src/tbf.cpp

/* Copied from gprs_bssgp_pcu.cpp
 *
 * Copyright (C) 2012 Ivan Klyuchnikov
 * Copyright (C) 2012 Andreas Eversberg <jolly@eversberg.eu>
 * Copyright (C) 2013 by Holger Hans Peter Freyther
 *
 * 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 <bts.h>
#include <tbf.h>
#include <rlc.h>
#include <gprs_rlcmac.h>
#include <gprs_debug.h>

extern "C" {
#include <osmocom/core/msgb.h>
#include <osmocom/core/talloc.h>
}

#include <errno.h>
#include <string.h>

extern "C" {
int bssgp_tx_llc_discarded(struct bssgp_bvc_ctx *bctx, uint32_t tlli,
                           uint8_t num_frames, uint32_t num_octets);
}

extern void *tall_pcu_ctx;

static void tbf_timer_cb(void *_tbf);

static inline void tbf_update_ms_class(struct gprs_rlcmac_tbf *tbf,
					const uint8_t ms_class)
{
	if (!tbf->ms_class && ms_class)
		tbf->ms_class = ms_class;
}

static inline void tbf_assign_imsi(struct gprs_rlcmac_tbf *tbf,
					const char *imsi)
{
	strncpy(tbf->meas.imsi, imsi, sizeof(tbf->meas.imsi) - 1);
}

static struct gprs_rlcmac_tbf *tbf_lookup_dl(BTS *bts,
					const uint32_t tlli, const char *imsi)
{
	/* TODO: look up by IMSI first, then tlli, then old_tlli */
	return bts->tbf_by_tlli(tlli, GPRS_RLCMAC_DL_TBF);
}

static int tbf_append_data(struct gprs_rlcmac_tbf *tbf,
				struct gprs_rlcmac_bts *bts,
				const uint8_t ms_class,
				const uint16_t pdu_delay_csec,
				const uint8_t *data, const uint16_t len)
{
	LOGP(DRLCMAC, LOGL_INFO, "TBF: APPEND TFI: %u TLLI: 0x%08x\n", tbf->tfi, tbf->tlli);
	if (tbf->state_is(GPRS_RLCMAC_WAIT_RELEASE)) {
		LOGP(DRLCMAC, LOGL_DEBUG, "TBF in WAIT RELEASE state "
			"(T3193), so reuse TBF\n");
		memcpy(tbf->llc_frame, data, len);
		tbf->llc_length = len;
		/* reset rlc states */
		memset(&tbf->dir.dl, 0, sizeof(tbf->dir.dl));
		/* keep to flags */
		tbf->state_flags &= GPRS_RLCMAC_FLAG_TO_MASK;
		tbf->state_flags &= ~(1 << GPRS_RLCMAC_FLAG_CCCH);
		tbf_update_ms_class(tbf, ms_class);
		tbf->update();
		gprs_rlcmac_trigger_downlink_assignment(tbf, tbf, NULL);
	} else {
		/* the TBF exists, so we must write it in the queue
		 * we prepend lifetime in front of PDU */
		struct timeval *tv;
		struct msgb *llc_msg = msgb_alloc(len + sizeof(*tv),
			"llc_pdu_queue");
		if (!llc_msg)
			return -ENOMEM;
		tv = (struct timeval *)msgb_put(llc_msg, sizeof(*tv));

		uint16_t delay_csec;
		if (bts->force_llc_lifetime)
			delay_csec = bts->force_llc_lifetime;
		else
			delay_csec = pdu_delay_csec;
		/* keep timestap at 0 for infinite delay */
		if (delay_csec != 0xffff) {
			/* calculate timestamp of timeout */
			gettimeofday(tv, NULL);
			tv->tv_usec += (delay_csec % 100) * 10000;
			tv->tv_sec += delay_csec / 100;
			if (tv->tv_usec > 999999) {
				tv->tv_usec -= 1000000;
				tv->tv_sec++;
			}
		}
		memcpy(msgb_put(llc_msg, len), data, len);
		msgb_enqueue(&tbf->llc_queue, llc_msg);
		tbf_update_ms_class(tbf, ms_class);
	}

	return 0;
}

static int tbf_new_dl_assignment(struct gprs_rlcmac_bts *bts,
				const char *imsi,
				const uint32_t tlli, const uint8_t ms_class,
				const uint8_t *data, const uint16_t len)
{
	uint8_t trx, ta, ss;
	int8_t use_trx;
	struct gprs_rlcmac_tbf *old_tbf, *tbf;
	int8_t tfi; /* must be signed */
	int rc;

