pci);
+    return proc_outcome_t::error;
+  }
+
+  // Section 5.3.5.4
+  rrc_ptr->t310.stop();
+  rrc_ptr->t304.set(mob_ctrl_info->t304.to_number(), [this](uint32_t tid) { rrc_ptr->timer_expired(tid); });
+
+  // Save serving cell and current configuration
+  ho_src_cell = *rrc_ptr->serving_cell;
+  mac_interface_rrc::ue_rnti_t uernti;
+  rrc_ptr->mac->get_rntis(&uernti);
+  ho_src_rnti = uernti.crnti;
+
+  // Reset/Reestablish stack
+  rrc_ptr->pdcp->reestablish();
+  rrc_ptr->rlc->reestablish();
+  rrc_ptr->mac->wait_uplink();
+  rrc_ptr->mac->clear_rntis();
+  rrc_ptr->mac->reset();
+  rrc_ptr->phy->reset();
+
+  rrc_ptr->mac->set_ho_rnti(mob_ctrl_info->new_ue_id.to_number(), mob_ctrl_info->target_pci);
+
+  // Apply common config, but do not send to lower layers if Dedicated is present (to avoid sending twice)
+  rrc_ptr->apply_rr_config_common(&mob_ctrl_info->rr_cfg_common, !recfg_r8.rr_cfg_ded_present);
+
+  if (recfg_r8.rr_cfg_ded_present) {
+    rrc_ptr->apply_rr_config_dedicated(&recfg_r8.rr_cfg_ded);
+  }
+
+  cell_t* target_cell = rrc_ptr->get_neighbour_cell_handle(target_earfcn, recfg_r8.mob_ctrl_info.target_pci);
+  if (not rrc_ptr->phy_cell_selector.launch(*target_cell)) {
+    Error("Failed to launch the selection of target cell %s\n", target_cell->to_string().c_str());
+    return proc_outcome_t::error;
+  }
+  return proc_outcome_t::yield;
+}
+
+srslte::proc_outcome_t rrc::ho_prep_proc::react(srsue::cell_select_event_t ev)
+{
+  // Check if cell has not been deleted in the meantime
+  cell_t* target_cell = rrc_ptr->get_neighbour_cell_handle(target_earfcn, recfg_r8.mob_ctrl_info.target_pci);
+  if (target_cell == nullptr) {
+    Error("Cell removed from list of neighbours. Aborting handover preparation\n");
+    return proc_outcome_t::error;
+  }
+
+  if (not ev.cs_ret) {
+    Error("Could not synchronize with target cell %s. Removing cell and trying to return to source %s\n",
+          target_cell->to_string().c_str(),
+          rrc_ptr->serving_cell->to_string().c_str());
+
+    // Remove cell from list to avoid cell re-selection, picking the same cell
+    target_cell->set_rsrp(-INFINITY);
+    return proc_outcome_t::error;
+  }
+
+  rrc_ptr->set_serving_cell(target_cell->phy_cell, false);
+
+  // Extract and apply scell config if any
+  rrc_ptr->apply_scell_config(&recfg_r8);
+
+  if (recfg_r8.mob_ctrl_info.rach_cfg_ded_present) {
+    Info("Starting non-contention based RA with preamble_idx=%d, mask_idx=%d\n",
+         recfg_r8.mob_ctrl_info.rach_cfg_ded.ra_preamb_idx,
+         recfg_r8.mob_ctrl_info.rach_cfg_ded.ra_prach_mask_idx);
+    rrc_ptr->mac->start_noncont_ho(recfg_r8.mob_ctrl_info.rach_cfg_ded.ra_preamb_idx,
+                                   recfg_r8.mob_ctrl_info.rach_cfg_ded.ra_prach_mask_idx);
+  } else {
+    Info("Starting contention-based RA\n");
+    rrc_ptr->mac->start_cont_ho();
+  }
+
+  int ncc = -1;
+  if (recfg_r8.security_cfg_ho_present) {
+    auto& sec_intralte = recfg_r8.security_cfg_ho.handov_type.intra_lte();
+    ncc                = sec_intralte.next_hop_chaining_count;
+    if (sec_intralte.key_change_ind) {
+      rrc_ptr->rrc_log->console("keyChangeIndicator in securityConfigHO not supported\n");
+      return proc_outcome_t::error;
+    }
+    if (sec_intralte.security_algorithm_cfg_present) {
+      rrc_ptr->sec_cfg.cipher_algo =
+          (srslte::CIPHERING_ALGORITHM_ID_ENUM)sec_intralte.security_algorithm_cfg.ciphering_algorithm.to_number();
+      rrc_ptr->sec_cfg.integ_algo =
+          (srslte::INTEGRITY_ALGORITHM_ID_ENUM)sec_intralte.security_algorithm_cfg.integrity_prot_algorithm.to_number();
+      Info("Changed Ciphering to %s and Integrity to %s\n",
+           srslte::ciphering_algorithm_id_text[rrc_ptr->sec_cfg.cipher_algo],
+           srslte::integrity_algorithm_id_text[rrc_ptr->sec_cfg.integ_algo]);
+    }
+  }
+
+  rrc_ptr->usim->generate_as_keys_ho(
+      recfg_r8.mob_ctrl_info.target_pci, rrc_ptr->serving_cell->get_earfcn(), ncc, &rrc_ptr->sec_cfg);
+
+  rrc_ptr->pdcp->config_security_all(rrc_ptr->sec_cfg);
+  return proc_outcome_t::success;
+}
+
+srslte::proc_outcome_t rrc::ho_prep_proc::step()
+{
+  if (rrc_ptr->state != RRC_STATE_CONNECTED) {
+    Info("HO interrupted, since RRC is no longer in connected state\n");
+    return srslte::proc_outcome_t::error;
+  }
+  return proc_outcome_t::success;
+}
+
+srslte::proc_outcome_t rrc::ho_prep_proc::react(t304_expiry ev)
+{
+  Info("HO preparation timed out.\n");
+  return proc_outcome_t::error;
+}
+
+void rrc::ho_prep_proc::then(const srslte::proc_state_t& result)
+{
+  if (result.is_error()) {
+    rrc_ptr->con_reconfig_failed();
+  } else {
+    rrc_ptr->send_rrc_con_reconfig_complete();
+  }
+}
+
 } // namespace srsue