From e454fc41d1e375bf5906c91a59c42a6cadd0840f Mon Sep 17 00:00:00 2001
From: francescomani <email@francescomani.it>
Date: Mon, 8 Sep 2025 10:59:11 +0200
Subject: [PATCH] Trigger MSG3 with C-RNTI in MAC CE if CBRA with
 newUE-Identity (handover)

---
 openair2/LAYER2/NR_MAC_UE/config_ue.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/openair2/LAYER2/NR_MAC_UE/config_ue.c b/openair2/LAYER2/NR_MAC_UE/config_ue.c
index 8951ef65e5..729f0b4763 100644
--- a/openair2/LAYER2/NR_MAC_UE/config_ue.c
+++ b/openair2/LAYER2/NR_MAC_UE/config_ue.c
@@ -1978,12 +1978,23 @@ static void handle_reconfiguration_with_sync(NR_UE_MAC_INST_t *mac,
   LOG_I(NR_MAC, "Configuring CRNTI %x\n", mac->crnti);
 
   RA_config_t *ra = &mac->ra;
+  bool is_cfra = false;
   if (reconfWithSync->rach_ConfigDedicated) {
     AssertFatal(reconfWithSync->rach_ConfigDedicated->present == NR_ReconfigurationWithSync__rach_ConfigDedicated_PR_uplink,
                 "RACH on supplementaryUplink not supported\n");
+    NR_RACH_ConfigDedicated_t *rach_ConfigDedicated = reconfWithSync->rach_ConfigDedicated->choice.uplink;
+    if (rach_ConfigDedicated->cfra)
+      is_cfra = true;
+    if (rach_ConfigDedicated->ext1 && rach_ConfigDedicated->ext1->cfra_TwoStep_r16)
+      is_cfra = true;
     UPDATE_IE(ra->rach_ConfigDedicated, reconfWithSync->rach_ConfigDedicated->choice.uplink, NR_RACH_ConfigDedicated_t);
   }
 
+  // in case of CBRA and reconfiguration with sync (handover)
+  // the UE sends MSG3 with C-RNTI to identify itself
+  if (!is_cfra)
+    mac->msg3_C_RNTI = true;
+
   if (reconfWithSync->spCellConfigCommon) {
     NR_ServingCellConfigCommon_t *scc = reconfWithSync->spCellConfigCommon;
     if (scc->physCellId)