path: root/src/gb/gprs_bssgp.c

/*! \file gprs_bssgp.c
 * GPRS BSSGP protocol implementation as per 3GPP TS 08.18. */
/*
 * (C) 2009-2017 by Harald Welte <laforge@gnumonks.org>
 *
 * All Rights Reserved
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 * TODO:
 *  o  properly count incoming BVC-RESET packets in counter group
 *  o  set log context as early as possible for outgoing packets
 */

#include <errno.h>
#include <stdint.h>

#include <osmocom/core/msgb.h>
#include <osmocom/core/byteswap.h>
#include <osmocom/core/bit16gen.h>
#include <osmocom/gsm/tlv.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/rate_ctr.h>
#include <osmocom/core/stats.h>

#include <osmocom/gprs/gprs_bssgp.h>
#include <osmocom/gprs/gprs_bssgp_bss.h>
#include <osmocom/gprs/gprs_ns.h>

#include "common_vty.h"

void *bssgp_tall_ctx = NULL;

static const struct rate_ctr_desc bssgp_ctr_description[] = {
	{ "packets:in",	"Packets at BSSGP Level ( In)" },
	{ "packets:out","Packets at BSSGP Level (Out)" },
	{ "bytes:in",	"Bytes at BSSGP Level   ( In)" },
	{ "bytes:out",	"Bytes at BSSGP Level   (Out)" },
	{ "blocked",	"BVC Blocking count" },
	{ "discarded",	"BVC LLC Discarded count" },
	{ "status",	"BVC Status count" },
};

static const struct rate_ctr_group_desc bssgp_ctrg_desc = {
	.group_name_prefix = "bssgp:bss_ctx",
	.group_description = "BSSGP Peer Statistics",
	.num_ctr = ARRAY_SIZE(bssgp_ctr_description),
	.ctr_desc = bssgp_ctr_description,
	.class_id = OSMO_STATS_CLASS_PEER,
};

LLIST_HEAD(bssgp_bvc_ctxts);

static int _bssgp_tx_dl_ud(struct bssgp_flow_control *fc, struct msgb *msg,
			   uint32_t llc_pdu_len, void *priv);

/* Find a BTS Context based on parsed RA ID and Cell ID */
struct bssgp_bvc_ctx *btsctx_by_raid_cid(const struct gprs_ra_id *raid, uint16_t cid)
{
	struct bssgp_bvc_ctx *bctx;

	llist_for_each_entry(bctx, &bssgp_bvc_ctxts, list) {
		if (!memcmp(&bctx->ra_id, raid, sizeof(bctx->ra_id)) &&
		    bctx->cell_id == cid)
			return bctx;
	}
	return NULL;
}

/*! Initiate reset procedure for all PTP BVC on a given NSEI.
 *
 *  This function initiates reset procedure for all PTP BVC with a given cause.
 *  \param[in] nsei NSEI to which PTP BVC should belong to
 *  \param[in] cause Cause of BVC RESET
 *  \returns 0 on success, negative error code otherwise
 */
int bssgp_tx_bvc_ptp_reset(uint16_t nsei, enum gprs_bssgp_cause cause)
{
	int rc;
	struct bssgp_bvc_ctx *bctx;

	llist_for_each_entry(bctx, &bssgp_bvc_ctxts, list) {
		if (bctx->nsei == nsei && bctx->bvci != BVCI_SIGNALLING) {
			LOGP(DBSSGP, LOGL_DEBUG, "NSEI=%u/BVCI=%u RESET due to %s\n",
			     nsei, bctx->bvci, bssgp_cause_str(cause));
			rc = bssgp_tx_bvc_reset(bctx, bctx->bvci, cause);
			if (rc < 0)
				return rc;
		}
	}

	return 0;
}

/* Find a BTS context based on BVCI+NSEI tuple */
struct bssgp_bvc_ctx *btsctx_by_bvci_nsei(uint16_t bvci, uint16_t nsei)
{
	struct bssgp_bvc_ctx *bctx;