	/* check for uplink data, so we copy our informations */
#warning "Do the same look up for IMSI, TLLI and OLD_TLLI"
#warning "Refactor the below lines... into a new method"
	tbf = bts->bts->tbf_by_tlli(tlli, GPRS_RLCMAC_UL_TBF);
	if (tbf && tbf->dir.ul.contention_resolution_done
	 && !tbf->dir.ul.final_ack_sent) {
		use_trx = tbf->trx_no;
		ta = tbf->ta;
		ss = 0;
		old_tbf = tbf;
	} else {
		use_trx = -1;
		/* we already have an uplink TBF, so we use that TA */
		if (tbf)
			ta = tbf->ta;
		else {
			/* recall TA */
			rc = bts->bts->timing_advance()->recall(tlli);
			if (rc < 0) {
				LOGP(DRLCMAC, LOGL_NOTICE, "TA unknown"
					", assuming 0\n");
				ta = 0;
			} else
				ta = rc;
		}
		ss = 1; /* PCH assignment only allows one timeslot */
		old_tbf = NULL;
	}

	// Create new TBF (any TRX)
#warning "Copy and paste with alloc_ul_tbf"
	tfi = bts->bts->tfi_find_free(GPRS_RLCMAC_DL_TBF, &trx, use_trx);
	if (tfi < 0) {
		LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH resource\n");
		/* FIXME: send reject */
		return -EBUSY;
	}
	/* set number of downlink slots according to multislot class */
	tbf = tbf_alloc(bts, tbf, GPRS_RLCMAC_DL_TBF, tfi, trx, ms_class, ss);
	if (!tbf) {
		LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH ressource\n");
		/* FIXME: send reject */
		return -EBUSY;
	}
	tbf->tlli = tlli;
	tbf->tlli_valid = 1;
	tbf->ta = ta;

	LOGP(DRLCMAC, LOGL_DEBUG,
		"TBF: [DOWNLINK] START TFI: %d TLLI: 0x%08x \n",
		tbf->tfi, tbf->tlli);

	/* new TBF, so put first frame */
	memcpy(tbf->llc_frame, data, len);
	tbf->llc_length = len;

	/* trigger downlink assignment and set state to ASSIGN.
	 * we don't use old_downlink, so the possible uplink is used
	 * to trigger downlink assignment. if there is no uplink,
	 * AGCH is used. */
	gprs_rlcmac_trigger_downlink_assignment(tbf, old_tbf, imsi);

	/* store IMSI for debugging purpose. TODO: it is more than debugging */
	tbf_assign_imsi(tbf, imsi);
	return 0;
}

/**
 * TODO: split into unit test-able parts...
 */
int tbf_handle(struct gprs_rlcmac_bts *bts,
		const uint32_t tlli, const char *imsi,
		const uint8_t ms_class, const uint16_t delay_csec,
		const uint8_t *data, const uint16_t len)
{
	struct gprs_rlcmac_tbf *tbf;

	/* check for existing TBF */
	tbf = tbf_lookup_dl(bts->bts, tlli, imsi);
	if (tbf) {
		int rc = tbf_append_data(tbf, bts, ms_class,
						delay_csec, data, len);
		if (rc >= 0)
			tbf_assign_imsi(tbf, imsi);
		return rc;
	} 

	return tbf_new_dl_assignment(bts, imsi, tlli, ms_class, data, len);
}

struct gprs_rlcmac_tbf *tbf_alloc_ul(struct gprs_rlcmac_bts *bts,
	int8_t use_trx, uint8_t ms_class,
	uint32_t tlli, uint8_t ta, struct gprs_rlcmac_tbf *dl_tbf)
{
	uint8_t trx;
	struct gprs_rlcmac_tbf *tbf;
	uint8_t tfi;

