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Add NGAP Handover Request decoding and RRC handler

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This commit introduces the NG Mobility Management Procedure known as
Handover Resource Allocation. The inbound message is sent by the AMF
and is known as Handover Request.

Major changes:

(0) Add Handover Resource Allocation initiating message decoding
    * add case for NGAP initiating message and unsuccessful message decoding
(1) handle Handover Request on the target NG-RAN
(2) decode NG Handover Request message
(3) process payload, e.g. create UE context,
    store IDs, set UP security and trigger bearer setup

Co-authored-by: batuhan duyuler <batuhan.duyuler@firecell.io>
This commit is contained in:
Guido Casati
2025-09-18 11:34:30 +02:00
co-authored by batuhan duyuler
parent 92abefb815
commit 461cfb7911
16 changed files with 525 additions and 104 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openair2/COMMON/ngap_messages_def.h
+1
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@@ -83,6 +83,7 @@ MESSAGE_DEF(NGAP_PDUSESSION_SETUP_REQ , MESSAGE_PRIORITY_MED, ngap_pd
MESSAGE_DEF(NGAP_PDUSESSION_MODIFY_REQ , MESSAGE_PRIORITY_MED, ngap_pdusession_modify_req_t , ngap_pdusession_modify_req )
MESSAGE_DEF(NGAP_PDUSESSION_RELEASE_COMMAND , MESSAGE_PRIORITY_MED, ngap_pdusession_release_command_t , ngap_pdusession_release_command)
MESSAGE_DEF(NGAP_UE_CONTEXT_RELEASE_COMMAND, MESSAGE_PRIORITY_MED, ngap_ue_release_command_t , ngap_ue_release_command)
MESSAGE_DEF(NGAP_HANDOVER_REQUEST, MESSAGE_PRIORITY_MED, ngap_handover_request_t, ngap_handover_request)
/* NGAP <-> RRC messages (can be initiated either by MME or gNB) */
MESSAGE_DEF(NGAP_UE_CONTEXT_RELEASE_REQ , MESSAGE_PRIORITY_MED, ngap_ue_release_req_t , ngap_ue_release_req)
openair2/COMMON/ngap_messages_types.h
+59 -9
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@@ -67,6 +67,7 @@
#define NGAP_PAGING_IND(mSGpTR) (mSGpTR)->ittiMsg.ngap_paging_ind
#define NGAP_HANDOVER_REQUIRED(mSGpTR) (mSGpTR)->ittiMsg.ngap_handover_required
#define NGAP_HANDOVER_FAILURE(mSGpTR) (mSGpTR)->ittiMsg.ngap_handover_failure
#define NGAP_HANDOVER_REQUEST(mSGpTR) (mSGpTR)->ittiMsg.ngap_handover_request
#define NGAP_UE_CONTEXT_RELEASE_REQ(mSGpTR) (mSGpTR)->ittiMsg.ngap_ue_release_req
#define NGAP_PDUSESSION_RELEASE_COMMAND(mSGpTR) (mSGpTR)->ittiMsg.ngap_pdusession_release_command
@@ -229,6 +230,15 @@ typedef struct ngap_mobility_restriction_s{
plmn_id_t serving_plmn;
}ngap_mobility_restriction_t;
/* PDU Session Resource Setup Request Transfer (9.3.4.1 3GPP TS 38.413) */
typedef struct {
uint8_t nb_qos;
pdusession_level_qos_parameter_t qos[QOSFLOW_MAX_VALUE];
pdu_session_type_t pdu_session_type;
// UPF endpoint of the NG-U (N3) transport bearer
gtpu_tunnel_t n3_incoming;
} pdusession_transfer_t;
typedef enum pdusession_qosflow_mapping_ind_e{
QOSFLOW_MAPPING_INDICATION_UL = 0,
QOSFLOW_MAPPING_INDICATION_DL = 1,
@@ -558,6 +568,55 @@ typedef struct {
ngap_cause_t cause;
} ngap_handover_failure_t;
typedef struct {
// Next-Hop NH
uint8_t next_hop[SECURITY_KEY_LENGTH];