	llist_for_each_entry(bctx, &bssgp_bvc_ctxts, list) {
		if (bctx->nsei == nsei && bctx->bvci == bvci)
			return bctx;
	}
	return NULL;
}

struct bssgp_bvc_ctx *btsctx_alloc(uint16_t bvci, uint16_t nsei)
{
	struct bssgp_bvc_ctx *ctx;

	ctx = talloc_zero(bssgp_tall_ctx, struct bssgp_bvc_ctx);
	if (!ctx)
		return NULL;
	ctx->bvci = bvci;
	ctx->nsei = nsei;
	/* FIXME: BVCI is not unique, only BVCI+NSEI ?!? */
	ctx->ctrg = rate_ctr_group_alloc(ctx, &bssgp_ctrg_desc, bvci);
	ctx->fc = talloc_zero(ctx, struct bssgp_flow_control);
	/* cofigure for 2Mbit, 30 packets in queue */
	bssgp_fc_init(ctx->fc, 100000, 2*1024*1024/8, 30, &_bssgp_tx_dl_ud);

	llist_add(&ctx->list, &bssgp_bvc_ctxts);

	return ctx;
}

/* Chapter 10.4.5: Flow Control BVC ACK */
static int bssgp_tx_fc_bvc_ack(uint16_t nsei, uint8_t tag, uint16_t ns_bvci)
{
	struct msgb *msg = bssgp_msgb_alloc();
	struct bssgp_normal_hdr *bgph =
			(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));

	msgb_nsei(msg) = nsei;
	msgb_bvci(msg) = ns_bvci;

	bgph->pdu_type = BSSGP_PDUT_FLOW_CONTROL_BVC_ACK;
	msgb_tvlv_put(msg, BSSGP_IE_TAG, 1, &tag);

	return gprs_ns_sendmsg(bssgp_nsi, msg);
}

/* 10.3.7 SUSPEND-ACK PDU */
int bssgp_tx_suspend_ack(uint16_t nsei, uint32_t tlli,
			 const struct gprs_ra_id *ra_id, uint8_t suspend_ref)
{
	struct msgb *msg = bssgp_msgb_alloc();
	struct bssgp_normal_hdr *bgph =
		(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
	uint32_t _tlli;
	uint8_t ra[6];

	msgb_nsei(msg) = nsei;
	msgb_bvci(msg) = 0; /* Signalling */
	bgph->pdu_type = BSSGP_PDUT_SUSPEND_ACK;

	_tlli = osmo_htonl(tlli);
	msgb_tvlv_put(msg, BSSGP_IE_TLLI, 4, (uint8_t *) &_tlli);
	gsm48_construct_ra(ra, ra_id);
	msgb_tvlv_put(msg, BSSGP_IE_ROUTEING_AREA, 6, ra);
	msgb_tvlv_put(msg, BSSGP_IE_SUSPEND_REF_NR, 1, &suspend_ref);

	return gprs_ns_sendmsg(bssgp_nsi, msg);
}

/* 10.3.8 SUSPEND-NACK PDU */
int bssgp_tx_suspend_nack(uint16_t nsei, uint32_t tlli,
			  const struct gprs_ra_id *ra_id,
			  uint8_t *cause)
{
	struct msgb *msg = bssgp_msgb_alloc();
	struct bssgp_normal_hdr *bgph =
		(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
	uint32_t _tlli;
	uint8_t ra[6];

	msgb_nsei(msg) = nsei;
	msgb_bvci(msg) = 0; /* Signalling */
	bgph->pdu_type = BSSGP_PDUT_SUSPEND_NACK;

	_tlli = osmo_htonl(tlli);
	msgb_tvlv_put(msg, BSSGP_IE_TLLI, 4, (uint8_t *) &_tlli);
	gsm48_construct_ra(ra, ra_id);
	msgb_tvlv_put(msg, BSSGP_IE_ROUTEING_AREA, 6, ra);
	if (cause)
		msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, cause);

	return gprs_ns_sendmsg(bssgp_nsi, msg);
}

/* 10.3.10 RESUME-ACK PDU */
int bssgp_tx_resume_ack(uint16_t nsei, uint32_t tlli,
			const struct gprs_ra_id *ra_id)
{
	struct msgb *msg = bssgp_msgb_alloc();
	struct bssgp_normal_hdr *bgph =
		(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
	uint32_t _tlli;
	uint8_t ra[6];

	msgb_nsei(msg) = nsei;
	msgb_bvci(msg) = 0; /* Signalling */
	bgph->pdu_type = BSSGP_PDUT_RESUME_ACK;

