osmo-bts/src/common/l1sap.c

/* L1 SAP primitives */

/* (C) 2011 by Harald Welte <laforge@gnumonks.org>
 * (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
 *
 * 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 <stdint.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <inttypes.h>

#include <osmocom/core/msgb.h>
#include <osmocom/gsm/l1sap.h>
#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/gsm/rsl.h>
#include <osmocom/core/gsmtap.h>
#include <osmocom/core/gsmtap_util.h>
#include <osmocom/core/utils.h>

#include <osmocom/trau/osmo_ortp.h>

#include <osmo-bts/logging.h>
#include <osmo-bts/gsm_data.h>
#include <osmo-bts/l1sap.h>
#include <osmo-bts/dtx_dl_amr_fsm.h>
#include <osmo-bts/pcu_if.h>
#include <osmo-bts/measurement.h>
#include <osmo-bts/bts.h>
#include <osmo-bts/rsl.h>
#include <osmo-bts/oml.h>
#include <osmo-bts/abis.h>
#include <osmo-bts/bts_model.h>
#include <osmo-bts/handover.h>
#include <osmo-bts/msg_utils.h>
#include <osmo-bts/pcuif_proto.h>
#include <osmo-bts/cbch.h>


#define CB_FCCH		-1
#define CB_SCH		-2
#define CB_BCCH		-3
#define CB_IDLE		-4

/* according to TS 05.02 Clause 7 Table 3 of 9 an Figure 8a */
static const int ccch_block_table[51] = {
	CB_FCCH, CB_SCH,/* 0..1 */
	CB_BCCH, CB_BCCH, CB_BCCH, CB_BCCH,	/* 2..5: BCCH */
	0, 0, 0, 0,	/* 6..9: B0 */
	CB_FCCH, CB_SCH,/* 10..11 */
	1, 1, 1, 1,	/* 12..15: B1 */
	2, 2, 2, 2,	/* 16..19: B2 */
	CB_FCCH, CB_SCH,/* 20..21 */
	3, 3, 3, 3,	/* 22..25: B3 */
	4, 4, 4, 4,	/* 26..29: B4 */
	CB_FCCH, CB_SCH,/* 30..31 */
	5, 5, 5, 5,	/* 32..35: B5 */
	6, 6, 6, 6,	/* 36..39: B6 */
	CB_FCCH, CB_SCH,/* 40..41 */
	7, 7, 7, 7, 	/* 42..45: B7 */
	8, 8, 8, 8, 	/* 46..49: B8 */
	-4		/* 50: Idle */
};

/* determine the CCCH block number based on the frame number */
unsigned int l1sap_fn2ccch_block(uint32_t fn)
{
	int rc = ccch_block_table[fn%51];
	/* if FN is negative, we were called for something that's not CCCH! */
	OSMO_ASSERT(rc >= 0);
	return rc;
}

struct gsm_lchan *get_lchan_by_chan_nr(struct gsm_bts_trx *trx,
				       unsigned int chan_nr)
{
	struct gsm_bts_trx_ts *ts;
	unsigned int tn, ss;

	tn = L1SAP_CHAN2TS(chan_nr);
	ts = &trx->ts[tn];

	if (L1SAP_IS_CHAN_VAMOS(chan_nr)) {
		if (ts->vamos.peer == NULL)
			return NULL;
		ts = ts->vamos.peer;
	}

	if (L1SAP_IS_CHAN_CBCH(chan_nr))
		ss = 2; /* CBCH is always on sub-slot 2 */
	else
		ss = l1sap_chan2ss(chan_nr);
	OSMO_ASSERT(ss < ARRAY_SIZE(ts->lchan));

	return &ts->lchan[ss];
}

static struct gsm_lchan *
get_active_lchan_by_chan_nr(struct gsm_bts_trx *trx, unsigned int chan_nr)
{
	struct gsm_lchan *lchan = get_lchan_by_chan_nr(trx, chan_nr);

	if (lchan && lchan->state != LCHAN_S_ACTIVE) {
		LOGPLCHAN(lchan, DL1P, LOGL_NOTICE, "assuming active lchan, but state is %s\n",
			  gsm_lchans_name(lchan->state));
		return NULL;
	}
	return lchan;
}

static int l1sap_down(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap);

static uint32_t fn_ms_adj(uint32_t fn, const struct gsm_lchan *lchan)
{
	uint32_t samples_passed, r;

	if (lchan->tch.last_fn != LCHAN_FN_DUMMY) {
		/* 12/13 frames usable for audio in TCH,
		   160 samples per RTP packet,
		   1 RTP packet per 4 frames */
		const uint32_t num_fn = GSM_TDMA_FN_SUB(fn, lchan->tch.last_fn);
		samples_passed = num_fn * 12 * 160 / (13 * 4);
		/* round number of samples to the nearest multiple of
		   GSM_RTP_DURATION */
		r = samples_passed + GSM_RTP_DURATION / 2;
		r -= r % GSM_RTP_DURATION;

		if (r != GSM_RTP_DURATION)
			LOGPLCHAN(lchan, DRTP, LOGL_ERROR, "RTP clock out of sync with lower layer:"
				  " %"PRIu32" vs %d (%"PRIu32"->%"PRIu32")\n",
				  r, GSM_RTP_DURATION, lchan->tch.last_fn, fn);
	}
	return GSM_RTP_DURATION;
}

/* allocate a msgb containing a osmo_phsap_prim + optional l2 data
 * in order to wrap femtobts header around l2 data, there must be enough space
 * in front and behind data pointer */
struct msgb *l1sap_msgb_alloc(unsigned int l2_len)
{
	const int headroom = L1SAP_MSGB_HEADROOM;
	const int size = headroom + sizeof(struct osmo_phsap_prim) + l2_len;
	struct msgb *msg = msgb_alloc_headroom(size, headroom, "l1sap_prim");

	if (!msg)
		return NULL;

	msg->l1h = msgb_put(msg, sizeof(struct osmo_phsap_prim));

	return msg;
}

/* Enclose rmsg into an osmo_phsap primitive and hand it over to the higher
 * layers. The phsap primitive also contains measurement information. The
 * parameters rssi, ta_offs and is_sub are only needed when the measurement
 * information is passed along with the TCH data. When separate measurement
 * indications are used, those last three parameters may be set to zero. */
int add_l1sap_header(struct gsm_bts_trx *trx, struct msgb *rmsg,
		     struct gsm_lchan *lchan, uint8_t chan_nr, uint32_t fn,
		     uint16_t ber10k, int16_t lqual_cb, int8_t rssi,
		     int16_t ta_offs, uint8_t is_sub)
{
	struct osmo_phsap_prim *l1sap;

	LOGPLCHAN(lchan, DL1P, LOGL_DEBUG, "Rx -> RTP: %s\n", osmo_hexdump(rmsg->data, rmsg->len));

	rmsg->l2h = rmsg->data;
	rmsg->l1h = msgb_push(rmsg, sizeof(*l1sap));
	l1sap = msgb_l1sap_prim(rmsg);
	osmo_prim_init(&l1sap->oph, SAP_GSM_PH, PRIM_TCH, PRIM_OP_INDICATION,
		       rmsg);
	l1sap->u.tch.chan_nr = chan_nr;
	l1sap->u.tch.fn = fn;
	l1sap->u.tch.ber10k = ber10k;
	l1sap->u.tch.lqual_cb = lqual_cb;

	l1sap->u.tch.rssi = rssi;
	l1sap->u.tch.ta_offs_256bits = ta_offs;
	l1sap->u.tch.is_sub = is_sub;

	return l1sap_up(trx, l1sap);
}

static int l1sap_tx_ciph_req(struct gsm_bts_trx *trx, uint8_t chan_nr,
	uint8_t downlink, uint8_t uplink)
{
	struct osmo_phsap_prim l1sap_ciph;

	osmo_prim_init(&l1sap_ciph.oph, SAP_GSM_PH, PRIM_MPH_INFO,
		PRIM_OP_REQUEST, NULL);
	l1sap_ciph.u.info.type = PRIM_INFO_ACT_CIPH;
	l1sap_ciph.u.info.u.ciph_req.chan_nr = chan_nr;
	l1sap_ciph.u.info.u.ciph_req.downlink = downlink;
	l1sap_ciph.u.info.u.ciph_req.uplink = uplink;

	return l1sap_down(trx, &l1sap_ciph);
}


/* check if the message is a GSM48_MT_RR_CIPH_M_CMD, and if yes, enable
 * uni-directional de-cryption on the uplink. We need this ugly layering
 * violation as we have no way of passing down L3 metadata (RSL CIPHERING CMD)
 * to this point in L1 */
static int check_for_ciph_cmd(struct msgb *msg, struct gsm_lchan *lchan,
	uint8_t chan_nr)
{
	uint8_t n_s;

	/* only do this if we are in the right state */
	switch (lchan->ciph_state) {
	case LCHAN_CIPH_NONE:
	case LCHAN_CIPH_RX_REQ:
		break;
	default:
		return 0;
	}

	/* First byte (Address Field) of LAPDm header) */
	if (msg->data[0] != 0x03)
		return 0;
	/* First byte (protocol discriminator) of RR */
	if ((msg->data[3] & 0xF) != GSM48_PDISC_RR)
		return 0;
	/* 2nd byte (msg type) of RR */
	if ((msg->data[4] & 0x3F) != GSM48_MT_RR_CIPH_M_CMD)
		return 0;

	/* Remember N(S) + 1 to find the first ciphered frame */
	n_s = (msg->data[1] >> 1) & 0x7;
	lchan->ciph_ns = (n_s + 1) % 8;

	l1sap_tx_ciph_req(lchan->ts->trx, chan_nr, 0, 1);

	return 1;
}

/* public helpers for the test */
int bts_check_for_ciph_cmd(struct msgb *msg, struct gsm_lchan *lchan,
			   uint8_t chan_nr)
{
	return check_for_ciph_cmd(msg, lchan, chan_nr);
}

uint16_t l1sap_log_ctx_sapi;

const struct value_string l1sap_common_sapi_names[] = {
	{ L1SAP_COMMON_SAPI_UNKNOWN,	"UNKNOWN" },
	/* alphabetic order */
	{ L1SAP_COMMON_SAPI_AGCH,	"AGCH" },
	{ L1SAP_COMMON_SAPI_BCCH,	"BCCH" },
	{ L1SAP_COMMON_SAPI_CBCH,	"CBCH" },
	{ L1SAP_COMMON_SAPI_FACCH_F,	"FACCH/F" },
	{ L1SAP_COMMON_SAPI_FACCH_H,	"FACCH/H" },
	{ L1SAP_COMMON_SAPI_FCCH,	"FCCH" },
	{ L1SAP_COMMON_SAPI_IDLE,	"IDLE" },
	{ L1SAP_COMMON_SAPI_NCH,	"NCH" },
	{ L1SAP_COMMON_SAPI_PACCH,	"PACCH" },
	{ L1SAP_COMMON_SAPI_PAGCH,	"PAGCH" },
	{ L1SAP_COMMON_SAPI_PBCCH,	"PBCCH" },
	{ L1SAP_COMMON_SAPI_PCH,	"PCH" },
	{ L1SAP_COMMON_SAPI_PDTCH,	"PDTCH" },
	{ L1SAP_COMMON_SAPI_PNCH,	"PNCH" },
	{ L1SAP_COMMON_SAPI_PPCH,	"PPCH" },
	{ L1SAP_COMMON_SAPI_PRACH,	"PRACH" },
	{ L1SAP_COMMON_SAPI_PTCCH,	"PTCCH" },
	{ L1SAP_COMMON_SAPI_RACH,	"RACH" },
	{ L1SAP_COMMON_SAPI_SACCH,	"SACCH" },
	{ L1SAP_COMMON_SAPI_SCH,	"SCH" },
	{ L1SAP_COMMON_SAPI_SDCCH,	"SDCCH" },
	{ L1SAP_COMMON_SAPI_TCH_F,	"TCH/F" },
	{ L1SAP_COMMON_SAPI_TCH_H,	"TCH/H" },
	{ 0, NULL }
};

