RLC failure to deliver notifications and discard timer limits to 1500ms (#2368)

* Added interfaces for the RLC to notify the PDCP of failure to transmit
SDU

* Limit discard timer to 1500ms, to avoid issues of lingering SDUs in the undeliverd_sdus_queue.

* Fix bug in early exit of notify_delivery and notify_failure

* fix compilation issue in rlc-pdcp notification

Co-authored-by: Francisco <francisco.paisana@softwareradiosystems.com>

lib/include/srslte/interfaces/enb_pdcp_interfaces.h

@@ -54,6 +54,7 @@ public:
   /* RLC calls PDCP to push a PDCP PDU. */
   virtual void write_pdu(uint16_t rnti, uint32_t lcid, srslte::unique_byte_buffer_t pdu)            = 0;
   virtual void notify_delivery(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& pdcp_sns) = 0;
+  virtual void notify_failure(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& pdcp_sns)  = 0;
 };
 
 } // namespace srsenb

lib/include/srslte/interfaces/gnb_interfaces.h

@@ -84,6 +84,7 @@ public:
   /* RLC calls PDCP to push a PDCP PDU. */
   virtual void write_pdu(uint16_t rnti, uint32_t lcid, srslte::unique_byte_buffer_t sdu)            = 0;
   virtual void notify_delivery(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& tx_count) = 0;
+  virtual void notify_failure(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& tx_count)  = 0;
 };
 
 class pdcp_interface_rrc_nr

lib/include/srslte/interfaces/ue_interfaces.h

@@ -306,6 +306,7 @@ public:
   virtual void write_pdu_pcch(srslte::unique_byte_buffer_t sdu)                     = 0;
   virtual void write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t sdu)       = 0;
   virtual void notify_delivery(uint32_t lcid, const std::vector<uint32_t>& pdcp_sn) = 0;
+  virtual void notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sn)  = 0;
 };
 
 class pdcp_interface_gw

lib/include/srslte/upper/pdcp.h

@@ -59,6 +59,7 @@ public:
   void write_pdu_bcch_dlsch(unique_byte_buffer_t sdu) override;
   void write_pdu_pcch(unique_byte_buffer_t sdu) override;
   void notify_delivery(uint32_t lcid, const std::vector<uint32_t>& pdcp_sn) override;
+  void notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sn) override;
 
   // eNB-only methods
   std::map<uint32_t, srslte::unique_byte_buffer_t> get_buffered_pdus(uint32_t lcid);

lib/include/srslte/upper/pdcp_entity_base.h

@@ -113,7 +113,8 @@ public:
 
   // RLC interface
   virtual void write_pdu(unique_byte_buffer_t pdu)                    = 0;
-  virtual void notify_delivery(const std::vector<uint32_t>& tx_count) = 0;
+  virtual void notify_delivery(const std::vector<uint32_t>& pdcp_sns) = 0;
+  virtual void notify_failure(const std::vector<uint32_t>& pdcp_sns)  = 0;
 
   virtual void get_bearer_state(pdcp_lte_state_t* state)       = 0;
   virtual void set_bearer_state(const pdcp_lte_state_t& state) = 0;

lib/include/srslte/upper/pdcp_entity_lte.h

@@ -53,6 +53,7 @@ public:
 
   // RLC interface
   void write_pdu(unique_byte_buffer_t pdu) override;
+  void notify_failure(const std::vector<uint32_t>& pdcp_sns) override;
   void notify_delivery(const std::vector<uint32_t>& pdcp_sns) override;
 
   // Config helpers

lib/include/srslte/upper/pdcp_entity_nr.h

@@ -50,6 +50,7 @@ public:
   // RLC interface
   void write_pdu(unique_byte_buffer_t pdu) final;
   void notify_delivery(const std::vector<uint32_t>& tx_count) final;
+  void notify_failure(const std::vector<uint32_t>& tx_count) final;
 
   // State variable setters (should be used only for testing)
   void set_tx_next(uint32_t tx_next_) { tx_next = tx_next_; }

lib/src/upper/pdcp.cc

@@ -306,6 +306,15 @@ void pdcp::notify_delivery(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns)
   }
 }
 
