src/gb_proxy.c

/* NS-over-IP proxy */

/* (C) 2010-2020 by Harald Welte <laforge@gnumonks.org>
 * (C) 2010-2013 by On-Waves
 * (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 Affero 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 <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <errno.h>
#include <sys/fcntl.h>
#include <sys/stat.h>
#include <arpa/inet.h>
#include <time.h>

#include <osmocom/core/hashtable.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/linuxlist.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/select.h>
#include <osmocom/core/rate_ctr.h>
#include <osmocom/core/signal.h>
#include <osmocom/core/stats.h>
#include <osmocom/core/utils.h>

#include <osmocom/gprs/gprs_ns2.h>
#include <osmocom/gprs/gprs_bssgp.h>
#include <osmocom/gprs/gprs_bssgp2.h>
#include <osmocom/gprs/gprs_bssgp_bss.h>
#include <osmocom/gprs/bssgp_bvc_fsm.h>
#include <osmocom/gprs/protocol/gsm_08_18.h>

#include <osmocom/gsm/gsm23236.h>
#include <osmocom/gsm/gsm_utils.h>

#include "debug.h"
#include <osmocom/gbproxy/gb_proxy.h>

#include <osmocom/gsm/protocol/gsm_04_08_gprs.h>

extern void *tall_sgsn_ctx;

static const struct rate_ctr_desc global_ctr_description[] = {
	[GBPROX_GLOB_CTR_INV_BVCI]		= { "inv-bvci",	    "Invalid BVC Identifier          " },
	[GBPROX_GLOB_CTR_INV_LAI]		= { "inv-lai",	    "Invalid Location Area Identifier" },
	[GBPROX_GLOB_CTR_INV_RAI]		= { "inv-rai",	    "Invalid Routing Area Identifier " },
	[GBPROX_GLOB_CTR_INV_NSEI]		= { "inv-nsei",	    "No BVC established for NSEI     " },
	[GBPROX_GLOB_CTR_PROTO_ERR_BSS]		= { "proto-err:bss",  "BSSGP protocol error      (BSS )" },
	[GBPROX_GLOB_CTR_PROTO_ERR_SGSN]	= { "proto-err:sgsn", "BSSGP protocol error      (SGSN)" },
	[GBPROX_GLOB_CTR_NOT_SUPPORTED_BSS]	= { "not-supp:bss",   "Feature not supported     (BSS )" },
	[GBPROX_GLOB_CTR_NOT_SUPPORTED_SGSN]	= { "not-supp:sgsn",  "Feature not supported     (SGSN)" },
	[GBPROX_GLOB_CTR_RESTART_RESET_SGSN]	= { "restart:sgsn",   "Restarted RESET procedure (SGSN)" },
	[GBPROX_GLOB_CTR_TX_ERR_SGSN]		= { "tx-err:sgsn",    "NS Transmission error     (SGSN)" },
	[GBPROX_GLOB_CTR_OTHER_ERR]		= { "error",          "Other error                     " },
};

static const struct rate_ctr_group_desc global_ctrg_desc = {
	.group_name_prefix = "gbproxy:global",
	.group_description = "GBProxy Global Statistics",
	.num_ctr = ARRAY_SIZE(global_ctr_description),
	.ctr_desc = global_ctr_description,
	.class_id = OSMO_STATS_CLASS_GLOBAL,
};

static int gbprox_relay2peer(struct msgb *old_msg, struct gbproxy_bvc *bvc,
			     uint16_t ns_bvci);

int tx_status(struct gbproxy_nse *nse, uint16_t ns_bvci, enum gprs_bssgp_cause cause, const uint16_t *bvci, const struct msgb *old_msg)
{
	int rc;

	struct msgb *msg = bssgp2_enc_status(cause, bvci, old_msg, nse->max_sdu_len);
	if (!msg) {
		LOGPNSE(nse, LOGL_NOTICE, "Unable to encode STATUS message\n");
		return -ENOMEM;
	}

	rc = bssgp2_nsi_tx_ptp(nse->cfg->nsi, nse->nsei, ns_bvci, msg, 0);
	if (rc < 0)
		LOGPNSE(nse, LOGL_NOTICE, "Unable to send STATUS message\n");
	return rc;
}

/* generate BVC-STATUS mess
age with cause value derived from TLV-parser error */
static int tx_status_from_tlvp(struct gbproxy_nse *nse, enum osmo_tlv_parser_error tlv_p_err, struct msgb *orig_msg)
{
	uint8_t bssgp_cause;
	switch (tlv_p_err) {
	case OSMO_TLVP_ERR_MAND_IE_MISSING:
		bssgp_cause = BSSGP_CAUSE_MISSING_MAND_IE;
		break;
	default:
		bssgp_cause = BSSGP_CAUSE_PROTO_ERR_UNSPEC;
	}
	return tx_status(nse, msgb_bvci(orig_msg), bssgp_cause, NULL, orig_msg);
}

/* strip off the NS header */
static void strip_ns_hdr(struct msgb *msg)
{
	int strip_len = msgb_bssgph(msg) - msg->data;
	msgb_pull(msg, strip_len);
}

#if 0
/* feed a message down the NS-VC associated with the specified bvc */
static int gbprox_relay2sgsn(struct gbproxy_config *cfg, struct msgb *old_msg,
			     uint16_t ns_bvci, uint16_t sgsn_nsei)
{
	/* create a copy of the message so the old one can
	 * be free()d safely when we return from gbprox_rcvmsg() */
	struct gprs_ns2_inst *nsi = cfg->nsi;
	struct osmo_gprs_ns2_prim nsp = {};
	struct msgb *msg = bssgp_msgb_copy(old_msg, "msgb_relay2sgsn");
	int rc;

	DEBUGP(DGPRS, "NSE(%05u/BSS)-BVC(%05u) proxying BTS->SGSN  NSE(%05u/SGSN)\n",
		msgb_nsei(msg), ns_bvci, sgsn_nsei);

	nsp.bvci = ns_bvci;
	nsp.nsei = sgsn_nsei;

	strip_ns_hdr(msg);
	osmo_prim_init(&nsp.oph, SAP_NS, PRIM_NS_UNIT_DATA,
		       PRIM_OP_REQUEST, msg);
	rc = gprs_ns2_recv_prim(nsi, &nsp.oph);
	if (rc < 0)
		rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, GBPROX_GLOB_CTR_TX_ERR_SGSN));
	return rc;
}
#endif

/*! Determine the TLLI from the given BSSGP message.
 *  \param[in] bssgp pointer to start of BSSGP header
 *  \param[in] bssgp_len length of BSSGP message in octets
 *  \param[out] tlli TLLI (if any) in host byte order
 *  \returns 1 if TLLI found; 0 if none found; negative on parse error */
int gprs_gb_parse_tlli(const uint8_t *bssgp, size_t bssgp_len, uint32_t *tlli)
{
	const struct bssgp_normal_hdr *bgph;
	uint8_t pdu_type;

	if (bssgp_len < sizeof(struct bssgp_normal_hdr))
		return -EINVAL;

	bgph = (struct bssgp_normal_hdr *)bssgp;
	pdu_type = bgph->pdu_type;

	if (pdu_type == BSSGP_PDUT_UL_UNITDATA ||
	    pdu_type == BSSGP_PDUT_DL_UNITDATA) {
		const struct bssgp_ud_hdr *budh = (struct bssgp_ud_hdr *)bssgp;
		if (bssgp_len < sizeof(struct bssgp_ud_hdr))
			return -EINVAL;
		*tlli = osmo_load32be((const uint8_t *)&budh->tlli);
		return 1;
	} else {
		const uint8_t *data = bgph->data;
		size_t data_len = bssgp_len - sizeof(*bgph);
		struct tlv_parsed tp;

		if (bssgp_tlv_parse(&tp, data, data_len) < 0)
			return -EINVAL;

		if (TLVP_PRESENT(&tp, BSSGP_IE_TLLI)) {
			*tlli = osmo_load32be(TLVP_VAL(&tp, BSSGP_IE_TLLI));
			return 1;
		}
	}

	/* No TLLI present in message */
	return 0;
}

/* feed a message down the NSE */
static int gbprox_relay2nse(struct msgb *old_msg, struct gbproxy_nse *nse,
			     uint16_t ns_bvci)
{
	OSMO_ASSERT(nse);
	OSMO_ASSERT(nse->cfg);

	/* create a copy of the message so the old one can
	 * be free()d safely when we return from gbprox_rcvmsg() */
	struct gprs_ns2_inst *nsi = nse->cfg->nsi;
	struct msgb *msg = bssgp_msgb_copy(old_msg, "msgb_relay2nse");
	uint32_t tlli = 0;
	int rc;

	DEBUGP(DGPRS, "NSE(%05u/%s)-BVC(%05u/??) proxying to NSE(%05u/%s)\n", msgb_nsei(msg),
	       !nse->sgsn_facing ? "SGSN" : "BSS", ns_bvci, nse->nsei, nse->sgsn_facing ? "SGSN" : "BSS");

	/* Strip the old NS header, it will be replaced with a new one */
	strip_ns_hdr(msg);

	/* TS 48.018 Section 5.4.2: The link selector parameter is
	 * defined in 3GPP TS 48.016. At one side of the Gb interface,
	 * all BSSGP UNITDATA PDUs related to an MS shall be passed with
	 * the same LSP, e.g. the LSP contains the MS's TLLI, to the
	 * underlying network service. */
	gprs_gb_parse_tlli(msgb_data(msg), msgb_length(msg), &tlli);

	rc = bssgp2_nsi_tx_ptp(nsi, nse->nsei, ns_bvci, msg, tlli);
	/* FIXME: We need a counter group for gbproxy_nse */
	//if (rc < 0)
	//	rate_ctr_inc(rate_ctr_group_get_ctr(bvc->ctrg, GBPROX_PEER_CTR_TX_ERR));

	return rc;
}

/* feed a message down the NS-VC associated with the specified bvc */
static int gbprox_relay2peer(struct msgb *old_msg, struct gbproxy_bvc *bvc,
			     uint16_t ns_bvci)
{
	int rc;
	struct gbproxy_nse *nse = bvc->nse;
	OSMO_ASSERT(nse);

	rc = gbprox_relay2nse(old_msg, nse, ns_bvci);
	if (rc < 0)
		rate_ctr_inc(rate_ctr_group_get_ctr(bvc->ctrg, GBPROX_PEER_CTR_TX_ERR));

	return rc;
}

int bssgp_prim_cb(struct osmo_prim_hdr *oph, void *ctx)
{
	return 0;
}


/***********************************************************************
 * PTP BVC handling
 ***********************************************************************/

/* FIXME: Handle the tlli NULL case correctly,
 * This function should take a generic selector
 * and choose an sgsn based on that
 */
static struct gbproxy_sgsn *gbproxy_select_sgsn(struct gbproxy_config *cfg, const uint32_t *tlli)
{
	struct gbproxy_sgsn *sgsn = NULL;
	struct gbproxy_sgsn *sgsn_avoid = NULL;

	int tlli_type;
	int16_t nri;
	bool null_nri = false;

	if (!tlli) {
		sgsn = gbproxy_sgsn_by_available(cfg);
		if (!sgsn) {
			LOGP(DGPRS, LOGL_ERROR, "Could not find any available SGSN\n");
			return NULL;
		}
		LOGPSGSN(sgsn, LOGL_INFO, "Could not get TLLI, using first available SGSN\n");
		return sgsn;
	}

	if (cfg->pool.nri_bitlen == 0) {
		/* Pooling is disabled */
		sgsn = gbproxy_sgsn_by_available(cfg);
		if (!sgsn) {
			LOGP(DGPRS, LOGL_ERROR, "Could not find any available SGSN\n");
			return NULL;
		}

