diff --git a/openbsc/src/gprs/Makefile.am b/openbsc/src/gprs/Makefile.am
index f937362..d45aaee 100644
--- a/openbsc/src/gprs/Makefile.am
+++ b/openbsc/src/gprs/Makefile.am
@@ -22,7 +22,8 @@
 osmo_sgsn_SOURCES =	gprs_gmm.c gprs_sgsn.c gprs_sndcp.c gprs_sndcp_vty.c \
 			sgsn_main.c sgsn_vty.c sgsn_libgtp.c \
 			gprs_llc.c gprs_llc_parse.c gprs_llc_vty.c crc24.c \
-			sgsn_ctrl.c sgsn_auth.c gprs_subscriber.c
+			sgsn_ctrl.c sgsn_auth.c gprs_subscriber.c \
+			gprs_gsup_messages.c gprs_utils.c
 osmo_sgsn_LDADD = 	\
 			$(top_builddir)/src/libcommon/libcommon.a \
 			-lgtp $(OSMO_LIBS) $(LIBOSMOABIS_LIBS)
diff --git a/openbsc/src/gprs/gprs_gsup_messages.c b/openbsc/src/gprs/gprs_gsup_messages.c
new file mode 100644
index 0000000..c3d187d
--- /dev/null
+++ b/openbsc/src/gprs/gprs_gsup_messages.c
@@ -0,0 +1,405 @@
+/* GPRS Subscriber Update Protocol message encoder/decoder */
+
+/*
+ * (C) 2014 by Sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Jacob Erlbeck
+ *
+ * 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 <openbsc/gprs_gsup_messages.h>
+
+#include <openbsc/debug.h>
+#include <openbsc/gprs_utils.h>
+
+#include <osmocom/gsm/tlv.h>
+#include <osmocom/core/msgb.h>
+
+#include <stdint.h>
+
+
+static uint64_t decode_big_endian(const uint8_t *data, size_t data_len)
+{
+	uint64_t value = 0;
+
+	while (data_len > 0) {
+		value = (value << 8) + *data;
+		data += 1;
+		data_len -= 1;
+	}
+
+	return value;
+}
+
+static uint8_t *encode_big_endian(uint64_t value, size_t data_len)
+{
+	static uint8_t buf[sizeof(uint64_t)];
+	int idx;
+
+	OSMO_ASSERT(data_len <= ARRAY_SIZE(buf));
+
+	for (idx = data_len - 1; idx >= 0; idx--) {
+		buf[idx] = (uint8_t)value;
+		value = value >> 8;
+	}
+
+	return buf;
+}
+
+static int decode_pdp_info(uint8_t *data, size_t data_len,
+			  struct gprs_gsup_pdp_info *pdp_info)
+{
+	int rc;
+	uint8_t tag;
+	uint8_t *value;
+	size_t value_len;
+
+	/* specific parts */
+	while (data_len > 0) {
+		enum gprs_gsup_iei iei;
+
+		rc = gprs_shift_tlv(&data, &data_len, &tag, &value, &value_len);
+		if (rc < 0)
+			return rc;
+
+		iei = tag;
+
+		switch (iei) {
+		case GPRS_GSUP_PDP_CONTEXT_ID_IE:
+			pdp_info->context_id = decode_big_endian(value, value_len);
+			break;
+
+		case GPRS_GSUP_PDP_TYPE_IE:
+			pdp_info->pdp_type =
+				decode_big_endian(value, value_len) & 0x0fff;
+			break;
+
+		case GPRS_GSUP_ACCESS_POINT_NAME_IE:
+			pdp_info->apn_enc = value;
