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osmo-msc/src/libmsc/msc_ho.c

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/* MSC Handover implementation */
/*
* (C) 2019 by sysmocom - s.m.f.c. GmbH <info@sysmocom.de>
* All Rights Reserved
*
* Author: Neels Hofmeyr
*
* SPDX-License-Identifier: GPL-2.0+
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <osmocom/core/fsm.h>
#include <osmocom/gsm/protocol/gsm_08_08.h>
#include <osmocom/sigtran/sccp_helpers.h>
#include <osmocom/msc/msc_ho.h>
#include <osmocom/msc/ran_msg.h>
#include <osmocom/msc/msc_a.h>
#include <osmocom/msc/msc_i.h>
#include <osmocom/msc/msc_t.h>
#include <osmocom/msc/e_link.h>
#include <osmocom/msc/msc_i_remote.h>
#include <osmocom/msc/msc_t_remote.h>
#include <osmocom/msc/neighbor_ident.h>
#include <osmocom/msc/gsm_data.h>
#include <osmocom/msc/ran_peer.h>
#include <osmocom/msc/vlr.h>
#include <osmocom/msc/transaction.h>
#include <osmocom/msc/gsm_04_08.h>
#include <osmocom/msc/call_leg.h>
#include <osmocom/msc/rtp_stream.h>
#include <osmocom/msc/mncc_call.h>
struct osmo_fsm msc_ho_fsm;
#define MSC_A_USE_HANDOVER "Handover"
static const struct osmo_tdef_state_timeout msc_ho_fsm_timeouts[32] = {
[MSC_HO_ST_REQUIRED] = { .keep_timer = true, .T = -3 },
[MSC_HO_ST_WAIT_REQUEST_ACK] = { .keep_timer = true },
[MSC_HO_ST_WAIT_COMPLETE] = { .T = -3 },
};
/* Transition to a state, using the T timer defined in msc_a_fsm_timeouts.
* The actual timeout value is in turn obtained from network->T_defs.
* Assumes local variable fi exists. */
#define msc_ho_fsm_state_chg(msc_a, state) \
osmo_tdef_fsm_inst_state_chg((msc_a)->ho.fi, state, msc_ho_fsm_timeouts, (msc_a)->c.ran->tdefs, 5)
static __attribute__((constructor)) void msc_ho_fsm_init()
{
OSMO_ASSERT(osmo_fsm_register(&msc_ho_fsm) == 0);
}
void msc_ho_down_required_reject(struct msc_a *msc_a, enum gsm0808_cause cause)
{
struct msc_i *msc_i;
uint32_t event;
msc_i = msc_a_msc_i(msc_a);
OSMO_ASSERT(msc_i);
struct ran_msg ran_enc_msg = {
.msg_type = RAN_MSG_HANDOVER_REQUIRED_REJECT,
.handover_required_reject = {
.cause = cause,
},
};
if (msc_i->c.remote_to)
event = MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_ERROR;
else
event = MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST;
msc_a_msg_down(msc_a, MSC_ROLE_I, event, &ran_enc_msg);
}
/* Even though this is using the 3GPP TS 48.008 definitions and naming, the intention is to be RAN implementation agnostic.
* For other RAN types, the 48.008 items shall be translated to their respective counterparts. */
void msc_ho_start(struct msc_a *msc_a, const struct ran_handover_required *ho_req)
{
if (msc_a->ho.fi) {
LOG_HO(msc_a, LOGL_ERROR, "Rx Handover Required, but Handover is still ongoing\n");
msc_ho_down_required_reject(msc_a, GSM0808_CAUSE_PROTOCOL_ERROR_BETWEEN_BSS_AND_MSC);
return;
}
if (!ho_req->cil.id_list_len) {
LOG_HO(msc_a, LOGL_ERROR, "Rx Handover Required without a Cell Identifier List\n");
msc_ho_down_required_reject(msc_a, GSM0808_CAUSE_INFORMATION_ELEMENT_OR_FIELD_MISSING);
return;
}
if (msc_a_msc_t(msc_a)) {
LOG_HO(msc_a, LOGL_ERROR,
"Rx Handover Required, but this subscriber still has an active MSC-T role: %s\n",
msc_a_msc_t(msc_a)->c.fi->id);
/* Protocol error because the BSS is not supposed to send another Handover Required before the previous
* attempt has concluded. */
msc_ho_down_required_reject(msc_a, GSM0808_CAUSE_PROTOCOL_ERROR_BETWEEN_BSS_AND_MSC);
return;
}
/* Paranoia: make sure we start with clean state */
msc_a->ho = (struct msc_ho_state){};
msc_a->ho.fi = osmo_fsm_inst_alloc_child(&msc_ho_fsm, msc_a->c.fi, MSC_A_EV_HANDOVER_END);
OSMO_ASSERT(msc_a->ho.fi);
msc_a->ho.fi->priv = msc_a;
msc_a->ho.info = *ho_req;
msc_a->ho.next_cil_idx = 0;
/* Start the timeout */
msc_ho_fsm_state_chg(msc_a, MSC_HO_ST_REQUIRED);
}
static void msc_ho_rtp_rollback_to_old_cell(struct msc_a *msc_a);
static void msc_ho_end(struct msc_a *msc_a, bool success, enum gsm0808_cause cause)
{
struct msc_i *msc_i;
struct msc_t *msc_t = msc_a_msc_t(msc_a);
if (!success) {
msc_ho_rtp_rollback_to_old_cell(msc_a);
msc_ho_down_required_reject(msc_a, cause);
}
if (success) {
/* Any previous call forwarding to a remote MSC becomes obsolete. */
