src/bts.cpp

/*
 * Copyright (C) 2013 by Holger Hans Peter Freyther
 *
 * All Rights Reserved
 *
 * 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 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 <bts.h>
#include <poll_controller.h>
#include <tbf.h>
#include <encoding.h>
#include <decoding.h>
#include <rlc.h>
#include <pcu_l1_if.h>

#include <gprs_rlcmac.h>
#include <gprs_debug.h>

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

#include <arpa/inet.h>

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

extern void *tall_pcu_ctx;

static BTS s_bts;

/**
 * For gcc-4.4 compat do not use extended initializer list but keep the
 * order from the enum here. Once we support GCC4.7 and up we can change
 * the code below.
 */
static const struct rate_ctr_desc bts_ctr_description[] = {
	{ "tbf.dl.alloc",		"TBF DL Allocated     "},
	{ "tbf.dl.freed",		"TBF DL Freed         "},
	{ "tbf.ul.alloc",		"TBF UL Allocated     "},
	{ "tbf.ul.freed",		"TBF UL Freed         "},
	{ "decode.errors",		"Decode Errors        "},
	{ "sba.allocated",		"SBA Allocated        "},
	{ "sba.freed",			"SBA Freed            "},
	{ "sba.timedout",		"SBA Timeout          "},
	{ "llc.timeout",		"Timedout Frames      "},
	{ "llc.dropped",		"Dropped Frames       "},
	{ "rach.requests",		"RACH requests        "},
};

static const struct rate_ctr_group_desc bts_ctrg_desc = {
	"bts",
	"BTS Statistics",
	ARRAY_SIZE(bts_ctr_description),
	bts_ctr_description,
};

BTS* BTS::main_bts()
{
	return &s_bts;
}

struct gprs_rlcmac_bts *BTS::bts_data()
{
	return &m_bts;
}

struct gprs_rlcmac_bts *bts_main_data()
{
	return BTS::main_bts()->bts_data();
}

struct rate_ctr_group *bts_main_data_stats()
{
	return BTS::main_bts()->rate_counters();
}

BTS::BTS()
	: m_cur_fn(0)
	, m_pollController(*this)
	, m_sba(*this)
{
	memset(&m_bts, 0, sizeof(m_bts));
	INIT_LLIST_HEAD(&m_bts.ul_tbfs);
	INIT_LLIST_HEAD(&m_bts.dl_tbfs);
	m_bts.bts = this;

	/* initialize back pointers */
	for (size_t trx_no = 0; trx_no < ARRAY_SIZE(m_bts.trx); ++trx_no) {
		struct gprs_rlcmac_trx *trx = &m_bts.trx[trx_no];
		trx->trx_no = trx_no;
		trx->bts = this;

		for (size_t ts_no = 0; ts_no < ARRAY_SIZE(trx->pdch); ++ts_no) {
			struct gprs_rlcmac_pdch *pdch = &trx->pdch[ts_no];
			pdch->ts_no = ts_no;
			pdch->trx = trx;
		}
	}

	m_ratectrs = rate_ctr_group_alloc(tall_pcu_ctx, &bts_ctrg_desc, 0);
}

BTS::~BTS()
{
	rate_ctr_group_free(m_ratectrs);
}


void BTS::set_current_frame_number(int fn)
{
	m_cur_fn = fn;
	m_pollController.expireTimedout(m_cur_fn);
}

int BTS::add_paging(uint8_t chan_needed, uint8_t *identity_lv)
{
	uint8_t l, trx, ts, any_tbf = 0;
	struct gprs_rlcmac_tbf *tbf;
	struct gprs_rlcmac_paging *pag;
	uint8_t slot_mask[8];
	int8_t first_ts; /* must be signed */

	llist_head *tbfs_lists[] = {
		&m_bts.ul_tbfs,
		&m_bts.dl_tbfs,
		NULL
	};


	LOGP(DRLCMAC, LOGL_INFO, "Add RR paging: chan-needed=%d MI=%s\n",
		chan_needed, osmo_hexdump(identity_lv + 1, identity_lv[0]));

	/* collect slots to page
	 * Mark slots for every TBF, but only mark one of it.
	 * Mark only the first slot found.
	 * Don't mark, if TBF uses a different slot that is already marked. */
	memset(slot_mask, 0, sizeof(slot_mask));
	for (l = 0; tbfs_lists[l]; l++) {
		llist_for_each_entry(tbf, tbfs_lists[l], list) {
			first_ts = -1;
			for (ts = 0; ts < 8; ts++) {
				if (tbf->pdch[ts]) {
					/* remember the first slot found */
					if (first_ts < 0)
						first_ts = ts;
					/* break, if we already marked a slot */
					if ((slot_mask[tbf->trx->trx_no] & (1 << ts)))
						break;
				}
			}
			/* mark first slot found, if none is marked already */
			if (ts == 8 && first_ts >= 0) {
				LOGP(DRLCMAC, LOGL_DEBUG, "- %s uses "
					"TRX=%d TS=%d, so we mark\n",
					tbf_name(tbf),
					tbf->trx->trx_no, first_ts);
				slot_mask[tbf->trx->trx_no] |= (1 << first_ts);
			} else
				LOGP(DRLCMAC, LOGL_DEBUG, "- %s uses "
					"already marked TRX=%d TS=%d\n",
					tbf_name(tbf),
					tbf->trx->trx_no, ts);
		}
	}