	_tlli = osmo_htonl(tlli);
	msgb_tvlv_put(msg, BSSGP_IE_TLLI, 4, (uint8_t *) &_tlli);
	gsm48_construct_ra(ra, ra_id);
	msgb_tvlv_put(msg, BSSGP_IE_ROUTEING_AREA, 6, ra);

	return gprs_ns_sendmsg(bssgp_nsi, msg);
}

/* 10.3.11 RESUME-NACK PDU */
int bssgp_tx_resume_nack(uint16_t nsei, uint32_t tlli,
			 const struct gprs_ra_id *ra_id, uint8_t *cause)
{
	struct msgb *msg = bssgp_msgb_alloc();
	struct bssgp_normal_hdr *bgph =
		(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
	uint32_t _tlli;
	uint8_t ra[6];

	msgb_nsei(msg) = nsei;
	msgb_bvci(msg) = 0; /* Signalling */
	bgph->pdu_type = BSSGP_PDUT_SUSPEND_NACK;

	_tlli = osmo_htonl(tlli);
	msgb_tvlv_put(msg, BSSGP_IE_TLLI, 4, (uint8_t *) &_tlli);
	gsm48_construct_ra(ra, ra_id);
	msgb_tvlv_put(msg, BSSGP_IE_ROUTEING_AREA, 6, ra);
	if (cause)
		msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, cause);

	return gprs_ns_sendmsg(bssgp_nsi, msg);
}

uint16_t bssgp_parse_cell_id(struct gprs_ra_id *raid, const uint8_t *buf)
{
	/* 6 octets RAC */
	gsm48_parse_ra(raid, buf);
	/* 2 octets CID */
	return osmo_load16be(buf+6);
}

int bssgp_create_cell_id(uint8_t *buf, const struct gprs_ra_id *raid,
			 uint16_t cid)
{
	/* 6 octets RAC */
	gsm48_construct_ra(buf, raid);
	/* 2 octets CID */
	osmo_store16be(cid, buf+6);

	return 8;
}

/* Chapter 8.4 BVC-Reset Procedure */
static int bssgp_rx_bvc_reset(struct msgb *msg, struct tlv_parsed *tp,	
			      uint16_t ns_bvci)
{
	struct osmo_bssgp_prim nmp;
	struct bssgp_bvc_ctx *bctx;
	uint16_t nsei = msgb_nsei(msg);
	uint16_t bvci;

	bvci = tlvp_val16be(tp, BSSGP_IE_BVCI);
	DEBUGP(DBSSGP, "BSSGP BVCI=%u Rx RESET cause=%s\n", bvci,
		bssgp_cause_str(*TLVP_VAL(tp, BSSGP_IE_CAUSE)));

	/* look-up or create the BTS context for this BVC */
	bctx = btsctx_by_bvci_nsei(bvci, nsei);
	if (!bctx)
		bctx = btsctx_alloc(bvci, nsei);

	/* As opposed to NS-VCs, BVCs are NOT blocked after RESET */
	bctx->state &= ~BVC_S_BLOCKED;

	/* When we receive a BVC-RESET PDU (at least of a PTP BVCI), the BSS
	 * informs us about its RAC + Cell ID, so we can create a mapping */
	if (bvci != 0 && bvci != 1) {
		if (!TLVP_PRESENT(tp, BSSGP_IE_CELL_ID)) {
			LOGP(DBSSGP, LOGL_ERROR, "BSSGP BVCI=%u Rx RESET "
				"missing mandatory IE\n", bvci);
			return -EINVAL;
		}
		/* actually extract RAC / CID */
		bctx->cell_id = bssgp_parse_cell_id(&bctx->ra_id,
						TLVP_VAL(tp, BSSGP_IE_CELL_ID));
		LOGP(DBSSGP, LOGL_NOTICE, "Cell %u-%u-%u-%u CI %u on BVCI %u\n",
			bctx->ra_id.mcc, bctx->ra_id.mnc, bctx->ra_id.lac,
			bctx->ra_id.rac, bctx->cell_id, bvci);
	}

