check expiration of poll_retx_timer and schedule retx if needed

lib/src/upper/rlc_am.cc

@@ -198,7 +198,7 @@ uint32_t rlc_am::get_bearer()
 void rlc_am::write_sdu(byte_buffer_t *sdu)
 {
   tx_sdu_queue.write(sdu);
-  log->info_hex(sdu->msg, sdu->N_bytes, "%s Tx SDU, tx_sdu_len=%d", rrc->get_rb_name(lcid).c_str(), tx_sdu_queue.size());
+  log->info_hex(sdu->msg, sdu->N_bytes, "%s Tx SDU, tx_sdu_queue_len=%d", rrc->get_rb_name(lcid).c_str(), tx_sdu_queue.size());
 }
 
 /****************************************************************************
@@ -273,6 +273,27 @@ uint32_t rlc_am::get_buffer_state()
     goto unlock_and_return;
   }
 
+  // check if pollRetx timer expired (Section 5.2.2.3 in TS 36.322)
+  if (poll_retx()) {
+    // if both tx and retx buffer are empty, retransmit next PDU to be ack'ed
+    log->info("Poll reTx timer expired (lcid=%d)\n", lcid);
+    if ((tx_window.size() > 0 && retx_queue.size() == 0 && tx_sdu_queue.size() == 0)) {
+      std::map<uint32_t, rlc_amd_tx_pdu_t>::iterator it = tx_window.find(vt_s - 1);
+      if (it != tx_window.end()) {
+        log->info("Schedule last PDU (SN=%d) for reTx.\n", vt_s - 1);
+        rlc_amd_retx_t retx;
+        retx.is_segment = false;
+        retx.so_start = 0;
+        retx.so_end = tx_window[vt_s - 1].buf->N_bytes;
+        retx.sn = vt_s - 1;
+        retx_queue.push_back(retx);
+      } else {
+        log->error("Found invalid PDU in tx_window.\n");
+      }
+      poll_retx_timeout.start(cfg.t_poll_retx);
+    }
+  }
+
   // Bytes needed for retx
   if(retx_queue.size() > 0) {
     rlc_amd_retx_t retx = retx_queue.front();