	/* Now we have a list of marked slots. Every TBF uses at least one
	 * of these slots. */

	/* schedule paging to all marked slots */
	for (trx = 0; trx < 8; trx++) {
		if (slot_mask[trx] == 0)
			continue;
		for (ts = 0; ts < 8; ts++) {
			if ((slot_mask[trx] & (1 << ts))) {
				/* schedule */
				pag = talloc_zero(tall_pcu_ctx,
					struct gprs_rlcmac_paging);
				if (!pag)
					return -ENOMEM;
				pag->chan_needed = chan_needed;
				memcpy(pag->identity_lv, identity_lv,
					identity_lv[0] + 1);
				m_bts.trx[trx].pdch[ts].add_paging(pag);
				LOGP(DRLCMAC, LOGL_INFO, "Paging on PACCH of "
					"TRX=%d TS=%d\n", trx, ts);
				any_tbf = 1;
			}
		}
	}

	if (!any_tbf)
		LOGP(DRLCMAC, LOGL_INFO, "No paging, because no TBF\n");

	return 0;
}

/* search for active downlink or uplink tbf */
gprs_rlcmac_tbf *BTS::tbf_by_tlli(uint32_t tlli, enum gprs_rlcmac_tbf_direction dir)
{
	struct gprs_rlcmac_tbf *tbf;
	if (dir == GPRS_RLCMAC_UL_TBF) {
		llist_for_each_entry(tbf, &m_bts.ul_tbfs, list) {
			if (tbf->state_is_not(GPRS_RLCMAC_RELEASING)
			 && tbf->tlli() == tlli && tbf->is_tlli_valid())
				return tbf;
		}
	} else {
		llist_for_each_entry(tbf, &m_bts.dl_tbfs, list) {
			if (tbf->state_is_not(GPRS_RLCMAC_RELEASING)
			 && tbf->tlli() == tlli)
				return tbf;
		}
	}
	return NULL;
}

gprs_rlcmac_tbf *BTS::tbf_by_poll_fn(uint32_t fn, uint8_t trx, uint8_t ts)
{
	struct gprs_rlcmac_tbf *tbf;

	/* only one TBF can poll on specific TS/FN, because scheduler can only
	 * schedule one downlink control block (with polling) at a FN per TS */
	llist_for_each_entry(tbf, &m_bts.ul_tbfs, list) {
		if (tbf->state_is_not(GPRS_RLCMAC_RELEASING)
		 && tbf->poll_state == GPRS_RLCMAC_POLL_SCHED
		 && tbf->poll_fn == fn && tbf->trx->trx_no == trx
		 && tbf->control_ts == ts)
			return tbf;
	}
	llist_for_each_entry(tbf, &m_bts.dl_tbfs, list) {
		if (tbf->state_is_not(GPRS_RLCMAC_RELEASING)
		 && tbf->poll_state == GPRS_RLCMAC_POLL_SCHED
		 && tbf->poll_fn == fn && tbf->trx->trx_no == trx
		 && tbf->control_ts == ts)
			return tbf;
	}
	return NULL;
}

/* lookup TBF Entity (by TFI) */
gprs_rlcmac_tbf *BTS::tbf_by_tfi(uint8_t tfi, uint8_t trx,
				enum gprs_rlcmac_tbf_direction dir)
{
	struct gprs_rlcmac_tbf *tbf;

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

	if (dir == GPRS_RLCMAC_UL_TBF)
		tbf = m_bts.trx[trx].ul_tbf[tfi];
	else
		tbf = m_bts.trx[trx].dl_tbf[tfi];
	if (!tbf)
		return NULL;

	if (tbf->state_is_not(GPRS_RLCMAC_RELEASING))
		return tbf;

	return NULL;
}

/* FIXME: spread resources over multiple TRX. Also add option to use same
 * TRX in case of existing TBF for TLLI in the other direction. */
/* search for free TFI and return TFI, TRX */
int BTS::tfi_find_free(enum gprs_rlcmac_tbf_direction dir,
		uint8_t *_trx, int8_t use_trx)
{
	struct gprs_rlcmac_pdch *pdch;
	struct gprs_rlcmac_tbf **tbfp;
	uint8_t trx_from, trx_to, trx, ts, tfi;

	if (use_trx >= 0 && use_trx < 8)
		trx_from = trx_to = use_trx;
	else {
		trx_from = 0;
		trx_to = 7;
	}

	/* on TRX find first enabled TS */
	for (trx = trx_from; trx <= trx_to; trx++) {
		for (ts = 0; ts < 8; ts++) {
			pdch = &m_bts.trx[trx].pdch[ts];
			if (!pdch->is_enabled())
				continue;
			break;
		}
		if (ts < 8)
			break;
	}
	if (trx > trx_to) {
		LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH available.\n");
		return -EINVAL;
	}


