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/* The MSC-T role implementation variant that forwards requests to/from a remote MSC. */
/*
* (C) 2019 by sysmocom - s.m.f.c. GmbH <info@sysmocom.de>
* All Rights Reserved
*
* SPDX-License-Identifier: AGPL-3.0+
*
* Author: Neels Hofmeyr
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <osmocom/core/fsm.h>
#include <osmocom/msc/debug.h>
#include <osmocom/msc/gsm_data.h>
#include <osmocom/msc/msc_t_remote.h>
#include <osmocom/msc/msc_roles.h>
#include <osmocom/msc/msub.h>
#include <osmocom/msc/msc_t.h>
#include <osmocom/msc/e_link.h>
static struct osmo_fsm msc_t_remote_fsm;
static struct msc_t *msc_t_remote_priv(struct osmo_fsm_inst *fi)
{
OSMO_ASSERT(fi);
OSMO_ASSERT(fi->fsm == &msc_t_remote_fsm);
OSMO_ASSERT(fi->priv);
return fi->priv;
}
/* The idea is that this msc_t role is event-compatible to the "real" msc_t.c FSM, but instead of acting on the events
* directly, it forwards the events to a remote MSC-T role, via E-over-GSUP.
*
* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_t_remote ----GSUP---> msc_a_remote --> msc_t ---BSSMAP--> [BSS]
* you are here^
*/
static int msc_t_remote_msg_down_to_remote_msc(struct msc_t *msc_t,
enum osmo_gsup_message_type message_type,
struct an_apdu *an_apdu)
{
struct osmo_gsup_message m;
struct e_link *e = msc_t->c.remote_to;
if (!e) {
LOG_MSC_T_REMOTE(msc_t, LOGL_ERROR, "No E link to remote MSC, cannot send AN-APDU\n");
return -1;
}
if (e_prep_gsup_msg(e, &m)) {
LOG_MSC_T_REMOTE(msc_t, LOGL_ERROR, "Error composing E-interface GSUP message\n");
return -1;
}
m.message_type = message_type;
if (an_apdu) {
if (gsup_msg_assign_an_apdu(&m, an_apdu)) {
LOG_MSC_T_REMOTE(msc_t, LOGL_ERROR, "Error composing E-interface GSUP message\n");
return -1;
}
}
return e_tx(e, &m);
}
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a <-- msc_t_remote <---GSUP---- msc_a_remote <-- msc_t <--BSSMAP--- [BSS]
* you are here^
*/
static int msc_t_remote_rx_gsup(struct msc_t *msc_t, const struct osmo_gsup_message *gsup_msg)
{
uint32_t event;
struct an_apdu an_apdu;
int rc;
switch (gsup_msg->message_type) {
case OSMO_GSUP_MSGT_E_PROCESS_ACCESS_SIGNALLING_REQUEST:
event = MSC_A_EV_FROM_T_PROCESS_ACCESS_SIGNALLING_REQUEST;
break;
case OSMO_GSUP_MSGT_E_PREPARE_HANDOVER_ERROR:
case OSMO_GSUP_MSGT_E_PREPARE_HANDOVER_RESULT:
event = MSC_A_EV_FROM_T_PREPARE_HANDOVER_RESPONSE;
break;
case OSMO_GSUP_MSGT_E_SEND_END_SIGNAL_REQUEST:
event = MSC_A_EV_FROM_T_SEND_END_SIGNAL_REQUEST;
break;
case OSMO_GSUP_MSGT_E_CLOSE:
case OSMO_GSUP_MSGT_E_ABORT:
case OSMO_GSUP_MSGT_E_ROUTING_ERROR:
msc_t_clear(msc_t);
return 0;
default:
LOG_MSC_T_REMOTE(msc_t, LOGL_ERROR, "Unhandled GSUP message type: %s\n",
osmo_gsup_message_type_name(gsup_msg->message_type));
return -1;
};
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a <-- msc_t_remote <---GSUP---- msc_a_remote <-- msc_t <--BSSMAP--- [BSS]
* ^you are here
*/
gsup_msg_to_an_apdu(&an_apdu, gsup_msg);
rc = msub_role_dispatch(msc_t->c.msub, MSC_ROLE_A, event, &an_apdu);
if (an_apdu.msg)
