lib,rlc_am_nr: use std:vector for nacks in rlc_am_nr_status_pdu_t

- Also create tx_status a member to avoid frequent allocations
for each created PDU.

- Remove unused member nack_range from rlc_am_nr_status_pdu_t.

lib/include/srsran/rlc/rlc_am_nr.h

@@ -149,10 +149,11 @@ private:
   struct rlc_am_nr_tx_state_t                             st = {};
   std::unique_ptr<rlc_ringbuffer_base<rlc_amd_tx_pdu_nr> > tx_window;
 
-  // Queues and buffers
+  // Queues, buffers and container
   std::unique_ptr<pdu_retx_queue_base<rlc_amd_retx_nr_t> > retx_queue;
   uint32_t sdu_under_segmentation_sn = INVALID_RLC_SN; // SN of the SDU currently being segmented.
   pdcp_sn_vector_t notify_info_vec;
+  rlc_am_nr_status_pdu_t tx_status;
 
   // Helper constants
   uint32_t min_hdr_size = 2;

lib/include/srsran/rlc/rlc_am_nr_packing.h

@@ -78,13 +78,23 @@ struct rlc_amd_tx_sdu_nr_t {
 };
 
 ///< AM NR Status PDU header (perhaps merge with LTE version)
-typedef struct {
-  rlc_am_nr_control_pdu_type_t cpt;
-  uint32_t                     ack_sn; ///< SN of the next not received RLC Data PDU
-  uint16_t                     N_nack; ///< number of NACKs
-  uint8_t           nack_range;        ///< number of consecutively lost RLC SDUs starting from and including NACK_SN
-  rlc_status_nack_t            nacks[RLC_AM_NR_MAX_NACKS];
-} rlc_am_nr_status_pdu_t;
+struct rlc_am_nr_status_pdu_t {
+  rlc_am_nr_control_pdu_type_t   cpt;
+  uint32_t                       ack_sn; ///< SN of the next not received RLC Data PDU
+  uint16_t                       N_nack; ///< number of NACKs
+  std::vector<rlc_status_nack_t> nacks;
+
+  rlc_am_nr_status_pdu_t() :
+    cpt(rlc_am_nr_control_pdu_type_t::status_pdu), ack_sn(INVALID_RLC_SN), N_nack(0), nacks(RLC_AM_NR_TYP_NACKS)
+  {}
+  void reset()
+  {
+    cpt    = rlc_am_nr_control_pdu_type_t::status_pdu;
+    ack_sn = INVALID_RLC_SN;
+    N_nack = 0;
+    nacks.clear();
+  }
+};
 
 /****************************************************************************
  * Header pack/unpack helper functions for NR

lib/include/srsran/rlc/rlc_common.h

@@ -34,7 +34,8 @@ namespace srsran {
 #define RLC_MAX_SDU_SIZE ((1 << 11) - 1) // Length of LI field is 11bits
 #define RLC_AM_MIN_DATA_PDU_SIZE (3)     // AMD PDU with 10 bit SN (length of LI field is 11 bits) (No LI)
 
-#define RLC_AM_NR_MAX_NACKS 2048
+#define RLC_AM_NR_TYP_NACKS 512  // Expected number of NACKs in status PDU before expanding space by alloc
+#define RLC_AM_NR_MAX_NACKS 2048 // Maximum number of NACKs in status PDU
 
 #define RlcDebug(fmt, ...) logger.debug("%s: " fmt, rb_name, ##__VA_ARGS__)
 #define RlcInfo(fmt, ...) logger.info("%s: " fmt, rb_name, ##__VA_ARGS__)

lib/src/rlc/rlc_am_nr.cc

@@ -676,8 +676,8 @@ uint32_t rlc_am_nr_tx::get_retx_expected_hdr_len(const rlc_amd_retx_nr_t& retx)
 uint32_t rlc_am_nr_tx::build_status_pdu(byte_buffer_t* payload, uint32_t nof_bytes)
 {
   RlcInfo("generating status PDU. Bytes available:%d", nof_bytes);
-  rlc_am_nr_status_pdu_t tx_status;
-  int                    pdu_len = rx->get_status_pdu(&tx_status, nof_bytes);
+  tx_status.reset();
+  int pdu_len = rx->get_status_pdu(&tx_status, nof_bytes);
   if (pdu_len == SRSRAN_ERROR) {
     RlcDebug("deferred status PDU. Cause: Failed to acquire rx lock");
     pdu_len = 0;
@@ -1286,6 +1286,8 @@ uint32_t rlc_am_nr_rx::get_status_pdu(rlc_am_nr_status_pdu_t* status, uint32_t m
       }
     }
 
+    // TODO: add check to not exceed status->N_nack >= RLC_AM_NR_MAX_NACKS
+
     // make sure we don't exceed grant size (FIXME)
     rlc_am_nr_write_status_pdu(*status, cfg.rx_sn_field_length, &tmp_buf);
     // TODO