		LOGPSGSN(sgsn, LOGL_INFO, "Pooling disabled, using first available SGSN\n");
	} else {
		/* Pooling is enabled, try to use the NRI for routing to an SGSN
		 * See 3GPP TS 23.236 Ch. 5.3.2 */
		tlli_type = gprs_tlli_type(*tlli);
		if (tlli_type == TLLI_LOCAL || tlli_type == TLLI_FOREIGN) {
			/* Only get/use the NRI if tlli type is local */
			osmo_tmsi_nri_v_get(&nri, *tlli, cfg->pool.nri_bitlen);
			if (nri >= 0) {
				/* Get the SGSN for the NRI */
				sgsn = gbproxy_sgsn_by_nri(cfg, nri, &null_nri);
				if (sgsn && !null_nri)
					return sgsn;
				/* If the NRI is the null NRI, we need to avoid the chosen SGSN */
				if (null_nri && sgsn) {
					sgsn_avoid = sgsn;
				}
			} else {
				/* We couldn't get the NRI from the TLLI */
				LOGP(DGPRS, LOGL_ERROR, "Could not extract NRI from local TLLI %08x\n", *tlli);
			}
		} else {
			LOGP(DGPRS, LOGL_INFO, "TLLI %08x is neither local nor foreign, not routing by NRI\n", *tlli);
		}
	}

	/* If we haven't found an SGSN yet we need to choose one, but avoid the one in sgsn_avoid
	 * NOTE: This function is not stable if the number of SGSNs or allow_attach changes
	 * We could implement TLLI tracking here, but 3GPP TS 23.236 Ch. 5.3.2 (see NOTE) argues that
	 * we can just wait for the MS to reattempt the procedure.
	 */
	if (!sgsn)
		sgsn = gbproxy_sgsn_by_tlli(cfg, sgsn_avoid, *tlli);

	if (!sgsn) {
		LOGP(DGPRS, LOGL_ERROR, "No suitable SGSN found for TLLI %u\n", *tlli);
		return NULL;
	}

	return sgsn;
}

/*! Find the correct gbproxy_bvc given a cell and an SGSN
 *  \param[in] cfg The gbproxy configuration
 *  \param[in] cell The cell the message belongs to
 *  \param[in] tlli An optional TLLI used for tracking
 *  \return Returns 0 on success, otherwise a negative value
 */
static struct gbproxy_bvc *gbproxy_select_sgsn_bvc(struct gbproxy_config *cfg, struct gbproxy_cell *cell, const uint32_t *tlli)
{
	struct gbproxy_sgsn *sgsn;
	struct gbproxy_bvc *sgsn_bvc = NULL;
	int i;

	sgsn = gbproxy_select_sgsn(cfg, tlli);
	if (!sgsn) {
		LOGPCELL(cell, LOGL_ERROR, "Could not find any SGSN, dropping message!\n");
		return NULL;
	}

	/* Get the BVC for this SGSN/NSE */
	for (i = 0; i < ARRAY_SIZE(cell->sgsn_bvc); i++) {
		sgsn_bvc = cell->sgsn_bvc[i];
		if (!sgsn_bvc)
			continue;
		if (sgsn->nse != sgsn_bvc->nse)
			continue;

		return sgsn_bvc;
	}

	/* This shouldn't happen */
	LOGPCELL(cell, LOGL_ERROR, "Could not find matching BVC for SGSN %s, dropping message!\n", sgsn->name);
	return NULL;
}

/*! Send a message to the next SGSN, possibly ignoring the null SGSN
 *  route an uplink message on a PTP-BVC to a SGSN using the TLLI
 *  \param[in] cell The cell the message belongs to
 *  \param[in] msg The BSSGP message
 *  \param[in] null_sgsn If not NULL then avoid this SGSN (because this message contains its null NRI)
 *  \param[in] tlli An optional TLLI used for tracking
 *  \return Returns 0 on success, otherwise a negative value
 */
static int gbprox_bss2sgsn_tlli(struct gbproxy_cell *cell, struct msgb *msg, const uint32_t *tlli,
				bool sig_bvci)
{
	struct gbproxy_config *cfg = cell->cfg;
	struct gbproxy_bvc *sgsn_bvc;

	sgsn_bvc = gbproxy_select_sgsn_bvc(cfg, cell, tlli);
	if (!sgsn_bvc) {
		LOGPCELL(cell, LOGL_NOTICE, "Could not find any SGSN for TLLI %u, dropping message!\n", *tlli);
		return -EINVAL;
	}

	return gbprox_relay2peer(msg, sgsn_bvc, sig_bvci ? 0 : sgsn_bvc->bvci);
}

static int gbproxy_decode_bssgp(const struct bssgp_normal_hdr *bgph, int msg_len, struct tlv_parsed *tp, const char *log_pfx)
{
	int rc;

	/* UNITDATA PDUs have a different header than the other PDUs */
	if (bgph->pdu_type == BSSGP_PDUT_UL_UNITDATA || bgph->pdu_type == BSSGP_PDUT_DL_UNITDATA) {
		const struct bssgp_ud_hdr *budh = (struct bssgp_ud_hdr *) bgph;
		if (msg_len < sizeof(*budh))
			return OSMO_TLVP_ERR_MAND_IE_MISSING;
		rc = osmo_tlv_prot_parse(&osmo_pdef_bssgp, tp, 1, budh->pdu_type, budh->data,
					 msg_len - sizeof(*budh), 0, 0, DGPRS, log_pfx);
		/* populate TLLI from the fixed headser into the TLV-parsed array so later code
		 * doesn't have to worry where the TLLI came from */
		tp->lv[BSSGP_IE_TLLI].len = 4;
		tp->lv[BSSGP_IE_TLLI].val = (const uint8_t *) &budh->tlli;
	} else {
		rc = osmo_tlv_prot_parse(&osmo_pdef_bssgp, tp, 1, bgph->pdu_type, bgph->data,
					 msg_len - sizeof(*bgph), 0, 0, DGPRS, log_pfx);
	}

	return rc;
}

static int gbproxy_tlli_from_status_pdu(struct tlv_parsed *tp, uint32_t *tlli, char *log_pfx);

/* Receive an incoming PTP message from a BSS-side NS-VC */
static int gbprox_rx_ptp_from_bss(struct gbproxy_nse *nse, struct msgb *msg, uint16_t ns_bvci)
{
	struct bssgp_normal_hdr *bgph = (struct bssgp_normal_hdr *) msgb_bssgph(msg);
	const char *pdut_name = osmo_tlv_prot_msg_name(&osmo_pdef_bssgp, bgph->pdu_type);
	struct gbproxy_bvc *bss_bvc;
	struct tlv_parsed tp;
	char log_pfx[32];
	uint32_t tlli;
	int rc;

	snprintf(log_pfx, sizeof(log_pfx), "NSE(%05u/BSS)-BVC(%05u/??)", nse->nsei, ns_bvci);

	LOGP(DGPRS, LOGL_DEBUG, "%s Rx %s\n", log_pfx, pdut_name);

	if (ns_bvci == 0 || ns_bvci == 1) {
		LOGP(DGPRS, LOGL_NOTICE, "%s BVCI=%05u is not PTP\n", log_pfx, ns_bvci);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(bgph->pdu_type) & BSSGP_PDUF_PTP)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in PTP BVC\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(bgph->pdu_type) & BSSGP_PDUF_UL)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in uplink direction\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	bss_bvc = gbproxy_bvc_by_bvci(nse, ns_bvci);
	if (!bss_bvc) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s - Didn't find BVC for PTP message, discarding\n",
		     log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKNOWN_BVCI, &ns_bvci, msg);
	}

	rc = gbproxy_decode_bssgp(bgph, msgb_bssgp_len(msg), &tp, log_pfx);
	if (rc < 0) {
		rate_ctr_inc(rate_ctr_group_get_ctr(nse->cfg->ctrg, GBPROX_GLOB_CTR_PROTO_ERR_BSS));
		return tx_status_from_tlvp(nse, rc, msg);
	}
	/* hack to get both msg + tlv_parsed passed via osmo_fsm_inst_dispatch */
	msgb_bcid(msg) = (void *)&tp;

	switch (bgph->pdu_type) {
	case BSSGP_PDUT_UL_UNITDATA:
	case BSSGP_PDUT_RA_CAPA_UPDATE:
	case BSSGP_PDUT_FLOW_CONTROL_MS:
	case BSSGP_PDUT_DOWNLOAD_BSS_PFC:
	case BSSGP_PDUT_CREATE_BSS_PFC_ACK:
	case BSSGP_PDUT_CREATE_BSS_PFC_NACK:
	case BSSGP_PDUT_MODIFY_BSS_PFC_ACK:
	case BSSGP_PDUT_DELETE_BSS_PFC_ACK:
	case BSSGP_PDUT_FLOW_CONTROL_PFC:
	case BSSGP_PDUT_DELETE_BSS_PFC_REQ:
	case BSSGP_PDUT_PS_HO_REQUIRED:
	case BSSGP_PDUT_PS_HO_REQUEST_ACK:
	case BSSGP_PDUT_PS_HO_REQUEST_NACK:
	case BSSGP_PDUT_PS_HO_COMPLETE:
	case BSSGP_PDUT_PS_HO_CANCEL:
		/* We can route based on TLLI-NRI */
		tlli = osmo_load32be(TLVP_VAL(&tp, BSSGP_IE_TLLI));
		rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, &tlli, false);
		break;
	case BSSGP_PDUT_RADIO_STATUS:
		if (TLVP_PRESENT(&tp, BSSGP_IE_TLLI)) {
			tlli = osmo_load32be(TLVP_VAL(&tp, BSSGP_IE_TLLI));
			rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, &tlli, false);
		} else if (TLVP_PRESENT(&tp, BSSGP_IE_TMSI)) {
			/* we treat the TMSI like a TLLI and extract the NRI from it */
			tlli = osmo_load32be(TLVP_VAL(&tp, BSSGP_IE_TMSI));
			/* Convert the TMSI into a FOREIGN TLLI so it is routed appropriately */
			tlli = gprs_tmsi2tlli(tlli, TLLI_FOREIGN);
			rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, &tlli, false);
		} else if (TLVP_PRESENT(&tp, BSSGP_IE_IMSI)) {
			/* FIXME: Use the IMSI as selector? */
			rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, NULL, false);
		} else
			LOGPBVC(bss_bvc, LOGL_ERROR, "Rx RADIO-STATUS without any of the conditional IEs\n");
		break;
	case BSSGP_PDUT_DUMMY_PAGING_PS_RESP:
	case BSSGP_PDUT_PAGING_PS_REJECT:
	{
		/* Route according to IMSI<->NSE cache entry */
		struct osmo_mobile_identity mi;
		const uint8_t *mi_data = TLVP_VAL(&tp, BSSGP_IE_IMSI);
		uint8_t mi_len = TLVP_LEN(&tp, BSSGP_IE_IMSI);
		osmo_mobile_identity_decode(&mi, mi_data, mi_len, false);
		nse = gbproxy_nse_by_imsi(nse->cfg, mi.imsi, CACHE_USAGE_PAGING);
		if (nse) {
			OSMO_ASSERT(nse->sgsn_facing);
			rc = gbprox_relay2nse(msg, nse, ns_bvci);
		} else {
			LOGPBVC(bss_bvc, LOGL_ERROR, "Rx unmatched %s with IMSI %s\n", pdut_name, mi.imsi);
		}
		break;
	}
	case BSSGP_PDUT_FLOW_CONTROL_BVC:
		osmo_fsm_inst_dispatch(bss_bvc->fi, BSSGP_BVCFSM_E_RX_FC_BVC, msg);
		break;
	case BSSGP_PDUT_STATUS:
	{
		struct gbproxy_sgsn *sgsn;
		/* Check if the status needs to be terminated locally */
		uint8_t cause = *TLVP_VAL(&tp, BSSGP_IE_CAUSE);

