diff --git a/openbsc/include/openbsc/gprs_bssgp.h b/openbsc/include/openbsc/gprs_bssgp.h
new file mode 100644
index 0000000..d3ccb12
--- /dev/null
+++ b/openbsc/include/openbsc/gprs_bssgp.h
@@ -0,0 +1,163 @@
+#ifndef _GPRS_BSSGP_H
+#define _GPRS_BSSGP_H
+
+#include <stdint.h>
+
+/* Section 11.3.26 / Table 11.27 */
+enum bssgp_pdu_type {
+	/* PDUs between RL and BSSGP SAPs */
+	BSSGP_PDUT_DL_UNITDATA		= 0x00,
+	BSSGP_PDUT_UL_UNITDATA		= 0x01,
+	BSSGP_PDUT_RA_CAPABILITY	= 0x02,
+	BSSGP_PDUT_PTM_UNITDATA		= 0x03,
+	/* PDUs between GMM SAPs */
+	BSSGP_PDUT_PAGING_PS		= 0x06,
+	BSSGP_PDUT_PAGING_CS		= 0x07,
+	BSSGP_PDUT_RA_CAPA_UDPATE	= 0x08,
+	BSSGP_PDUT_RA_CAPA_UPDATE_ACK	= 0x09,
+	BSSGP_PDUT_RADIO_STATUS		= 0x0a,
+	BSSGP_PDUT_SUSPEND		= 0x0b,
+	BSSGP_PDUT_SUSPEND_ACK		= 0x0c,
+	BSSGP_PDUT_SUSPEND_NACK		= 0x0d,
+	BSSGP_PDUT_RESUME		= 0x0e,
+	BSSGP_PDUT_RESUME_ACK		= 0x0f,
+	BSSGP_PDUT_RESUME_NACK		= 0x10,
+	/* PDus between NM SAPs */
+	BSSGP_PDUT_BVC_BLOCK		= 0x20,
+	BSSGP_PDUT_BVC_BLOCK_ACK	= 0x21,
+	BSSGP_PDUT_BVC_RESET		= 0x22,
+	BSSGP_PDUT_BVC_RESET_ACK	= 0x23,
+	BSSGP_PDUT_BVC_UNBLOCK		= 0x24,
+	BSSGP_PDUT_BVC_UNBLOCK_ACK	= 0x25,
+	BSSGP_PDUT_FLOW_CONTROL_BVC	= 0x26,
+	BSSGP_PDUT_FLOW_CONTROL_BVC_ACK	= 0x27,
+	BSSGP_PDUT_FLOW_CONTROL_MS	= 0x28,
+	BSSGP_PDUT_FLOW_CONTROL_MS_ACK	= 0x29,
+	BSSGP_PDUT_FLUSH_LL		= 0x2a,
+	BSSGP_PDUT_FLUSH_LL_ACK		= 0x2b,
+	BSSGP_PDUT_LLC_DISCARD		= 0x2c,
+	BSSGP_PDUT_SGSN_INVOKE_TRACE	= 0x40,
+	BSSGP_PDUT_STATUS		= 0x41,
+	/* PDUs between PFM SAP's */
+	BSSGP_PDUT_DOWNLOAD_BSS_PFC	= 0x50,
+	BSSGP_PDUT_CREATE_BSS_PFC	= 0x51,
+	BSSGP_PDUT_CREATE_BSS_PFC_ACK	= 0x52,
+	BSSGP_PDUT_CREATE_BSS_PFC_NACK	= 0x53,
+	BSSGP_PDUT_MODIFY_BSS_PFC	= 0x54,
+	BSSGP_PDUT_MODIFY_BSS_PFC_ACK	= 0x55,
+	BSSGP_PDUT_DELETE_BSS_PFC	= 0x56,
+	BSSGP_PDUT_DELETE_BSS_PFC_ACK	= 0x57,
+};
+
+/* Section 10.2.1 and 10.2.2 */
+struct bssgp_ud_hdr {
+	uint8_t pdu_type;
+	uint32_t tlli;
+	uint8_t qos_profile[3];
+	uint8_t data[0];	/* TLV's */
+} __attribute__((packed));
+
+struct bssgp_normal_hdr {
+	uint8_t pdu_type;
+	uint8_t data[0];	/* TLV's */
+};
+
+enum bssgp_iei_type {
+	BSSGP_IE_ALIGNMENT		= 0x00,
+	BSSGP_IE_BMAX_DEFAULT_MS	= 0x01,
+	BSSGP_IE_BSS_AREA_ID		= 0x02,
+	BSSGP_IE_BUCKET_LEAK_RATE	= 0x03,
+	BSSGP_IE_BVCI			= 0x04,
+	BSSGP_IE_BVC_BUCKET_SIZE	= 0x05,
+	BSSGP_IE_BVC_MEASUREMENT	= 0x06,
+	BSSGP_IE_CAUSE			= 0x07,
+	BSSGP_IE_CELL_ID		= 0x08,
+	BSSGP_IE_CHAN_NEEDED		= 0x09,
+	BSSGP_IE_DRX_PARAMS		= 0x0a,
+	BSSGP_IE_EMLPP_PRIO		= 0x0b,
+	BSSGP_IE_FLUSH_ACTION		= 0x0c,
+	BSSGP_IE_IMSI			= 0x0d,
+	BSSGP_IE_LLC_PDU		= 0x0e,
+	BSSGP_IE_LLC_FRAMES_DISCARDED	= 0x0f,
+	BSSGP_IE_LOCATION_AREA		= 0x10,
+	BSSGP_IE_MOBILE_ID		= 0x11,
+	BSSGP_IE_MS_BUCKET_SIZE		= 0x12,
+	BSSGP_IE_MS_RADIO_ACCESS_CAP	= 0x13,
+	BSSGP_IE_OMC_ID			= 0x14,
+	BSSGP_IE_PDU_IN_ERROR		= 0x15,
+	BSSGP_IE_PDU_LIFETIME		= 0x16,
+	BSSGP_IE_PRIORITY		= 0x17,
+	BSSGP_IE_QOS_PROFILE		= 0x18,
+	BSSGP_IE_RADIO_CAUSE		= 0x19,
+	BSSGP_IE_RA_CAP_UPD_CAUSE	= 0x1a,
+	BSSGP_IE_ROUTEING_AREA		= 0x1b,
+	BSSGP_IE_R_DEFAULT_MS		= 0x1c,
+	BSSGP_IE_SUSPEND_REF_NR		= 0x1d,
+	BSSGP_IE_TAG			= 0x1e,
+	BSSGP_IE_TLLI			= 0x1f,
+	BSSGP_IE_TMSI			= 0x20,
+	BSSGP_IE_TRACE_REFERENC		= 0x21,
+	BSSGP_IE_TRACE_TYPE		= 0x22,
+	BSSGP_IE_TRANSACTION_ID		= 0x23,
+	BSSGP_IE_TRIGGER_ID		= 0x24,
+	BSSGP_IE_NUM_OCT_AFF		= 0x25,
+	BSSGP_IE_LSA_ID_LIST		= 0x26,
+	BSSGP_IE_LSA_INFORMATION	= 0x27,
+	BSSGP_IE_PACKET_FLOW_ID		= 0x28,
+	BSSGP_IE_PACKET_FLOW_TIMER	= 0x29,
+	BSSGP_IE_AGG_BSS_QOS_PROFILE	= 0x3a,
+	BSSGP_IE_FEATURE_BITMAP		= 0x3b,
+	BSSGP_IE_BUCKET_FULL_RATIO	= 0x3c,
+	BSSGP_IE_SERVICE_UTRAN_CCO	= 0x3d,
+};
+
+/* Section 11.3.8 / Table 11.10: Cause coding */
+enum gprs_bssgp_cause {
+	BSSGP_CAUSE_PROC_OVERLOAD	= 0x00,
+	BSSGP_CAUSE_EQUIP_FAIL		= 0x01,
+	BSSGP_CAUSE_TRASIT_NET_FAIL	= 0x02,
+	BSSGP_CAUSE_CAPA_GREATER_0KPBS	= 0x03,
+	BSSGP_CAUSE_UNKNOWN_MS		= 0x04,
+	BSSGP_CAUSE_UNKNOWN_BVCI	= 0x05,
+	BSSGP_CAUSE_CELL_TRAF_CONG	= 0x06,
+	BSSGP_CAUSE_SGSN_CONG		= 0x07,
+	BSSGP_CAUSE_OML_INTERV		= 0x08,
+	BSSGP_CAUSE_BVCI_BLOCKED	= 0x09,
+	BSSGP_CAUSE_PFC_CREATE_FAIL	= 0x0a,
+	BSSGP_CAUSE_SEM_INCORR_PDU	= 0x20,
+	BSSGP_CAUSE_INV_MAND_INF	= 0x21,
+	BSSGP_CAUSE_MISSING_MAND_IE	= 0x22,
+	BSSGP_CAUSE_MISSING_COND_IE	= 0x23,
+	BSSGP_CAUSE_UNEXP_COND_IE	= 0x24,
+	BSSGP_CAUSE_COND_IE_ERR		= 0x25,
+	BSSGP_CAUSE_PDU_INCOMP_STATE	= 0x26,
+	BSSGP_CAUSE_PROTO_ERR_UNSPEC	= 0x27,
+	BSSGP_CAUSE_PDU_INCOMP_FEAT	= 0x28,
+};
+
+/* Our implementation */
+
+/* gprs_bssgp_util.c */
+extern struct gprs_ns_inst *bssgp_nsi;
+struct msgb *bssgp_msgb_alloc(void);
+const char *bssgp_cause_str(enum gprs_bssgp_cause cause);
+/* Transmit a simple response such as BLOCK/UNBLOCK/RESET ACK/NACK */
+int bssgp_tx_simple_bvci(uint8_t pdu_type, uint16_t nsei,
+			 uint16_t bvci, uint16_t ns_bvci);
+/* Chapter 10.4.14: Status */
+int bssgp_tx_status(uint8_t cause, uint16_t *bvci, struct msgb *orig_msg);
+
+/* gprs_bssgp.c */
+
+#include <osmocore/tlv.h>
+
+extern int gprs_bssgp_rcvmsg(struct msgb *msg);
+uint16_t bssgp_parse_cell_id(struct gprs_ra_id *raid, const uint8_t *buf);
+
+/* Wrapper around TLV parser to parse BSSGP IEs */
+static inline int bssgp_tlv_parse(struct tlv_parsed *tp, uint8_t *buf, int len)
+{
+	return tlv_parse(tp, &tvlv_att_def, buf, len, 0, 0);
+}
+
+#endif /* _GPRS_BSSGP_H */
diff --git a/openbsc/include/openbsc/gprs_ns.h b/openbsc/include/openbsc/gprs_ns.h