	LOGP(DRLCMAC, LOGL_DEBUG, "Searching for first unallocated TFI: "
		"TRX=%d first TS=%d\n", trx, ts);
	if (dir == GPRS_RLCMAC_UL_TBF)
		tbfp = m_bts.trx[trx].ul_tbf;
	else
		tbfp = m_bts.trx[trx].dl_tbf;
	for (tfi = 0; tfi < 32; tfi++) {
		if (!tbfp[tfi])
			break;
	}

	if (tfi < 32) {
		LOGP(DRLCMAC, LOGL_DEBUG, " Found TFI=%d.\n", tfi);
		*_trx = trx;
		return tfi;
	}
	LOGP(DRLCMAC, LOGL_NOTICE, "No TFI available.\n");

	return -1;
}

int BTS::rcv_imm_ass_cnf(const uint8_t *data, uint32_t fn)
{
	struct gprs_rlcmac_tbf *tbf;
	uint8_t plen;
	uint32_t tlli;

	/* move to IA Rest Octets */
	plen = data[0] >> 2;
	data += 1 + plen;

	if ((*data & 0xf0) != 0xd0) {
		LOGP(DRLCMAC, LOGL_ERROR, "Got IMM.ASS confirm, but rest "
			"octets do not start with bit sequence 'HH01' "
			"(Packet Downlink Assignment)\n");
		return -EINVAL;
	}

	/* get TLLI from downlink assignment */
	tlli = (*data++) << 28;
	tlli |= (*data++) << 20;
	tlli |= (*data++) << 12;
	tlli |= (*data++) << 4;
	tlli |= (*data++) >> 4;

	tbf = tbf_by_tlli(tlli, GPRS_RLCMAC_DL_TBF);
	if (!tbf) {
		LOGP(DRLCMAC, LOGL_ERROR, "Got IMM.ASS confirm, but TLLI=%08x "
			"does not exit\n", tlli);
		return -EINVAL;
	}

	LOGP(DRLCMAC, LOGL_DEBUG, "Got IMM.ASS confirm for TLLI=%08x\n", tlli);

	if (tbf->dir.dl.wait_confirm)
		tbf_timer_start(tbf, 0, Tassign_agch);

	return 0;
}

int BTS::rcv_rach(uint8_t ra, uint32_t Fn, int16_t qta)
{
	struct gprs_rlcmac_tbf *tbf;
	uint8_t trx, ts = 0;
	int8_t tfi; /* must be signed */
	uint8_t sb = 0;
	uint32_t sb_fn = 0;
	int rc;
	uint8_t plen;

	rach_frame();

	LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF on RACH, so we provide "
		"one:\n");
	if ((ra & 0xf8) == 0x70) {
		LOGP(DRLCMAC, LOGL_DEBUG, "MS requests single block "
			"allocation\n");
		sb = 1;
	} else if (m_bts.force_two_phase) {
		LOGP(DRLCMAC, LOGL_DEBUG, "MS requests single phase access, "
			"but we force two phase access\n");
		sb = 1;
	}
	if (qta < 0)
		qta = 0;
	if (qta > 252)
		qta = 252;
	if (sb) {
		rc = sba()->alloc(&trx, &ts, &sb_fn, qta >> 2);
		if (rc < 0)
			return rc;
		LOGP(DRLCMAC, LOGL_DEBUG, "RX: [PCU <- BTS] RACH qbit-ta=%d "
			"ra=0x%02x, Fn=%d (%d,%d,%d)\n", qta, ra, Fn,
			(Fn / (26 * 51)) % 32, Fn % 51, Fn % 26);
		LOGP(DRLCMAC, LOGL_INFO, "TX: Immediate Assignment Uplink "
			"(AGCH)\n");
	} else {
		// Create new TBF
		#warning "Copy and pate with other routines.."
		tfi = tfi_find_free(GPRS_RLCMAC_UL_TBF, &trx, -1);
		if (tfi < 0) {
			LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH resource\n");
			/* FIXME: send reject */
			return -EBUSY;
		}
		/* set class to 0, since we don't know the multislot class yet */
		tbf = tbf_alloc(&m_bts, NULL, GPRS_RLCMAC_UL_TBF, tfi, trx, 0, 1);
		if (!tbf) {
			LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH resource\n");
			/* FIXME: send reject */
			return -EBUSY;
		}
		tbf->ta = qta >> 2;
		tbf_new_state(tbf, GPRS_RLCMAC_FLOW);
		tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_CCCH);
		tbf_timer_start(tbf, 3169, m_bts.t3169, 0);
		LOGP(DRLCMAC, LOGL_DEBUG, "%s [UPLINK] START\n",
			tbf_name(tbf));
		LOGP(DRLCMAC, LOGL_DEBUG, "%s RX: [PCU <- BTS] RACH "
			"qbit-ta=%d ra=0x%02x, Fn=%d (%d,%d,%d)\n",
			tbf_name(tbf),
			qta, ra, Fn, (Fn / (26 * 51)) % 32, Fn % 51, Fn % 26);
		LOGP(DRLCMAC, LOGL_INFO, "%s TX: START Immediate "
			"Assignment Uplink (AGCH)\n", tbf_name(tbf));
	}
	bitvec *immediate_assignment = bitvec_alloc(22) /* without plen */;
	bitvec_unhex(immediate_assignment,
		"2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b");
	if (sb)
		plen = Encoding::write_immediate_assignment(&m_bts, immediate_assignment, 0, ra,
			Fn, qta >> 2, m_bts.trx[trx].arfcn, ts,
			m_bts.trx[trx].pdch[ts].tsc, 0, 0, 0, 0, sb_fn, 1,
			m_bts.alpha, m_bts.gamma, -1);
	else
		plen = Encoding::write_immediate_assignment(&m_bts, immediate_assignment, 0, ra,
			Fn, tbf->ta, tbf->trx->arfcn, tbf->first_ts, tbf->tsc,
			tbf->tfi(), tbf->dir.ul.usf[tbf->first_ts], 0, 0, 0, 0,
			m_bts.alpha, m_bts.gamma, -1);
	pcu_l1if_tx_agch(immediate_assignment, plen);
	bitvec_free(immediate_assignment);

