port rest octets encoding code from osmo-bsc

As part of fixing issue OS#3075, we want to migrate support
for encoding system information from osmo-bsc to libosmocore.

This change ports osmo-bsc code for encoding SI rest octets.

The conversion was a bit tricky in some places because some
functions receive a 'struct gsm_bts' parameter in osmo-bsc.
In this libosmocore version, such functions expect parameters
which correspond to the individual fields of 'struct gsm_bts'
which are used by these functions.

Several structs from osmo-bsc's system_information.h are now
also declared in libosmocore headers, with an added osmo_ prefix
to avoid collisions with existing definitions in osmo-bsc.

Some helpers were ported from osmo-bsc's system_information.c
to libosmocore's gsm48_rest_octets.c. Contrary to osmo-bsc's
implementation they are now only visible within this file.

Unfortunately, this code ported from osmo-bsc lacks unit tests.

Change-Id: I47888965ab11bba1186c21987f1365c9270abeab
Related: OS#3075

2 files changed, 957 insertions, 0 deletions

diff --git a/src/gsm/gsm48_rest_octets.c b/src/gsm/gsm48_rest_octets.c
new file mode 100644
index 00000000..619dc6d1
--- /dev/null
+++ b/src/gsm/gsm48_rest_octets.c
@@ -0,0 +1,949 @@
+/* GSM Mobile Radio Interface Layer 3 messages on the A-bis interface,
+ * rest octet handling according to
+ * 3GPP TS 04.08 version 7.21.0 Release 1998 / ETSI TS 100 940 V7.21.0 */
+
+/* (C) 2009 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 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 <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <stdbool.h>
+
+#include <osmocom/core/bitvec.h>
+#include <osmocom/gsm/bitvec_gsm.h>
+#include <osmocom/gsm/sysinfo.h>
+#include <osmocom/gsm/gsm48_arfcn_range_encode.h>
+#include <osmocom/gsm/gsm48_rest_octets.h>
+
+/* generate SI1 rest octets */
+int osmo_gsm48_rest_octets_si1(uint8_t *data, uint8_t *nch_pos, int is1800_net)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 1;
+
+	if (nch_pos) {
+		bitvec_set_bit(&bv, H);
+		bitvec_set_uint(&bv, *nch_pos, 5);
+	} else
+		bitvec_set_bit(&bv, L);
+
+	if (is1800_net)
+		bitvec_set_bit(&bv, L);
+	else
+		bitvec_set_bit(&bv, H);
+
+	bitvec_spare_padding(&bv, 6);
+	return bv.data_len;
+}
+
+/* Append Repeated E-UTRAN Neighbour Cell to bitvec: see 3GPP TS 44.018 Table 10.5.2.33b.1 */
+static inline bool append_eutran_neib_cell(struct bitvec *bv, const struct osmo_earfcn_si2q *e, size_t *e_offset,
+					   uint8_t budget)
+{
+	unsigned i, skip = 0;
+	int16_t rem = budget - 6; /* account for mandatory stop bit and THRESH_E-UTRAN_high */
+	uint8_t earfcn_budget;
+
+	if (budget <= 6)
+		return false;
+
+	OSMO_ASSERT(budget <= SI2Q_MAX_LEN);
+
+	/* first we have to properly adjust budget requirements */
+	if (e->prio_valid) /* E-UTRAN_PRIORITY: 3GPP TS 45.008*/
+		rem -= 4;
+	else
+		rem--;
+
+	if (e->thresh_lo_valid) /* THRESH_E-UTRAN_low: */
+		rem -= 6;
+	else
+		rem--;
+
+	if (e->qrxlm_valid) /* E-UTRAN_QRXLEVMIN: */
+		rem -= 6;
+	else
+		rem--;
+
+	if (rem < 0)
+		return false;
+
+	/* now we can proceed with actually adding EARFCNs within adjusted budget limit */
+	for (i = 0; i < e->length; i++) {
+		if (e->arfcn[i] != OSMO_EARFCN_INVALID) {
+			if (skip < *e_offset) {
+				skip++; /* ignore EARFCNs added on previous calls */
+			} else {
+				earfcn_budget = 17; /* compute budget per-EARFCN */
+				if (OSMO_EARFCN_MEAS_INVALID == e->meas_bw[i])
+					earfcn_budget++;
+				else
+					earfcn_budget += 4;
+
+				if (rem - earfcn_budget < 0)
+					break;
+				else {
+					(*e_offset)++;
+					rem -= earfcn_budget;
+
+					if (rem < 0)
+						return false;
+
+					bitvec_set_bit(bv, 1); /* EARFCN: */