+void pdcp::notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns)
+{
+  if (valid_lcid(lcid)) {
+    pdcp_array.at(lcid)->notify_failure(pdcp_sns);
+  } else {
+    logger.warning("Could not notify failure: lcid=%d, nof_sn=%ld.", lcid, pdcp_sns.size());
+  }
+}
+
 bool pdcp::valid_lcid(uint32_t lcid)
 {
   if (lcid >= SRSLTE_N_RADIO_BEARERS) {

lib/src/upper/pdcp_entity_lte.cc

@@ -60,6 +60,13 @@ pdcp_entity_lte::pdcp_entity_lte(srsue::rlc_interface_pdcp* rlc_,
   // Queue Helpers
   maximum_allocated_sns_window = (1 << cfg.sn_len) / 2;
 
+  if (is_drb() && not rlc->rb_is_um(lcid) && cfg.discard_timer == pdcp_discard_timer_t::infinity) {
+    logger.warning(
+        "Setting discard timer to 1500ms, to avoid issues with lingering SDUs in the Unacknowledged SDUs map. LCID=%d",
+        lcid);
+    cfg.discard_timer = pdcp_discard_timer_t::ms1500;
+  }
+
   logger.info("Init %s with bearer ID: %d", rrc->get_rb_name(lcid).c_str(), cfg.bearer_id);
   logger.info("SN len bits: %d, SN len bytes: %d, reordering window: %d, Maximum SN: %d, discard timer: %d ms",
               cfg.sn_len,
@@ -642,21 +649,19 @@ void pdcp_entity_lte::discard_callback::operator()(uint32_t timer_id)
 }
 
 /****************************************************************************
- * Handle delivery notifications from RLC
+ * Handle delivery/failure notifications from RLC
  ***************************************************************************/
 void pdcp_entity_lte::notify_delivery(const std::vector<uint32_t>& pdcp_sns)
 {
   logger.info("Received delivery notification from RLC. Number of PDU notified=%ld", pdcp_sns.size());
 
   for (uint32_t sn : pdcp_sns) {
-    logger.debug("Received delivery notification for SN=%d", sn);
+    logger.debug("Delivery notification received for PDU with SN=%d", sn);
     // Find undelivered PDU info
     std::map<uint32_t, unique_byte_buffer_t>::iterator it = undelivered_sdus_queue.find(sn);
     if (it == undelivered_sdus_queue.end()) {
       logger.warning("Could not find PDU for delivery notification. Notified SN=%d", sn);
-      return;
+    } else {
-    }
-
       // Metrics
       tx_pdu_ack_latency_ms.push(std::chrono::duration_cast<std::chrono::milliseconds>(
                                      std::chrono::high_resolution_clock::now() - it->second->get_timestamp())
@@ -664,10 +669,29 @@ void pdcp_entity_lte::notify_delivery(const std::vector<uint32_t>& pdcp_sns)
       metrics.num_tx_acked_bytes += it->second->N_bytes;
       metrics.num_tx_buffered_pdus_bytes -= it->second->N_bytes;
 
-    // If ACK'ed bytes are equal to (or exceed) PDU size, remove PDU and disarm timer.
+      // Remove PDU and disarm timer.
+      undelivered_sdus_queue.erase(sn);
+      stop_discard_timer(sn);
+    }
+  }
+}
+
+void pdcp_entity_lte::notify_failure(const std::vector<uint32_t>& pdcp_sns)
+{
+  logger.info("Received failure notification from RLC. Number of PDU notified=%ld", pdcp_sns.size());
+
+  for (uint32_t sn : pdcp_sns) {
+    logger.info("Failure notification received for PDU with SN=%d", sn);
+    // Find undelivered PDU info
+    std::map<uint32_t, unique_byte_buffer_t>::iterator it = undelivered_sdus_queue.find(sn);
+    if (it == undelivered_sdus_queue.end()) {
+      logger.info("Could not find PDU for failure notification. Notified SN=%d", sn);
+    } else {
+      // Remove PDU and disarm timer.
       undelivered_sdus_queue.erase(sn);
       stop_discard_timer(sn);
     }
+  }
 }
 
 /****************************************************************************

lib/src/upper/pdcp_entity_nr.cc

@@ -202,12 +202,17 @@ void pdcp_entity_nr::write_pdu(unique_byte_buffer_t pdu)
   }
 }
 