static enum l1sap_common_sapi get_common_sapi_ph_data(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap)
{
	uint8_t link_id = l1sap->u.data.link_id;
	uint8_t chan_nr = l1sap->u.data.chan_nr;
	uint32_t u32Fn = l1sap->u.data.fn;

	if (L1SAP_IS_CHAN_TCHF(chan_nr))
		return L1SAP_COMMON_SAPI_TCH_F;

	if (L1SAP_IS_CHAN_TCHH(chan_nr))
		return L1SAP_COMMON_SAPI_TCH_H;

	if (L1SAP_IS_CHAN_SDCCH4(chan_nr) || L1SAP_IS_CHAN_SDCCH8(chan_nr))
		return L1SAP_COMMON_SAPI_SDCCH;

	if (L1SAP_IS_CHAN_BCCH(chan_nr))
		return L1SAP_COMMON_SAPI_BCCH;

	if (L1SAP_IS_CHAN_AGCH_PCH(chan_nr))
		/* The sapi depends on DSP configuration, not on the actual SYSTEM INFORMATION 3. */
		return ((l1sap_fn2ccch_block(u32Fn) >= num_agch(trx, "PH-DATA-REQ"))
			? L1SAP_COMMON_SAPI_PCH
			: L1SAP_COMMON_SAPI_AGCH);

	if (L1SAP_IS_CHAN_CBCH(chan_nr))
		return L1SAP_COMMON_SAPI_CBCH;

	if (L1SAP_IS_LINK_SACCH(link_id))
		return L1SAP_COMMON_SAPI_SACCH;

	return L1SAP_COMMON_SAPI_UNKNOWN;
}

static enum l1sap_common_sapi get_common_sapi_by_trx_prim(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap)
{
	/* Only downlink prims are relevant */
	switch (OSMO_PRIM_HDR(&l1sap->oph)) {
	case OSMO_PRIM(PRIM_PH_DATA, PRIM_OP_REQUEST):
		if (ts_is_pdch(&trx->ts[L1SAP_CHAN2TS(l1sap->u.data.chan_nr)]))
			return ((L1SAP_IS_PTCCH(l1sap->u.data.fn))
				? L1SAP_COMMON_SAPI_PTCCH
				: L1SAP_COMMON_SAPI_PDTCH);
		return get_common_sapi_ph_data(trx, l1sap);
	default:
		return L1SAP_COMMON_SAPI_UNKNOWN;
	}
}

/* send primitive as gsmtap */
static int gsmtap_ph_data(const struct osmo_phsap_prim *l1sap,
			  uint8_t *chan_type, uint8_t *ss, uint32_t fn,
			  uint8_t **data, unsigned int *len,
			  uint8_t num_agch)
{
	struct msgb *msg = l1sap->oph.msg;
	uint8_t chan_nr, link_id;

	*data = msgb_l2(msg);
	*len = msgb_l2len(msg);
	chan_nr = l1sap->u.data.chan_nr;
	link_id = l1sap->u.data.link_id;

	if (L1SAP_IS_CHAN_TCHF(chan_nr)) {
		*chan_type = GSMTAP_CHANNEL_TCH_F;
	} else if (L1SAP_IS_CHAN_TCHH(chan_nr)) {
		*ss = L1SAP_CHAN2SS_TCHH(chan_nr);
		*chan_type = GSMTAP_CHANNEL_TCH_H;
	} else if (L1SAP_IS_CHAN_SDCCH4(chan_nr)) {
		*ss = L1SAP_CHAN2SS_SDCCH4(chan_nr);
		*chan_type = GSMTAP_CHANNEL_SDCCH;
	} else if (L1SAP_IS_CHAN_SDCCH8(chan_nr)) {
		*ss = L1SAP_CHAN2SS_SDCCH8(chan_nr);
		*chan_type = GSMTAP_CHANNEL_SDCCH;
	} else if (L1SAP_IS_CHAN_BCCH(chan_nr)) {
		*chan_type = GSMTAP_CHANNEL_BCCH;
	} else if (L1SAP_IS_CHAN_AGCH_PCH(chan_nr)) {
		/* The sapi depends on DSP configuration, not
		 * on the actual SYSTEM INFORMATION 3. */
		if (l1sap_fn2ccch_block(fn) >= num_agch)
			*chan_type = GSMTAP_CHANNEL_PCH;
		else
			*chan_type = GSMTAP_CHANNEL_AGCH;
	} else if (L1SAP_IS_CHAN_CBCH(chan_nr)) {
		*chan_type = GSMTAP_CHANNEL_CBCH51;
	} else if (L1SAP_IS_CHAN_PDCH(chan_nr)) {
		*chan_type = GSMTAP_CHANNEL_PDTCH;
	}
	if (L1SAP_IS_LINK_SACCH(link_id))
		*chan_type |= GSMTAP_CHANNEL_ACCH;

	return 0;
}

static int gsmtap_pdch(const struct osmo_phsap_prim *l1sap,
		       uint8_t *chan_type, uint8_t *ss, uint32_t fn,
		       uint8_t **data, unsigned int *len)
{
	struct msgb *msg = l1sap->oph.msg;

	*data = msgb_l2(msg);
	*len = msgb_l2len(msg);

	if (L1SAP_IS_PTCCH(fn)) {
		*chan_type = GSMTAP_CHANNEL_PTCCH;
		*ss = L1SAP_FN2PTCCHBLOCK(fn);
	} else {
		/* TODO: distinguish PACCH */
		*chan_type = GSMTAP_CHANNEL_PDTCH;
	}

	return 0;
}

static int gsmtap_ph_rach(const struct osmo_phsap_prim *l1sap, uint8_t *chan_type,
			  uint8_t *tn, uint8_t *ss, uint32_t *fn,
			  uint8_t **data, unsigned int *len)
{
	uint8_t chan_nr = l1sap->u.rach_ind.chan_nr;
	static uint8_t ra_buf[2];

	*chan_type = GSMTAP_CHANNEL_RACH;
	*fn = l1sap->u.rach_ind.fn;
	*tn = L1SAP_CHAN2TS(chan_nr);

	if (L1SAP_IS_CHAN_TCHH(chan_nr))
		*ss = L1SAP_CHAN2SS_TCHH(chan_nr);
	else if (L1SAP_IS_CHAN_SDCCH4(chan_nr))
		*ss = L1SAP_CHAN2SS_SDCCH4(chan_nr);
	else if (L1SAP_IS_CHAN_SDCCH8(chan_nr))
		*ss = L1SAP_CHAN2SS_SDCCH8(chan_nr);
	else if (L1SAP_IS_CHAN_PDCH(chan_nr)) {
		if (L1SAP_IS_PTCCH(*fn)) {
			/* TODO: calculate sub-slot from frame-number */
			*chan_type = GSMTAP_CHANNEL_PTCCH;
		} else {
			*chan_type = GSMTAP_CHANNEL_PDTCH;
		}
	}

	if (l1sap->u.rach_ind.is_11bit) {
		/* Pack as described in 3GPP TS 44.004, figure 7.4a.b */
		ra_buf[0] = (uint8_t) (l1sap->u.rach_ind.ra >> 3);
		ra_buf[1] = (uint8_t) (l1sap->u.rach_ind.ra & 0x07);
		*len  = sizeof(ra_buf);
		*data = ra_buf;
	} else {
		ra_buf[0] = (uint8_t) (l1sap->u.rach_ind.ra & 0xff);
		*len  = sizeof(ra_buf[0]);
		*data = ra_buf;
	}

	return 0;
}

/* Paging Request 1 with "no identity" content, i.e. empty/dummy paging */
static const uint8_t paging_fill[GSM_MACBLOCK_LEN] = {
	0x15, 0x06, 0x21, 0x00, 0x01, 0xf0, 0x2b, 0x2b, 0x2b, 0x2b,
	0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,
	0x2b, 0x2b, 0x2b };

static bool is_fill_frame(uint8_t chan_type, const uint8_t *data, unsigned int len)
{
	if (len != GSM_MACBLOCK_LEN)
		return false;

	switch (chan_type) {
	case GSMTAP_CHANNEL_AGCH:
	case GSMTAP_CHANNEL_SDCCH:
	case GSMTAP_CHANNEL_TCH_F:
	case GSMTAP_CHANNEL_TCH_H:
		if (!memcmp(data, fill_frame, GSM_MACBLOCK_LEN))
			return true;
		break;
	case GSMTAP_CHANNEL_PCH:
		if (!memcmp(data, paging_fill, GSM_MACBLOCK_LEN))
			return true;
		break;
	/* FIXME: implement the same for GSMTAP_CHANNEL_PDTCH from/to PCU */
	/* don't use 'default' case here as the above only conditionally return true */
	}
	return false;
}

static int to_gsmtap(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap)
{
	uint8_t *data;
	unsigned int len;
	uint8_t chan_type = 0, tn = 0, ss = 0;
	uint32_t fn;
	uint16_t uplink = GSMTAP_ARFCN_F_UPLINK;
	int8_t signal_dbm;
	int rc;

	struct gsmtap_inst *inst = trx->bts->gsmtap.inst;
	if (!inst)
		return 0;

	switch (OSMO_PRIM_HDR(&l1sap->oph)) {
	case OSMO_PRIM(PRIM_PH_DATA, PRIM_OP_REQUEST):
		uplink = 0;
		/* fall through */
	case OSMO_PRIM(PRIM_PH_DATA, PRIM_OP_INDICATION):
		fn = l1sap->u.data.fn;
		tn = L1SAP_CHAN2TS(l1sap->u.data.chan_nr);
		if (ts_is_pdch(&trx->ts[tn]))
			rc = gsmtap_pdch(l1sap, &chan_type, &ss, fn, &data,
					 &len);
		else
			rc = gsmtap_ph_data(l1sap, &chan_type, &ss, fn, &data,
					    &len, num_agch(trx, "GSMTAP"));
		signal_dbm = l1sap->u.data.rssi;
		break;
	case OSMO_PRIM(PRIM_PH_RACH, PRIM_OP_INDICATION):
		rc = gsmtap_ph_rach(l1sap, &chan_type, &tn, &ss, &fn, &data,
			&len);
		signal_dbm = l1sap->u.rach_ind.rssi;
		break;
	default:
		rc = -ENOTSUP;
	}

	if (rc)
		return rc;

	if (len == 0)
		return 0;
	if ((chan_type & GSMTAP_CHANNEL_ACCH)) {
		if (!trx->bts->gsmtap.sapi_acch)
			return 0;
	} else {
		if (!((1 << (chan_type & 31)) & trx->bts->gsmtap.sapi_mask))
			return 0;
	}