+					bitvec_set_uint(bv, e->arfcn[i], 16);
+
+					if (OSMO_EARFCN_MEAS_INVALID == e->meas_bw[i])
+						bitvec_set_bit(bv, 0);
+					else { /* Measurement Bandwidth: 9.1.54 */
+						bitvec_set_bit(bv, 1);
+						bitvec_set_uint(bv, e->meas_bw[i], 3);
+					}
+				}
+			}
+		}
+	}
+
+	/* stop bit - end of EARFCN + Measurement Bandwidth sequence */
+	bitvec_set_bit(bv, 0);
+
+	/* Note: we don't support different EARFCN arrays each with different priority, threshold etc. */
+
+	if (e->prio_valid) {
+		/* E-UTRAN_PRIORITY: 3GPP TS 45.008*/
+		bitvec_set_bit(bv, 1);
+		bitvec_set_uint(bv, e->prio, 3);
+	} else
+		bitvec_set_bit(bv, 0);
+
+	/* THRESH_E-UTRAN_high */
+	bitvec_set_uint(bv, e->thresh_hi, 5);
+
+	if (e->thresh_lo_valid) {
+		/* THRESH_E-UTRAN_low: */
+		bitvec_set_bit(bv, 1);
+		bitvec_set_uint(bv, e->thresh_lo, 5);
+	} else
+		bitvec_set_bit(bv, 0);
+
+	if (e->qrxlm_valid) {
+		/* E-UTRAN_QRXLEVMIN: */
+		bitvec_set_bit(bv, 1);
+		bitvec_set_uint(bv, e->qrxlm, 5);
+	} else
+		bitvec_set_bit(bv, 0);
+
+	return true;
+}
+
+static inline void append_earfcn(struct bitvec *bv, const struct osmo_earfcn_si2q *e, size_t *e_offset, uint8_t budget)
+{
+	bool appended;
+	unsigned int old = bv->cur_bit; /* save current position to make rollback possible */
+	int rem = budget - 25;
+	if (rem <= 0)
+		return;
+
+	OSMO_ASSERT(budget <= SI2Q_MAX_LEN);
+
+	/* Additions in Rel-5: */
+	bitvec_set_bit(bv, H);
+	/* No 3G Additional Measurement Param. Descr. */
+	bitvec_set_bit(bv, 0);
+	/* No 3G ADDITIONAL MEASUREMENT Param. Descr. 2 */
+	bitvec_set_bit(bv, 0);
+	/* Additions in Rel-6: */
+	bitvec_set_bit(bv, H);
+	/* 3G_CCN_ACTIVE */
+	bitvec_set_bit(bv, 0);
+	/* Additions in Rel-7: */
+	bitvec_set_bit(bv, H);
+	/* No 700_REPORTING_OFFSET */
+	bitvec_set_bit(bv, 0);
+	/* No 810_REPORTING_OFFSET */
+	bitvec_set_bit(bv, 0);
+	/* Additions in Rel-8: */
+	bitvec_set_bit(bv, H);
+
+	/* Priority and E-UTRAN Parameters Description */
+	bitvec_set_bit(bv, 1);
+
+	/* No Serving Cell Priority Parameters Descr. */
+	bitvec_set_bit(bv, 0);
+	/* No 3G Priority Parameters Description */
+	bitvec_set_bit(bv, 0);
+	/* E-UTRAN Parameters Description */
+	bitvec_set_bit(bv, 1);
+
+	/* E-UTRAN_CCN_ACTIVE */
+	bitvec_set_bit(bv, 0);
+	/* E-UTRAN_Start: 9.1.54 */
+	bitvec_set_bit(bv, 1);
+	/* E-UTRAN_Stop: 9.1.54 */
+	bitvec_set_bit(bv, 1);
+
+	/* No E-UTRAN Measurement Parameters Descr. */
+	bitvec_set_bit(bv, 0);
+	/* No GPRS E-UTRAN Measurement Param. Descr. */
+	bitvec_set_bit(bv, 0);
+
+	/* Note: each of next 3 "repeated" structures might be repeated any
+	   (0, 1, 2...) times - we only support 1 and 0 */
+
+	/* Repeated E-UTRAN Neighbour Cells */
+	bitvec_set_bit(bv, 1);
+
+	appended = append_eutran_neib_cell(bv, e, e_offset, rem);
+	if (!appended) { /* appending is impossible within current budget: rollback */
+		bv->cur_bit = old;
+		return;
+	}
+
+	/* stop bit - end of Repeated E-UTRAN Neighbour Cells sequence: */
+	bitvec_set_bit(bv, 0);
+
+	/* Note: following 2 repeated structs are not supported ATM */
+	/* stop bit - end of Repeated E-UTRAN Not Allowed Cells sequence: */
+	bitvec_set_bit(bv, 0);
+	/* stop bit - end of Repeated E-UTRAN PCID to TA mapping sequence: */
+	bitvec_set_bit(bv, 0);
+
+	/* Priority and E-UTRAN Parameters Description ends here */
+	/* No 3G CSG Description */
+	bitvec_set_bit(bv, 0);
+	/* No E-UTRAN CSG Description */
+	bitvec_set_bit(bv, 0);
+	/* No Additions in Rel-9: */
+	bitvec_set_bit(bv, L);
+}
+
+static int range_encode(enum osmo_gsm48_range r, int *arfcns, int arfcns_used, int *w,
+			int f0, uint8_t *chan_list)
+{
+	/*
+	 * Manipulate the ARFCN list according to the rules in J4 depending
+	 * on the selected range.