	return 0;
}

/* depending on the current TBF, we assign on PACCH or AGCH */
void BTS::trigger_dl_ass(
	struct gprs_rlcmac_tbf *tbf,
	struct gprs_rlcmac_tbf *old_tbf, const char *imsi)
{
	/* stop pending timer */
	tbf->stop_timer();

	/* check for downlink tbf:  */
	if (old_tbf) {
		LOGP(DRLCMAC, LOGL_DEBUG, "Send dowlink assignment on "
			"PACCH, because %s exists\n", tbf_name(old_tbf));
		old_tbf->dl_ass_state = GPRS_RLCMAC_DL_ASS_SEND_ASS;
		/* use TA from old TBF */
		tbf->ta = old_tbf->ta;
		/* change state */
		tbf_new_state(tbf, GPRS_RLCMAC_ASSIGN);
		tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_PACCH);
		/* start timer */
		tbf_timer_start(tbf, 0, Tassign_pacch);
	} else {
		LOGP(DRLCMAC, LOGL_DEBUG, "Send dowlink assignment for %s on PCH, no TBF exist (IMSI=%s)\n", tbf_name(tbf), imsi);
		if (!imsi || strlen(imsi) < 3) {
			LOGP(DRLCMAC, LOGL_ERROR, "No valid IMSI!\n");
			return;
		}
		/* change state */
		tbf_new_state(tbf, GPRS_RLCMAC_ASSIGN);
		tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_CCCH);
		tbf->assign_imsi(imsi);
		/* send immediate assignment */
		tbf->bts->snd_dl_ass(tbf, 0, imsi);
		tbf->dir.dl.wait_confirm = 1;
	}
}

void BTS::snd_dl_ass(gprs_rlcmac_tbf *tbf, uint8_t poll, const char *imsi)
{
	int plen;

	debug_diagram(this, tbf->diag, "IMM.ASS (PCH)");
	LOGP(DRLCMAC, LOGL_INFO, "TX: START %s Immediate Assignment Downlink (PCH)\n", tbf_name(tbf));
	bitvec *immediate_assignment = bitvec_alloc(22); /* without plen */
	bitvec_unhex(immediate_assignment, "2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b");
	/* use request reference that has maximum distance to current time,
	 * so the assignment will not conflict with possible RACH requests. */
	plen = Encoding::write_immediate_assignment(&m_bts, immediate_assignment, 1, 125,
		(tbf->pdch[tbf->first_ts]->last_rts_fn + 21216) % 2715648, tbf->ta,
		tbf->trx->arfcn, tbf->first_ts, tbf->tsc, tbf->tfi(), 0, tbf->tlli(), poll,
		tbf->poll_fn, 0, m_bts.alpha, m_bts.gamma, -1);
	pcu_l1if_tx_pch(immediate_assignment, plen, imsi);
	bitvec_free(immediate_assignment);
}


/*
 * PDCH code below. TODO: move to a separate file
 */

void gprs_rlcmac_pdch::enable()
{
	/* TODO: Check if there are still allocated resources.. */
	INIT_LLIST_HEAD(&paging_list);
	m_is_enabled = 1;
}

void gprs_rlcmac_pdch::disable()
{
	/* TODO.. kick free_resources once we know the TRX/TS we are on */
	m_is_enabled = 0;
}

/* TODO: kill the parameter and make a pdch belong to a trx.. to a bts.. */
void gprs_rlcmac_pdch::free_resources()
{
	struct gprs_rlcmac_paging *pag;

	/* we are not enabled. there should be no resources */
	if (!is_enabled())
		return;

	/* kick all TBF on slot */
	gprs_rlcmac_tbf::free_all(this);