#warning "Copy and paste with tbf_new_dl_assignment"
	/* create new TBF, use sme TRX as DL TBF */
	tfi = bts->bts->tfi_find_free(GPRS_RLCMAC_UL_TBF, &trx, use_trx);
	if (tfi < 0) {
		LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH ressource\n");
		/* FIXME: send reject */
		return NULL;
	}
	/* use multislot class of downlink TBF */
	tbf = tbf_alloc(bts, dl_tbf, GPRS_RLCMAC_UL_TBF, tfi, trx, ms_class, 0);
	if (!tbf) {
		LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH ressource\n");
		/* FIXME: send reject */
		return NULL;
	}
	tbf->tlli = tlli;
	tbf->tlli_valid = 1; /* no contention resolution */
	tbf->dir.ul.contention_resolution_done = 1;
	tbf->ta = ta; /* use current TA */
	tbf_new_state(tbf, GPRS_RLCMAC_ASSIGN);
	tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_PACCH);
	tbf_timer_start(tbf, 3169, bts->t3169, 0);

	return tbf;
}

static void tbf_unlink_pdch(struct gprs_rlcmac_tbf *tbf)
{
	struct gprs_rlcmac_pdch *pdch;
	int ts;

	if (tbf->direction == GPRS_RLCMAC_UL_TBF) {
		tbf->trx->ul_tbf[tbf->tfi] = NULL;
		for (ts = 0; ts < 8; ts++) {
			pdch = tbf->pdch[ts];
			if (pdch)
				pdch->ul_tbf[tbf->tfi] = NULL;
			tbf->pdch[ts] = NULL;
		}
	} else {
		tbf->trx->dl_tbf[tbf->tfi] = NULL;
		for (ts = 0; ts < 8; ts++) {
			pdch = tbf->pdch[ts];
			if (pdch)
				pdch->dl_tbf[tbf->tfi] = NULL;
			tbf->pdch[ts] = NULL;
		}
	}
}

void tbf_free(struct gprs_rlcmac_tbf *tbf)
{
	struct msgb *msg;

	/* Give final measurement report */
	gprs_rlcmac_rssi_rep(tbf);
	gprs_rlcmac_lost_rep(tbf);

	debug_diagram(tbf->bts, tbf->diag, "+---------------+");
	debug_diagram(tbf->bts, tbf->diag, "|    THE END    |");
	debug_diagram(tbf->bts, tbf->diag, "+---------------+");
	LOGP(DRLCMAC, LOGL_INFO, "Free %s TBF=%d with TLLI=0x%08x.\n",
		(tbf->direction == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL", tbf->tfi,
		tbf->tlli);
	if (tbf->ul_ass_state != GPRS_RLCMAC_UL_ASS_NONE)
		LOGP(DRLCMAC, LOGL_ERROR, "Software error: Pending uplink "
			"assignment. This may not happen, because the "
			"assignment message never gets transmitted. Please "
			"be sure not to free in this state. PLEASE FIX!\n");
	if (tbf->dl_ass_state != GPRS_RLCMAC_DL_ASS_NONE)
		LOGP(DRLCMAC, LOGL_ERROR, "Software error: Pending downlink "
			"assignment. This may not happen, because the "
			"assignment message never gets transmitted. Please "
			"be sure not to free in this state. PLEASE FIX!\n");
	tbf->stop_timer();
	#warning "TODO: Could/Should generate  bssgp_tx_llc_discarded"
	while ((msg = msgb_dequeue(&tbf->llc_queue)))
		msgb_free(msg);
	tbf_unlink_pdch(tbf);
	llist_del(&tbf->list);
	LOGP(DRLCMAC, LOGL_DEBUG, "********** TBF ends here **********\n");
	talloc_free(tbf);
}

int gprs_rlcmac_tbf::update()
{
	struct gprs_rlcmac_tbf *ul_tbf = NULL;
	struct gprs_rlcmac_bts *bts_data = bts->bts_data();
	int rc;

	LOGP(DRLCMAC, LOGL_DEBUG, "********** TBF update **********\n");

	if (direction != GPRS_RLCMAC_DL_TBF)
		return -EINVAL;

	if (!ms_class) {
		LOGP(DRLCMAC, LOGL_DEBUG, "- Cannot update, no class\n");
		return -EINVAL;
	}

	ul_tbf = bts->tbf_by_tlli(tlli, GPRS_RLCMAC_UL_TBF);

	tbf_unlink_pdch(this);
	rc = bts_data->alloc_algorithm(bts_data, ul_tbf, this, bts_data->alloc_algorithm_curst, 0);
	/* if no ressource */
	if (rc < 0) {
		LOGP(DRLCMAC, LOGL_ERROR, "No ressource after update???\n");
		return -rc;
	}