	/* don't log fill frames via GSMTAP; they serve no purpose other than
	 * to clog up your logs */
	if (is_fill_frame(chan_type, data, len))
		return 0;

	gsmtap_send(inst, trx->arfcn | uplink, tn, chan_type, ss, fn,
		    signal_dbm, 0 /* TODO: SNR */, data, len);

	return 0;
}

/* Calculate the number of RACH slots that expire in a certain GSM frame
 * See also 3GPP TS 05.02 Clause 7 Table 5 of 9 */
static unsigned int calc_exprd_rach_frames(struct gsm_bts *bts, uint32_t fn)
{
	int rach_frames_expired = 0;
	uint8_t ccch_conf;
	struct gsm48_system_information_type_3 *si3;
	unsigned int blockno;

	si3 = GSM_BTS_SI(bts, SYSINFO_TYPE_3);
	ccch_conf = si3->control_channel_desc.ccch_conf;

	if (ccch_conf == RSL_BCCH_CCCH_CONF_1_C) {
		/* It is possible to combine a CCCH with an SDCCH4, in this
		 * case the CCCH will have to share the available frames with
		 * the other channel, this results in a limited number of
		 * available rach slots */
		blockno = fn % 51;
		if (blockno == 4 || blockno == 5
		    || (blockno >= 15 && blockno <= 36) || blockno == 45
		    || blockno == 46)
			rach_frames_expired = 1;
	} else {
		/* It is possible to have multiple CCCH channels on
		 * different physical channels (large cells), this
		 * also multiplies the available/expired RACH channels.
		 * See also TS 04.08, Chapter 10.5.2.11, table 10.29 */
		if (ccch_conf == RSL_BCCH_CCCH_CONF_2_NC)
			rach_frames_expired = 2;
		else if (ccch_conf == RSL_BCCH_CCCH_CONF_3_NC)
			rach_frames_expired = 3;
		else if (ccch_conf == RSL_BCCH_CCCH_CONF_4_NC)
			rach_frames_expired = 4;
		else
			rach_frames_expired = 1;
	}

	return rach_frames_expired;
}

static void l1sap_interf_meas_calc_avg(struct gsm_bts_trx *trx)
{
	unsigned int tn, ln;

	for (tn = 0; tn < ARRAY_SIZE(trx->ts); tn++) {
		struct gsm_bts_trx_ts *ts = &trx->ts[tn];

		if (ts->mo.nm_state.operational != NM_OPSTATE_ENABLED)
			continue;
		if (ts->mo.nm_state.availability != NM_AVSTATE_OK)
			continue;

		for (ln = 0; ln < ARRAY_SIZE(ts->lchan); ln++) {
			struct gsm_lchan *lchan = &ts->lchan[ln];

			lchan->meas.interf_meas_avg_dbm = 0;
			lchan->meas.interf_band = 0;

			/* There must be at least one sample */
			if (lchan->meas.interf_meas_num == 0)
				continue;

			/* Average all collected samples */
			gsm_lchan_interf_meas_calc_avg(lchan);
		}
	}
}

static void l1sap_interf_meas_report(struct gsm_bts *bts)
{
	const uint32_t period = bts->interference.intave * 104;
	struct gsm_bts_trx *trx;

	if (bts->interference.intave == 0)
		return;
	if (bts->gsm_time.fn % period != 0)
		return;

	llist_for_each_entry(trx, &bts->trx_list, list) {
		/* Calculate the average of all received samples */
		l1sap_interf_meas_calc_avg(trx);
		/* Report to the BSC over the A-bis/RSL */
		rsl_tx_rf_res(trx);
		/* Report to the PCU over the PCUIF */
		pcu_tx_interf_ind(trx, bts->gsm_time.fn);
	}
}

/* time information received from bts model */
static int l1sap_info_time_ind(struct gsm_bts *bts,
			       struct osmo_phsap_prim *l1sap,
			       struct info_time_ind_param *info_time_ind)
{
	unsigned int frames_expired;
	unsigned int i;

	DEBUGPFN(DL1P, info_time_ind->fn, "Rx MPH_INFO time ind\n");

	/* Calculate and check frame difference */
	frames_expired = GSM_TDMA_FN_SUB(info_time_ind->fn, bts->gsm_time.fn);
	if (frames_expired > 1) {
		if (bts->gsm_time.fn)
			LOGPFN(DL1P, LOGL_ERROR, info_time_ind->fn,
			     "Invalid condition detected: Frame difference is %"PRIu32"-%"PRIu32"=%u > 1!\n",
			     info_time_ind->fn, bts->gsm_time.fn, frames_expired);
	}

	/* Update our data structures with the current GSM time */
	gsm_fn2gsmtime(&bts->gsm_time, info_time_ind->fn);

	/* Update time on PCU interface */
	pcu_tx_time_ind(info_time_ind->fn);

	/* increment number of RACH slots that have passed by since the
	 * last time indication */
	for (i = 0; i < frames_expired; i++) {
		uint32_t fn = GSM_TDMA_FN_SUB(info_time_ind->fn, i);
		bts->load.rach.total += calc_exprd_rach_frames(bts, fn);
	}

	/* Report interference levels to the BSC */
	if (bts_internal_flag_get(bts, BTS_INTERNAL_FLAG_INTERF_MEAS))
		l1sap_interf_meas_report(bts);

	return 0;
}

static inline void set_ms_to_data(struct gsm_lchan *lchan, int16_t data, bool set_ms_to)
{
	if (!lchan)
		return;

	if (data + 63 > 255) { /* According to 3GPP TS 48.058 §9.3.37 Timing Offset field cannot exceed 255 */
		LOGPLCHAN(lchan, DL1P, LOGL_ERROR, "Attempting to set invalid Timing Offset value "
			  "%d (MS TO = %u)!\n", data, set_ms_to);
		return;
	}

	if (set_ms_to) {
		lchan->ms_t_offs = data + 63;
		lchan->p_offs = -1;
	} else {
		lchan->p_offs = data + 63;
		lchan->ms_t_offs = -1;
	}
}

bool trx_sched_is_sacch_fn(const struct gsm_bts_trx_ts *ts, uint32_t fn, bool uplink);

/* measurement information received from bts model */
static void process_l1sap_meas_data(struct gsm_lchan *lchan,
				    const struct osmo_phsap_prim *l1sap,
				    enum osmo_ph_prim ind_type)
{
	struct bts_ul_meas ulm;
	const struct info_meas_ind_param *info_meas_ind;
	const struct ph_data_param *ph_data_ind;
	const struct ph_tch_param *ph_tch_ind;
	uint32_t fn;
	const char *ind_name;

	switch (ind_type) {
	case PRIM_MPH_INFO:
		/* (legacy way, see also OS#2977) */
	        info_meas_ind = &l1sap->u.info.u.meas_ind;
		fn = info_meas_ind->fn;
		ind_name = "MPH INFO";
		ulm = (struct bts_ul_meas) {
			.ta_offs_256bits = info_meas_ind->ta_offs_256bits,
			.inv_rssi = info_meas_ind->inv_rssi,
			.ber10k = info_meas_ind->ber10k,
			.ci_cb = info_meas_ind->c_i_cb,
		};
		/* additionally treat SACCH frames (match by TDMA FN) as SUB frames */
		if (info_meas_ind->is_sub || trx_sched_is_sacch_fn(lchan->ts, fn, true))
			ulm.is_sub = 1;
		break;
	case PRIM_TCH:
		ph_tch_ind = &l1sap->u.tch;
		if (ph_tch_ind->rssi == 0)
			return;
		fn = ph_tch_ind->fn;
		ind_name = "TCH";
		ulm = (struct bts_ul_meas) {
			.ta_offs_256bits = ph_tch_ind->ta_offs_256bits,
			.inv_rssi = abs(ph_tch_ind->rssi),
			.ber10k = ph_tch_ind->ber10k,
			.ci_cb = ph_tch_ind->lqual_cb,
			.is_sub = ph_tch_ind->is_sub,
		};
		/* PRIM_TCH always carries DCCH, not SACCH */
		break;
	case PRIM_PH_DATA:
		ph_data_ind = &l1sap->u.data;
		if (ph_data_ind->rssi == 0)
			return;
		fn = ph_data_ind->fn;
		ind_name = "DATA";
		ulm = (struct bts_ul_meas) {
			.ta_offs_256bits = ph_data_ind->ta_offs_256bits,
			.inv_rssi = abs(ph_data_ind->rssi),
			.ber10k = ph_data_ind->ber10k,
			.ci_cb = ph_data_ind->lqual_cb,
		};
		/* additionally treat SACCH frames (match by RSL link ID) as SUB frames */
		if (ph_data_ind->is_sub || L1SAP_IS_LINK_SACCH(ph_data_ind->link_id))
			ulm.is_sub = 1;
		break;
	default:
		OSMO_ASSERT(false);
	}

	DEBUGPFN(DL1P, fn,
		 "%s %s meas ind, ta_offs_256bits=%d, ber10k=%d, inv_rssi=%u, C/I=%d cB\n",
		 gsm_lchan_name(lchan), ind_name, ulm.ta_offs_256bits,
		 ulm.ber10k, ulm.inv_rssi, ulm.ci_cb);

	/* we assume that symbol period is 1 bit: */
	set_ms_to_data(lchan, ulm.ta_offs_256bits / 256, true);

	lchan_meas_process_measurement(lchan, &ulm, fn);

	return;
}

/* any L1 MPH_INFO indication prim received from bts model */
static int l1sap_mph_info_ind(struct gsm_bts_trx *trx,
	 struct osmo_phsap_prim *l1sap, struct mph_info_param *info)
{
	const struct info_meas_ind_param *meas_ind;
	struct gsm_lchan *lchan;
	int rc = 0;

	switch (info->type) {
	case PRIM_INFO_TIME:
		if (trx != trx->bts->c0) {
			LOGPFN(DL1P, LOGL_NOTICE, info->u.time_ind.fn,
				"BTS model is sending us PRIM_INFO_TIME for TRX %u, please fix it\n",
				trx->nr);
			rc = -1;
		} else
			rc = l1sap_info_time_ind(trx->bts, l1sap,
						 &info->u.time_ind);
		break;
	case PRIM_INFO_MEAS:
		/* We should never get an INFO_IND with PRIM_INFO_MEAS
		 * when BTS_INTERNAL_FLAG_MEAS_PAYLOAD_COMB is set */
		if (bts_internal_flag_get(trx->bts, BTS_INTERNAL_FLAG_MEAS_PAYLOAD_COMB))
			OSMO_ASSERT(false);

		meas_ind = &l1sap->u.info.u.meas_ind;

		lchan = get_active_lchan_by_chan_nr(trx, meas_ind->chan_nr);
		if (!lchan) {
			LOGPFN(DL1P, LOGL_ERROR, meas_ind->fn,
			       "No lchan for chan_nr=%s\n",
			       rsl_chan_nr_str(meas_ind->chan_nr));
			return 0;
		}

		process_l1sap_meas_data(lchan, l1sap, PRIM_MPH_INFO);
		break;
	default:
		LOGP(DL1P, LOGL_NOTICE, "unknown MPH_INFO ind type %d\n",
			info->type);
		break;
	}

	return rc;
}

/* activation confirm received from bts model */
static int l1sap_info_act_cnf(struct gsm_bts_trx *trx,
	struct osmo_phsap_prim *l1sap,
	struct info_act_cnf_param *info_act_cnf)
{
	struct gsm_lchan *lchan = get_lchan_by_chan_nr(trx, info_act_cnf->chan_nr);
	if (lchan == NULL) {
		LOGPTRX(trx, DL1C, LOGL_ERROR, "get_lchan_by_chan_nr(chan_nr=%s) "
			"yields NULL for PRIM_INFO_ACTIVATE.conf\n",
			rsl_chan_nr_str(info_act_cnf->chan_nr));
		return -ENODEV;
	}

