Osmocom Packet control Unit (PCU): Network-side GPRS (RLC/MAC); BTS- or BSC-colocated https://osmocom.org/projects/osmopcu
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osmo-pcu/src/tbf_fsm.c

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/* tbf_fsm.c
*
* Copyright (C) 2021 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
* Author: Pau Espin Pedrol <pespin@sysmocom.de>
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <unistd.h>
#include <talloc.h>
#include <tbf_fsm.h>
#include <gprs_rlcmac.h>
#include <gprs_debug.h>
#include <gprs_ms.h>
#include <encoding.h>
#include <bts.h>
#define X(s) (1 << (s))
const struct osmo_tdef_state_timeout tbf_fsm_timeouts[32] = {
[TBF_ST_NEW] = {},
[TBF_ST_ASSIGN] = { },
[TBF_ST_FLOW] = { },
[TBF_ST_FINISHED] = {},
[TBF_ST_WAIT_RELEASE] = {},
[TBF_ST_RELEASING] = {},
};
const struct value_string tbf_fsm_event_names[] = {
{ TBF_EV_ASSIGN_ADD_CCCH, "ASSIGN_ADD_CCCH" },
{ TBF_EV_ASSIGN_ADD_PACCH, "ASSIGN_ADD_PACCH" },
{ TBF_EV_ASSIGN_ACK_PACCH, "ASSIGN_ACK_PACCH" },
{ TBF_EV_ASSIGN_READY_CCCH, "ASSIGN_READY_CCCH" },
{ TBF_EV_ASSIGN_PCUIF_CNF, "ASSIGN_PCUIF_CNF" },
{ TBF_EV_DL_ACKNACK_MISS, "DL_ACKNACK_MISS" },
{ TBF_EV_LAST_DL_DATA_SENT, "LAST_DL_DATA_SENT" },
{ TBF_EV_LAST_UL_DATA_RECVD, "LAST_UL_DATA_RECVD" },
{ TBF_EV_FINAL_ACK_RECVD, "FINAL_ACK_RECVD" },
{ TBF_EV_FINAL_UL_ACK_CONFIRMED, "FINAL_UL_ACK_CONFIRMED" },
{ TBF_EV_MAX_N3101 , "MAX_N3101" },
{ TBF_EV_MAX_N3103 , "MAX_N3103" },
{ TBF_EV_MAX_N3105 , "MAX_N3105" },
{ 0, NULL }
};
static void mod_ass_type(struct tbf_fsm_ctx *ctx, uint8_t t, bool set)
{
const char *ch = "UNKNOWN";
bool prev_set = ctx->state_flags & (1 << t);
switch (t) {
case GPRS_RLCMAC_FLAG_CCCH:
ch = "CCCH";
break;
case GPRS_RLCMAC_FLAG_PACCH:
ch = "PACCH";
break;
default:
LOGPTBF(ctx->tbf, LOGL_ERROR,
"attempted to %sset unexpected ass. type %d - FIXME!\n",
set ? "" : "un", t);
return;
}
if (set && prev_set) {
LOGPTBF(ctx->tbf, LOGL_ERROR,
"attempted to set ass. type %s which is already set.\n", ch);
} else if (!set && !prev_set) {
return;
}
LOGPTBF(ctx->tbf, LOGL_INFO, "%sset ass. type %s [prev CCCH:%u, PACCH:%u]\n",
set ? "" : "un", ch,
!!(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH)),
!!(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_PACCH)));
if (set) {
ctx->state_flags |= (1 << t);
} else {
ctx->state_flags &= GPRS_RLCMAC_FLAG_TO_MASK; /* keep to flags */
ctx->state_flags &= ~(1 << t);
}
}
static void st_new(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
switch (event) {
case TBF_EV_ASSIGN_ADD_CCCH:
mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, true);
tbf_fsm_state_chg(fi, tbf_direction(ctx->tbf) == GPRS_RLCMAC_DL_TBF ?