new file mode 100644
index 0000000..c74546a
--- /dev/null
+++ b/openbsc/include/openbsc/gprs_ns.h
@@ -0,0 +1,181 @@
+#ifndef _GPRS_NS_H
+#define _GPRS_NS_H
+
+#include <stdint.h>
+
+/* GPRS Networks Service (NS) messages on the Gb interface
+ * 3GPP TS 08.16 version 8.0.1 Release 1999 / ETSI TS 101 299 V8.0.1 (2002-05)
+ * 3GPP TS 48.016 version 6.5.0 Release 6 / ETSI TS 148 016 V6.5.0 (2005-11) */
+
+struct gprs_ns_hdr {
+	uint8_t pdu_type;
+	uint8_t data[0];
+} __attribute__((packed));
+
+/* TS 08.16, Section 10.3.7, Table 14 */
+enum ns_pdu_type {
+	NS_PDUT_UNITDATA	= 0x00,
+	NS_PDUT_RESET		= 0x02,
+	NS_PDUT_RESET_ACK	= 0x03,
+	NS_PDUT_BLOCK		= 0x04,
+	NS_PDUT_BLOCK_ACK	= 0x05,
+	NS_PDUT_UNBLOCK		= 0x06,
+	NS_PDUT_UNBLOCK_ACK	= 0x07,
+	NS_PDUT_STATUS		= 0x08,
+	NS_PDUT_ALIVE		= 0x0a,
+	NS_PDUT_ALIVE_ACK	= 0x0b,
+	/* TS 48.016 Section 10.3.7, Table 10.3.7.1 */
+	SNS_PDUT_ACK		= 0x0c,
+	SNS_PDUT_ADD		= 0x0d,
+	SNS_PDUT_CHANGE_WEIGHT	= 0x0e,
+	SNS_PDUT_CONFIG		= 0x0f,
+	SNS_PDUT_CONFIG_ACK	= 0x10,
+	SNS_PDUT_DELETE		= 0x11,
+	SNS_PDUT_SIZE		= 0x12,
+	SNS_PDUT_SIZE_ACK	= 0x13,
+};
+
+/* TS 08.16, Section 10.3, Table 12 */
+enum ns_ctrl_ie {
+	NS_IE_CAUSE		= 0x00,
+	NS_IE_VCI		= 0x01,
+	NS_IE_PDU		= 0x02,
+	NS_IE_BVCI		= 0x03,
+	NS_IE_NSEI		= 0x04,
+	/* TS 48.016 Section 10.3, Table 10.3.1 */
+	NS_IE_IPv4_LIST		= 0x05,
+	NS_IE_IPv6_LIST		= 0x06,
+	NS_IE_MAX_NR_NSVC	= 0x07,
+	NS_IE_IPv4_EP_NR	= 0x08,
+	NS_IE_IPv6_EP_NR	= 0x09,
+	NS_IE_RESET_FLAG	= 0x0a,
+	NS_IE_IP_ADDR		= 0x0b,
+};
+
+/* TS 08.16, Section 10.3.2, Table 13 */
+enum ns_cause {
+	NS_CAUSE_TRANSIT_FAIL		= 0x00,
+	NS_CAUSE_OM_INTERVENTION	= 0x01,
+	NS_CAUSE_EQUIP_FAIL		= 0x02,
+	NS_CAUSE_NSVC_BLOCKED		= 0x03,
+	NS_CAUSE_NSVC_UNKNOWN		= 0x04,
+	NS_CAUSE_BVCI_UNKNOWN		= 0x05,
+	NS_CAUSE_SEM_INCORR_PDU		= 0x08,
+	NS_CAUSE_PDU_INCOMP_PSTATE	= 0x0a,
+	NS_CAUSE_PROTO_ERR_UNSPEC	= 0x0b,
+	NS_CAUSE_INVAL_ESSENT_IE	= 0x0c,
+	NS_CAUSE_MISSING_ESSENT_IE	= 0x0d,
+	/* TS 48.016 Section 10.3.2, Table 10.3.2.1 */
+	NS_CAUSE_INVAL_NR_IPv4_EP	= 0x0e,
+	NS_CAUSE_INVAL_NR_IPv6_EP	= 0x0f,
+	NS_CAUSE_INVAL_NR_NS_VC		= 0x10,
+	NS_CAUSE_INVAL_WEIGH		= 0x11,
+	NS_CAUSE_UNKN_IP_EP		= 0x12,
+	NS_CAUSE_UNKN_IP_ADDR		= 0x13,
+	NS_CAUSE_UNKN_IP_TEST_FAILED	= 0x14,
+};
+
+
+/* Our Implementation */
+#include <netinet/in.h>
+#include <osmocore/linuxlist.h>
+#include <osmocore/msgb.h>
+#include <osmocore/timer.h>
+#include <osmocore/select.h>
+
+#define NSE_S_BLOCKED	0x0001
+#define NSE_S_ALIVE	0x0002
+
+enum gprs_ns_ll {
+	GPRS_NS_LL_UDP,
+	GPRS_NS_LL_E1,
+};
+
+enum gprs_ns_evt {
+	GPRS_NS_EVT_UNIT_DATA,
+};
+
+struct gprs_nsvc;
+typedef int gprs_ns_cb_t(enum gprs_ns_evt event, struct gprs_nsvc *nsvc,
+			 struct msgb *msg, uint16_t bvci);
+
+/* An instance of the NS protocol stack */
+struct gprs_ns_inst {
+	/* callback to the user for incoming UNIT DATA IND */
+	gprs_ns_cb_t *cb;
+
+	/* linked lists of all NSVC in this instance */
+	struct llist_head gprs_nsvcs;
+
+	/* which link-layer are we based on? */
+	enum gprs_ns_ll ll;
+
+	union {
+		/* NS-over-IP specific bits */
+		struct {
+			struct bsc_fd fd;
+		} nsip;
+	};
+};
+
+enum nsvc_timer_mode {
+	/* standard timers */
+	NSVC_TIMER_TNS_TEST,
+	NSVC_TIMER_TNS_ALIVE,
+	NSVC_TIMER_TNS_RESET,
+	_NSVC_TIMER_NR,
+};
+
+struct gprs_nsvc {
+	struct llist_head list;
+	struct gprs_ns_inst *nsi;
+
+	uint16_t nsei;		/* end-to-end significance */
+	uint16_t nsvci;	/* uniquely identifies NS-VC at SGSN */
+
+	uint32_t state;
+	uint32_t remote_state;
+
+	struct timer_list timer;
+	enum nsvc_timer_mode timer_mode;
+	int alive_retries;
+
+	int remote_end_is_sgsn;
+
+	union {
+		struct {
+			struct sockaddr_in bts_addr;
+		} ip;
+	};
+};
+
+/* Create a new NS protocol instance */
+struct gprs_ns_inst *gprs_ns_instantiate(gprs_ns_cb_t *cb);
+
+/* Destroy a NS protocol instance */
+void gprs_ns_destroy(struct gprs_ns_inst *nsi);
+
+/* Listen for incoming GPRS packets */
+int nsip_listen(struct gprs_ns_inst *nsi, uint16_t udp_port);
+
+struct sockaddr_in;
+
+/* main entry point, here incoming NS frames enter */
+int gprs_ns_rcvmsg(struct gprs_ns_inst *nsi, struct msgb *msg,
+		   struct sockaddr_in *saddr);
+
+/* main function for higher layers (BSSGP) to send NS messages */
+int gprs_ns_sendmsg(struct gprs_ns_inst *nsi, struct msgb *msg);
+
+int gprs_ns_tx_reset(struct gprs_nsvc *nsvc, uint8_t cause);
+int gprs_ns_tx_block(struct gprs_nsvc *nsvc, uint8_t cause);
+int gprs_ns_tx_unblock(struct gprs_nsvc *nsvc);
+
+/* Listen for incoming GPRS packets */
+int nsip_listen(struct gprs_ns_inst *nsi, uint16_t udp_port);
+
+/* Establish a connection (from the BSS) to the SGSN */
+struct gprs_nsvc *nsip_connect(struct gprs_ns_inst *nsi,
+				struct sockaddr_in *dest, uint16_t nsei,
+				uint16_t nsvci);
+#endif
diff --git a/openbsc/src/gprs/gprs_bssgp.c b/openbsc/src/gprs/gprs_bssgp.c
new file mode 100644
index 0000000..9fdfd32
--- /dev/null
+++ b/openbsc/src/gprs/gprs_bssgp.c
@@ -0,0 +1,448 @@
+/* GPRS BSSGP protocol implementation as per 3GPP TS 08.18 */
+
+/* (C) 2009-2010 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <errno.h>
+#include <stdint.h>
+
+#include <netinet/in.h>
+
+#include <osmocore/msgb.h>
+#include <osmocore/tlv.h>
+#include <osmocore/talloc.h>
+
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/gsm_04_08_gprs.h>
+#include <openbsc/gprs_bssgp.h>