	return 0;
}

int tbf_assign_control_ts(struct gprs_rlcmac_tbf *tbf)
{
	if (tbf->control_ts == 0xff)
		LOGP(DRLCMAC, LOGL_INFO, "- Setting Control TS %d\n",
			tbf->first_common_ts);
	else if (tbf->control_ts != tbf->first_common_ts)
		LOGP(DRLCMAC, LOGL_INFO, "- Changing Control TS %d\n",
			tbf->first_common_ts);
	tbf->control_ts = tbf->first_common_ts;

	return 0;
}

static const char *tbf_state_name[] = {
	"NULL",
	"ASSIGN",
	"FLOW",
	"FINISHED",
	"WAIT RELEASE",
	"RELEASING",
};

void tbf_new_state(struct gprs_rlcmac_tbf *tbf,
	enum gprs_rlcmac_tbf_state state)
{
	debug_diagram(tbf->bts, tbf->diag, "->%s", tbf_state_name[state]);
	LOGP(DRLCMAC, LOGL_DEBUG, "%s TBF=%d changes state from %s to %s\n",
		(tbf->direction == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL", tbf->tfi,
		tbf_state_name[tbf->state], tbf_state_name[state]);
	tbf->set_state(state);
}

void tbf_timer_start(struct gprs_rlcmac_tbf *tbf, unsigned int T,
			unsigned int seconds, unsigned int microseconds)
{
	if (!osmo_timer_pending(&tbf->timer))
		LOGP(DRLCMAC, LOGL_DEBUG, "Starting %s TBF=%d timer %u.\n",
			(tbf->direction == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL",
			tbf->tfi, T);
	else
		LOGP(DRLCMAC, LOGL_DEBUG, "Restarting %s TBF=%d timer %u "
			"while old timer %u pending \n",
			(tbf->direction == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL",
			tbf->tfi, T, tbf->T);

	tbf->T = T;
	tbf->num_T_exp = 0;

	/* Tunning timers can be safely re-scheduled. */
	tbf->timer.data = tbf;
	tbf->timer.cb = &tbf_timer_cb;

	osmo_timer_schedule(&tbf->timer, seconds, microseconds);
}

void gprs_rlcmac_tbf::stop_t3191()
{
	return stop_timer();
}

void gprs_rlcmac_tbf::stop_timer()
{
	if (osmo_timer_pending(&timer)) {
		LOGP(DRLCMAC, LOGL_DEBUG, "Stopping %s TBF=%d timer %u.\n",
			(direction == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL", tfi, T);
		osmo_timer_del(&timer);
	}
}

struct gprs_rlcmac_tbf *tbf_alloc(struct gprs_rlcmac_bts *bts,
	struct gprs_rlcmac_tbf *old_tbf, enum gprs_rlcmac_tbf_direction dir,
	uint8_t tfi, uint8_t trx,
	uint8_t ms_class, uint8_t single_slot)
{
	struct gprs_rlcmac_tbf *tbf;
	int rc;

#ifdef DEBUG_DIAGRAM
	/* hunt for first free number in diagram */
	int diagram_num;
	for (diagram_num = 0; ; diagram_num++) {
		llist_for_each_entry(tbf, &bts->ul_tbfs, list) {
			if (tbf->diag == diagram_num)
				goto next_diagram;
		}
		llist_for_each_entry(tbf, &bts->dl_tbfs, list) {
			if (tbf->diag == diagram_num)
				goto next_diagram;
		}
		break;
next_diagram:
		continue;
	}
#endif

	LOGP(DRLCMAC, LOGL_DEBUG, "********** TBF starts here **********\n");
	LOGP(DRLCMAC, LOGL_INFO, "Allocating %s TBF: TFI=%d TRX=%d "
		"MS_CLASS=%d\n", (dir == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL",
		tfi, trx, ms_class);

	if (trx >= 8 || tfi >= 32)
		return NULL;

	tbf = talloc_zero(tall_pcu_ctx, struct gprs_rlcmac_tbf);
	if (!tbf)
		return NULL;

	tbf->bts = bts->bts;
#ifdef DEBUG_DIAGRAM
	tbf->diag = diagram_num;
#endif
	tbf->direction = dir;
	tbf->tfi = tfi;
	tbf->trx_no = trx;
	tbf->trx = &bts->trx[trx];
	tbf->arfcn = bts->trx[trx].arfcn;
	tbf->ms_class = ms_class;
	tbf->ws = 64;
	tbf->sns = 128;
	/* select algorithm */
	rc = bts->alloc_algorithm(bts, old_tbf, tbf, bts->alloc_algorithm_curst,
		single_slot);
	/* if no ressource */
	if (rc < 0) {
		talloc_free(tbf);
		return NULL;
	}
	/* assign control ts */
	tbf->control_ts = 0xff;
	rc = tbf_assign_control_ts(tbf);
	/* if no ressource */
	if (rc < 0) {
		talloc_free(tbf);
		return NULL;
	}

