From 96ab16f1c7bed71e011b931896bdd5e4165e459a Mon Sep 17 00:00:00 2001
From: Francisco <francisco.paisana@softwareradiosystems.com>
Date: Wed, 12 May 2021 15:38:38 +0100
Subject: [PATCH] s1ap fix - release old rnti (instead of new one) when a new
 rnti with the same tmsi is found. Furthermore, we now make sure to warn log
 if the enb is unable to release the old rnti

---
 srsenb/src/stack/rrc/rrc_ue.cc |  6 ++----
 srsenb/src/stack/upper/s1ap.cc | 19 ++++++++++---------
 2 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/srsenb/src/stack/rrc/rrc_ue.cc b/srsenb/src/stack/rrc/rrc_ue.cc
index c947693c4..aed5cbe57 100644
--- a/srsenb/src/stack/rrc/rrc_ue.cc
+++ b/srsenb/src/stack/rrc/rrc_ue.cc
@@ -391,10 +391,8 @@ void rrc::ue::handle_rrc_con_req(rrc_conn_request_s* msg)
     for (auto& user : parent->users) {
       if (user.first != rnti && user.second->has_tmsi && user.second->mmec == mmec && user.second->m_tmsi == m_tmsi) {
         parent->logger.info("RRC connection request: UE context already exists. M-TMSI=%d", m_tmsi);
-        if (parent->s1ap->user_release(rnti, asn1::s1ap::cause_radio_network_opts::radio_conn_with_ue_lost)) {
-          // Do not wait for MME response
-          parent->rem_user_thread(user.first);
-        }
+        user.second->state = RRC_STATE_IDLE; // Set old rnti to IDLE so that enb doesn't send RRC Connection Release
+        parent->s1ap->user_release(user.first, asn1::s1ap::cause_radio_network_opts::radio_conn_with_ue_lost);
         break;
       }
     }
diff --git a/srsenb/src/stack/upper/s1ap.cc b/srsenb/src/stack/upper/s1ap.cc
index 7755a4aae..1b7314de3 100644
--- a/srsenb/src/stack/upper/s1ap.cc
+++ b/srsenb/src/stack/upper/s1ap.cc
@@ -411,24 +411,21 @@ void s1ap::write_pdu(uint16_t rnti, srsran::unique_byte_buffer_t pdu)
 
 bool s1ap::user_release(uint16_t rnti, asn1::s1ap::cause_radio_network_e cause_radio)
 {
-  logger.info("User inactivity - RNTI:0x%x", rnti);
-
   ue* u = users.find_ue_rnti(rnti);
   if (u == nullptr) {
+    logger.warning("Released UE with rnti=0x%x not found", rnti);
     return false;
   }
 
-  if (u->was_uectxtrelease_requested() or not u->ctxt.mme_ue_s1ap_id.has_value()) {
-    logger.warning("UE context for RNTI:0x%x is in zombie state. Releasing...", rnti);
+  cause_c cause;
+  cause.set_radio_network().value = cause_radio.value;
+
+  if (not u->send_uectxtreleaserequest(cause)) {
     users.erase(u);
     rrc->release_ue(rnti);
     return false;
   }
-
-  cause_c cause;
-  cause.set_radio_network().value = cause_radio.value;
-
-  return u->send_uectxtreleaserequest(cause);
+  return true;
 }
 
 bool s1ap::user_exists(uint16_t rnti)
@@ -1402,6 +1399,10 @@ bool s1ap::ue::send_ulnastransport(srsran::unique_byte_buffer_t pdu)
 
 bool s1ap::ue::send_uectxtreleaserequest(const cause_c& cause)
 {
+  if (was_uectxtrelease_requested()) {
+    logger.warning("UE context for RNTI:0x%x is in zombie state. Releasing...", ctxt.rnti);
+    return false;
+  }
   if (not ctxt.mme_ue_s1ap_id.has_value()) {
     logger.error("Cannot send UE context release request without a MME-UE-S1AP-Id allocated.");
     return false;