Starting to add boiler-plate code to support Discard at RLC.

lib/include/srslte/interfaces/ue_interfaces.h

@@ -287,7 +287,8 @@ public:
   /* PDCP calls RLC to push an RLC SDU. SDU gets placed into the RLC buffer and MAC pulls
    * RLC PDUs according to TB size. */
   virtual void write_sdu(uint32_t lcid, srslte::unique_byte_buffer_t sdu, bool blocking = true) = 0;
-  virtual bool rb_is_um(uint32_t lcid) = 0;
+  virtual void discard_sdu(uint32_t discard_sn)                                                 = 0;
+  virtual bool rb_is_um(uint32_t lcid)                                                          = 0;
 };
 
 //RLC interface for MAC

lib/include/srslte/upper/pdcp_entity_nr.h

@@ -134,7 +134,7 @@ public:
 
 private:
   pdcp_entity_nr* parent;
-  uint32_t        sn;
+  uint32_t        discard_sn;
 };
 
 /*

lib/include/srslte/upper/rlc_am_lte.h

@@ -80,6 +80,7 @@ public:
 
   // PDCP interface
   void write_sdu(unique_byte_buffer_t sdu, bool blocking = true);
+  void discard_sdu(uint32_t pdcp_sn);
 
   // MAC interface
   bool     has_data();
@@ -106,7 +107,8 @@ private:
     void stop();
 
     void write_sdu(unique_byte_buffer_t sdu, bool blocking);
-    int read_pdu(uint8_t *payload, uint32_t nof_bytes);
+    int  read_pdu(uint8_t* payload, uint32_t nof_bytes);
+    void discard_sdu(uint32_t discard_sn);
 
     bool     has_data();
     uint32_t get_buffer_state();

lib/include/srslte/upper/rlc_common.h

@@ -256,6 +256,7 @@ public:
 
   // PDCP interface
   virtual void write_sdu(unique_byte_buffer_t sdu, bool blocking) = 0;
+  virtual void discard_sdu(uint32_t discard_sn)                   = 0;
 
   // MAC interface
   virtual bool     has_data() = 0;

lib/include/srslte/upper/rlc_tm.h

@@ -54,6 +54,7 @@ public:
 
   // PDCP interface
   void write_sdu(unique_byte_buffer_t sdu, bool blocking);
+  void discard_sdu(uint32_t discard_sn);
 
   // MAC interface
   bool     has_data();

lib/include/srslte/upper/rlc_um_base.h

@@ -54,6 +54,7 @@ public:
 
   // PDCP interface
   void write_sdu(unique_byte_buffer_t sdu, bool blocking = true);
+  void discard_sdu(uint32_t discard_sn);
 
   // MAC interface
   bool     has_data();
@@ -78,6 +79,7 @@ protected:
     void             reestablish();
     void             empty_queue();
     void             write_sdu(unique_byte_buffer_t sdu);
+    void             discard_sdu(uint32_t discard_sn);
     void             try_write_sdu(unique_byte_buffer_t sdu);
     void             reset_metrics();
     bool             has_data();

lib/src/upper/rlc_am_lte.cc

@@ -122,6 +122,11 @@ void rlc_am_lte::write_sdu(unique_byte_buffer_t sdu, bool blocking)
   tx.write_sdu(std::move(sdu), blocking);
 }
 
+void rlc_am_lte::discard_sdu(uint32_t discard_sn)
+{
+  tx.discard_sdu(discard_sn);
+}
+
 /****************************************************************************
  * MAC interface
  ***************************************************************************/
@@ -337,8 +342,8 @@ void rlc_am_lte::rlc_am_lte_tx::write_sdu(unique_byte_buffer_t sdu, bool blockin
       tx_sdu_queue.write(std::move(sdu));
     } else {
       // non-blocking write
-      uint8_t* msg_ptr   = sdu->msg;
-      uint32_t nof_bytes = sdu->N_bytes;
+      uint8_t*                              msg_ptr   = sdu->msg;
+      uint32_t                              nof_bytes = sdu->N_bytes;
       std::pair<bool, unique_byte_buffer_t> ret       = tx_sdu_queue.try_write(std::move(sdu));
       if (ret.first) {
         log->info_hex(
@@ -358,6 +363,14 @@ void rlc_am_lte::rlc_am_lte_tx::write_sdu(unique_byte_buffer_t sdu, bool blockin
   }
 }
 
+void rlc_am_lte::rlc_am_lte_tx::discard_sdu(uint32_t discard_sn)
+{
+  if (!tx_enabled) {
+    return;
+  }
+  log->warning("Discard SDU not implemented yet\n");
+}
+
 int rlc_am_lte::rlc_am_lte_tx::read_pdu(uint8_t* payload, uint32_t nof_bytes)
 {
   pthread_mutex_lock(&mutex);

lib/src/upper/rlc_tm.cc

@@ -115,6 +115,14 @@ void rlc_tm::write_sdu(unique_byte_buffer_t sdu, bool blocking)
   }
 }
 
+void rlc_tm::discard_sdu(uint32_t discard_sn)
+{
+  if (!tx_enabled) {
+    return;
+  }
+  log->warning("SDU discard not implemented on RLC TM\n");
+}
+
 // MAC interface
 bool rlc_tm::has_data()
 {

lib/src/upper/rlc_um_base.cc

@@ -104,6 +104,15 @@ void rlc_um_base::write_sdu(unique_byte_buffer_t sdu, bool blocking)
   }
 }
 
+void rlc_um_base::discard_sdu(uint32_t discard_sn)
+{
+  if (not tx_enabled || not tx) {
+    log->debug("%s is currently deactivated. Ignoring SDU discard(SN %" PRIu32 ")\n", rb_name.c_str(), discard_sn);
+    metrics.num_dropped_sdus++;
+    return;
+  }
+  tx->discard_sdu(discard_sn);
+}
 /****************************************************************************
  * MAC interface
  ***************************************************************************/

srsenb/hdr/stack/upper/pdcp.h

@@ -66,6 +66,7 @@ private:
     srsenb::rlc_interface_pdcp* rlc;
     // rlc_interface_pdcp
     void write_sdu(uint32_t lcid, srslte::unique_byte_buffer_t sdu, bool blocking);
+    void discard_sdu(uint32_t discard_sn);
     bool rb_is_um(uint32_t lcid);
   };