if (msc_a->cc.mncc_forwarding_to_remote_ran) {
mncc_call_release(msc_a->cc.mncc_forwarding_to_remote_ran);
msc_a->cc.mncc_forwarding_to_remote_ran = NULL;
}
/* Replace MSC-I with new MSC-T */
if (msc_t->c.remote_to) {
/* Inter-MSC Handover. */
/* The MNCC forwarding set up for inter-MSC handover, so far transitional in msc_a->ho now
* becomes the "officially" active MNCC forwarding for this call. */
msc_a->cc.mncc_forwarding_to_remote_ran = msc_a->ho.new_cell.mncc_forwarding_to_remote_ran;
msc_a->ho.new_cell.mncc_forwarding_to_remote_ran = NULL;
mncc_call_reparent(msc_a->cc.mncc_forwarding_to_remote_ran,
msc_a->c.fi, -1, MSC_MNCC_EV_CALL_ENDED, NULL, NULL);
/* inter-MSC link. msc_i_remote_alloc() properly "steals" the e_link from msc_t. */
msc_i = msc_i_remote_alloc(msc_a->c.msub, msc_t->c.ran, msc_t->c.remote_to);
OSMO_ASSERT(msc_t->c.remote_to == NULL);
} else {
/* local BSS */
msc_i = msc_i_alloc(msc_a->c.msub, msc_t->c.ran);
/* msc_i_set_ran_conn() properly "steals" the ran_conn from msc_t */
msc_i_set_ran_conn(msc_i, msc_t->ran_conn);
}
}
osmo_fsm_inst_term(msc_a->ho.fi, OSMO_FSM_TERM_REGULAR, NULL);
}
#define msc_ho_failed(msc_a, cause, fmt, args...) do { \
LOG_HO(msc_a, LOGL_ERROR, fmt, ##args); \
msc_ho_end(msc_a, false, cause); \
} while(0)
#define msc_ho_try_next_cell(msc_a, fmt, args...) do {\
LOG_HO(msc_a, LOGL_ERROR, fmt, ##args); \
msc_ho_fsm_state_chg(msc_a, MSC_HO_ST_REQUIRED); \
} while(0)
#define msc_ho_success(msc_a) msc_ho_end(msc_a, true, 0)
enum msc_neighbor_type msc_ho_find_target_cell(struct msc_a *msc_a, const struct gsm0808_cell_id *cid,
const struct neighbor_ident_entry **remote_msc,
struct ran_peer **ran_peer_from_neighbor_ident,
struct ran_peer **ran_peer_from_seen_cells)
{
struct gsm_network *net = msc_a_net(msc_a);
const struct neighbor_ident_entry *e;
struct sccp_ran_inst *sri;
struct ran_peer *rp_from_neighbor_ident = NULL;
struct ran_peer *rp_from_cell_id = NULL;
struct ran_peer *rp;
int i;
OSMO_ASSERT(remote_msc);
OSMO_ASSERT(ran_peer_from_neighbor_ident);
OSMO_ASSERT(ran_peer_from_seen_cells);
e = neighbor_ident_find_by_cell(&net->neighbor_ident_list, msc_a->c.ran->type, cid);
if (e && e->addr.type == MSC_NEIGHBOR_TYPE_REMOTE_MSC) {
*remote_msc = e;
return MSC_NEIGHBOR_TYPE_REMOTE_MSC;
}
/* It is not a remote MSC target. Figure out local RAN peers. */
if (e && e->addr.type == MSC_NEIGHBOR_TYPE_LOCAL_RAN_PEER) {
/* Find local RAN peer in neighbor config. If anything is wrong with that, just keep
* rp_from_neighbor_ident == NULL. */
struct sccp_ran_inst *sri_from_neighbor_ident = NULL;
struct osmo_ss7_instance *ss7 = NULL;
/* Get the sccp_ran_inst with sanity checkin. If anything is fishy, just keep
* sri_from_neighbor_ident == NULL and below code will notice the error. */
if (e->addr.ran_type < msc_ran_infra_len) {
sri_from_neighbor_ident = msc_ran_infra[e->addr.ran_type].sri;
ss7 = osmo_sccp_get_ss7(sri_from_neighbor_ident->sccp);
if (!ss7)
sri_from_neighbor_ident = NULL;
}
if (!sri_from_neighbor_ident) {
LOG_HO(msc_a, LOGL_ERROR, "Cannot handover to RAN type %s\n", osmo_rat_type_name(e->addr.ran_type));
} else {
/* Interpret the point-code string placed in the neighbors config. */
int pc = osmo_ss7_pointcode_parse(ss7, e->addr.local_ran_peer_pc_str);
if (pc < 0) {
LOG_HO(msc_a, LOGL_ERROR, "Invalid point code string: %s\n",
osmo_quote_str(e->addr.local_ran_peer_pc_str, -1));
} else {
struct osmo_sccp_addr addr = {};
osmo_sccp_make_addr_pc_ssn(&addr, pc, sri_from_neighbor_ident->ran->ssn);
rp_from_neighbor_ident = ran_peer_find_by_addr(sri_from_neighbor_ident, &addr);
}
}
if (!rp_from_neighbor_ident) {
LOG_HO(msc_a, LOGL_ERROR, "Target RAN peer from neighbor config is not connected:"
" Cell ID %s resolves to target address %s\n",
gsm0808_cell_id_name(cid), e->addr.local_ran_peer_pc_str);
} else if (rp_from_neighbor_ident->fi->state != RAN_PEER_ST_READY) {
LOG_HO(msc_a, LOGL_ERROR, "Target RAN peer in invalid state: %s (%s)\n",
osmo_fsm_inst_state_name(rp_from_neighbor_ident->fi),
rp_from_neighbor_ident->fi->id);
rp_from_neighbor_ident = NULL;
}
}
/* Figure out actually connected RAN peers for this cell ID.