		LOGPNSE(nse, LOGL_NOTICE, "Rx STATUS cause=0x%02x(%s)\n", cause,
			bssgp_cause_str(cause));

		if (gbproxy_tlli_from_status_pdu(&tp, &tlli, log_pfx) == 0)
			sgsn = gbproxy_select_sgsn(nse->cfg, &tlli);
		else
			sgsn = gbproxy_select_sgsn(nse->cfg, NULL);

		if (!sgsn) {
			rc = -EINVAL;
			break;
		}

		rc = gbprox_relay2nse(msg, sgsn->nse, ns_bvci);
		break;
	}
	}

	return 0;
}

/* Receive an incoming PTP message from a SGSN-side NS-VC */
static int gbprox_rx_ptp_from_sgsn(struct gbproxy_nse *nse, struct msgb *msg, uint16_t ns_bvci)
{
	struct bssgp_normal_hdr *bgph = (struct bssgp_normal_hdr *) msgb_bssgph(msg);
	const char *pdut_name = osmo_tlv_prot_msg_name(&osmo_pdef_bssgp, bgph->pdu_type);
	struct gbproxy_bvc *sgsn_bvc, *bss_bvc;
	struct tlv_parsed tp;
	char log_pfx[32];
	int rc;

	snprintf(log_pfx, sizeof(log_pfx), "NSE(%05u/SGSN)-BVC(%05u/??)", nse->nsei, ns_bvci);

	LOGP(DGPRS, LOGL_DEBUG, "%s Rx %s\n", log_pfx, pdut_name);

	if (ns_bvci == 0 || ns_bvci == 1) {
		LOGP(DGPRS, LOGL_NOTICE, "%s BVCI is not PTP\n", log_pfx);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(bgph->pdu_type) & BSSGP_PDUF_PTP)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in PTP BVC\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(bgph->pdu_type) & BSSGP_PDUF_DL)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in downlink direction\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	sgsn_bvc = gbproxy_bvc_by_bvci(nse, ns_bvci);
	if (!sgsn_bvc) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s - Didn't find BVC for for PTP message, discarding\n",
		     log_pfx, pdut_name);
		rate_ctr_inc(rate_ctr_group_get_ctr(nse->cfg->ctrg, GBPROX_GLOB_CTR_INV_BVCI));
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKNOWN_BVCI, &ns_bvci, msg);
	}

	if (!bssgp_bvc_fsm_is_unblocked(sgsn_bvc->fi)) {
		LOGPBVC(sgsn_bvc, LOGL_NOTICE, "Rx %s: Dropping on blocked BVC\n", pdut_name);
		rate_ctr_inc(rate_ctr_group_get_ctr(sgsn_bvc->ctrg, GBPROX_PEER_CTR_DROPPED));
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_BVCI_BLOCKED, &ns_bvci, msg);
	}

	rc = gbproxy_decode_bssgp(bgph, msgb_bssgp_len(msg), &tp, log_pfx);
	if (rc < 0) {
		rate_ctr_inc(rate_ctr_group_get_ctr(nse->cfg->ctrg, GBPROX_GLOB_CTR_PROTO_ERR_SGSN));
		return tx_status_from_tlvp(nse, rc, msg);
	}
	/* hack to get both msg + tlv_parsed passed via osmo_fsm_inst_dispatch */
	msgb_bcid(msg) = (void *)&tp;

	OSMO_ASSERT(sgsn_bvc->cell);
	bss_bvc = sgsn_bvc->cell->bss_bvc;

	switch (bgph->pdu_type) {
	case BSSGP_PDUT_FLOW_CONTROL_BVC_ACK:
		return osmo_fsm_inst_dispatch(sgsn_bvc->fi, BSSGP_BVCFSM_E_RX_FC_BVC_ACK, msg);
	case BSSGP_PDUT_DUMMY_PAGING_PS:
	case BSSGP_PDUT_PAGING_PS:
	{
		/* Cache the IMSI<->NSE to route PAGING REJECT */
		struct osmo_mobile_identity mi;
		const uint8_t *mi_data = TLVP_VAL(&tp, BSSGP_IE_IMSI);
		uint8_t mi_len = TLVP_LEN(&tp, BSSGP_IE_IMSI);
		osmo_mobile_identity_decode(&mi, mi_data, mi_len, false);
		gbproxy_imsi_cache_update(nse, mi.imsi, CACHE_USAGE_PAGING);
		break;
	}
	default:
		break;
	}
	return gbprox_relay2peer(msg, bss_bvc, bss_bvc->bvci);

}

/***********************************************************************
 * BVC FSM call-backs
 ***********************************************************************/

/* helper function to dispatch a FSM event to all SGSN-side BVC FSMs of a cell */
static void dispatch_to_all_sgsn_bvc(struct gbproxy_cell *cell, uint32_t event, void *priv)
{
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(cell->sgsn_bvc); i++) {
		struct gbproxy_bvc *sgsn_bvc = cell->sgsn_bvc[i];
		if (!sgsn_bvc)
			continue;
		osmo_fsm_inst_dispatch(sgsn_bvc->fi, event, priv);
	}
}

/* BVC FSM informs us about a BSS-side reset of the signaling BVC */
static void bss_sig_bvc_reset_notif(uint16_t nsei, uint16_t bvci, const struct gprs_ra_id *ra_id,
				    uint16_t cell_id, uint8_t cause, void *priv)
{
	struct gbproxy_bvc *sig_bvc = priv;
	struct gbproxy_nse *nse = sig_bvc->nse;
	struct gbproxy_bvc *ptp_bvc;
	unsigned int i;

	/* BLOCK all SGSN-side PTP BVC within this NSE */
	hash_for_each(nse->bvcs, i, ptp_bvc, list) {
		if (ptp_bvc == sig_bvc)
			continue;
		OSMO_ASSERT(ptp_bvc->cell);

		dispatch_to_all_sgsn_bvc(ptp_bvc->cell, BSSGP_BVCFSM_E_REQ_BLOCK, &cause);
	}

	/* Delete all BSS-side PTP BVC within this NSE */
	gbproxy_cleanup_bvcs(nse, 0);

	/* TODO: we keep the "CELL" around for now, re-connecting it to
	 * any (later) new PTP-BVC for that BVCI. Not sure if that's the
	 * best idea ? */
}

/* forward declaration */
static const struct bssgp_bvc_fsm_ops sgsn_ptp_bvc_fsm_ops;

static const struct bssgp_bvc_fsm_ops bss_sig_bvc_fsm_ops = {
	.reset_notification = bss_sig_bvc_reset_notif,
};

/* BVC FSM informs us about a BSS-side reset of a PTP BVC */
static void bss_ptp_bvc_reset_notif(uint16_t nsei, uint16_t bvci, const struct gprs_ra_id *ra_id,
				    uint16_t cell_id, uint8_t cause, void *priv)
{
	struct gbproxy_bvc *bvc = priv;
	struct gbproxy_config *cfg = bvc->nse->cfg;
	struct gbproxy_nse *sgsn_nse;
	unsigned int i;

	OSMO_ASSERT(bvci != 0);

	if (!bvc->cell) {
		/* see if we have a CELL dangling around */
		bvc->cell = gbproxy_cell_by_bvci(cfg, bvci);
		if (bvc->cell) {
			/* the CELL already exists. This means either it * was created before at an
			 * earlier PTP BVC-RESET, or that there are non-unique BVCIs and hence a
			 * malconfiguration */
			if (bvc->cell->bss_bvc) {
				LOGPBVC(bvc, LOGL_NOTICE, "Rx BVC-RESET via this NSE, but CELL already "
					"has BVC on NSEI=%05u\n", bvc->cell->bss_bvc->nse->nsei);
				LOGPBVC(bvc->cell->bss_bvc, LOGL_NOTICE, "Destroying due to conflicting "
					"BVCI configuration (new NSEI=%05u)!\n", bvc->nse->nsei);
				gbproxy_bvc_free(bvc->cell->bss_bvc);
				bvc->cell = NULL;
			} else {
				LOGPBVC(bvc, LOGL_ERROR, "Found cell without BSS BVC, this should not happen!");
			}
		}
	}

	if (!bvc->cell) {
		/* if we end up here, it means this is the first time we received a BVC-RESET
		 * for this BVC.  We need to create the 'cell' data structure and the SGSN-side
		 * BVC counterparts */

		bvc->cell = gbproxy_cell_alloc(cfg, bvci, ra_id, cell_id);
		OSMO_ASSERT(bvc->cell);

		/* link us to the cell and vice-versa */
		bvc->cell->bss_bvc = bvc;
	}

	/* Ensure we have the correct RA/CELL ID */
	if (!gsm48_ra_equal(&bvc->cell->id.raid, ra_id)) {
		LOGPBVC(bvc, LOGL_NOTICE, "RAID changed from %s to %s, updating cell\n", osmo_rai_name(&bvc->cell->id.raid), osmo_rai_name(ra_id));
		memcpy(&bvc->cell->id.raid, ra_id, sizeof(*ra_id));
	}
	if (bvc->cell->id.cid != cell_id) {
		LOGPBVC(bvc, LOGL_NOTICE, "CellID changed from %05d to %05d, updating cell\n", bvc->cell->id.cid, cell_id);
		bvc->cell->id.cid = cell_id;
	}

	/* Reallocate SGSN-side BVCs of the cell, and reset them
	 * Removing and reallocating is needed because the ra_id/cell_id might have changed */
	hash_for_each(cfg->sgsn_nses, i, sgsn_nse, list) {
		struct gbproxy_bvc *sgsn_bvc = gbproxy_bvc_by_bvci(sgsn_nse, bvci);
		if (!sgsn_bvc)
			sgsn_bvc = gbproxy_bvc_by_bvci_inactive(sgsn_nse, bvci);
		if (sgsn_bvc)
			gbproxy_bvc_free(sgsn_bvc);

		sgsn_bvc = gbproxy_bvc_alloc(sgsn_nse, bvci);
		OSMO_ASSERT(sgsn_bvc);
		sgsn_bvc->cell = bvc->cell;
		sgsn_bvc->fi = bssgp_bvc_fsm_alloc_ptp_bss(sgsn_bvc, cfg->nsi, sgsn_nse->nsei,
							   bvci, ra_id, cell_id);
		OSMO_ASSERT(sgsn_bvc->fi);
		bssgp_bvc_fsm_set_max_pdu_len(sgsn_bvc->fi, sgsn_nse->max_sdu_len);
		bssgp_bvc_fsm_set_ops(sgsn_bvc->fi, &sgsn_ptp_bvc_fsm_ops, sgsn_bvc);
		gbproxy_cell_add_sgsn_bvc(bvc->cell, sgsn_bvc);
	}