	/* Send NM_BVC_RESET.ind to NM */
	memset(&nmp, 0, sizeof(nmp));
	nmp.nsei = nsei;
	nmp.bvci = bvci;
	nmp.tp = tp;
	nmp.ra_id = &bctx->ra_id;
	osmo_prim_init(&nmp.oph, SAP_BSSGP_NM, PRIM_NM_BVC_RESET,
			PRIM_OP_INDICATION, msg);
	bssgp_prim_cb(&nmp.oph, NULL);

	/* Acknowledge the RESET to the BTS */
	bssgp_tx_simple_bvci(BSSGP_PDUT_BVC_RESET_ACK,
			     nsei, bvci, ns_bvci);
	return 0;
}

static int bssgp_rx_bvc_block(struct msgb *msg, struct tlv_parsed *tp)
{
	struct osmo_bssgp_prim nmp;
	uint16_t bvci;
	struct bssgp_bvc_ctx *ptp_ctx;

	bvci = tlvp_val16be(tp, BSSGP_IE_BVCI);
	if (bvci == BVCI_SIGNALLING) {
		/* 8.3.2: Signalling BVC shall never be blocked */
		LOGP(DBSSGP, LOGL_ERROR, "NSEI=%u/BVCI=%u "
			"received block for signalling BVC!?!\n",
			msgb_nsei(msg), msgb_bvci(msg));
		return 0;
	}

	LOGP(DBSSGP, LOGL_INFO, "BSSGP Rx BVCI=%u BVC-BLOCK\n", bvci);

	ptp_ctx = btsctx_by_bvci_nsei(bvci, msgb_nsei(msg));
	if (!ptp_ctx)
		return bssgp_tx_status(BSSGP_CAUSE_UNKNOWN_BVCI, &bvci, msg);

	ptp_ctx->state |= BVC_S_BLOCKED;
	rate_ctr_inc(&ptp_ctx->ctrg->ctr[BSSGP_CTR_BLOCKED]);

	/* Send NM_BVC_BLOCK.ind to NM */
	memset(&nmp, 0, sizeof(nmp));
	nmp.nsei = msgb_nsei(msg);
	nmp.bvci = bvci;
	nmp.tp = tp;
	osmo_prim_init(&nmp.oph, SAP_BSSGP_NM, PRIM_NM_BVC_BLOCK,
			PRIM_OP_INDICATION, msg);
	bssgp_prim_cb(&nmp.oph, NULL);

	/* We always acknowledge the BLOCKing */
	return bssgp_tx_simple_bvci(BSSGP_PDUT_BVC_BLOCK_ACK, msgb_nsei(msg),
				    bvci, msgb_bvci(msg));
};

static int bssgp_rx_bvc_unblock(struct msgb *msg, struct tlv_parsed *tp)
{
	struct osmo_bssgp_prim nmp;
	uint16_t bvci;
	struct bssgp_bvc_ctx *ptp_ctx;

	bvci = tlvp_val16be(tp, BSSGP_IE_BVCI);
	if (bvci == BVCI_SIGNALLING) {
		/* 8.3.2: Signalling BVC shall never be blocked */
		LOGP(DBSSGP, LOGL_ERROR, "NSEI=%u/BVCI=%u "
			"received unblock for signalling BVC!?!\n",
			msgb_nsei(msg), msgb_bvci(msg));
		return 0;
	}

	DEBUGP(DBSSGP, "BSSGP BVCI=%u Rx BVC-UNBLOCK\n", bvci);

	ptp_ctx = btsctx_by_bvci_nsei(bvci, msgb_nsei(msg));
	if (!ptp_ctx)
		return bssgp_tx_status(BSSGP_CAUSE_UNKNOWN_BVCI, &bvci, msg);

	ptp_ctx->state &= ~BVC_S_BLOCKED;