	/* set timestamp */
	gettimeofday(&tbf->meas.dl_bw_tv, NULL);
	gettimeofday(&tbf->meas.rssi_tv, NULL);
	gettimeofday(&tbf->meas.dl_loss_tv, NULL);

	INIT_LLIST_HEAD(&tbf->llc_queue);
	if (dir == GPRS_RLCMAC_UL_TBF)
		llist_add(&tbf->list, &bts->ul_tbfs);
	else
		llist_add(&tbf->list, &bts->dl_tbfs);

	debug_diagram(bts->bts, tbf->diag, "+-----------------+");
	debug_diagram(bts->bts, tbf->diag, "|NEW %s TBF TFI=%2d|",
		(dir == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL", tfi);
	debug_diagram(bts->bts, tbf->diag, "+-----------------+");

	return tbf;
}

static void tbf_timer_cb(void *_tbf)
{
	struct gprs_rlcmac_tbf *tbf = (struct gprs_rlcmac_tbf *)_tbf;
	tbf->handle_timeout();
}

void gprs_rlcmac_tbf::handle_timeout()
{
	LOGP(DRLCMAC, LOGL_DEBUG, "%s TBF=%d timer %u expired.\n",
		(direction == GPRS_RLCMAC_UL_TBF) ? "UL" : "DL", tfi, T);

	num_T_exp++;

	switch (T) {
#ifdef DEBUG_DL_ASS_IDLE
	case 1234:
		gprs_rlcmac_trigger_downlink_assignment(tbf, NULL, debug_imsi);
		break;
#endif
	case 0: /* assignment */
		if ((state_flags & (1 << GPRS_RLCMAC_FLAG_PACCH))) {
			if (state_is(GPRS_RLCMAC_ASSIGN)) {
				LOGP(DRLCMAC, LOGL_NOTICE, "Releasing due to "
					"PACCH assignment timeout.\n");
				tbf_free(this);
			} else
				LOGP(DRLCMAC, LOGL_ERROR, "Error: TBF is not "
					"in assign state\n");
		}
		if ((state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH))) {
			/* change state to FLOW, so scheduler will start transmission */
			dir.dl.wait_confirm = 0;
			if (state_is(GPRS_RLCMAC_ASSIGN)) {
				tbf_new_state(this, GPRS_RLCMAC_FLOW);
				tbf_assign_control_ts(this);
			} else
				LOGP(DRLCMAC, LOGL_NOTICE, "Continue flow after "
					"IMM.ASS confirm\n");
		}
		break;
	case 3169:
	case 3191:
	case 3195:
		LOGP(DRLCMAC, LOGL_NOTICE, "TBF T%d timeout during "
			"transsmission\n", T);
		rlcmac_diag();
		/* fall through */
	case 3193:
		if (T == 3193)
		        debug_diagram(bts, diag, "T3193 timeout");
		LOGP(DRLCMAC, LOGL_DEBUG, "TBF will be freed due to timeout\n");
		/* free TBF */
		tbf_free(this);
		break;
	default:
		LOGP(DRLCMAC, LOGL_ERROR, "Timer expired in unknown mode: %u\n", T);
	}
}

int gprs_rlcmac_tbf::rlcmac_diag()
{
	if ((state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH)))
		LOGP(DRLCMAC, LOGL_NOTICE, "- Assignment was on CCCH\n");
	if ((state_flags & (1 << GPRS_RLCMAC_FLAG_PACCH)))
		LOGP(DRLCMAC, LOGL_NOTICE, "- Assignment was on PACCH\n");
	if ((state_flags & (1 << GPRS_RLCMAC_FLAG_UL_DATA)))
		LOGP(DRLCMAC, LOGL_NOTICE, "- Uplink data was received\n");
	else if (direction == GPRS_RLCMAC_UL_TBF)
		LOGP(DRLCMAC, LOGL_NOTICE, "- No uplink data received yet\n");
	if ((state_flags & (1 << GPRS_RLCMAC_FLAG_DL_ACK)))
		LOGP(DRLCMAC, LOGL_NOTICE, "- Downlink ACK was received\n");
	else if (direction == GPRS_RLCMAC_DL_TBF)
		LOGP(DRLCMAC, LOGL_NOTICE, "- No downlink ACK received yet\n");