	/* Trigger outbound BVC-RESET procedure toward each SGSN */
	dispatch_to_all_sgsn_bvc(bvc->cell, BSSGP_BVCFSM_E_REQ_RESET, &cause);
}

/* BVC FSM informs us about a BSS-side FSM state change */
static void bss_ptp_bvc_state_chg_notif(uint16_t nsei, uint16_t bvci, int old_state, int state, void *priv)
{
	struct gbproxy_bvc *bvc = priv;
	struct gbproxy_cell *cell = bvc->cell;
	uint8_t cause = bssgp_bvc_fsm_get_block_cause(bvc->fi);

	/* we have just been created but due to callback ordering the cell is not associated */
	if (!cell)
		return;

	switch (state) {
	case BSSGP_BVCFSM_S_BLOCKED:
		/* block the corresponding SGSN-side PTP BVCs */
		dispatch_to_all_sgsn_bvc(cell, BSSGP_BVCFSM_E_REQ_BLOCK, &cause);
		break;
	case BSSGP_BVCFSM_S_UNBLOCKED:
		/* unblock the corresponding SGSN-side PTP BVCs */
		dispatch_to_all_sgsn_bvc(cell, BSSGP_BVCFSM_E_REQ_UNBLOCK, NULL);
		break;
	}
}

/* BVC FSM informs us about BVC-FC PDU receive */
static void bss_ptp_bvc_fc_bvc(uint16_t nsei, uint16_t bvci, const struct bssgp2_flow_ctrl *fc, void *priv)
{
	struct bssgp2_flow_ctrl fc_reduced;
	struct gbproxy_bvc *bss_bvc = priv;
	struct gbproxy_cell *cell;
	struct gbproxy_config *cfg;

	OSMO_ASSERT(bss_bvc);
	OSMO_ASSERT(fc);

	cell = bss_bvc->cell;
	if (!cell)
		return;

	cfg = cell->cfg;

	/* reduce / scale according to configuration to make sure we only advertise a fraction
	 * of the capacity to each of the SGSNs in the pool */
	fc_reduced = *fc;
	fc_reduced.bucket_size_max = (fc->bucket_size_max * cfg->pool.bvc_fc_ratio) / 100;
	fc_reduced.bucket_leak_rate = (fc->bucket_leak_rate * cfg->pool.bvc_fc_ratio) / 100;
	/* we don't modify the per-MS related values as any single MS is only served by one SGSN */

	dispatch_to_all_sgsn_bvc(cell, BSSGP_BVCFSM_E_REQ_FC_BVC, (void *) &fc_reduced);
}

static const struct bssgp_bvc_fsm_ops bss_ptp_bvc_fsm_ops = {
	.reset_notification = bss_ptp_bvc_reset_notif,
	.state_chg_notification = bss_ptp_bvc_state_chg_notif,
	.rx_fc_bvc = bss_ptp_bvc_fc_bvc,
};

/* BVC FSM informs us about a SGSN-side reset of a PTP BVC */
static void sgsn_ptp_bvc_reset_notif(uint16_t nsei, uint16_t bvci, const struct gprs_ra_id *ra_id,
				     uint16_t cell_id, uint8_t cause, void *priv)
{
	struct gbproxy_bvc *bvc = priv;

	if (!bvc->cell) {
		LOGPBVC(bvc, LOGL_ERROR, "RESET of PTP BVC on SGSN side for which we have no BSS?\n");
		return;
	}

	OSMO_ASSERT(bvc->cell->bss_bvc);

	/* request reset of BSS-facing PTP-BVC */
	osmo_fsm_inst_dispatch(bvc->cell->bss_bvc->fi, BSSGP_BVCFSM_E_REQ_RESET, &cause);
}

static const struct bssgp_bvc_fsm_ops sgsn_ptp_bvc_fsm_ops = {
	.reset_notification = sgsn_ptp_bvc_reset_notif,
};

/* BVC FSM informs us about a SGSN-side reset of the signaling BVC */
static void sgsn_sig_bvc_reset_notif(uint16_t nsei, uint16_t bvci, const struct gprs_ra_id *ra_id,
				     uint16_t cell_id, uint8_t cause, void *priv)
{
	struct gbproxy_bvc *bvc = priv;
	struct gbproxy_config *cfg = bvc->nse->cfg;
	struct gbproxy_nse *bss_nse;
	unsigned int i;

	/* delete all SGSN-side PTP BVC for this SGSN */
	gbproxy_cleanup_bvcs(bvc->nse, 0);
	/* FIXME: what to do about the cells? */
	/* FIXME: do we really want to RESET all signaling BVC on the BSS and affect all other SGSN? */

	/* we need to trigger generating a reset procedure towards each BSS side signaling BVC */
	hash_for_each(cfg->bss_nses, i, bss_nse, list) {
		struct gbproxy_bvc *bss_bvc = gbproxy_bvc_by_bvci(bss_nse, 0);
		if (!bss_bvc) {
			LOGPNSE(bss_nse, LOGL_ERROR, "Doesn't have BVC with BVCI=0 ?!?\n");
			continue;
		}
		osmo_fsm_inst_dispatch(bss_bvc->fi, BSSGP_BVCFSM_E_REQ_RESET, &cause);
	}
}

const struct bssgp_bvc_fsm_ops sgsn_sig_bvc_fsm_ops = {
	.reset_notification = sgsn_sig_bvc_reset_notif,
};

/***********************************************************************
 * Signaling BVC handling
 ***********************************************************************/

/* process a BVC-RESET message from the BSS side */
static int rx_bvc_reset_from_bss(struct gbproxy_nse *nse, struct msgb *msg, struct tlv_parsed *tp)
{
	struct gbproxy_bvc *from_bvc = NULL;
	uint16_t bvci = ntohs(tlvp_val16_unal(tp, BSSGP_IE_BVCI));
	uint32_t features = 0; // FIXME: make configurable

	LOGPNSE(nse, LOGL_INFO, "Rx BVC-RESET (BVCI=%05u)\n", bvci);

	if (bvci == 0) {
		/* If we receive a BVC reset on the signalling endpoint, we
		 * don't want the SGSN to reset, as the signalling endpoint
		 * is common for all point-to-point BVCs (and thus all BTS) */

		from_bvc = gbproxy_bvc_by_bvci(nse, 0);
		if (!from_bvc) {
			from_bvc = gbproxy_bvc_alloc(nse, 0);
			OSMO_ASSERT(from_bvc);
			from_bvc->fi = bssgp_bvc_fsm_alloc_sig_sgsn(from_bvc, nse->cfg->nsi, nse->nsei, features);
			if (!from_bvc->fi) {
				LOGPNSE(nse, LOGL_ERROR, "Cannot allocate SIG-BVC FSM\n");
				gbproxy_bvc_free(from_bvc);
				return -ENOMEM;
			}
			bssgp_bvc_fsm_set_max_pdu_len(from_bvc->fi, nse->max_sdu_len);
			bssgp_bvc_fsm_set_ops(from_bvc->fi, &bss_sig_bvc_fsm_ops, from_bvc);
		}
	} else {
		from_bvc = gbproxy_bvc_by_bvci(nse, bvci);
		if (!from_bvc) {
			/* if a PTP-BVC is reset, and we don't know that
			 * PTP-BVCI yet, we should allocate a new bvc */
			from_bvc = gbproxy_bvc_alloc(nse, bvci);
			OSMO_ASSERT(from_bvc);
			from_bvc->fi = bssgp_bvc_fsm_alloc_ptp_sgsn(from_bvc, nse->cfg->nsi,
								    nse->nsei, bvci);
			if (!from_bvc->fi) {
				LOGPNSE(nse, LOGL_ERROR, "Cannot allocate SIG-BVC FSM\n");
				gbproxy_bvc_free(from_bvc);
				return -ENOMEM;
			}
			bssgp_bvc_fsm_set_max_pdu_len(from_bvc->fi, nse->max_sdu_len);
			bssgp_bvc_fsm_set_ops(from_bvc->fi, &bss_ptp_bvc_fsm_ops, from_bvc);
		}
	}
	/* hand into FSM for further processing */
	osmo_fsm_inst_dispatch(from_bvc->fi, BSSGP_BVCFSM_E_RX_RESET, msg);
	return 0;
}

/* Receive an incoming RIM message from a BSS-side NS-VC */
static int gbprox_rx_rim_from_bss(struct tlv_parsed *tp, struct gbproxy_nse *nse, struct msgb *msg, char *log_pfx,
				  const char *pdut_name)
{
	struct gbproxy_sgsn *sgsn;
	struct gbproxy_cell *dest_cell;
	struct gbproxy_cell *src_cell;
	struct bssgp_rim_routing_info dest_ri;
	struct bssgp_rim_routing_info src_ri;
	int rc;
	char ri_src_str[64];
	char ri_dest_str[64];
	uint16_t ns_bvci = msgb_bvci(msg);

	rc = bssgp_parse_rim_ri(&dest_ri, TLVP_VAL(&tp[0], BSSGP_IE_RIM_ROUTING_INFO),
				TLVP_LEN(&tp[0], BSSGP_IE_RIM_ROUTING_INFO));
	if (rc < 0) {
		LOGP(DGPRS, LOGL_ERROR, "%s %s cannot parse destination RIM routing info\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
	}
	rc = bssgp_parse_rim_ri(&src_ri, TLVP_VAL(&tp[1], BSSGP_IE_RIM_ROUTING_INFO),
				TLVP_LEN(&tp[1], BSSGP_IE_RIM_ROUTING_INFO));
	if (rc < 0) {
		LOGP(DGPRS, LOGL_ERROR, "%s %s cannot parse source RIM routing info\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
	}

	/* Since gbproxy is 2G only we do not expect to get RIM messages only from GERAN cells. */
	if (src_ri.discr != BSSGP_RIM_ROUTING_INFO_GERAN) {
		LOGP(DGPRS, LOGL_ERROR, "%s %s source RIM routing info is not GERAN (%s)\n", log_pfx, pdut_name,
		     bssgp_rim_ri_name(&src_ri));
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
	}

	/* Lookup source cell to make sure that the source RIM routing information actually belongs
	 * to a valid cell that we know */
	src_cell = gbproxy_cell_by_cellid(nse->cfg, &src_ri.geran.raid, src_ri.geran.cid);
	if (!src_cell) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s cannot find cell for source RIM routing info (%s)\n", log_pfx,
		     pdut_name, bssgp_rim_ri_name(&src_ri));
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
	}

	/* TODO: Use bssgp_bvc_get_features_negotiated(src_cell->bss_bvc->fi) to check if the the BSS sided BVC actually
	 * did negotiate RIM support. If not we should respond with a BSSGP STATUS message. The cause code should be
	 * BSSGP_CAUSE_PDU_INCOMP_FEAT. */

	/* If Destination is known by gbproxy, route directly */
	if (dest_ri.discr == BSSGP_RIM_ROUTING_INFO_GERAN) {
		dest_cell = gbproxy_cell_by_cellid(nse->cfg, &dest_ri.geran.raid, dest_ri.geran.cid);
		if (dest_cell) {
			/* TODO: Also check if dest_cell->bss_bvc is RIM-capable (see also above). If not we should
			 * respond with a BSSGP STATUS message as well because it also would make no sense to try
			 * routing the RIM message to the next RIM-capable SGSN. */
			LOGP(DLBSSGP, LOGL_DEBUG, "%s %s relaying to peer (nsei=%u) RIM-PDU: src=%s, dest=%s\n",
			     log_pfx, pdut_name, dest_cell->bss_bvc->nse->nsei,
			     bssgp_rim_ri_name_buf(ri_src_str, sizeof(ri_src_str), &src_ri),
			     bssgp_rim_ri_name_buf(ri_dest_str, sizeof(ri_dest_str), &dest_ri));
			return gbprox_relay2peer(msg, dest_cell->bss_bvc, 0);
		}
	}

