diff --git a/openbsc/tests/gbproxy/gbproxy_test.c b/openbsc/tests/gbproxy/gbproxy_test.c
new file mode 100644
index 0000000..6e7be64
--- /dev/null
+++ b/openbsc/tests/gbproxy/gbproxy_test.c
@@ -0,0 +1,409 @@
+/* test routines for gbproxy
+ * send NS messages to the gbproxy and dumps what happens
+ * (C) 2013 by sysmocom s.f.m.c. GmbH
+ * Author: Jacob Erlbeck <jerlbeck@sysmocom.de>
+ */
+
+#undef _GNU_SOURCE
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <getopt.h>
+#include <dlfcn.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/application.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/signal.h>
+#include <osmocom/core/rate_ctr.h>
+#include <osmocom/gprs/gprs_msgb.h>
+#include <osmocom/gprs/gprs_ns.h>
+#include <osmocom/gprs/gprs_bssgp.h>
+
+#include <openbsc/gb_proxy.h>
+
+#define REMOTE_BSS_ADDR 0x01020304
+#define REMOTE_SGSN_ADDR 0x05060708
+
+#define SGSN_NSEI 0xfffe
+
+struct gbproxy_config gbcfg;
+
+static int gprs_process_message(struct gprs_ns_inst *nsi, const char *text, struct sockaddr_in *peer, const unsigned char* data, size_t data_len);
+
+static void send_ns_reset(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr,
+			  enum ns_cause cause, uint16_t nsvci, uint16_t nsei)
+{
+	/* GPRS Network Service, PDU type: NS_RESET,
+	 */
+	unsigned char msg[12] = {
+		0x02, 0x00, 0x81, 0x01, 0x01, 0x82, 0x11, 0x22,
+		0x04, 0x82, 0x11, 0x22
+	};
+
+	msg[3] = cause;
+	msg[6] = nsvci / 256;
+	msg[7] = nsvci % 256;
+	msg[10] = nsei / 256;
+	msg[11] = nsei % 256;
+
+	gprs_process_message(nsi, "RESET", src_addr, msg, sizeof(msg));
+}
+
+static void send_ns_alive(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr)
+{
+	/* GPRS Network Service, PDU type: NS_ALIVE */
+	unsigned char msg[1] = {
+		0x0a
+	};
+
+	gprs_process_message(nsi, "ALIVE", src_addr, msg, sizeof(msg));
+}
+
+static void send_ns_alive_ack(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr)
+{
+	/* GPRS Network Service, PDU type: NS_ALIVE_ACK */
+	unsigned char msg[1] = {
+		0x0b
+	};
+
+	gprs_process_message(nsi, "ALIVE_ACK", src_addr, msg, sizeof(msg));
+}
+
+static void send_ns_unblock(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr)
+{
+	/* GPRS Network Service, PDU type: NS_UNBLOCK */
+	unsigned char msg[1] = {
+		0x06
+	};
+
+	gprs_process_message(nsi, "UNBLOCK", src_addr, msg, sizeof(msg));
+}
+
+static void send_ns_unitdata(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr,
+			     uint16_t nsbvci,
+			     const unsigned char *bssgp_msg, size_t bssgp_msg_size)
+{
+	/* GPRS Network Service, PDU type: NS_UNITDATA */
+	unsigned char msg[4096] = {
+		0x00, 0x00, 0x00, 0x00
+	};
+
+	OSMO_ASSERT(bssgp_msg_size <= sizeof(msg) - 4);
+
+	msg[2] = nsbvci / 256;
+	msg[3] = nsbvci % 256;
+	memcpy(msg + 4, bssgp_msg, bssgp_msg_size);
+
+	gprs_process_message(nsi, "UNITDATA", src_addr, msg, bssgp_msg_size + 4);
+}
+
+static void send_bssgp_reset(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr,
+			     uint16_t bvci)
+{
+	/* GPRS Network Service, PDU type: NS_UNITDATA, BVCI 0
+	 * BSSGP RESET */
+	unsigned char msg[22] = {
+		0x22, 0x04, 0x82, 0x4a,
