rlc_um: fix counting of lost PDUs

* change try_push() return value to indicate whether the addition
  of the SDU to the tx queue was successful or not
* count lost PDUs

lib/include/srslte/upper/rlc_metrics.h

@@ -34,8 +34,8 @@ typedef struct {
   uint64_t num_tx_bytes;
   uint64_t num_rx_bytes;
 
-  uint32_t num_lost_pdus;
+  uint32_t num_lost_pdus;    //< Lost PDUs registered at Rx
-  uint32_t num_dropped_sdus;
+  uint32_t num_dropped_sdus; //< Count dropped SDUs at Tx due to bearer inactivity or empty buffer
 } rlc_bearer_metrics_t;
 
 typedef struct {

lib/include/srslte/upper/rlc_um_base.h

@@ -82,7 +82,7 @@ protected:
     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);
+    int              try_write_sdu(unique_byte_buffer_t sdu);
     void             reset_metrics();
     bool             has_data();
     virtual uint32_t get_buffer_state() = 0;

lib/src/upper/rlc_um_base.cc

@@ -102,7 +102,9 @@ void rlc_um_base::write_sdu(unique_byte_buffer_t sdu, bool blocking)
   if (blocking) {
     tx->write_sdu(std::move(sdu));
   } else {
-    tx->try_write_sdu(std::move(sdu));
+    if (tx->try_write_sdu(std::move(sdu)) != SRSLTE_SUCCESS) {
+      metrics.num_dropped_sdus++;
+    }
   }
 }
 
@@ -251,7 +253,7 @@ void rlc_um_base::rlc_um_base_tx::write_sdu(unique_byte_buffer_t sdu)
   }
 }
 
-void rlc_um_base::rlc_um_base_tx::try_write_sdu(unique_byte_buffer_t sdu)
+int rlc_um_base::rlc_um_base_tx::try_write_sdu(unique_byte_buffer_t sdu)
 {
   if (sdu) {
     uint8_t*                                 msg_ptr   = sdu->msg;
@@ -260,6 +262,7 @@ void rlc_um_base::rlc_um_base_tx::try_write_sdu(unique_byte_buffer_t sdu)
     if (ret) {
       log->info_hex(
           msg_ptr, nof_bytes, "%s Tx SDU (%d B, tx_sdu_queue_len=%d)", rb_name.c_str(), nof_bytes, tx_sdu_queue.size());
+      return SRSLTE_SUCCESS;
     } else {
       log->info_hex(ret.error()->msg,
                     ret.error()->N_bytes,
@@ -271,6 +274,7 @@ void rlc_um_base::rlc_um_base_tx::try_write_sdu(unique_byte_buffer_t sdu)
   } else {
     log->warning("NULL SDU pointer in write_sdu()\n");
   }
+  return SRSLTE_ERROR;
 }
 
 void rlc_um_base::rlc_um_base_tx::discard_sdu(uint32_t discard_sn)

lib/src/upper/rlc_um_lte.cc

@@ -374,6 +374,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
           rx_window[vr_ur].buf->msg += len;
           rx_window[vr_ur].buf->N_bytes -= len;
           rx_sdu->clear();
+          metrics.num_lost_pdus++;
           break;
         }
 
@@ -387,6 +388,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
                        vr_ur,
                        vr_ur_in_rx_sdu);
           rx_sdu->clear();
+          metrics.num_lost_pdus++;
         } else {
           log->info_hex(rx_sdu->msg,
                         rx_sdu->N_bytes,
@@ -423,6 +425,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
           if (pdu_lost && !rlc_um_start_aligned(rx_window[vr_ur].header.fi)) {
             log->warning("Dropping remainder of lost PDU (lower edge last segments)\n");
             rx_sdu->clear();
+            metrics.num_lost_pdus++;
           } else {
             log->info_hex(
                 rx_sdu->msg, rx_sdu->N_bytes, "%s Rx SDU vr_ur=%d (lower edge last segments)", rb_name.c_str(), vr_ur);
@@ -486,6 +489,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
         rx_window[vr_ur].buf->msg += len;
         rx_window[vr_ur].buf->N_bytes -= len;
         rx_sdu->clear();
+        metrics.num_lost_pdus++;
 
         // Reset flag, it is safe to process all remaining segments of this PDU
         pdu_lost = false;
@@ -499,6 +503,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
                    rx_sdu->N_bytes,
                    len);
         rx_sdu->clear();
+        metrics.num_lost_pdus++;
         goto clean_up_rx_window;
       }
 
@@ -551,6 +556,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
         // Advance data pointers and continue with next segment
         rx_window[vr_ur].buf->msg += len;
         rx_window[vr_ur].buf->N_bytes -= len;
+        metrics.num_lost_pdus++;
       }
       pdu_lost = false;
     }
@@ -560,6 +566,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
         !rlc_um_start_aligned(rx_window[vr_ur].header.fi)) {
       log->warning("Dropping PDU %d during last segment handling due to lost start segment\n", vr_ur);
       rx_sdu->clear();
+      metrics.num_lost_pdus++;
       goto clean_up_rx_window;
     }
 
@@ -587,6 +594,7 @@ void rlc_um_lte::rlc_um_lte_rx::reassemble_rx_sdus()
       if (pdu_lost && !rlc_um_start_aligned(rx_window[vr_ur].header.fi)) {
         log->warning("Dropping remainder of lost PDU (update vr_ur last segments)\n");
         rx_sdu->clear();
+        metrics.num_lost_pdus++;
       } else {
         log->info_hex(
             rx_sdu->msg, rx_sdu->N_bytes, "%s Rx SDU vr_ur=%d (update vr_ur last segments)", rb_name.c_str(), vr_ur);

lib/test/upper/rlc_stress_test.cc

@@ -534,6 +534,7 @@ void stress_test(stress_test_args_t args)
          static_cast<double>(tester1.get_nof_rx_pdus() / args.test_duration_sec),
          metrics.bearer[lcid].num_tx_bytes,
          metrics.bearer[lcid].num_rx_bytes);
+  printf("rlc1_num_lost=%d\n", metrics.bearer[lcid].num_lost_pdus);
 
   rlc2.get_metrics(metrics);
   printf("RLC2 received %d SDUs in %ds (%.2f/s), Tx=%" PRIu64 " B, Rx=%" PRIu64 " B\n",
@@ -542,6 +543,7 @@ void stress_test(stress_test_args_t args)
          static_cast<double>(tester2.get_nof_rx_pdus() / args.test_duration_sec),
          metrics.bearer[lcid].num_tx_bytes,
          metrics.bearer[lcid].num_rx_bytes);
+  printf("rlc2_num_lost=%d\n", metrics.bearer[lcid].num_lost_pdus);
 }
 
 int main(int argc, char** argv)