set last_submitted_pdcp_rx_sn to -1 of the next ul rx sn

lib/include/srslte/asn1/rrc_utils.h

@@ -75,7 +75,6 @@ struct ue_eutra_cap_s;
  *  Conversion Helpers
  ***********************/
 namespace srslte {
-
 plmn_id_t make_plmn_id_t(const asn1::rrc::plmn_id_s& asn1_type);
 void      to_asn1(asn1::rrc::plmn_id_s* asn1_type, const plmn_id_t& cfg);
 plmn_id_t make_plmn_id_t(const asn1::fixed_octstring<3, true>& asn1_type);
@@ -96,6 +95,7 @@ void         to_asn1(asn1::rrc::rlc_cfg_c* asn1_type, const rlc_config_t& cfg);
  **************************/
 srslte::pdcp_config_t make_srb_pdcp_config_t(const uint8_t bearer_id, bool is_ue);
 srslte::pdcp_config_t make_drb_pdcp_config_t(const uint8_t bearer_id, bool is_ue);
+uint8_t               get_pdcp_drb_sn_len(const asn1::rrc::pdcp_cfg_s& pdcp_cfg);
 srslte::pdcp_config_t
 make_drb_pdcp_config_t(const uint8_t bearer_id, bool is_ue, const asn1::rrc::pdcp_cfg_s& pdcp_cfg);
 

lib/src/asn1/rrc_utils.cc

@@ -224,6 +224,17 @@ srslte::pdcp_config_t make_drb_pdcp_config_t(const uint8_t bearer_id, bool is_ue
   return cfg;
 }
 
+uint8_t get_pdcp_drb_sn_len(const pdcp_cfg_s& pdcp_cfg)
+{
+  uint8_t sn_len = srslte::PDCP_SN_LEN_12;
+  if (pdcp_cfg.rlc_um_present) {
+    if (pdcp_cfg.rlc_um.pdcp_sn_size.value == pdcp_cfg_s::rlc_um_s_::pdcp_sn_size_e_::len7bits) {
+      sn_len = srslte::PDCP_SN_LEN_7;
+    }
+  }
+  return sn_len;
+}
+
 srslte::pdcp_config_t make_drb_pdcp_config_t(const uint8_t bearer_id, bool is_ue, const asn1::rrc::pdcp_cfg_s& pdcp_cfg)
 {
   // TODO: complete config processing
@@ -250,12 +261,7 @@ srslte::pdcp_config_t make_drb_pdcp_config_t(const uint8_t bearer_id, bool is_ue
     }
   }
 
-  uint8_t sn_len = srslte::PDCP_SN_LEN_12;
-  if (pdcp_cfg.rlc_um_present) {
-    if (pdcp_cfg.rlc_um.pdcp_sn_size.value == pdcp_cfg_s::rlc_um_s_::pdcp_sn_size_e_::len7bits) {
-      sn_len = srslte::PDCP_SN_LEN_7;
-    }
-  }
+  uint8_t sn_len = get_pdcp_drb_sn_len(pdcp_cfg);
 
   bool status_report_required = false;
   if (pdcp_cfg.rlc_am_present) {

srsenb/src/stack/rrc/rrc_mobility.cc

@@ -887,7 +887,9 @@ void rrc::ue::rrc_mobility::handle_status_transfer(s1_target_ho_st& s, const sta
     drb_state.next_pdcp_tx_sn           = erab_item.dl_coun_tvalue.pdcp_sn;
     drb_state.rx_hfn                    = erab_item.ul_coun_tvalue.hfn;
     drb_state.next_pdcp_rx_sn           = erab_item.ul_coun_tvalue.pdcp_sn;
-    drb_state.last_submitted_pdcp_rx_sn = erab_item.ul_coun_tvalue.pdcp_sn;
+    uint8_t  sn_len                     = srslte::get_pdcp_drb_sn_len(drb_it->pdcp_cfg);
+    uint32_t maximum_pdcp_sn            = (1u << sn_len) - 1u;
+    drb_state.last_submitted_pdcp_rx_sn = std::max(erab_item.ul_coun_tvalue.pdcp_sn - 1u, maximum_pdcp_sn);
     logger.info("Setting lcid=%d PDCP state to {Tx SN: %d, Rx SN: %d}",
                 drb_it->lc_ch_id,
                 drb_state.next_pdcp_tx_sn,