+		0x2e, 0x07, 0x81, 0x08, 0x08, 0x88, 0x10, 0x20,
+		0x30, 0x40, 0x50, 0x60, 0x10, 0x00
+	};
+
+	msg[3] = bvci / 256;
+	msg[4] = bvci % 256;
+
+	send_ns_unitdata(nsi, src_addr, 0, msg, sizeof(msg));
+}
+
+static void setup_ns(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr,
+		     uint16_t nsvci, uint16_t nsei)
+{
+	printf("Setup NS-VC: remote 0x%08x:%d, "
+	       "NSVCI 0x%04x(%d), NSEI 0x%04x(%d)\n\n",
+	       ntohl(src_addr->sin_addr.s_addr), ntohs(src_addr->sin_port),
+	       nsvci, nsvci, nsei, nsei);
+
+	send_ns_reset(nsi, src_addr, NS_CAUSE_OM_INTERVENTION, nsvci, nsei);
+	send_ns_alive(nsi, src_addr);
+	send_ns_unblock(nsi, src_addr);
+	send_ns_alive_ack(nsi, src_addr);
+}
+
+static void setup_bssgp(struct gprs_ns_inst *nsi, struct sockaddr_in *src_addr,
+		     uint16_t bvci)
+{
+	printf("Setup BSSGP: remote 0x%08x:%d, "
+	       "BVCI 0x%04x(%d)\n\n",
+	       ntohl(src_addr->sin_addr.s_addr), ntohs(src_addr->sin_port),
+	       bvci, bvci);
+
+	send_bssgp_reset(nsi, src_addr, bvci);
+}
+
+int gprs_ns_rcvmsg(struct gprs_ns_inst *nsi, struct msgb *msg,
+		   struct sockaddr_in *saddr, enum gprs_ns_ll ll);
+
+/* override */
+int gprs_ns_callback(enum gprs_ns_evt event, struct gprs_nsvc *nsvc,
+			 struct msgb *msg, uint16_t bvci)
+{
+	printf("CALLBACK, event %d, msg length %d, bvci 0x%04x\n%s\n\n",
+			event, msgb_bssgp_len(msg), bvci,
+			osmo_hexdump(msgb_bssgph(msg), msgb_bssgp_len(msg)));
+
+	switch (event) {
+	case GPRS_NS_EVT_UNIT_DATA:
+		return gbprox_rcvmsg(msg, nsvc, bvci);
+	default:
+		break;
+	}
+	return 0;
+}
+
+/* override */
+ssize_t sendto(int sockfd, const void *buf, size_t len, int flags,
+		const struct sockaddr *dest_addr, socklen_t addrlen)
+{
+	typedef ssize_t (*sendto_t)(int, const void *, size_t, int,
+			const struct sockaddr *, socklen_t);
+	static sendto_t real_sendto = NULL;
+	uint32_t dest_host = htonl(((struct sockaddr_in *)dest_addr)->sin_addr.s_addr);
+
+	if (!real_sendto)
+		real_sendto = dlsym(RTLD_NEXT, "sendto");
+
+	if (dest_host == REMOTE_BSS_ADDR)
+		printf("MESSAGE to BSS, msg length %d\n%s\n\n", len, osmo_hexdump(buf, len));
+	else if (dest_host == REMOTE_SGSN_ADDR)
+		printf("MESSAGE to SGSN, msg length %d\n%s\n\n", len, osmo_hexdump(buf, len));
+	else
+		return real_sendto(sockfd, buf, len, flags, dest_addr, addrlen);
+
+	return len;
+}
+
+/* override */
+int gprs_ns_sendmsg(struct gprs_ns_inst *nsi, struct msgb *msg)
+{
+	uint16_t bvci = msgb_bvci(msg);
+	uint16_t nsei = msgb_nsei(msg);
+
+	unsigned char *buf = msg->data;
+	size_t len = msg->len;
+
+	if (nsei == SGSN_NSEI)
+		printf("NS UNITDATA MESSAGE to SGSN, BVCI 0x%04x, msg length %d\n%s\n\n",
+		       bvci, len, osmo_hexdump(buf, len));
+	else
+		printf("NS UNITDATA MESSAGE to BSS, BVCI 0x%04x, msg length %d\n%s\n\n",
+		       bvci, len, osmo_hexdump(buf, len));
+
+	return 0;
+}
+
+static void dump_rate_ctr_group(FILE *stream, const char *prefix,
+			    struct rate_ctr_group *ctrg)
+{
+	unsigned int i;
+
+	for (i = 0; i < ctrg->desc->num_ctr; i++) {
+		struct rate_ctr *ctr = &ctrg->ctr[i];
+		if (ctr->current && !strchr(ctrg->desc->ctr_desc[i].name, '.'))