	/* flush all pending paging messages */
	while ((pag = dequeue_paging()))
		talloc_free(pag);

	trx->bts->sba()->free_resources(this);
}

struct gprs_rlcmac_paging *gprs_rlcmac_pdch::dequeue_paging()
{
	struct gprs_rlcmac_paging *pag;

	if (llist_empty(&paging_list))
		return NULL;
	pag = llist_entry(paging_list.next, struct gprs_rlcmac_paging, list);
	llist_del(&pag->list);

	return pag;
}

struct msgb *gprs_rlcmac_pdch::packet_paging_request()
{
	struct gprs_rlcmac_paging *pag;
	struct msgb *msg;
	unsigned wp = 0, len;

	/* no paging, no message */
	pag = dequeue_paging();
	if (!pag)
		return NULL;

	LOGP(DRLCMAC, LOGL_DEBUG, "Scheduling paging\n");

	/* alloc message */
	msg = msgb_alloc(23, "pag ctrl block");
	if (!msg) {
		talloc_free(pag);
		return NULL;
	}
	bitvec *pag_vec = bitvec_alloc(23);
	if (!pag_vec) {
		msgb_free(msg);
		talloc_free(pag);
		return NULL;
	}
	wp = Encoding::write_packet_paging_request(pag_vec);

	/* loop until message is full */
	while (pag) {
		/* try to add paging */
		if ((pag->identity_lv[1] & 0x07) == 4) {
			/* TMSI */
			LOGP(DRLCMAC, LOGL_DEBUG, "- TMSI=0x%08x\n",
				ntohl(*((uint32_t *)(pag->identity_lv + 1))));
			len = 1 + 1 + 1 + 32 + 2 + 1;
			if (pag->identity_lv[0] != 5) {
				LOGP(DRLCMAC, LOGL_ERROR, "TMSI paging with "
					"MI != 5 octets!\n");
				goto continue_next;
			}
		} else {
			/* MI */
			LOGP(DRLCMAC, LOGL_DEBUG, "- MI=%s\n",
				osmo_hexdump(pag->identity_lv + 1,
					pag->identity_lv[0]));
			len = 1 + 1 + 1 + 4 + (pag->identity_lv[0]<<3) + 2 + 1;
			if (pag->identity_lv[0] > 8) {
				LOGP(DRLCMAC, LOGL_ERROR, "Paging with "
					"MI > 8 octets!\n");
				goto continue_next;
			}
		}
		if (wp + len > 184) {
			LOGP(DRLCMAC, LOGL_DEBUG, "- Does not fit, so schedule "
				"next time\n");
			/* put back paging record, because does not fit */
			llist_add_tail(&pag->list, &paging_list);
			break;
		}
		Encoding::write_repeated_page_info(pag_vec, wp, pag->identity_lv[0],
			pag->identity_lv + 1, pag->chan_needed);

continue_next:
		talloc_free(pag);
		pag = dequeue_paging();
	}

	bitvec_pack(pag_vec, msgb_put(msg, 23));
	RlcMacDownlink_t * mac_control_block = (RlcMacDownlink_t *)talloc_zero(tall_pcu_ctx, RlcMacDownlink_t);
	LOGP(DRLCMAC, LOGL_DEBUG, "+++++++++++++++++++++++++ TX : Packet Paging Request +++++++++++++++++++++++++\n");
	decode_gsm_rlcmac_downlink(pag_vec, mac_control_block);
	LOGPC(DCSN1, LOGL_NOTICE, "\n");
	LOGP(DRLCMAC, LOGL_DEBUG, "------------------------- TX : Packet Paging Request -------------------------\n");
	bitvec_free(pag_vec);
	talloc_free(mac_control_block);

	return msg;
}

void gprs_rlcmac_pdch::add_paging(struct gprs_rlcmac_paging *pag)
{
	llist_add(&pag->list, &paging_list);
}

/* receive UL data block
 *
 * The blocks are defragmented and forwarded as LLC frames, if complete.
 */
int gprs_rlcmac_pdch::rcv_data_block_acknowledged(uint8_t *data, uint8_t len, int8_t rssi)
{
	struct gprs_rlcmac_tbf *tbf;
	struct rlc_ul_header *rh = (struct rlc_ul_header *)data;

	switch (len) {
		case 54:
			/* omitting spare bits */
			len = 53;
			break;
		case 40:
			/* omitting spare bits */
			len = 39;
			break;
		case 34:
			/* omitting spare bits */
			len = 33;
			break;
		case 23:
			break;
	default:
		bts()->decode_error();
		LOGP(DRLCMACUL, LOGL_ERROR, "Dropping data block with invalid"
			"length: %d)\n", len);
		return -EINVAL;
	}