	/* Send NM_BVC_UNBLOCK.ind to NM */
	memset(&nmp, 0, sizeof(nmp));
	nmp.nsei = msgb_nsei(msg);
	nmp.bvci = bvci;
	nmp.tp = tp;
	osmo_prim_init(&nmp.oph, SAP_BSSGP_NM, PRIM_NM_BVC_UNBLOCK,
			PRIM_OP_INDICATION, msg);
	bssgp_prim_cb(&nmp.oph, NULL);

	/* We always acknowledge the unBLOCKing */
	return bssgp_tx_simple_bvci(BSSGP_PDUT_BVC_UNBLOCK_ACK, msgb_nsei(msg),
				    bvci, msgb_bvci(msg));
};

/* Uplink unit-data */
static int bssgp_rx_ul_ud(struct msgb *msg, struct tlv_parsed *tp,
			  struct bssgp_bvc_ctx *ctx)
{
	struct osmo_bssgp_prim gbp;
	struct bssgp_ud_hdr *budh = (struct bssgp_ud_hdr *) msgb_bssgph(msg);

	/* extract TLLI and parse TLV IEs */
	msgb_tlli(msg) = osmo_ntohl(budh->tlli);

	DEBUGP(DBSSGP, "BSSGP TLLI=0x%08x Rx UPLINK-UNITDATA\n", msgb_tlli(msg));

	/* Cell ID and LLC_PDU are the only mandatory IE */
	if (!TLVP_PRESENT(tp, BSSGP_IE_CELL_ID) ||
	    !TLVP_PRESENT(tp, BSSGP_IE_LLC_PDU)) {
		LOGP(DBSSGP, LOGL_ERROR, "BSSGP TLLI=0x%08x Rx UL-UD "
			"missing mandatory IE\n", msgb_tlli(msg));
		return bssgp_tx_status(BSSGP_CAUSE_MISSING_MAND_IE, NULL, msg);
	}

	/* store pointer to LLC header and CELL ID in msgb->cb */
	msgb_llch(msg) = (uint8_t *) TLVP_VAL(tp, BSSGP_IE_LLC_PDU);
	msgb_bcid(msg) = (uint8_t *) TLVP_VAL(tp, BSSGP_IE_CELL_ID);

	/* Send BSSGP_UL_UD.ind to NM */
	memset(&gbp, 0, sizeof(gbp));
	gbp.nsei = ctx->nsei;
	gbp.bvci = ctx->bvci;
	gbp.tlli = msgb_tlli(msg);
	gbp.tp = tp;
	osmo_prim_init(&gbp.oph, SAP_BSSGP_LL, PRIM_BSSGP_UL_UD,
			PRIM_OP_INDICATION, msg);
	return bssgp_prim_cb(&gbp.oph, NULL);
}

static int bssgp_rx_suspend(struct msgb *msg, struct tlv_parsed *tp)
{
	struct osmo_bssgp_prim gbp;
	struct gprs_ra_id raid;
	uint32_t tlli;
	uint16_t ns_bvci = msgb_bvci(msg);
	int rc;

	if (!TLVP_PRESENT(tp, BSSGP_IE_TLLI) ||
	    !TLVP_PRESENT(tp, BSSGP_IE_ROUTEING_AREA)) {
		LOGP(DBSSGP, LOGL_ERROR, "BSSGP BVCI=%u Rx SUSPEND "
			"missing mandatory IE\n", ns_bvci);
		return bssgp_tx_status(BSSGP_CAUSE_MISSING_MAND_IE, NULL, msg);
	}

	tlli = tlvp_val32be(tp, BSSGP_IE_TLLI);

	DEBUGP(DBSSGP, "BSSGP BVCI=%u TLLI=0x%08x Rx SUSPEND\n",
		ns_bvci, tlli);

	gsm48_parse_ra(&raid, TLVP_VAL(tp, BSSGP_IE_ROUTEING_AREA));