	LOGPLCHAN(lchan, DL1C, LOGL_INFO, "activate confirm chan_nr=%s trx=%d\n",
		  rsl_chan_nr_str(info_act_cnf->chan_nr), trx->nr);

	rsl_tx_chan_act_acknack(lchan, info_act_cnf->cause);

	/* During PDCH ACT, this is where we know that the PCU is done
	 * activating a PDCH, and PDCH switchover is complete.  See
	 * rsl_rx_dyn_pdch() */
	if (lchan->ts->pchan == GSM_PCHAN_TCH_F_PDCH
	    && (lchan->ts->flags & TS_F_PDCH_ACT_PENDING))
		ipacc_dyn_pdch_complete(lchan->ts,
					info_act_cnf->cause? -EIO : 0);

	return 0;
}

/* activation confirm received from bts model */
static int l1sap_info_rel_cnf(struct gsm_bts_trx *trx,
	struct osmo_phsap_prim *l1sap,
	struct info_act_cnf_param *info_act_cnf)
{
	struct gsm_lchan *lchan = get_lchan_by_chan_nr(trx, info_act_cnf->chan_nr);
	if (lchan == NULL) {
		LOGPTRX(trx, DL1C, LOGL_ERROR, "get_lchan_by_chan_nr(chan_nr=%s) "
			"yields NULL for PRIM_INFO_ACTIVATE.conf\n",
			rsl_chan_nr_str(info_act_cnf->chan_nr));
		return -ENODEV;
	}

	LOGPLCHAN(lchan, DL1C, LOGL_INFO, "deactivate confirm chan_nr=%s trx=%d\n",
		  rsl_chan_nr_str(info_act_cnf->chan_nr), trx->nr);

	rsl_tx_rf_rel_ack(lchan);

	/* During PDCH DEACT, this marks the deactivation of the PDTCH as
	 * requested by the PCU. Next up, we disconnect the TS completely and
	 * call back to cb_ts_disconnected(). See rsl_rx_dyn_pdch(). */
	if (lchan->ts->pchan == GSM_PCHAN_TCH_F_PDCH
	    && (lchan->ts->flags & TS_F_PDCH_DEACT_PENDING))
		bts_model_ts_disconnect(lchan->ts);

	return 0;
}

/* any L1 MPH_INFO confirm prim received from bts model */
static int l1sap_mph_info_cnf(struct gsm_bts_trx *trx,
	 struct osmo_phsap_prim *l1sap, struct mph_info_param *info)
{
	int rc = 0;

	switch (info->type) {
	case PRIM_INFO_ACTIVATE:
		rc = l1sap_info_act_cnf(trx, l1sap, &info->u.act_cnf);
		break;
	case PRIM_INFO_DEACTIVATE:
		rc = l1sap_info_rel_cnf(trx, l1sap, &info->u.act_cnf);
		break;
	default:
		LOGP(DL1C, LOGL_NOTICE, "unknown MPH_INFO cnf type %d\n",
			info->type);
		break;
	}

	return rc;
}

/*! handling for PDTCH loopback mode, used for BER testing
 *  \param[in] lchan logical channel on which we operate
 *  \param[in] rts_ind PH-RTS.ind from PHY which we process
 *  \param[out] msg Message buffer to which we write data
 *
 *  The function will fill \a msg, from which the caller can then
 *  subsequently build a PH-DATA.req */
static int lchan_pdtch_ph_rts_ind_loop(struct gsm_lchan *lchan,
					const struct ph_data_param *rts_ind,
					struct msgb *msg, const struct gsm_time *tm)
{
	struct msgb *loop_msg;
	uint8_t *p;

	/* de-queue response message (loopback) */
	loop_msg = msgb_dequeue_count(&lchan->dl_tch_queue, &lchan->dl_tch_queue_len);
	if (!loop_msg) {
		LOGPGT(DL1P, LOGL_NOTICE, tm, "%s: no looped PDTCH message, sending empty\n",
		     gsm_lchan_name(lchan));
		/* empty downlink message */
		p = msgb_put(msg, GSM_MACBLOCK_LEN);
		memset(p, 0, GSM_MACBLOCK_LEN);
	} else {
		LOGPGT(DL1P, LOGL_NOTICE, tm, "%s: looped PDTCH message of %u bytes\n",
		     gsm_lchan_name(lchan), msgb_l2len(loop_msg));
		/* copy over data from queued response message */
		p = msgb_put(msg, msgb_l2len(loop_msg));
		memcpy(p, msgb_l2(loop_msg), msgb_l2len(loop_msg));
		msgb_free(loop_msg);
	}
	return 0;
}

/* Check if given CCCH frame number is for a PCH or for an AGCH (this function is
 * only used internally, it is public to call it from unit-tests) */
int is_ccch_for_agch(struct gsm_bts_trx *trx, uint32_t fn) {
	/* Note: The number of available access grant channels is set by the
	 * parameter BS_AG_BLKS_RES via system information type 3. This SI is
	 * transferred to osmo-bts via RSL */
        return l1sap_fn2ccch_block(fn) < num_agch(trx, "PH-RTS-IND");
}

/* return the measured average of frame numbers that the RTS clock is running in advance */
int32_t bts_get_avg_fn_advance(const struct gsm_bts *bts)
{
	if (bts->fn_stats.avg_count == 0)
		return 0;
	return bts->fn_stats.avg256 / bts->fn_stats.avg_count;
}

static void l1sap_update_fnstats(struct gsm_bts *bts, uint32_t rts_fn)
{
	int32_t delta = GSM_TDMA_FN_SUB(rts_fn, bts->gsm_time.fn);

	if (delta < bts->fn_stats.min)
		bts->fn_stats.min = delta;
	if (delta > bts->fn_stats.max)
		bts->fn_stats.max = delta;

	if (bts->fn_stats.avg_count > bts->fn_stats.avg_window) {
		/* reset and start old average and new sample */
		bts->fn_stats.avg256 = (bts->fn_stats.avg256 / bts->fn_stats.avg_count) + delta;
		bts->fn_stats.avg_count = 2;
	} else {
		bts->fn_stats.avg256 += delta;
		bts->fn_stats.avg_count++;
	}
}

/* Common dequeueing function */
static inline struct msgb *lapdm_phsap_dequeue_msg(struct lapdm_entity *le)
{
	struct osmo_phsap_prim pp;
	if (lapdm_phsap_dequeue_prim(le, &pp) < 0)
		return NULL;
	return pp.oph.msg;
}

/* Special dequeueing function with FACCH repetition (3GPP TS 44.006, section 10) */
static inline struct msgb *lapdm_phsap_dequeue_msg_facch(struct gsm_lchan *lchan, struct lapdm_entity *le, uint32_t fn)
{
	struct osmo_phsap_prim pp;
	struct msgb *msg;

	/* Note: The repeated version of the FACCH block must be scheduled 8 or 9 bursts after the original
	 * transmission. see 3GPP TS 44.006, section 10.2 for a more detailed explaination. */
	if (lchan->rep_acch.dl_facch[0].msg && GSM_TDMA_FN_SUB(fn, lchan->rep_acch.dl_facch[0].fn) >= 8) {
		/* Re-use stored FACCH message buffer from SLOT #0 for repetition. */
		msg = lchan->rep_acch.dl_facch[0].msg;
		lchan->rep_acch.dl_facch[0].msg = NULL;
	} else if (lchan->rep_acch.dl_facch[1].msg && GSM_TDMA_FN_SUB(fn, lchan->rep_acch.dl_facch[1].fn) >= 8) {
		/* Re-use stored FACCH message buffer from SLOT #1 for repetition. */
		msg = lchan->rep_acch.dl_facch[1].msg;
		lchan->rep_acch.dl_facch[1].msg = NULL;
	} else {
		/* Fetch new FACCH from queue ... */
		if (lapdm_phsap_dequeue_prim(le, &pp) < 0)
			return NULL;
		msg = pp.oph.msg;

		/* Check if the LAPDm frame is a command frame,
		 * see also: 3GPP TS 04.06 section 3.2 and 3.3.2.
		 * If the MS explicitly indicated that repeated ACCH is
		 * supported, than all FACCH frames may be repeated
		 * see also: 3GPP TS 44.006, section 10.3). */
		if (!(lchan->rep_acch_cap.dl_facch_all || msg->data[0] & 0x02))
			return msg;

		/* ... and store the message buffer for repetition. */
		if (lchan->rep_acch.dl_facch[0].msg == NULL) {
			lchan->rep_acch.dl_facch[0].msg = msgb_copy(msg, "rep_facch_0");
			lchan->rep_acch.dl_facch[0].fn = fn;
		} else if (lchan->rep_acch.dl_facch[1].msg == NULL) {
			lchan->rep_acch.dl_facch[1].msg = msgb_copy(msg, "rep_facch_1");
			lchan->rep_acch.dl_facch[1].fn = fn;
		} else {
			/* By definition 3GPP TS 05.02 does not allow more than two (for TCH/H only one) FACCH blocks
			 * to be transmitted simultaniously. */
			OSMO_ASSERT(false);
		}
	}

	return msg;
}

/* Special dequeueing function with SACCH repetition (3GPP TS 44.006, section 11) */
static inline struct msgb *lapdm_phsap_dequeue_msg_sacch(struct gsm_lchan *lchan, struct lapdm_entity *le)
{
	struct osmo_phsap_prim pp;
	struct msgb *msg;
	uint8_t sapi;

	/* Note: When the MS disables SACCH repetition, we still must collect
	 * possible candidates in order to have one ready in case the MS enables
	 * SACCH repetition. */

	if (lchan->rep_acch.dl_sacch_msg) {
		if (lchan->meas.l1_info.srr_sro == 0) {
			/* Toss previous repetition candidate */
			msgb_free(lchan->rep_acch.dl_sacch_msg);
			lchan->rep_acch.dl_sacch_msg = NULL;
		} else {
			/* Use previous repetition candidate */
			msg = lchan->rep_acch.dl_sacch_msg;
			lchan->rep_acch.dl_sacch_msg = NULL;
			return msg;
		}
	}

