Support FQDN Resolver

src/smf_app/smf_app.hpp

@@ -81,10 +81,10 @@ class smf_context_ref {
   void clear() {
     supi           = {};
     nssai          = {};
-    dnn            = "";
+    dnn            = {};
     pdu_session_id = 0;
-    amf_status_uri = "";
-    amf_addr       = "";
+    amf_status_uri = {};
+    amf_addr       = {};
     upf_node_id    = {};
   }
 
@@ -214,6 +214,7 @@ class smf_app {
 
   void operator=(smf_app const&) = delete;
 
+  void test_dns();
   /*
    * Set the association between Seid and SM Context
    * @param [const seid_t &] seid: SessionID

src/smf_app/smf_config.hpp

@@ -137,6 +137,9 @@
   "USE_LOCAL_SUBSCRIPTION_INFO"
 #define SMF_CONFIG_STRING_NAS_FORCE_PUSH_PCO                                   \
   "FORCE_PUSH_PROTOCOL_CONFIGURATION_OPTIONS"
+#define SMF_CONFIG_STRING_SUPPORT_FEATURES_USE_FQDN_DNS "USE_FQDN_DNS"
+
+#define SMF_CONFIG_STRING_FQDN_DNS "FQDN"
 
 #define SMF_MAX_ALLOCATED_PDN_ADDRESSES 1024
 
@@ -217,6 +220,7 @@ class smf_config {
   bool register_nrf;
   bool discover_upf;
   bool use_local_subscription_info;
+  bool use_fqdn_dns;
 
   struct {
     struct in_addr ipv4_addr;
@@ -314,6 +318,7 @@ class smf_config {
     use_local_subscription_info = false;
     register_nrf                = false;
     discover_upf                = false;
+    use_fqdn_dns                = false;
   };
   ~smf_config();
   void lock() { m_rw_lock.lock(); };