+	 */
+	int rc, f0_included;
+
+	osmo_gsm48_range_enc_filter_arfcns(arfcns, arfcns_used, f0, &f0_included);
+
+	rc = osmo_gsm48_range_enc_arfcns(r, arfcns, arfcns_used, w, 0);
+	if (rc < 0)
+		return rc;
+
+	/* Select the range and the amount of bits needed */
+	switch (r) {
+	case OSMO_GSM48_ARFCN_RANGE_128:
+		return osmo_gsm48_range_enc_range128(chan_list, f0, w);
+	case OSMO_GSM48_ARFCN_RANGE_256:
+		return osmo_gsm48_range_enc_range256(chan_list, f0, w);
+	case OSMO_GSM48_ARFCN_RANGE_512:
+		return osmo_gsm48_range_enc_range512(chan_list, f0, w);
+	case OSMO_GSM48_ARFCN_RANGE_1024:
+		return osmo_gsm48_range_enc_range1024(chan_list, f0, f0_included, w);
+	default:
+		return -ERANGE;
+	};
+
+	return f0_included;
+}
+
+static inline int f0_helper(int *sc, size_t length, uint8_t *chan_list)
+{
+	int w[OSMO_GSM48_RANGE_ENC_MAX_ARFCNS] = { 0 };
+
+	return range_encode(OSMO_GSM48_ARFCN_RANGE_1024, sc, length, w, 0, chan_list);
+}
+
+/* Return p(n) for given NR_OF_TDD_CELLS - see Table 9.1.54.1a, 3GPP TS 44.018 */
+static unsigned range1024_p(unsigned n)
+{
+	switch (n) {
+	case 0: return 0;
+	case 1: return 10;
+	case 2: return 19;
+	case 3: return 28;
+	case 4: return 36;
+	case 5: return 44;
+	case 6: return 52;
+	case 7: return 60;
+	case 8: return 67;
+	case 9: return 74;
+	case 10: return 81;
+	case 11: return 88;
+	case 12: return 95;
+	case 13: return 102;
+	case 14: return 109;
+	case 15: return 116;
+	case 16: return 122;
+	default: return 0;
+	}
+}
+
+/* Estimate how many bits it'll take to append single FDD UARFCN */
+static inline int append_utran_fdd_length(uint16_t u, const int *sc, size_t sc_len, size_t length)
+{
+	uint8_t chan_list[16] = { 0 };
+	int tmp[sc_len], f0;
+
+	memcpy(tmp, sc, sizeof(tmp));
+
+	f0 = f0_helper(tmp, length, chan_list);
+	if (f0 < 0)
+		return f0;
+
+	return 21 + range1024_p(length);
+}
+
+/* Append single FDD UARFCN */
+static inline int append_utran_fdd(struct bitvec *bv, uint16_t u, int *sc, size_t length)
+{
+	uint8_t chan_list[16] = { 0 };
+	int f0 = f0_helper(sc, length, chan_list);
+
+	if (f0 < 0)
+		return f0;
+
+	/* Repeated UTRAN FDD Neighbour Cells */
+	bitvec_set_bit(bv, 1);
+
+	/* FDD-ARFCN */
+	bitvec_set_bit(bv, 0);
+	bitvec_set_uint(bv, u, 14);
+
+	/* FDD_Indic0: parameter value '0000000000' is a member of the set? */
+	bitvec_set_bit(bv, f0);
+	/* NR_OF_FDD_CELLS */
+	bitvec_set_uint(bv, length, 5);
+
+	f0 = bv->cur_bit;
+	bitvec_add_range1024(bv, (struct gsm48_range_1024 *)chan_list);
+	bv->cur_bit = f0 + range1024_p(length);
+
+	return 21 + range1024_p(length);
+}
+
+static inline int try_adding_uarfcn(struct bitvec *bv, uint16_t *scramble_list,
+				    size_t uarfcn_length, size_t *u_offset,
+				    uint16_t uarfcn, uint8_t num_sc, uint8_t start_pos, uint8_t budget)
+{
+	int i, k, rc, a[uarfcn_length];
+
+	if (budget < 23)
+		return -ENOMEM;
+
+	/* copy corresponding Scrambling Codes: range encoder make in-place modifications */
+	for (i = start_pos, k = 0; i < num_sc; a[k++] = scramble_list[i++]);
+
+	/* estimate bit length requirements */
+	rc = append_utran_fdd_length(uarfcn, a, uarfcn_length, k);
+	if (rc < 0)
+		return rc; /* range encoder failure */