	/* Fetch new repetition candidate from queue */
	if (lapdm_phsap_dequeue_prim(le, &pp) < 0)
		return NULL;
	msg = pp.oph.msg;
	sapi = (msg->data[0] >> 2) & 0x07;

	/* Only LAPDm frames for SAPI 0 may become a repetition
	 * candidate. */
	if (sapi == 0)
		lchan->rep_acch.dl_sacch_msg = msgb_copy(msg, "rep_sacch");

	return msg;
}

/* PH-RTS-IND prim received from bts model */
static int l1sap_ph_rts_ind(struct gsm_bts_trx *trx,
	struct osmo_phsap_prim *l1sap, struct ph_data_param *rts_ind)
{
	struct msgb *msg = l1sap->oph.msg;
	struct gsm_time g_time;
	struct gsm_lchan *lchan;
	uint8_t chan_nr, link_id;
	uint8_t tn;
	uint32_t fn;
	uint8_t *p = NULL;
	uint8_t *si;
	struct lapdm_entity *le;
	struct msgb *pp_msg;
	bool dtxd_facch = false;
	int rc;
	int is_ag_res;

	chan_nr = rts_ind->chan_nr;
	link_id = rts_ind->link_id;
	fn = rts_ind->fn;
	tn = L1SAP_CHAN2TS(chan_nr);

	gsm_fn2gsmtime(&g_time, fn);

	DEBUGPGT(DL1P, &g_time, "Rx PH-RTS.ind chan_nr=%s link_id=0x%02xd\n", rsl_chan_nr_str(chan_nr), link_id);

	l1sap_update_fnstats(trx->bts, fn);

	/* reuse PH-RTS.ind for PH-DATA.req */
	if (!msg) {
		LOGPGT(DL1P, LOGL_FATAL, &g_time, "RTS without msg to be reused. Please fix!\n");
		abort();
	}
	msgb_trim(msg, sizeof(*l1sap));
	osmo_prim_init(&l1sap->oph, SAP_GSM_PH, PRIM_PH_DATA, PRIM_OP_REQUEST,
		msg);
	msg->l2h = msg->l1h + sizeof(*l1sap);

	if (ts_is_pdch(&trx->ts[tn])) {
		lchan = get_active_lchan_by_chan_nr(trx, chan_nr);
		if (lchan && lchan->loopback) {
			if (!L1SAP_IS_PTCCH(rts_ind->fn))
				lchan_pdtch_ph_rts_ind_loop(lchan, rts_ind, msg, &g_time);
			/* continue below like for SACCH/FACCH/... */
		} else {
			/* forward RTS.ind to PCU */
			if (L1SAP_IS_PTCCH(rts_ind->fn)) {
				pcu_tx_rts_req(&trx->ts[tn], 1, fn, trx->arfcn,
						L1SAP_FN2PTCCHBLOCK(fn));
			} else {
				pcu_tx_rts_req(&trx->ts[tn], 0, fn, trx->arfcn,
						L1SAP_FN2MACBLOCK(fn));
			}
			/* return early, PCU takes care of rest */
			return 0;
		}
	} else if (L1SAP_IS_CHAN_BCCH(chan_nr)) {
		p = msgb_put(msg, GSM_MACBLOCK_LEN);
		/* get them from bts->si_buf[] */
		si = bts_sysinfo_get(trx->bts, &g_time);
		if (si)
			memcpy(p, si, GSM_MACBLOCK_LEN);
		else
			memcpy(p, fill_frame, GSM_MACBLOCK_LEN);
	} else if (L1SAP_IS_CHAN_CBCH(chan_nr)) {
		p = msgb_put(msg, GSM_MACBLOCK_LEN);
		bts_cbch_get(trx->bts, p, &g_time);
	} else if (!(chan_nr & 0x80)) { /* only TCH/F, TCH/H, SDCCH/4 and SDCCH/8 have C5 bit cleared */
		lchan = get_active_lchan_by_chan_nr(trx, chan_nr);
		if (!lchan) {
			LOGPGT(DL1P, LOGL_ERROR, &g_time, "No lchan for PH-RTS.ind (chan_nr=%s)\n",
			       rsl_chan_nr_str(chan_nr));
			return 0;
		}
		if (lchan->pending_rel_ind_msg) {
			LOGPGT(DRSL, LOGL_INFO, &g_time,
			       "%s Forward RLL RELease INDication to the BSC\n",
			       gsm_lchan_name(lchan));
			abis_bts_rsl_sendmsg(lchan->pending_rel_ind_msg);
			lchan->pending_rel_ind_msg = NULL;
		}
		if (L1SAP_IS_LINK_SACCH(link_id)) {
			p = msgb_put(msg, GSM_MACBLOCK_LEN);
			/* L1-header, if not set/modified by layer 1 */
			p[0] = lchan->ms_power_ctrl.current;
			if (lchan->rep_acch.ul_sacch_active)
				p[0] |= 0x40; /* See also: 3GPP TS 44.004, section 7.1 */
			p[1] = lchan->ta_ctrl.current;
			le = &lchan->lapdm_ch.lapdm_acch;
			if (lchan->rep_acch_cap.dl_sacch) {
				/* Check if MS requests SACCH repetition and update state accordingly */
				if (lchan->meas.l1_info.srr_sro) {
					if (lchan->rep_acch.dl_sacch_active == false)
						LOGPLCHAN(lchan, DL1P, LOGL_DEBUG, "DL-SACCH repetition: inactive => active\n");
					lchan->rep_acch.dl_sacch_active = true;
				} else {
					if (lchan->rep_acch.dl_sacch_active == true)
						LOGPLCHAN(lchan, DL1P, LOGL_DEBUG, "DL-SACCH repetition: active => inactive\n");
					lchan->rep_acch.dl_sacch_active = false;
				}
				pp_msg = lapdm_phsap_dequeue_msg_sacch(lchan, le);
			} else {
				pp_msg = lapdm_phsap_dequeue_msg(le);
			}
		} else {
			if (lchan->ts->trx->bts->dtxd)
				dtxd_facch = true;
			le = &lchan->lapdm_ch.lapdm_dcch;
			if (lchan->rep_acch.dl_facch_active && lchan->rsl_cmode != RSL_CMOD_SPD_SIGN)
				pp_msg = lapdm_phsap_dequeue_msg_facch(lchan, le, fn);
			else
				pp_msg = lapdm_phsap_dequeue_msg(le);
		}
		if (!pp_msg) {
			if (L1SAP_IS_LINK_SACCH(link_id)) {
				/* No SACCH data from LAPDM pending, send SACCH filling */
				uint8_t *si = lchan_sacch_get(lchan);
				if (si) {
					/* The +2 is empty space where the DSP inserts the L1 hdr */
					memcpy(p + 2, si, GSM_MACBLOCK_LEN - 2);
				} else
					memcpy(p + 2, fill_frame, GSM_MACBLOCK_LEN - 2);
			} else if (L1SAP_IS_CHAN_SDCCH4(chan_nr) || L1SAP_IS_CHAN_SDCCH8(chan_nr) ||
				   (lchan->rsl_cmode == RSL_CMOD_SPD_SIGN && !lchan->ts->trx->bts->dtxd)) {
				/*
				 * SDCCH or TCH in signalling mode without DTX.
				 *
				 * Send fill frame according to GSM 05.08, section 8.3: "On the SDCCH and on the
				 * half rate speech traffic channel in signalling only mode DTX is not allowed.
				 * In these cases and during signalling on the TCH when DTX is not used, the same
				 * L2 fill frame shall be transmitted in case there is nothing else to transmit."
				 */
				p = msgb_put(msg, GSM_MACBLOCK_LEN);
				memcpy(p, fill_frame, GSM_MACBLOCK_LEN);
			} /* else the message remains empty, so TCH frames are sent */
		} else {
			/* The +2 is empty space where the DSP inserts the L1 hdr */
			if (L1SAP_IS_LINK_SACCH(link_id))
				memcpy(p + 2, pp_msg->data + 2, GSM_MACBLOCK_LEN - 2);
			else {
				p = msgb_put(msg, GSM_MACBLOCK_LEN);
				memcpy(p, pp_msg->data, GSM_MACBLOCK_LEN);
				/* check if it is a RR CIPH MODE CMD. if yes, enable RX ciphering */
				check_for_ciph_cmd(pp_msg, lchan, chan_nr);
				if (dtxd_facch)
					dtx_dispatch(lchan, E_FACCH);
			}
			msgb_free(pp_msg);
		}
	} else if (L1SAP_IS_CHAN_AGCH_PCH(chan_nr)) {
		p = msgb_put(msg, GSM_MACBLOCK_LEN);
		is_ag_res = is_ccch_for_agch(trx, fn);
		rc = bts_ccch_copy_msg(trx->bts, p, &g_time, is_ag_res);
		if (rc <= 0)
			memcpy(p, fill_frame, GSM_MACBLOCK_LEN);
	}

	DEBUGPGT(DL1P, &g_time, "Tx PH-DATA.req chan_nr=%s link_id=0x%02x\n", rsl_chan_nr_str(chan_nr), link_id);

	l1sap_down(trx, l1sap);

	/* don't free, because we forwarded data */
	return 1;
}

static bool rtppayload_is_octet_aligned(const uint8_t *rtp_pl, uint8_t payload_len)
{
	/*
	 * Logic: If 1st bit padding is not zero, packet is either:
	 * - bandwidth-efficient AMR payload.
	 * - malformed packet.
	 * However, Bandwidth-efficient AMR 4,75 frame last in payload(F=0, FT=0)
	 * with 4th,5ht,6th AMR payload to 0 matches padding==0.
	 * Furthermore, both AMR 4,75 bw-efficient and octet alignment are 14 bytes long (AMR 4,75 encodes 95b):
	 * bw-efficient: 95b, + 4b hdr + 6b ToC = 105b, + padding = 112b = 14B.
	 * octet-aligned: 1B hdr + 1B ToC + 95b = 111b, + padding = 112b = 14B.
	 * We cannot use other fields to match since they are inside the AMR
	 * payload bits which are unknown.
	 * As a result, this function may return false positive (true) for some AMR
	 * 4,75 AMR frames, but given the length, CMR and FT read is the same as a
	 * consequence, the damage in here is harmless other than being unable to
	 * decode the audio at the other side.
	 */
	#define AMR_PADDING1(rtp_pl) (rtp_pl[0] & 0x0f)
	#define AMR_PADDING2(rtp_pl) (rtp_pl[1] & 0x03)

	if (payload_len < 2 || AMR_PADDING1(rtp_pl) || AMR_PADDING2(rtp_pl))
		return false;

	return true;
}

static bool rtppayload_is_valid(struct gsm_lchan *lchan, struct msgb *resp_msg)
{
	/* Avoid sending bw-efficient AMR to lower layers, most bts models
	 * don't support it. */
	if (lchan->tch_mode == GSM48_CMODE_SPEECH_AMR &&
		!rtppayload_is_octet_aligned(resp_msg->data, resp_msg->len)) {
		LOGPLCHAN(lchan, DL1P, LOGL_NOTICE,
			  "RTP->L1: Dropping unexpected AMR encoding (bw-efficient?) %s\n",
			  osmo_hexdump(resp_msg->data, resp_msg->len));
		return false;
	}
	return true;
}