	/* Otherwise pass on to a RIM-capable SGSN */
	/* TODO: We need to extend gbproxy_select_sgsn() so that it selects a RIM-capable SGSN, at the moment we just
	 * get any SGSN and just assume that it is RIM-capable. */
	sgsn = gbproxy_select_sgsn(nse->cfg, NULL);
	if (!sgsn) {
		LOGP(DGPRS, LOGL_NOTICE,
		     "%s %s cannot route RIM message (%s to %s) since no RIM capable SGSN is found!\n", log_pfx,
		     pdut_name, bssgp_rim_ri_name(&src_ri), bssgp_rim_ri_name(&dest_ri));
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
	}
	LOGP(DLBSSGP, LOGL_DEBUG, "%s %s relaying to SGSN(%05u/%s) RIM-PDU: src=%s, dest=%s\n",
	     log_pfx, pdut_name, sgsn->nse->nsei, sgsn->name,
	     bssgp_rim_ri_name_buf(ri_src_str, sizeof(ri_src_str), &src_ri),
	     bssgp_rim_ri_name_buf(ri_dest_str, sizeof(ri_dest_str), &dest_ri));

	return gbprox_relay2nse(msg, sgsn->nse, 0);
}

/* Extract the TLLI from the PDU-in-error of the STATUS PDU (if available) */
static int gbproxy_tlli_from_status_pdu(struct tlv_parsed *tp, uint32_t *tlli, char *log_pfx)
{
	int rc;
	int pdu_len = TLVP_LEN(&tp[0], BSSGP_IE_PDU_IN_ERROR);
	const uint8_t *pdu_data = TLVP_VAL(&tp[0], BSSGP_IE_PDU_IN_ERROR);
	struct bssgp_normal_hdr *bgph = (struct bssgp_normal_hdr *)pdu_data;
	struct tlv_parsed tp_inner;

	rc = gbproxy_decode_bssgp(bgph, pdu_len, &tp_inner, log_pfx);
	/* Ignore decode failure due to truncated message */
	if (rc < 0 && rc != OSMO_TLVP_ERR_OFS_BEYOND_BUFFER)
		return rc;

	if (TLVP_PRESENT(&tp_inner, BSSGP_IE_TLLI)) {
		*tlli = osmo_load32be(TLVP_VAL(&tp_inner, BSSGP_IE_TLLI));
	} else if (TLVP_PRESENT(&tp_inner, BSSGP_IE_TMSI)) {
		/* we treat the TMSI like a TLLI and extract the NRI from it */
		*tlli = osmo_load32be(TLVP_VAL(&tp_inner, BSSGP_IE_TMSI));
		/* Convert the TMSI into a FOREIGN TLLI so it is routed appropriately */
		*tlli = gprs_tmsi2tlli(*tlli, TLLI_FOREIGN);
	} else {
		return -ENOENT;
	}

	return 0;
}

/* Extract the BVCI from the PDU-in-error of the STATUS PDU (if available) */
static int gbproxy_bvci_from_status_pdu(struct tlv_parsed *tp, uint16_t *bvci, char *log_pfx)
{
	int rc;
	int pdu_len = TLVP_LEN(&tp[0], BSSGP_IE_PDU_IN_ERROR);
	const uint8_t *pdu_data = TLVP_VAL(&tp[0], BSSGP_IE_PDU_IN_ERROR);
	struct bssgp_normal_hdr *bgph = (struct bssgp_normal_hdr *)pdu_data;
	struct tlv_parsed tp_inner;

	rc = gbproxy_decode_bssgp(bgph, pdu_len, &tp_inner, log_pfx);
	/* Ignore decode failure due to truncated message */
	if (rc < 0 && rc != OSMO_TLVP_ERR_OFS_BEYOND_BUFFER)
		return rc;

	if (TLVP_PRESENT(&tp_inner, BSSGP_IE_BVCI))
		*bvci = ntohs(tlvp_val16_unal(&tp_inner, BSSGP_IE_BVCI));
	else
		return -ENOENT;

	return 0;
}

/* Receive an incoming signalling message from a BSS-side NS-VC */
static int gbprox_rx_sig_from_bss(struct gbproxy_nse *nse, struct msgb *msg, uint16_t ns_bvci)
{
	struct bssgp_normal_hdr *bgph = (struct bssgp_normal_hdr *) msgb_bssgph(msg);
	uint8_t pdu_type = bgph->pdu_type;
	const char *pdut_name = osmo_tlv_prot_msg_name(&osmo_pdef_bssgp, bgph->pdu_type);
	struct tlv_parsed tp[2];
	int data_len = msgb_bssgp_len(msg) - sizeof(*bgph);
	struct gbproxy_bvc *from_bvc = NULL;
	char log_pfx[32];
	uint16_t ptp_bvci;
	uint32_t tlli;
	int rc;

	snprintf(log_pfx, sizeof(log_pfx), "NSE(%05u/BSS)-BVC(%05u/??)", nse->nsei, ns_bvci);

	LOGP(DGPRS, LOGL_DEBUG, "%s Rx %s\n", log_pfx, pdut_name);

	if (ns_bvci != 0 && ns_bvci != 1) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s BVCI=%05u is not signalling\n", log_pfx, pdut_name, ns_bvci);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(pdu_type) & BSSGP_PDUF_SIG)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in signalling BVC\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(pdu_type) & BSSGP_PDUF_UL)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in uplink direction\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	rc = osmo_tlv_prot_parse(&osmo_pdef_bssgp, tp, ARRAY_SIZE(tp), pdu_type, bgph->data, data_len, 0, 0,
				 DGPRS, log_pfx);
	if (rc < 0) {
		rate_ctr_inc(rate_ctr_group_get_ctr(nse->cfg->ctrg, GBPROX_GLOB_CTR_PROTO_ERR_BSS));
		return tx_status_from_tlvp(nse, rc, msg);
	}
	/* hack to get both msg + tlv_parsed passed via osmo_fsm_inst_dispatch */
	msgb_bcid(msg) = (void *)tp;

	/* special case handling for some PDU types */
	switch (pdu_type) {
	case BSSGP_PDUT_BVC_RESET:
		/* resolve or create gbproxy_bvc + handlei n BVC-FSM */
		return rx_bvc_reset_from_bss(nse, msg, &tp[0]);
	case BSSGP_PDUT_BVC_RESET_ACK:
		ptp_bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		from_bvc = gbproxy_bvc_by_bvci(nse, ptp_bvci);
		if (!from_bvc)
			goto err_no_bvc;
		return osmo_fsm_inst_dispatch(from_bvc->fi, BSSGP_BVCFSM_E_RX_RESET_ACK, msg);
	case BSSGP_PDUT_BVC_BLOCK:
		ptp_bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		from_bvc = gbproxy_bvc_by_bvci(nse, ptp_bvci);
		if (!from_bvc)
			goto err_no_bvc;
		return osmo_fsm_inst_dispatch(from_bvc->fi, BSSGP_BVCFSM_E_RX_BLOCK, msg);
	case BSSGP_PDUT_BVC_UNBLOCK:
		ptp_bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		from_bvc = gbproxy_bvc_by_bvci(nse, ptp_bvci);
		if (!from_bvc)
			goto err_no_bvc;
		return osmo_fsm_inst_dispatch(from_bvc->fi, BSSGP_BVCFSM_E_RX_UNBLOCK, msg);
	case BSSGP_PDUT_SUSPEND:
	case BSSGP_PDUT_RESUME:
	{
		struct gbproxy_sgsn *sgsn;

		tlli = osmo_load32be(TLVP_VAL(&tp[0], BSSGP_IE_TLLI));
		sgsn = gbproxy_select_sgsn(nse->cfg, &tlli);
		if (!sgsn) {
			LOGP(DGPRS, LOGL_ERROR, "Could not find any SGSN for TLLI, dropping message!\n");
			rc = -EINVAL;
			break;
		}

		gbproxy_tlli_cache_update(nse, tlli);

		rc = gbprox_relay2nse(msg, sgsn->nse, 0);
#if 0
		/* TODO: Validate the RAI for consistency with the RAI
		 * we expect for any of the BVC within this BSS side NSE */
		memcpy(ra, TLVP_VAL(&tp[0], BSSGP_IE_ROUTEING_AREA), sizeof(from_bvc->ra));
		gsm48_parse_ra(&raid, from_bvc->ra);
#endif
		break;
	}
	case BSSGP_PDUT_STATUS:
	{
		struct gbproxy_sgsn *sgsn;
		/* Check if the status needs to be terminated locally */
		uint8_t cause = *TLVP_VAL(&tp[0], BSSGP_IE_CAUSE);

		if (cause == BSSGP_CAUSE_UNKNOWN_BVCI || cause == BSSGP_CAUSE_BVCI_BLOCKED) {
			/* Log and handle locally */
			ptp_bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
			LOGPNSE(nse, LOGL_ERROR, "Rx STATUS cause=0x%02x(%s) for PtP-BVC %05u\n", cause,
				bssgp_cause_str(cause), ptp_bvci);
			/* FIXME: Remove/block our BVC if present? */
			break;
		}

		LOGPNSE(nse, LOGL_NOTICE, "Rx STATUS cause=0x%02x(%s) ", cause,
			bssgp_cause_str(cause));

		if (gbproxy_tlli_from_status_pdu(tp, &tlli, log_pfx) == 0)
			sgsn = gbproxy_select_sgsn(nse->cfg, &tlli);
		else
			sgsn = gbproxy_select_sgsn(nse->cfg, NULL);

		if (!sgsn) {
			rc = -EINVAL;
			break;
		}

		rc = gbprox_relay2nse(msg, sgsn->nse, 0);
		break;
	}
	case BSSGP_PDUT_RAN_INFO:
	case BSSGP_PDUT_RAN_INFO_REQ:
	case BSSGP_PDUT_RAN_INFO_ACK:
	case BSSGP_PDUT_RAN_INFO_ERROR:
	case BSSGP_PDUT_RAN_INFO_APP_ERROR:
		rc = gbprox_rx_rim_from_bss(tp, nse, msg, log_pfx, pdut_name);
		break;
	case BSSGP_PDUT_LLC_DISCARD:
		/* route based on BVCI + TLLI */
		ptp_bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		tlli = osmo_load32be(TLVP_VAL(&tp[0], BSSGP_IE_TLLI));
		from_bvc = gbproxy_bvc_by_bvci(nse, ptp_bvci);
		if (!from_bvc)
			goto err_no_bvc;
		rc = gbprox_bss2sgsn_tlli(from_bvc->cell, msg, &tlli, true);
		break;
	case BSSGP_PDUT_FLUSH_LL_ACK:
	{
		/* Route based on TLLI */
		tlli = osmo_load32be(TLVP_VAL(&tp[0], BSSGP_IE_TLLI));
		struct gbproxy_sgsn *sgsn = gbproxy_select_sgsn(nse->cfg, &tlli);
		if (!sgsn) {
			rc = -EINVAL;
			break;
		}