+
+	if (budget - rc <= 0)
+		return -ENOMEM; /* we have ran out of budget in current SI2q */
+
+	/* compute next offset */
+	*u_offset += k;
+
+	return budget - append_utran_fdd(bv, uarfcn, a, k);
+}
+
+/* Append multiple FDD UARFCNs */
+static inline void append_uarfcns(struct bitvec *bv, const uint16_t *uarfcn_list, size_t *u_offset,
+				  size_t uarfcn_length, uint16_t *scramble_list, uint8_t budget)
+{
+	int i, rem = budget - 7, st = *u_offset; /* account for constant bits right away */
+	uint16_t cu = uarfcn_list[*u_offset]; /* caller ensures that length is positive */
+
+	OSMO_ASSERT(budget <= SI2Q_MAX_LEN);
+
+	if (budget <= 7)
+		return;
+
+	/* 3G Neighbour Cell Description */
+	bitvec_set_bit(bv, 1);
+	/* No Index_Start_3G */
+	bitvec_set_bit(bv, 0);
+	/* No Absolute_Index_Start_EMR */
+	bitvec_set_bit(bv, 0);
+
+	/* UTRAN FDD Description */
+	bitvec_set_bit(bv, 1);
+	/* No Bandwidth_FDD */
+	bitvec_set_bit(bv, 0);
+
+	for (i = *u_offset; i <= uarfcn_length; i++)
+		if (uarfcn_list[i] != cu) { /* we've reached new UARFCN */
+			rem = try_adding_uarfcn(bv, scramble_list, uarfcn_length, u_offset, cu, i, st, rem);
+			if (rem < 0)
+				break;
+
+			if (i < uarfcn_length) {
+				cu = uarfcn_list[i];
+				st = i;
+			} else
+				break;
+		}
+
+	/* stop bit - end of Repeated UTRAN FDD Neighbour Cells */
+	bitvec_set_bit(bv, 0);
+
+	/* UTRAN TDD Description */
+	bitvec_set_bit(bv, 0);
+}
+
+static size_t si2q_earfcn_count(const struct osmo_earfcn_si2q *e)
+{
+	unsigned i, ret = 0;
+
+	if (!e)
+		return 0;
+
+	for (i = 0; i < e->length; i++)
+		if (e->arfcn[i] != OSMO_EARFCN_INVALID)
+			ret++;
+
+	return ret;
+}
+
+/* generate SI2quater rest octets: 3GPP TS 44.018 § 10.5.2.33b */
+int osmo_gsm48_rest_octets_si2quater(uint8_t *data, uint8_t si2q_index, uint8_t si2q_count, const uint16_t *uarfcn_list,
+				     size_t *u_offset, size_t uarfcn_length, uint16_t *scramble_list,
+				     struct osmo_earfcn_si2q *si2quater_neigh_list, size_t *e_offset)
+{
+	int rc;
+	struct bitvec bv;
+
+	if (si2q_count < si2q_index)
+		return -EINVAL;
+
+	bv.data = data;
+	bv.data_len = 20;
+	bitvec_zero(&bv);
+
+	/* BA_IND: Set to '0' as that's what we use for SI2xxx type,
+	 * whereas '1' is used for SI5xxx type messages. The point here
+	 * is to be able to correlate whether a given MS measurement
+	 * report was using the neighbor cells advertised in SI2 or in
+	 * SI5, as those two could very well be different */
+	bitvec_set_bit(&bv, 0);
+	/* 3G_BA_IND */
+	bitvec_set_bit(&bv, 1);
+	/* MP_CHANGE_MARK */
+	bitvec_set_bit(&bv, 0);
+
+	/* SI2quater_INDEX */
+	bitvec_set_uint(&bv, si2q_index, 4);
+	/* SI2quater_COUNT */
+	bitvec_set_uint(&bv, si2q_count, 4);
+
+	/* No Measurement_Parameters Description */
+	bitvec_set_bit(&bv, 0);
+	/* No GPRS_Real Time Difference Description */
+	bitvec_set_bit(&bv, 0);
+	/* No GPRS_BSIC Description */
+	bitvec_set_bit(&bv, 0);
+	/* No GPRS_REPORT PRIORITY Description */
+	bitvec_set_bit(&bv, 0);
+	/* No GPRS_MEASUREMENT_Parameters Description */
+	bitvec_set_bit(&bv, 0);
+	/* No NC Measurement Parameters */
+	bitvec_set_bit(&bv, 0);
+	/* No extension (length) */