/* TCH-RTS-IND prim received from bts model */
static int l1sap_tch_rts_ind(struct gsm_bts_trx *trx,
	struct osmo_phsap_prim *l1sap, struct ph_tch_param *rts_ind)
{
	struct msgb *resp_msg;
	struct osmo_phsap_prim *resp_l1sap, empty_l1sap;
	struct gsm_time g_time;
	struct gsm_lchan *lchan;
	uint8_t chan_nr, marker = 0;
	uint32_t fn;

	chan_nr = rts_ind->chan_nr;
	fn = rts_ind->fn;

	gsm_fn2gsmtime(&g_time, fn);

	DEBUGPGT(DL1P, &g_time, "Rx TCH-RTS.ind chan_nr=%s\n", rsl_chan_nr_str(chan_nr));

	lchan = get_active_lchan_by_chan_nr(trx, chan_nr);
	if (!lchan) {
		LOGPGT(DL1P, LOGL_ERROR, &g_time, "No lchan for PH-RTS.ind (chan_nr=%s)\n", rsl_chan_nr_str(chan_nr));
		return 0;
	}

	if (!lchan->loopback && lchan->abis_ip.rtp_socket) {
		osmo_rtp_socket_poll(lchan->abis_ip.rtp_socket);
		/* FIXME: we _assume_ that we never miss TDMA
		 * frames and that we always get to this point
		 * for every to-be-transmitted voice frame.  A
		 * better solution would be to compute
		 * rx_user_ts based on how many TDMA frames have
		 * elapsed since the last call */
		lchan->abis_ip.rtp_socket->rx_user_ts += GSM_RTP_DURATION;
	}
	/* get a msgb from the dl_tx_queue */
	resp_msg = msgb_dequeue_count(&lchan->dl_tch_queue, &lchan->dl_tch_queue_len);
	if (!resp_msg) {
		DEBUGPGT(DL1P, &g_time, "%s DL TCH Tx queue underrun\n", gsm_lchan_name(lchan));
		resp_l1sap = &empty_l1sap;
	} else if (!rtppayload_is_valid(lchan, resp_msg)) {
		msgb_free(resp_msg);
		resp_msg = NULL;
		resp_l1sap = &empty_l1sap;
	} else {
		/* Obtain RTP header Marker bit from control buffer */
		marker = rtpmsg_marker_bit(resp_msg);

		resp_msg->l2h = resp_msg->data;
		msgb_push(resp_msg, sizeof(*resp_l1sap));
		resp_msg->l1h = resp_msg->data;
		resp_l1sap = msgb_l1sap_prim(resp_msg);
	}

	memset(resp_l1sap, 0, sizeof(*resp_l1sap));
	osmo_prim_init(&resp_l1sap->oph, SAP_GSM_PH, PRIM_TCH, PRIM_OP_REQUEST,
		resp_msg);
	resp_l1sap->u.tch.chan_nr = chan_nr;
	resp_l1sap->u.tch.fn = fn;
	resp_l1sap->u.tch.marker = marker;

	DEBUGPGT(DL1P, &g_time, "Tx TCH.req chan_nr=%s\n", rsl_chan_nr_str(chan_nr));

	l1sap_down(trx, resp_l1sap);

	return 0;
}

/* process radio link timeout counter S. Follows TS 05.08 Section 5.2
 * "MS Procedure" as the "BSS Procedure [...] shall be determined by the
 * network operator." */
static void radio_link_timeout(struct gsm_lchan *lchan, bool bad_frame)
{
	struct gsm_bts *bts = lchan->ts->trx->bts;

	/* Bypass radio link timeout if set to -1 */
	if (bts->radio_link_timeout.current < 0)
		return;

	/* if link loss criterion already reached */
	if (lchan->s == 0) {
		LOGPLCHAN(lchan, DMEAS, LOGL_DEBUG,
			  "radio link timeout counter S is already 0\n");
		return;
	}

	if (bad_frame) {
		LOGPLCHAN(lchan, DMEAS, LOGL_DEBUG,
			  "decreasing radio link timeout counter S=%d -> %d\n",
			  lchan->s, lchan->s - 1);
		lchan->s--; /* count down radio link counter S */
		if (lchan->s == 0) {
			LOGPLCHAN(lchan, DMEAS, LOGL_NOTICE,
				  "radio link timeout counter S reached zero, "
				  "dropping connection\n");
			rsl_tx_conn_fail(lchan, RSL_ERR_RADIO_LINK_FAIL);
		}
		return;
	}

	if (lchan->s < bts->radio_link_timeout.current) {
		/* count up radio link counter S */
		int s = lchan->s + 2;
		if (s > bts->radio_link_timeout.current)
			s = bts->radio_link_timeout.current;
		LOGPLCHAN(lchan, DMEAS, LOGL_DEBUG,
			  "increasing radio link timeout counter S=%d -> %d\n",
			  lchan->s, s);
		lchan->s = s;
	}
}

static inline int check_for_first_ciphrd(struct gsm_lchan *lchan,
					  uint8_t *data, int len)
{
	uint8_t n_r;

	/* if this is the first valid message after enabling Rx
	 * decryption, we have to enable Tx encryption */
	if (lchan->ciph_state != LCHAN_CIPH_RX_CONF)
		return 0;

	/* HACK: check if it's an I frame, in order to
	 * ignore some still buffered/queued UI frames received
	 * before decryption was enabled */
	if (data[0] != 0x01)
		return 0;

	if ((data[1] & 0x01) != 0)
		return 0;

	n_r = data[1] >> 5;
	if (lchan->ciph_ns != n_r)
		return 0;

	return 1;
}

/* public helper for the test */
int bts_check_for_first_ciphrd(struct gsm_lchan *lchan,
				uint8_t *data, int len)
{
	return check_for_first_ciphrd(lchan, data, len);
}

/* Decide if repeated UL-SACCH should be applied or not. If the BER level, of
 * the received SACCH blocks rises above a certain threshold UL-SACCH
 * repetition is enabled */
static void repeated_ul_sacch_active_decision(struct gsm_lchan *lchan,
					      uint16_t ber10k)
{
	uint16_t upper = 0;
	uint16_t lower = 0;
	bool prev_repeated_ul_sacch_active = lchan->rep_acch.ul_sacch_active;

	/* This is an optimization so that we exit as quickly as possible if
	 * there are no uplink SACCH repetition capabilities present.
	 * However If the repeated UL-SACCH capabilities vanish for whatever
	 * reason, we must be sure that UL-SACCH repetition is disabled. */
	if (!lchan->rep_acch_cap.ul_sacch) {
		lchan->rep_acch.ul_sacch_active = false;
		goto out;
	}

	/* Threshold disabled (repetition is always on) */
	if (lchan->rep_acch_cap.rxqual == 0) {
		lchan->rep_acch.ul_sacch_active = true;
		goto out;
	}

	/* convert from RXQUAL value to ber10k value.
	 * see also GSM 05.08, section 8.2.4 (first table, without frame */
	static const uint16_t ber10k_by_rxqual_upper[] =
	    { 0, 20, 40, 80, 160, 320, 640, 1280 };
	static const uint16_t ber10k_by_rxqual_lower[] =
	    { 0, 0, 0, 20, 40, 80, 160, 320 };
	/* Note: The values in the upper vector are taken from the left side
	 * of the table in GSM 05.08, section 8.2.4. The lower vector is just
	 * the upper vector shifted by 2. */

	upper = ber10k_by_rxqual_upper[lchan->rep_acch_cap.rxqual];
	lower = ber10k_by_rxqual_lower[lchan->rep_acch_cap.rxqual];

	/* If upper/rxqual == 0, then repeated UL-SACCH is always on */
	if (ber10k >= upper)
		lchan->rep_acch.ul_sacch_active = true;
	else if (ber10k <= lower)
		lchan->rep_acch.ul_sacch_active = false;

out:
	if (lchan->rep_acch.ul_sacch_active == prev_repeated_ul_sacch_active)
		return;
	if (lchan->rep_acch.ul_sacch_active)
		LOGPLCHAN(lchan, DL1P, LOGL_DEBUG, "UL-SACCH repetition: inactive => active\n");
	else
		LOGPLCHAN(lchan, DL1P, LOGL_DEBUG, "UL-SACCH repetition: active => inactive\n");
}

/* DATA received from bts model */
static int l1sap_ph_data_ind(struct gsm_bts_trx *trx,
	 struct osmo_phsap_prim *l1sap, struct ph_data_param *data_ind)
{
	struct msgb *msg = l1sap->oph.msg;
	struct gsm_time g_time;
	struct gsm_lchan *lchan;
	struct lapdm_entity *le;
	uint8_t *data = msg->l2h;
	int len = msgb_l2len(msg);
	uint8_t chan_nr, link_id;
	uint8_t tn;
	uint32_t fn;
	enum osmo_ph_pres_info_type pr_info = data_ind->pdch_presence_info;

	chan_nr = data_ind->chan_nr;
	link_id = data_ind->link_id;
	fn = data_ind->fn;
	tn = L1SAP_CHAN2TS(chan_nr);

	gsm_fn2gsmtime(&g_time, fn);

	DEBUGPGT(DL1P, &g_time, "Rx PH-DATA.ind chan_nr=%s link_id=0x%02x len=%d\n",
		 rsl_chan_nr_str(chan_nr), link_id, len);

	if (ts_is_pdch(&trx->ts[tn])) {
		lchan = get_lchan_by_chan_nr(trx, chan_nr);
		if (!lchan)
			LOGPGT(DL1P, LOGL_ERROR, &g_time, "No lchan for chan_nr=%s\n", rsl_chan_nr_str(chan_nr));
		if (lchan && lchan->loopback) {
			/* we are in loopback mode (for BER testing)
			 * mode and need to enqeue the frame to be
			 * returned in downlink */
			lchan_dl_tch_queue_enqueue(lchan, msg, 1);

			/* Return 1 to signal that we're still using msg
			 * and it should not be freed */
			return 1;
		}

		/* There can be no DATA.ind on PTCCH/U (rather RACH.ind instead), but some
		 * BTS models with buggy implementation may still be sending them to us. */
		if (L1SAP_IS_PTCCH(fn)) {
			LOGPGT(DL1P, LOGL_NOTICE, &g_time, "There can be no DATA.ind on PTCCH/U. "
			       "This is probably a bug of the BTS model you're using, please fix!\n");
			return -EINVAL;
		}

		/* Drop all data from incomplete UL block */
		if (pr_info != PRES_INFO_BOTH)
			len = 0;

		/* PDTCH / PACCH frame handling */
		pcu_tx_data_ind(&trx->ts[tn], PCU_IF_SAPI_PDTCH, fn, trx->arfcn,
				L1SAP_FN2MACBLOCK(fn), data, len, data_ind->rssi, data_ind->ber10k,
				data_ind->ta_offs_256bits/64, data_ind->lqual_cb);
		return 0;
	}

	lchan = get_active_lchan_by_chan_nr(trx, chan_nr);
	if (!lchan) {
		LOGPGT(DL1P, LOGL_ERROR, &g_time, "No lchan for chan_nr=%s\n", rsl_chan_nr_str(chan_nr));
		return 0;
	}