		rc = gbprox_relay2nse(msg, sgsn->nse, 0);
		break;
	}
	case BSSGP_PDUT_PAGING_PS_REJECT:
	case BSSGP_PDUT_DUMMY_PAGING_PS_RESP:
	{
		/* Route according to IMSI<->NSE cache entry */
		struct osmo_mobile_identity mi;
		const uint8_t *mi_data = TLVP_VAL(&tp[0], BSSGP_IE_IMSI);
		uint8_t mi_len = TLVP_LEN(&tp[0], BSSGP_IE_IMSI);
		osmo_mobile_identity_decode(&mi, mi_data, mi_len, false);
		nse = gbproxy_nse_by_imsi(nse->cfg, mi.imsi, CACHE_USAGE_PAGING);
		if (!nse) {
			return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
		}
		OSMO_ASSERT(nse->sgsn_facing);
		rc = gbprox_relay2nse(msg, nse, 0);
		break;
	}
	case BSSGP_PDUT_MS_REGISTR_ENQ:
	{
		struct gbproxy_sgsn *sgsn;
		struct osmo_mobile_identity mi;
		const uint8_t *mi_data = TLVP_VAL(&tp[0], BSSGP_IE_IMSI);
		uint8_t mi_len = TLVP_LEN(&tp[0], BSSGP_IE_IMSI);
		osmo_mobile_identity_decode(&mi, mi_data, mi_len, false);

		sgsn = gbproxy_select_sgsn(nse->cfg, NULL);
		if (!sgsn) {
			LOGP(DGPRS, LOGL_ERROR, "Could not find any SGSN, dropping message!\n");
			rc = -EINVAL;
			break;
		}

		gbproxy_imsi_cache_update(nse, mi.imsi, CACHE_USAGE_MS_REG_ENQ);

		rc = gbprox_relay2nse(msg, sgsn->nse, 0);
		break;
	}
	default:
		LOGPNSE(nse, LOGL_ERROR, "Rx %s: Implementation missing\n", pdut_name);
		break;
	}

	return rc;
err_no_bvc:
	LOGPNSE(nse, LOGL_ERROR, "Rx %s: cannot find BVC for BVCI=%05u\n", pdut_name, ptp_bvci);
	rate_ctr_inc(rate_ctr_group_get_ctr(nse->cfg->ctrg, GBPROX_GLOB_CTR_INV_NSEI));
	return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
}

/* Receive paging request from SGSN, we need to relay to proper BSS */
static int gbprox_rx_paging(struct gbproxy_nse *sgsn_nse, struct msgb *msg, const char *pdut_name,
			    struct tlv_parsed *tp, uint16_t ns_bvci, bool broadcast)
{
	struct gbproxy_config *cfg = sgsn_nse->cfg;
	struct gbproxy_bvc *sgsn_bvc, *bss_bvc;
	struct gbproxy_nse *nse;
	unsigned int n_nses = 0;
	int errctr = GBPROX_GLOB_CTR_PROTO_ERR_SGSN;
	int i, j;

	if (TLVP_PRES_LEN(tp, BSSGP_IE_BVCI, 2)) {
		uint16_t bvci = ntohs(tlvp_val16_unal(tp, BSSGP_IE_BVCI));
		errctr = GBPROX_GLOB_CTR_OTHER_ERR;
		sgsn_bvc = gbproxy_bvc_by_bvci(sgsn_nse, bvci);
		if (!sgsn_bvc) {
			LOGPNSE(sgsn_nse, LOGL_NOTICE, "Rx %s: unable to route: BVCI=%05u unknown\n",
				pdut_name, bvci);
			rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, errctr));
			return -EINVAL;
		}
		LOGPBVC(sgsn_bvc, LOGL_INFO, "Rx %s: routing by BVCI\n", pdut_name);
		return gbprox_relay2peer(msg, sgsn_bvc->cell->bss_bvc, ns_bvci);
	} else if (TLVP_PRES_LEN(tp, BSSGP_IE_ROUTEING_AREA, 6)) {
		struct gprs_ra_id raid;
		errctr = GBPROX_GLOB_CTR_INV_RAI;
		gsm48_parse_ra(&raid, TLVP_VAL(tp, BSSGP_IE_ROUTEING_AREA));
		/* iterate over all bvcs and dispatch the paging to each matching one */
		hash_for_each(cfg->bss_nses, i, nse, list) {
			hash_for_each(nse->bvcs, j, bss_bvc, list) {
				/* Skip BVCs without a cell (e.g. signalling) */
				if (!bss_bvc->cell)
					continue;

				if (gsm48_ra_equal(&bss_bvc->cell->id.raid, &raid)) {
					LOGPNSE(nse, LOGL_INFO, "Rx %s: routing to NSE (RAI match)\n",
						pdut_name);
					gbprox_relay2peer(msg, bss_bvc, ns_bvci);
					n_nses++;
					/* Only send it once to each NSE */
					break;
				}
			}
		}
	} else if (TLVP_PRES_LEN(tp, BSSGP_IE_LOCATION_AREA, 5)) {
		struct gsm48_ra_id lac;
		errctr = GBPROX_GLOB_CTR_INV_LAI;
		/* iterate over all bvcs and dispatch the paging to each matching one */
		hash_for_each(cfg->bss_nses, i, nse, list) {
			hash_for_each(nse->bvcs, j, bss_bvc, list) {
				/* Skip BVCs without a cell (e.g. signalling) */
				if (!bss_bvc->cell)
					continue;

				gsm48_encode_ra(&lac, &bss_bvc->cell->id.raid);
				if (!memcmp(&lac, TLVP_VAL(tp, BSSGP_IE_LOCATION_AREA), 5)) {
					LOGPNSE(nse, LOGL_INFO, "Rx %s: routing to NSE (LAI match)\n",
						pdut_name);
					gbprox_relay2peer(msg, bss_bvc, ns_bvci);
					n_nses++;
					/* Only send it once to each NSE */
					break;
				}
			}
		}
	} else if (TLVP_PRES_LEN(tp, BSSGP_IE_BSS_AREA_ID, 1) || broadcast) {
		/* iterate over all bvcs and dispatch the paging to each matching one */
		hash_for_each(cfg->bss_nses, i, nse, list) {
			hash_for_each(nse->bvcs, j, bss_bvc, list) {
				LOGPNSE(nse, LOGL_INFO, "Rx %s:routing to NSE (broadcast)\n", pdut_name);
				gbprox_relay2peer(msg, bss_bvc, ns_bvci);
				n_nses++;
				/* Only send it once to each NSE */
				break;
			}
		}
	} else {
		LOGPNSE(sgsn_nse, LOGL_ERROR, "BSSGP PAGING: unable to route, missing IE\n");
		rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, errctr));
	}

	if (n_nses == 0) {
		LOGPNSE(sgsn_nse, LOGL_ERROR, "BSSGP PAGING: unable to route, no destination found\n");
		rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, errctr));
		return -EINVAL;
	}
	return 0;
}

/* Receive an incoming BVC-RESET message from the SGSN */
static int rx_bvc_reset_from_sgsn(struct gbproxy_nse *nse, struct msgb *msg, struct tlv_parsed *tp,
			uint16_t ns_bvci)
{
	uint16_t ptp_bvci = ntohs(tlvp_val16_unal(tp, BSSGP_IE_BVCI));
	struct gbproxy_bvc *from_bvc;

	LOGPNSE(nse, LOGL_INFO, "Rx BVC-RESET (BVCI=%05u)\n", ptp_bvci);

	if (ptp_bvci == 0) {
		from_bvc = gbproxy_bvc_by_bvci(nse, 0);
		OSMO_ASSERT(from_bvc);
		osmo_fsm_inst_dispatch(from_bvc->fi, BSSGP_BVCFSM_E_RX_RESET, msg);
	} else {
		from_bvc = gbproxy_bvc_by_bvci(nse, ptp_bvci);
		if (!from_bvc) {
			LOGPNSE(nse, LOGL_ERROR, "Rx BVC-RESET BVCI=%05u: Cannot find BVC\n", ptp_bvci);
			rate_ctr_inc(rate_ctr_group_get_ctr(nse->cfg->ctrg, GBPROX_GLOB_CTR_INV_BVCI));
			return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKNOWN_BVCI, &ptp_bvci, msg);
		}
		osmo_fsm_inst_dispatch(from_bvc->fi, BSSGP_BVCFSM_E_RX_RESET, msg);
	}

	return 0;
}

/* Receive an incoming RIM message from the SGSN-side NS-VC */
static int gbprox_rx_rim_from_sgsn(struct tlv_parsed *tp, struct gbproxy_nse *nse, struct msgb *msg, char *log_pfx,
				   const char *pdut_name)
{
	struct gbproxy_sgsn *sgsn;
	struct gbproxy_cell *dest_cell;
	struct bssgp_rim_routing_info dest_ri;
	struct bssgp_rim_routing_info src_ri;
	int rc;
	char ri_src_str[64];
	char ri_dest_str[64];
	uint16_t ns_bvci = msgb_bvci(msg);

	/* TODO: Reply with STATUS if BSSGP didn't negotiate RIM feature, see also comments in
	   gbprox_rx_rim_from_bss() */

	rc = bssgp_parse_rim_ri(&dest_ri, TLVP_VAL(&tp[0], BSSGP_IE_RIM_ROUTING_INFO),
				TLVP_LEN(&tp[0], BSSGP_IE_RIM_ROUTING_INFO));
	if (rc < 0) {
		LOGP(DGPRS, LOGL_ERROR, "%s %s cannot parse destination RIM routing info\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
	}
	rc = bssgp_parse_rim_ri(&src_ri, TLVP_VAL(&tp[1], BSSGP_IE_RIM_ROUTING_INFO),
				TLVP_LEN(&tp[1], BSSGP_IE_RIM_ROUTING_INFO));
	if (rc < 0) {
		LOGP(DGPRS, LOGL_ERROR, "%s %s cannot parse source RIM routing info\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
	}

	/* Since gbproxy is 2G only we do not expect to get RIM messages that target non-GERAN cells. */
	if (dest_ri.discr != BSSGP_RIM_ROUTING_INFO_GERAN) {
		LOGP(DGPRS, LOGL_ERROR, "%s %s destination RIM routing info is not GERAN (%s)\n", log_pfx, pdut_name,
		     bssgp_rim_ri_name(&dest_ri));
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
	}

	/* Lookup destination cell */
	dest_cell = gbproxy_cell_by_cellid(nse->cfg, &dest_ri.geran.raid, dest_ri.geran.cid);
	if (!dest_cell) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s cannot find cell for destination RIM routing info (%s)\n", log_pfx,
		     pdut_name, bssgp_rim_ri_name(&dest_ri));
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
	}

	/* TODO: Check if the BVC of the destination cell actually did negotiate RIM support, see also comments
	 * in gbprox_rx_rim_from_bss() */
	sgsn = gbproxy_sgsn_by_nsei(nse->cfg, nse->nsei);
	OSMO_ASSERT(sgsn);