+	bitvec_set_bit(&bv, 0);
+
+	rc = SI2Q_MAX_LEN - (bv.cur_bit + 3);
+	if (rc > 0 && uarfcn_length - *u_offset > 0)
+		append_uarfcns(&bv, uarfcn_list, u_offset, uarfcn_length, scramble_list, rc);
+	else /* No 3G Neighbour Cell Description */
+		bitvec_set_bit(&bv, 0);
+
+	/* No 3G Measurement Parameters Description */
+	bitvec_set_bit(&bv, 0);
+	/* No GPRS_3G_MEASUREMENT Parameters Descr. */
+	bitvec_set_bit(&bv, 0);
+
+	rc = SI2Q_MAX_LEN - bv.cur_bit;
+	if (rc > 0 && si2q_earfcn_count(si2quater_neigh_list) - *e_offset > 0)
+		append_earfcn(&bv, si2quater_neigh_list, e_offset, rc);
+	else /* No Additions in Rel-5: */
+		bitvec_set_bit(&bv, L);
+
+	bitvec_spare_padding(&bv, (bv.data_len * 8) - 1);
+	return bv.data_len;
+}
+
+/* Append selection parameters to bitvec */
+static void append_selection_params(struct bitvec *bv,
+				    const struct osmo_gsm48_si_selection_params *sp)
+{
+	if (sp->present) {
+		bitvec_set_bit(bv, H);
+		bitvec_set_bit(bv, sp->cbq);
+		bitvec_set_uint(bv, sp->cell_resel_off, 6);
+		bitvec_set_uint(bv, sp->temp_offs, 3);
+		bitvec_set_uint(bv, sp->penalty_time, 5);
+	} else
+		bitvec_set_bit(bv, L);
+}
+
+/* Append power offset to bitvec */
+static void append_power_offset(struct bitvec *bv,
+				const struct osmo_gsm48_si_power_offset *po)
+{
+	if (po->present) {
+		bitvec_set_bit(bv, H);
+		bitvec_set_uint(bv, po->power_offset, 2);
+	} else
+		bitvec_set_bit(bv, L);
+}
+
+/* Append GPRS indicator to bitvec */
+static void append_gprs_ind(struct bitvec *bv,
+			    const struct osmo_gsm48_si3_gprs_ind *gi)
+{
+	if (gi->present) {
+		bitvec_set_bit(bv, H);
+		bitvec_set_uint(bv, gi->ra_colour, 3);
+		/* 0 == SI13 in BCCH Norm, 1 == SI13 sent on BCCH Ext */
+		bitvec_set_bit(bv, gi->si13_position);
+	} else
+		bitvec_set_bit(bv, L);
+}
+
+/* Generate SI2ter Rest Octests 3GPP TS 44.018 Table 10.5.2.33a.1 */
+int osmo_gsm48_rest_octets_si2ter(uint8_t *data)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 4;
+
+	/* No SI2ter_MP_CHANGE_MARK */
+	bitvec_set_bit(&bv, L);
+
+	bitvec_spare_padding(&bv, (bv.data_len * 8) - 1);
+
+	return bv.data_len;
+}
+
+/* Generate SI2bis Rest Octests 3GPP TS 44.018 Table 10.5.2.33.1 */
+int osmo_gsm48_rest_octets_si2bis(uint8_t *data)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 1;
+
+	bitvec_spare_padding(&bv, (bv.data_len * 8) - 1);
+
+	return bv.data_len;
+}
+
+/* Generate SI3 Rest Octests (Chapter 10.5.2.34 / Table 10.4.72) */
+int osmo_gsm48_rest_octets_si3(uint8_t *data, const struct osmo_gsm48_si_ro_info *si3)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 4;
+
+	/* Optional Selection Parameters */
+	append_selection_params(&bv, &si3->selection_params);
+
+	/* Optional Power Offset */
+	append_power_offset(&bv, &si3->power_offset);
+
+	/* Do we have a SI2ter on the BCCH? */
+	if (si3->si2ter_indicator)
+		bitvec_set_bit(&bv, H);
+	else
+		bitvec_set_bit(&bv, L);
+
+	/* Early Classmark Sending Control */
+	if (si3->early_cm_ctrl)
+		bitvec_set_bit(&bv, H);
+	else
+		bitvec_set_bit(&bv, L);
+
+	/* Do we have a SI Type 9 on the BCCH? */
+	if (si3->scheduling.present) {
+		bitvec_set_bit(&bv, H);
+		bitvec_set_uint(&bv, si3->scheduling.where, 3);