+#include <openbsc/gprs_llc.h>
+#include <openbsc/gprs_ns.h>
+
+void *bssgp_tall_ctx = NULL;
+
+#define BVC_F_BLOCKED	0x0001
+
+/* The per-BTS context that we keep on the SGSN side of the BSSGP link */
+struct bssgp_bts_ctx {
+	struct llist_head list;
+
+	/* parsed RA ID and Cell ID of the remote BTS */
+	struct gprs_ra_id ra_id;
+	uint16_t cell_id;
+
+	/* NSEI and BVCI of underlying Gb link.  Together they
+	 * uniquely identify a link to a BTS (5.4.4) */
+	uint16_t bvci;
+	uint16_t nsei;
+
+	uint32_t bvc_state;
+
+	/* we might want to add this as a shortcut later, avoiding the NSVC
+	 * lookup for every packet, similar to a routing cache */
+	//struct gprs_nsvc *nsvc;
+};
+static LLIST_HEAD(bts_ctxts);
+
+/* Find a BTS Context based on parsed RA ID and Cell ID */
+struct bssgp_bts_ctx *btsctx_by_raid_cid(const struct gprs_ra_id *raid, uint16_t cid)
+{
+	struct bssgp_bts_ctx *bctx;
+
+	llist_for_each_entry(bctx, &bts_ctxts, list) {
+		if (!memcmp(&bctx->ra_id, raid, sizeof(bctx->ra_id)) &&
+		    bctx->cell_id == cid)
+			return bctx;
+	}
+	return NULL;
+}
+
+/* Find a BTS context based on BVCI+NSEI tuple */
+struct bssgp_bts_ctx *btsctx_by_bvci_nsei(uint16_t bvci, uint16_t nsei)
+{
+	struct bssgp_bts_ctx *bctx;
+
+	llist_for_each_entry(bctx, &bts_ctxts, list) {
+		if (bctx->nsei == nsei && bctx->bvci == bvci)
+			return bctx;
+	}
+	return NULL;
+}
+
+struct bssgp_bts_ctx *btsctx_alloc(uint16_t bvci, uint16_t nsei)
+{
+	struct bssgp_bts_ctx *ctx;
+
+	ctx = talloc_zero(bssgp_tall_ctx, struct bssgp_bts_ctx);
+	if (!ctx)
+		return NULL;
+	ctx->bvci = bvci;
+	ctx->nsei = nsei;
+	llist_add(&ctx->list, &bts_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);
+}
+
+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 ntohs(*(uint16_t *) (buf+6));
+}
+
+/* Chapter 8.4 BVC-Reset Procedure */
+static int bssgp_rx_bvc_reset(struct msgb *msg, struct tlv_parsed *tp,	
+			      uint16_t ns_bvci)
+{
+	struct bssgp_bts_ctx *bctx;
+	uint16_t nsei = msgb_nsei(msg);
+	uint16_t bvci;
+	int rc;
+
+	bvci = ntohs(*(uint16_t *)TLVP_VAL(tp, BSSGP_IE_BVCI));
+	DEBUGPC(DBSSGP, "BVCI=%u, 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);
+
+	/* 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 RESET BVCI=%u "
+				"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);
+	}
+
+	/* Acknowledge the RESET to the BTS */
+	rc = bssgp_tx_simple_bvci(BSSGP_PDUT_BVC_RESET_ACK,
+				  nsei, bvci, ns_bvci);
+	return 0;
+}
+
+/* Uplink unit-data */
+static int bssgp_rx_ul_ud(struct msgb *msg)
+{
+	struct bssgp_ud_hdr *budh = (struct bssgp_ud_hdr *) msgb_bssgph(msg);
+	int data_len = msgb_bssgp_len(msg) - sizeof(*budh);
+	struct tlv_parsed tp;
+	int rc;
+
+	DEBUGP(DBSSGP, "BSSGP UL-UD\n");
+
+	/* extract TLLI and parse TLV IEs */
+	msgb_tlli(msg) = ntohl(budh->tlli);
+	rc = bssgp_tlv_parse(&tp, budh->data, data_len);
+
+	/* 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))
+		return -EIO;
+
+	/* FIXME: lookup bssgp_bts_ctx based on BVCI + NSEI */
+
+	/* store pointer to LLC header and CELL ID in msgb->cb */
+	msgb_llch(msg) = TLVP_VAL(&tp, BSSGP_IE_LLC_PDU);
+	msgb_bcid(msg) = TLVP_VAL(&tp, BSSGP_IE_CELL_ID);
+
+	return gprs_llc_rcvmsg(msg, &tp);
+}
+
+static int bssgp_rx_suspend(struct msgb *msg)
+{
+	struct bssgp_normal_hdr *bgph =
+			(struct bssgp_normal_hdr *) msgb_bssgph(msg);
+	int data_len = msgb_bssgp_len(msg) - sizeof(*bgph);
+	struct tlv_parsed tp;
+	int rc;
+
+	DEBUGP(DBSSGP, "BSSGP SUSPEND\n");
+
+	rc = bssgp_tlv_parse(&tp, bgph->data, data_len);
+	if (rc < 0)
+		return rc;
+
+	if (!TLVP_PRESENT(&tp, BSSGP_IE_TLLI) ||
+	    !TLVP_PRESENT(&tp, BSSGP_IE_ROUTEING_AREA))
+		return -EIO;
+
+	/* FIXME: pass the SUSPEND request to GMM */
+	/* SEND SUSPEND_ACK or SUSPEND_NACK */
+}
+
+static int bssgp_rx_resume(struct msgb *msg)
+{
+	struct bssgp_normal_hdr *bgph =
+			(struct bssgp_normal_hdr *) msgb_bssgph(msg);
+	int data_len = msgb_bssgp_len(msg) - sizeof(*bgph);
+	struct tlv_parsed tp;
+	int rc;
+
+	DEBUGP(DBSSGP, "BSSGP RESUME\n");
+
+	rc = bssgp_tlv_parse(&tp, bgph->data, data_len);
+	if (rc < 0)
+		return rc;
+
+	if (!TLVP_PRESENT(&tp, BSSGP_IE_TLLI) ||
+	    !TLVP_PRESENT(&tp, BSSGP_IE_ROUTEING_AREA) ||
+	    !TLVP_PRESENT(&tp, BSSGP_IE_SUSPEND_REF_NR))
+		return -EIO;
+
+	/* FIXME: pass the RESUME request to GMM */
+	/* SEND RESUME_ACK or RESUME_NACK */
+}
+
+static int bssgp_rx_fc_bvc(struct msgb *msg, struct tlv_parsed *tp)
+{
+
+	DEBUGP(DBSSGP, "BSSGP FC BVC\n");
+
+	if (!TLVP_PRESENT(tp, BSSGP_IE_TAG) ||
+	    !TLVP_PRESENT(tp, BSSGP_IE_BVC_BUCKET_SIZE) ||
+	    !TLVP_PRESENT(tp, BSSGP_IE_BUCKET_LEAK_RATE) ||
+	    !TLVP_PRESENT(tp, BSSGP_IE_BMAX_DEFAULT_MS) ||
+	    !TLVP_PRESENT(tp, BSSGP_IE_R_DEFAULT_MS))
+		return bssgp_tx_status(BSSGP_CAUSE_MISSING_MAND_IE, NULL, msg);
+
+	/* FIXME: actually implement flow control */
+
+	/* Send FLOW_CONTROL_BVC_ACK */
+	return bssgp_tx_fc_bvc_ack(msgb_nsei(msg), *TLVP_VAL(tp, BSSGP_IE_TAG),
+				   msgb_bvci(msg));
+}
+
+/* We expect msgb_bssgph() to point to the BSSGP header */
+int gprs_bssgp_rcvmsg(struct msgb *msg)
+{
+	struct bssgp_normal_hdr *bgph =
+			(struct bssgp_normal_hdr *) msgb_bssgph(msg);
+	struct tlv_parsed tp;
+	uint8_t pdu_type = bgph->pdu_type;
+	int data_len = msgb_bssgp_len(msg) - sizeof(*bgph);
+	uint16_t bvci;	/* PTP BVCI */
+	uint16_t ns_bvci = msgb_bvci(msg);
+	int rc = 0;
+