	LOGP(DLBSSGP, LOGL_DEBUG, "%s %s relaying from SGSN(%05u/%s) RIM-PDU: src=%s, dest=%s\n",
	     log_pfx, pdut_name, sgsn->nse->nsei, sgsn->name,
	     bssgp_rim_ri_name_buf(ri_src_str, sizeof(ri_src_str), &src_ri),
	     bssgp_rim_ri_name_buf(ri_dest_str, sizeof(ri_dest_str), &dest_ri));

	return gbprox_relay2peer(msg, dest_cell->bss_bvc, 0);
}

/* Receive an incoming signalling message from the SGSN-side NS-VC */
static int gbprox_rx_sig_from_sgsn(struct gbproxy_nse *nse, struct msgb *msg, uint16_t ns_bvci)
{
	struct bssgp_normal_hdr *bgph = (struct bssgp_normal_hdr *) msgb_bssgph(msg);
	uint8_t pdu_type = bgph->pdu_type;
	const char *pdut_name = osmo_tlv_prot_msg_name(&osmo_pdef_bssgp, bgph->pdu_type);
	struct gbproxy_config *cfg = nse->cfg;
	struct gbproxy_bvc *sgsn_bvc;
	struct tlv_parsed tp[2];
	int data_len;
	uint16_t bvci;
	char log_pfx[32];
	int rc = 0;
	int i;
	bool paging_bc = false;

	snprintf(log_pfx, sizeof(log_pfx), "NSE(%05u/SGSN)-BVC(%05u/??)", nse->nsei, ns_bvci);

	LOGP(DGPRS, LOGL_DEBUG, "%s Rx %s\n", log_pfx, pdut_name);

	if (ns_bvci != 0 && ns_bvci != 1) {
		LOGP(DGPRS, LOGL_NOTICE, "%s BVCI=%05u is not signalling\n", log_pfx, ns_bvci);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(pdu_type) & BSSGP_PDUF_SIG)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in signalling BVC\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	if (!(bssgp_pdu_type_flags(pdu_type) & BSSGP_PDUF_DL)) {
		LOGP(DGPRS, LOGL_NOTICE, "%s %s not allowed in downlink direction\n", log_pfx, pdut_name);
		return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
	}

	data_len = msgb_bssgp_len(msg) - sizeof(*bgph);

	rc = osmo_tlv_prot_parse(&osmo_pdef_bssgp, tp, ARRAY_SIZE(tp), pdu_type, bgph->data, data_len, 0, 0,
				 DGPRS, log_pfx);
	if (rc < 0) {
		rc = tx_status_from_tlvp(nse, rc, msg);
		rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, GBPROX_GLOB_CTR_PROTO_ERR_SGSN));
		return rc;
	}
	/* hack to get both msg + tlv_parsed passed via osmo_fsm_inst_dispatch */
	msgb_bcid(msg) = (void *)tp;

	switch (pdu_type) {
	case BSSGP_PDUT_BVC_RESET:
		/* resolve or create ggbproxy_bvc + handle in BVC-FSM */
		bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		rc = rx_bvc_reset_from_sgsn(nse, msg, &tp[0], ns_bvci);
		break;
	case BSSGP_PDUT_BVC_RESET_ACK:
		bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		sgsn_bvc = gbproxy_bvc_by_bvci(nse, bvci);
		if (!sgsn_bvc)
			goto err_no_bvc;
		rc = osmo_fsm_inst_dispatch(sgsn_bvc->fi, BSSGP_BVCFSM_E_RX_RESET_ACK, msg);
		break;
	case BSSGP_PDUT_BVC_BLOCK_ACK:
		bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		sgsn_bvc = gbproxy_bvc_by_bvci(nse, bvci);
		if (!sgsn_bvc) {
			/* Check if BVC was blocked before */
			sgsn_bvc = gbproxy_bvc_by_bvci_inactive(nse, bvci);
			if (!sgsn_bvc)
				goto err_no_bvc;
		}
		rc = osmo_fsm_inst_dispatch(sgsn_bvc->fi, BSSGP_BVCFSM_E_RX_BLOCK_ACK, msg);
		break;
	case BSSGP_PDUT_BVC_UNBLOCK_ACK:
		bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		sgsn_bvc = gbproxy_bvc_by_bvci(nse, bvci);
		if (!sgsn_bvc)
			goto err_no_bvc;
		rc = osmo_fsm_inst_dispatch(sgsn_bvc->fi, BSSGP_BVCFSM_E_RX_UNBLOCK_ACK, msg);
		break;
	case BSSGP_PDUT_FLUSH_LL:
		/* TODO: If new BVCI is on different NSE we should remove the new BVCI so the
		 * message is interpreted as a request to delete the PDUs, not forward them.
		 * If we negotiate Inter-NSE re-routing or LCS-procedures we can also
		 * add the NSEI TLV to trigger re-routing the PDUs */
		/* simple case: BVCI IE is mandatory */
		bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
		sgsn_bvc = gbproxy_bvc_by_bvci(nse, bvci);
		if (!sgsn_bvc)
			goto err_no_bvc;
		if (sgsn_bvc->cell && sgsn_bvc->cell->bss_bvc)
			rc = gbprox_relay2peer(msg, sgsn_bvc->cell->bss_bvc, ns_bvci);
		break;
	case BSSGP_PDUT_DUMMY_PAGING_PS:
		/* Routing area is optional in dummy paging and we have nothing else to go by
		 * so in case it is missing we need to broadcast the paging */
		paging_bc = true;
		/* fall through */
	case BSSGP_PDUT_PAGING_PS:
	{
		/* Cache the IMSI<->NSE to route PAGING REJECT */
		struct osmo_mobile_identity mi;
		const uint8_t *mi_data = TLVP_VAL(&tp[0], BSSGP_IE_IMSI);
		uint8_t mi_len = TLVP_LEN(&tp[0], BSSGP_IE_IMSI);
		osmo_mobile_identity_decode(&mi, mi_data, mi_len, false);
		gbproxy_imsi_cache_update(nse, mi.imsi, CACHE_USAGE_PAGING);
		/* fall through */
	}
	case BSSGP_PDUT_PAGING_CS:
		/* process the paging request (LAI/RAI lookup) */
		rc = gbprox_rx_paging(nse, msg, pdut_name, &tp[0], ns_bvci, paging_bc);
		break;
	case BSSGP_PDUT_STATUS:
	{
		struct gbproxy_nse *nse_peer;
		uint32_t tlli;

		/* Check if the status needs to be terminated locally */
		uint8_t cause = *TLVP_VAL(&tp[0], BSSGP_IE_CAUSE);

		if (cause == BSSGP_CAUSE_UNKNOWN_BVCI || cause == BSSGP_CAUSE_BVCI_BLOCKED) {
			/* Log and handle locally, BVCI should be present for these causes */
			if (!TLVP_PRESENT(&tp[0], BSSGP_IE_BVCI)) {
				LOGPNSE(nse, LOGL_ERROR, "Rx STATUS cause=0x%02x(%s), but BVCI is missing\n", cause,
					bssgp_cause_str(cause));
				break;
			}
			uint16_t ptp_bvci = ntohs(tlvp_val16_unal(&tp[0], BSSGP_IE_BVCI));
			LOGPNSE(nse, LOGL_ERROR, "Rx STATUS cause=0x%02x(%s) for PtP-BVC %05u\n", cause,
				bssgp_cause_str(cause), ptp_bvci);
			/* FIXME: Remove/block the other BSS/SGSN BVCs if present? */
			break;
		}

		LOGPNSE(nse, LOGL_NOTICE, "Rx STATUS cause=0x%02x(%s)\n", cause,
			bssgp_cause_str(cause));


		if (gbproxy_bvci_from_status_pdu(tp, &bvci, log_pfx) == 0 && bvci != 0) {
			struct gbproxy_cell *cell = gbproxy_cell_by_bvci(cfg, bvci);

			if ((!cell || !cell->bss_bvc || !cell->bss_bvc->nse)) {
				LOGPNSE(nse, LOGL_ERROR, "Rx STATUS cause=0x%02x(%s), but can't find NSE for cell\n",
					cause, bssgp_cause_str(cause));
				break;
			}

			return gbprox_relay2nse(msg, cell->bss_bvc->nse, 0);
		}

		/* We can only forward this TLLI if it's in the cache (which only happens on suspend/resume) */
		if (gbproxy_tlli_from_status_pdu(tp, &tlli, log_pfx) == 0) {
			nse_peer = gbproxy_nse_by_tlli(cfg, tlli);
			if (nse_peer)
				return gbprox_relay2nse(msg, nse_peer, 0);
		}

		LOGPNSE(nse, LOGL_ERROR, "Unable to handle STATUS cause=0x%02x(%s)\n", cause,
			bssgp_cause_str(cause));

		break;
	}
	/* those only exist in the SGSN -> BSS direction */
	case BSSGP_PDUT_SUSPEND_ACK:
	case BSSGP_PDUT_SUSPEND_NACK:
	case BSSGP_PDUT_RESUME_ACK:
	case BSSGP_PDUT_RESUME_NACK:
	{
		struct gbproxy_nse *nse_peer;
		uint32_t tlli = osmo_load32be(TLVP_VAL(&tp[0], BSSGP_IE_TLLI));

		nse_peer = gbproxy_nse_by_tlli(cfg, tlli);
		if (!nse_peer) {
			LOGPNSE(nse, LOGL_ERROR, "Rx %s: Cannot find NSE\n", pdut_name);
			/* TODO: Counter */
			return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
		}
		/* Delete the entry after we're done */
		gbproxy_tlli_cache_remove(cfg, tlli);
		LOGPNSE(nse_peer, LOGL_DEBUG, "Rx %s: forwarding\n", pdut_name);
		gbprox_relay2nse(msg, nse_peer, ns_bvci);
		break;
	}
	case BSSGP_PDUT_SGSN_INVOKE_TRACE:
	case BSSGP_PDUT_OVERLOAD:
		LOGPNSE(nse, LOGL_DEBUG, "Rx %s: broadcasting\n", pdut_name);
		/* broadcast to all BSS-side bvcs */
		hash_for_each(cfg->bss_nses, i, nse, list) {
			gbprox_relay2nse(msg, nse, 0);
		}
		break;
	case BSSGP_PDUT_RAN_INFO:
	case BSSGP_PDUT_RAN_INFO_REQ:
	case BSSGP_PDUT_RAN_INFO_ACK:
	case BSSGP_PDUT_RAN_INFO_ERROR:
	case BSSGP_PDUT_RAN_INFO_APP_ERROR:
		rc = gbprox_rx_rim_from_sgsn(tp, nse, msg, log_pfx, pdut_name);
		break;
	case BSSGP_PDUT_MS_REGISTR_ENQ_RESP:
	{
		struct gbproxy_nse *nse_peer;
		struct osmo_mobile_identity mi;
		const uint8_t *mi_data = TLVP_VAL(&tp[0], BSSGP_IE_IMSI);
		uint8_t mi_len = TLVP_LEN(&tp[0], BSSGP_IE_IMSI);
		osmo_mobile_identity_decode(&mi, mi_data, mi_len, false);
		nse_peer = gbproxy_nse_by_imsi(cfg, mi.imsi, CACHE_USAGE_MS_REG_ENQ);
		if (!nse_peer) {
			LOGPNSE(nse, LOGL_ERROR, "Rx %s: Cannot find NSE\n", pdut_name);
			return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
		} else if (nse_peer->sgsn_facing) {
			LOGPNSE(nse, LOGL_ERROR, "Forwarding %s failed: IMSI cache contains SGSN NSE", pdut_name);
			return tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
		}
		gbproxy_imsi_cache_remove(cfg, mi.imsi, CACHE_USAGE_MS_REG_ENQ);
		gbprox_relay2nse(msg, nse_peer, ns_bvci);
		break;
	}
	default:
		LOGPNSE(nse, LOGL_NOTICE, "Rx %s: Not supported\n", pdut_name);
		rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, GBPROX_GLOB_CTR_PROTO_ERR_SGSN));
		rc = tx_status(nse, ns_bvci, BSSGP_CAUSE_PROTO_ERR_UNSPEC, NULL, msg);
		break;
	}

	return rc;

err_no_bvc:
	LOGPNSE(nse, LOGL_ERROR, "Rx %s: Cannot find BVC %05u\n", pdut_name, bvci);
	rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, GBPROX_GLOB_CTR_INV_BVCI));
	return tx_status(nse, ns_bvci, BSSGP_CAUSE_INV_MAND_INF, NULL, msg);
}