+	} else
+		bitvec_set_bit(&bv, L);
+
+	/* GPRS Indicator */
+	append_gprs_ind(&bv, &si3->gprs_ind);
+
+	/* 3G Early Classmark Sending Restriction. If H, then controlled by
+	 * early_cm_ctrl above */
+	if (si3->early_cm_restrict_3g)
+		bitvec_set_bit(&bv, L);
+	else
+		bitvec_set_bit(&bv, H);
+
+	if (si3->si2quater_indicator) {
+		bitvec_set_bit(&bv, H); /* indicator struct present */
+		bitvec_set_uint(&bv, 0, 1); /* message is sent on BCCH Norm */
+	}
+
+	bitvec_spare_padding(&bv, (bv.data_len*8)-1);
+	return bv.data_len;
+}
+
+static int append_lsa_params(struct bitvec *bv,
+			     const struct osmo_gsm48_lsa_params *lsa_params)
+{
+	/* FIXME */
+	return -1;
+}
+
+/* Generate SI4 Rest Octets (Chapter 10.5.2.35) */
+int osmo_gsm48_rest_octets_si4(uint8_t *data, const struct osmo_gsm48_si_ro_info *si4, int len)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = len;
+
+	/* SI4 Rest Octets O */
+	append_selection_params(&bv, &si4->selection_params);
+	append_power_offset(&bv, &si4->power_offset);
+	append_gprs_ind(&bv, &si4->gprs_ind);
+
+	if (0 /* FIXME */) {
+		/* H and SI4 Rest Octets S */
+		bitvec_set_bit(&bv, H);
+
+		/* LSA Parameters */
+		if (si4->lsa_params.present) {
+			bitvec_set_bit(&bv, H);
+			append_lsa_params(&bv, &si4->lsa_params);
+		} else
+			bitvec_set_bit(&bv, L);
+
+		/* Cell Identity */
+		if (1) {
+			bitvec_set_bit(&bv, H);
+			bitvec_set_uint(&bv, si4->cell_id, 16);
+		} else
+			bitvec_set_bit(&bv, L);
+
+		/* LSA ID Information */
+		if (0) {
+			bitvec_set_bit(&bv, H);
+			/* FIXME */
+		} else
+			bitvec_set_bit(&bv, L);
+	} else {
+		/* L and break indicator */
+		bitvec_set_bit(&bv, L);
+		bitvec_set_bit(&bv, si4->break_ind ? H : L);
+	}
+
+	return bv.data_len;
+}
+
+
+/* GSM 04.18 ETSI TS 101 503 V8.27.0 (2006-05)
+
+<SI6 rest octets> ::=
+{L | H <PCH and NCH info>}
+{L | H <VBS/VGCS options : bit(2)>}
+{ < DTM_support : bit == L > I < DTM_support : bit == H >
+< RAC : bit (8) >
+< MAX_LAPDm : bit (3) > }
+< Band indicator >
+{ L | H < GPRS_MS_TXPWR_MAX_CCH : bit (5) > }
+<implicit spare >;
+*/
+int osmo_gsm48_rest_octets_si6(uint8_t *data, bool is1800_net)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 1;
+
+	/* no PCH/NCH info */
+	bitvec_set_bit(&bv, L);
+	/* no VBS/VGCS options */
+	bitvec_set_bit(&bv, L);
+	/* no DTM_support */
+	bitvec_set_bit(&bv, L);
+	/* band indicator */
+	if (is1800_net)
+		bitvec_set_bit(&bv, L);
+	else
+		bitvec_set_bit(&bv, H);
+	/* no GPRS_MS_TXPWR_MAX_CCH */
+	bitvec_set_bit(&bv, L);
+
+	bitvec_spare_padding(&bv, (bv.data_len * 8) - 1);
+	return bv.data_len;
+}
+
+/* GPRS Mobile Allocation as per TS 04.60 Chapter 12.10a:
+   < GPRS Mobile Allocation IE > ::=
+     < HSN : bit (6) >
+     { 0 | 1 < RFL number list : < RFL number list struct > > }
+     { 0 < MA_LENGTH : bit (6) >
+         < MA_BITMAP: bit (val(MA_LENGTH) + 1) >
+     | 1 { 0 | 1 <ARFCN index list : < ARFCN index list struct > > } } ;
+
+     < RFL number list struct > :: =
+       < RFL_NUMBER : bit (4) >
+       { 0 | 1 < RFL number list struct > } ;
+     < ARFCN index list struct > ::=
+       < ARFCN_INDEX : bit(6) >
+       { 0 | 1 < ARFCN index list struct > } ;