* If no cell has been found yet at all, this might determine a Handover target,
* otherwise this is for sanity checking. If none is found, just keep rp_from_cell_id == NULL. */
/* Iterate all connected RAN peers. Possibly, more than one RAN peer has advertised a match for this Cell ID.
* For example, if the handover target is identified as LAC=23 but there are multiple cells with distinct CIs
* serving in LAC=23, we have an ambiguity. It's up to the user to configure correctly, help with logging. */
for (i = 0; i < msc_ran_infra_len; i++) {
sri = msc_ran_infra[i].sri;
if (!sri)
continue;
rp = ran_peer_find_by_cell_id(sri, cid, true);
if (rp && rp->fi && rp->fi->state == RAN_PEER_ST_READY) {
if (rp_from_cell_id) {
LOG_HO(msc_a, LOGL_ERROR,
"Ambiguous match for cell ID %s: more than one RAN type is serving this cell"
" ID: %s and %s\n",
gsm0808_cell_id_name(cid),
rp_from_cell_id->fi->id,
rp->fi->id);
/* But logging is all we're going to do about it. */
}
/* Use the first found RAN peer, but if multiple matches are found, favor the one that matches
* the current RAN type. */
if (!rp_from_cell_id || rp->sri == msc_a->c.ran->sri)
rp_from_cell_id = rp;
}
}
/* Did we find mismatching targets from neighbor config and from connected cells? */
if (rp_from_neighbor_ident && rp_from_cell_id
&& rp_from_neighbor_ident != rp_from_cell_id) {
LOG_HO(msc_a, LOGL_ERROR, "Ambiguous match for cell ID %s:"
" neighbor config points at %s; a matching cell is also served by connected RAN peer %s\n",
gsm0808_cell_id_name(cid), rp_from_neighbor_ident->fi->id, rp_from_cell_id->fi->id);
/* But logging is all we're going to do about it. */
}
if (rp_from_neighbor_ident && rp_from_neighbor_ident->sri != msc_a->c.ran->sri) {
LOG_HO(msc_a, LOGL_ERROR,
"Neighbor config indicates inter-RAT Handover, which is not implemented. Ignoring target %s\n",
rp_from_neighbor_ident->fi->id);
rp_from_neighbor_ident = NULL;
}
if (rp_from_cell_id && rp_from_cell_id->sri != msc_a->c.ran->sri) {
LOG_HO(msc_a, LOGL_ERROR,
"Target RAN peer indicates inter-RAT Handover, which is not implemented. Ignoring target %s\n",
rp_from_cell_id->fi->id);
rp_from_cell_id = NULL;
}
*ran_peer_from_neighbor_ident = rp_from_neighbor_ident;
*ran_peer_from_seen_cells = rp_from_cell_id;
return rp_from_neighbor_ident || rp_from_cell_id ? MSC_NEIGHBOR_TYPE_LOCAL_RAN_PEER : MSC_NEIGHBOR_TYPE_NONE;
}
static bool msc_ho_find_next_target_cell(struct msc_a *msc_a)
{
struct vlr_subscr *vsub = msc_a_vsub(msc_a);
struct ran_handover_required *info = &msc_a->ho.info;
struct gsm0808_cell_id *cid = &msc_a->ho.new_cell.cid;
const struct neighbor_ident_entry *e;
struct ran_peer *rp_from_neighbor_ident = NULL;
struct ran_peer *rp_from_cell_id = NULL;
struct ran_peer *rp;
unsigned int cil_idx = msc_a->ho.next_cil_idx;
msc_a->ho.next_cil_idx++;
msc_a->ho.new_cell.type = MSC_NEIGHBOR_TYPE_NONE;
