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open5gs/src/mme/mme-gn-handler.c

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/*
* Copyright (C) 2023 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
*
* This file is part of Open5GS.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "mme-event.h"
#include "mme-sm.h"
#include "mme-context.h"
#include "mme-timer.h"
#include "mme-gtp-path.h"
#include "mme-fd-path.h"
#include "mme-path.h"
#include "mme-gn-build.h"
#include "mme-gn-handler.h"
#include "s1ap-path.h"
void mme_gn_handle_echo_request(
ogs_gtp_xact_t *xact, ogs_gtp1_echo_request_t *req)
{
ogs_assert(xact);
ogs_assert(req);
ogs_debug("[Gn] Receiving Echo Request");
/* FIXME : Implementing recovery counter correctly */
ogs_gtp1_send_echo_response(xact, 0);
}
void mme_gn_handle_echo_response(
ogs_gtp_xact_t *xact, ogs_gtp1_echo_response_t *req)
{
/* Not Implemented */
}
static int decode_global_enb_id(S1AP_Global_ENB_ID_t *glob_enb_id, const uint8_t *buf, size_t buf_len)
{
asn_dec_rval_t dec_ret = {0};
memset(glob_enb_id, 0, sizeof(S1AP_Global_ENB_ID_t));
dec_ret = aper_decode(NULL, &asn_DEF_S1AP_Global_ENB_ID, (void **)&glob_enb_id,
buf, buf_len, 0, 0);
if (dec_ret.code != RC_OK) {
ogs_warn("Failed to decode ASN-PDU [code:%d,consumed:%d]",
dec_ret.code, (int)dec_ret.consumed);
return OGS_ERROR;
}
if (ogs_log_get_domain_level(OGS_LOG_DOMAIN) >= OGS_LOG_TRACE)
asn_fprint(stdout, &asn_DEF_S1AP_Global_ENB_ID, glob_enb_id);
return OGS_OK;
}
/* 3GPP TS 23.003 2.8.2.2 Mapping from RAI and P-TMSI to GUT */
static void rai_ptmsi_to_guti(const ogs_nas_rai_t *rai, mme_p_tmsi_t ptmsi, uint32_t ptmsi_sig, ogs_nas_eps_guti_t *nas_guti)
{
uint16_t lac = be16toh(rai->lai.lac);;
nas_guti->nas_plmn_id =rai->lai.nas_plmn_id;
nas_guti->mme_gid = lac;
nas_guti->mme_code = rai->rac;
nas_guti->m_tmsi = 0xC0000000 | (ptmsi & 0x3f000000) | (ptmsi_sig & 0x00ff0000) | (ptmsi & 0x0000ffff);
}
/* TS 29.060 7.5.3 SGSN Context Request */
void mme_gn_handle_sgsn_context_request(
ogs_gtp_xact_t *xact, ogs_gtp1_sgsn_context_request_t *req)
{
ogs_nas_eps_guti_t nas_guti;
ogs_nas_rai_t *rai;
mme_ue_t *mme_ue = NULL;
int rv;
ogs_debug("[Gn] Rx SGSN Context Request");
if (!req->routeing_area_identity.presence) {
ogs_warn("[Gn] Rx SGSN Context Request with no RAI!");
mme_gtp1_send_sgsn_context_response(NULL, OGS_GTP1_CAUSE_MANDATORY_IE_MISSING, xact);
return;
}
if (req->routeing_area_identity.len != sizeof(*rai)) {
ogs_warn("[Gn] Rx SGSN Context Request RAI wrong size %u vs exp %zu!",
req->routeing_area_identity.len, sizeof(*rai));
mme_gtp1_send_sgsn_context_response(NULL, OGS_GTP1_CAUSE_MANDATORY_IE_INCORRECT, xact);
return;
}
if (!req->tunnel_endpoint_identifier_control_plane.presence) {
ogs_warn("[Gn] Rx SGSN Context Request with no Tunnel Endpoint Identifier Control Plane!");
mme_gtp1_send_sgsn_context_response(NULL, OGS_GTP1_CAUSE_MANDATORY_IE_MISSING, xact);
return;
}
if (!req->sgsn_address_for_control_plane.presence) {
ogs_warn("[Gn] Rx SGSN Context Request with no SGSN Address for Control Plane!");
mme_gtp1_send_sgsn_context_response(NULL, OGS_GTP1_CAUSE_MANDATORY_IE_MISSING, xact);
return;
}
if (!req->imsi.presence &&
!req->temporary_logical_link_identifier.presence &&
!req->packet_tmsi.presence) {
ogs_warn("[Gn] Rx SGSN Context Request with no IMSI/TLLI/P-TMSI!");
mme_gtp1_send_sgsn_context_response(NULL, OGS_GTP1_CAUSE_MANDATORY_IE_MISSING, xact);
return;
}
if (req->ms_validated.presence &&
(req->ms_validated.u8 & 0x01) /* 1=> "Yes" */