	/* Inform GMM about the SUSPEND request */
	memset(&gbp, 0, sizeof(gbp));
	gbp.nsei = msgb_nsei(msg);
	gbp.bvci = ns_bvci;
	gbp.tlli = tlli;
	gbp.ra_id = &raid;
	osmo_prim_init(&gbp.oph, SAP_BSSGP_GMM, PRIM_BSSGP_GMM_SUSPEND,
			PRIM_OP_REQUEST, msg);

	rc = bssgp_prim_cb(&gbp.oph, NULL);
	if (rc < 0)
		return bssgp_tx_suspend_nack(msgb_nsei(msg), tlli, &raid, NULL);

	bssgp_tx_suspend_ack(msgb_nsei(msg), tlli, &raid, 0);

	return 0;
}

static int bssgp_rx_resume(struct msgb *msg, struct tlv_parsed *tp)
{
	struct osmo_bssgp_prim gbp;
	struct gprs_ra_id raid;
	uint32_t tlli;
	uint8_t suspend_ref;
	uint16_t ns_bvci = msgb_bvci(msg);
	int rc;

	if (!TLVP_PRESENT(tp, BSSGP_IE_TLLI) ||
	    !TLVP_PRESENT(tp, BSSGP_IE_ROUTEING_AREA) ||
	    !TLVP_PRESENT(tp, BSSGP_IE_SUSPEND_REF_NR)) {
		LOGP(DBSSGP, LOGL_ERROR, "BSSGP BVCI=%u Rx RESUME "
			"missing mandatory IE\n", ns_bvci);
		return bssgp_tx_status(BSSGP_CAUSE_MISSING_MAND_IE, NULL, msg);
	}

	tlli = tlvp_val32be(tp, BSSGP_IE_TLLI);
	suspend_ref = *TLVP_VAL(tp, BSSGP_IE_SUSPEND_REF_NR);

	DEBUGP(DBSSGP, "BSSGP BVCI=%u TLLI=0x%08x Rx RESUME\n", ns_bvci, tlli);

	gsm48_parse_ra(&raid, TLVP_VAL(tp, BSSGP_IE_ROUTEING_AREA));

	/* Inform GMM about the RESUME request */
	memset(&gbp, 0, sizeof(gbp));
	gbp.nsei = msgb_nsei(msg);
	gbp.bvci = ns_bvci;
	gbp.tlli = tlli;
	gbp.ra_id = &raid;
	gbp.u.resume.suspend_ref = suspend_ref;
	osmo_prim_init(&gbp.oph, SAP_BSSGP_GMM, PRIM_BSSGP_GMM_RESUME,
			PRIM_OP_REQUEST, msg);

	rc = bssgp_prim_cb(&gbp.oph, NULL);
	if (rc < 0)
		return bssgp_tx_resume_nack(msgb_nsei(msg), tlli, &raid,
					    NULL);

	bssgp_tx_resume_ack(msgb_nsei(msg), tlli, &raid);
	return 0;
}


static int bssgp_rx_llc_disc(struct msgb *msg, struct tlv_parsed *tp,
			     struct bssgp_bvc_ctx *ctx)
{
	struct osmo_bssgp_prim nmp;
	uint32_t tlli = 0;

	if (!TLVP_PRESENT(tp, BSSGP_IE_TLLI) ||
	    !TLVP_PRESENT(tp, BSSGP_IE_LLC_FRAMES_DISCARDED) ||
	    !TLVP_PRESENT(tp, BSSGP_IE_BVCI) ||
	    !TLVP_PRESENT(tp, BSSGP_IE_NUM_OCT_AFF)) {
		LOGP(DBSSGP, LOGL_ERROR, "BSSGP BVCI=%u Rx LLC DISCARDED "
			"missing mandatory IE\n", ctx->bvci);
	}

	if (TLVP_PRESENT(tp, BSSGP_IE_TLLI))
		tlli = tlvp_val32be(tp, BSSGP_IE_TLLI);