/***********************************************************************
 * libosmogb NS/BSSGP integration
 ***********************************************************************/

int gbprox_bssgp_send_cb(void *ctx, struct msgb *msg)
{
	int rc;
	struct gbproxy_config *cfg = (struct gbproxy_config *) ctx;
	struct gprs_ns2_inst *nsi = cfg->nsi;
	struct osmo_gprs_ns2_prim nsp = {};

	nsp.bvci = msgb_bvci(msg);
	nsp.nsei = msgb_nsei(msg);

	osmo_prim_init(&nsp.oph, SAP_NS, GPRS_NS2_PRIM_UNIT_DATA, PRIM_OP_REQUEST, msg);
	rc = gprs_ns2_recv_prim(nsi, &nsp.oph);

	return rc;
}

/* Main input function for Gb proxy */
int gbprox_rcvmsg(void *ctx, struct msgb *msg)
{
	struct gbproxy_config *cfg = (struct gbproxy_config *) ctx;
	uint16_t ns_bvci = msgb_bvci(msg);
	uint16_t nsei = msgb_nsei(msg);
	struct gbproxy_nse *nse;

	nse = gbproxy_nse_by_nsei(cfg, nsei, NSE_F_SGSN);
	if (nse) {
		/* ensure minimum length to decode PDU type */
		if (msgb_bssgp_len(msg) < sizeof(struct bssgp_normal_hdr))
			return tx_status(nse, ns_bvci, BSSGP_CAUSE_SEM_INCORR_PDU, NULL, msg);

		if (ns_bvci == 0 || ns_bvci == 1)
			return gbprox_rx_sig_from_sgsn(nse, msg, ns_bvci);
		else
			return gbprox_rx_ptp_from_sgsn(nse, msg, ns_bvci);
	}

	nse = gbproxy_nse_by_nsei(cfg, nsei, NSE_F_BSS);
	if (!nse) {
		LOGP(DGPRS, LOGL_NOTICE, "NSE(%05u/BSS) not known -> allocating\n", nsei);
		nse = gbproxy_nse_alloc(cfg, nsei, false);
	}
	if (nse) {
		/* ensure minimum length to decode PDU type */
		if (msgb_bssgp_len(msg) < sizeof(struct bssgp_normal_hdr))
			return tx_status(nse, ns_bvci, BSSGP_CAUSE_SEM_INCORR_PDU, NULL, msg);

		if (ns_bvci == 0 || ns_bvci == 1)
			return gbprox_rx_sig_from_bss(nse, msg, ns_bvci);
		else
			return gbprox_rx_ptp_from_bss(nse, msg, ns_bvci);
	}

	return 0;
}

/*  TODO: What about handling:
 * 	GPRS_NS2_AFF_CAUSE_VC_FAILURE,
	GPRS_NS2_AFF_CAUSE_VC_RECOVERY,
	osmocom own causes
	GPRS_NS2_AFF_CAUSE_SNS_CONFIGURED,
	GPRS_NS2_AFF_CAUSE_SNS_FAILURE,
	*/

void gprs_ns_prim_status_cb(struct gbproxy_config *cfg, struct osmo_gprs_ns2_prim *nsp)
{
	int i;
	struct gbproxy_bvc *bvc;
	struct gbproxy_nse *nse;

	switch (nsp->u.status.cause) {
	case GPRS_NS2_AFF_CAUSE_SNS_FAILURE:
	case GPRS_NS2_AFF_CAUSE_SNS_CONFIGURED:
		break;

	case GPRS_NS2_AFF_CAUSE_RECOVERY:
		LOGP(DGPRS, LOGL_NOTICE, "NS-NSE %d became available\n", nsp->nsei);
		nse = gbproxy_nse_by_nsei(cfg, nsp->nsei, NSE_F_SGSN);
		if (nse) {
			nse->alive = true;
			// Update the NSE max SDU len
			nse->max_sdu_len = nsp->u.status.mtu;

			uint8_t cause = BSSGP_CAUSE_OML_INTERV;
			bvc = gbproxy_bvc_by_bvci(nse, 0);
			if (bvc) {
				bssgp_bvc_fsm_set_max_pdu_len(bvc->fi, nse->max_sdu_len);
				osmo_fsm_inst_dispatch(bvc->fi, BSSGP_BVCFSM_E_REQ_RESET, &cause);
			}
		}
		break;
	case GPRS_NS2_AFF_CAUSE_FAILURE:
		nse = gbproxy_nse_by_nsei(cfg, nsp->nsei, NSE_F_BSS | NSE_F_SGSN);
		if (!nse) {
			LOGP(DGPRS, LOGL_ERROR, "Unknown NSE(%05d) became unavailable\n", nsp->nsei);
			break;
		}

		nse->alive = false;
		if (nse->sgsn_facing) {
			struct hlist_node *ntmp;
			/* SGSN */
			/* TODO: When to block all PtP towards bss? Only if all SGSN are down? */
			hash_for_each_safe(nse->bvcs, i, ntmp, bvc, list) {
				if (bvc->bvci == 0)
					continue;
				gbproxy_bvc_free(bvc);
			}
			rate_ctr_inc(rate_ctr_group_get_ctr(cfg->ctrg, GBPROX_GLOB_CTR_RESTART_RESET_SGSN));
		} else {
			/* BSS became unavailable
			 * Block matching PtP-BVCs on SGSN-side */
			hash_for_each(nse->bvcs, i, bvc, list) {
				if (bvc->bvci == 0)
					continue;
				/* Get BVC for each SGSN and send block request */
				struct gbproxy_cell *cell = bvc->cell;
				for (int j = 0; j < GBPROXY_MAX_NR_SGSN; j++) {
					struct gbproxy_bvc *sgsn_bvc = cell->sgsn_bvc[j];
					if (!sgsn_bvc)
						continue;

					/* Block BVC, indicate BSS equipment failure */
					uint8_t cause = BSSGP_CAUSE_EQUIP_FAIL;
					osmo_fsm_inst_dispatch(sgsn_bvc->fi, BSSGP_BVCFSM_E_REQ_BLOCK, &cause);
					sgsn_bvc->inactive = true;
				}
			}

			/* This frees the BVCs for us as well */
			gbproxy_nse_free(nse);
		}
		LOGP(DGPRS, LOGL_NOTICE, "NS-NSE %d became unavailable\n", nsp->nsei);
		break;
	default:
		LOGP(DGPRS, LOGL_NOTICE, "NS: Unknown NS-STATUS.ind cause=%s from NS\n",
		     gprs_ns2_aff_cause_prim_str(nsp->u.status.cause));
		break;
	}
}

/* called by the ns layer */
int gprs_ns2_prim_cb(struct osmo_prim_hdr *oph, void *ctx)
{
	struct osmo_gprs_ns2_prim *nsp;
	struct gbproxy_config *cfg = (struct gbproxy_config *) ctx;
	uintptr_t bvci;
	int rc = 0;

	if (oph->sap != SAP_NS)
		return 0;

	nsp = container_of(oph, struct osmo_gprs_ns2_prim, oph);

	if (oph->operation != PRIM_OP_INDICATION) {
		LOGP(DGPRS, LOGL_NOTICE, "NS: Unexpected primitive operation %s from NS\n",
		     get_value_string(osmo_prim_op_names, oph->operation));
		return 0;
	}

	switch (oph->primitive) {
	case GPRS_NS2_PRIM_UNIT_DATA:

		/* hand the message into the BSSGP implementation */
		msgb_bssgph(oph->msg) = oph->msg->l3h;
		msgb_bvci(oph->msg) = nsp->bvci;
		msgb_nsei(oph->msg) = nsp->nsei;
		bvci = nsp->bvci | BVC_LOG_CTX_FLAG;

		log_set_context(LOG_CTX_GB_BVC, (void *)bvci);
		rc = gbprox_rcvmsg(cfg, oph->msg);
		msgb_free(oph->msg);
		break;
	case GPRS_NS2_PRIM_STATUS:
		gprs_ns_prim_status_cb(cfg, nsp);
		break;
	default:
		LOGP(DGPRS, LOGL_NOTICE, "NS: Unknown prim %s %s from NS\n",
		     gprs_ns2_prim_str(oph->primitive),
		     get_value_string(osmo_prim_op_names, oph->operation));
		break;
	}

	return rc;
}

void gbprox_reset(struct gbproxy_config *cfg)
{
	struct gbproxy_nse *nse;
	struct hlist_node *ntmp;
	int i, j;

	hash_for_each_safe(cfg->bss_nses, i, ntmp, nse, list) {
		struct gbproxy_bvc *bvc;
		struct hlist_node *tmp;
		hash_for_each_safe(nse->bvcs, j, tmp, bvc, list)
			gbproxy_bvc_free(bvc);

		gbproxy_nse_free(nse);
	}
	/* FIXME: cells */
	/* FIXME: SGSN side BVCs (except signaling) */

	rate_ctr_group_free(cfg->ctrg);
	gbproxy_init_config(cfg);
}

static void tlli_cache_cleanup(void *data)
{
	struct gbproxy_config *cfg = data;
	gbproxy_tlli_cache_cleanup(cfg);

	/* TODO: Disable timer when cache is empty */
	osmo_timer_schedule(&cfg->tlli_cache.timer, 2, 0);
}

static void imsi_cache_cleanup(void *data)
{
	struct gbproxy_config *cfg = data;
	gbproxy_imsi_cache_cleanup(cfg);

	/* TODO: Disable timer when cache is empty */
	osmo_timer_schedule(&cfg->imsi_cache.timer, 2, 0);
}

int gbproxy_init_config(struct gbproxy_config *cfg)
{
	struct timespec tp;

	/* by default we advertise 100% of the BSS-side capacity to _each_ SGSN */
	cfg->pool.bvc_fc_ratio = 100;
	cfg->pool.null_nri_ranges = osmo_nri_ranges_alloc(cfg);
	/* TODO: Make configurable */
	cfg->tlli_cache.timeout = 10;
	cfg->imsi_cache.timeout = 10;

	hash_init(cfg->bss_nses);
	hash_init(cfg->sgsn_nses);
	hash_init(cfg->cells);
	hash_init(cfg->tlli_cache.entries);
	INIT_LLIST_HEAD(&cfg->sgsns);

	osmo_timer_setup(&cfg->tlli_cache.timer, tlli_cache_cleanup, cfg);
	osmo_timer_schedule(&cfg->tlli_cache.timer, 2, 0);

	/* We could also combine both timers */
	osmo_timer_setup(&cfg->imsi_cache.timer, imsi_cache_cleanup, cfg);
	osmo_timer_schedule(&cfg->imsi_cache.timer, 2, 0);

	cfg->ctrg = rate_ctr_group_alloc(tall_sgsn_ctx, &global_ctrg_desc, 0);
	if (!cfg->ctrg) {
		LOGP(DGPRS, LOGL_ERROR, "Cannot allocate global counter group!\n");
		return -1;
	}
	osmo_clock_gettime(CLOCK_REALTIME, &tp);
	osmo_fsm_log_timeouts(true);

	return 0;
}