if (cil_idx >= info->cil.id_list_len)
return false;
*cid = (struct gsm0808_cell_id){
.id_discr = info->cil.id_discr,
.id = info->cil.id_list[cil_idx],
};
msc_a->ho.new_cell.cgi = (struct osmo_cell_global_id){
.lai = vsub->cgi.lai,
};
gsm0808_cell_id_to_cgi(&msc_a->ho.new_cell.cgi, cid);
switch (msc_ho_find_target_cell(msc_a, cid, &e, &rp_from_neighbor_ident, &rp_from_cell_id)) {
case MSC_NEIGHBOR_TYPE_REMOTE_MSC:
OSMO_ASSERT(e);
msc_a->ho.new_cell.ran_type = e->addr.ran_type;
msc_a->ho.new_cell.type = MSC_NEIGHBOR_TYPE_REMOTE_MSC;
msc_a->ho.new_cell.msc_ipa_name = e->addr.remote_msc_ipa_name.buf;
return true;
case MSC_NEIGHBOR_TYPE_LOCAL_RAN_PEER:
rp = rp_from_neighbor_ident ? : rp_from_cell_id;
OSMO_ASSERT(rp);
msc_a->ho.new_cell.type = MSC_NEIGHBOR_TYPE_LOCAL_RAN_PEER;
msc_a->ho.new_cell.ran_peer = rp;
return true;
default:
break;
}
LOG_HO(msc_a, LOGL_DEBUG, "Cannot find target peer for cell ID %s\n", gsm0808_cell_id_name(cid));
/* Try the next cell id, if any. */
return msc_ho_find_next_target_cell(msc_a);
}
static void msc_ho_fsm_required_onenter(struct osmo_fsm_inst *fi, uint32_t prev_state)
{
struct msc_a *msc_a = fi->priv;
if (!msc_ho_find_next_target_cell(msc_a)) {
int tried = msc_a->ho.next_cil_idx - 1;
msc_ho_failed(msc_a, GSM0808_CAUSE_NO_RADIO_RESOURCE_AVAILABLE,
"Attempted Handover to %u cells without success\n", tried);
return;
}
msc_ho_fsm_state_chg(msc_a, MSC_HO_ST_WAIT_REQUEST_ACK);
}
static void msc_ho_send_handover_request(struct msc_a *msc_a)
{
struct vlr_subscr *vsub = msc_a_vsub(msc_a);
struct gsm_network *net = msc_a_net(msc_a);
struct gsm0808_channel_type channel_type;
struct gsm_trans *cc_trans = msc_a->cc.active_trans;
struct ran_msg ran_enc_msg = {
.msg_type = RAN_MSG_HANDOVER_REQUEST,
.handover_request = {
.imsi = vsub->imsi,
.classmark = &vsub->classmark,
.geran = {
.chosen_encryption = &msc_a->geran_encr,
.a5_encryption_mask = net->a5_encryption_mask,
},
.bssap_cause = GSM0808_CAUSE_BETTER_CELL,
.current_channel_type_1_present = msc_a->ho.info.current_channel_type_1_present,
.current_channel_type_1 = msc_a->ho.info.current_channel_type_1,
.speech_version_used = msc_a->ho.info.speech_version_used,
.old_bss_to_new_bss_info_raw = msc_a->ho.info.old_bss_to_new_bss_info_raw,
.old_bss_to_new_bss_info_raw_len = msc_a->ho.info.old_bss_to_new_bss_info_raw_len,
/* Don't send AoIP Transport Layer Address for inter-MSC Handover */
.rtp_ran_local = (msc_a->ho.new_cell.type == MSC_NEIGHBOR_TYPE_LOCAL_RAN_PEER)
? call_leg_local_ip(msc_a->cc.call_leg, RTP_TO_RAN) : NULL,
.call_id_present = true,
.call_id = cc_trans->callref,
},
};
if (msc_a->geran_encr.key_len)
LOG_MSC_A(msc_a, LOGL_DEBUG, "HO Request with ciphering: A5/%d kc %s kc128 %s\n",
msc_a->geran_encr.alg_id - 1,
osmo_hexdump_nospc_c(OTC_SELECT, msc_a->geran_encr.key, msc_a->geran_encr.key_len),
msc_a->geran_encr.kc128_present ?