msgb_free(an_apdu.msg);
return rc;
}
static void msc_t_remote_fsm_ready(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct msc_t *msc_t = msc_t_remote_priv(fi);
struct an_apdu *an_apdu;
switch (event) {
case MSC_REMOTE_EV_RX_GSUP:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a <-- msc_t_remote <---GSUP---- msc_a_remote <-- msc_t <--BSSMAP--- [BSS]
* you are here^
*/
msc_t_remote_rx_gsup(msc_t, (const struct osmo_gsup_message*)data);
return;
case MSC_T_EV_FROM_A_PREPARE_HANDOVER_REQUEST:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_t_remote ----GSUP---> going to create an msc_t if the request succeeds
* ^you are here
*/
an_apdu = data;
msc_t_remote_msg_down_to_remote_msc(msc_t, OSMO_GSUP_MSGT_E_PREPARE_HANDOVER_REQUEST, an_apdu);
return;
case MSC_T_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_t_remote ----GSUP---> msc_a_remote --> msc_t ---BSSMAP--> [BSS]
* ^you are here
*/
an_apdu = data;
msc_t_remote_msg_down_to_remote_msc(msc_t, OSMO_GSUP_MSGT_E_FORWARD_ACCESS_SIGNALLING_REQUEST, an_apdu);
return;
default:
OSMO_ASSERT(false);
}
}
static void msc_t_remote_fsm_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause cause)
{
struct msc_t *msc_t = msc_t_remote_priv(fi);
if (msc_t->c.remote_to)
msc_t_remote_msg_down_to_remote_msc(msc_t, OSMO_GSUP_MSGT_E_CLOSE, NULL);
}
#define S(x) (1 << (x))
static const struct osmo_fsm_state msc_t_remote_fsm_states[] = {
/* An FSM instance always starts in state 0. Define one just to be able to state_chg out of it. Root reason is
* that we're using MSC_T_ST_* enum values from msc_t.c, but don't need the first
* MSC_T_ST_PENDING_FIRST_CO_INITIAL_MSG. */
[0] = {
.name = "0",
.out_state_mask = 0
| S(MSC_T_ST_WAIT_HO_COMPLETE)
,
},
[MSC_T_ST_WAIT_HO_COMPLETE] = {
.name = "WAIT_HO_COMPLETE",
.action = msc_t_remote_fsm_ready,
.in_event_mask = 0
| S(MSC_REMOTE_EV_RX_GSUP)
| S(MSC_T_EV_FROM_A_PREPARE_HANDOVER_REQUEST)
| S(MSC_T_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST)
,
},
};
static struct osmo_fsm msc_t_remote_fsm = {
.name = "msc_t_remote",
.states = msc_t_remote_fsm_states,
.num_states = ARRAY_SIZE(msc_t_remote_fsm_states),
.log_subsys = DMSC,
.event_names = msc_t_fsm_event_names,
.cleanup = msc_t_remote_fsm_cleanup,
};
static __attribute__((constructor)) void msc_t_remote_fsm_init(void)
{
OSMO_ASSERT(osmo_fsm_register(&msc_t_remote_fsm) == 0);
}
struct msc_t *msc_t_remote_alloc(struct msub *msub, struct ran_infra *ran,
const uint8_t *remote_msc_name, size_t remote_msc_name_len)
{
struct msc_t *msc_t;
msub_role_alloc(msub, MSC_ROLE_T, &msc_t_remote_fsm, struct msc_t, ran);
msc_t = msub_msc_t(msub);
if (!msc_t)
return NULL;
msc_t->c.remote_to = e_link_alloc(msub_net(msub)->gcm, msc_t->c.fi, remote_msc_name, remote_msc_name_len);
if (!msc_t->c.remote_to) {
LOG_MSC_T_REMOTE(msc_t, LOGL_ERROR, "Failed to set up E link over GSUP to remote MSC\n");
msc_t_clear(msc_t);
return NULL;
}
osmo_fsm_inst_state_chg(msc_t->c.fi, MSC_T_ST_WAIT_HO_COMPLETE, 0, 0);
return msc_t;
}
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