From b2a35f6b5a22cccc69d0cb3b1fda2916f3fe7d69 Mon Sep 17 00:00:00 2001
From: Andre Puschmann <andre@softwareradiosystems.com>
Date: Mon, 3 Jun 2019 14:53:07 +0200
Subject: [PATCH] nas: add parser and sender for modify EPS bearer context
 messages

---
 srsue/hdr/stack/upper/nas.h  |  2 ++
 srsue/src/stack/upper/nas.cc | 67 ++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/srsue/hdr/stack/upper/nas.h b/srsue/hdr/stack/upper/nas.h
index cedc6af38..f81d6b09b 100644
--- a/srsue/hdr/stack/upper/nas.h
+++ b/srsue/hdr/stack/upper/nas.h
@@ -170,6 +170,7 @@ 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, const uint8_t sec_hdr_type);
+  void parse_modify_eps_bearer_context_request(srslte::unique_byte_buffer_t pdu);
 
   // Packet generators
   void gen_attach_request(srslte::byte_buffer_t* msg);
@@ -189,6 +190,7 @@ private:
   void send_activate_dedicated_eps_bearer_context_accept(const uint8_t& proc_transaction_id,
                                                          const uint8_t& eps_bearer_id);
   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(const uint8_t sec_hdr_type);
 
   // security context persistence file
diff --git a/srsue/src/stack/upper/nas.cc b/srsue/src/stack/upper/nas.cc
index 12d9254b9..c5ca20ce4 100644
--- a/srsue/src/stack/upper/nas.cc
+++ b/srsue/src/stack/upper/nas.cc
@@ -429,6 +429,9 @@ void nas::write_pdu(uint32_t lcid, unique_byte_buffer_t pdu)
     case LIBLTE_MME_MSG_TYPE_DEACTIVATE_EPS_BEARER_CONTEXT_REQUEST:
       parse_deactivate_eps_bearer_context_request(std::move(pdu));
       break;
+    case LIBLTE_MME_MSG_TYPE_MODIFY_EPS_BEARER_CONTEXT_REQUEST:
+      parse_modify_eps_bearer_context_request(std::move(pdu));
+      break;
     case LIBLTE_MME_MSG_TYPE_ACTIVATE_TEST_MODE:
       parse_activate_test_mode(lcid, std::move(pdu), sec_hdr_type);
       break;
@@ -1175,6 +1178,30 @@ void nas::parse_deactivate_eps_bearer_context_request(unique_byte_buffer_t pdu)
   send_deactivate_eps_bearer_context_accept(request.proc_transaction_id, request.eps_bearer_id);
 }
 
+void nas::parse_modify_eps_bearer_context_request(srslte::unique_byte_buffer_t pdu)
+{
+  LIBLTE_MME_MODIFY_EPS_BEARER_CONTEXT_REQUEST_MSG_STRUCT request;
+
+  liblte_mme_unpack_modify_eps_bearer_context_request_msg((LIBLTE_BYTE_MSG_STRUCT*)pdu.get(), &request);
+
+  nas_log->info("Received Modify EPS bearer context request (eps_bearer_id=%d, proc_id=%d)\n",
+                request.eps_bearer_id,
+                request.proc_transaction_id);
+
+  ctxt.rx_count++;
+
+  // check if bearer exists
+  if (eps_bearer.find(request.eps_bearer_id) == eps_bearer.end()) {
+    nas_log->error("EPS bearer doesn't exist (eps_bearer_id=%d)\n", request.eps_bearer_id);
+    // fixme: send proper response
+    return;
+  }
+
+  // fixme: carry out modification
+  nas_log->info("Modified EPS bearer context (eps_bearer_id=%d)\n", request.eps_bearer_id);
+
+  send_modify_eps_bearer_context_accept(request.proc_transaction_id, request.eps_bearer_id);
+}
 
 void nas::parse_activate_test_mode(uint32_t lcid, unique_byte_buffer_t pdu, const uint8_t sec_hdr_type)
 {
@@ -1886,6 +1913,46 @@ void nas::send_deactivate_eps_bearer_context_accept(const uint8_t& proc_transact
   ctxt.tx_count++;
 }
 
+void nas::send_modify_eps_bearer_context_accept(const uint8_t& proc_transaction_id, const uint8_t& eps_bearer_id)
+{
+  unique_byte_buffer_t pdu = srslte::allocate_unique_buffer(*pool, true);
+
+  LIBLTE_MME_MODIFY_EPS_BEARER_CONTEXT_ACCEPT_MSG_STRUCT accept = {};
+
+  accept.eps_bearer_id       = eps_bearer_id;
+  accept.proc_transaction_id = proc_transaction_id;
+
+  if (liblte_mme_pack_modify_eps_bearer_context_accept_msg(&accept,
+                                                           LIBLTE_MME_SECURITY_HDR_TYPE_INTEGRITY_AND_CIPHERED,
+                                                           ctxt.tx_count,
+                                                           (LIBLTE_BYTE_MSG_STRUCT*)pdu.get())) {
+    nas_log->error("Error packing Modify EPS Bearer context accept.\n");
+    return;
+  }
+
+  if (pcap != NULL) {
+    pcap->write_nas(pdu->msg, pdu->N_bytes);
+  }
+
+  cipher_encrypt(pdu.get());
+  if (pdu->N_bytes > 5) {
+    integrity_generate(
+        &k_nas_int[16], ctxt.tx_count, SECURITY_DIRECTION_UPLINK, &pdu->msg[5], pdu->N_bytes - 5, &pdu->msg[1]);
+  } else {
+    nas_log->error("Invalid PDU size %d\n", pdu->N_bytes);
+    return;
+  }
+
+  nas_log->info_hex(pdu->msg,
+                    pdu->N_bytes,
+                    "Sending Modify EPS Bearer context accept (eps_bearer_id=%d, proc_id=%d)\n",
+                    accept.eps_bearer_id,
+                    accept.proc_transaction_id);
+  rrc->write_sdu(std::move(pdu));
+
+  ctxt.tx_count++;
+}
+
 void nas::send_activate_test_mode_complete(const uint8_t sec_hdr_type)
 {
   unique_byte_buffer_t pdu = srslte::allocate_unique_buffer(*pool, true);