Implement Close UE Test Loop/Complete messages

This commit implements support for the CLOSE_UE_TEST_LOOP message.
Currently the mode is not saved and looping the data is not implemented.
Only the *_COMPLETE message is sent back as a response.

lib/include/srslte/asn1/liblte_mme.h

@@ -4007,4 +4007,19 @@ liblte_mme_unpack_pdn_disconnect_request_msg(LIBLTE_BYTE_MSG_STRUCT*
 LIBLTE_ERROR_ENUM
 liblte_mme_pack_activate_test_mode_complete_msg(LIBLTE_BYTE_MSG_STRUCT* msg, uint8 sec_hdr_type, uint32 count);
 
+/*********************************************************************
+    Message Name: CLOSE UE TEST LOOP COMPLETE
+
+    Description: Sent by the UE to the network in response to a
+                 CLOSE UE TEST LOOP message.
+
+    Document Reference: 36.509 v8.7.0 Section 6.2
+*********************************************************************/
+// Defines
+// Enums
+// Structs
+// Functions
+LIBLTE_ERROR_ENUM
+liblte_mme_pack_close_ue_test_loop_complete_msg(LIBLTE_BYTE_MSG_STRUCT* msg, uint8 sec_hdr_type, uint32 count);
+
 #endif // SRSLTE_LIBLTE_MME_H

lib/src/asn1/liblte_mme.cc

@@ -10328,6 +10328,44 @@ liblte_mme_pack_activate_test_mode_complete_msg(LIBLTE_BYTE_MSG_STRUCT* msg, uin
   return (err);
 }
 
+LIBLTE_ERROR_ENUM
+liblte_mme_pack_close_ue_test_loop_complete_msg(LIBLTE_BYTE_MSG_STRUCT* msg, uint8 sec_hdr_type, uint32 count)
+{
+  LIBLTE_ERROR_ENUM err     = LIBLTE_ERROR_INVALID_INPUTS;
+  uint8*            msg_ptr = msg->msg;
+
+  if (msg != NULL) {
+    if (LIBLTE_MME_SECURITY_HDR_TYPE_PLAIN_NAS != sec_hdr_type) {
+      // Protocol Discriminator and Security Header Type
+      *msg_ptr = (sec_hdr_type << 4) | (LIBLTE_MME_PD_EPS_MOBILITY_MANAGEMENT);
+      msg_ptr++;
+
+      // MAC will be filled in later
+      msg_ptr += 4;
+
+      // Sequence Number
+      *msg_ptr = count & 0xFF;
+      msg_ptr++;
+    }
+
+    // Protocol Discriminator and skip indicator (always 0x0F)
+    *msg_ptr =
+        (LIBLTE_MME_MSG_TYPE_TEST_MODE_SKIP_INDICATOR << 4) | (LIBLTE_MME_MSG_TYPE_TEST_MODE_PROTOCOL_DISCRIMINATOR);
+    msg_ptr++;
+
+    // Message Type
+    *msg_ptr = LIBLTE_MME_MSG_TYPE_CLOSE_UE_TEST_LOOP_COMPLETE;
+    msg_ptr++;
+
+    // Fill in the number of bytes used
+    msg->N_bytes = msg_ptr - msg->msg;
+
+    err = LIBLTE_SUCCESS;
+  }
+
+  return (err);
+}
+
 /*******************************************************************************
                               HELPER FUNCTIONS
 *******************************************************************************/

srsue/hdr/stack/upper/nas.h

@@ -196,6 +196,7 @@ private:
   void parse_activate_dedicated_eps_bearer_context_request(uint32_t lcid, srslte::unique_byte_buffer_t pdu);
   void parse_deactivate_eps_bearer_context_request(srslte::unique_byte_buffer_t pdu);
   void parse_activate_test_mode(uint32_t lcid, srslte::unique_byte_buffer_t pdu);
+  void parse_close_ue_test_loop(uint32_t lcid, srslte::unique_byte_buffer_t pdu);
   void parse_modify_eps_bearer_context_request(srslte::unique_byte_buffer_t pdu);
 
   // Packet generators
@@ -219,6 +220,7 @@ private:
   void send_deactivate_eps_bearer_context_accept(const uint8_t& proc_transaction_id, const uint8_t& eps_bearer_id);
   void send_modify_eps_bearer_context_accept(const uint8_t& proc_transaction_id, const uint8_t& eps_bearer_id);
   void send_activate_test_mode_complete();
+  void send_close_ue_test_loop_complete();
 
   // Other internal helpers
   void enter_state(emm_state_t state_);

srsue/src/stack/upper/nas.cc

@@ -694,10 +694,12 @@ void nas::write_pdu(uint32_t lcid, unique_byte_buffer_t pdu)
     case LIBLTE_MME_MSG_TYPE_ACTIVATE_TEST_MODE:
       parse_activate_test_mode(lcid, std::move(pdu));
       break;
-    // TODO: Handle deactivate test mode and ue close/open
-    case LIBLTE_MME_MSG_TYPE_DEACTIVATE_TEST_MODE:
     case LIBLTE_MME_MSG_TYPE_CLOSE_UE_TEST_LOOP:
+      parse_close_ue_test_loop(lcid, std::move(pdu));
+      break;
+    // TODO: Handle deactivate test mode and ue open test loop
     case LIBLTE_MME_MSG_TYPE_OPEN_UE_TEST_LOOP:
+    case LIBLTE_MME_MSG_TYPE_DEACTIVATE_TEST_MODE:
     default:
       nas_log->error("Not handling NAS message with MSG_TYPE=%02X\n", msg_type);
       return;
@@ -1674,6 +1676,17 @@ void nas::parse_activate_test_mode(uint32_t lcid, unique_byte_buffer_t pdu)
   send_activate_test_mode_complete();
 }
 
+void nas::parse_close_ue_test_loop(uint32_t lcid, unique_byte_buffer_t pdu)
+{
+  nas_log->info("Received Close UE test loop\n");
+
+  ctxt.rx_count++;
+
+  // TODO: Save the test loop mode
+
+  send_close_ue_test_loop_complete();
+}
+
 void nas::parse_emm_status(uint32_t lcid, unique_byte_buffer_t pdu)
 {
   LIBLTE_MME_EMM_STATUS_MSG_STRUCT emm_status;
@@ -2425,6 +2438,31 @@ void nas::send_activate_test_mode_complete()
   ctxt.tx_count++;
 }
 
+void nas::send_close_ue_test_loop_complete()
+{
+  unique_byte_buffer_t pdu = srslte::allocate_unique_buffer(*pool, true);
+
+  if (liblte_mme_pack_close_ue_test_loop_complete_msg(
+          (LIBLTE_BYTE_MSG_STRUCT*)pdu.get(), current_sec_hdr, ctxt.tx_count)) {
+    nas_log->error("Error packing close UE test loop complete.\n");
+    return;
+  }
+
+  if (pcap != nullptr) {
+    pcap->write_nas(pdu->msg, pdu->N_bytes);
+  }
+
+  if (apply_security_config(pdu, current_sec_hdr)) {
+    nas_log->error("Error applying NAS security.\n");
+    return;
+  }
+
+  nas_log->info_hex(pdu->msg, pdu->N_bytes, "Sending Close UE test loop complete\n");
+  rrc->write_sdu(std::move(pdu));
+
+  ctxt.tx_count++;
+}
+
 /*
  * Handles the airplane mode simulation by triggering a UE switch off/on
  * in user-definable time intervals