TBF_ST_ASSIGN : TBF_ST_FLOW);
break;
case TBF_EV_ASSIGN_ADD_PACCH:
mod_ass_type(ctx, GPRS_RLCMAC_FLAG_PACCH, true);
tbf_fsm_state_chg(fi, TBF_ST_ASSIGN);
break;
default:
OSMO_ASSERT(0);
}
}
static void st_assign_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
unsigned long val;
unsigned int sec, micro;
/* If assignment for this TBF is happening on PACCH, that means the
* actual Assignment procedure (tx/rx) is happening on another TBF (eg
* Ul TBF vs DL TBF). Hence we add a security timer here to free it in
* case the other TBF doesn't succeed in informing (assigning) the MS
* about this TBF, or simply because the scheduler takes too long to
* schedule it. This timer can probably be dropped once we make the
* other TBF always signal us assignment failure (we already get
* assignment success through TBF_EV_ASSIGN_ACK_PACCH) */
if (ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_PACCH)) {
fi->T = -2001;
val = osmo_tdef_get(the_pcu->T_defs, fi->T, OSMO_TDEF_MS, -1);
sec = val / 1000;
micro = (val % 1000) * 1000;
LOGPTBF(ctx->tbf, LOGL_DEBUG,
"Starting timer X2001 [assignment (PACCH)] with %u sec. %u microsec\n",
sec, micro);
osmo_timer_schedule(&fi->timer, sec, micro);
} else if (tbf_direction(ctx->tbf) == GPRS_RLCMAC_DL_TBF) {
/* GPRS_RLCMAC_FLAG_CCCH is set, so here we submitted an DL Ass through PCUIF on CCCH */
}
}
static void st_assign(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
unsigned long val;
unsigned int sec, micro;
switch (event) {
case TBF_EV_ASSIGN_ADD_CCCH:
mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, true);
break;
case TBF_EV_ASSIGN_ADD_PACCH:
mod_ass_type(ctx, GPRS_RLCMAC_FLAG_PACCH, true);
break;
case TBF_EV_ASSIGN_ACK_PACCH:
tbf_assign_control_ts(ctx->tbf);
if (ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH)) {
/* We now know that the PACCH really existed */
LOGPTBF(ctx->tbf, LOGL_INFO,
"The TBF has been confirmed on the PACCH, "
"changed type from CCCH to PACCH\n");
mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, false);
mod_ass_type(ctx, GPRS_RLCMAC_FLAG_PACCH, true);
}
tbf_fsm_state_chg(fi, TBF_ST_FLOW);
break;
case TBF_EV_ASSIGN_PCUIF_CNF:
/* BTS informs us it sent Imm Ass for DL TBF over CCCH. We now
* have to wait for X2002 to trigger (meaning MS is already
* listening on PDCH) in order to move to FLOW state and start
* transmitting data to it. When X2002 triggers (see cb timer
* end of the file) it will send TBF_EV_ASSIGN_READY_CCCH back
* to us here. */
OSMO_ASSERT(tbf_direction(ctx->tbf) == GPRS_RLCMAC_DL_TBF);
fi->T = -2002;
val = osmo_tdef_get(the_pcu->T_defs, fi->T, OSMO_TDEF_MS, -1);
sec = val / 1000;
micro = (val % 1000) * 1000;
LOGPTBF(ctx->tbf, LOGL_DEBUG,
"Starting timer X2002 [assignment (AGCH)] with %u sec. %u microsec\n",
sec, micro);
osmo_timer_schedule(&fi->timer, sec, micro);
break;
case TBF_EV_ASSIGN_READY_CCCH:
/* change state to FLOW, so scheduler will start transmission */
tbf_fsm_state_chg(fi, TBF_ST_FLOW);
break;
case TBF_EV_MAX_N3105:
/* We are going to release, so abort any Pkt Ul Ass pending to be scheduled: */
osmo_fsm_inst_dispatch(tbf_ul_ass_fi(ctx->tbf), TBF_UL_ASS_EV_ABORT, NULL);
ctx->T_release = 3195;
tbf_fsm_state_chg(fi, TBF_ST_RELEASING);
break;
default:
OSMO_ASSERT(0);
}
}
static void st_flow(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
switch (event) {
case TBF_EV_DL_ACKNACK_MISS:
/* DL TBF: we missed a DL ACK/NACK. If we started assignment
* over CCCH and never received any DL ACK/NACK yet, it means we
* don't even know if the MS successfuly received the Imm Ass on
