mac_nr_test: add testcase for MAC PDU packing with long L field

this reproduces the issue found in #2609

srsue/src/stack/mac_nr/test/mac_nr_test.cc

@@ -228,6 +228,99 @@ int mac_nr_ul_logical_channel_prioritization_test1()
   return SRSRAN_SUCCESS;
 }
 
+// Correct packing of MAC PDU with subHeader with 16bit L field
+int mac_nr_ul_logical_channel_prioritization_test2()
+{
+  // PDU layout (260 B in total)
+  // -   3 B MAC subheader for SCH LCID=4 for 16bit L field
+  // - 257 B sduPDU
+  const uint8_t tv[] = {
+      0x44, 0x01, 0x01, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+      0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+  };
+
+  // dummy layers
+  dummy_phy   phy;
+  rlc_dummy   rlc;
+  rrc_dummy   rrc;
+  stack_dummy stack;
+
+  // the actual MAC
+  mac_nr mac(&stack.task_sched);
+
+  mac_nr_args_t args = {};
+  mac.init(args, &phy, &rlc, &rrc);
+
+  stack.init(&mac, &phy);
+  const uint16_t crnti = 0x1001;
+
+  // generate config (default DRB2 config for EN-DC)
+  std::vector<srsran::logical_channel_config_t> lcids;
+  srsran::logical_channel_config_t              config = {};
+  config.lcid                                          = 4;
+  config.lcg                                           = 6;
+  config.PBR                                           = 0;
+  config.BSD                                           = 1000; // 1000ms
+  config.priority                                      = 11;
+  lcids.push_back(config);
+
+  // setup LCIDs in MAC
+  for (auto& channel : lcids) {
+    mac.setup_lcid(channel);
+  }
+
+  // write dummy data to DRB2
+  rlc.write_sdu(4, 1000);
+
+  // run TTI to setup Bj, BSR should be generated
+  stack.run_tti(0);
+  usleep(100);
+
+  // create UL action and grant and read MAC PDU
+  {
+    mac_interface_phy_nr::tb_action_ul_t    ul_action = {};
+    mac_interface_phy_nr::mac_nr_grant_ul_t mac_grant = {};
+
+    mac_grant.rnti = crnti; // make sure MAC picks it up as valid UL grant
+    mac_grant.pid  = 0;
+    mac_grant.rnti = 0x1001;
+    mac_grant.tti  = 0;
+    mac_grant.tbs  = 260;
+    int cc_idx     = 0;
+
+    // Send grant to MAC and get action for this TB, 0x
+    mac.new_grant_ul(cc_idx, mac_grant, &ul_action);
+
+    // print generated PDU
+    srslog::fetch_basic_logger("MAC").info(
+        ul_action.tb.payload->msg, mac_grant.tbs, "Generated PDU (%d B)", mac_grant.tbs);
+#if HAVE_PCAP
+    pcap_handle->write_ul_crnti_nr(
+        ul_action.tb.payload->msg, mac_grant.tbs, mac_grant.rnti, UE_ID, mac_grant.pid, mac_grant.tti);
+#endif
+
+    TESTASSERT(memcmp(ul_action.tb.payload->msg, tv, sizeof(tv)) == 0);
+  }
+
+  // make sure MAC PDU thread picks up before stopping
+  stack.run_tti(0);
+  mac.stop();
+
+  return SRSRAN_SUCCESS;
+}
+
 // Basic test for periodic BSR transmission
 int mac_nr_ul_periodic_bsr_test()
 {
@@ -395,6 +488,7 @@ int main()
 
   TESTASSERT(msg3_test() == SRSRAN_SUCCESS);
   TESTASSERT(mac_nr_ul_logical_channel_prioritization_test1() == SRSRAN_SUCCESS);
+  TESTASSERT(mac_nr_ul_logical_channel_prioritization_test2() == SRSRAN_SUCCESS);
   TESTASSERT(mac_nr_ul_periodic_bsr_test() == SRSRAN_SUCCESS);
 
   return SRSRAN_SUCCESS;