nr: bugfix: LDPC post-processing copies wrong number of bytes

There was a bug. Uplink MAC PDU were corrupted. It turns out
that at the end of the processing of an LDPC segment, the decoded
data is copied to the output buffer, but! with a wrong size, bigger
than it should. The bug I saw was with three segments: 0, 1, and 2.
Segment 1 was finished first, then 0, then 2. When copying segment
0, the beginning of segment 1 was overwritten with the end
of segment 1 (which contains non-data bytes but CRC bytes then 0s),
leading to a corrupted MAC PDU.

Let's copy only the decoded data bytes instead.

openair1/PHY/NR_TRANSPORT/nr_ulsch_decoding.c

@@ -294,6 +294,7 @@ void nr_processULSegment(void* arg) {
   int Kr_bytes;
   int K_bytes_F;
   uint8_t crc_type;
+  int crc_len;
   int i;
   int j;
   int r = rdata->segment_r;
@@ -388,15 +389,19 @@ void nr_processULSegment(void* arg) {
   memset(ulsch_harq->c[r],0,Kr_bytes);
 
   if (ulsch_harq->C == 1) {
-    if (A > 3824)
+    if (A > 3824) {
       crc_type = CRC24_A;
-    else
+      crc_len = 3;
+    } else {
       crc_type = CRC16;
+      crc_len = 2;
+    }
 
     length_dec = ulsch_harq->B;
   }
   else {
     crc_type = CRC24_B;
+    crc_len = 3;
     length_dec = (ulsch_harq->B+24*ulsch_harq->C)/ulsch_harq->C;
   }
 
@@ -434,6 +439,8 @@ void nr_processULSegment(void* arg) {
                                      ulsch_harq->p_nrLDPC_procBuf[r],
                                      p_procTime);
 
+  rdata->data_size = (length_dec>>3) - crc_len;
+
   if (check_crc((uint8_t*)llrProcBuf,length_dec,ulsch_harq->F,crc_type)) {
 #ifdef PRINT_CRC_CHECK
       LOG_I(PHY, "Segment %d CRC OK\n",r);

openair1/PHY/defs_gNB.h

@@ -854,6 +854,7 @@ typedef struct LDPCDecode_s {
   int offset;
   int Tbslbrm;
   int decodeIterations;
+  int data_size;
 } ldpcDecode_t;
 
 struct ldpcReqId {

openair1/SCHED_NR/phy_procedures_nr_gNB.c

@@ -239,7 +239,7 @@ void nr_postDecode(PHY_VARS_gNB *gNB, notifiedFIFO_elt_t *req) {
   if (decodeSuccess) {
     memcpy(ulsch_harq->b+rdata->offset,
            ulsch_harq->c[r],
-           rdata->Kr_bytes- - (ulsch_harq->F>>3) -((ulsch_harq->C>1)?3:0));
+           rdata->data_size);
 
   } else {
     if ( rdata->nbSegments != ulsch_harq->processedSegments ) {

openair1/SIMULATION/NR_PHY/ulschsim.c

@@ -81,7 +81,7 @@ int nr_postDecode_sim(PHY_VARS_gNB *gNB, notifiedFIFO_elt_t *req) {
   if (decodeSuccess) {
     memcpy(ulsch_harq->b+rdata->offset,
            ulsch_harq->c[r],
-           rdata->Kr_bytes- - (ulsch_harq->F>>3) -((ulsch_harq->C>1)?3:0));
+           rdata->data_size);
   } else {
     if ( rdata->nbSegments != ulsch_harq->processedSegments ) {
       int nb=abortTpool(gNB->threadPool, req->key);