mux: fix packing of short MAC PDUs

lib/include/srslte/common/pdu.h

@@ -101,7 +101,7 @@ public:
     if (nof_subheaders > 0) {
       nof_subheaders--;
     }
-    if (cur_idx > 0) {
+    if (cur_idx >= 0) {
       cur_idx--;
     }
   }

lib/src/common/pdu.cc

@@ -126,7 +126,7 @@ uint8_t* sch_pdu::write_packet(srslte::log* log_h)
   for (uint32_t i = 0; i < onetwo_padding; i++) {
     sch_subh padding;
     padding.set_padding();
-    padding.write_subheader(&ptr, false);
+    padding.write_subheader(&ptr, pdu_len > onetwo_padding ? false : true);
   }
 
   // Then write subheaders for MAC CE

srsue/src/stack/mac/mux.cc

@@ -326,13 +326,15 @@ bool mux::allocate_sdu(uint32_t lcid, srslte::sch_pdu* pdu_msg, int max_sdu_sz)
 
         buffer_state = rlc->get_buffer_state(lcid);
       } else {
-        Warning("SDU:   rlc_buffer=%d, requested_sdu_len=%d, allocated=%d/%d, remaining=%d\n",
+        Warning("Couldn't allocate new SDU (rlc_buffer=%d, requested_sdu_len=%d, allocated=%d/%d, remaining=%d)\n",
                 buffer_state,
                 requested_sdu_len,
                 sdu_len,
                 sdu_space,
                 pdu_msg->rem_size());
         pdu_msg->del_subh();
+        // prevent endless loop
+        break;
       }
     } else {
       Debug("Couldn't add new MAC subheader (rlc_buffer=%d, requested_sdu_len=%d, sdu_space=%d, remaining=%d)\n",