	/* The ph_data_param contained in the l1sap primitive may contain
	 * measurement data. If this data is present, forward it for
	 * processing */
	if (bts_internal_flag_get(trx->bts, BTS_INTERNAL_FLAG_MEAS_PAYLOAD_COMB))
		process_l1sap_meas_data(lchan, l1sap, PRIM_PH_DATA);

	if (L1SAP_IS_LINK_SACCH(link_id)) {
		repeated_ul_sacch_active_decision(lchan, data_ind->ber10k);

		/* Radio Link Timeout counter */
		if (len == 0) {
			LOGPGT(DL1P, LOGL_INFO, &g_time, "%s Lost SACCH block\n",
			       gsm_lchan_name(lchan));
			radio_link_timeout(lchan, true);
		} else {
			radio_link_timeout(lchan, false);
		}

		/* Trigger the measurement reporting/processing logic */
		lchan_meas_handle_sacch(lchan, msg);
	}

	/* bad frame */
	if (len == 0)
		return -EINVAL;

	/* report first valid received frame to handover process */
	if (lchan->ho.active == HANDOVER_WAIT_FRAME)
		handover_frame(lchan);

	if (L1SAP_IS_LINK_SACCH(link_id))
		le = &lchan->lapdm_ch.lapdm_acch;
	else
		le = &lchan->lapdm_ch.lapdm_dcch;

	if (check_for_first_ciphrd(lchan, data, len))
		l1sap_tx_ciph_req(lchan->ts->trx, chan_nr, 1, 0);

	/* SDCCH, SACCH and FACCH all go to LAPDm */
	msgb_pull_to_l2(msg);
	lapdm_phsap_up(&l1sap->oph, le);

	/* don't free, because we forwarded data */
	return 1;
}

/* TCH received from bts model */
static int l1sap_tch_ind(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap,
	struct ph_tch_param *tch_ind)
{
	struct gsm_bts *bts = trx->bts;
	struct msgb *msg = l1sap->oph.msg;
	struct gsm_time g_time;
	struct gsm_lchan *lchan;
	uint8_t  chan_nr;
	uint32_t fn;

	chan_nr = tch_ind->chan_nr;
	fn = tch_ind->fn;

	gsm_fn2gsmtime(&g_time, fn);

	LOGPGT(DL1P, LOGL_DEBUG, &g_time, "Rx TCH.ind chan_nr=%s\n", rsl_chan_nr_str(chan_nr));

	lchan = get_active_lchan_by_chan_nr(trx, chan_nr);
	if (!lchan) {
		LOGPGT(DL1P, LOGL_ERROR, &g_time, "No lchan for TCH.ind (chan_nr=%s)\n", rsl_chan_nr_str(chan_nr));
		return 0;
	}

	/* The ph_tch_param contained in the l1sap primitive may contain
	 * measurement data. If this data is present, forward it for
	 * processing */
	if (bts_internal_flag_get(trx->bts, BTS_INTERNAL_FLAG_MEAS_PAYLOAD_COMB))
		process_l1sap_meas_data(lchan, l1sap, PRIM_TCH);

	msgb_pull_to_l2(msg);

	/* Low level layers always call us when TCH content is expected, even if
	 * the content is not available due to decoding issues. Content not
	 * available is expected as empty payload. We also check if quality is
	 * good enough. */
	if (msg->len && tch_ind->lqual_cb >= bts->min_qual_norm) {
		/* hand msg to RTP code for transmission */
		if (lchan->abis_ip.osmux.use) {
			lchan_osmux_send_frame(lchan, msg->data, msg->len,
					       fn_ms_adj(fn, lchan), lchan->rtp_tx_marker);
		} else if (lchan->abis_ip.rtp_socket) {
			osmo_rtp_send_frame_ext(lchan->abis_ip.rtp_socket,
				msg->data, msg->len, fn_ms_adj(fn, lchan), lchan->rtp_tx_marker);
		}
		/* if loopback is enabled, also queue received RTP data */
		if (lchan->loopback) {
			/* add new frame to queue, make sure the queue doesn't get too long */
			lchan_dl_tch_queue_enqueue(lchan, msg, 1);
			/* Return 1 to signal that we're still using msg and it should not be freed */
			return 1;
		}
		/* Only clear the marker bit once we have sent a RTP packet with it */
		lchan->rtp_tx_marker = false;
	} else {
		DEBUGPGT(DRTP, &g_time, "Skipping RTP frame with lost payload (chan_nr=0x%02x)\n",
			 chan_nr);
		if (lchan->abis_ip.osmux.use)
			lchan_osmux_skipped_frame(lchan, fn_ms_adj(fn, lchan));
		else if (lchan->abis_ip.rtp_socket)
			osmo_rtp_skipped_frame(lchan->abis_ip.rtp_socket, fn_ms_adj(fn, lchan));
		lchan->rtp_tx_marker = true;
	}

	lchan->tch.last_fn = fn;
	return 0;
}

#define RACH_MIN_TOA256 -2 * 256

static bool rach_pass_filter(struct ph_rach_ind_param *rach_ind, struct gsm_bts *bts,
			     const char *chan_name)
{
	int16_t toa256 = rach_ind->acc_delay_256bits;

	/* Check for RACH exceeding BER threshold (ghost RACH) */
	if (rach_ind->ber10k > bts->max_ber10k_rach) {
		LOGPFN(DL1C, LOGL_DEBUG, rach_ind->fn, "Ignoring an Access Burst on %s: "
			"BER10k(%u) > BER10k_MAX(%u)\n", chan_name,
			rach_ind->ber10k, bts->max_ber10k_rach);
		return false;
	}

	/**
	 * Make sure that ToA (Timing of Arrival) is acceptable.
	 * We allow early arrival up to 2 symbols, and delay
	 * according to maximal allowed Timing Advance value.
	 */
	if (toa256 < RACH_MIN_TOA256 || toa256 > bts->max_ta * 256) {
		LOGPFN(DL1C, LOGL_DEBUG, rach_ind->fn, "Ignoring an Access Burst on %s: "
			"ToA(%d) exceeds the allowed range (%d..%d)\n", chan_name,
			toa256, RACH_MIN_TOA256, bts->max_ta * 256);
		return false;
	}

	/* Link quality defined by C/I (Carrier-to-Interference ratio) */
	if (rach_ind->lqual_cb < bts->min_qual_rach) {
		LOGPFN(DL1C, LOGL_DEBUG, rach_ind->fn, "Ignoring an Access Burst on %s: "
			"link quality (%d) below the minimum (%d)\n", chan_name,
			rach_ind->lqual_cb, bts->min_qual_rach);
		return false;
	}

	return true;
}

/* Special case where handover RACH is detected */
static int l1sap_handover_rach(struct gsm_bts_trx *trx, struct ph_rach_ind_param *rach_ind)
{
	/* Filter out noise / interference / ghosts */
	if (!rach_pass_filter(rach_ind, trx->bts, "handover")) {
		rate_ctr_inc2(trx->bts->ctrs, BTS_CTR_RACH_DROP);
		return 0;
	}

	handover_rach(get_lchan_by_chan_nr(trx, rach_ind->chan_nr),
		rach_ind->ra, rach_ind->acc_delay);

	/* must return 0, so in case of msg at l1sap, it will be freed */
	return 0;
}

/* Special case for Access Bursts on PDTCH/U or PTCCH/U */
static int l1sap_pdch_rach(struct gsm_bts_trx *trx, struct ph_rach_ind_param *rach_ind)
{
	/* Filter out noise / interference / ghosts */
	if (!rach_pass_filter(rach_ind, trx->bts, "PDCH"))
		return -EAGAIN;

	/* PTCCH/U (Packet Timing Advance Control Channel) */
	if (L1SAP_IS_PTCCH(rach_ind->fn)) {
		LOGPFN(DL1P, LOGL_DEBUG, rach_ind->fn,
		       /* TODO: calculate and print Timing Advance Index */
		       "Access Burst for continuous Timing Advance control (toa256=%d)\n",
		       rach_ind->acc_delay_256bits);

		/* QTA: Timing Advance in units of 1/4 of a symbol */
		pcu_tx_rach_ind(trx->bts->nr, trx->nr, rach_ind->chan_nr & 0x07,
				rach_ind->acc_delay_256bits >> 6,
				rach_ind->ra, rach_ind->fn, rach_ind->is_11bit,
				rach_ind->burst_type, PCU_IF_SAPI_PTCCH);
		return 0;
	} else { /* The MS may acknowledge DL data by 4 consequent Access Bursts */
		LOGPFN(DL1P, LOGL_NOTICE, rach_ind->fn,
		       "Access Bursts on PDTCH/U are not (yet) supported\n");
		return -ENOTSUP;
	}
}

/* RACH received from bts model */
static int l1sap_ph_rach_ind(struct gsm_bts_trx *trx,
	 struct osmo_phsap_prim *l1sap, struct ph_rach_ind_param *rach_ind)
{
	struct gsm_bts *bts = trx->bts;
	struct lapdm_channel *lc;

	DEBUGPFN(DL1P, rach_ind->fn, "Rx PH-RA.ind\n");

	/* Check the origin of an Access Burst */
	switch (rach_ind->chan_nr & 0xf8) {
	case RSL_CHAN_RACH:
		/* CS or PS RACH, to be handled in this function */
		break;
	case RSL_CHAN_OSMO_PDCH:
		/* TODO: do we need to count Access Bursts on PDCH? */
		return l1sap_pdch_rach(trx, rach_ind);
	default:
		rate_ctr_inc2(trx->bts->ctrs, BTS_CTR_RACH_HO);
		return l1sap_handover_rach(trx, rach_ind);
	}

	rate_ctr_inc2(trx->bts->ctrs, BTS_CTR_RACH_RCVD);

	/* increment number of busy RACH slots, if required */
	if (rach_ind->rssi >= bts->load.rach.busy_thresh)
		bts->load.rach.busy++;

	/* Filter out noise / interference / ghosts */
	if (!rach_pass_filter(rach_ind, bts, "CCCH")) {
		rate_ctr_inc2(trx->bts->ctrs, BTS_CTR_RACH_DROP);
		return 0;
	}

	/* increment number of RACH slots with valid non-handover RACH burst */
	bts->load.rach.access++;

	lc = &trx->ts[0].lchan[CCCH_LCHAN].lapdm_ch;

	/* According to 3GPP TS 48.058 § 9.3.17 Access Delay is expressed same way as TA (number of symbols) */
	set_ms_to_data(get_lchan_by_chan_nr(trx, rach_ind->chan_nr),
		rach_ind->acc_delay, false);

	/* check for packet access */
	if ((trx == bts->c0 && L1SAP_IS_PACKET_RACH(rach_ind->ra)) ||
		(trx == bts->c0 && rach_ind->is_11bit)) {
		rate_ctr_inc2(trx->bts->ctrs, BTS_CTR_RACH_PS);

