Refactor TUN Interface Management and Move to SDAP Layer

This commit refactors the TUN interface management by moving its creation
and configuration from the PDCP layer to the SDAP layer for UE.

Key changes include:

- Introduced `tun_generate_ue_ifname` and `tun_destroy` functions for better
  TUN interface lifecycle management.
- Added support for creating and destroying UE-specific TUN interfaces in SDAP.
- Refactored `nr_pdcp_module_init` to remove TUN-related logic and moved it
  to SDAP.
- Updated NAS and SDAP layers to handle PDU session-specific TUN interface
  creation and configuration.
- Enhanced SDAP entity management to include TUN socket handling and thread
  lifecycle.
- Updated NAS message handling to initialize default PDU session TUN
  interfaces in NOS1 mode.
- Use a single SDAP thread function for gNB and UE
- Allow noS1 mode also in SA on gNB

These changes improve modularity by isolating TUN interface management within
the SDAP layer, aligning with the 3GPP architecture, and simplifying the PDCP
layer.

Co-Authored-By: Robert Schmidt <robert.schmidt@openairinterface.org>

executables/nr-softmodem.c

@@ -85,6 +85,7 @@ unsigned short config_frames[4] = {2,9,11,13};
 #include "utils.h"
 #include "x2ap_eNB.h"
 #include "openair1/SCHED_NR/sched_nr.h"
+#include "openair2/SDAP/nr_sdap/nr_sdap.h"
 
 pthread_cond_t nfapi_sync_cond;
 pthread_mutex_t nfapi_sync_mutex;
@@ -497,11 +498,8 @@ static  void wait_nfapi_init(char *thread_name)
 }
 
 void init_pdcp(void) {
-  uint32_t pdcp_initmask = IS_SOFTMODEM_NOS1 ? ENB_NAS_USE_TUN_BIT : LINK_ENB_PDCP_TO_GTPV1U_BIT;
-
   if (!NODE_IS_DU(get_node_type())) {
     nr_pdcp_layer_init();
-    nr_pdcp_module_init(pdcp_initmask, 0);
   }
 }
 

executables/nr-uesoftmodem.c

@@ -301,25 +301,10 @@ void init_openair0()
 
 static void init_pdcp(int ue_id)
 {
-  uint32_t pdcp_initmask = (!IS_SOFTMODEM_NOS1) ? LINK_ENB_PDCP_TO_GTPV1U_BIT : LINK_ENB_PDCP_TO_GTPV1U_BIT;
-
-  /*if (IS_SOFTMODEM_RFSIM || (nfapi_getmode()==NFAPI_UE_STUB_PNF)) {
-    pdcp_initmask = pdcp_initmask | UE_NAS_USE_TUN_BIT;
-  }*/
-
-  // previous code was:
-  //   if (IS_SOFTMODEM_NOKRNMOD)
-  //     pdcp_initmask = pdcp_initmask | UE_NAS_USE_TUN_BIT;
-  // The kernel module (KRNMOD) has been removed from the project, so the 'if'
-  // was removed but the flag 'pdcp_initmask' was kept, as "no kernel module"
-  // was always set. further refactoring could take it out
-  pdcp_initmask = pdcp_initmask | UE_NAS_USE_TUN_BIT;
-
   if (get_softmodem_params()->nsa && nr_rlc_module_init(0) != 0) {
     LOG_I(RLC, "Problem at RLC initiation \n");
   }
   nr_pdcp_layer_init();
-  nr_pdcp_module_init(pdcp_initmask, ue_id);
 }
 
 // Stupid function addition because UE itti messages queues definition is common with eNB
@@ -449,6 +434,11 @@ int main(int argc, char **argv)
     }
   }
 
+  if (create_tasks_nrue(1) < 0) {
+    printf("cannot create ITTI tasks\n");
+    exit(-1); // need a softer mode
+  }
+
   int mode_offset = get_softmodem_params()->nsa ? NUMBER_OF_UE_MAX : 1;
   uint16_t node_number = get_softmodem_params()->node_number;
   ue_id_g = (node_number == 0) ? 0 : node_number - 2;
@@ -557,11 +547,6 @@ int main(int argc, char **argv)
   // wait for end of program
   printf("TYPE <CTRL-C> TO TERMINATE\n");
 
-  if (create_tasks_nrue(1) < 0) {
-    printf("cannot create ITTI tasks\n");
-    exit(-1); // need a softer mode
-  }
-
   // Sleep a while before checking all parameters have been used
   // Some are used directly in external threads, asynchronously
   sleep(2);

executables/softmodem-common.h

@@ -144,6 +144,7 @@ extern "C"
 #define EMULATE_L1          softmodem_params.emulate_l1
 #define CONTINUOUS_TX       softmodem_params.continuous_tx
 #define SYNC_REF            softmodem_params.sync_ref
+#define DEFAULT_PDU_ID      softmodem_params.default_pdu_session_id
 
 #define DEFAULT_RFCONFIG_FILE    "/usr/local/etc/syriq/ue.band7.tm1.PRB100.NR40.dat";
 
@@ -188,6 +189,7 @@ extern int usrp_tx_thread;
   {"E" ,                    CONFIG_HLP_TQFS,          PARAMFLAG_BOOL, .iptr=&softmodem_params.threequarter_fs, .defintval=0,            TYPE_INT,    0}, \
   {"imscope" ,              CONFIG_HLP_IMSCOPE,       PARAMFLAG_BOOL, .uptr=&enable_imscope,                   .defintval=0,            TYPE_UINT,   0}, \
   {"imscope-record" ,       CONFIG_HLP_IMSCOPE_RECORD,PARAMFLAG_BOOL, .uptr=&enable_imscope_record,            .defintval=0,            TYPE_UINT,   0}, \
+  {"default_pdu_id",        NULL,                     0,              .iptr=&DEFAULT_PDU_ID,                   .defintval=10,           TYPE_INT,    0}, \
 }
 // clang-format on
 
@@ -234,6 +236,7 @@ extern int usrp_tx_thread;
     { .s5 = { NULL } },                     \
     { .s5 = { NULL } },                     \
     { .s5 = { NULL } },                     \
+    { .s5 = { NULL } },                     \
 }
 // clang-format on
 
@@ -343,6 +346,7 @@ typedef struct {
   uint32_t       sync_ref;
   int no_itti;
   int threequarter_fs;
+  int default_pdu_session_id;
 } softmodem_params_t;
 
 #define IS_SA_MODE(sM_params) (!(sM_params)->phy_test && !(sM_params)->do_ra && !(sM_params)->nsa)