+			pdp_info->apn_enc_len = value_len;
+			break;
+
+		default:
+			LOGP(DGPRS, LOGL_ERROR,
+			     "GSUP IE type %d not expected in PDP info\n", iei);
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+static int decode_auth_info(uint8_t *data, size_t data_len,
+			   struct gsm_auth_tuple *auth_tuple)
+{
+	int rc;
+	uint8_t tag;
+	uint8_t *value;
+	size_t value_len;
+	enum gprs_gsup_iei iei;
+
+	/* specific parts */
+	while (data_len > 0) {
+		rc = gprs_shift_tlv(&data, &data_len, &tag, &value, &value_len);
+		if (rc < 0)
+			return rc;
+
+		iei = tag;
+
+		switch (iei) {
+		case GPRS_GSUP_RAND_IE:
+			if (value_len != sizeof(auth_tuple->rand))
+				goto parse_error;
+
+			memcpy(auth_tuple->rand, value, value_len);
+			break;
+
+		case GPRS_GSUP_SRES_IE:
+			if (value_len != sizeof(auth_tuple->sres))
+				goto parse_error;
+
+			memcpy(auth_tuple->sres, value, value_len);
+			break;
+
+		case GPRS_GSUP_KC_IE:
+			if (value_len != sizeof(auth_tuple->kc))
+				goto parse_error;
+
+			memcpy(auth_tuple->kc, value, value_len);
+			break;
+
+		default:
+			LOGP(DGPRS, LOGL_ERROR,
+			     "GSUP IE type %d not expected in PDP info\n", iei);
+			continue;
+		}
+	}
+
+	return 0;
+
+parse_error:
+	LOGP(DGPRS, LOGL_ERROR,
+	     "GSUP IE type %d, length %d invalid in PDP info\n", iei, value_len);
+
+	return -1;
+}
+
+int gprs_gsup_decode(const uint8_t *const_data, size_t data_len,
+		     struct gprs_gsup_message *gsup_msg)
+{
+	int rc;
+	uint8_t tag;
+	/* the shift/match functions expect non-const pointers, but we'll
+	 * either copy the data or cast pointers back to const before returning
+	 * them
+	 */
+	uint8_t *data = (uint8_t *)const_data;
+	uint8_t *value;
+	size_t value_len;
+	static const struct gprs_gsup_pdp_info empty_pdp_info = {0};
+	static const struct gsm_auth_tuple empty_auth_info = {0};
+
+	/* generic part */
+	gprs_shift_v_fixed(&data, &data_len, 1, &value);
+	gsup_msg->message_type = decode_big_endian(value, 1);
+
+	rc = gprs_match_tlv(&data, &data_len, GPRS_GSUP_IMSI_IE,
+			    &value, &value_len);
+
+	if (rc <= 0)
+		return -GMM_CAUSE_INV_MAND_INFO;
+
+	if (value_len * 2 + 1 > sizeof(gsup_msg->imsi))
+		return -GMM_CAUSE_INV_MAND_INFO;
+
+	/* Note that gsm48_decode_bcd_number expects the number of encoded IMSI
+	 * octets in the first octet. By coincidence (the TLV encoding) the byte
+	 * before the value part already contains this length so we can use it
+	 * here.
