Added a comment to justify pdu_len checks in gNB

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_ulsch.c

@@ -261,6 +261,10 @@ int nr_process_mac_pdu(module_id_t module_idP,
         case UL_SCH_LCID_L_TRUNCATED_BSR:
         	//38.321 section 6.1.3.1
         	//variable length
+                /* Several checks have been added to this function to
+                   ensure that the casting of the pduP is possible. There
+                   is an actual bug here, but it has not been resolved. This
+                   means that the scheduled transport block size is invalid. */
                 if (pdu_len < sizeof(NR_MAC_SUBHEADER_SHORT))
                         return 0;
         	mac_ce_len |= (uint16_t)((NR_MAC_SUBHEADER_SHORT *)pduP)->L;