+			fprintf(stream, " %s%s: %llu%s",
+				prefix, ctrg->desc->ctr_desc[i].description,
+				(long long)ctr->current,
+				"\n");
+	};
+}
+
+/* Signal handler for signals from NS layer */
+static int test_signal(unsigned int subsys, unsigned int signal,
+		  void *handler_data, void *signal_data)
+{
+	struct ns_signal_data *nssd = signal_data;
+	int rc;
+
+	if (subsys != SS_L_NS)
+		return 0;
+
+	switch (signal) {
+	case S_NS_RESET:
+		printf("==> got signal NS_RESET, NS-VC 0x%04x/%s\n",
+		       nssd->nsvc->nsvci,
+		       gprs_ns_ll_str(nssd->nsvc));
+		break;
+
+	case S_NS_ALIVE_EXP:
+		printf("==> got signal NS_ALIVE_EXP, NS-VC 0x%04x/%s\n",
+		       nssd->nsvc->nsvci,
+		       gprs_ns_ll_str(nssd->nsvc));
+		break;
+
+	case S_NS_BLOCK:
+		printf("==> got signal NS_BLOCK, NS-VC 0x%04x/%s\n",
+		       nssd->nsvc->nsvci,
+		       gprs_ns_ll_str(nssd->nsvc));
+		break;
+
+	case S_NS_UNBLOCK:
+		printf("==> got signal NS_UNBLOCK, NS-VC 0x%04x/%s\n",
+		       nssd->nsvc->nsvci,
+		       gprs_ns_ll_str(nssd->nsvc));
+		break;
+
+	case S_NS_REPLACED:
+		printf("==> got signal NS_REPLACED: 0x%04x/%s",
+		       nssd->nsvc->nsvci,
+		       gprs_ns_ll_str(nssd->nsvc));
+		printf(" -> 0x%04x/%s\n",
+		       nssd->old_nsvc->nsvci,
+		       gprs_ns_ll_str(nssd->old_nsvc));
+		break;
+
+	default:
+		printf("==> got signal %d, NS-VC 0x%04x/%s\n", signal,
+		       nssd->nsvc->nsvci,
+		       gprs_ns_ll_str(nssd->nsvc));
+		break;
+	}
+	printf("\n");
+	rc = gbprox_signal(subsys, signal, handler_data, signal_data);
+	return rc;
+}
+
+static int gprs_process_message(struct gprs_ns_inst *nsi, const char *text, struct sockaddr_in *peer, const unsigned char* data, size_t data_len)
+{
+	struct msgb *msg;
+	int ret;
+	if (data_len > NS_ALLOC_SIZE - NS_ALLOC_HEADROOM) {
+		fprintf(stderr, "message too long: %d\n", data_len);
+		return -1;
+	}
+
+	msg = gprs_ns_msgb_alloc();
+	memmove(msg->data, data, data_len);
+	msg->l2h = msg->data;
+	msgb_put(msg, data_len);
+
+	printf("PROCESSING %s from 0x%08x:%d\n%s\n\n",
+	       text, ntohl(peer->sin_addr.s_addr), ntohs(peer->sin_port),
+	       osmo_hexdump(data, data_len));
+
+	ret = gprs_ns_rcvmsg(nsi, msg, peer, GPRS_NS_LL_UDP);
+
+	printf("result (%s) = %d\n\n", text, ret);
+
+	msgb_free(msg);
+
+	return ret;
+}
+
+static void gprs_dump_nsi(struct gprs_ns_inst *nsi)
+{
+	struct gprs_nsvc *nsvc;
+
+	printf("Current NS-VCIs:\n");
+	llist_for_each_entry(nsvc, &nsi->gprs_nsvcs, list) {
+		struct sockaddr_in *peer = &(nsvc->ip.bts_addr);
+		printf("    VCI 0x%04x, NSEI 0x%04x, peer 0x%08x:%d\n",