+	 */
+	OSMO_ASSERT(value[-1] == value_len);
+	gsm48_decode_bcd_number(gsup_msg->imsi, sizeof(gsup_msg->imsi),
+				value - 1, 0);
+
+	/* specific parts */
+	while (data_len > 0) {
+		enum gprs_gsup_iei iei;
+		struct gprs_gsup_pdp_info pdp_info;
+		struct gsm_auth_tuple auth_info;
+
+		rc = gprs_shift_tlv(&data, &data_len, &tag, &value, &value_len);
+		if (rc < 0)
+			return -GMM_CAUSE_PROTO_ERR_UNSPEC;
+
+		iei = tag;
+
+		switch (iei) {
+		case GPRS_GSUP_IMSI_IE:
+		case GPRS_GSUP_PDP_TYPE_IE:
+		case GPRS_GSUP_ACCESS_POINT_NAME_IE:
+		case GPRS_GSUP_RAND_IE:
+		case GPRS_GSUP_SRES_IE:
+		case GPRS_GSUP_KC_IE:
+			LOGP(DGPRS, LOGL_NOTICE,
+			     "GSUP IE type %d not expected (ignored)\n", iei);
+			continue;
+
+		case GPRS_GSUP_CAUSE_IE:
+			gsup_msg->cause = decode_big_endian(value, value_len);
+			break;
+
+		case GPRS_GSUP_CANCEL_TYPE_IE:
+			gsup_msg->cancel_type =
+				decode_big_endian(value, value_len) + 1;
+			break;
+
+		case GPRS_GSUP_PDP_INFO_COMPL_IE:
+			gsup_msg->pdp_info_compl = 1;
+			break;
+
+		case GPRS_GSUP_PDP_CONTEXT_ID_IE:
+			/* When these IE appear in the top-level part of the
+			 * message, they are used by Delete Subscr Info to delete
+			 * single entries. We don't have an extra list for
+			 * these but use the PDP info list instead */
+
+			/* fall through */
+
+		case GPRS_GSUP_PDP_INFO_IE:
+			if (gsup_msg->num_pdp_infos >= GPRS_GSUP_MAX_NUM_PDP_INFO) {
+				LOGP(DGPRS, LOGL_ERROR,
+				     "GSUP IE type %d (PDP_INFO) max exceeded\n",
+				     iei);
+				return -GMM_CAUSE_COND_IE_ERR;
+			}
+
+			memcpy(&pdp_info, &empty_pdp_info, sizeof(pdp_info));
+
+			if (iei == GPRS_GSUP_PDP_INFO_IE) {
+				rc = decode_pdp_info(value, value_len, &pdp_info);
+				if (rc < 0)
+					return rc;
+				pdp_info.have_info = 1;
+			} else {
+				pdp_info.context_id =
+					decode_big_endian(value, value_len);
+			}
+
+			gsup_msg->pdp_infos[gsup_msg->num_pdp_infos++] =
+				pdp_info;
+			break;
+
+		case GPRS_GSUP_AUTH_TUPLE_IE:
+			if (gsup_msg->num_auth_tuples >= GPRS_GSUP_MAX_NUM_AUTH_INFO) {
+				LOGP(DGPRS, LOGL_ERROR,
+				     "GSUP IE type %d (AUTH_INFO) max exceeded\n",
+				     iei);
+				return -GMM_CAUSE_INV_MAND_INFO;
+			}
+
+			memcpy(&auth_info, &empty_auth_info, sizeof(auth_info));
+			auth_info.key_seq = gsup_msg->num_auth_tuples;
+
+			rc = decode_auth_info(value, value_len, &auth_info);
+			if (rc < 0)
+				return rc;
+
+			gsup_msg->auth_tuples[gsup_msg->num_auth_tuples++] =
+				auth_info;
+			break;
+		default:
+			LOGP(DGPRS, LOGL_NOTICE,
+			     "GSUP IE type %d unknown\n", iei);
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+static void encode_pdp_info(struct msgb *msg, enum gprs_gsup_iei iei,
+			    const struct gprs_gsup_pdp_info *pdp_info)
+{
+	uint8_t *len_field;
+	size_t old_len;
+	uint8_t u8;
+
+	len_field = msgb_tlv_put(msg, iei, 0, NULL) - 1;