* CCCH and hence is listening on PDCH. Let's better refrain
* from continuing and start assignment on CCCH again */
if ((ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH))
&& !(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_DL_ACK))) {
struct GprsMs *ms = tbf_ms(ctx->tbf);
const char *imsi = ms_imsi(ms);
uint16_t pgroup;
LOGPTBF(ctx->tbf, LOGL_DEBUG, "Re-send downlink assignment on PCH (IMSI=%s)\n",
imsi);
tbf_fsm_state_chg(fi, TBF_ST_ASSIGN);
/* send immediate assignment */
if ((pgroup = imsi2paging_group(imsi)) > 999)
LOGPTBF(ctx->tbf, LOGL_ERROR, "IMSI to paging group failed! (%s)\n", imsi);
bts_snd_dl_ass(ms->bts, ctx->tbf, pgroup);
}
break;
case TBF_EV_LAST_DL_DATA_SENT:
case TBF_EV_LAST_UL_DATA_RECVD:
/* All data has been sent or received, change state to FINISHED */
tbf_fsm_state_chg(fi, TBF_ST_FINISHED);
break;
case TBF_EV_FINAL_ACK_RECVD:
/* We received Final Ack (DL ACK/NACK) from MS. move to
WAIT_RELEASE, we wait there for release or re-use the TBF in
case we receive more DL data to tx */
tbf_fsm_state_chg(fi, TBF_ST_WAIT_RELEASE);
break;
case TBF_EV_MAX_N3101:
ctx->T_release = 3169;
tbf_fsm_state_chg(fi, TBF_ST_RELEASING);
break;
case TBF_EV_MAX_N3105:
ctx->T_release = 3195;
tbf_fsm_state_chg(fi, TBF_ST_RELEASING);
break;
default:
OSMO_ASSERT(0);
}
}
static void st_finished(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
switch (event) {
case TBF_EV_DL_ACKNACK_MISS:
break;
case TBF_EV_FINAL_ACK_RECVD:
/* We received Final Ack (DL ACK/NACK) from MS. move to
WAIT_RELEASE, we wait there for release or re-use the TBF in
case we receive more DL data to tx */
tbf_fsm_state_chg(fi, TBF_ST_WAIT_RELEASE);
break;
case TBF_EV_FINAL_UL_ACK_CONFIRMED:
/* UL TBF ACKed our transmitted UL ACK/NACK with final Ack
* Indicator set to '1' t. We can free the TBF right away. */
tbf_free(ctx->tbf);
break;
case TBF_EV_MAX_N3103:
ctx->T_release = 3169;
tbf_fsm_state_chg(fi, TBF_ST_RELEASING);
break;
case TBF_EV_MAX_N3105:
ctx->T_release = 3195;
tbf_fsm_state_chg(fi, TBF_ST_RELEASING);
break;
default:
OSMO_ASSERT(0);
}
}
static void st_wait_release_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
unsigned long val_s, val_ms, val_us;
OSMO_ASSERT(tbf_direction(ctx->tbf) == GPRS_RLCMAC_DL_TBF);
fi->T = 3193;
val_ms = osmo_tdef_get(tbf_ms(ctx->tbf)->bts->T_defs_bts, fi->T, OSMO_TDEF_MS, -1);
val_s = val_ms / 1000;
val_us = (val_ms % 1000) * 1000;
LOGPTBF(ctx->tbf, LOGL_DEBUG, "starting timer T%u with %lu sec. %lu microsec\n",
fi->T, val_s, val_us);
osmo_timer_schedule(&fi->timer, val_s, val_us);
mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, false);
}
static void st_wait_release(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
switch (event) {
case TBF_EV_FINAL_ACK_RECVD:
/* ignore, duplicate ACK, we already know about since we are in WAIT_RELEASE */
break;
case TBF_EV_MAX_N3101:
ctx->T_release = 3169;
tbf_fsm_state_chg(fi, TBF_ST_RELEASING);
break;
case TBF_EV_MAX_N3105:
ctx->T_release = 3195;
tbf_fsm_state_chg(fi, TBF_ST_RELEASING);
break;
default:
OSMO_ASSERT(0);
}
}
static void st_releasing_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
unsigned long val;
if (!ctx->T_release)
return;
/* In general we should end up here with an assigned timer in ctx->T_release. Possible values are:
* T3195: Wait for reuse of TFI(s) when there is no response from the MS
* (radio failure or cell change) for this TBF/MBMS radio bearer.
* T3169: Wait for reuse of USF and TFI(s) after the MS uplink assignment for this TBF is invalid.