	DEBUGP(DBSSGP, "BSSGP BVCI=%u TLLI=%08x Rx LLC DISCARDED\n",
		ctx->bvci, tlli);

	rate_ctr_inc(&ctx->ctrg->ctr[BSSGP_CTR_DISCARDED]);

	/* send NM_LLC_DISCARDED to NM */
	memset(&nmp, 0, sizeof(nmp));
	nmp.nsei = msgb_nsei(msg);
	nmp.bvci = ctx->bvci;
	nmp.tlli = tlli;
	nmp.tp = tp;
	osmo_prim_init(&nmp.oph, SAP_BSSGP_NM, PRIM_NM_LLC_DISCARDED,
			PRIM_OP_INDICATION, msg);

	return bssgp_prim_cb(&nmp.oph, NULL);
}

int bssgp_rx_status(struct msgb *msg, struct tlv_parsed *tp,
	uint16_t bvci, struct bssgp_bvc_ctx *bctx)
{
	struct osmo_bssgp_prim nmp;
	enum gprs_bssgp_cause cause;

	if (!TLVP_PRESENT(tp, BSSGP_IE_CAUSE)) {
		LOGP(DBSSGP, LOGL_ERROR, "BSSGP BVCI=%u Rx STATUS "
			"missing mandatory IE\n", bvci);
		cause = BSSGP_CAUSE_PROTO_ERR_UNSPEC;
	} else {
		cause = *TLVP_VAL(tp, BSSGP_IE_CAUSE);
	}

	LOGP(DBSSGP, LOGL_NOTICE, "BSSGP BVCI=%u Rx BVC STATUS, cause=%s\n",
		bvci, bssgp_cause_str(cause));

	if (cause == BSSGP_CAUSE_BVCI_BLOCKED || cause == BSSGP_CAUSE_UNKNOWN_BVCI) {
		if (!TLVP_PRESENT(tp, BSSGP_IE_BVCI))
			LOGP(DBSSGP, LOGL_ERROR,
				"BSSGP BVCI=%u Rx STATUS cause=%s "
				"missing conditional BVCI IE\n",
				bvci, bssgp_cause_str(cause));
	}

	if (bctx)
		rate_ctr_inc(&bctx->ctrg->ctr[BSSGP_CTR_STATUS]);

	/* send NM_STATUS to NM */
	memset(&nmp, 0, sizeof(nmp));
	nmp.nsei = msgb_nsei(msg);
	nmp.bvci = bvci;
	nmp.tp = tp;
	osmo_prim_init(&nmp.oph, SAP_BSSGP_NM, PRIM_NM_STATUS,
			PRIM_OP_INDICATION, msg);

	return bssgp_prim_cb(&nmp.oph, NULL);
}


/* One element (msgb) in a BSSGP Flow Control queue */
struct bssgp_fc_queue_element {
	/* linked list of queue elements */
	struct llist_head list;
	/* The message that we have enqueued */
	struct msgb *msg;
	/* Length of the LLC PDU part of the contained message */
	uint32_t llc_pdu_len;
	/* private pointer passed to the flow control out_cb function */
	void *priv;
};

static int fc_queue_timer_cfg(struct bssgp_flow_control *fc);
static int bssgp_fc_needs_queueing(struct bssgp_flow_control *fc, uint32_t pdu_len);

static void fc_timer_cb(void *data)
{
	struct bssgp_flow_control *fc = data;
	struct bssgp_fc_queue_element *fcqe;
	struct timeval time_now;

	/* if the queue is empty, we return without sending something
	 * and without re-starting the timer */
	if (llist_empty(&fc->queue))
		return;

	/* get the first entry from the queue */
	fcqe = llist_entry(fc->queue.next, struct bssgp_fc_queue_element,
			   list);

	if (bssgp_fc_needs_queueing(fc, fcqe->llc_pdu_len)) {
		LOGP(DBSSGP, LOGL_NOTICE, "BSSGP-FC: fc_timer_cb() but still "
			"not able to send PDU of %u bytes\n", fcqe->llc_pdu_len);
		/* make sure we re-start the t