246 lines
7.8 KiB
C
246 lines
7.8 KiB
C
/* The MSC-I role implementation variant that forwards requests to/from a remote MSC. */
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/*
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* (C) 2019 by sysmocom - s.m.f.c. GmbH <info@sysmocom.de>
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* All Rights Reserved
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*
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* SPDX-License-Identifier: AGPL-3.0+
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*
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* Author: Neels Hofmeyr
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <osmocom/core/fsm.h>
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#include <osmocom/msc/debug.h>
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#include <osmocom/msc/gsm_data.h>
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#include <osmocom/msc/msc_i_remote.h>
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#include <osmocom/msc/msc_roles.h>
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#include <osmocom/msc/msub.h>
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#include <osmocom/msc/msc_i.h>
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#include <osmocom/msc/e_link.h>
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static struct osmo_fsm msc_i_remote_fsm;
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static struct msc_i *msc_i_remote_priv(struct osmo_fsm_inst *fi)
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{
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OSMO_ASSERT(fi);
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OSMO_ASSERT(fi->fsm == &msc_i_remote_fsm);
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OSMO_ASSERT(fi->priv);
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return fi->priv;
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}
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/* 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
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* directly, it forwards the events to a remote MSC-I role, via E-over-GSUP.
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*
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* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
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* you are here^
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*/
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static int msc_i_remote_msg_down_to_remote_msc(struct msc_i *msc_i,
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enum osmo_gsup_message_type message_type,
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struct an_apdu *an_apdu)
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{
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struct osmo_gsup_message m;
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struct e_link *e = msc_i->c.remote_to;
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if (!e) {
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LOG_MSC_I_REMOTE(msc_i, LOGL_ERROR, "No E link to remote MSC, cannot send AN-APDU\n");
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return -1;
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}
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if (e_prep_gsup_msg(e, &m)) {
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LOG_MSC_I_REMOTE(msc_i, LOGL_ERROR, "Error composing E-interface GSUP message\n");
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return -1;
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}
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m.message_type = message_type;
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if (an_apdu) {
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if (gsup_msg_assign_an_apdu(&m, an_apdu)) {
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LOG_MSC_I_REMOTE(msc_i, LOGL_ERROR, "Error composing E-interface GSUP message\n");
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return -1;
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}
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}
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return e_tx(e, &m);
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}
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/* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a <-- msc_i_remote <---GSUP---- msc_a_remote <-- msc_i <--BSSMAP--- [BSS]
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* you are here^
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*/
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static int msc_i_remote_rx_gsup(struct msc_i *msc_i, const struct osmo_gsup_message *gsup_msg)
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{
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uint32_t event;
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struct an_apdu an_apdu;
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int rc;
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/* MSC_A_EV_FROM_I_COMPLETE_LAYER_3 will never occur with a remote MSC-I, since all Complete Layer 3 will happen
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* between a local MSC-A and local MSC-I roles. Only after an inter-MSC Handover will there possibly exist a
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* remote MSC-I, which is long after Complete Layer 3. */
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switch (gsup_msg->message_type) {
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case OSMO_GSUP_MSGT_E_PROCESS_ACCESS_SIGNALLING_REQUEST:
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case OSMO_GSUP_MSGT_E_PREPARE_SUBSEQUENT_HANDOVER_REQUEST:
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event = MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST;
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break;
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case OSMO_GSUP_MSGT_E_SEND_END_SIGNAL_REQUEST:
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event = MSC_A_EV_FROM_I_SEND_END_SIGNAL_REQUEST;
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break;
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case OSMO_GSUP_MSGT_E_CLOSE:
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case OSMO_GSUP_MSGT_E_ABORT:
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case OSMO_GSUP_MSGT_E_ROUTING_ERROR:
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msc_i_clear(msc_i);
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return 0;
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default:
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LOG_MSC_I_REMOTE(msc_i, LOGL_ERROR, "Unhandled GSUP message type: %s\n",
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osmo_gsup_message_type_name(gsup_msg->message_type));
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return -1;
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};
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/* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a <-- msc_i_remote <---GSUP---- msc_a_remote <-- msc_i <--BSSMAP--- [BSS]
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* ^you are here
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*/
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gsup_msg_to_an_apdu(&an_apdu, gsup_msg);
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rc = msub_role_dispatch(msc_i->c.msub, MSC_ROLE_A, event, &an_apdu);
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if (an_apdu.msg)
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msgb_free(an_apdu.msg);
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return rc;
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}
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static void msc_i_remote_fsm_ready(struct osmo_fsm_inst *fi, uint32_t event, void *data)
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{
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struct msc_i *msc_i = msc_i_remote_priv(fi);
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struct an_apdu *an_apdu;
