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Diffstat (limited to 'src/libmsc/msc_i_remote.c')
| -rw-r--r-- | src/libmsc/msc_i_remote.c | 245 |
1 files changed, 245 insertions, 0 deletions
diff --git a/src/libmsc/msc_i_remote.c b/src/libmsc/msc_i_remote.c new file mode 100644 index 000000000..86c7b9c54 --- /dev/null +++ b/src/libmsc/msc_i_remote.c @@ -0,0 +1,245 @@ +/* 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, MSC_ROLE_A, &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; +} |