// Next Hop Chaining Count
uint8_t next_hop_chain_count;
} ngap_security_context_t;
/* Handover Request (3GPP TS 38.413 9.2.3.4)
PDU Session Resource Setup Item */
typedef struct {
// PDU Session ID
uint8_t pdusession_id;
pdu_session_type_t pdu_session_type;
// S-NSSAI
nssai_t nssai;
// Handover Required Transfer
pdusession_transfer_t pdusessionTransfer;
} ho_request_pdusession_t;
/* 3GPP TS 38.413 9.2.3.4 */
typedef struct {
// AMF UE NGAP ID
uint64_t amf_ue_ngap_id;
// Handover Type
ho_type_t ho_type;
// Cause
ngap_cause_t cause;
// UE Aggregate Maximum Bit Rate
ngap_ambr_t ue_ambr;
// UE Security Capabilities
ngap_security_capabilities_t security_capabilities;
// Security Context
ngap_security_context_t security_context;
// PDU Session Resource Setup List
uint8_t nb_of_pdusessions;
ho_request_pdusession_t pduSessionResourceSetupList[NGAP_MAX_PDU_SESSION];
// Allowed NSSAI
uint8_t nb_allowed_nssais;
nssai_t allowed_nssai[8];
// Source to Target Transparent Container contents
uint64_t nr_cell_id;
byte_array_t ue_ho_prep_info;
byte_array_t ue_cap;
// Mobility Restriction List
ngap_mobility_restriction_t *mobility_restriction;
// GUAMI
nr_guami_t guami;
} ngap_handover_request_t;
typedef struct ngap_ue_cap_info_ind_s {
uint32_t gNB_ue_ngap_id;
byte_array_t ue_radio_cap;
@@ -628,15 +687,6 @@ typedef struct ngap_downlink_nas_s {
byte_array_t nas_pdu;
} ngap_downlink_nas_t;
/* PDU Session Resource Setup Request Transfer (9.3.4.1 3GPP TS 38.413) */
typedef struct {
uint8_t nb_qos;
pdusession_level_qos_parameter_t qos[QOSFLOW_MAX_VALUE];
pdu_session_type_t pdu_session_type;
// UPF endpoint of the NG-U (N3) transport bearer
gtpu_tunnel_t n3_incoming;
} pdusession_transfer_t;
/* PDU Session Resource Setup/Modify Request Item */
typedef struct {
int pdusession_id;
openair2/RRC/NR/nr_rrc_proto.h
+1
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@@ -127,5 +127,6 @@ f1ap_qos_flow_param_t get_qos_char_from_qos_flow_param(const pdusession_level_qo
void openair_rrc_gNB_configuration(gNB_RRC_INST *rrc, gNB_RrcConfigurationReq *configuration);
NR_SRB_ToAddModList_t *createSRBlist(gNB_RRC_UE_t *ue, uint8_t reestablish);
NR_DRB_ToAddModList_t *createDRBlist(gNB_RRC_UE_t *ue, bool reestablish);
void activate_srb(gNB_RRC_UE_t *UE, int srb_id);
#endif
openair2/RRC/NR/rrc_gNB.c
+6 -1
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@@ -354,7 +354,7 @@ void freeSRBlist(NR_SRB_ToAddModList_t *l)
ASN_STRUCT_FREE(asn_DEF_NR_SRB_ToAddModList, l);
}
static void activate_srb(gNB_RRC_UE_t *UE, int srb_id)
void activate_srb(gNB_RRC_UE_t *UE, int srb_id)
{
AssertFatal(srb_id == 1 || srb_id == 2, "handling only SRB 1 or 2\n");
if (UE->Srb[srb_id].Active == 1) {
@@ -2944,6 +2944,11 @@ void *rrc_gnb_task(void *args_p) {
rrc_gNB_process_PAGING_IND(msg_p, instance);
break;
case NGAP_HANDOVER_REQUEST:
rrc_gNB_process_Handover_Request(RC.nrrrc[instance], instance, &NGAP_HANDOVER_REQUEST(msg_p));
rrc_gNB_free_Handover_Request(&NGAP_HANDOVER_REQUEST(msg_p)); // Free transfered NG message
break;
default:
LOG_E(NR_RRC, "[gNB %ld] Received unexpected message %s\n", instance, msg_name_p);
break;
openair2/RRC/NR/rrc_gNB_NGAP.c