&& !req->imsi.presence) {
ogs_warn("[Gn] Rx SGSN Context Request with 'MS Validated' but no IMSI!");
mme_gtp1_send_sgsn_context_response(NULL, OGS_GTP1_CAUSE_MANDATORY_IE_MISSING, xact);
return;
}
rai = req->routeing_area_identity.data;
if (req->imsi.presence) {
mme_ue = mme_ue_find_by_imsi(req->imsi.data, req->imsi.len);
} else if (req->packet_tmsi.presence) { /* P-TMSI */
if (!req->p_tmsi_signature.presence) {
ogs_warn("[Gn] Rx SGSN Context Request with 'P-TMSI' but no P-TMSI Signature! Assuming value 0.");
req->p_tmsi_signature.u24 = 0;
}
rai_ptmsi_to_guti(rai, req->packet_tmsi.u32, req->p_tmsi_signature.u24, &nas_guti);
mme_ue = mme_ue_find_by_guti(&nas_guti);
} else if (req->temporary_logical_link_identifier.presence) {
if (!req->p_tmsi_signature.presence) {
ogs_warn("[Gn] Rx SGSN Context Request with 'TLLI' but no P-TMSI Signature! Assuming value 0.");
req->p_tmsi_signature.u24 = 0;
}
/* TS 29.060 7.5.3 "The TLLI/P-TMSI and RAI is a foreign TLLI/P-TMSI and an RAI in the old SGSN."
* A foregin TLLI is "tlli = (p_tmsi & 0x3fffffff) | 0x80000000", and since we only use 0x3fffffff
* bits of P-TMSI to derive the GUTI, it's totally fine passing the TLLI as P-TMSI. */
rai_ptmsi_to_guti(rai, req->temporary_logical_link_identifier.u32, req->p_tmsi_signature.u24, &nas_guti);
mme_ue = mme_ue_find_by_guti(&nas_guti);
}
if (!mme_ue) {
mme_gtp1_send_sgsn_context_response(NULL, OGS_GTP1_CAUSE_IMSI_IMEI_NOT_KNOWN, xact);
return;
}
mme_ue->gn.sgsn_gn_teid = req->tunnel_endpoint_identifier_control_plane.u32;
rv = ogs_gtp1_gsn_addr_to_ip(req->sgsn_address_for_control_plane.data,
req->sgsn_address_for_control_plane.len,
&mme_ue->gn.sgsn_gn_ip);
ogs_assert(rv == OGS_OK);
if (req->alternative_sgsn_address_for_control_plane.presence) {
rv = ogs_gtp1_gsn_addr_to_ip(req->alternative_sgsn_address_for_control_plane.data,
req->alternative_sgsn_address_for_control_plane.len,
&mme_ue->gn.sgsn_gn_ip_alt);
ogs_assert(rv == OGS_OK);
}
/* 3GPP TS 23.401 Annex D.3.5 "Routing Area Update":
* Step 2. "If the old P-TMSI Signature was valid or if the new SGSN indicates that it has authenticated the MS,
* the old SGSN starts a timer."
*/
ogs_timer_start(mme_ue->gn.t_gn_holding, mme_timer_cfg(MME_TIMER_GN_HOLDING)->duration);
mme_gtp1_send_sgsn_context_response(mme_ue, OGS_GTP1_CAUSE_REQUEST_ACCEPTED, xact);
}
/* TS 29.060 7.5.5 SGSN Context Acknowledge */
void mme_gn_handle_sgsn_context_acknowledge(
ogs_gtp_xact_t *xact, mme_ue_t *mme_ue, ogs_gtp1_sgsn_context_acknowledge_t *req)
{
int rv;
ogs_debug("[Gn] Rx SGSN Context Acknowledge");
rv = ogs_gtp_xact_commit(xact);
if (rv != OGS_OK) {
ogs_error("ogs_gtp_xact_commit() failed");
return;
}
if (!mme_ue) {
ogs_error("MME-UE Context has already been removed");
return;
}
/* 3GPP TS 23.060 6.9.1.2.2 Step 4), 3GPP TS 23.401 D.3.5 Step 4)
* The new SGSN sends an SGSN Context Acknowledge message to the old SGSN. The old MME (which is the old
* SGSN from the new SGSN's point of view) marks in its context that the information in the GWs and the HSS are
* invalid. This triggers the GWs, and the HSS to be updated if the UE initiates a Tracking Area Update procedure
* back to the old MME before completing the ongoing Routing Area Update procedure. If the security functions do
* not authenticate the MS correctly, then the routing area update shall be rejected, and the new SGSN shall send a
* reject indication to the old SGSN. The old MME shall continue as if the SGSN Context Request was never
* received.
