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/* The MSC-I 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_i_remote.h>
#include <osmocom/msc/msc_roles.h>
#include <osmocom/msc/msub.h>
#include <osmocom/msc/msc_i.h>
#include <osmocom/msc/e_link.h>
static struct osmo_fsm msc_i_remote_fsm;
static struct msc_i *msc_i_remote_priv(struct osmo_fsm_inst *fi)
{
OSMO_ASSERT(fi);
OSMO_ASSERT(fi->fsm == &msc_i_remote_fsm);
OSMO_ASSERT(fi->priv);
return fi->priv;
}
/* The idea is that this msc_i role is event-compatible to the "real" msc_i.c FSM, but instead of acting on the events
* directly, it forwards the events to a remote MSC-I role, via E-over-GSUP.
*
* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
* you are here^
*/
static int msc_i_remote_msg_down_to_remote_msc(struct msc_i *msc_i,
enum osmo_gsup_message_type message_type,
struct an_apdu *an_apdu)
{
struct osmo_gsup_message m;
struct e_link *e = msc_i->c.remote_to;
if (!e) {
LOG_MSC_I_REMOTE(msc_i, LOGL_ERROR, "No E link to remote MSC, cannot send AN-APDU\n");
return -1;
}
if (e_prep_gsup_msg(e, &m)) {
LOG_MSC_I_REMOTE(msc_i, 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_I_REMOTE(msc_i, LOGL_ERROR, "Error composing E-interface GSUP message\n");
return -1;
}
}
return e_tx(e, &m);
}
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a <-- msc_i_remote <---GSUP---- msc_a_remote <-- msc_i <--BSSMAP--- [BSS]
* you are here^
*/
static int msc_i_remote_rx_gsup(struct msc_i *msc_i, const struct osmo_gsup_message *gsup_msg)
{
uint32_t event;
struct an_apdu an_apdu;
int rc;
/* MSC_A_EV_FROM_I_COMPLETE_LAYER_3 will never occur with a remote MSC-I, since all Complete Layer 3 will happen
* between a local MSC-A and local MSC-I roles. Only after an inter-MSC Handover will there possibly exist a
* remote MSC-I, which is long after Complete Layer 3. */
switch (gsup_msg->message_type) {
case OSMO_GSUP_MSGT_E_PROCESS_ACCESS_SIGNALLING_REQUEST:
case OSMO_GSUP_MSGT_E_PREPARE_SUBSEQUENT_HANDOVER_REQUEST:
event = MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST;
break;
case OSMO_GSUP_MSGT_E_SEND_END_SIGNAL_REQUEST:
event = MSC_A_EV_FROM_I_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_i_clear(msc_i);
return 0;
default:
LOG_MSC_I_REMOTE(msc_i, 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_i_remote <---GSUP---- msc_a_remote <-- msc_i <--BSSMAP--- [BSS]
* ^you are here
*/
gsup_msg_to_an_apdu(&an_apdu, gsup_msg);
rc = msub_role_dispatch(msc_i->c.msub, MSC_ROLE_A, event, &an_apdu);
if (an_apdu.msg)
msgb_free(an_apdu.msg);
return rc;
}
static void msc_i_remote_fsm_ready(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct msc_i *msc_i = msc_i_remote_priv(fi);
struct an_apdu *an_apdu;
switch (event) {
case MSC_REMOTE_EV_RX_GSUP:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a <-- msc_i_remote <---GSUP---- msc_a_remote <-- msc_i <--BSSMAP--- [BSS]
* you are here^
*/
msc_i_remote_rx_gsup(msc_i, (const struct osmo_gsup_message*)data);
return;
case MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
* ^you are here
*/
an_apdu = data;
msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_FORWARD_ACCESS_SIGNALLING_REQUEST, an_apdu);
return;
case MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_RESULT:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
* ^you are here
*/
an_apdu = data;
msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_PREPARE_SUBSEQUENT_HANDOVER_RESULT, an_apdu);
return;
case MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_ERROR:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
* ^you are here
*/
an_apdu = data;
msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_PREPARE_SUBSEQUENT_HANDOVER_ERROR, an_apdu);
return;
case MSC_I_EV_FROM_A_SEND_END_SIGNAL_RESPONSE:
/* [MSC-A-----------------] [MSC-B-----------------]
* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
* ^you are here
*/
an_apdu = data;
msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_SEND_END_SIGNAL_RESULT, an_apdu);
return;
default:
OSMO_ASSERT(false);
}
}
static void msc_i_remote_fsm_clearing_onenter(struct osmo_fsm_inst *fi, uint32_t prev_state)
{
osmo_fsm_inst_term(fi, OSMO_FSM_TERM_REGULAR, fi);
}
static void msc_i_remote_fsm_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause cause)
{
struct msc_i *msc_i = msc_i_remote_priv(fi);
msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_CLOSE, NULL);
}
#define S(x) (1 << (x))
static const struct osmo_fsm_state msc_i_remote_fsm_states[] = {
[MSC_I_ST_READY] = {
.name = "READY",
.action = msc_i_remote_fsm_ready,
.in_event_mask = 0
| S(MSC_REMOTE_EV_RX_GSUP)
| S(MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST)
| S(MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_RESULT)
| S(MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_ERROR)
,
.out_state_mask = 0
| S(MSC_I_ST_CLEARING)
,
},
[MSC_I_ST_CLEARING] = {
.name = "CLEARING",
.onenter = msc_i_remote_fsm_clearing_onenter,
},
};
static struct osmo_fsm msc_i_remote_fsm = {
.name = "msc_i_remote",
.states = msc_i_remote_fsm_states,
.num_states = ARRAY_SIZE(msc_i_remote_fsm_states),
.log_subsys = DMSC,
.event_names = msc_i_fsm_event_names,
.cleanup = msc_i_remote_fsm_cleanup,
};
static __attribute__((constructor)) void msc_i_remote_fsm_init(void)
{
OSMO_ASSERT(osmo_fsm_register(&msc_i_remote_fsm) == 0);
}
struct msc_i *msc_i_remote_alloc(struct msub *msub, struct ran_infra *ran, struct e_link *e)
{
struct msc_i *msc_i;
msub_role_alloc(msub, MSC_ROLE_I, &msc_i_remote_fsm, struct msc_i, ran);
msc_i = msub_msc_i(msub);
if (!msc_i)
return NULL;
e_link_assign(e, msc_i->c.fi);
if (!msc_i->c.remote_to) {
LOG_MSC_I_REMOTE(msc_i, LOGL_ERROR, "Failed to set up E link over GSUP to remote MSC\n");
msc_i_clear(msc_i);
return NULL;
}
return msc_i;
}
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