osmo_hexdump_nospc_c(OTC_SELECT, msc_a->geran_encr.kc128, sizeof(msc_a->geran_encr.kc128))
: "-");
if (msc_a->cc.active_trans) {
if (mncc_bearer_cap_to_channel_type(&channel_type, &msc_a->cc.active_trans->bearer_cap)) {
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE,
"Failed to encode Bearer Cap to Channel Type\n");
return;
}
ran_enc_msg.handover_request.geran.channel_type = &channel_type;
}
gsm0808_cell_id_from_cgi(&ran_enc_msg.handover_request.cell_id_serving, CELL_IDENT_WHOLE_GLOBAL, &vsub->cgi);
ran_enc_msg.handover_request.cell_id_target = msc_a->ho.new_cell.cid;
if (msc_a_msg_down(msc_a, MSC_ROLE_T, MSC_T_EV_FROM_A_PREPARE_HANDOVER_REQUEST, &ran_enc_msg))
msc_ho_try_next_cell(msc_a, "Failed to send Handover Request message\n");
}
static void msc_ho_fsm_wait_request_ack_onenter(struct osmo_fsm_inst *fi, uint32_t prev_state)
{
struct msc_a *msc_a = fi->priv;
struct msc_i *msc_i = msc_a_msc_i(msc_a);
struct msc_t *msc_t;
struct ran_peer *rp;
const char *ipa_name;
msc_t = msc_a_msc_t(msc_a);
if (msc_t) {
/* All the other code should prevent this from happening, ever. */
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE,
"Cannot initiate Handover Request, there still is an active MSC-T role: %s\n",
msc_t->c.fi->id);
return;
}
if (!msc_i) {
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE,
"Cannot initiate Handover Request, there is no MSC-I role\n");
return;
}
if (!msc_i->c.remote_to
&& !(msc_i->ran_conn && msc_i->ran_conn->ran_peer)) {
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE,
"Cannot initiate Handover Request, MSC-I role has no connection\n");
return;
}
switch (msc_a->ho.new_cell.type) {
case MSC_NEIGHBOR_TYPE_LOCAL_RAN_PEER:
rp = msc_a->ho.new_cell.ran_peer;
OSMO_ASSERT(rp && rp->fi);
if (msc_i->c.remote_to) {
LOG_HO(msc_a, LOGL_INFO,
"Starting inter-MSC Subsequent Handover from remote MSC %s to local %s\n",
msc_i->c.remote_to->remote_name, rp->fi->id);
msc_a->ho.subsequent_ho = true;
} else {
LOG_HO(msc_a, LOGL_INFO, "Starting inter-BSC Handover from %s to %s\n",
msc_i->ran_conn->ran_peer->fi->id, rp->fi->id);
}
msc_t = msc_t_alloc(msc_a->c.msub, rp);
break;
case MSC_NEIGHBOR_TYPE_REMOTE_MSC:
ipa_name = msc_a->ho.new_cell.msc_ipa_name;
OSMO_ASSERT(ipa_name);
if (msc_i->c.remote_to) {
LOG_HO(msc_a, LOGL_INFO,
"Starting inter-MSC Subsequent Handover from remote MSC %s to remote MSC at %s\n",
msc_i->c.remote_to->remote_name, osmo_quote_str(ipa_name, -1));
msc_a->ho.subsequent_ho = true;
} else {
LOG_HO(msc_a, LOGL_INFO, "Starting inter-MSC Handover from local %s to remote MSC at %s\n",
msc_i->ran_conn->ran_peer->fi->id,
osmo_quote_str(ipa_name, -1));
}
msc_t = msc_t_remote_alloc(msc_a->c.msub, msc_a->c.ran,
(const uint8_t *) ipa_name,
strlen(ipa_name));
break;
default:
msc_ho_try_next_cell(msc_a, "unknown Handover target type %d\n", msc_a->ho.new_cell.type);
return;
}
if (!msc_t) {
/* There should definitely be one now. */
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE,
"Cannot initiate Handover Request, failed to set up a target MSC-T\n");
return;
}
msc_ho_send_handover_request(msc_a);
}
static void msc_ho_rx_request_ack(struct msc_a *msc_a, struct msc_a_ran_dec_data *hra);
static void msc_ho_fsm_wait_request_ack(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct msc_a *msc_a = fi->priv;
switch (event) {
case MSC_HO_EV_RX_REQUEST_ACK:
msc_ho_rx_request_ack(msc_a, (struct msc_a_ran_dec_data*)data);
return;
case MSC_HO_EV_RX_FAILURE:
msc_ho_failed(msc_a, GSM0808_CAUSE_NO_RADIO_RESOURCE_AVAILABLE,
"Received Handover Failure message\n");
return;
default:
OSMO_ASSERT(false);
}
}
static void msc_ho_rtp_switch_to_new_cell(struct msc_a *msc_a);
void msc_ho_mncc_forward_cb(struct mncc_call *mncc_call, const union mncc_msg *mncc_msg, void *data)
{
struct msc_a *msc_a = data;
switch (mncc_msg->msg_type) {
case MNCC_RTP_CONNECT:
msc_a->ho.rtp_switched_to_new_cell = true;
return;
default:
return;
}
}
/* Initiate call forwarding via MNCC: call the Handover Number that the other MSC assigned. */
static int msc_ho_start_inter_msc_call_forwarding(struct msc_a *msc_a, struct msc_t *msc_t,
const struct msc_a_ran_dec_data *hra)
{
const struct osmo_gsup_message *e_info = hra->an_apdu->e_info;
struct gsm_mncc outgoing_call_req = {};
struct call_leg *cl = msc_a->cc.call_leg;
struct rtp_stream *rtp_to_ran = cl ? cl->rtp[RTP_TO_RAN] : NULL;
struct mncc_call *mncc_call;
if (!e_info || !e_info->msisdn_enc || !e_info->msisdn_enc_len) {
msc_ho_try_next_cell(msc_a,
"No Handover Number in Handover Request Acknowledge from remote MSC\n");
return -EINVAL;
}
if (!rtp_to_ran) {
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE, "Unexpected: no RTP stream is set up\n");
return -EINVAL;
}
/* Backup old cell's RTP IP:port and codec data */
msc_a->ho.old_cell.ran_remote_rtp = rtp_to_ran->remote;
msc_a->ho.old_cell.codec = rtp_to_ran->codec;
/* Blindly taken over from an MNCC trace of existing code: send an all-zero CCCAP: */
outgoing_call_req.fields |= MNCC_F_CCCAP;
/* Called number */
outgoing_call_req.fields |= MNCC_F_CALLED;
outgoing_call_req.called.plan = 1; /* Empirical magic number. There seem to be no enum or defines for this.