+ */
+static int append_gprs_mobile_alloc(struct bitvec *bv)
+{
+	/* Hopping Sequence Number */
+	bitvec_set_uint(bv, 0, 6);
+
+	if (0) {
+		/* We want to use a RFL number list */
+		bitvec_set_bit(bv, 1);
+		/* FIXME: RFL number list */
+	} else
+		bitvec_set_bit(bv, 0);
+
+	if (0) {
+		/* We want to use a MA_BITMAP */
+		bitvec_set_bit(bv, 0);
+		/* FIXME: MA_LENGTH, MA_BITMAP, ... */
+	} else {
+		bitvec_set_bit(bv, 1);
+		if (0) {
+			/* We want to provide an ARFCN index list */
+			bitvec_set_bit(bv, 1);
+			/* FIXME */
+		} else
+			bitvec_set_bit(bv, 0);
+	}
+	return 0;
+}
+
+static int encode_t3192(unsigned int t3192)
+{
+	/* See also 3GPP TS 44.060
+	   Table 12.24.2: GPRS Cell Options information element details */
+	if (t3192 == 0)
+		return 3;
+	else if (t3192 <= 80)
+		return 4;
+	else if (t3192 <= 120)
+		return 5;
+	else if (t3192 <= 160)
+		return 6;
+	else if (t3192 <= 200)
+		return 7;
+	else if (t3192 <= 500)
+		return 0;
+	else if (t3192 <= 1000)
+		return 1;
+	else if (t3192 <= 1500)
+		return 2;
+	else
+		return -EINVAL;
+}
+
+static int encode_drx_timer(unsigned int drx)
+{
+	if (drx == 0)
+		return 0;
+	else if (drx == 1)
+		return 1;
+	else if (drx == 2)
+		return 2;
+	else if (drx <= 4)
+		return 3;
+	else if (drx <= 8)
+		return 4;
+	else if (drx <= 16)
+		return 5;
+	else if (drx <= 32)
+		return 6;
+	else if (drx <= 64)
+		return 7;
+	else
+		return -EINVAL;
+}
+
+/* GPRS Cell Options as per TS 04.60 Chapter 12.24
+	< GPRS Cell Options IE > ::=
+		< NMO : bit(2) >
+		< T3168 : bit(3) >
+		< T3192 : bit(3) >
+		< DRX_TIMER_MAX: bit(3) >
+		< ACCESS_BURST_TYPE: bit >
+		< CONTROL_ACK_TYPE : bit >
+		< BS_CV_MAX: bit(4) >
+		{ 0 | 1 < PAN_DEC : bit(3) >
+			< PAN_INC : bit(3) >
+			< PAN_MAX : bit(3) >
+		{ 0 | 1 < Extension Length : bit(6) >
+			< bit (val(Extension Length) + 1
+			& { < Extension Information > ! { bit ** = <no string> } } ;
+	< Extension Information > ::=
+		{ 0 | 1 < EGPRS_PACKET_CHANNEL_REQUEST : bit >
+			< BEP_PERIOD : bit(4) > }
+		< PFC_FEATURE_MODE : bit >
+		< DTM_SUPPORT : bit >
+		<BSS_PAGING_COORDINATION: bit >
+		<spare bit > ** ;
+ */
+static int append_gprs_cell_opt(struct bitvec *bv,
+				const struct osmo_gprs_cell_options *gco)
+{
+	int t3192, drx_timer_max;
+
+	t3192 = encode_t3192(gco->t3192);
+	if (t3192 < 0)
+		return t3192;
+
+	drx_timer_max = encode_drx_timer(gco->drx_timer_max);
+	if (drx_timer_max < 0)
+		return drx_timer_max;
+
+	bitvec_set_uint(bv, gco->nmo, 2);
+
+	/* See also 3GPP TS 44.060
+	   Table 12.24.2: GPRS Cell Options information element details */
+	bitvec_set_uint(bv, gco->t3168 / 500 - 1, 3);
+
+	bitvec_set_uint(bv, t3192, 3);
+	bitvec_set_uint(bv, drx_timer_max, 3);
+	/* ACCESS_BURST_TYPE: Hard-code 8bit */
+	bitvec_set_bit(bv, 0);
+	/* CONTROL_ACK_TYPE: */
+	bitvec_set_bit(bv, gco->ctrl_ack_type_use_block);
+	bitvec_set_uint(bv, gco->bs_cv_max, 4);
+
+	if (0) {
+		/* hard-code no PAN_{DEC,INC,MAX} */
+		bitvec_set_bit(bv, 0);
+	} else {
+		/* copied from ip.access BSC protocol trace */
+		bitvec_set_bit(bv, 1);
+		bitvec_set_uint(bv, 1, 3);	/* DEC */
+		bitvec_set_uint(bv, 1, 3);	/* INC */