	/* find TBF inst from given TFI */
	tbf = bts()->tbf_by_tfi(rh->tfi, trx_no(), GPRS_RLCMAC_UL_TBF);
	if (!tbf) {
		LOGP(DRLCMACUL, LOGL_NOTICE, "UL DATA unknown TFI=%d\n",
			rh->tfi);
		return 0;
	}

	return tbf->rcv_data_block_acknowledged(data, len, rssi);
}

void gprs_rlcmac_pdch::rcv_control_ack(Packet_Control_Acknowledgement_t *packet, uint32_t fn)
{
	struct gprs_rlcmac_tbf *tbf;
	uint32_t tlli = 0;

	tlli = packet->TLLI;
	tbf = bts()->tbf_by_poll_fn(fn, trx_no(), ts_no);
	if (!tbf) {
		LOGP(DRLCMAC, LOGL_NOTICE, "PACKET CONTROL ACK with "
			"unknown FN=%u TLLI=0x%08x (TRX %d TS %d)\n",
			fn, tlli, trx_no(), ts_no);
		return;
	}
	tbf->update_tlli(tlli);
	LOGP(DRLCMAC, LOGL_DEBUG, "RX: [PCU <- BTS] %s Packet Control Ack\n", tbf_name(tbf));
	tbf->poll_state = GPRS_RLCMAC_POLL_NONE;

	/* check if this control ack belongs to packet uplink ack */
	if (tbf->ul_ack_state == GPRS_RLCMAC_UL_ACK_WAIT_ACK) {
		LOGP(DRLCMAC, LOGL_DEBUG, "TBF: [UPLINK] END %s\n", tbf_name(tbf));
		tbf->ul_ack_state = GPRS_RLCMAC_UL_ACK_NONE;
		debug_diagram(bts(), tbf->diag, "got CTL-ACK (fin)");
		if ((tbf->state_flags &
			(1 << GPRS_RLCMAC_FLAG_TO_UL_ACK))) {
			tbf->state_flags &=
				~(1 << GPRS_RLCMAC_FLAG_TO_UL_ACK);
				LOGP(DRLCMAC, LOGL_NOTICE, "Recovered uplink "
					"ack for UL %s\n", tbf_name(tbf));
		}
		tbf_free(tbf);
		return;
	}
	if (tbf->dl_ass_state == GPRS_RLCMAC_DL_ASS_WAIT_ACK) {
		LOGP(DRLCMAC, LOGL_DEBUG, "TBF: [UPLINK] DOWNLINK ASSIGNED %s\n", tbf_name(tbf));
		/* reset N3105 */
		tbf->n3105 = 0;
		tbf->dl_ass_state = GPRS_RLCMAC_DL_ASS_NONE;
		debug_diagram(bts(), tbf->diag, "got CTL-ACK DL-ASS");
		if (tbf->direction == GPRS_RLCMAC_UL_TBF)
			tbf = bts()->tbf_by_tlli(tbf->tlli(),
						GPRS_RLCMAC_DL_TBF);
#warning "TBF is changing on the way... *sigh*"
		if (!tbf) {
			LOGP(DRLCMAC, LOGL_ERROR, "Got ACK, but DL "
				"TBF is gone TLLI=0x%08x\n", tlli);
			return;
		}
		tbf_new_state(tbf, GPRS_RLCMAC_FLOW);
		/* stop pending assignment timer */
		tbf->stop_timer();
		if ((tbf->state_flags &
			(1 << GPRS_RLCMAC_FLAG_TO_DL_ASS))) {
			tbf->state_flags &=
				~(1 << GPRS_RLCMAC_FLAG_TO_DL_ASS);
			LOGP(DRLCMAC, LOGL_NOTICE, "Recovered downlink "
				"assignment for %s\n", tbf_name(tbf));
		}
		tbf_assign_control_ts(tbf);
		return;
	}
	if (tbf->ul_ass_state == GPRS_RLCMAC_UL_ASS_WAIT_ACK) {
		LOGP(DRLCMAC, LOGL_DEBUG, "TBF: [DOWNLINK] UPLINK ASSIGNED %s\n", tbf_name(tbf));
		/* reset N3105 */
		tbf->n3105 = 0;
		tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_NONE;
		debug_diagram(bts(), tbf->diag, "got CTL-AC UL-ASS");
#warning "TBF is changing on the way... *sigh*"
		if (tbf->direction == GPRS_RLCMAC_DL_TBF)
			tbf = bts()->tbf_by_tlli(tbf->tlli(),
						GPRS_RLCMAC_UL_TBF);
		if (!tbf) {
			LOGP(DRLCMAC, LOGL_ERROR, "Got ACK, but UL "
				"TBF is gone TLLI=0x%08x\n", tlli);
			return;
		}
		tbf_new_state(tbf, GPRS_RLCMAC_FLOW);
		if ((tbf->state_flags &
			(1 << GPRS_RLCMAC_FLAG_TO_UL_ASS))) {
			tbf->state_flags &=
				~(1 << GPRS_RLCMAC_FLAG_TO_UL_ASS);
			LOGP(DRLCMAC, LOGL_NOTICE, "Recovered uplink "
				"assignment for UL %s\n", tbf_name(tbf));
		}
		tbf_assign_control_ts(tbf);
		return;
	}
	LOGP(DRLCMAC, LOGL_ERROR, "Error: received PACET CONTROL ACK "
		"at no request\n");
}