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switch (event) {
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case MSC_REMOTE_EV_RX_GSUP:
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/* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a <-- msc_i_remote <---GSUP---- msc_a_remote <-- msc_i <--BSSMAP--- [BSS]
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* you are here^
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*/
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msc_i_remote_rx_gsup(msc_i, (const struct osmo_gsup_message*)data);
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return;
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case MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST:
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/* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
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* ^you are here
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*/
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an_apdu = data;
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msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_FORWARD_ACCESS_SIGNALLING_REQUEST, an_apdu);
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return;
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case MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_RESULT:
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/* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
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* ^you are here
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*/
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an_apdu = data;
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msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_PREPARE_SUBSEQUENT_HANDOVER_RESULT, an_apdu);
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return;
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case MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_ERROR:
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/* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
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* ^you are here
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*/
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an_apdu = data;
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msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_PREPARE_SUBSEQUENT_HANDOVER_ERROR, an_apdu);
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return;
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case MSC_I_EV_FROM_A_SEND_END_SIGNAL_RESPONSE:
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/* [MSC-A-----------------] [MSC-B-----------------]
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* msc_a --> msc_i_remote ----GSUP---> msc_a_remote --> msc_i ---BSSMAP--> [BSS]
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* ^you are here
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*/
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an_apdu = data;
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msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_SEND_END_SIGNAL_RESULT, an_apdu);
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return;
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default:
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OSMO_ASSERT(false);
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}
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}
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static void msc_i_remote_fsm_clearing_onenter(struct osmo_fsm_inst *fi, uint32_t prev_state)
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{
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osmo_fsm_inst_term(fi, OSMO_FSM_TERM_REGULAR, fi);
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}
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static void msc_i_remote_fsm_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause cause)
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{
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struct msc_i *msc_i = msc_i_remote_priv(fi);
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msc_i_remote_msg_down_to_remote_msc(msc_i, OSMO_GSUP_MSGT_E_CLOSE, NULL);
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}
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#define S(x) (1 << (x))
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static const struct osmo_fsm_state msc_i_remote_fsm_states[] = {
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[MSC_I_ST_READY] = {
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.name = "READY",
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.action = msc_i_remote_fsm_ready,
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.in_event_mask = 0
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| S(MSC_REMOTE_EV_RX_GSUP)
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| S(MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST)
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| S(MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_RESULT)
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| S(MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_ERROR)
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,
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.out_state_mask = 0
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| S(MSC_I_ST_CLEARING)
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,
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},
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[MSC_I_ST_CLEARING] = {
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.name = "CLEARING",
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.onenter = msc_i_remote_fsm_clearing_onenter,
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},
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};
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static struct osmo_fsm msc_i_remote_fsm = {
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.name = "msc_i_remote",
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.states = msc_i_remote_fsm_states,
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.num_states = ARRAY_SIZE(msc_i_remote_fsm_states),
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.log_subsys = DMSC,
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.event_names = msc_i_fsm_event_names,
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.cleanup = msc_i_remote_fsm_cleanup,
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};
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static __attribute__((constructor)) void msc_i_remote_fsm_init(void)
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{
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OSMO_ASSERT(osmo_fsm_register(&msc_i_remote_fsm) == 0);
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}
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struct msc_i *msc_i_remote_alloc(struct msub *msub, struct ran_infra *ran, struct e_link *e)
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{
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struct msc_i *msc_i;
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msub_role_alloc(msub, MSC_ROLE_I, &msc_i_remote_fsm, struct msc_i, ran);
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msc_i = msub_msc_i(msub);
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if (!msc_i)
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return NULL;
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e_link_assign(e, msc_i->c.fi);
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if (!msc_i->c.remote_to) {
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LOG_MSC_I_REMOTE(msc_i, LOGL_ERROR, "Failed to set up E link over GSUP to remote MSC\n");
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msc_i_clear(msc_i);
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return NULL;
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}
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return msc_i;
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}
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