+		bitvec_set_uint(bv, 15, 3);	/* MAX */
+	}
+
+	if (!gco->ext_info_present) {
+		/* no extension information */
+		bitvec_set_bit(bv, 0);
+	} else {
+		/* extension information */
+		bitvec_set_bit(bv, 1);
+		if (!gco->ext_info.egprs_supported) {
+			/* 6bit length of extension */
+			bitvec_set_uint(bv, (1 + 3)-1, 6);
+			/* EGPRS supported in the cell */
+			bitvec_set_bit(bv, 0);
+		} else {
+			/* 6bit length of extension */
+			bitvec_set_uint(bv, (1 + 5 + 3)-1, 6);
+			/* EGPRS supported in the cell */
+			bitvec_set_bit(bv, 1);
+
+			/* 1bit EGPRS PACKET CHANNEL REQUEST */
+			if (gco->supports_egprs_11bit_rach == 0) {
+				bitvec_set_bit(bv,
+					gco->ext_info.use_egprs_p_ch_req);
+			} else {
+				bitvec_set_bit(bv, 0);
+			}
+
+			/* 4bit BEP PERIOD */
+			bitvec_set_uint(bv, gco->ext_info.bep_period, 4);
+		}
+		bitvec_set_bit(bv, gco->ext_info.pfc_supported);
+		bitvec_set_bit(bv, gco->ext_info.dtm_supported);
+		bitvec_set_bit(bv, gco->ext_info.bss_paging_coordination);
+	}
+
+	return 0;
+}
+
+static void append_gprs_pwr_ctrl_pars(struct bitvec *bv,
+				      const struct osmo_gprs_power_ctrl_pars *pcp)
+{
+	bitvec_set_uint(bv, pcp->alpha, 4);
+	bitvec_set_uint(bv, pcp->t_avg_w, 5);
+	bitvec_set_uint(bv, pcp->t_avg_t, 5);
+	bitvec_set_uint(bv, pcp->pc_meas_chan, 1);
+	bitvec_set_uint(bv, pcp->n_avg_i, 4);
+}
+
+/* Generate SI13 Rest Octests (04.08 Chapter 10.5.2.37b) */
+int osmo_gsm48_rest_octets_si13(uint8_t *data, const struct osmo_gsm48_si13_info *si13)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 20;
+
+	if (0) {
+		/* No rest octets */
+		bitvec_set_bit(&bv, L);
+	} else {
+		bitvec_set_bit(&bv, H);
+		bitvec_set_uint(&bv, si13->bcch_change_mark, 3);
+		bitvec_set_uint(&bv, si13->si_change_field, 4);
+		if (1) {
+			bitvec_set_bit(&bv, 0);
+		} else {
+			bitvec_set_bit(&bv, 1);
+			bitvec_set_uint(&bv, si13->bcch_change_mark, 2);
+			append_gprs_mobile_alloc(&bv);
+		}
+		/* PBCCH not present in cell:
+		   it shall never be indicated according to 3GPP TS 44.018 Table 10.5.2.37b.1 */
+		bitvec_set_bit(&bv, 0);
+		bitvec_set_uint(&bv, si13->rac, 8);
+		bitvec_set_bit(&bv, si13->spgc_ccch_sup);
+		bitvec_set_uint(&bv, si13->prio_acc_thr, 3);
+		bitvec_set_uint(&bv, si13->net_ctrl_ord, 2);
+		append_gprs_cell_opt(&bv, &si13->cell_opts);
+		append_gprs_pwr_ctrl_pars(&bv, &si13->pwr_ctrl_pars);
+
+		/* 3GPP TS 44.018 Release 6 / 10.5.2.37b */
+		bitvec_set_bit(&bv, H);	/* added Release 99 */
+		/* claim our SGSN is compatible with Release 99, as EDGE and EGPRS
+		 * was only added in this Release */
+		bitvec_set_bit(&bv, 1);
+	}
+	bitvec_spare_padding(&bv, (bv.data_len*8)-1);
+	return bv.data_len;
+}
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 922ac01f..a9037870 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -273,6 +273,14 @@ gsm414_msgt_names;
 gsm48_push_l3hdr;
 gsm48_att_tlvdef;
 gsm48_cc_msg_name;
+gsm48_rest_octets_si1;
+gsm48_rest_octets_si2quater;
+gsm48_rest_octets_si2ter;
+gsm48_rest_octets_si2bis;
+gsm48_rest_octets_si6;
+gsm48_rest_octets_si3;
+gsm48_rest_octets_si4;
+gsm48_rest_octets_si13;
 gsm48_rr_msg_name;
 gsm48_cc_state_name;
 gsm48_construct_ra;