		LOGPFN(DL1P, LOGL_INFO, rach_ind->fn, "RACH for packet access (toa=%d, ra=%d)\n",
			rach_ind->acc_delay, rach_ind->ra);

		/* QTA: Timing Advance in units of 1/4 of a symbol */
		pcu_tx_rach_ind(bts->nr, trx->nr, rach_ind->chan_nr & 0x07,
			rach_ind->acc_delay_256bits >> 6,
			rach_ind->ra, rach_ind->fn, rach_ind->is_11bit,
			rach_ind->burst_type, PCU_IF_SAPI_RACH);
		return 0;
	}

	LOGPFN(DL1P, LOGL_INFO, rach_ind->fn, "RACH for RR access (toa=%d, ra=%d)\n",
		rach_ind->acc_delay, rach_ind->ra);
	rate_ctr_inc2(trx->bts->ctrs, BTS_CTR_RACH_CS);
	lapdm_phsap_up(&l1sap->oph, &lc->lapdm_dcch);

	return 0;
}

/* Process any L1 prim received from bts model.
 *
 * This function takes ownership of the msgb.
 * If l1sap contains a msgb, it assumes that msgb->l2h was set by lower layer.
 */
int l1sap_up(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap)
{
	struct msgb *msg = l1sap->oph.msg;
	int rc = 0;

	switch (OSMO_PRIM_HDR(&l1sap->oph)) {
	case OSMO_PRIM(PRIM_MPH_INFO, PRIM_OP_INDICATION):
		rc = l1sap_mph_info_ind(trx, l1sap, &l1sap->u.info);
		break;
	case OSMO_PRIM(PRIM_MPH_INFO, PRIM_OP_CONFIRM):
		rc = l1sap_mph_info_cnf(trx, l1sap, &l1sap->u.info);
		break;
	case OSMO_PRIM(PRIM_PH_RTS, PRIM_OP_INDICATION):
		rc = l1sap_ph_rts_ind(trx, l1sap, &l1sap->u.data);
		break;
	case OSMO_PRIM(PRIM_TCH_RTS, PRIM_OP_INDICATION):
		rc = l1sap_tch_rts_ind(trx, l1sap, &l1sap->u.tch);
		break;
	case OSMO_PRIM(PRIM_PH_DATA, PRIM_OP_INDICATION):
		to_gsmtap(trx, l1sap);
		rc = l1sap_ph_data_ind(trx, l1sap, &l1sap->u.data);
		break;
	case OSMO_PRIM(PRIM_TCH, PRIM_OP_INDICATION):
		rc = l1sap_tch_ind(trx, l1sap, &l1sap->u.tch);
		break;
	case OSMO_PRIM(PRIM_PH_RACH, PRIM_OP_INDICATION):
		to_gsmtap(trx, l1sap);
		rc = l1sap_ph_rach_ind(trx, l1sap, &l1sap->u.rach_ind);
		break;
	default:
		LOGP(DL1P, LOGL_NOTICE, "unknown prim %d op %d\n",
			l1sap->oph.primitive, l1sap->oph.operation);
		oml_tx_failure_event_rep(&trx->mo, NM_SEVER_MAJOR, OSMO_EVT_MAJ_UKWN_MSG,
					 "unknown prim %d op %d",
					 l1sap->oph.primitive,
					 l1sap->oph.operation);
		break;
	}

	/* Special return value '1' means: do not free */
	if (rc != 1)
		msgb_free(msg);

	return rc;
}

/* any L1 prim sent to bts model */
static int l1sap_down(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap)
{
	l1sap_log_ctx_sapi = get_common_sapi_by_trx_prim(trx, l1sap);
	log_set_context(LOG_CTX_L1_SAPI, &l1sap_log_ctx_sapi);

	if (OSMO_PRIM_HDR(&l1sap->oph) ==
				 OSMO_PRIM(PRIM_PH_DATA, PRIM_OP_REQUEST))
		to_gsmtap(trx, l1sap);

	return bts_model_l1sap_down(trx, l1sap);
}

/* pcu (socket interface) sends us a data request primitive */
int l1sap_pdch_req(struct gsm_bts_trx_ts *ts, int is_ptcch, uint32_t fn,
	uint16_t arfcn, uint8_t block_nr, const uint8_t *data, uint8_t len)
{
	struct msgb *msg;
	struct osmo_phsap_prim *l1sap;
	struct gsm_time g_time;

	gsm_fn2gsmtime(&g_time, fn);

	DEBUGP(DL1P, "TX packet data %s is_ptcch=%d trx=%d ts=%d "
		"block_nr=%d, arfcn=%d, len=%d\n", osmo_dump_gsmtime(&g_time),
		is_ptcch, ts->trx->nr, ts->nr, block_nr, arfcn, len);

	msg = l1sap_msgb_alloc(len);
	l1sap = msgb_l1sap_prim(msg);
	osmo_prim_init(&l1sap->oph, SAP_GSM_PH, PRIM_PH_DATA, PRIM_OP_REQUEST,
		msg);
	l1sap->u.data.chan_nr = RSL_CHAN_OSMO_PDCH | ts->nr;
	l1sap->u.data.link_id = 0x00;
	l1sap->u.data.fn = fn;
	if (len) {
		msg->l2h = msgb_put(msg, len);
		memcpy(msg->l2h, data, len);
	} else {
		msg->l2h = NULL; /* Idle block */
	}

	return l1sap_down(ts->trx, l1sap);
}

/*! \brief call-back function for incoming RTP */
void l1sap_rtp_rx_cb(struct osmo_rtp_socket *rs, const uint8_t *rtp_pl,
                     unsigned int rtp_pl_len, uint16_t seq_number,
		     uint32_t timestamp, bool marker)
{
	struct gsm_lchan *lchan = rs->priv;
	struct msgb *msg;
	struct osmo_phsap_prim *l1sap;

	/* if we're in loopback mode, we don't accept frames from the
	 * RTP socket anymore */
	if (lchan->loopback)
		return;

	msg = l1sap_msgb_alloc(rtp_pl_len);
	if (!msg)
		return;
	memcpy(msgb_put(msg, rtp_pl_len), rtp_pl, rtp_pl_len);
	msgb_pull(msg, sizeof(*l1sap));

	/* Store RTP header Marker bit in control buffer */
	rtpmsg_marker_bit(msg) = marker;
	/* Store RTP header Sequence Number in control buffer */
	rtpmsg_seq(msg) = seq_number;
	/* Store RTP header Timestamp in control buffer */
	rtpmsg_ts(msg) = timestamp;

	/* make sure the queue doesn't get too long */
	lchan_dl_tch_queue_enqueue(lchan, msg, 1);
}

static int l1sap_chan_act_dact_modify(struct gsm_bts_trx *trx, uint8_t chan_nr,
		enum osmo_mph_info_type type, uint8_t sacch_only)
{
	struct osmo_phsap_prim l1sap;

	memset(&l1sap, 0, sizeof(l1sap));
	osmo_prim_init(&l1sap.oph, SAP_GSM_PH, PRIM_MPH_INFO, PRIM_OP_REQUEST,
		NULL);
	l1sap.u.info.type = type;
	l1sap.u.info.u.act_req.chan_nr = chan_nr;
	l1sap.u.info.u.act_req.sacch_only = sacch_only;

	return l1sap_down(trx, &l1sap);
}

int l1sap_chan_act(struct gsm_bts_trx *trx, uint8_t chan_nr)
{
	struct gsm_lchan *lchan = get_lchan_by_chan_nr(trx, chan_nr);
	int rc;

	if (lchan->state == LCHAN_S_ACTIVE) {
		LOGPLCHAN(lchan, DL1C, LOGL_ERROR, "Trying to activate already active channel %s\n",
			  rsl_chan_nr_str(chan_nr));
		return -1;
	}

	LOGPLCHAN(lchan, DL1C, LOGL_INFO, "Activating channel %s\n", rsl_chan_nr_str(chan_nr));

	lchan->s = trx->bts->radio_link_timeout.current;

	rc = l1sap_chan_act_dact_modify(trx, chan_nr, PRIM_INFO_ACTIVATE, 0);
	if (rc)
		return -RSL_ERR_EQUIPMENT_FAIL;

	/* Init DTX DL FSM if necessary */
	if (trx->bts->dtxd && lchan_is_tch(lchan)) {
		lchan->tch.dtx.dl_amr_fsm = osmo_fsm_inst_alloc(&dtx_dl_amr_fsm,
								tall_bts_ctx,
								lchan,
								LOGL_DEBUG,
								NULL);
		if (!lchan->tch.dtx.dl_amr_fsm) {
			l1sap_chan_act_dact_modify(trx, chan_nr, PRIM_INFO_DEACTIVATE, 0);
			return -RSL_ERR_EQUIPMENT_FAIL;
		}

		rc = osmo_fsm_inst_update_id_f(lchan->tch.dtx.dl_amr_fsm,
					       "bts%u-trx%u-ts%u-ss%u%s",
					       trx->bts->nr, trx->nr,
					       lchan->ts->nr, lchan->nr,
					       lchan->ts->vamos.is_shadow ? "-shadow" : "");
		OSMO_ASSERT(rc == 0);
	}
	return 0;
}

int l1sap_chan_rel(struct gsm_bts_trx *trx, uint8_t chan_nr)
{
	struct gsm_lchan *lchan = get_lchan_by_chan_nr(trx, chan_nr);

	if (lchan->state == LCHAN_S_NONE) {
		LOGPLCHAN(lchan, DL1C, LOGL_ERROR, "Trying to deactivate already deactivated channel %s\n",
			  rsl_chan_nr_str(chan_nr));
		return -1;
	}

	LOGPLCHAN(lchan, DL1C, LOGL_INFO, "Deactivating channel %s\n",
		  rsl_chan_nr_str(chan_nr));

	if (lchan->tch.dtx.dl_amr_fsm) {
		osmo_fsm_inst_free(lchan->tch.dtx.dl_amr_fsm);
		lchan->tch.dtx.dl_amr_fsm = NULL;
	}

	return l1sap_chan_act_dact_modify(trx, chan_nr, PRIM_INFO_DEACTIVATE,
		0);
}

int l1sap_chan_deact_sacch(struct gsm_bts_trx *trx, uint8_t chan_nr)
{
	struct gsm_lchan *lchan = get_lchan_by_chan_nr(trx, chan_nr);

	LOGPLCHAN(lchan, DL1C, LOGL_INFO, "Deactivating SACCH on channel %s\n",
		  rsl_chan_nr_str(chan_nr));

	return l1sap_chan_act_dact_modify(trx, chan_nr, PRIM_INFO_DEACTIVATE,
		1);
}

int l1sap_chan_modify(struct gsm_bts_trx *trx, uint8_t chan_nr)
{
	struct gsm_lchan *lchan = get_lchan_by_chan_nr(trx, chan_nr);

	LOGPLCHAN(lchan, DL1C, LOGL_INFO, "Modifying channel %s\n",
		rsl_chan_nr_str(chan_nr));

	return l1sap_chan_act_dact_modify(trx, chan_nr, PRIM_INFO_MODIFY, 0);
}