From 163c078c427dcddb683e19ec3a68b61c99ce6189 Mon Sep 17 00:00:00 2001
From: Pedro Alvarez <pedro.alvarez@softwareradiosystems.com>
Date: Wed, 24 Jun 2020 12:37:14 +0100
Subject: [PATCH] srsEPC: Using bearer state to decide weather to send release
 bearer request or not.

---
 srsepc/src/mme/nas.cc                 | 11 +++++++++++
 srsepc/src/mme/s1ap_ctx_mngmt_proc.cc | 13 +++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/srsepc/src/mme/nas.cc b/srsepc/src/mme/nas.cc
index d4ebc0255..a9bff4d90 100644
--- a/srsepc/src/mme/nas.cc
+++ b/srsepc/src/mme/nas.cc
@@ -759,6 +759,11 @@ bool nas::handle_detach_request(uint32_t                m_tmsi,
   emm_ctx->state = EMM_STATE_DEREGISTERED;
   sec_ctx->ul_nas_count++;
 
+  // Mark E-RABs as de-activated
+  for (esm_ctx_t& esm_ctx : nas_ctx->m_esm_ctx) {
+    esm_ctx.state = ERAB_DEACTIVATED;
+  }
+
   nas_log->console("Received. M-TMSI 0x%x\n", m_tmsi);
   // Received detach request as an initial UE message
   // eNB created new ECM context to send the detach request; this needs to be cleared.
@@ -1242,6 +1247,12 @@ bool nas::handle_detach_request(srslte::byte_buffer_t* nas_msg)
 
   m_gtpc->send_delete_session_request(m_emm_ctx.imsi);
   m_emm_ctx.state = EMM_STATE_DEREGISTERED;
+
+  // Mark E-RABs as de-activated
+  for (esm_ctx_t& esm_ctx : m_esm_ctx) {
+    esm_ctx.state = ERAB_DEACTIVATED;
+  }
+
   if (m_ecm_ctx.mme_ue_s1ap_id != 0) {
     m_s1ap->send_ue_context_release_command(m_ecm_ctx.mme_ue_s1ap_id);
   }
diff --git a/srsepc/src/mme/s1ap_ctx_mngmt_proc.cc b/srsepc/src/mme/s1ap_ctx_mngmt_proc.cc
index 70c3ee670..e58f0c926 100644
--- a/srsepc/src/mme/s1ap_ctx_mngmt_proc.cc
+++ b/srsepc/src/mme/s1ap_ctx_mngmt_proc.cc
@@ -287,9 +287,18 @@ bool s1ap_ctx_mngmt_proc::send_ue_context_release_command(nas* nas_ctx, bool sen
     return false;
   }
 
+  // Detect weather there are active E-RABs
+  bool active_erabs = false;
+  for (esm_ctx_t& esm_ctx : nas_ctx->m_esm_ctx) {
+    if (esm_ctx.state != ERAB_DEACTIVATED) {
+      active_erabs = true;
+      break;
+    }
+  }
+
   // On some circumstances, such as the NAS Detach, the UE context has already been cleared from
   // the SPGW. In such cases, there is no need to send the GTP-C Release Access Bearers Request.
-  if (send_release_erabs) {
+  if (active_erabs) {
     // There are active E-RABs, send release access mearers request
     m_s1ap_log->console("There are active E-RABs, send release access bearers request\n");
     m_s1ap_log->info("There are active E-RABs, send release access bearers request\n");
@@ -299,7 +308,7 @@ bool s1ap_ctx_mngmt_proc::send_ue_context_release_command(nas* nas_ctx, bool sen
     m_mme_gtpc->send_release_access_bearers_request(emm_ctx->imsi);
   }
 
-  // Mark ECM state as IDLE
+  // Mark ECM state as IDLE and de-activate E-RABs
   ecm_ctx->state = ECM_STATE_IDLE;
   for (esm_ctx_t& esm_ctx : nas_ctx->m_esm_ctx) {
     esm_ctx.state = ERAB_DEACTIVATED;