-// Notification of delivery
+// Notification of delivery/failure
 void pdcp_entity_nr::notify_delivery(const std::vector<uint32_t>& pdcp_sns)
 {
   logger.debug("Received delivery notification from RLC. Nof SNs=%ld", pdcp_sns.size());
 }
 
+void pdcp_entity_nr::notify_failure(const std::vector<uint32_t>& pdcp_sns)
+{
+  logger.debug("Received failure notification from RLC. Nof SNs=%ld", pdcp_sns.size());
+}
+
 /*
  * Packing / Unpacking Helpers
  */

lib/src/upper/rlc_am_lte.cc

@@ -626,6 +626,7 @@ int rlc_am_lte::rlc_am_lte_tx::build_retx_pdu(uint8_t* payload, uint32_t nof_byt
   if (tx_window[retx.sn].retx_count >= cfg.max_retx_thresh) {
     logger.warning("%s Signaling max number of reTx=%d for for SN=%d", RB_NAME, tx_window[retx.sn].retx_count, retx.sn);
     parent->rrc->max_retx_attempted();
+    parent->pdcp->notify_failure(parent->lcid, tx_window[retx.sn].pdcp_sns);
   }
 
   logger.info(payload,
@@ -873,11 +874,11 @@ int rlc_am_lte::rlc_am_lte_tx::build_data_pdu(uint8_t* payload, uint32_t nof_byt
       logger.error("Could not find PDCP SN in SDU info queue (segment). PDCP_SN=%d", tx_sdu->md.pdcp_sn);
       return 0;
     }
-    undelivered_sdu_info_queue.at(tx_sdu->md.pdcp_sn).rlc_sn_info_list.push_back({header.sn, false});
+    info_it->second.rlc_sn_info_list.push_back({header.sn, false});
     pdcp_sns.push_back(tx_sdu->md.pdcp_sn);
     if (tx_sdu->N_bytes == 0) {
       logger.debug("%s Complete SDU scheduled for tx.", RB_NAME);
-      undelivered_sdu_info_queue[tx_sdu->md.pdcp_sn].fully_txed = true;
+      info_it->second.fully_txed = true;
       tx_sdu.reset();
     }
     if (pdu_space > to_move) {

lib/test/upper/rlc_am_test.cc

@@ -64,6 +64,11 @@ public:
       notified_counts[pdcp_sn] += 1;
     }
   }
+  void notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sn_vec)
+  {
+    assert(lcid == 1);
+    // TODO
+  }
 
   // RRC interface
   void        max_retx_attempted() {}

lib/test/upper/rlc_common_test.cc

@@ -47,6 +47,7 @@ public:
     sdus[n_sdus++] = std::move(sdu);
   }
   void notify_delivery(uint32_t lcid, const std::vector<uint32_t>& pdcp_sn) {}
+  void notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sn) {}
   void write_pdu_bcch_bch(unique_byte_buffer_t sdu) {}
   void write_pdu_bcch_dlsch(unique_byte_buffer_t sdu) {}
   void write_pdu_pcch(unique_byte_buffer_t sdu) {}

lib/test/upper/rlc_stress_test.cc

@@ -352,6 +352,7 @@ public:
   void write_pdu_pcch(unique_byte_buffer_t sdu) {}
   void write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t sdu) {}
   void notify_delivery(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns) {}
+  void notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns) {}
 
   // RRC interface
   void        max_retx_attempted() {}

lib/test/upper/rlc_test_common.h

@@ -50,6 +50,7 @@ public:
   void write_pdu_pcch(unique_byte_buffer_t sdu) {}
   void write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t sdu) { sdus.push_back(std::move(sdu)); }
   void notify_delivery(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns) {}
+  void notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns) {}
 
   // RRC interface
   void        max_retx_attempted() {}

srsenb/hdr/stack/upper/pdcp.h

@@ -38,6 +38,7 @@ public:
   // pdcp_interface_rlc
   void write_pdu(uint16_t rnti, uint32_t lcid, srslte::unique_byte_buffer_t sdu) override;
   void notify_delivery(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& pdcp_sn) override;
+  void notify_failure(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& pdcp_sn) override;
   void write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t sdu) {}
 