* The only other place setting this apparently is gsm48_decode_called(). */
if (gsm48_decode_bcd_number2(outgoing_call_req.called.number, sizeof(outgoing_call_req.called.number),
e_info->msisdn_enc, e_info->msisdn_enc_len, 0)) {
msc_ho_try_next_cell(msc_a,
"Failed to decode Handover Number in Handover Request Acknowledge"
" from remote MSC\n");
return -EINVAL;
}
if (msc_a->cc.active_trans) {
outgoing_call_req.fields |= MNCC_F_BEARER_CAP;
outgoing_call_req.bearer_cap = msc_a->cc.active_trans->bearer_cap;
}
mncc_call = mncc_call_alloc(msc_a_vsub(msc_a),
msc_a->ho.fi,
MSC_HO_EV_MNCC_FORWARDING_COMPLETE,
MSC_HO_EV_MNCC_FORWARDING_FAILED,
msc_ho_mncc_forward_cb, msc_a);
mncc_call_set_rtp_stream(mncc_call, rtp_to_ran);
msc_a->ho.new_cell.mncc_forwarding_to_remote_ran = mncc_call;
return mncc_call_outgoing_start(mncc_call, &outgoing_call_req);
}
static void msc_ho_rx_request_ack(struct msc_a *msc_a, struct msc_a_ran_dec_data *hra)
{
struct msc_t *msc_t = msc_a_msc_t(msc_a);
struct ran_msg ran_enc_msg;
OSMO_ASSERT(hra->ran_dec);
OSMO_ASSERT(hra->an_apdu);
if (!msc_t) {
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE, "MSC-T role missing\n");
return;
}
if (!hra->ran_dec->handover_request_ack.rr_ho_command
|| !hra->ran_dec->handover_request_ack.rr_ho_command_len) {
msc_ho_try_next_cell(msc_a, "Missing mandatory IE in Handover Request Acknowledge:"
" L3 Info (RR Handover Command)\n");
return;
}
if (!hra->ran_dec->handover_request_ack.chosen_channel_present) {
LOG_HO(msc_a, LOGL_DEBUG, "No 'Chosen Channel' IE in Handover Request Ack\n");
msc_t->geran.chosen_channel = 0;
} else
msc_t->geran.chosen_channel = hra->ran_dec->handover_request_ack.chosen_channel;
if (!hra->ran_dec->handover_request_ack.chosen_encr_alg) {
LOG_HO(msc_a, LOGL_DEBUG, "No 'Chosen Encryption Algorithm' IE in Handover Request Ack\n");
msc_t->geran.chosen_encr_alg = 0;
} else {
msc_t->geran.chosen_encr_alg = hra->ran_dec->handover_request_ack.chosen_encr_alg;
if (msc_t->geran.chosen_encr_alg < 1 || msc_t->geran.chosen_encr_alg > 8) {
msc_ho_try_next_cell(msc_a, "Handover Request Ack: Invalid 'Chosen Encryption Algorithm': %u\n",
msc_t->geran.chosen_encr_alg);
return;
}
}
msc_t->geran.chosen_speech_version = hra->ran_dec->handover_request_ack.chosen_speech_version;
if (!msc_t->geran.chosen_speech_version)
LOG_HO(msc_a, LOGL_DEBUG, "No 'Chosen Speech Version' IE in Handover Request Ack\n");
/* Inter-MSC call forwarding? */
if (msc_a->ho.new_cell.type == MSC_NEIGHBOR_TYPE_REMOTE_MSC) {
if (msc_ho_start_inter_msc_call_forwarding(msc_a, msc_t, hra))
return;
}
msc_ho_fsm_state_chg(msc_a, MSC_HO_ST_WAIT_COMPLETE);
/* Forward the RR Handover Command composed by the new RAN peer down to the old RAN peer */
ran_enc_msg = (struct ran_msg){
.msg_type = RAN_MSG_HANDOVER_COMMAND,
.handover_command = {
.rr_ho_command = hra->ran_dec->handover_request_ack.rr_ho_command,
.rr_ho_command_len = hra->ran_dec->handover_request_ack.rr_ho_command_len,
},
};
if (msc_a_msg_down(msc_a, MSC_ROLE_I,
msc_a->ho.subsequent_ho ? MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_RESULT
: MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST,
&ran_enc_msg)) {
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE, "Failed to send Handover Command\n");
return;
}
msc_a->ho.new_cell.ran_remote_rtp = hra->ran_dec->handover_request_ack.remote_rtp;
if (osmo_sockaddr_str_is_nonzero(&msc_a->ho.new_cell.ran_remote_rtp)) {
LOG_HO(msc_a, LOGL_DEBUG, "Request Ack contains cell's RTP address " OSMO_SOCKADDR_STR_FMT "\n",
OSMO_SOCKADDR_STR_FMT_ARGS(&msc_a->ho.new_cell.ran_remote_rtp));
}
msc_a->ho.new_cell.codec_present = hra->ran_dec->handover_request_ack.codec_present;
msc_a->ho.new_cell.codec = hra->ran_dec->handover_request_ack.codec;
if (hra->ran_dec->handover_request_ack.codec_present) {
LOG_HO(msc_a, LOGL_DEBUG, "Request Ack contains codec %s\n",
osmo_mgcpc_codec_name(msc_a->ho.new_cell.codec));
}
}
static void msc_ho_rtp_switch_to_new_cell(struct msc_a *msc_a)
{
struct call_leg *cl = msc_a->cc.call_leg;
struct rtp_stream *rtp_to_ran = cl ? cl->rtp[RTP_TO_RAN] : NULL;
if (!rtp_to_ran) {
LOG_HO(msc_a, LOGL_DEBUG, "No RTP stream, nothing to switch\n");
return;
}
if (!osmo_sockaddr_str_is_nonzero(&msc_a->ho.new_cell.ran_remote_rtp)) {
LOG_HO(msc_a, LOGL_DEBUG, "New cell's RTP IP:port not yet known, not switching RTP stream\n");
return;
}
if (msc_a->ho.rtp_switched_to_new_cell) {
LOG_HO(msc_a, LOGL_DEBUG, "Already switched RTP to new cell\n");
return;
}
msc_a->ho.rtp_switched_to_new_cell = true;
/* Backup old cell's RTP IP:port and codec data */
msc_a->ho.old_cell.ran_remote_rtp = rtp_to_ran->remote;
msc_a->ho.old_cell.codec = rtp_to_ran->codec;
LOG_HO(msc_a, LOGL_DEBUG, "Switching RTP stream to new cell: from " OSMO_SOCKADDR_STR_FMT " to " OSMO_SOCKADDR_STR_FMT "\n",
OSMO_SOCKADDR_STR_FMT_ARGS(&msc_a->ho.old_cell.ran_remote_rtp),
OSMO_SOCKADDR_STR_FMT_ARGS(&msc_a->ho.new_cell.ran_remote_rtp));
/* If a previous forwarding to a remote MSC is still active, this now becomes no longer responsible for the RTP
* stream. */
if (msc_a->cc.mncc_forwarding_to_remote_ran) {
if (msc_a->cc.mncc_forwarding_to_remote_ran->rtps != rtp_to_ran) {
LOG_HO(msc_a, LOGL_ERROR,
"Unexpected state: previous MNCC forwarding not using RTP-to-RAN stream\n");
/* That would be weird, but carry on anyway... */
}
mncc_call_detach_rtp_stream(msc_a->cc.mncc_forwarding_to_remote_ran);
}
/* Switch over to the new peer */
rtp_stream_set_remote_addr(rtp_to_ran, &msc_a->ho.new_cell.ran_remote_rtp);
if (msc_a->ho.new_cell.codec_present)
rtp_stream_set_codec(rtp_to_ran, msc_a->ho.new_cell.codec);
else
LOG_HO(msc_a, LOGL_ERROR, "No codec is set\n");
rtp_stream_commit(rtp_to_ran);
}
static void msc_ho_rtp_rollback_to_old_cell(struct msc_a *msc_a)
{
struct call_leg *cl = msc_a->cc.call_leg;
struct rtp_stream *rtp_to_ran = cl ? cl->rtp[RTP_TO_RAN] : NULL;
if (!msc_a->ho.rtp_switched_to_new_cell) {
LOG_HO(msc_a, LOGL_DEBUG, "Not switched RTP to new cell yet, no need to roll back\n");
return;
}
if (!rtp_to_ran) {
LOG_HO(msc_a, LOGL_DEBUG, "No RTP stream, nothing to switch\n");
return;
}
if (!osmo_sockaddr_str_is_nonzero(&msc_a->ho.old_cell.ran_remote_rtp)) {
LOG_HO(msc_a, LOGL_DEBUG, "Have no RTP IP:port for the old cell, not switching back to\n");
return;
}
/* The new call forwarding to a remote MSC is no longer needed because the handover failed */
if (msc_a->ho.new_cell.mncc_forwarding_to_remote_ran)
mncc_call_detach_rtp_stream(msc_a->ho.new_cell.mncc_forwarding_to_remote_ran);
/* If before this handover, there was a call forwarding to a remote MSC in place, this now goes back into
* responsibility. */
if (msc_a->cc.mncc_forwarding_to_remote_ran)
mncc_call_set_rtp_stream(msc_a->cc.mncc_forwarding_to_remote_ran, rtp_to_ran);
msc_a->ho.rtp_switched_to_new_cell = false;
msc_a->ho.ready_to_switch_rtp = false;
LOG_HO(msc_a, LOGL_NOTICE, "Switching RTP back to old cell\n");
/* Switch back to the old cell */
rtp_stream_set_remote_addr(rtp_to_ran, &msc_a->ho.old_cell.ran_remote_rtp);
rtp_stream_set_codec(rtp_to_ran, msc_a->ho.old_cell.codec);
rtp_stream_commit(rtp_to_ran);
}
static void msc_ho_send_handover_succeeded(struct msc_a *msc_a)
{
struct ran_msg ran_enc_msg = {
.msg_type = RAN_MSG_HANDOVER_SUCCEEDED,
};
if (msc_a_msg_down(msc_a, MSC_ROLE_I, MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST, &ran_enc_msg))
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE, "Failed to send Handover Succeeded message\n");
}
static void msc_ho_fsm_wait_complete(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct msc_a *msc_a = fi->priv;
switch (event) {
case MSC_HO_EV_RX_DETECT:
msc_a->ho.ready_to_switch_rtp = true;
/* For inter-MSC, the mncc_fsm switches the rtp_stream upon MNCC_RTP_CONNECT.
* For inter-BSC, need to switch here to the address obtained from Handover Request Ack. */
if (msc_a->ho.new_cell.type == MSC_NEIGHBOR_TYPE_LOCAL_RAN_PEER)
msc_ho_rtp_switch_to_new_cell(msc_a);
msc_ho_send_handover_succeeded(msc_a);
return;
case MSC_HO_EV_RX_COMPLETE:
msc_ho_success(msc_a);
return;
case MSC_HO_EV_RX_FAILURE:
msc_ho_failed(msc_a, GSM0808_CAUSE_NO_RADIO_RESOURCE_AVAILABLE,
"Received Handover Failure message\n");
return;
case MSC_HO_EV_MNCC_FORWARDING_FAILED:
msc_ho_failed(msc_a, GSM0808_CAUSE_EQUIPMENT_FAILURE, "MNCC Forwarding failed\n");
return;
case MSC_HO_EV_MNCC_FORWARDING_COMPLETE:
return;
default:
OSMO_ASSERT(false);
}
}
static void msc_ho_fsm_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause cause)
{
struct msc_a *msc_a = fi->priv;
struct msc_t *msc_t = msc_a_msc_t(msc_a);
/* paranoia */
if (msc_a->ho.fi != fi)
return;
/* Completely clear all handover state */
msc_a->ho = (struct msc_ho_state){};
if (msc_t)
msc_t_clear(msc_t);
}
static int msc_ho_fsm_timer_cb(struct osmo_fsm_inst *fi)
{
return 1;
}
#define S(x) (1 << (x))
static const struct osmo_fsm_state msc_ho_fsm_states[] = {
[MSC_HO_ST_REQUIRED] = {
.name = OSMO_STRINGIFY(MSC_HO_ST_REQUIRED),
.out_state_mask = 0
| S(MSC_HO_ST_REQUIRED)
| S(MSC_HO_ST_WAIT_REQUEST_ACK)
,
.onenter = msc_ho_fsm_required_onenter,
},
[MSC_HO_ST_WAIT_REQUEST_ACK] = {
.name = OSMO_STRINGIFY(MSC_HO_ST_WAIT_REQUEST_ACK),
.in_event_mask = 0
| S(MSC_HO_EV_RX_REQUEST_ACK)
| S(MSC_HO_EV_RX_FAILURE)
,
.out_state_mask = 0
| S(MSC_HO_ST_REQUIRED)
| S(MSC_HO_ST_WAIT_COMPLETE)
,
.onenter = msc_ho_fsm_wait_request_ack_onenter,
.action = msc_ho_fsm_wait_request_ack,
},
[MSC_HO_ST_WAIT_COMPLETE] = {
.name = OSMO_STRINGIFY(MSC_HO_ST_WAIT_COMPLETE),
.in_event_mask = 0
| S(MSC_HO_EV_RX_DETECT)
| S(MSC_HO_EV_RX_COMPLETE)
| S(MSC_HO_EV_RX_FAILURE)
| S(MSC_HO_EV_MNCC_FORWARDING_COMPLETE)
| S(MSC_HO_EV_MNCC_FORWARDING_FAILED)
,
.action = msc_ho_fsm_wait_complete,
},
};
static const struct value_string msc_ho_fsm_event_names[] = {
OSMO_VALUE_STRING(MSC_HO_EV_RX_REQUEST_ACK),
OSMO_VALUE_STRING(MSC_HO_EV_RX_DETECT),
OSMO_VALUE_STRING(MSC_HO_EV_RX_COMPLETE),
OSMO_VALUE_STRING(MSC_HO_EV_RX_FAILURE),
{}
};
struct osmo_fsm msc_ho_fsm = {
.name = "handover",
.states = msc_ho_fsm_states,
.num_states = ARRAY_SIZE(msc_ho_fsm_states),
.log_subsys = DHO,
.event_names = msc_ho_fsm_event_names,
.timer_cb = msc_ho_fsm_timer_cb,
.cleanup = msc_ho_fsm_cleanup,
};
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