+	/* Identifiers from DOWN: NSEI, BVCI (both in msg->cb) */
+
+	/* UNITDATA BSSGP headers have TLLI in front */
+	if (pdu_type != BSSGP_PDUT_UL_UNITDATA &&
+	    pdu_type != BSSGP_PDUT_DL_UNITDATA)
+		rc = bssgp_tlv_parse(&tp, bgph->data, data_len);
+
+	switch (pdu_type) {
+	case BSSGP_PDUT_UL_UNITDATA:
+		/* some LLC data from the MS */
+		rc = bssgp_rx_ul_ud(msg);
+		break;
+	case BSSGP_PDUT_RA_CAPABILITY:
+		/* BSS requests RA capability or IMSI */
+		DEBUGP(DBSSGP, "BSSGP RA CAPABILITY UPDATE\n");
+		/* FIXME: send RA_CAPA_UPDATE_ACK */
+		break;
+	case BSSGP_PDUT_RADIO_STATUS:
+		DEBUGP(DBSSGP, "BSSGP RADIO STATUS\n");
+		/* BSS informs us of some exception */
+		/* FIXME: notify GMM */
+		break;
+	case BSSGP_PDUT_SUSPEND:
+		/* MS wants to suspend */
+		rc = bssgp_rx_suspend(msg);
+		break;
+	case BSSGP_PDUT_RESUME:
+		/* MS wants to resume */
+		rc = bssgp_rx_resume(msg);
+		break;
+	case BSSGP_PDUT_FLUSH_LL:
+		/* BSS informs MS has moved to one cell to other cell */
+		DEBUGP(DBSSGP, "BSSGP FLUSH LL\n");
+		/* FIXME: notify GMM */
+		/* Send FLUSH_LL_ACK */
+		break;
+	case BSSGP_PDUT_LLC_DISCARD:
+		/* BSS informs that some LLC PDU's have been discarded */
+		DEBUGP(DBSSGP, "BSSGP LLC DISCARDED\n");
+		/* FIXME: notify GMM */
+		break;
+	case BSSGP_PDUT_FLOW_CONTROL_BVC:
+		/* BSS informs us of available bandwidth in Gb interface */
+		rc = bssgp_rx_fc_bvc(msg, &tp);
+		break;
+	case BSSGP_PDUT_FLOW_CONTROL_MS:
+		/* BSS informs us of available bandwidth to one MS */
+		DEBUGP(DBSSGP, "BSSGP FC MS\n");
+		/* FIXME: actually implement flow control */
+		/* FIXME: Send FLOW_CONTROL_MS_ACK */
+		break;
+	case BSSGP_PDUT_BVC_BLOCK:
+		/* BSS tells us that BVC shall be blocked */
+		DEBUGP(DBSSGP, "BSSGP BVC BLOCK ");
+		if (!TLVP_PRESENT(&tp, BSSGP_IE_BVCI) ||
+		    !TLVP_PRESENT(&tp, BSSGP_IE_CAUSE))
+			goto err_mand_ie;
+		bvci = ntohs(*(uint16_t *)TLVP_VAL(&tp, BSSGP_IE_BVCI));
+		DEBUGPC(DBSSGP, "BVCI=%u, cause=%s\n", bvci,
+			bssgp_cause_str(*TLVP_VAL(&tp, BSSGP_IE_CAUSE)));
+		/* We always acknowledge the BLOCKing */
+		rc = bssgp_tx_simple_bvci(BSSGP_PDUT_BVC_BLOCK_ACK,
+					  msgb_nsei(msg), bvci, ns_bvci);
+		break;
+	case BSSGP_PDUT_BVC_UNBLOCK:
+		/* BSS tells us that BVC shall be unblocked */
+		DEBUGP(DBSSGP, "BSSGP BVC UNBLOCK ");
+		if (!TLVP_PRESENT(&tp, BSSGP_IE_BVCI))
+			goto err_mand_ie;
+		bvci = ntohs(*(uint16_t *)TLVP_VAL(&tp, BSSGP_IE_BVCI));
+		DEBUGPC(DBSSGP, "BVCI=%u\n", bvci);
+		/* We always acknowledge the unBLOCKing */
+		rc = bssgp_tx_simple_bvci(BSSGP_PDUT_BVC_UNBLOCK_ACK,
+					  msgb_nsei(msg), bvci, ns_bvci);
+		break;
+	case BSSGP_PDUT_BVC_RESET:
+		/* BSS tells us that BVC init is required */
+		DEBUGP(DBSSGP, "BSSGP BVC RESET ");
+		if (!TLVP_PRESENT(&tp, BSSGP_IE_BVCI) ||
+		    !TLVP_PRESENT(&tp, BSSGP_IE_CAUSE))
+			goto err_mand_ie;
+		rc = bssgp_rx_bvc_reset(msg, &tp, ns_bvci);
+		break;
+	case BSSGP_PDUT_STATUS:
+		/* Some exception has occurred */
+		/* FIXME: notify GMM */
+	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:
+	case BSSGP_PDUT_DELETE_BSS_PFC_ACK:
+		DEBUGP(DBSSGP, "BSSGP PDU type 0x%02x not [yet] implemented\n",
+			pdu_type);
+		break;
+	/* those only exist in the SGSN -> BSS direction */
+	case BSSGP_PDUT_DL_UNITDATA:
+	case BSSGP_PDUT_PAGING_PS:
+	case BSSGP_PDUT_PAGING_CS:
+	case BSSGP_PDUT_RA_CAPA_UPDATE_ACK:
+	case BSSGP_PDUT_SUSPEND_ACK:
+	case BSSGP_PDUT_SUSPEND_NACK:
+	case BSSGP_PDUT_RESUME_ACK:
+	case BSSGP_PDUT_RESUME_NACK:
+	case BSSGP_PDUT_FLUSH_LL_ACK:
+	case BSSGP_PDUT_FLOW_CONTROL_BVC_ACK:
+	case BSSGP_PDUT_FLOW_CONTROL_MS_ACK:
+	case BSSGP_PDUT_BVC_BLOCK_ACK:
+	case BSSGP_PDUT_BVC_UNBLOCK_ACK:
+	case BSSGP_PDUT_SGSN_INVOKE_TRACE:
+		DEBUGP(DBSSGP, "BSSGP PDU type 0x%02x only exists in DL\n",
+			pdu_type);
+		rc = -EINVAL;
+		break;
+	default:
+		DEBUGP(DBSSGP, "BSSGP PDU type 0x%02x unknown\n", pdu_type);
+		break;
+	}
+
+	return rc;
+err_mand_ie:
+	return bssgp_tx_status(BSSGP_CAUSE_MISSING_MAND_IE, NULL, msg);
+}
+
+/* Entry function from upper level (LLC), asking us to transmit a BSSGP PDU
+ * to a remote MS (identified by TLLI) at a BTS identified by its BVCI and NSEI */
+int gprs_bssgp_tx_dl_ud(struct msgb *msg)
+{
+	struct bssgp_bts_ctx *bctx;
+	struct bssgp_ud_hdr *budh;
+	uint8_t llc_pdu_tlv_hdr_len = 2;
+	uint8_t *llc_pdu_tlv, *qos_profile;
+	uint16_t pdu_lifetime = 1000; /* centi-seconds */
+	uint8_t qos_profile_default[3] = { 0x00, 0x00, 0x21 };
+	uint16_t msg_len = msg->len;
+	uint16_t bvci = msgb_bvci(msg);
+	uint16_t nsei = msgb_nsei(msg);
+
+	/* Identifiers from UP: TLLI, BVCI, NSEI (all in msgb->cb) */
+	if (bvci < 2) {
+		LOGP(DBSSGP, LOGL_ERROR, "Cannot send DL-UD to BVCI %u\n",
+			bvci);
+		return -EINVAL;
+	}
+
+	bctx = btsctx_by_bvci_nsei(bvci, nsei);
+	if (!bctx)
+		bctx = btsctx_alloc(bvci, nsei);
+
+	if (msg->len > TVLV_MAX_ONEBYTE)
+		llc_pdu_tlv_hdr_len += 1;
+
+	/* prepend the tag and length of the LLC-PDU TLV */
+	llc_pdu_tlv = msgb_push(msg, llc_pdu_tlv_hdr_len);
+	llc_pdu_tlv[0] = BSSGP_IE_LLC_PDU;
+	if (llc_pdu_tlv_hdr_len > 2) {
+		llc_pdu_tlv[1] = msg_len >> 8;
+		llc_pdu_tlv[2] = msg_len & 0xff;
+	} else {
+		llc_pdu_tlv[1] = msg_len & 0x3f;
+		llc_pdu_tlv[1] |= 0x80;
+	}
+
+	/* FIXME: optional elements */
+
+	/* prepend the pdu lifetime */
+	pdu_lifetime = htons(pdu_lifetime);
+	msgb_tvlv_push(msg, BSSGP_IE_PDU_LIFETIME, 2, (uint8_t *)&pdu_lifetime);
