From 8c22d8a20ca8506716e5fbde0f1b0050a6d997da Mon Sep 17 00:00:00 2001
From: Supreeth Herle <herlesupreeth@gmail.com>
Date: Wed, 13 Apr 2022 00:06:49 +0200
Subject: [PATCH] Send EMM Cause when Attach Request type is not same as HSS
 Network-Access-Mode (#1484)

This commit adds EMM Cause to Attach accept message when
Attach Request has COMBINED EPS IMSI ATTACH but the HSS
Network-Access-Mode is configure for EPS ONLY.
---
 src/mme/emm-build.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/mme/emm-build.c b/src/mme/emm-build.c
index d54e112fe..c670015cd 100644
--- a/src/mme/emm-build.c
+++ b/src/mme/emm-build.c
@@ -113,6 +113,14 @@ ogs_pkbuf_t *emm_build_attach_accept(
                             "EPS_EMERGENCY_ATTACH]");
                 break;
         }
+
+        if ((mme_ue->nas_eps.attach.value ==
+                OGS_NAS_ATTACH_TYPE_COMBINED_EPS_IMSI_ATTACH) &&
+            (eps_attach_result->result == OGS_NAS_ATTACH_TYPE_EPS_ATTACH)) {
+            attach_accept->presencemask |=
+                OGS_NAS_EPS_ATTACH_ACCEPT_EMM_CAUSE_PRESENT;
+            attach_accept->emm_cause = EMM_CAUSE_CS_DOMAIN_NOT_AVAILABLE;
+        }
     } else {
         switch (eps_attach_result->result) {
             case OGS_NAS_ATTACH_TYPE_EPS_ATTACH: