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assignment_fsm: allow assignment to a specific lchan 

So far the assignment FSM always tried to satisfy the channel mode and
rate by either re-using the current lchan or finding a new, unused
lchan. For VAMOS however, we want to pick one specific lchan.

Add target_lchan to struct assignment_request and skip all mode matching
and lchan selection when a specific target_lchan is set.

Related: SYS#5315 OS#4940
Change-Id: I71e0d4ff4746706e0be5266e4574d70ca432e3d7
This commit is contained in:
Neels Hofmeyr 2021-04-27 22:37:14 +00:00
parent c2d3fe5da0
commit cb0aaad5d4
3 changed files with 97 additions and 19 deletions
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4
include/osmocom/bsc/assignment_fsm.h
View File

@ -41,6 +41,10 @@ enum assignment_fsm_event {
void assignment_fsm_init();
int reassignment_request_to_lchan(enum assign_for assign_for, struct gsm_lchan *lchan, struct gsm_lchan *to_lchan);
int reassignment_request_to_chan_type(enum assign_for assign_for, struct gsm_lchan *lchan,
enum gsm_chan_t new_lchan_type);
void assignment_fsm_start(struct gsm_subscriber_connection *conn, struct gsm_bts *bts,
struct assignment_request *req);
void assignment_reset(struct gsm_subscriber_connection *conn);

8
include/osmocom/bsc/gsm_data.h
View File

@ -154,6 +154,14 @@ struct assignment_request {
/* Rate/codec setting in preference order (need at least 1 !) */
int n_ch_mode_rate;
struct channel_mode_and_rate ch_mode_rate_list[3];
/* An assignment request usually requests to assign any available lchan, to match above requirements. This may
* also choose to just keep the current lchan and merely modify it as appropriate. In these cases, keep
* target_lchan == NULL.
* In some situations, an assignment to a specific target lchan is requested (congestion resolution, VAMOS
* multiplexing, user request via VTY). In these situations, select a target lchan beforehand and point
* target_lchan to it. */
struct gsm_lchan *target_lchan;
};
/* State of an ongoing Assignment, while the assignment_fsm is still busy. This serves as state separation to keep the

104
src/osmo-bsc/assignment_fsm.c
View File

@ -438,6 +438,48 @@ static bool reuse_existing_lchan(struct gsm_subscriber_connection *conn)
return false;
}
static int _reassignment_request(enum assign_for assign_for, struct gsm_lchan *lchan, struct gsm_lchan *to_lchan,
enum gsm_chan_t new_lchan_type)
{
struct gsm_subscriber_connection *conn = lchan->conn;
struct assignment_request req = {
.assign_for = assign_for,
.aoip = gscon_is_aoip(conn),
.msc_assigned_cic = conn->user_plane.msc_assigned_cic,
.msc_rtp_port = conn->user_plane.msc_assigned_rtp_port,
.n_ch_mode_rate = 1,
.ch_mode_rate_list = { lchan->current_ch_mode_rate },
.target_lchan = to_lchan,
};
if (to_lchan)
new_lchan_type = to_lchan->type;
req.ch_mode_rate_list[0].chan_rate = chan_t_to_chan_rate(new_lchan_type);
/* lchan activation will automatically convert chan_mode to a VAMOS equivalent if required.
* So rather always pass the plain non-VAMOS mode. */
req.ch_mode_rate_list[0].chan_mode = gsm48_chan_mode_to_non_vamos(lchan->current_ch_mode_rate.chan_mode);
OSMO_STRLCPY_ARRAY(req.msc_rtp_addr, conn->user_plane.msc_assigned_rtp_addr);
if (conn->user_plane.mgw_endpoint_ci_msc) {
req.use_osmux = osmo_mgcpc_ep_ci_get_crcx_info_to_osmux_cid(conn->user_plane.mgw_endpoint_ci_msc,
&req.osmux_cid);
}
return osmo_fsm_inst_dispatch(conn->fi, GSCON_EV_ASSIGNMENT_START, &req);
}
int reassignment_request_to_lchan(enum assign_for assign_for, struct gsm_lchan *lchan, struct gsm_lchan *to_lchan)
{
return _reassignment_request(assign_for, lchan, to_lchan, 0);
}
int reassignment_request_to_chan_type(enum assign_for assign_for, struct gsm_lchan *lchan,
enum gsm_chan_t new_lchan_type)
{
return _reassignment_request(assign_for, lchan, NULL, new_lchan_type);
}
void assignment_fsm_start(struct gsm_subscriber_connection *conn, struct gsm_bts *bts,
struct assignment_request *req)
{
@ -470,13 +512,8 @@ void assignment_fsm_start(struct gsm_subscriber_connection *conn, struct gsm_bts
if (check_requires_voice_stream(conn) < 0)
return;
/* There may be an already existing lchan, if yes, try to work with
* the existing lchan.
* If an RTP FSM is already set up for the lchan, Mode Modify is not yet supported -- see handling of
* LCHAN_EV_REQUEST_MODE_MODIFY in lchan_fsm.c. To not break the lchan, do not even attempt to re-use an lchan
* that already has an RTP stream set up, rather establish a new lchan (that transition is well implemented). */
if (reuse_existing_lchan(conn) && !conn->lchan->fi_rtp) {
/* The new lchan is the old lchan, keep new_lchan == NULL. */
if (!req->target_lchan && reuse_existing_lchan(conn)) {
/* The already existing lchan is suitable for this mode */
conn->assignment.new_lchan = NULL;
/* If the requested mode and the current TCH mode matches up, just send the
@ -512,19 +549,48 @@ void assignment_fsm_start(struct gsm_subscriber_connection *conn, struct gsm_bts
return;
}
/* Try to allocate a new lchan in order of preference */
for (i = 0; i < req->n_ch_mode_rate; i++) {
conn->assignment.new_lchan = lchan_select_by_chan_mode(bts,
req->ch_mode_rate_list[i].chan_mode, req->ch_mode_rate_list[i].chan_rate);
if (!conn->assignment.new_lchan)
continue;
LOG_ASSIGNMENT(conn, LOGL_DEBUG, "selected new lchan %s for mode[%d] = %s channel_rate=%d\n",
gsm_lchan_name(conn->assignment.new_lchan),
i, gsm48_chan_mode_name(req->ch_mode_rate_list[i].chan_mode),
req->ch_mode_rate_list[i].chan_rate);
if (req->target_lchan) {
bool matching_mode;
conn->assignment.selected_ch_mode_rate = req->ch_mode_rate_list[i];
break;
/* The caller already picked a target lchan to assign to. No need to try re-using the current lchan or
* picking a new one. */
if (!lchan_state_is(req->target_lchan, LCHAN_ST_UNUSED)) {
assignment_fail(GSM0808_CAUSE_NO_RADIO_RESOURCE_AVAILABLE,
"Assignment to lchan %s requested, but lchan is already in use (state=%s)\n",
gsm_lchan_name(req->target_lchan),
osmo_fsm_inst_state_name(req->target_lchan->fi));
return;
}
conn->assignment.new_lchan = req->target_lchan;
matching_mode = false;
for (i = 0; i < req->n_ch_mode_rate; i++) {
if (!lchan_type_compat_with_mode(conn->assignment.new_lchan->type, &req->ch_mode_rate_list[i]))
continue;
conn->assignment.selected_ch_mode_rate = req->ch_mode_rate_list[i];
matching_mode = true;
}
if (!matching_mode) {
assignment_fail(GSM0808_CAUSE_NO_RADIO_RESOURCE_AVAILABLE,
"Assignment to lchan %s requested, but lchan is not compatible\n",
gsm_lchan_name(req->target_lchan));
return;
}
} else {
/* Try to allocate a new lchan in order of preference */
for (i = 0; i < req->n_ch_mode_rate; i++) {
conn->assignment.new_lchan = lchan_select_by_chan_mode(bts,
req->ch_mode_rate_list[i].chan_mode, req->ch_mode_rate_list[i].chan_rate);
if (!conn->assignment.new_lchan)
continue;
LOG_ASSIGNMENT(conn, LOGL_DEBUG, "selected new lchan %s for mode[%d] = %s channel_rate=%d\n",
gsm_lchan_name(conn->assignment.new_lchan),
i, gsm48_chan_mode_name(req->ch_mode_rate_list[i].chan_mode),
req->ch_mode_rate_list[i].chan_rate);
conn->assignment.selected_ch_mode_rate = req->ch_mode_rate_list[i];
break;
}
}
/* Check whether the lchan allocation was successful or not and tear