void gprs_rlcmac_pdch::rcv_control_dl_ack_nack(Packet_Downlink_Ack_Nack_t *ack_nack, uint32_t fn)
{
	int8_t tfi = 0; /* must be signed */
	struct gprs_rlcmac_tbf *tbf;
	int rc;

	tfi = ack_nack->DOWNLINK_TFI;
	tbf = bts()->tbf_by_poll_fn(fn, trx_no(), ts_no);
	if (!tbf) {
		LOGP(DRLCMAC, LOGL_NOTICE, "PACKET DOWNLINK ACK with "
			"unknown FN=%u TFI=%d (TRX %d TS %d)\n",
			fn, tfi, trx_no(), ts_no);
		return;
	}
	if (tbf->tfi() != tfi) {
		LOGP(DRLCMAC, LOGL_NOTICE, "PACKET DOWNLINK ACK with "
			"wrong TFI=%d, ignoring!\n", tfi);
		return;
	}
	tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_DL_ACK);
	if ((tbf->state_flags & (1 << GPRS_RLCMAC_FLAG_TO_DL_ACK))) {
		tbf->state_flags &= ~(1 << GPRS_RLCMAC_FLAG_TO_DL_ACK);
		LOGP(DRLCMAC, LOGL_NOTICE, "Recovered downlink ack "
			"for %s\n", tbf_name(tbf));
	}
	/* reset N3105 */
	tbf->n3105 = 0;
	tbf->stop_t3191();
	LOGP(DRLCMAC, LOGL_DEBUG, "RX: [PCU <- BTS] %s Packet Downlink Ack/Nack\n", tbf_name(tbf));
	tbf->poll_state = GPRS_RLCMAC_POLL_NONE;
	debug_diagram(bts(), tbf->diag, "got DL-ACK");

	rc = tbf->snd_dl_ack(
		ack_nack->Ack_Nack_Description.FINAL_ACK_INDICATION,
		ack_nack->Ack_Nack_Description.STARTING_SEQUENCE_NUMBER,
		ack_nack->Ack_Nack_Description.RECEIVED_BLOCK_BITMAP);
	if (rc == 1) {
		tbf_free(tbf);
		return;
	}
	/* check for channel request */
	if (ack_nack->Exist_Channel_Request_Description) {
		LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
			"message, so we provide one:\n");
		tbf_alloc_ul(bts_data(), tbf->trx->trx_no, tbf->ms_class, tbf->tlli(), tbf->ta, tbf);
		/* schedule uplink assignment */
		tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS;
	}
}

void gprs_rlcmac_pdch::rcv_resource_request(Packet_Resource_Request_t *request, uint32_t fn)
{
	struct gprs_rlcmac_tbf *tbf;
	struct gprs_rlcmac_sba *sba;
	int rc;

	if (request->ID.UnionType) {
		uint32_t tlli = request->ID.u.TLLI;
		uint8_t ms_class = 0;
		struct gprs_rlcmac_tbf *dl_tbf;
		uint8_t ta;

		tbf = bts()->tbf_by_tlli(tlli, GPRS_RLCMAC_UL_TBF);
		if (tbf) {
			LOGP(DRLCMACUL, LOGL_NOTICE, "Got RACH from "
				"TLLI=0x%08x while %s still "
				"exists. Killing pending DL TBF\n",
				tlli, tbf_name(tbf));
			tbf_free(tbf);
			tbf = NULL;
		}

		if ((dl_tbf = bts()->tbf_by_tlli(tlli, GPRS_RLCMAC_DL_TBF))) {
			LOGP(DRLCMACUL, LOGL_NOTICE, "Got RACH from "
				"TLLI=0x%08x while %s still exists. "
				"Killing pending DL TBF\n", tlli,
				tbf_name(dl_tbf));
			tbf_free(dl_tbf);
		}
		LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF "
			"in packet resource request of single "
			"block, so we provide one:\n");
		sba = bts()->sba()->find(this, fn);
		if (!sba) {
			LOGP(DRLCMAC, LOGL_NOTICE, "MS requests UL TBF "
				"in packet resource request of single "
				"block, but there is no resource request "
				"scheduled!\n");
			rc = bts()->timing_advance()->recall(tlli);
			if (rc >= 0)
				ta = rc;
			else
				ta = 0;
		} else {
			ta = sba->ta;
			bts()->timing_advance()->remember(tlli, ta);
			bts()->sba()->free_sba(sba);
		}
		if (request->Exist_MS_Radio_Access_capability)
			ms_class = Decoding::get_ms_class_by_capability(&request->MS_Radio_Access_capability);
		if (!ms_class)
			LOGP(DRLCMAC, LOGL_NOTICE, "MS does not give us a class.\n");
		tbf = tbf_alloc_ul(bts_data(), trx_no(), ms_class, tlli, ta, NULL);
		if (!tbf)
			return;
		/* set control ts to current MS's TS, until assignment complete */
		LOGP(DRLCMAC, LOGL_DEBUG, "Change control TS to %d until assinment is complete.\n", ts_no);
		tbf->control_ts = ts_no;
		/* schedule uplink assignment */
		tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS;
		debug_diagram(bts->bts, tbf->diag, "Res. REQ");
		return;
	}