+		       nsvc->nsvci, nsvc->nsei,
+		       ntohl(peer->sin_addr.s_addr), ntohs(peer->sin_port)
+		      );
+		dump_rate_ctr_group(stdout, "        ", nsvc->ctrg);
+	}
+	printf("\n");
+}
+
+static void test_gbproxy()
+{
+	struct gprs_ns_inst *nsi = gprs_ns_instantiate(gprs_ns_callback, NULL);
+	struct sockaddr_in bss_peer[4] = {{0},};
+
+	bssgp_nsi = nsi;
+	gbcfg.nsi = bssgp_nsi;
+	gbcfg.nsip_sgsn_nsei = SGSN_NSEI;
+
+	bss_peer[0].sin_family = AF_INET;
+	bss_peer[0].sin_port = htons(1111);
+	bss_peer[0].sin_addr.s_addr = htonl(REMOTE_BSS_ADDR);
+	bss_peer[1].sin_family = AF_INET;
+	bss_peer[1].sin_port = htons(2222);
+	bss_peer[1].sin_addr.s_addr = htonl(REMOTE_BSS_ADDR);
+	bss_peer[2].sin_family = AF_INET;
+	bss_peer[2].sin_port = htons(3333);
+	bss_peer[2].sin_addr.s_addr = htonl(REMOTE_BSS_ADDR);
+	bss_peer[3].sin_family = AF_INET;
+	bss_peer[3].sin_port = htons(4444);
+	bss_peer[3].sin_addr.s_addr = htonl(REMOTE_BSS_ADDR);
+
+	printf("--- Initialise BSS 1 ---\n\n");
+
+	setup_ns(nsi, &bss_peer[0], 0x1001, 0x1000);
+	setup_bssgp(nsi, &bss_peer[0], 0x1002);
+	gprs_dump_nsi(nsi);
+	gbprox_dump_peers(stdout, 0);
+
+	printf("--- Initialise BSS 2 ---\n\n");
+
+	setup_ns(nsi, &bss_peer[1], 0x2001, 0x2000);
+	setup_bssgp(nsi, &bss_peer[1], 0x2002);
+	gprs_dump_nsi(nsi);
+	gbprox_dump_peers(stdout, 0);
+
+	printf("--- Move BSS 1 to new port ---\n\n");
+
+	setup_ns(nsi, &bss_peer[2], 0x1001, 0x1000);
+	gprs_dump_nsi(nsi);
+	gbprox_dump_peers(stdout, 0);
+
+	printf("--- Move BSS 2 to former BSS 1 port ---\n\n");
+
+	setup_ns(nsi, &bss_peer[0], 0x2001, 0x2000);
+	gprs_dump_nsi(nsi);
+	gbprox_dump_peers(stdout, 0);
+
+	printf("--- Move BSS 1 to current BSS 2 port ---\n\n");
+
+	setup_ns(nsi, &bss_peer[0], 0x2001, 0x2000);
+	gprs_dump_nsi(nsi);
+	gbprox_dump_peers(stdout, 0);
+
+	printf("--- Move BSS 2 to new port ---\n\n");
+
+	setup_ns(nsi, &bss_peer[3], 0x2001, 0x2000);
+	gprs_dump_nsi(nsi);
+	gbprox_dump_peers(stdout, 0);
+
+	printf("--- Move BSS 2 to former BSS 1 port ---\n\n");
+
+	setup_ns(nsi, &bss_peer[2], 0x2001, 0x2000);
+	gprs_dump_nsi(nsi);
+	gbprox_dump_peers(stdout, 0);
+
+	gprs_ns_destroy(nsi);
+	nsi = NULL;
+}
+
+
+static struct log_info info = {};
+
+int main(int argc, char **argv)
+{
+	osmo_init_logging(&info);
+	log_set_use_color(osmo_stderr_target, 0);
+	log_set_print_filename(osmo_stderr_target, 0);
+	osmo_signal_register_handler(SS_L_NS, &test_signal, NULL);
+
+	printf("===== NS protocol test START\n");
+	test_gbproxy();
+	printf("===== NS protocol test END\n\n");
+
+	exit(EXIT_SUCCESS);
+}