lib,nas: Fix packing and unpacking add_info in generic_nas_transport

lib/include/srsran/asn1/liblte_mme.h

@@ -2430,6 +2430,7 @@ LIBLTE_ERROR_ENUM liblte_mme_pack_security_protected_nas_msg(LIBLTE_BYTE_MSG_STR
 #define LIBLTE_MME_EPS_NETWORK_FEATURE_SUPPORT_IEI 0x64
 #define LIBLTE_MME_ADDITIONAL_UPDATE_RESULT_IEI 0xF
 #define LIBLTE_MME_T3412_EXTENDED_VALUE_IEI 0x5E
+#define LIBLTE_MME_ADDITIONAL_INFORMATION_IEI 0x65
 // Enums
 // Structs
 typedef struct {

lib/src/asn1/liblte_mme.cc

@@ -7600,7 +7600,11 @@ LIBLTE_ERROR_ENUM liblte_mme_pack_downlink_generic_nas_transport_msg(
     liblte_mme_pack_generic_message_container_ie(&dl_generic_nas_transport->generic_msg_cont, &msg_ptr);
 
     // Additional Information
-    liblte_mme_pack_additional_information_ie(&dl_generic_nas_transport->add_info, &msg_ptr);
+    if (dl_generic_nas_transport->add_info_present) {
+      *msg_ptr = LIBLTE_MME_ADDITIONAL_INFORMATION_IEI;
+      msg_ptr++;
+      liblte_mme_pack_additional_information_ie(&dl_generic_nas_transport->add_info, &msg_ptr);
+    }
 
     // Fill in the number of bytes used
     msg->N_bytes = msg_ptr - msg->msg;
@@ -7637,8 +7641,13 @@ LIBLTE_ERROR_ENUM liblte_mme_unpack_downlink_generic_nas_transport_msg(
     liblte_mme_unpack_generic_message_container_ie(&msg_ptr, &dl_generic_nas_transport->generic_msg_cont);
 
     // Additional Information
-    liblte_mme_unpack_additional_information_ie(&msg_ptr, &dl_generic_nas_transport->add_info);
-
+    if (LIBLTE_MME_ADDITIONAL_INFORMATION_IEI == *msg_ptr) {
+      msg_ptr++;
+      liblte_mme_unpack_additional_information_ie(&msg_ptr, &dl_generic_nas_transport->add_info);
+      dl_generic_nas_transport->add_info_present = true;
+    } else {
+      dl_generic_nas_transport->add_info_present = false;
+    }
     err = LIBLTE_SUCCESS;
   }