   // pdcp_interface_rrc

srsenb/hdr/stack/upper/pdcp_nr.h

@@ -41,6 +41,7 @@ public:
   // pdcp_interface_rlc_nr
   void write_pdu(uint16_t rnti, uint32_t lcid, srslte::unique_byte_buffer_t sdu);
   void notify_delivery(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& tx_count);
+  void notify_failure(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& tx_count);
   void write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t sdu) {}
 
   // pdcp_interface_rrc_nr

srsenb/hdr/stack/upper/rlc.h

@@ -72,6 +72,7 @@ private:
   public:
     void        write_pdu(uint32_t lcid, srslte::unique_byte_buffer_t sdu);
     void        notify_delivery(uint32_t lcid, const std::vector<uint32_t>& tx_count);
+    void        notify_failure(uint32_t lcid, const std::vector<uint32_t>& tx_count);
     void        write_pdu_bcch_bch(srslte::unique_byte_buffer_t sdu);
     void        write_pdu_bcch_dlsch(srslte::unique_byte_buffer_t sdu);
     void        write_pdu_pcch(srslte::unique_byte_buffer_t sdu);

srsenb/hdr/stack/upper/rlc_nr.h

@@ -64,6 +64,7 @@ private:
   public:
     void        write_pdu(uint32_t lcid, srslte::unique_byte_buffer_t sdu);
     void        notify_delivery(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns);
+    void        notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns);
     void        write_pdu_bcch_bch(srslte::unique_byte_buffer_t sdu);
     void        write_pdu_bcch_dlsch(srslte::unique_byte_buffer_t sdu);
     void        write_pdu_pcch(srslte::unique_byte_buffer_t sdu);

srsenb/src/stack/upper/pdcp.cc

@@ -149,6 +149,14 @@ void pdcp::notify_delivery(uint16_t rnti, uint32_t lcid, const std::vector<uint3
     users[rnti].pdcp->notify_delivery(lcid, pdcp_sns);
   }
 }
+
+void pdcp::notify_failure(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& pdcp_sns)
+{
+  if (users.count(rnti)) {
+    users[rnti].pdcp->notify_failure(lcid, pdcp_sns);
+  }
+}
+
 void pdcp::write_sdu(uint16_t rnti, uint32_t lcid, srslte::unique_byte_buffer_t sdu, int pdcp_sn)
 {
   if (users.count(rnti)) {

srsenb/src/stack/upper/pdcp_nr.cc

@@ -108,6 +108,15 @@ void pdcp_nr::notify_delivery(uint16_t rnti, uint32_t lcid, const std::vector<ui
   }
 }
 
+void pdcp_nr::notify_failure(uint16_t rnti, uint32_t lcid, const std::vector<uint32_t>& pdcp_sns)
+{
+  if (users.count(rnti)) {
+    users[rnti].pdcp->notify_failure(lcid, pdcp_sns);
+  } else {
+    m_log->error("Can't notify Ack of PDU. RNTI=0x%X doesn't exist.\n", rnti);
+  }
+}
+
 void pdcp_nr::write_sdu(uint16_t rnti, uint32_t lcid, srslte::unique_byte_buffer_t sdu)
 {
   if (users.count(rnti)) {

srsenb/src/stack/upper/rlc.cc

@@ -274,6 +274,11 @@ void rlc::user_interface::notify_delivery(uint32_t lcid, const std::vector<uint3
   pdcp->notify_delivery(rnti, lcid, pdcp_sns);
 }
 
+void rlc::user_interface::notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns)
+{
+  pdcp->notify_failure(rnti, lcid, pdcp_sns);
+}
+
 void rlc::user_interface::write_pdu_bcch_bch(srslte::unique_byte_buffer_t sdu)
 {
   ERROR("Error: Received BCCH from ue=%d", rnti);

srsenb/src/stack/upper/rlc_nr.cc

@@ -212,4 +212,9 @@ void rlc_nr::user_interface::notify_delivery(uint32_t lcid, const std::vector<ui
   m_pdcp->notify_delivery(rnti, lcid, pdcp_sns);
 }
 
+void rlc_nr::user_interface::notify_failure(uint32_t lcid, const std::vector<uint32_t>& pdcp_sns)
+{
+  m_pdcp->notify_failure(rnti, lcid, pdcp_sns);
+}
+
 } // namespace srsenb