+95 -6
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@@ -83,6 +83,8 @@
#include "rrc_messages_types.h"
#include "s1ap_messages_types.h"
#include "uper_encoder.h"
#include "rrc_gNB_mobility.h"
#include "rrc_gNB_du.h"
#ifdef E2_AGENT
#include "openair2/E2AP/RAN_FUNCTION/O-RAN/ran_func_rc_extern.h"
@@ -163,18 +165,24 @@ static nr_guami_t get_guami(const uint32_t amf_Id, const plmn_id_t plmn)
return guami;
}
/** @brief Copy NGAP PDU Session Transfer item to RRC pdusession_t struct */
static void cp_pdusession_transfer_to_pdusession(pdusession_t *dst, const pdusession_transfer_t *src)
{
dst->nb_qos = src->nb_qos;
for (uint8_t i = 0; i < src->nb_qos && i < QOSFLOW_MAX_VALUE; ++i) {
dst->qos[i] = src->qos[i];
}
dst->pdu_session_type = src->pdu_session_type;
dst->n3_incoming = src->n3_incoming;
}
/** @brief Copy NGAP PDU Session Resource item to RRC pdusession_t struct */
static void cp_pdusession_resource_item_to_pdusession(pdusession_t *dst, const pdusession_resource_item_t *src)
{
dst->pdusession_id = src->pdusession_id;
dst->nas_pdu = src->nas_pdu;
dst->nb_qos = src->pdusessionTransfer.nb_qos;
for (uint8_t i = 0; i < src->pdusessionTransfer.nb_qos && i < QOSFLOW_MAX_VALUE; ++i) {
dst->qos[i] = src->pdusessionTransfer.qos[i];
}
dst->pdu_session_type = src->pdusessionTransfer.pdu_session_type;
dst->n3_incoming = src->pdusessionTransfer.n3_incoming;
dst->nssai = src->nssai;
cp_pdusession_transfer_to_pdusession(dst, &src->pdusessionTransfer);
}
/**
@@ -1072,6 +1080,87 @@ void rrc_gNB_send_NGAP_HANDOVER_FAILURE(gNB_RRC_INST *rrc, ngap_handover_failure
itti_send_msg_to_task(TASK_NGAP, rrc->module_id, msg_p);
}
/** @brief Process NG Handover Request message (8.4.2.2 3GPP TS 38.413) */
int rrc_gNB_process_Handover_Request(gNB_RRC_INST *rrc, instance_t instance, ngap_handover_request_t *msg)
{
LOG_I(NR_RRC, "Received Handover Request (on PCI=%lu) \n", msg->nr_cell_id);
struct nr_rrc_du_container_t *du = get_du_by_cell_id(rrc, msg->nr_cell_id);
if (du == NULL) {
/* Cell Not Found! Return HO Request Failure*/
LOG_E(RRC, "Failed to process Handover Request: no DU found with PCI=%lu \n", msg->nr_cell_id);
ngap_handover_failure_t fail = {
.amf_ue_ngap_id = msg->amf_ue_ngap_id,
.cause.type = NGAP_CAUSE_RADIO_NETWORK,
.cause.value = NGAP_CAUSE_RADIO_NETWORK_RADIO_RESOURCES_NOT_AVAILABLE,
};
rrc_gNB_send_NGAP_HANDOVER_FAILURE(rrc, &fail);
return -1;
}
// Create UE context
sctp_assoc_t curr_assoc_id = du->assoc_id;
rrc_gNB_ue_context_t *ue_context_p = rrc_gNB_create_ue_context(curr_assoc_id, UINT16_MAX, rrc, UINT64_MAX, UINT32_MAX);
gNB_RRC_UE_t *UE = &ue_context_p->ue_context;
// allocate context for target
if (UE->ho_context != NULL) {
LOG_E(NR_RRC, "Ongoing handover for UE %d, cannot trigger new\n", UE->rrc_ue_id);
return -1;
}
UE->ho_context = alloc_ho_ctx(HO_CTX_TARGET);
// Store IDs in UE context
UE->amf_ue_ngap_id = msg->amf_ue_ngap_id;
UE->ue_guami = msg->guami;
UE->ho_context->target->ue_ho_prep_info = copy_byte_array(msg->ue_ho_prep_info);
// store the received UE Security Capabilities in the UE context
FREE_AND_ZERO_BYTE_ARRAY(UE->ue_cap_buffer);