	return 0;
}

struct msgb *gprs_rlcmac_tbf::llc_dequeue(bssgp_bvc_ctx *bctx)
{
	struct msgb *msg;
	struct timeval *tv, tv_now;
	uint32_t octets = 0, frames = 0;

	gettimeofday(&tv_now, NULL);

	while ((msg = msgb_dequeue(&llc_queue))) {
		tv = (struct timeval *)msg->data;
		msgb_pull(msg, sizeof(*tv));
		if (tv->tv_sec /* not infinite */
		 && (tv_now.tv_sec > tv->tv_sec /* and secs expired */
		  || (tv_now.tv_sec == tv->tv_sec /* .. or if secs equal .. */
		   && tv_now.tv_usec > tv->tv_usec))) { /* .. usecs expired */
			LOGP(DRLCMACDL, LOGL_NOTICE, "Discarding LLC PDU of "
				"DL TBF=%d, because lifetime limit reached\n",
				tfi);
			frames++;
			octets += msg->len;
			msgb_free(msg);
			continue;
		}
		break;
	}

	if (frames) {
		if (frames > 0xff)
			frames = 0xff;
		if (octets > 0xffffff)
			octets = 0xffffff;
		bssgp_tx_llc_discarded(bctx, tlli, frames, octets);
	}

	return msg;
}

void gprs_rlcmac_tbf::update_llc_frame(struct msgb *msg)
{
	/* TODO: bounds check */
	memcpy(llc_frame, msg->data, msg->len);
	llc_length = msg->len;
}

/*
 * Store received block data in LLC message(s) and forward to SGSN
 * if complete.
 */
int gprs_rlcmac_tbf::assemble_forward_llc(uint8_t *data, uint8_t len)
{
	struct rlc_ul_header *rh = (struct rlc_ul_header *)data;
	uint8_t e, m;
	struct rlc_li_field *li;
	uint8_t frame_offset[16], offset = 0, chunk;
	int i, frames = 0;

	LOGP(DRLCMACUL, LOGL_DEBUG, "- Assembling frames: (len=%d)\n", len);

	data += 3;
	len -= 3;
	e = rh->e; /* if extended */
	m = 1; /* more frames, that means: the first frame */

	/* Parse frame offsets from length indicator(s), if any. */
	while (1) {
		if (frames == (int)sizeof(frame_offset)) {
			LOGP(DRLCMACUL, LOGL_ERROR, "Too many frames in "
				"block\n");
			return -EINVAL;
		}
		frame_offset[frames++] = offset;
		LOGP(DRLCMACUL, LOGL_DEBUG, "-- Frame %d starts at offset "
			"%d\n", frames, offset);
		if (!len)
			break;
		/* M == 0 and E == 0 is not allowed in this version. */
		if (!m && !e) {
			LOGP(DRLCMACUL, LOGL_NOTICE, "UL DATA TBF=%d "
				"ignored, because M='0' and E='0'.\n",
				this->tfi);
			return 0;
		}
		/* no more frames in this segment */
		if (e) {
			break;
		}
		/* There is a new frame and an LI that delimits it. */
		if (m) {
			li = (struct rlc_li_field *)data;
			LOGP(DRLCMACUL, LOGL_DEBUG, "-- Delimiter len=%d\n",
				li->li);
			/* Special case: LI == 0
			 * If the last segment would fit precisely into the
			 * rest of the RLC MAC block, there would be no way
			 * to delimit that this segment ends and is not
			 * continued in the next block.
			 * The special LI (0) is used to force the segment to
			 * extend into the next block, so it is delimited there.
			 * This LI must be skipped. Also it is the last LI.
			 */
			if (li->li == 0) {
				data++;
				len--;
				m = 1; /* M is ignored, we know there is more */
				break; /* handle E as '1', so we break! */
			}
			e = li->e;
			m = li->m;
			offset += li->li;
			data++;
			len--;
			continue;
		}
	}
	if (!m) {
		LOGP(DRLCMACUL, LOGL_DEBUG, "- Last frame carries spare "
			"data\n");
	}

