Fix: store CellGroupConfig from initial UL RRC message

This F1 message sends us the CellGroupConfig of the UE. Store it in case
we need it. For instance, at least in OAI, it is possible to make a
handover without a DRB (this might or might not be standard compliant).
However, in this case, we did never receive a UE context setup request,
which stores the CellGroupConfig. Hence, store the first CellGroupConfig
we receive, to be able to do e.g., handover.

openair2/RRC/NR/rrc_gNB.c

@@ -1029,9 +1029,18 @@ static void rrc_handle_RRCSetupRequest(gNB_RRC_INST *rrc,
     return;
   }
 
+  NR_CellGroupConfig_t *cellGroupConfig = NULL;
+  asn_dec_rval_t dec_rval = uper_decode_complete(NULL,
+                                                 &asn_DEF_NR_CellGroupConfig,
+                                                 (void **)&cellGroupConfig,
+                                                 msg->du2cu_rrc_container,
+                                                 msg->du2cu_rrc_container_length);
+  AssertFatal(dec_rval.code == RC_OK && dec_rval.consumed > 0, "Cell group config decode error\n");
+
   gNB_RRC_UE_t *UE = &ue_context_p->ue_context;
   UE = &ue_context_p->ue_context;
   UE->establishment_cause = rrcSetupRequest->establishmentCause;
+  UE->masterCellGroup = cellGroupConfig;
   activate_srb(UE, 1);
   rrc_gNB_generate_RRCSetup(0, msg->crnti, ue_context_p, msg->du2cu_rrc_container, msg->du2cu_rrc_container_length);
 }