refactor airplane mode simulation and move to NAS

- move handling to NAS
- use switch off to enable airplane mode (don't wait for EPC response)
- add tiny FSM to control airplane mode activation/deactivation
- only start on/off counter after state has been entered

srsue/hdr/stack/ue_stack_base.h

@@ -57,11 +57,6 @@ typedef struct {
   int usim_hex_limit;
 } stack_log_args_t;
 
-typedef struct {
-  int airplane_t_on_ms;
-  int airplane_t_off_ms;
-} ue_sim_args_t;
-
 typedef struct {
   std::string      type;
   pcap_args_t      pcap;
@@ -72,7 +67,6 @@ typedef struct {
   nas_args_t       nas;
   gw_args_t        gw;
   bool             have_tti_time_stats;
-  ue_sim_args_t    sim;
 } stack_args_t;
 
 class ue_stack_base

srsue/hdr/stack/ue_stack_lte.h

@@ -141,6 +141,7 @@ private:
 
   bool                  running;
   srsue::stack_args_t   args;
+
   srslte::tti_point     current_tti;
 
   // timers

srsue/hdr/stack/upper/nas.h

@@ -152,6 +152,10 @@ private:
   uint8_t k_nas_enc[32] = {};
   uint8_t k_nas_int[32] = {};
 
+  // Airplane mode simulation
+  typedef enum { DISABLED = 0, ENABLED } airplane_mode_state_t;
+  airplane_mode_state_t airplane_mode_state = {};
+
   // PCAP
   srslte::nas_pcap* pcap = nullptr;
 
@@ -209,6 +213,7 @@ private:
   void send_activate_test_mode_complete(const uint8_t sec_hdr_type);
 
   // Other internal helpers
+  void handle_airplane_mode_sim();
   void enter_emm_deregistered();
 
   // security context persistence file

srsue/hdr/stack/upper/nas_common.h

@@ -24,6 +24,11 @@
 
 namespace srsue {
 
+typedef struct {
+  int airplane_t_on_ms;
+  int airplane_t_off_ms;
+} nas_sim_args_t;
+
 class nas_args_t
 {
 public:
@@ -36,6 +41,7 @@ public:
   bool           force_imsi_attach;
   std::string    eia;
   std::string    eea;
+  nas_sim_args_t sim;
 };
 
 // EMM states (3GPP 24.302 v10.0.0)

srsue/src/main.cc

@@ -370,11 +370,11 @@ static int parse_args(all_args_t* args, int argc, char* argv[])
 
     // UE simulation args
     ("sim.airplane_t_on_ms",
-     bpo::value<int>(&args->stack.sim.airplane_t_on_ms)->default_value(-1),
+     bpo::value<int>(&args->stack.nas.sim.airplane_t_on_ms)->default_value(-1),
      "On-time for airplane mode (in ms)")
 
     ("sim.airplane_t_off_ms",
-     bpo::value<int>(&args->stack.sim.airplane_t_off_ms)->default_value(-1),
+     bpo::value<int>(&args->stack.nas.sim.airplane_t_off_ms)->default_value(-1),
      "Off-time for airplane mode (in ms)")
 
      /* general options */

srsue/src/stack/ue_stack_lte.cc

@@ -176,14 +176,6 @@ bool ue_stack_lte::switch_on()
   if (running) {
     pending_tasks.try_push(ue_queue_id,
                            [this]() { nas.start_attach_request(nullptr, srslte::establishment_cause_t::mo_sig); });
-
-    // schedule airplane mode on command
-    if (args.sim.airplane_t_on_ms > 0) {
-      timers.defer_callback(args.sim.airplane_t_on_ms, [&]() {
-        // Enable air-plane mode
-        disable_data();
-      });
-    }
     return true;
   }
   return false;
@@ -221,16 +213,7 @@ bool ue_stack_lte::disable_data()
 {
   // generate detach request
   stack_log->console("Turning on airplane mode.\n");
-  int ret = nas.detach_request(false);
-
-  // schedule airplane mode off command
-  if (args.sim.airplane_t_off_ms > 0) {
-    timers.defer_callback(args.sim.airplane_t_off_ms, [&]() {
-      // Disable airplane mode again
-      enable_data();
-    });
-  }
-  return ret;
+  return nas.detach_request(false);
 }
 
 bool ue_stack_lte::get_metrics(stack_metrics_t* metrics)

srsue/src/stack/upper/nas.cc

@@ -302,6 +302,8 @@ void nas::init(usim_interface_nas* usim_, rrc_interface_nas* rrc_, gw_interface_
   t3421.set(t3421_duration_ms, [this](uint32_t tid) { timer_expired(tid); });
   reattach_timer.set(reattach_timer_duration_ms, [this](uint32_t tid) { timer_expired(tid); });
 
+  handle_airplane_mode_sim();
+
   running = true;
 }
 
@@ -2323,6 +2325,40 @@ void nas::send_activate_test_mode_complete(const uint8_t sec_hdr_type)
   ctxt.tx_count++;
 }
 
+/*
+ * Handles the airplane mode simulation by triggering a UE switch off/on
+ * in user-definable time intervals
+ */
+void nas::handle_airplane_mode_sim()
+{
+  if (cfg.sim.airplane_t_on_ms > 0 && airplane_mode_state == DISABLED) {
+    // check if we're already attached, if so, schedule airplane mode command
+    if (state == EMM_STATE_REGISTERED) {
+      // NAS is attached
+      task_handler->defer_callback(cfg.sim.airplane_t_on_ms, [&]() {
+        // Enabling air-plane mode
+        send_detach_request(true);
+        airplane_mode_state = ENABLED;
+      });
+    }
+  } else if (cfg.sim.airplane_t_off_ms > 0 && airplane_mode_state == ENABLED) {
+    // check if we are already deregistered, if so, schedule command to turn off airplone mode again
+    if (state == EMM_STATE_DEREGISTERED) {
+      // NAS is deregistered
+      task_handler->defer_callback(cfg.sim.airplane_t_off_ms, [&]() {
+        // Disabling airplane mode again
+        start_attach_request(nullptr, srslte::establishment_cause_t::mo_sig);
+        airplane_mode_state = DISABLED;
+      });
+    }
+  }
+
+  // schedule another call
+  if (cfg.sim.airplane_t_on_ms > 0 || cfg.sim.airplane_t_off_ms > 0) {
+    task_handler->defer_callback(1000, [&]() { handle_airplane_mode_sim(); });
+  }
+}
+
 /*******************************************************************************
  * Security context persistence file
  ******************************************************************************/