	LOGP(DRLCMACUL, LOGL_DEBUG, "- Data length after length fields: %d\n",
		len);
	/* TLLI */
	if (rh->ti) {
		if (len < 4) {
			LOGP(DRLCMACUL, LOGL_NOTICE, "UL DATA TLLI out of "
				"frame border\n");
			return -EINVAL;
		}
		data += 4;
		len -= 4;
		LOGP(DRLCMACUL, LOGL_DEBUG, "- Length after skipping TLLI: "
			"%d\n", len);
	}

	/* PFI */
	if (rh->pi) {
		LOGP(DRLCMACUL, LOGL_ERROR, "ERROR: PFI not supported, "
			"please disable in SYSTEM INFORMATION\n");
		if (len < 1) {
			LOGP(DRLCMACUL, LOGL_NOTICE, "UL DATA PFI out of "
				"frame border\n");
			return -EINVAL;
		}
		data++;
		len--;
		LOGP(DRLCMACUL, LOGL_DEBUG, "- Length after skipping PFI: "
			"%d\n", len);
	}

	/* Now we have:
	 * - a list of frames offsets: frame_offset[]
	 * - number of frames: i
	 * - m == 0: Last frame carries spare data (end of TBF).
	 */

	/* Check if last offset would exceed frame. */
	if (offset > len) {
		LOGP(DRLCMACUL, LOGL_NOTICE, "UL DATA TBF=%d ignored, "
			"because LI delimits data that exceeds block size.\n",
			this->tfi);
		return -EINVAL;
	}

	/* create LLC frames */
	for (i = 0; i < frames; i++) {
		/* last frame ? */
		if (i == frames - 1) {
			/* no more data in last frame */
			if (!m)
				break;
			/* data until end of frame */
			chunk = len - frame_offset[i];
		} else {
			/* data until next frame */
			chunk = frame_offset[i + 1] - frame_offset[i];
		}
		LOGP(DRLCMACUL, LOGL_DEBUG, "-- Appending chunk (len=%d) to "
			"frame at %d.\n", chunk, this->llc_index);
		if (this->llc_index + chunk > LLC_MAX_LEN) {
			LOGP(DRLCMACUL, LOGL_NOTICE, "LLC frame exceeds "
				"maximum size.\n");
			chunk = LLC_MAX_LEN - this->llc_index;
		}
		memcpy(this->llc_frame + this->llc_index, data + frame_offset[i],
			chunk);
		this->llc_index += chunk;
		/* not last frame. */
		if (i != frames - 1) {
			/* send frame to SGSN */
			LOGP(DRLCMACUL, LOGL_INFO, "Complete UL frame for "
				"TBF=%d: len=%d\n", this->tfi, this->llc_index);
			gprs_rlcmac_tx_ul_ud(this);
			this->llc_index = 0; /* reset frame space */
		/* also check if CV==0, because the frame may fill up the
		 * block precisely, then it is also complete. normally the
		 * frame would be extended into the next block with a 0-length
		 * delimiter added to this block. */
		} else if (rh->cv == 0) {
			/* send frame to SGSN */
			LOGP(DRLCMACUL, LOGL_INFO, "Complete UL frame for "
				"TBF=%d that fits precisely in last block: "
				"len=%d\n", this->tfi, this->llc_index);
			gprs_rlcmac_tx_ul_ud(this);
			this->llc_index = 0; /* reset frame space */
		}
	}

	return 0;
}

void gprs_rlcmac_tbf::free_all(struct gprs_rlcmac_trx *trx)
{
	for (uint8_t tfi = 0; tfi < 32; tfi++) {
		struct gprs_rlcmac_tbf *tbf;

		tbf = trx->ul_tbf[tfi];
		if (tbf)
			tbf_free(tbf);
		tbf = trx->dl_tbf[tfi];
		if (tbf)
			tbf_free(tbf);
	}
}

void gprs_rlcmac_tbf::free_all(struct gprs_rlcmac_pdch *pdch)
{
	for (uint8_t tfi = 0; tfi < 32; tfi++) {
		struct gprs_rlcmac_tbf *tbf;

		tbf = pdch->ul_tbf[tfi];
		if (tbf)
			tbf_free(tbf);
		tbf = pdch->dl_tbf[tfi];
		if (tbf)
			tbf_free(tbf);
	}
}