* "NOTE 6: The new SGSN's operation is unmodified compared to pre-Rel-8. The old MME/S-GW (old SGSN from
* the new SGSN's point of view) does not forward any data towards the new SGSN." "*/
if (req->cause.u8 != OGS_GTP1_CAUSE_REQUEST_ACCEPTED) {
ogs_timer_stop(mme_ue->gn.t_gn_holding);
return;
}
/* 3GPP TS 23.060 6.9.1.2.2 Step 13)
* "If the old MME has an S1-MME association for the UE, the source MME sends a S1-U Release Command to the
* source eNodeB when receiving the SGSN Context Acknowledge message from the new SGSN. The RRC
* connection is released by the source eNodeB. The source eNodeB confirms the release of the RRC connection
* and of the S1-U connection by sending a S1-U Release Complete message to the source MME."
*/
if (mme_ue->enb_ue) {
rv = s1ap_send_ue_context_release_command(mme_ue->enb_ue,
S1AP_Cause_PR_nas, S1AP_CauseNas_normal_release,
S1AP_UE_CTX_REL_S1_REMOVE_AND_UNLINK, 0);
ogs_expect(rv == OGS_OK);
}
}
/* TS 29.060 7.5.14.1 */
void mme_gn_handle_ran_information_relay(
ogs_gtp_xact_t *xact, ogs_gtp1_ran_information_relay_t *req)
{
uint8_t discr;
ogs_eps_tai_t *target_tai;
S1AP_Global_ENB_ID_t global_ENB_ID;
uint32_t target_enb_id;
mme_enb_t *target_enb = NULL;
int rv;
ogs_debug("[Gn] Receiving RAN Information Relay");
if (req->ran_transparent_container.len == 0 ||
req->ran_transparent_container.data == NULL) {
ogs_warn("[Gn] Receiving RAN Information Relay with empty container!");
return;
}
/* "If RIM Routing Address Discriminator IE is not included, the RIM Routing
* Address shall be processed as an RNC identifier". Hence, not for us! */
if (req->rim_routing_address_discriminator.presence == false) {
ogs_warn("[Gn] Rx RAN Information Relay: no RIM Routing Address Discriminator!");
return;
}
if (req->rim_routing_address_discriminator.len != 1) {
ogs_warn("[Gn] Rx RAN Information Relay: RIM Routing Address Discriminator len != 1");
return;
}
/* 3GPP TS 48.018 RIM Routing Information IE */
discr = *((uint8_t*)req->rim_routing_address_discriminator.data) & 0x0f;
if (discr != 2) {/* 2: An eNB identifier is used to identify an E-UTRAN eNodeB or HeNB */
ogs_warn("[Gn] Rx RAN Information Relay: RIM Routing Address Discriminator %u unexpected", discr);
return;
}
if (req->rim_routing_address.presence == false) {
ogs_warn("[Gn] Rx RAN Information Relay: no RIM Routing Address!");
return;
}
if (req->rim_routing_address.len < sizeof(ogs_eps_tai_t)) {
ogs_warn("[Gn] Rx RAN Information Relay: RIM Routing Address len < %zu", sizeof(ogs_eps_tai_t));
return;
}
target_tai = req->rim_routing_address.data;
rv = decode_global_enb_id(&global_ENB_ID,
((uint8_t *)req->rim_routing_address.data) + sizeof(ogs_eps_tai_t),
req->rim_routing_address.len - sizeof(ogs_eps_tai_t));
if (rv != OGS_OK)
return;
ogs_s1ap_ENB_ID_to_uint32(&global_ENB_ID.eNB_ID, &target_enb_id);
ogs_debug(" Target : ENB_ID[%s:%d], TAC[%d]",
global_ENB_ID.eNB_ID.present ==
S1AP_ENB_ID_PR_homeENB_ID ? "Home" :
global_ENB_ID.eNB_ID.present ==
S1AP_ENB_ID_PR_macroENB_ID ? "Macro" : "Others",
target_enb_id, target_tai->tac);
target_enb = mme_enb_find_by_enb_id(target_enb_id);
if (target_enb == NULL) {
ogs_warn("[Gn] Rx RAN Information Relay: cannot find target eNB-id[0x%x]", target_enb_id);
return;
}
s1ap_send_mme_direct_information_transfer(
target_enb,
req->ran_transparent_container.data,
req->ran_transparent_container.len);
}
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