+
+	/* prepend the QoS profile, TLLI and pdu type */
+	budh = (struct bssgp_ud_hdr *) msgb_push(msg, sizeof(*budh));
+	memcpy(budh->qos_profile, qos_profile_default, sizeof(qos_profile_default));
+	budh->tlli = htonl(msgb_tlli(msg));
+	budh->pdu_type = BSSGP_PDUT_DL_UNITDATA;
+
+	/* Identifiers down: BVCI, NSEI (in msgb->cb) */
+
+	return gprs_ns_sendmsg(bssgp_nsi, msg);
+}
diff --git a/openbsc/src/gprs/gprs_bssgp_util.c b/openbsc/src/gprs/gprs_bssgp_util.c
new file mode 100644
index 0000000..d9b5175
--- /dev/null
+++ b/openbsc/src/gprs/gprs_bssgp_util.c
@@ -0,0 +1,119 @@
+/* GPRS BSSGP protocol implementation as per 3GPP TS 08.18 */
+
+/* (C) 2009-2010 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <errno.h>
+#include <stdint.h>
+
+#include <netinet/in.h>
+
+#include <osmocore/msgb.h>
+#include <osmocore/tlv.h>
+#include <osmocore/talloc.h>
+
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/gprs_bssgp.h>
+#include <openbsc/gprs_ns.h>
+
+struct gprs_ns_inst *bssgp_nsi;
+
+/* BSSGP Protocol specific, not implementation specific */
+/* FIXME: This needs to go into libosmocore after finished */
+
+/* Chapter 11.3.9 / Table 11.10: Cause coding */
+static const struct value_string bssgp_cause_strings[] = {
+	{ BSSGP_CAUSE_PROC_OVERLOAD,	"Processor overload" },
+	{ BSSGP_CAUSE_EQUIP_FAIL,	"Equipment Failure" },
+	{ BSSGP_CAUSE_TRASIT_NET_FAIL,	"Transit netowkr service failure" },
+	{ BSSGP_CAUSE_CAPA_GREATER_0KPBS,"Transmission capacity modified" },
+	{ BSSGP_CAUSE_UNKNOWN_MS,	"Unknown MS" },
+	{ BSSGP_CAUSE_UNKNOWN_BVCI,	"Unknown BVCI" },
+	{ BSSGP_CAUSE_CELL_TRAF_CONG,	"Cell traffic congestion" },
+	{ BSSGP_CAUSE_SGSN_CONG,	"SGSN congestion" },
+	{ BSSGP_CAUSE_OML_INTERV,	"O&M intervention" },
+	{ BSSGP_CAUSE_BVCI_BLOCKED,	"BVCI blocked" },
+	{ BSSGP_CAUSE_PFC_CREATE_FAIL,	"PFC create failure" },
+	{ BSSGP_CAUSE_SEM_INCORR_PDU,	"Semantically incorrect PDU" },
+	{ BSSGP_CAUSE_INV_MAND_INF,	"Invalid mandatory information" },
+	{ BSSGP_CAUSE_MISSING_MAND_IE,	"Missing mandatory IE" },
+	{ BSSGP_CAUSE_MISSING_COND_IE,	"Missing conditional IE" },
+	{ BSSGP_CAUSE_UNEXP_COND_IE,	"Unexpected conditional IE" },
+	{ BSSGP_CAUSE_COND_IE_ERR,	"Conditional IE error" },
+	{ BSSGP_CAUSE_PDU_INCOMP_STATE,	"PDU incompatible with protocol state" },
+	{ BSSGP_CAUSE_PROTO_ERR_UNSPEC,	"Protocol error - unspecified" },
+	{ BSSGP_CAUSE_PDU_INCOMP_FEAT, 	"PDU not compatible with feature set" },
+	{ 0, NULL },
+};
+
+const char *bssgp_cause_str(enum gprs_bssgp_cause cause)
+{
+	return get_value_string(bssgp_cause_strings, cause);
+}
+
+
+struct msgb *bssgp_msgb_alloc(void)
+{
+	return msgb_alloc_headroom(4096, 128, "BSSGP");
+}
+
+/* Transmit a simple response such as BLOCK/UNBLOCK/RESET ACK/NACK */
+int bssgp_tx_simple_bvci(uint8_t pdu_type, uint16_t nsei,
+			 uint16_t bvci, uint16_t ns_bvci)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph =
+			(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	uint16_t _bvci;
+
+	msgb_nsei(msg) = nsei;
+	msgb_bvci(msg) = ns_bvci;
+
+	bgph->pdu_type = pdu_type;
+	_bvci = htons(bvci);
+	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+
+	return gprs_ns_sendmsg(bssgp_nsi, msg);
+}
+
+/* Chapter 10.4.14: Status */
+int bssgp_tx_status(uint8_t cause, uint16_t *bvci, struct msgb *orig_msg)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph =
+			(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+
+	DEBUGPC(DBSSGP, "BSSGP: TX STATUS, cause=%s\n", bssgp_cause_str(cause));
+	msgb_nsei(msg) = msgb_nsei(orig_msg);
+	msgb_bvci(msg) = 0;
+
+	bgph->pdu_type = BSSGP_PDUT_STATUS;
+	msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, &cause);
+	if (bvci) {
+		uint16_t _bvci = htons(*bvci);
+		msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+	}
+	if (orig_msg)
+		msgb_tvlv_put(msg, BSSGP_IE_PDU_IN_ERROR,
+			      msgb_bssgp_len(orig_msg), msgb_bssgph(orig_msg));
+
+	return gprs_ns_sendmsg(bssgp_nsi, msg);
+}
diff --git a/openbsc/src/gprs/gprs_ns.c b/openbsc/src/gprs/gprs_ns.c
new file mode 100644
index 0000000..69c96ca
--- /dev/null
+++ b/openbsc/src/gprs/gprs_ns.c
@@ -0,0 +1,715 @@
+/* GPRS Networks Service (NS) messages on the Gb interfacebvci = msgb_bvci(msg);
+ * 3GPP TS 08.16 version 8.0.1 Release 1999 / ETSI TS 101 299 V8.0.1 (2002-05) */
+
+/* (C) 2009-2010 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+/* Some introduction into NS:  NS is used typically on top of frame relay,
+ * but in the ip.access world it is encapsulated in UDP packets.  It serves
+ * as an intermediate shim betwen BSSGP and the underlying medium.  It doesn't
+ * do much, apart from providing congestion notification and status indication.
+ *
+ * Terms:
+ * 	NS		Network Service
+ *	NSVC		NS Virtual Connection
+ *	NSEI		NS Entity Identifier
+ *	NSVL		NS Virtual Link
+ *	NSVLI		NS Virtual Link Identifier
+ *	BVC		BSSGP Virtual Connection
+ *	BVCI		BSSGP Virtual Connection Identifier
+ *	NSVCG		NS Virtual Connection Goup
+ *	Blocked		NS-VC cannot be used for user traffic
+ *	Alive		Ability of a NS-VC to provide communication
+ *
+ *  There can be multiple BSSGP virtual connections over one (group of) NSVC's.  BSSGP will
+ * therefore identify the BSSGP virtual connection by a BVCI passed down to NS.
+ * NS then has to firgure out which NSVC's are responsible for this BVCI.
+ * Those mappings are administratively configured.