UE->ue_cap_buffer = copy_byte_array(msg->ue_cap);
/* store the received Security Context in the UE context
and take it into use as defined in TS 33.501 */
set_UE_security_algos(rrc, UE, &msg->security_capabilities);
UE->nh_ncc = msg->security_context.next_hop_chain_count;
memcpy(UE->nh, msg->security_context.next_hop, SECURITY_KEY_LENGTH);
// Reset KgNB
memset(UE->kgnb, 0, SECURITY_KEY_LENGTH);
// Derive KgNB*
const f1ap_served_cell_info_t *cell_info = &du->setup_req->cell[0].info;
uint32_t ssb_arfcn = get_ssb_arfcn(du);
nr_derive_key_ng_ran_star(cell_info->nr_pci, ssb_arfcn, UE->nh, UE->kgnb);
UE->as_security_active = true;
// Activate SRBs
activate_srb(UE, SRB1);
activate_srb(UE, SRB2);
nr_rrc_pdcp_config_security(UE, false);
// Copy PDU Session Resource Setup item to RRC struct and do PDU Session Resource Setup procedure
pdusession_t to_setup = {
.nssai = msg->pduSessionResourceSetupList->nssai,
.pdu_session_type = msg->pduSessionResourceSetupList->pdu_session_type ,
.pdusession_id = msg->pduSessionResourceSetupList->pdusession_id,
};
cp_pdusession_transfer_to_pdusession(&to_setup, &msg->pduSessionResourceSetupList->pdusessionTransfer);
if (!trigger_bearer_setup(rrc, UE, msg->nb_of_pdusessions, &to_setup, msg->ue_ambr.br_dl)) {
LOG_E(NR_RRC, "Failed to establish PDU session: handover failed\n");
ngap_handover_failure_t fail = {
.amf_ue_ngap_id = msg->amf_ue_ngap_id,
.cause.type = NGAP_CAUSE_RADIO_NETWORK,
.cause.value = NGAP_CAUSE_RADIO_NETWORK_HO_FAILURE_IN_TARGET_5GC_NGRAN_NODE_OR_TARGET_SYSTEM,
};
rrc_gNB_send_NGAP_HANDOVER_FAILURE(rrc, &fail);
}
return 0;
}
void rrc_gNB_free_Handover_Request(ngap_handover_request_t *msg)
{
free_byte_array(msg->ue_cap);
free_byte_array(msg->ue_ho_prep_info);
free(msg->mobility_restriction);
}
/*
* Process the NG command NGAP_UE_CONTEXT_RELEASE_COMMAND, sent by AMF.
* The gNB should remove all pdu session, NG context, and other context of the UE.
openair2/RRC/NR/rrc_gNB_NGAP.h
+3
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@@ -96,4 +96,7 @@ void rrc_gNB_send_NGAP_HANDOVER_REQUIRED(gNB_RRC_INST *rrc,
void rrc_gNB_send_NGAP_HANDOVER_FAILURE(gNB_RRC_INST *rrc, ngap_handover_failure_t *msg);
int rrc_gNB_process_Handover_Request(gNB_RRC_INST *rrc, instance_t instance, ngap_handover_request_t *msg);
void rrc_gNB_free_Handover_Request(ngap_handover_request_t *msg);
#endif
openair2/RRC/NR/rrc_gNB_mobility.c
+2
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@@ -57,6 +57,8 @@ nr_handover_context_t *alloc_ho_ctx(ho_ctx_type_t type)
static void free_ho_ctx(nr_handover_context_t *ho_ctx)
{
free(ho_ctx->source);
if (ho_ctx->target)
FREE_AND_ZERO_BYTE_ARRAY(ho_ctx->target->ue_ho_prep_info);
free(ho_ctx->target);
free(ho_ctx);
}
openair2/RRC/NR/rrc_gNB_mobility.h
+2
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@@ -63,6 +63,8 @@ typedef struct nr_ho_target_cu {
uint32_t du_ue_id;
/// new (target) RNTI (as for du_ue_id)
rnti_t new_rnti;
/// Handover Preparation Buffer
byte_array_t ue_ho_prep_info;
/// function pointer to announce handover request acknowledgment
ho_req_ack_t ho_req_ack;
/// function pointer to announce handover success