+	old_len = msgb_length(msg);
+
+	u8 = pdp_info->context_id;
+	msgb_tlv_put(msg, GPRS_GSUP_PDP_CONTEXT_ID_IE, sizeof(u8), &u8);
+
+	if (pdp_info->pdp_type) {
+		msgb_tlv_put(msg, GPRS_GSUP_PDP_TYPE_IE,
+			     GPRS_GSUP_PDP_TYPE_SIZE,
+			     encode_big_endian(pdp_info->pdp_type | 0xf000,
+					       GPRS_GSUP_PDP_TYPE_SIZE));
+	}
+
+	if (pdp_info->apn_enc) {
+		msgb_tlv_put(msg, GPRS_GSUP_ACCESS_POINT_NAME_IE,
+			     pdp_info->apn_enc_len, pdp_info->apn_enc);
+	}
+
+	/* Update length field */
+	*len_field = msgb_length(msg) - old_len;
+}
+
+static void encode_auth_info(struct msgb *msg, enum gprs_gsup_iei iei,
+			     const struct gsm_auth_tuple *auth_tuple)
+{
+	uint8_t *len_field;
+	size_t old_len;
+
+	len_field = msgb_tlv_put(msg, iei, 0, NULL) - 1;
+	old_len = msgb_length(msg);
+
+	msgb_tlv_put(msg, GPRS_GSUP_RAND_IE,
+		     sizeof(auth_tuple->rand), auth_tuple->rand);
+
+	msgb_tlv_put(msg, GPRS_GSUP_SRES_IE,
+		     sizeof(auth_tuple->sres), auth_tuple->sres);
+
+	msgb_tlv_put(msg, GPRS_GSUP_KC_IE,
+		     sizeof(auth_tuple->kc), auth_tuple->kc);
+
+	/* Update length field */
+	*len_field = msgb_length(msg) - old_len;
+}
+
+void gprs_gsup_encode(struct msgb *msg, const struct gprs_gsup_message *gsup_msg)
+{
+	uint8_t u8;
+	int idx;
+	uint8_t bcd_buf[GSM48_MI_SIZE] = {0};
+	size_t bcd_len;
+
+	/* generic part */
+	OSMO_ASSERT(gsup_msg->message_type);
+	msgb_v_put(msg, gsup_msg->message_type);
+
+	bcd_len = gsm48_encode_bcd_number(bcd_buf, sizeof(bcd_buf), 0,
+					  gsup_msg->imsi);
+
+	OSMO_ASSERT(bcd_len > 1);
+
+	/* Note that gsm48_encode_bcd_number puts the length into the first
+	 * octet. Since msgb_tlv_put will add this length byte, we'll have to
+	 * skip it */
+	msgb_tlv_put(msg, GPRS_GSUP_IMSI_IE, bcd_len - 1, &bcd_buf[1]);
+
+	/* specific parts */
+	if ((u8 = gsup_msg->cause))
+		msgb_tlv_put(msg, GPRS_GSUP_CAUSE_IE, sizeof(u8), &u8);
+
+	if ((u8 = gsup_msg->cancel_type)) {
+		u8 -= 1;
+		msgb_tlv_put(msg, GPRS_GSUP_CANCEL_TYPE_IE, sizeof(u8), &u8);
+	}
+
+	if (gsup_msg->pdp_info_compl)
+		msgb_tlv_put(msg, GPRS_GSUP_PDP_INFO_COMPL_IE, 0, &u8);
+
+	for (idx = 0; idx < gsup_msg->num_pdp_infos; idx++) {
+		const struct gprs_gsup_pdp_info *pdp_info;
+
+		pdp_info = &gsup_msg->pdp_infos[idx];
+
+		if (pdp_info->context_id == 0)
+			continue;
+
+		if (pdp_info->have_info) {
+			encode_pdp_info(msg, GPRS_GSUP_PDP_INFO_IE, pdp_info);
+		} else {
+			u8 = pdp_info->context_id;
+			msgb_tlv_put(msg, GPRS_GSUP_PDP_CONTEXT_ID_IE,
+				     sizeof(u8), &u8);
+		}
+	}
+
+	for (idx = 0; idx < gsup_msg->num_auth_tuples; idx++) {
+		const struct gsm_auth_tuple *auth_info;
+
+		auth_info = &gsup_msg->auth_tuples[idx];
+
+		if (auth_info->key_seq == GSM_KEY_SEQ_INVAL)
+			continue;
+
+		encode_auth_info(msg, GPRS_GSUP_AUTH_TUPLE_IE, auth_info);
+	}
+}