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdint.h>
+
+#include <arpa/inet.h>
+
+#include <openbsc/gsm_data.h>
+#include <osmocore/msgb.h>
+#include <osmocore/tlv.h>
+#include <osmocore/talloc.h>
+#include <osmocore/select.h>
+#include <openbsc/debug.h>
+#include <openbsc/signal.h>
+#include <openbsc/gprs_ns.h>
+#include <openbsc/gprs_bssgp.h>
+
+#define NS_ALLOC_SIZE	1024
+
+static const struct tlv_definition ns_att_tlvdef = {
+	.def = {
+		[NS_IE_CAUSE]	= { TLV_TYPE_TvLV, 0 },
+		[NS_IE_VCI]	= { TLV_TYPE_TvLV, 0 },
+		[NS_IE_PDU]	= { TLV_TYPE_TvLV, 0 },
+		[NS_IE_BVCI]	= { TLV_TYPE_TvLV, 0 },
+		[NS_IE_NSEI]	= { TLV_TYPE_TvLV, 0 },
+	},
+};
+
+/* Lookup struct gprs_nsvc based on NSVCI */
+static struct gprs_nsvc *nsvc_by_nsvci(struct gprs_ns_inst *nsi,
+					uint16_t nsvci)
+{
+	struct gprs_nsvc *nsvc;
+	llist_for_each_entry(nsvc, &nsi->gprs_nsvcs, list) {
+		if (nsvc->nsvci == nsvci)
+			return nsvc;
+	}
+	return NULL;
+}
+
+/* Lookup struct gprs_nsvc based on NSVCI */
+static struct gprs_nsvc *nsvc_by_nsei(struct gprs_ns_inst *nsi,
+					uint16_t nsei)
+{
+	struct gprs_nsvc *nsvc;
+	llist_for_each_entry(nsvc, &nsi->gprs_nsvcs, list) {
+		if (nsvc->nsei == nsei)
+			return nsvc;
+	}
+	return NULL;
+}
+
+
+/* Lookup struct gprs_nsvc based on remote peer socket addr */
+static struct gprs_nsvc *nsvc_by_rem_addr(struct gprs_ns_inst *nsi,
+					  struct sockaddr_in *sin)
+{
+	struct gprs_nsvc *nsvc;
+	llist_for_each_entry(nsvc, &nsi->gprs_nsvcs, list) {
+		if (!memcmp(&nsvc->ip.bts_addr, sin, sizeof(*sin)))
+			return nsvc;
+	}
+	return NULL;
+}
+
+static void gprs_ns_timer_cb(void *data);
+
+static struct gprs_nsvc *nsvc_create(struct gprs_ns_inst *nsi, uint16_t nsvci)
+{
+	struct gprs_nsvc *nsvc;
+
+	nsvc = talloc_zero(nsi, struct gprs_nsvc);
+	nsvc->nsvci = nsvci;
+	/* before RESET procedure: BLOCKED and DEAD */
+	nsvc->state = NSE_S_BLOCKED;
+	nsvc->nsi = nsi;
+	nsvc->timer.cb = gprs_ns_timer_cb;
+	nsvc->timer.data = nsvc;
+
+	llist_add(&nsvc->list, &nsi->gprs_nsvcs);
+
+	return nsvc;
+}
+
+static void ns_dispatch_signal(struct gprs_nsvc *nsvc, unsigned int signal,
+			       uint8_t cause)
+{
+	struct ns_signal_data nssd;
+
+	nssd.nsvc = nsvc;
+	nssd.cause = cause;
+
+	dispatch_signal(SS_NS, signal, &nssd);
+}
+
+/* Section 10.3.2, Table 13 */
+static const struct value_string ns_cause_str[] = {
+	{ NS_CAUSE_TRANSIT_FAIL,	"Transit network failure" },
+	{ NS_CAUSE_OM_INTERVENTION, 	"O&M intervention" },
+	{ NS_CAUSE_EQUIP_FAIL,		"Equipment failure" },
+	{ NS_CAUSE_NSVC_BLOCKED,	"NS-VC blocked" },
+	{ NS_CAUSE_NSVC_UNKNOWN,	"NS-VC unknown" },
+	{ NS_CAUSE_BVCI_UNKNOWN,	"BVCI unknown" },
+	{ NS_CAUSE_SEM_INCORR_PDU,	"Semantically incorrect PDU" },
+	{ NS_CAUSE_PDU_INCOMP_PSTATE,	"PDU not compatible with protocol state" },
+	{ NS_CAUSE_PROTO_ERR_UNSPEC,	"Protocol error, unspecified" },
+	{ NS_CAUSE_INVAL_ESSENT_IE,	"Invalid essential IE" },
+	{ NS_CAUSE_MISSING_ESSENT_IE,	"Missing essential IE" },
+	{ 0, NULL }
+};
+
+const char *gprs_ns_cause_str(enum ns_cause cause)
+{
+	return get_value_string(ns_cause_str, cause);
+}
+
+static int nsip_sendmsg(struct gprs_nsvc *nsvc, struct msgb *msg);
+
+static int gprs_ns_tx(struct gprs_nsvc *nsvc, struct msgb *msg)
+{
+	int ret;
+
+	switch (nsvc->nsi->ll) {
+	case GPRS_NS_LL_UDP:
+		ret = nsip_sendmsg(nsvc, msg);
+		break;
+	default:
+		LOGP(DNS, LOGL_ERROR, "unsupported NS linklayer %u\n", nsvc->nsi->ll);
+		msgb_free(msg);
+		ret = -EIO;
+		break;
+	}
+	return ret;
+}
+
+static int gprs_ns_tx_simple(struct gprs_nsvc *nsvc, uint8_t pdu_type)
+{
+	struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "GPRS/NS");
+	struct gprs_ns_hdr *nsh;
+
+	if (!msg)
+		return -ENOMEM;
+
+	nsh = (struct gprs_ns_hdr *) msgb_put(msg, sizeof(*nsh));
+
+	nsh->pdu_type = pdu_type;
+
+	return gprs_ns_tx(nsvc, msg);
+}
+
+int gprs_ns_tx_reset(struct gprs_nsvc *nsvc, uint8_t cause)
+{
+	struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "GPRS/NS");
+	struct gprs_ns_hdr *nsh;
+	uint16_t nsvci = htons(nsvc->nsvci);
+	uint16_t nsei = htons(nsvc->nsei);
+
+	if (!msg)
+		return -ENOMEM;
+
+	nsh = (struct gprs_ns_hdr *) msgb_put(msg, sizeof(*nsh));
+	nsh->pdu_type = NS_PDUT_RESET;
+
+	msgb_tvlv_put(msg, NS_IE_CAUSE, 1, &cause);
+	msgb_tvlv_put(msg, NS_IE_VCI, 2, (uint8_t *) &nsvci);
+	msgb_tvlv_put(msg, NS_IE_NSEI, 2, (uint8_t *) &nsei);
+
+	return gprs_ns_tx(nsvc, msg);
+
+}
+
+int gprs_ns_tx_block(struct gprs_nsvc *nsvc, uint8_t cause)
+{
+	struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "GPRS/NS");
+	struct gprs_ns_hdr *nsh;
+	uint16_t nsvci = htons(nsvc->nsvci);
+
+	if (!msg)
+		return -ENOMEM;
+
+	/* be conservative and mark it as blocked even now! */
+	nsvc->state |= NSE_S_BLOCKED;
+
+	nsh = (struct gprs_ns_hdr *) msgb_put(msg, sizeof(*nsh));
+	nsh->pdu_type = NS_PDUT_BLOCK;
+
+	msgb_tvlv_put(msg, NS_IE_CAUSE, 1, &cause);
+	msgb_tvlv_put(msg, NS_IE_VCI, 2, (uint8_t *) &nsvci);
+
+	return gprs_ns_tx(nsvc, msg);
+}
+
+int gprs_ns_tx_unblock(struct gprs_nsvc *nsvc)
+{
+	return gprs_ns_tx_simple(nsvc, NS_PDUT_UNBLOCK);
+}
+
+#define NS_ALIVE_RETRIES  10	/* after 3 failed retransmit we declare BTS as dead */
+
+static const uint8_t timer_mode_tout[_NSVC_TIMER_NR] = {
+	[NSVC_TIMER_TNS_RESET]	= 60,
+	[NSVC_TIMER_TNS_ALIVE]	= 3,
+	[NSVC_TIMER_TNS_TEST]	= 30,
+};
+
+static void nsvc_start_timer(struct gprs_nsvc *nsvc, enum nsvc_timer_mode mode)
+{
+	nsvc->alive_retries = 0;
+
+	if (bsc_timer_pending(&nsvc->timer))
+		bsc_del_timer(&nsvc->timer);
+
+	nsvc->timer_mode = mode;
+	bsc_schedule_timer(&nsvc->timer, timer_mode_tout[mode], 0);
+}
+
+static void gprs_ns_timer_cb(void *data)
+{
+	struct gprs_nsvc *nsvc = data;
+
+	switch (nsvc->timer_mode) {
+	case NSVC_TIMER_TNS_ALIVE:
+		/* Tns-alive case: we expired without response ! */
+		nsvc->alive_retries++;
+		if (nsvc->alive_retries > NS_ALIVE_RETRIES) {
+			/* mark as dead and blocked */
+			nsvc->state = NSE_S_BLOCKED;
+			DEBUGP(DNS, "NSEI=%u Tns-alive expired more then "