	if (request->ID.u.Global_TFI.UnionType) {
		int8_t tfi = request->ID.u.Global_TFI.u.DOWNLINK_TFI;
		tbf = bts()->tbf_by_tfi(tfi, trx_no(), GPRS_RLCMAC_DL_TBF);
		if (!tbf) {
			LOGP(DRLCMAC, LOGL_NOTICE, "PACKET RESSOURCE REQ unknown downlink TFI=%d\n", tfi);
			return;
		}
	} else {
		int8_t tfi = request->ID.u.Global_TFI.u.UPLINK_TFI;
		tbf = bts()->tbf_by_tfi(tfi, trx_no(), GPRS_RLCMAC_UL_TBF);
		if (!tbf) {
			LOGP(DRLCMAC, LOGL_NOTICE, "PACKET RESSOURCE REQ unknown uplink TFI=%d\n", tfi);
			return;
		}
	}

	LOGP(DRLCMAC, LOGL_ERROR, "RX: [PCU <- BTS] %s FIXME: Packet resource request\n", tbf_name(tbf));
}

void gprs_rlcmac_pdch::rcv_measurement_report(Packet_Measurement_Report_t *report, uint32_t fn)
{
	struct gprs_rlcmac_sba *sba;

	sba = bts()->sba()->find(this, fn);
	if (!sba) {
		LOGP(DRLCMAC, LOGL_NOTICE, "MS send measurement "
			"in packet resource request of single "
			"block, but there is no resource request "
			"scheduled! TLLI=0x%08x\n", report->TLLI);
	} else {
		bts()->timing_advance()->remember(report->TLLI, sba->ta);
		bts()->sba()->free_sba(sba);
	}
	gprs_rlcmac_meas_rep(report);
}

/* Received Uplink RLC control block. */
int gprs_rlcmac_pdch::rcv_control_block(
	bitvec *rlc_block, uint32_t fn)
{
	RlcMacUplink_t * ul_control_block = (RlcMacUplink_t *)talloc_zero(tall_pcu_ctx, RlcMacUplink_t);
	LOGP(DRLCMAC, LOGL_DEBUG, "+++++++++++++++++++++++++ RX : Uplink Control Block +++++++++++++++++++++++++\n");
	decode_gsm_rlcmac_uplink(rlc_block, ul_control_block);
	LOGPC(DCSN1, LOGL_NOTICE, "\n");
	LOGP(DRLCMAC, LOGL_DEBUG, "------------------------- RX : Uplink Control Block -------------------------\n");
	switch (ul_control_block->u.MESSAGE_TYPE) {
	case MT_PACKET_CONTROL_ACK:
		rcv_control_ack(&ul_control_block->u.Packet_Control_Acknowledgement, fn);
		break;
	case MT_PACKET_DOWNLINK_ACK_NACK:
		rcv_control_dl_ack_nack(&ul_control_block->u.Packet_Downlink_Ack_Nack, fn);
		break;
	case MT_PACKET_RESOURCE_REQUEST:
		rcv_resource_request(&ul_control_block->u.Packet_Resource_Request, fn);
		break;
	case MT_PACKET_MEASUREMENT_REPORT:
		rcv_measurement_report(&ul_control_block->u.Packet_Measurement_Report, fn);
		break;
	case MT_PACKET_UPLINK_DUMMY_CONTROL_BLOCK:
		/* ignoring it. change the SI to not force sending these? */
		break;
	default:
		bts()->decode_error();
		LOGP(DRLCMAC, LOGL_NOTICE,
			"RX: [PCU <- BTS] unknown control block(%d) received\n",
			ul_control_block->u.MESSAGE_TYPE);
	}
	talloc_free(ul_control_block);
	return 1;
}


/* received RLC/MAC block from L1 */
int gprs_rlcmac_pdch::rcv_block(uint8_t *data, uint8_t len, uint32_t fn, int8_t rssi)
{
	unsigned payload = data[0] >> 6;
	bitvec *block;
	int rc = 0;

	switch (payload) {
	case GPRS_RLCMAC_DATA_BLOCK:
		rc = rcv_data_block_acknowledged(data, len, rssi);
		break;
	case GPRS_RLCMAC_CONTROL_BLOCK:
		block = bitvec_alloc(len);
		if (!block)
			return -ENOMEM;
		bitvec_unpack(block, data);
		rc = rcv_control_block(block, fn);
		bitvec_free(block);
		break;
	case GPRS_RLCMAC_CONTROL_BLOCK_OPT:
		LOGP(DRLCMAC, LOGL_NOTICE, "GPRS_RLCMAC_CONTROL_BLOCK_OPT block payload is not supported.\n");
		break;
	default:
		LOGP(DRLCMAC, LOGL_NOTICE, "Unknown RLCMAC block payload(%u).\n", payload);
		rc = -EINVAL;
	}

	return rc;
}