*/
val = osmo_tdef_get(tbf_ms(ctx->tbf)->bts->T_defs_bts, ctx->T_release, OSMO_TDEF_S, -1);
fi->T = ctx->T_release;
LOGPTBF(ctx->tbf, LOGL_DEBUG, "starting timer T%u with %lu sec. %u microsec\n",
ctx->T_release, val, 0);
osmo_timer_schedule(&fi->timer, val, 0);
}
static void st_releasing(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
switch (event) {
case TBF_EV_DL_ACKNACK_MISS:
/* Ignore, we don't care about missed DL ACK/NACK poll timeouts
* anymore, we are already releasing the TBF */
break;
default:
OSMO_ASSERT(0);
}
}
static void handle_timeout_X2002(struct tbf_fsm_ctx *ctx)
{
struct gprs_rlcmac_dl_tbf *dl_tbf = as_dl_tbf(ctx->tbf);
/* X2002 is used only for DL TBF */
OSMO_ASSERT(dl_tbf);
if (ctx->fi->state == TBF_ST_ASSIGN) {
tbf_assign_control_ts(ctx->tbf);
if (!tbf_can_upgrade_to_multislot(ctx->tbf)) {
/* change state to FLOW, so scheduler
* will start transmission */
osmo_fsm_inst_dispatch(ctx->fi, TBF_EV_ASSIGN_READY_CCCH, NULL);
return;
}
/* This tbf can be upgraded to use multiple DL
* timeslots and now that there is already one
* slot assigned send another DL assignment via
* PDCH. */
/* keep to flags */
ctx->state_flags &= GPRS_RLCMAC_FLAG_TO_MASK;
tbf_update(ctx->tbf);
tbf_dl_trigger_ass(dl_tbf, ctx->tbf);
} else
LOGPTBF(ctx->tbf, LOGL_NOTICE, "Continue flow after IMM.ASS confirm\n");
}
static int tbf_fsm_timer_cb(struct osmo_fsm_inst *fi)
{
struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
switch (fi->T) {
case -2002:
handle_timeout_X2002(ctx);
break;
case -2001:
LOGPTBF(ctx->tbf, LOGL_NOTICE, "releasing due to PACCH assignment timeout.\n");
/* fall-through */
case 3169:
case 3193:
case 3195:
tbf_free(ctx->tbf);
break;
default:
OSMO_ASSERT(0);
}
return 0;
}
static struct osmo_fsm_state tbf_fsm_states[] = {
[TBF_ST_NEW] = {
.in_event_mask =
X(TBF_EV_ASSIGN_ADD_CCCH) |
X(TBF_EV_ASSIGN_ADD_PACCH),
.out_state_mask =
X(TBF_ST_ASSIGN) |
X(TBF_ST_FLOW) |
X(TBF_ST_RELEASING),
.name = "NEW",
.action = st_new,
},
[TBF_ST_ASSIGN] = {
.in_event_mask =
X(TBF_EV_ASSIGN_ADD_CCCH) |
X(TBF_EV_ASSIGN_ADD_PACCH) |
X(TBF_EV_ASSIGN_ACK_PACCH) |
X(TBF_EV_ASSIGN_PCUIF_CNF) |
X(TBF_EV_ASSIGN_READY_CCCH) |
X(TBF_EV_MAX_N3105),
.out_state_mask =
X(TBF_ST_FLOW) |
X(TBF_ST_FINISHED) |
X(TBF_ST_RELEASING),
.name = "ASSIGN",
.action = st_assign,
.onenter = st_assign_on_enter,
},
[TBF_ST_FLOW] = {
.in_event_mask =
X(TBF_EV_DL_ACKNACK_MISS) |
X(TBF_EV_LAST_DL_DATA_SENT) |
X(TBF_EV_LAST_UL_DATA_RECVD) |
X(TBF_EV_FINAL_ACK_RECVD) |
X(TBF_EV_MAX_N3101) |
X(TBF_EV_MAX_N3105),
.out_state_mask =
X(TBF_ST_ASSIGN) |
X(TBF_ST_FINISHED) |
X(TBF_ST_WAIT_RELEASE) |
X(TBF_ST_RELEASING),
.name = "FLOW",
.action = st_flow,
},
[TBF_ST_FINISHED] = {
.in_event_mask =
X(TBF_EV_DL_ACKNACK_MISS) |
X(TBF_EV_FINAL_ACK_RECVD) |
X(TBF_EV_FINAL_UL_ACK_CONFIRMED) |
X(TBF_EV_MAX_N3103) |
X(TBF_EV_MAX_N3105),
.out_state_mask =
X(TBF_ST_WAIT_RELEASE) |
X(TBF_ST_RELEASING),
.name = "FINISHED",
.action = st_finished,
},
[TBF_ST_WAIT_RELEASE] = {
.in_event_mask =
X(TBF_EV_FINAL_ACK_RECVD) |
X(TBF_EV_MAX_N3101) |
X(TBF_EV_MAX_N3105),
.out_state_mask =
X(TBF_ST_RELEASING),
.name = "WAIT_RELEASE",
.action = st_wait_release,
.onenter = st_wait_release_on_enter,
},
[TBF_ST_RELEASING] = {
.in_event_mask =
X(TBF_EV_DL_ACKNACK_MISS),
.out_state_mask =
0,
.name = "RELEASING",
.action = st_releasing,
.onenter = st_releasing_on_enter,
},
};
struct osmo_fsm tbf_fsm = {
.name = "TBF",
.states = tbf_fsm_states,
.num_states = ARRAY_SIZE(tbf_fsm_states),
.timer_cb = tbf_fsm_timer_cb,
.log_subsys = DTBF,
.event_names = tbf_fsm_event_names,
};
static __attribute__((constructor)) void tbf_fsm_init(void)
{
OSMO_ASSERT(osmo_fsm_register(&tbf_fsm) == 0);
}