+				"%u times, blocking NS-VC\n", nsvc->nsei,
+				NS_ALIVE_RETRIES);
+			/* FIXME: inform higher layers */
+			return;
+		}
+		nsvc_start_timer(nsvc, NSVC_TIMER_TNS_ALIVE);
+		break;
+	case NSVC_TIMER_TNS_TEST:
+		/* Tns-test case: send NS-ALIVE PDU */
+		gprs_ns_tx_simple(nsvc, NS_PDUT_ALIVE);
+		/* start Tns-alive timer */
+		nsvc_start_timer(nsvc, NSVC_TIMER_TNS_ALIVE);
+		break;
+	case NSVC_TIMER_TNS_RESET:
+		/* Chapter 7.3: Re-send the RESET */
+		gprs_ns_tx_reset(nsvc, NS_CAUSE_OM_INTERVENTION);
+		nsvc_start_timer(nsvc, NSVC_TIMER_TNS_RESET);
+		break;
+	case _NSVC_TIMER_NR:
+		break;
+	}
+}
+
+/* Section 9.2.6 */
+static int gprs_ns_tx_reset_ack(struct gprs_nsvc *nsvc)
+{
+	struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "GPRS/NS");
+	struct gprs_ns_hdr *nsh;
+	uint16_t nsvci, nsei;
+
+	if (!msg)
+		return -ENOMEM;
+
+	nsvci = htons(nsvc->nsvci);
+	nsei = htons(nsvc->nsei);
+
+	nsh = (struct gprs_ns_hdr *) msgb_put(msg, sizeof(*nsh));
+
+	nsh->pdu_type = NS_PDUT_RESET_ACK;
+
+	DEBUGP(DNS, "NSEI=%u Tx NS RESET ACK (NSVCI=%u)\n",
+		nsvc->nsei, nsvc->nsvci);
+
+	msgb_tvlv_put(msg, NS_IE_VCI, 2, (uint8_t *)&nsvci);
+	msgb_tvlv_put(msg, NS_IE_NSEI, 2, (uint8_t *)&nsei);
+
+	return gprs_ns_tx(nsvc, msg);
+}
+
+/* Section 9.2.10: transmit side / NS-UNITDATA-REQUEST primitive */
+int gprs_ns_sendmsg(struct gprs_ns_inst *nsi, struct msgb *msg)
+{
+	struct gprs_nsvc *nsvc;
+	struct gprs_ns_hdr *nsh;
+	uint16_t bvci = msgb_bvci(msg);
+
+	nsvc = nsvc_by_nsei(nsi, msgb_nsei(msg));
+	if (!nsvc) {
+		LOGP(DNS, LOGL_ERROR, "Unable to resolve NSEI %u "
+			"to NS-VC!\n", msgb_nsei(msg));
+		return -EINVAL;
+	}
+
+	if (!(nsvc->state & NSE_S_ALIVE)) {
+		LOGP(DNS, LOGL_ERROR, "NSEI=%u is not alive, cannot send\n",
+			nsvc->nsei);
+		return -EBUSY;
+	}
+	if (nsvc->state & NSE_S_BLOCKED) {
+		LOGP(DNS, LOGL_ERROR, "NSEI=%u is blocked, cannot send\n",
+			nsvc->nsei);
+		return -EBUSY;
+	}
+
+	nsh = (struct gprs_ns_hdr *) msgb_push(msg, sizeof(*nsh) + 3);
+	if (!nsh) {
+		LOGP(DNS, LOGL_ERROR, "Not enough headroom for NS header\n");
+		return -EIO;
+	}
+
+	nsh->pdu_type = NS_PDUT_UNITDATA;
+	/* spare octet in data[0] */
+	nsh->data[1] = bvci >> 8;
+	nsh->data[2] = bvci & 0xff;
+
+	return gprs_ns_tx(nsvc, msg);
+}
+
+/* Section 9.2.10: receive side */
+static int gprs_ns_rx_unitdata(struct gprs_nsvc *nsvc, struct msgb *msg)
+{
+	struct gprs_ns_hdr *nsh = (struct gprs_ns_hdr *)msg->l2h;
+	uint16_t bvci;
+
+	/* spare octet in data[0] */
+	bvci = nsh->data[1] << 8 | nsh->data[2];
+	msgb_bssgph(msg) = &nsh->data[3];
+	msgb_bvci(msg) = bvci;
+
+	/* call upper layer (BSSGP) */
+	return nsvc->nsi->cb(GPRS_NS_EVT_UNIT_DATA, nsvc, msg, bvci);
+}
+
+/* Section 9.2.7 */
+static int gprs_ns_rx_status(struct gprs_nsvc *nsvc, struct msgb *msg)
+{
+	struct gprs_ns_hdr *nsh = (struct gprs_ns_hdr *) msg->l2h;
+	struct tlv_parsed tp;
+	uint8_t cause;
+	int rc;
+
+	DEBUGP(DNS, "NSEI=%u NS STATUS ", nsvc->nsei);
+
+	rc = tlv_parse(&tp, &ns_att_tlvdef, nsh->data, msgb_l2len(msg), 0, 0);
+
+	if (!TLVP_PRESENT(&tp, NS_IE_CAUSE)) {
+		DEBUGPC(DNS, "missing cause IE\n");
+		return -EINVAL;
+	}
+
+	cause = *TLVP_VAL(&tp, NS_IE_CAUSE);
+	DEBUGPC(DNS, "cause=%s\n", gprs_ns_cause_str(cause));
+
+	return 0;
+}
+
+/* Section 7.3 */
+static int gprs_ns_rx_reset(struct gprs_nsvc *nsvc, struct msgb *msg)
+{
+	struct gprs_ns_hdr *nsh = (struct gprs_ns_hdr *) msg->l2h;
+	struct tlv_parsed tp;
+	uint8_t *cause;
+	uint16_t *nsvci, *nsei;
+	int rc;
+
+	rc = tlv_parse(&tp, &ns_att_tlvdef, nsh->data, msgb_l2len(msg), 0, 0);
+
+	if (!TLVP_PRESENT(&tp, NS_IE_CAUSE) ||
+	    !TLVP_PRESENT(&tp, NS_IE_VCI) ||
+	    !TLVP_PRESENT(&tp, NS_IE_NSEI)) {
+		/* FIXME: respond with NS_CAUSE_MISSING_ESSENT_IE */
+		LOGP(DNS, LOGL_ERROR, "NS RESET Missing mandatory IE\n");
+		return -EINVAL;
+	}
+
+	cause = (uint8_t *) TLVP_VAL(&tp, NS_IE_CAUSE);
+	nsvci = (uint16_t *) TLVP_VAL(&tp, NS_IE_VCI);
+	nsei = (uint16_t *) TLVP_VAL(&tp, NS_IE_NSEI);
+
+	DEBUGP(DNS, "NSEI=%u NS RESET (NSVCI=%u, cause=%s)\n",
+		nsvc->nsvci, nsvc->nsei, gprs_ns_cause_str(*cause));
+
+	nsvc->state = NSE_S_BLOCKED | NSE_S_ALIVE;
+	nsvc->nsei = ntohs(*nsei);
+	nsvc->nsvci = ntohs(*nsvci);
+
+	/* mark the NS-VC as blocked and alive */
+	/* start the test procedure */
+	nsvc_start_timer(nsvc, NSVC_TIMER_TNS_ALIVE);
+
+	/* inform interested parties about the fact that this NSVC
+	 * has received RESET */
+	ns_dispatch_signal(nsvc, S_NS_RESET, *cause);
+
+	return gprs_ns_tx_reset_ack(nsvc);
+}
+
+static int gprs_ns_rx_block(struct gprs_nsvc *nsvc, struct msgb *msg)
+{
+	struct gprs_ns_hdr *nsh = (struct gprs_ns_hdr *) msg->l2h;
+	struct tlv_parsed tp;
+	uint8_t *cause;
+	int rc;
+
+	DEBUGP(DNS, "NSEI=%u Rx NS BLOCK\n", nsvc->nsei);
+
+	nsvc->state |= NSE_S_BLOCKED;
+
+	rc = tlv_parse(&tp, &ns_att_tlvdef, nsh->data, msgb_l2len(msg), 0, 0);
+
+	if (!TLVP_PRESENT(&tp, NS_IE_CAUSE) ||
+	    !TLVP_PRESENT(&tp, NS_IE_VCI)) {
+		/* FIXME: respond with NS_CAUSE_MISSING_ESSENT_IE */
+		LOGP(DNS, LOGL_ERROR, "NS RESET Missing mandatory IE\n");
+		return -EINVAL;
+	}
+
+	cause = (uint8_t *) TLVP_VAL(&tp, NS_IE_CAUSE);
+	//nsvci = (uint16_t *) TLVP_VAL(&tp, NS_IE_VCI);
+
+	ns_dispatch_signal(nsvc, S_NS_BLOCK, *cause);
+
+	return gprs_ns_tx_simple(nsvc, NS_PDUT_BLOCK_ACK);
+}
+
+/* main entry point, here incoming NS frames enter */
+int gprs_ns_rcvmsg(struct gprs_ns_inst *nsi, struct msgb *msg,
+		   struct sockaddr_in *saddr)
+{
+	struct gprs_ns_hdr *nsh = (struct gprs_ns_hdr *) msg->l2h;
+	struct gprs_nsvc *nsvc;
+	int rc = 0;
+
+	/* look up the NSVC based on source address */
+	nsvc = nsvc_by_rem_addr(nsi, saddr);
+	if (!nsvc) {
+		/* Only the RESET procedure creates a new NSVC */
+		if (nsh->pdu_type != NS_PDUT_RESET) {
+			LOGP(DNS, LOGL_INFO, "Ignoring NS PDU type 0x%0x "
+				"from %s for non-existing NS-VC\n",
+				nsh->pdu_type, inet_ntoa(saddr->sin_addr));
+			//gprs_ns_tx_reset(nsvc, NS_CAUSE_NSVC_UNKNOWN);
