s1ap: run connect in background thread to avoid blocking

srsenb/hdr/stack/s1ap/s1ap.h

@@ -330,10 +330,14 @@ private:
       bool success = false;
       enum class cause_t { timeout, failure } cause;
     };
+    struct s1connectresult {
+      bool success = false;
+    };
 
     explicit s1_setup_proc_t(s1ap* s1ap_) : s1ap_ptr(s1ap_) {}
     srsran::proc_outcome_t init();
     srsran::proc_outcome_t step() { return srsran::proc_outcome_t::yield; }
+    srsran::proc_outcome_t react(const s1connectresult& event);
     srsran::proc_outcome_t react(const s1setupresult& event);
     void                   then(const srsran::proc_state_t& result);
     const char*            name() const { return "MME Connection"; }

srsenb/src/stack/s1ap/s1ap.cc

@@ -237,21 +237,38 @@ srsran::proc_outcome_t s1ap::s1_setup_proc_t::start_mme_connection()
     return srsran::proc_outcome_t::success;
   }
 
-  if (not s1ap_ptr->connect_mme()) {
-    procInfo("Could not connect to MME");
-    return srsran::proc_outcome_t::error;
-  }
+  auto connect_callback = [this]() {
+    bool connected = s1ap_ptr->connect_mme();
+
+    auto notify_result = [this, connected]() {
+      s1_setup_proc_t::s1connectresult res;
+      res.success = connected;
+      s1ap_ptr->s1setup_proc.trigger(res);
+    };
+    s1ap_ptr->task_sched.notify_background_task_result(notify_result);
+  };
+  srsran::get_background_workers().push_task(connect_callback);
+
+  return srsran::proc_outcome_t::yield;
+}
 
+srsran::proc_outcome_t s1ap::s1_setup_proc_t::react(const srsenb::s1ap::s1_setup_proc_t::s1connectresult& event)
+{
+  if (event.success) {
+    procInfo("Connected to MME. Sending S1 setup request.");
+    s1ap_ptr->s1setup_timeout.run();
     if (not s1ap_ptr->setup_s1()) {
       procError("S1 setup failed. Exiting...");
       srsran::console("S1 setup failed\n");
       s1ap_ptr->running = false;
       return srsran::proc_outcome_t::error;
     }
-
-  s1ap_ptr->s1setup_timeout.run();
-  procInfo("S1SetupRequest sent. Waiting for response...");
+    procInfo("S1 setup request sent. Waiting for response.");
     return srsran::proc_outcome_t::yield;
+  }
+
+  procInfo("Could not connected to MME. Aborting");
+  return srsran::proc_outcome_t::error;
 }
 
 srsran::proc_outcome_t s1ap::s1_setup_proc_t::react(const srsenb::s1ap::s1_setup_proc_t::s1setupresult& event)