+			return -EIO;
+		}
+		LOGP(DNS, LOGL_INFO, "Creating NS-VC for BSS at %s:%u\n",
+			inet_ntoa(saddr->sin_addr), ntohs(saddr->sin_port));
+		nsvc = nsvc_create(nsi, 0xffff);
+		nsvc->ip.bts_addr = *saddr;
+	} else
+		msgb_nsei(msg) = nsvc->nsei;
+
+	switch (nsh->pdu_type) {
+	case NS_PDUT_ALIVE:
+		/* remote end inquires whether we're still alive,
+		 * we need to respond with ALIVE_ACK */
+		rc = gprs_ns_tx_simple(nsvc, NS_PDUT_ALIVE_ACK);
+		break;
+	case NS_PDUT_ALIVE_ACK:
+		/* stop Tns-alive */
+		bsc_del_timer(&nsvc->timer);
+		/* start Tns-test */
+		nsvc_start_timer(nsvc, NSVC_TIMER_TNS_TEST);
+		if (nsvc->remote_end_is_sgsn) {
+			/* FIXME: this should be one level higher */
+			if (nsvc->state & NSE_S_BLOCKED)
+				rc = gprs_ns_tx_simple(nsvc, NS_PDUT_UNBLOCK);
+		}
+		break;
+	case NS_PDUT_UNITDATA:
+		/* actual user data */
+		rc = gprs_ns_rx_unitdata(nsvc, msg);
+		break;
+	case NS_PDUT_STATUS:
+		rc = gprs_ns_rx_status(nsvc, msg);
+		break;
+	case NS_PDUT_RESET:
+		rc = gprs_ns_rx_reset(nsvc, msg);
+		break;
+	case NS_PDUT_RESET_ACK:
+		DEBUGP(DNS, "NSEI=%u Rx NS RESET ACK\n", nsvc->nsei);
+		/* mark remote NS-VC as blocked + active */
+		nsvc->remote_state = NSE_S_BLOCKED | NSE_S_ALIVE;
+		if (nsvc->remote_end_is_sgsn) {
+			/* stop RESET timer */
+			bsc_del_timer(&nsvc->timer);
+			/* send ALIVE PDU */
+			rc = gprs_ns_tx_simple(nsvc, NS_PDUT_ALIVE);
+			nsvc_start_timer(nsvc, NSVC_TIMER_TNS_ALIVE);
+			/* mark local state as BLOCKED + ALIVE */
+			nsvc->state = NSE_S_BLOCKED | NSE_S_ALIVE;
+		}
+		break;
+	case NS_PDUT_UNBLOCK:
+		/* Section 7.2: unblocking procedure */
+		DEBUGP(DNS, "NSEI=%u Rx NS UNBLOCK\n", nsvc->nsei);
+		nsvc->state &= ~NSE_S_BLOCKED;
+		ns_dispatch_signal(nsvc, S_NS_UNBLOCK, 0);
+		rc = gprs_ns_tx_simple(nsvc, NS_PDUT_UNBLOCK_ACK);
+		break;
+	case NS_PDUT_UNBLOCK_ACK:
+		DEBUGP(DNS, "NSEI=%u Rx NS UNBLOCK ACK\n", nsvc->nsei);
+		/* mark remote NS-VC as unblocked + active */
+		nsvc->remote_state = NSE_S_ALIVE;
+		if (nsvc->remote_end_is_sgsn)
+			nsvc->state = NSE_S_ALIVE;
+		break;
+	case NS_PDUT_BLOCK:
+		rc = gprs_ns_rx_block(nsvc, msg);
+		break;
+	case NS_PDUT_BLOCK_ACK:
+		DEBUGP(DNS, "NSEI=%u Rx NS BLOCK ACK\n", nsvc->nsei);
+		/* mark remote NS-VC as blocked + active */
+		nsvc->remote_state = NSE_S_BLOCKED | NSE_S_ALIVE;
+		break;
+	default:
+		DEBUGP(DNS, "NSEI=%u Rx Unknown NS PDU type 0x%02x\n",
+			nsvc->nsei, nsh->pdu_type);
+		rc = -EINVAL;
+		break;
+	}
+	return rc;
+}
+
+struct gprs_ns_inst *gprs_ns_instantiate(gprs_ns_cb_t *cb)
+{
+	struct gprs_ns_inst *nsi = talloc_zero(tall_bsc_ctx, struct gprs_ns_inst);
+
+	nsi->cb = cb;
+	INIT_LLIST_HEAD(&nsi->gprs_nsvcs);
+
+	return nsi;
+}
+
+void gprs_ns_destroy(struct gprs_ns_inst *nsi)
+{
+	/* FIXME: clear all timers */
+
+	/* recursively free the NSI and all its NSVCs */
+	talloc_free(nsi);
+}
+
+
+/* NS-over-IP code, according to 3GPP TS 48.016 Chapter 6.2
+ * We don't support Size Procedure, Configuration Procedure, ChangeWeight Procedure */
+
+/* Read a single NS-over-IP message */
+static struct msgb *read_nsip_msg(struct bsc_fd *bfd, int *error,
+				  struct sockaddr_in *saddr)
+{
+	struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "Abis/IP/GPRS-NS");
+	int ret = 0;
+	socklen_t saddr_len = sizeof(*saddr);
+
+	if (!msg) {
+		*error = -ENOMEM;
+		return NULL;
+	}
+
+	ret = recvfrom(bfd->fd, msg->data, NS_ALLOC_SIZE, 0,
+			(struct sockaddr *)saddr, &saddr_len);
+	if (ret < 0) {
+		LOGP(DNS, LOGL_ERROR, "recv error %s during NSIP recv\n",
+			strerror(errno));
+		msgb_free(msg);
+		*error = ret;
+		return NULL;
+	} else if (ret == 0) {
+		msgb_free(msg);
+		*error = ret;
+		return NULL;
+	}
+
+	msg->l2h = msg->data;
+	msgb_put(msg, ret);
+
+	return msg;
+}
+
+static int handle_nsip_read(struct bsc_fd *bfd)
+{
+	int error;
+	struct sockaddr_in saddr;
+	struct gprs_ns_inst *nsi = bfd->data;
+	struct msgb *msg = read_nsip_msg(bfd, &error, &saddr);
+
+	if (!msg)
+		return error;
+
+	return gprs_ns_rcvmsg(nsi, msg, &saddr);
+}
+
+static int handle_nsip_write(struct bsc_fd *bfd)
+{
+	/* FIXME: actually send the data here instead of nsip_sendmsg() */
+	return -EIO;
+}
+
+int nsip_sendmsg(struct gprs_nsvc *nsvc, struct msgb *msg)
+{
+	int rc;
+	struct gprs_ns_inst *nsi = nsvc->nsi;
+	struct sockaddr_in *daddr = &nsvc->ip.bts_addr;
+
+	rc = sendto(nsi->nsip.fd.fd, msg->data, msg->len, 0,
+		  (struct sockaddr *)daddr, sizeof(*daddr));
+
+	talloc_free(msg);
+
+	return rc;
+}
+
+/* UDP Port 23000 carries the LLC-in-BSSGP-in-NS protocol stack */
+static int nsip_fd_cb(struct bsc_fd *bfd, unsigned int what)
+{
+	int rc = 0;
+
+	if (what & BSC_FD_READ)
+		rc = handle_nsip_read(bfd);
+	if (what & BSC_FD_WRITE)
+		rc = handle_nsip_write(bfd);
+
+	return rc;
+}
+
+
+/* FIXME: this is currently in input/ipaccess.c */
+extern int make_sock(struct bsc_fd *bfd, int proto, uint16_t port,
+		     int (*cb)(struct bsc_fd *fd, unsigned int what));
+
+/* Listen for incoming GPRS packets */
+int nsip_listen(struct gprs_ns_inst *nsi, uint16_t udp_port)
+{
+	int ret;
+
+	ret = make_sock(&nsi->nsip.fd, IPPROTO_UDP, udp_port, nsip_fd_cb);
+	if (ret < 0)
+		return ret;
+
+	nsi->ll = GPRS_NS_LL_UDP;
+	nsi->nsip.fd.data = nsi;
+
+	return ret;
+}
+
+/* Establish a connection (from the BSS) to the SGSN */
+struct gprs_nsvc *nsip_connect(struct gprs_ns_inst *nsi,
+				struct sockaddr_in *dest, uint16_t nsei,
+				uint16_t nsvci)
+{
+	struct gprs_nsvc *nsvc;
+
+	nsvc = nsvc_by_rem_addr(nsi, dest);
+	if (!nsvc) {
+		nsvc = nsvc_create(nsi, nsvci);
+		nsvc->ip.bts_addr = *dest;
+	}
+	nsvc->nsei = nsei;
+	nsvc->nsvci = nsvci;
+	nsvc->remote_end_is_sgsn = 1;
+
+	/* Initiate a RESET procedure */
+	if (gprs_ns_tx_reset(nsvc, NS_CAUSE_OM_INTERVENTION) < 0) {
+		LOGP(DNS, LOGL_ERROR, "NSEI=%u, error resetting NS-VC\n",
+			nsei);
+	}
+	/* run a timer and re-transmit the reset request? */
+	nsvc_start_timer(nsvc, NSVC_TIMER_TNS_RESET);
+
+	return nsvc;
+}